User Panel
User Panel
User Panel
|
Posted: 3/2/2014 4:17:36 AM EDT
[#1]
Quoted:
? because it seems like this is the issue with my new 7.5 build. Fails to extract/eject and tries to jam another round in without the first round fully exiting the cylinder. Symptoms/Troubleshooting 1 - seems to be cycling fully... if I put one round in a magpul mag and fire, the bolt locks back EVERY time. 2 - spent casing remained maybe 50% of the way out of the chamber, bolt locked back. 3 - brass or steel 4 - brand new sota arms standard magphos mil-spec bcg, 5 - extractor (clip?) felt weak, removed spring, stretched, re-installed, tested, seem to have helped slightly... will extract single rounds but still fails to extract first spent casing if another is in the mag, had a FEW successful cycles but never more than 2. Does this sound like I need the BCM extractor upgrade kit? if so, why is this an issue more on SBR uppers? if not.. any other ideas? Thanks for your time! and a pic for clicking!! http://i62.tinypic.com/349a1x5.jpg Stretching the spring as you know isn't the way to go and now it does need to be replaced and the BCM is a good one. Did you happen to clean the bore really well with a bore brush and if not I would. After new extractor spring is installed I would lube it up and hand cycle the thing a few hundred times. Also no mention of which buffer you are using and it sounds like you are a candidate for a heavier one. Also never mix shooting brass and steel ammo at the same time, yes you could out with brass and finish with steel but not the other way around and don't go back and forth. Personally I start with good brass for the first couple of hundred rounds to help with break in and leave the steel for a later date for your plinking desires. Due to the higher pressures of the short pistol system your brass is still partially locked up in the chamber when the extractor is trying to rank it out. The new BCM kit and possibly a heavier buffer is likely your fix. You may also want to inspect your chamber to see if it looks smooth or if by chance there is some machining chatter marks left behind when it was being finished. |
|
|
|
Posted: 3/2/2014 5:25:16 AM EDT
[#2]
I also agree that your issue should be resolved with a heavier buffer since spent shell did not get a chance to eject completely before the next round is being pushed, timing is out as it sounds.
|
|
|
|
Posted: 3/2/2014 8:17:01 AM EDT
[#3]
Quote HistoryQuoted:
Stretching the spring as you know isn't the way to go and now it does need to be replaced and the BCM is a good one. Did you happen to clean the bore really well with a bore brush and if not I would. After new extractor spring is installed I would lube it up and hand cycle the thing a few hundred times. Also no mention of which buffer you are using and it sounds like you are a candidate for a heavier one. Also never mix shooting brass and steel ammo at the same time, yes you could out with brass and finish with steel but not the other way around and don't go back and forth. Personally I start with good brass for the first couple of hundred rounds to help with break in and leave the steel for a later date for your plinking desires. Due to the higher pressures of the short pistol system your brass is still partially locked up in the chamber when the extractor is trying to rank it out. The new BCM kit and possibly a heavier buffer is likely your fix. You may also want to inspect your chamber to see if it looks smooth or if by chance there is some machining chatter marks left behind when it was being finished. Quote HistoryQuoted:
Quoted:
? because it seems like this is the issue with my new 7.5 build. Fails to extract/eject and tries to jam another round in without the first round fully exiting the cylinder. Symptoms/Troubleshooting 1 - seems to be cycling fully... if I put one round in a magpul mag and fire, the bolt locks back EVERY time. 2 - spent casing remained maybe 50% of the way out of the chamber, bolt locked back. 3 - brass or steel 4 - brand new sota arms standard magphos mil-spec bcg, 5 - extractor (clip?) felt weak, removed spring, stretched, re-installed, tested, seem to have helped slightly... will extract single rounds but still fails to extract first spent casing if another is in the mag, had a FEW successful cycles but never more than 2. Does this sound like I need the BCM extractor upgrade kit? if so, why is this an issue more on SBR uppers? if not.. any other ideas? Thanks for your time! and a pic for clicking!! http://i62.tinypic.com/349a1x5.jpg Stretching the spring as you know isn't the way to go and now it does need to be replaced and the BCM is a good one. Did you happen to clean the bore really well with a bore brush and if not I would. After new extractor spring is installed I would lube it up and hand cycle the thing a few hundred times. Also no mention of which buffer you are using and it sounds like you are a candidate for a heavier one. Also never mix shooting brass and steel ammo at the same time, yes you could out with brass and finish with steel but not the other way around and don't go back and forth. Personally I start with good brass for the first couple of hundred rounds to help with break in and leave the steel for a later date for your plinking desires. Due to the higher pressures of the short pistol system your brass is still partially locked up in the chamber when the extractor is trying to rank it out. The new BCM kit and possibly a heavier buffer is likely your fix. You may also want to inspect your chamber to see if it looks smooth or if by chance there is some machining chatter marks left behind when it was being finished. BCM extractor upgrade ordered. I think i get it... because its a shorter barrel the gas block is closer resulting in bolt trying to extract the shell SOONER while the chamber pressures are still high creating more friction while trying to eject.. No haven't cleaned chamber, I'll do that. and yes i know stretching isn't the best but i figured it would be a good quick cheap test. Only had a few hours to test for before I won't have a chance for over a week to do any more testing. I figured I would be able to find a replacement by then. We actually have a large assortment of springs and o-rings at work.. Very well might have what I need there right now... No details on current buffer tube. All I know its a pistol buffer and came with the aero lower. When I fired one at a time sometimes the case was fully removed from the chamber but just laying around in the upper. any recommendations on a buffer if the extractor upgrade doesn't work? H2? is that a stiffer spring? or just heavier weight? thanks |
|
|
|
Posted: 3/2/2014 10:25:47 AM EDT
[#4]
Quote HistoryQuoted:
BCM extractor upgrade ordered. I think i get it... because its a shorter barrel the gas block is closer resulting in bolt trying to extract the shell SOONER while the chamber pressures are still high creating more friction while trying to eject.. No haven't cleaned chamber, I'll do that. and yes i know stretching isn't the best but i figured it would be a good quick cheap test. Only had a few hours to test for before I won't have a chance for over a week to do any more testing. I figured I would be able to find a replacement by then. We actually have a large assortment of springs and o-rings at work.. Very well might have what I need there right now... No details on current buffer tube. All I know its a pistol buffer and came with the aero lower. When I fired one at a time sometimes the case was fully removed from the chamber but just laying around in the upper. any recommendations on a buffer if the extractor upgrade doesn't work? H2? is that a stiffer spring? or just heavier weight? thanks Quote HistoryQuoted:
Quoted:
Quoted:
? because it seems like this is the issue with my new 7.5 build. Fails to extract/eject and tries to jam another round in without the first round fully exiting the cylinder. Symptoms/Troubleshooting 1 - seems to be cycling fully... if I put one round in a magpul mag and fire, the bolt locks back EVERY time. 2 - spent casing remained maybe 50% of the way out of the chamber, bolt locked back. 3 - brass or steel 4 - brand new sota arms standard magphos mil-spec bcg, 5 - extractor (clip?) felt weak, removed spring, stretched, re-installed, tested, seem to have helped slightly... will extract single rounds but still fails to extract first spent casing if another is in the mag, had a FEW successful cycles but never more than 2. Does this sound like I need the BCM extractor upgrade kit? if so, why is this an issue more on SBR uppers? if not.. any other ideas? Thanks for your time! and a pic for clicking!! http://i62.tinypic.com/349a1x5.jpg Stretching the spring as you know isn't the way to go and now it does need to be replaced and the BCM is a good one. Did you happen to clean the bore really well with a bore brush and if not I would. After new extractor spring is installed I would lube it up and hand cycle the thing a few hundred times. Also no mention of which buffer you are using and it sounds like you are a candidate for a heavier one. Also never mix shooting brass and steel ammo at the same time, yes you could out with brass and finish with steel but not the other way around and don't go back and forth. Personally I start with good brass for the first couple of hundred rounds to help with break in and leave the steel for a later date for your plinking desires. Due to the higher pressures of the short pistol system your brass is still partially locked up in the chamber when the extractor is trying to rank it out. The new BCM kit and possibly a heavier buffer is likely your fix. You may also want to inspect your chamber to see if it looks smooth or if by chance there is some machining chatter marks left behind when it was being finished. BCM extractor upgrade ordered. I think i get it... because its a shorter barrel the gas block is closer resulting in bolt trying to extract the shell SOONER while the chamber pressures are still high creating more friction while trying to eject.. No haven't cleaned chamber, I'll do that. and yes i know stretching isn't the best but i figured it would be a good quick cheap test. Only had a few hours to test for before I won't have a chance for over a week to do any more testing. I figured I would be able to find a replacement by then. We actually have a large assortment of springs and o-rings at work.. Very well might have what I need there right now... No details on current buffer tube. All I know its a pistol buffer and came with the aero lower. When I fired one at a time sometimes the case was fully removed from the chamber but just laying around in the upper. any recommendations on a buffer if the extractor upgrade doesn't work? H2? is that a stiffer spring? or just heavier weight? thanks |
|
|
|
Posted: 3/2/2014 10:31:04 AM EDT
[#5]
for anyone having this problem please consider this..
a brand name fancy extractor upgrade is not required visit your local hardware store such as fastanal etc and purchase a bag of number 007 o rings.. they are usually sold in 100 bags for just a couple buck per bag install one o-ring around the extractor spring and reassemble and your problems will be solved no heavy buffers or high cost involved. they other 99 o-rings put in all your other bolts, zombie bag, give to your shooting partners... this will fix all the problems with short barrels and will cost you very little installing o-rings in all your bolts even in long guns will increase reliability and smooth out ejection and extraction problems, you will find after this easy fix that your brass ejection angle will become very consistent and your gun will drop the brass in a small circle |
|
|
|
Posted: 3/2/2014 10:52:56 AM EDT
[#6]
Supermario, you also may want to check the ejector to make sure it is not binding. If you already have a standard carbine buffer I'd suggest buying a H3 buffer, that way you can make an H or H2 from the parts of the std and H3 internal components. If cash isn't an option, buy whichever and test drive.
And goatboy, yes a #60 o-ring from your local hardware store helps many times, but that can be only a partial fix and isn't necessary a 100% guarantee that will "fix all of the problems". Adding a heavier buffer will actually slow the system down a tad allowing it shell casing time to release from the chamber walls, and since Supermario already stretched his extractor spring he may as well spend the few bucks on a known exceptional replacement. |
|
|
|
Posted: 3/2/2014 12:50:02 PM EDT
[#7]
i say open the gas port
|
|
|
|
Posted: 3/2/2014 1:08:20 PM EDT
[#8]
OP, installing an "upgraded" extractor kit which uses a crane o-ring is taking the wrong approach, you need to correct the actual problem. Your BCG is cycling too fast, it needs to be slowed down enough to allow pressures to drop and the spent cases to cool and contract. To put this into a more simplified explanation, by installing the upgrade kit, you are only trying to force the bolt to yank the spent case out before it is ready to be extracted. It's like you choosing a nail remover to pull screws out of wood instead of using a screwdriver......sure, they might still come out, but it was probably not the best way to remove them.
|
|
|
|
Posted: 3/2/2014 1:25:05 PM EDT
[#9]
Quote HistoryQuoted:
i say open the gas port Me thinks this is bad advice. |
|
|
|
Posted: 3/2/2014 5:39:10 PM EDT
[#10]
Agree don't open the gas port first. That could make it worse.
|
|
|
|
Posted: 3/2/2014 6:08:24 PM EDT
[#11]
On my pistol, I was having problems extracting Steel Case ammo (no problem with Brass). The failure to extract was causing the next round to slam into the spent cartridge still sitting in the chamber and thus the spent case would get wedged into the chamber. It's a good thing I had a barrel cleaning rod with me that I used to poke the stuck cartridge out with. I called the vendor of my BCG (Aim), and told them about the extraction problems. My BCG does have an extractor O-ring pre-installed. They told me to take the O-ring that surrounds the extractor spring out, and this should solve the problem. I did take the Extractor Spring out (took only a couple min) and then tested extraction with manually cycling through a couple of magazines loaded with Steel case. I didn't get a single failure to extract. Very different, as with the O-ring ON, I would get failures to extract even with Manual Cycling. The weather has been very bad where I live, so I have not tried it at the range yet. Just passing on to you what I was told, and what I've experienced so far. As a back up, I also purchased a Wolff extractor spring upgrade from eBay for $5 including shipping. The Wolff spring looks stronger than the stock one on my BCG.I will install it and experiment with it, after I've experimented with the Stock SPring/No O-ring set up. Either way, if the Wolff spring works well, I may just end up using it and put the extractor O-ring back in with it. Although I'm obviously no expert, there must be a good reason for the O-ring to be there. |
|
|
|
Posted: 3/2/2014 6:21:07 PM EDT
[#12]
not true, more gas = full cycle , thats why DD opens theirs up
runs flawless |
|
|
|
Posted: 3/2/2014 6:50:36 PM EDT
[#13]
not saying your wrong I just wouldn't start with something so drastic at first and not to mention something needing done by someone with the right tools and knowledge.
|
|
|
|
Posted: 3/3/2014 12:12:51 AM EDT
[#14]
Quoted:
for anyone having this problem please consider this.. a brand name fancy extractor upgrade is not required visit your local hardware store such as fastanal etc and purchase a bag of number 007 o rings.. they are usually sold in 100 bags for just a couple buck per bag install one o-ring around the extractor spring and reassemble and your problems will be solved no heavy buffers or high cost involved. they other 99 o-rings put in all your other bolts, zombie bag, give to your shooting partners... this will fix all the problems with short barrels and will cost you very little installing o-rings in all your bolts even in long guns will increase reliability and smooth out ejection and extraction problems, you will find after this easy fix that your brass ejection angle will become very consistent and your gun will drop the brass in a small circle Yes, I'm aware there's nothing magical about the kits. Just a stiffer spring and an O-ring to limit unlocking motion. Like I said I'm 99% sure we have all the stuff needed sitting at my work right now. Quoted:
Supermario, you also may want to check the ejector to make sure it is not binding. If you already have a standard carbine buffer I'd suggest buying a H3 buffer, that way you can make an H or H2 from the parts of the std and H3 internal components. If cash isn't an option, buy whichever and test drive. And goatboy, yes a #60 o-ring from your local hardware store helps many times, but that can be only a partial fix and isn't necessary a 100% guarantee that will "fix all of the problems". Adding a heavier buffer will actually slow the system down a tad allowing it shell casing time to release from the chamber walls, and since Supermario already stretched his extractor spring he may as well spend the few bucks on a known exceptional replacement. I forgot to mention this yes... the extractor "clip" I guess... moves freely and seems weak while the actual spring punch extractor pin thing itself is actually quite stiff and almost felt bound. Which are you asking about? I see thanks, and I currently have a pistol buffer....(?not the same?) and yes the springs/orings are cheap, I'd rather have some in the mail just as a backup in case i can't find the parts locally. Quoted:
not saying your wrong I just wouldn't start with something so drastic at first and not to mention something needing done by someone with the right tools and knowledge. Yes I don't think is a gas port issue, that's what I thought at first but but since the bolt locks back EVERY time, it sounds like its getting enough pressure to me. Not to mention the PITA of trying to remove the handguard... don't even know how... Quoted:
OP, installing an "upgraded" extractor kit which uses a crane o-ring is taking the wrong approach, you need to correct the actual problem. Your BCG is cycling too fast, it needs to be slowed down enough to allow pressures to drop and the spent cases to cool and contract. To put this into a more simplified explanation, by installing the upgrade kit, you are only trying to force the bolt to yank the spent case out before it is ready to be extracted. It's like you choosing a nail remover to pull screws out of wood instead of using a screwdriver......sure, they might still come out, but it was probably not the best way to remove them. haha thanks for the breakdown but don't worry, I fully understand the concepts so far and yes I agree that this might be a possible issue so I will be looking into a heavier weight buffer. So far no damaged edges from the extractor otherwise that would be a CLEAR sign... (might happen after I get this new spring and o-ring though...) Quoted:
On my pistol, I was having problems extracting Steel Case ammo (no problem with Brass). The failure to extract was causing the next round to slam into the spent cartridge still sitting in the chamber and thus the spent case would get wedged into the chamber. It's a good thing I had a barrel cleaning rod with me that I used to poke the stuck cartridge out with. I called the vendor of my BCG (Aim), and told them about the extraction problems. My BCG does have an extractor O-ring pre-installed. They told me to take the O-ring that surrounds the extractor spring out, and this should solve the problem. I did take the Extractor Spring out (took only a couple min) and then tested extraction with manually cycling through a couple of magazines loaded with Steel case. I didn't get a single failure to extract. Very different, as with the O-ring ON, I would get failures to extract even with Manual Cycling. The weather has been very bad where I live, so I have not tried it at the range yet. Just passing on to you what I was told, and what I've experienced so far. As a back up, I also purchased a Wolff extractor spring upgrade from eBay for $5 including shipping. The Wolff spring looks stronger than the stock one on my BCG.I will install it and experiment with it, after I've experimented with the Stock SPring/No O-ring set up. Either way, if the Wolff spring works well, I may just end up using it and put the extractor O-ring back in with it. Although I'm obviously no expert, there must be a good reason for the O-ring to be there. That's odd... The o-ring limits the amount of travel the extractor clip has to lock and unlock. I would think no o-ring means the extractor would come un-clipped easier.. as in my case... the extractor appears to be "slipping" off the edge of the shells, But who knows! good luck! BTW pretty sure mine cycles manually fine... |
|
|
|
Posted: 3/3/2014 2:16:10 AM EDT
[#15]
Ejector, round looking object protruding from the face of the bolt at about a 3:00 orientation. It should be fairly stout to depress, but should move freely.
|
|
|
|
Posted: 3/3/2014 2:24:07 AM EDT
[#16]
I was having a problrm with my 7.5 and determined that it was over gassed. Causing similar problems. I installed an adjustable gas block and it fixed the issue.
|
|
|
|
Posted: 3/3/2014 6:05:58 AM EDT
[#17]
H2 buffer and bcm extractor upgrade fixed my problems with double feeds and failures to extract.
|
|
|
|
Posted: 3/3/2014 6:20:19 AM EDT
[#18]
Quote HistoryQuoted:
H2 buffer and bcm extractor upgrade fixed my problems with double feeds and failures to extract. The above, and clean the chamber. |
|
|
|
Posted: 3/3/2014 6:45:19 AM EDT
[#19]
Quote HistoryQuoted:
i say open the gas port Lol, wut? |
|
|
|
Posted: 3/3/2014 6:45:57 AM EDT
[#20]
Quote HistoryQuoted:
not true, more gas = full cycle , thats why DD opens theirs up runs flawless Gas shortage is NOT the problem here. The bolt locks back on an empty mag, but the extractor is slipping off of the case. Does DD even make a 7.5" or pistol-gas barrel? 
|
|
|
|
Posted: 3/3/2014 6:56:07 AM EDT
[#21]
Quote HistoryQuoted: not true, more gas = full cycle , thats why DD opens theirs up runs flawless Personally I would use a heavier buffer and 0 Ring. |
|
|
|
Posted: 3/3/2014 7:16:46 AM EDT
[#22]
putting 1 round in a magazine and it locks back is not full cycle
when you load a full magazine and it runs all rounds with no issues that is a full cycle you need more gas so the bcg goes full back ejecting the round and than comes forward to load a new round |
|
|
|
Posted: 3/3/2014 7:34:31 AM EDT
[#23]
Quote HistoryQuoted:
putting 1 round in a magazine and it locks back is not full cycle when you load a full magazine and it runs all rounds with no issues that is a full cycle you need more gas so the bcg goes full back ejecting the round and than comes forward to load a new round With all due respect, you shouldn't be giving advice on this. If it locks back on an empty mag, it should have ejected. If it hasn't, it's because the extractor slipped off of the case, not because it's undergassed. How many undergassed 7.5" AR's have you seen? Because I've never seen a single one. We get that a bigger port solved YOUR issue, but it will NOT solve this issue, it will make it worse. What length DD barrel were you working with? DD doesn't sell a 7.5" pistol gas barrel as far as I know. Pistol gas is a different animal than say a 10.3" carbine barrel. |
|
|
|
Posted: 3/3/2014 8:19:31 AM EDT
[#24]
well i told him how to fix it , if he doesnt want to do it thats up to him
if you dont like my advice you can give him your own. shorter barrels need more gas thats been proven |
|
|
|
Posted: 3/3/2014 8:21:30 AM EDT
[#25]
Quote HistoryQuoted:
well i told him how to fix it , if he doesnt want to do it thats up to him if you dont like my advice you can give him your own. shorter barrels need more gas thats been proven Do you have ANY experience with a pistol gas system? I'm guessing no. A 10" barrel with a carbine gas port needs a larger than standard port due to the short dwell. A 7.5" with a pistol gas port does not. This from someone who has built several short barrel AR's with zero functional issues. |
|
|
|
Posted: 3/3/2014 8:56:28 AM EDT
[#26]
yes I do, maybe you need to do more research.
I am glad I didnt listen to you when I built up all my 7.5's |
|
|
|
Posted: 3/3/2014 8:57:58 AM EDT
[#27]
So who else here with short barrel experience thinks opening the gas port on a rifle with a skipping extractor that locks the bolt back on an empty mag is bad advice?
pc-ops, explain to me how you think more gas will keep the extractor from slipping off of the case lip? You just keep saying "it will fix it, because DD uses large gas ports" without even understanding the real issue, or apparently even reading the relevant posts. |
|
|
|
Posted: 3/3/2014 9:17:31 AM EDT
[#28]
Enlarging the port is absolutely the worst thing that could be done unless it is very obviously short stroking. Most of the SBR/pistol length uppers come a bit over - gassed to ensure function with most ammo types.
Some extra buffer/carrier/action spring weight as well as a heavy duty extractor spring set will fix a majority of problems. |
|
|
|
Posted: 3/3/2014 9:29:25 AM EDT
[#29]
Quote HistoryQuoted: So who else here with short barrel experience thinks opening the gas port on a rifle with a skipping extractor that locks the bolt back on an empty mag is bad advice? pc-ops, explain to me how you think more gas will keep the extractor from slipping off of the case lip? You just keep saying "it will fix it, because DD uses large gas ports" without even understanding the real issue, or apparently even reading the relevant posts. 20" rifle gas 5.56 20" rifle gas 5.56 20" rifle gas 5.56 18" rifle gas 5.56 18" rifle gas 5.56 16" rifle gas 5.56 16" rifle gas 5.56 16" mid gas 6.8 14.5" mid gas 5.56 12.5" mid gas 6.8 16" carbine gas 5.56 16" carbine gas 5.56 15.4" carbine gas 5.56 10" carbine gas 5.56 8" pistol gas .300 7.5" pistol gas 7.62x39 I've also helped plenty of other people with gas system issues and I'm normally pretty good at troubleshooting and fixing AR problems. |
|
|
|
Posted: 3/3/2014 10:28:04 AM EDT
[#30]
Thanks for all the help everyone! And yes I agree this doesn't sound like an undergas issue to me.
And FYI I'm glad to report that a o-ring under the extractor spring SOLVED THE ISSUE. (So far), I just fired 60 flawless rounds of steel case ammo with 40 of them all in one extended steel mag without any issues!! :):) Just grabbed one from a hardware store for now to tesf until the full kit comes in. Will probably order a heavier buffer too. I checked mine out and they were all steel inserts totalling 2.9 ounces all together. |
|
|
|
Posted: 3/3/2014 10:31:58 AM EDT
[#31]
|
|
|
|
Posted: 3/3/2014 12:17:56 PM EDT
[#32]
Great, now with the carbine buffer you have and if you buy the H3 buffer you can make up any weight buffer in between.
|
|
|
|
Posted: 3/3/2014 12:57:25 PM EDT
[#33]
Quote HistoryQuoted: putting 1 round in a magazine and it locks back is not full cycle when you load a full magazine and it runs all rounds with no issues that is a full cycle you need more gas so the bcg goes full back ejecting the round and than comes forward to load a new round Sir, with all due respect, it's hard to agree with what you're saying. The OP should look at other ways to address an EXTRACTION problem first before doing something drastic like opening up the Gas Port, which is for CYCLING issues. The OP has apparently solved his issues without having to change gas port size. As to the use of 1 round in the magazine to test Cycling: The use of 1 round in a properly working magazine to ensure that the gas system is fully cycling is a proven method used by competition shooters. Now I'm no competition shooter, nor am I even an expert, but I'm really good at watching their YouTube how-to videos, so may I suggest you watch this: That's what they do to ensure their rifles are fully cycling right before competition. |
|
|
|
Posted: 3/3/2014 1:14:27 PM EDT
[#34]
Overgassing can look like an extraction problem. Too much gas results in the bolt moving rearward while chamber pressure is too high, and the result is the extractor slips off of the case head because the case body is effectively stuck inside of the chamber until the pressure reduces.
An adjustable gas block can correct this by reducing the amount of gas, or a heavier buffer can lengthen the dwell time before the bolt unlocks which allows chamber pressure to subside to permit extraction. |
|
|
|
Posted: 3/3/2014 1:21:57 PM EDT
[#35]
Quote HistoryQuoted: That's odd... The o-ring limits the amount of travel the extractor clip has to lock and unlock. I would think no o-ring means the extractor would come un-clipped easier.. as in my case... the extractor appears to be "slipping" off the edge of the shells, But who knows! good luck! BTW pretty sure mine cycles manually fine... Glad to hear you have solved your problem, and it seems to have been a simple $2 solution too. It wasn't clear though if (1) you already had on O-ring on the spring before and replaced it with the one from the store and (2) Whether you did end up using the upgraded BCM spring. Let us know. As to the guys at AIM who supplied my BCG and their advise to take off the O-ring, I think their logic may have been due to the fact that their extractor/spring assembly wasn't opening up enough to fully grab on to the lip of Steel case ammo. Thus, thus taking off the O-ring would allow the extractor to open up some more to get a good grip. Maybe this is a situation that's unique to their Bolt assembly. (By the way, the AIM BCG I use is the same BCG provided by Wilson Combat). |
|
|
|
Posted: 3/3/2014 1:26:58 PM EDT
[#36]
Quote HistoryQuoted:
So who else here with short barrel experience thinks opening the gas port on a rifle with a skipping extractor that locks the bolt back on an empty mag is bad advice? It's bad advice. Since no one has explained the "why" yet, here goes. The standard AR15 bolt design has an unbalanced extractor. There is more rotational inertia in front of the rotational axis (the pin) than behind... so rotation of the bolt during unlocking reduces tension on the extractor. Higher cyclic rate common in short barrel/short gas system configurations means higher rotational velocity of the bolt during unlocking, which means less tension on the extractor. The real fix is to use an updated bolt design, like the LWRC ACB, or LMT Advanced bolt, which has a balanced extractor. With a balanced extractor, tension stays the same regardless of rotational velocity during unlocking. The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Using heavy buffers can help also. Opening the gas port to increase energy to the operating system is exactly opposite of what is needed to fix the problem. The shorter the barrel and/or gas system, the more critical the exact configuration becomes as small changes in gas port size and other variables have proportionally greater impact on the overall operation due to the very high gas pressures and short amounts of time involved. Traditionally, most off-the-rack manufacturers have tended to use oversize gas ports as a consumer-proof way to ensure basic function, but this approach fails when you get to configurations like a 7.5" pistol gas barrel since its very easy to enter the realm of enough excessive energy to create function problems. The very touchy nature of many 7.5s is one of the reasons why many RKIs would advise against such setups, and instead recommend 11" or so with carbine gas as a baseline for compact 5.56 ARs. |
|
|
|
Posted: 3/3/2014 3:22:49 PM EDT
[#37]
Quote HistoryQuoted:
well i told him how to fix it , if he doesnt want to do it thats up to him if you dont like my advice you can give him your own. shorter barrels need more gas thats been proven Dwell time; 7.5's haz it. This is likely an over gas issue. |
|
|
|
Posted: 3/3/2014 4:28:35 PM EDT
[#38]
Quote HistoryQuoted:
The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Just quoting an excerpt from Gamma's post, which is 100% spot on. This is an important element in correcting the issue. By controlling the flow of gas, more pressure can be directed out the muzzle while reducing the amount entering through the system. Not only does this assist you in fine tuning the cycle, but increases velocity due to higher pressures, increasing ballistic performance in the process. Less unburnt powder as well since initial peak temperatures are higher. |
|
|
|
Posted: 3/3/2014 6:23:05 PM EDT
[#39]
Quote HistoryQuoted: Just quoting an excerpt from Gamma's post, which is 100% spot on. This is an important element in correcting the issue. By controlling the flow of gas, more pressure can be directed out the muzzle while reducing the amount entering through the system. Not only does this assist you in fine tuning the cycle, but increases velocity due to higher pressures, increasing ballistic performance in the process. Less unburnt powder as well since initial peak temperatures are higher. Quote HistoryQuoted: Quoted: The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Just quoting an excerpt from Gamma's post, which is 100% spot on. This is an important element in correcting the issue. By controlling the flow of gas, more pressure can be directed out the muzzle while reducing the amount entering through the system. Not only does this assist you in fine tuning the cycle, but increases velocity due to higher pressures, increasing ballistic performance in the process. Less unburnt powder as well since initial peak temperatures are higher. Thanks for sharing your insights. What about an extraction problem I had that was only specific to Steel Case ammo? The Pistol will shoot Brass all day long, but once you load Steel Case, it will be sure to have extraction problems every 3-4 rounds... |
|
|
|
Posted: 3/3/2014 6:25:10 PM EDT
[#40]
Quote HistoryQuoted:
Thanks for sharing your insights. What about an extraction problem I had that was only specific to Steel Case ammo? The Pistol will shoot Brass all day long, but once you load Steel Case, it will be sure to have extraction problems every 3-4 rounds... Quote HistoryQuoted:
Quoted:
Quoted:
The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Just quoting an excerpt from Gamma's post, which is 100% spot on. This is an important element in correcting the issue. By controlling the flow of gas, more pressure can be directed out the muzzle while reducing the amount entering through the system. Not only does this assist you in fine tuning the cycle, but increases velocity due to higher pressures, increasing ballistic performance in the process. Less unburnt powder as well since initial peak temperatures are higher. Thanks for sharing your insights. What about an extraction problem I had that was only specific to Steel Case ammo? The Pistol will shoot Brass all day long, but once you load Steel Case, it will be sure to have extraction problems every 3-4 rounds... What type of steel case? Laquer/polymer coated cases can be a bit harder to extract than zinc coated cases or brass, so if the timing is too early, before the case pressure drops sufficiently, the extractor may slip off the lip or in some cases, rip a chunk of the case lip out. |
|
|
|
Posted: 3/3/2014 9:39:33 PM EDT
[#41]
Quote HistoryQuoted:
Thanks for sharing your insights. What about an extraction problem I had that was only specific to Steel Case ammo? The Pistol will shoot Brass all day long, but once you load Steel Case, it will be sure to have extraction problems every 3-4 rounds... Quote HistoryQuoted:
Quoted:
Quoted:
The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Just quoting an excerpt from Gamma's post, which is 100% spot on. This is an important element in correcting the issue. By controlling the flow of gas, more pressure can be directed out the muzzle while reducing the amount entering through the system. Not only does this assist you in fine tuning the cycle, but increases velocity due to higher pressures, increasing ballistic performance in the process. Less unburnt powder as well since initial peak temperatures are higher. Thanks for sharing your insights. What about an extraction problem I had that was only specific to Steel Case ammo? The Pistol will shoot Brass all day long, but once you load Steel Case, it will be sure to have extraction problems every 3-4 rounds... It really depends. Was the spent case left in the chamber and a fresh round was picked up by the BCG, then jammed into the rear of it? Or was the spent case removed from the chamber, but ended up on top of a new round as it was attempting to chamber? Or did it fail to extract and the bolt closed on a spent round? Or did it partially extract? Stovepipe? Dramatic change in angle of ejection etc....??? Really need more details. |
|
|
|
Posted: 3/4/2014 12:52:52 AM EDT
[#42]
Quote HistoryQuoted: It really depends. Was the spent case left in the chamber and a fresh round was picked up by the BCG, then jammed into the rear of it? Yes Or was the spent case removed from the chamber, but ended up on top of a new round as it was attempting to chamber? This did happen once. In all other instances the spent casing was jammed in the chamber. Or did it fail to extract and the bolt closed on a spent round? If you mean fail to extract, followed by fail to feed, no. Or did it partially extract? The casing would mostly remain in the chamber, in fact, some casings had extractor-size chunk missing from the casing lip. Stovepipe? No Dramatic change in angle of ejection etc....??? None observed. Really need more details. Quote HistoryQuoted: It really depends. Was the spent case left in the chamber and a fresh round was picked up by the BCG, then jammed into the rear of it? Yes Or was the spent case removed from the chamber, but ended up on top of a new round as it was attempting to chamber? This did happen once. In all other instances the spent casing was jammed in the chamber. Or did it fail to extract and the bolt closed on a spent round? If you mean fail to extract, followed by fail to feed, no. Or did it partially extract? The casing would mostly remain in the chamber, in fact, some casings had extractor-size chunk missing from the casing lip. Stovepipe? No Dramatic change in angle of ejection etc....??? None observed. Really need more details. Quoted: What type of steel case? Laquer/polymer coated cases can be a bit harder to extract than zinc coated cases or brass, so if the timing is too early, before the case pressure drops sufficiently, the extractor may slip off the lip or in some cases, rip a chunk of the case lip out. It was the Tula Black Box 55gr - phosphate polymer coated. I inspected some of the casings and indeed I observed a few with extractor-shape chunks ripped out of the case lip. Is this a symptom of early timing? If so, then the more serious I'm getting about replacing all my pistol gas blocks with adjustable ones. I don't want to address the problem from the Upper side of things, because I share my Lower with multiple Uppers. |
|
|
|
Posted: 3/4/2014 1:04:55 AM EDT
[#43]
Well Tula is about as crappy as you can go on the ammo quality scale, but if that's what you want to blast with then you might need to make some accommodations for it.
Tula seems to use a relatively fast burning powder, so the velocity out of standard barrels is low, but the pressure at the pistol port position is high, so an adjustable gas block may help. You may consider a heavy buffer if it's a common issue between several uppers, and it would be cheaper to try than several adjustable gas blocks. This may alleviate the symptoms, but the cause will still be there. Another thing to try is to clean your chamber thoroughly, maybe a light polish. It may not be that extraction is very early, just that it's having a hard time getting the case free from the chamber. |
|
|
|
Posted: 3/4/2014 1:17:04 AM EDT
[#44]
Quote HistoryQuoted:
It was the Tula Black Box 55gr - phosphate polymer coated. I inspected some of the casings and indeed I observed a few with extractor-shape chunks ripped out of the case lip. Is this a symptom of early timing? If so, then the more serious I'm getting about replacing all my pistol gas blocks with adjustable ones. I don't want to address the problem from the Upper side of things, because I share my Lower with multiple Uppers. Quote HistoryQuoted:
Quoted:
It really depends. Was the spent case left in the chamber and a fresh round was picked up by the BCG, then jammed into the rear of it? Yes Or was the spent case removed from the chamber, but ended up on top of a new round as it was attempting to chamber? This did happen once. In all other instances the spent casing was jammed in the chamber. Or did it fail to extract and the bolt closed on a spent round? If you mean fail to extract, followed by fail to feed, no. Or did it partially extract? The casing would mostly remain in the chamber, in fact, some casings had extractor-size chunk missing from the casing lip. Stovepipe? No Dramatic change in angle of ejection etc....??? None observed. Really need more details. Quoted:
What type of steel case? Laquer/polymer coated cases can be a bit harder to extract than zinc coated cases or brass, so if the timing is too early, before the case pressure drops sufficiently, the extractor may slip off the lip or in some cases, rip a chunk of the case lip out. It was the Tula Black Box 55gr - phosphate polymer coated. I inspected some of the casings and indeed I observed a few with extractor-shape chunks ripped out of the case lip. Is this a symptom of early timing? If so, then the more serious I'm getting about replacing all my pistol gas blocks with adjustable ones. I don't want to address the problem from the Upper side of things, because I share my Lower with multiple Uppers. It sounds like the polymer was cooking off combined with a slight timing issue as RDTCU suggested. This issue occurs more commonly in non chrome-lined barrels or barrels with rough and/or tight chambers. Spent cases often need to be tapped out due to the polymer acting as an adhesive. What type of barrel are you using, and do you see any tool marks or rough areas in the chamber? |
|
|
|
Posted: 3/4/2014 5:31:51 AM EDT
[#45]
Quote HistoryQuoted:
Glad to hear you have solved your problem, and it seems to have been a simple $2 solution too. It wasn't clear though if (1) you already had on O-ring on the spring before and replaced it with the one from the store and (2) Whether you did end up using the upgraded BCM spring. Let us know. As to the guys at AIM who supplied my BCG and their advise to take off the O-ring, I think their logic may have been due to the fact that their extractor/spring assembly wasn't opening up enough to fully grab on to the lip of Steel case ammo. Thus, thus taking off the O-ring would allow the extractor to open up some more to get a good grip. Maybe this is a situation that's unique to their Bolt assembly. (By the way, the AIM BCG I use is the same BCG provided by Wilson Combat). Quote HistoryQuoted:
Quoted:
That's odd... The o-ring limits the amount of travel the extractor clip has to lock and unlock. I would think no o-ring means the extractor would come un-clipped easier.. as in my case... the extractor appears to be "slipping" off the edge of the shells, But who knows! good luck! BTW pretty sure mine cycles manually fine... Glad to hear you have solved your problem, and it seems to have been a simple $2 solution too. It wasn't clear though if (1) you already had on O-ring on the spring before and replaced it with the one from the store and (2) Whether you did end up using the upgraded BCM spring. Let us know. As to the guys at AIM who supplied my BCG and their advise to take off the O-ring, I think their logic may have been due to the fact that their extractor/spring assembly wasn't opening up enough to fully grab on to the lip of Steel case ammo. Thus, thus taking off the O-ring would allow the extractor to open up some more to get a good grip. Maybe this is a situation that's unique to their Bolt assembly. (By the way, the AIM BCG I use is the same BCG provided by Wilson Combat). (1) - there was NO existing o-ring. Only a stretched OEM spring. (2) - installed one from the store - tested, works fine now. (3) - haven't received BCM spring yet. Quoted:
Overgassing can look like an extraction problem. Too much gas results in the bolt moving rearward while chamber pressure is too high, and the result is the extractor slips off of the case head because the case body is effectively stuck inside of the chamber until the pressure reduces. An adjustable gas block can correct this by reducing the amount of gas, or a heavier buffer can lengthen the dwell time before the bolt unlocks which allows chamber pressure to subside to permit extraction. This also sounds plausible to me. Quoted:
Quoted:
So who else here with short barrel experience thinks opening the gas port on a rifle with a skipping extractor that locks the bolt back on an empty mag is bad advice? It's bad advice. Since no one has explained the "why" yet, here goes. The standard AR15 bolt design has an unbalanced extractor. There is more rotational inertia in front of the rotational axis (the pin) than behind... so rotation of the bolt during unlocking reduces tension on the extractor. Higher cyclic rate common in short barrel/short gas system configurations means higher rotational velocity of the bolt during unlocking, which means less tension on the extractor. The real fix is to use an updated bolt design, like the LWRC ACB, or LMT Advanced bolt, which has a balanced extractor. With a balanced extractor, tension stays the same regardless of rotational velocity during unlocking. The band-aid fix is to increase extractor tension using extra power spring, O rings, etc. This can cause other issues though. Reducing cyclic rate by reducing the amount of energy going into the operating system will also help alleviate the problem. One possibility for that is to reduce the gas volume by using an adjustable gas block. Using heavy buffers can help also. Opening the gas port to increase energy to the operating system is exactly opposite of what is needed to fix the problem. The shorter the barrel and/or gas system, the more critical the exact configuration becomes as small changes in gas port size and other variables have proportionally greater impact on the overall operation due to the very high gas pressures and short amounts of time involved. Traditionally, most off-the-rack manufacturers have tended to use oversize gas ports as a consumer-proof way to ensure basic function, but this approach fails when you get to configurations like a 7.5" pistol gas barrel since its very easy to enter the realm of enough excessive energy to create function problems. The very touchy nature of many 7.5s is one of the reasons why many RKIs would advise against such setups, and instead recommend 11" or so with carbine gas as a baseline for compact 5.56 ARs. Agree. All this sounds spot on to me. Sounds like possible over-gassing if anything. Was unaware of the unbalanced bolt issue though. To ME it seems that there are a number of factors, all of which contribute to the problem. None of theses issues are exactly right or wrong black and white but any one of them a little out of spec can cause the issue and it seems there are a number or ways to adjust the system to get it back into spec. |
|
|
|
Posted: 3/4/2014 5:54:36 AM EDT
[#46]
Quote HistoryQuoted:
..it seems there are a number or ways to adjust the system to get it back into spec. But drilling a bigger gas port is not one of them... 
|
|
|
|
Posted: 3/4/2014 8:40:59 AM EDT
[#47]
Quote HistoryQuoted:
But drilling a bigger gas port is not one of them... Quote HistoryQuoted:
Quoted:
..it seems there are a number or ways to adjust the system to get it back into spec. But drilling a bigger gas port is not one of them... Lol Yes I would agree. It the bolt locks back then it doesn't need more gas IMHO |
|
|
|
Posted: 3/4/2014 11:34:07 PM EDT
[#48]
Wonder if an LMT enhanced bolt carrier would work here.
|
|
|
|
Posted: 3/5/2014 1:37:03 AM EDT
[#49]
Quote HistoryQuoted:
I also agree that your issue should be resolved with a heavier buffer since spent shell did not get a chance to eject completely before the next round is being pushed, timing is out as it sounds. |
|
|
|
Posted: 3/5/2014 4:32:08 AM EDT
[#50]
Quote HistoryQuoted:
Wonder if an LMT enhanced bolt carrier would work here. It's a nice piece of equipment that could potentially help, but the OP still needs to drop in a heavier buffer. |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
