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Posted: 8/13/2019 10:14:44 PM EDT
[#1]
Verify the hammer spring is correct orientation
Also, what mags are you using? Normal pmags in my experience don’t work with 220 gr or similar profile bullets. You might get the 1st chambered but after that it’s a crap shoot because the tips are jamming up on the little plastic guide in the body. I use hexmags without issue and they’re massively different from pmags so I’ll never accidentally put one in a 556. |
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Posted: 8/13/2019 10:17:11 PM EDT
[#2]
Quote HistoryQuoted:
Verify the hammer spring is correct orientation Also, what mags are you using? Normal pmags in my experience don’t work with 220 gr or similar profile bullets. You might get the 1st chambered but after that it’s a crap shoot because the tips are jamming up on the little plastic guide in the body. I use hexmags without issue and they’re massively different from pmags so I’ll never accidentally put one in a 556. |
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Posted: 8/13/2019 10:18:10 PM EDT
[#3]
You mean when you release the charging handle the bolt goes back to battery slowly? Not fully understanding what you’re saying.
BTW the very light primer strike is likely from chambering the round. ARs have floating firing pins so when the BCG goes into battery the firing pin keeps going under its own momentum and the primer stops it. It isn’t enough kinetic energy to set the primer off but it does strike the primer, leaving a tiny strike mark. |
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Posted: 8/13/2019 10:22:21 PM EDT
[#4]
Quote HistoryQuoted:
You mean when you release the charging handle the bolt goes back to battery slowly? Not fully understanding what you’re saying. BTW the very light primer strike is likely from chambering the round. ARs have floating firing pins so when the BCG goes into battery the firing pin keeps going under its own momentum and the primer stops it. It isn’t enough kinetic energy to set the primer off but it does strike the primer, leaving a tiny strike mark. Perfect. This could be the reason that I am seeing the light primer strikes, they might be what you are saying and not actual light primer strikes. Also, bolt goes back in to battery slowly meaning - 1.) I pull the charging handle back and release it. It goes back hesitatingly, like something is stopping it. Tried doing it again, sometimes it chambers good, sometimes it gets stuck (not stuck actually but there is a resistance and it hesitatingly chambes the round. And in some cases, it just gets stuck midway and does not chamber the round at all. |
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Posted: 8/13/2019 10:23:43 PM EDT
[#5]
Quote HistoryQuoted: I put a CMC drop-in single stage trigger in it. Also, using PMAGS. Let me try using the Hexmags too tomorrow. You will also find a lot of fans of Lancer mags. Their 300blk specific mags are my favorite - not even a close second. To be fair though I’ve never shot hexmags before - not even sure they make 20 rounders, which is what I prefer. |
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Posted: 8/13/2019 10:24:37 PM EDT
[#6]
Is this factory ammo or loaded yourself?
Since the hammer ought to be just fine being a drop in, I’m assuming the poster above is right about the mark being from the pin during chambering. So what’s most likely going on is the round itself is out of spec so the bolt isn’t locking in and allowing the pin to properly strike. I would verify resize die etc. grab a decent chamber type gauge to test the rounds in to make sure it’s flush. The other thing it could be (but you would have a hell of a time extracting) is the coating on the bolt lugs could be too thick causing it to get jammed on the barrel extension before it can rotate closed. |
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Posted: 8/13/2019 10:26:12 PM EDT
[#7]
Quote HistoryQuoted: ---- Perfect. This could be the reason that I am seeing the light primer strikes, they might be what you are saying and not actual light primer strikes. Also, bolt goes back in to battery slowly meaning - 1.) I pull the charging handle back. It goes back hesitatingly, like something is stopping it. |
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Posted: 8/13/2019 10:29:07 PM EDT
[#8]
Quote HistoryQuoted: Did you try to run the BCG without a mag in? That would tell you if it is bolt/BCG/buffer/spring/tube related. If it is fine then your FCG and upper are probably fine and your mags are suspect. I had a hell of a time finding mags my DD liked. If it acts the same without a mag in, then start looking at those parts one by one. Seems like a sane thing to do. No, I did not try to do that without a mag in. A loaded PMAG was always there. Also, to answer some other questions. AMMO : The ammo is factory - Remington FMJ Green Box. Will try some other ammo too to rule out the ammo issues. BOLT: Bolt is a Toolcraft BCG (Black). I also a spare Nickel Boron WMD one, will put that in and see if that is the cause. MAGS: Only using Gen 3 PMAGS for now. Will try a Lancer and Hexmag that I have to see if its mag related. |
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Posted: 8/13/2019 10:37:56 PM EDT
[#9]
To echo some other comments. I had some weird feed issues with regular pmags when using heavier bullets. Got some 300blk pmags and it’s been smooth sailing
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Posted: 8/13/2019 10:39:00 PM EDT
[#10]
As the others said, sounds mag related.
Is the BCG hanging up about the point where it'd be stripping the next round out of the mag? If so, a mag change will fix that issue. The long ogive of 300 blk subs generally is a problem in PMAGs. The much shorter supersonics generally don't have this issue. It's having trouble getting the bullet out of the magazine and that's slowing the bolt down. |
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Posted: 8/13/2019 10:51:23 PM EDT
[#11]
If you're loading a full 30, GOOD LUCK. Only load 25 in mine. Load from open bolt, try again.
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Posted: 8/13/2019 11:01:48 PM EDT
[#12]
Quote HistoryQuoted: ---- Seems like a sane thing to do. No, I did not try to do that without a mag in. A loaded PMAG was always there. Also, to answer some other questions. AMMO : The ammo is factory - Remington FMJ Green Box. Will try some other ammo too to rule out the ammo issues. BOLT: Bolt is a Toolcraft BCG (Black). I also a spare Nickel Boron WMD one, will put that in and see if that is the cause. MAGS: Only using Gen 3 PMAGS for now. Will try a Lancer and Hexmag that I have to see if its mag related. |
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Posted: 8/13/2019 11:03:22 PM EDT
[#13]
Quote HistoryQuoted: Basic 120gr supers, correct? Shouldn't be an issue. Is the bcg lubed well? with the rcvrs apart, have you slowly worked the CH and bcg checking for drag, etc? Bolt moves ok within carrier? |
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Posted: 8/13/2019 11:05:16 PM EDT
[#14]
BTW, contrary to what he said, 300s don'y have inherent issues as some believe.
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Posted: 8/13/2019 11:11:39 PM EDT
[#15]
Quote HistoryQuoted:
BTW, contrary to what he said, 300s don'y have inherent issues as some believe. |
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Posted: 8/13/2019 11:14:27 PM EDT
[#16]
Quote HistoryQuoted:
Yes that is my concern, its doing this with the basic 120 grainers. The gun is at my FFL, will get it this Friday and check for scraping and drag. The drag is the main issue. Will check with another WMD BCG too. Quote HistoryQuoted:
Quoted: Basic 120gr supers, correct? Shouldn't be an issue. Is the bcg lubed well? with the rcvrs apart, have you slowly worked the CH and bcg checking for drag, etc? Bolt moves ok within carrier? |
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Posted: 8/13/2019 11:46:04 PM EDT
[#17]
Will check cycling the bolt with the magazine out to see if that is the issue. If that is the case, then I have a spare WMD BCG to try out.
Will update you guys regarding the findings this Friday. |
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Posted: 8/24/2019 1:44:54 PM EDT
[#18]
Quote HistoryQuoted:
BTW, contrary to what he said, 300s don'y have inherent issues as some believe. |
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Posted: 8/24/2019 7:43:40 PM EDT
[#19]
Cycled the bolt without the magazine and it seems to cycle fine. Looks like the issue was with the PMAGS. Going to try with the Lancer mags tomorrow at the range.
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Posted: 8/24/2019 7:49:15 PM EDT
[#20]
Quote HistoryQuoted:
Cycled the bolt without the magazine and it seems to cycle fine. Looks like the issue was with the PMAGS. Going to try with the Lancer mags tomorrow at the range. |
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Posted: 8/24/2019 11:28:59 PM EDT
[#21]
Quote HistoryQuoted:
I have 2 20s and 1 30 rd lancer 300BO mags, they are awesome. |
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Posted: 8/25/2019 4:46:00 PM EDT
[#22]
Quote HistoryQuoted: The only concern is I was using normal range rounds - Remington Green Box supersonic. Still with the Pmags, they weren't cycling. Will try tomorrow and see what happens. |
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Posted: 8/27/2019 7:27:09 PM EDT
[#23]
Update: Went to the range today to test the changes :
- Replaced the Toolcraft BCG with the NiBo WMD BCG. Not that the BCG was bad but just had a spare one and wanted to rule out the bolt factor. - Lancer 20 round .300 mags with stronger spring for the sub-sonic rounds. Although I loaded the normal Remington Green Box supersonic range ammo. Had a PMAG and a D&H 20 round mag as well. 1.) Put in the PMAG with 20 rounds in it. Pulled the charging handle back and nothing. The round does not feed. The charging handle bot just scrapes back. 2.) Tried the Lancer Mag this time. Round chambered. Got excited. Pulled the trigger. “Click”. Nothing happened. Pulled the charging handle back and checked the ejected round. Light primer strike as shown in the picture below. 3.) Tried the D&H 10 round mag (advertised as .300 mag ..lol) just to rule out the magazine factor. Pulled the charging handle back. Seemed like round got stuck in the chamber. The charging handle wouldn’t pull back either. Had to give the charging handle a good smack to get the stuck round out. As mentioned earlier, I have a single stage CMC drop-in trigger. The light primer strike issue is making me think if it’s the trigger issues. But then, I am using the normal supersonic rounds and why wouldn’t they chamber with the Pmags or the D&H. It takes a Lancer with the stiffer springs designed for the heavier sun-sonic ammo to chamber the rounds. Never had these issues with any of the 5.56 builds before. all sounds a bit crazy.  Attached File |
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Posted: 8/27/2019 7:34:55 PM EDT
[#24]
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Posted: 8/27/2019 8:25:53 PM EDT
[#25]
Did you put stiffer springs in the Lancer? I'm not aware of them changing the spring, just the internal rib dimensions.
Take a pic of the FCG both into the lower and from the side with the hammer up (ease it up gently). |
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Posted: 8/27/2019 8:29:18 PM EDT
[#26]
Quote HistoryQuoted:
Did you put stiffer springs in the Lancer? I'm not aware of them changing the spring, just the internal rib dimensions. Take a pic of the FCG both into the lower and from the side with the hammer up (ease it up gently). Also it a CMC drop in trigger which is completely enclosed. |
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Posted: 8/27/2019 9:04:04 PM EDT
[#27]
Quote HistoryQuoted:
Did not put stiffer springs in the Lancer. My comments comes from the thought that the Lancer mags for .300 BLK subsonic might have stiffer springs to handle the heavier rounds. Also it a CMC drop in trigger which is completely enclosed. Quote HistoryQuoted:
Quoted:
Did you put stiffer springs in the Lancer? I'm not aware of them changing the spring, just the internal rib dimensions. Take a pic of the FCG both into the lower and from the side with the hammer up (ease it up gently). Also it a CMC drop in trigger which is completely enclosed. I don't understand the how the bolt and trigger/light strike issues are related. Possible to try the trigger in another gun? Maybe swap lower the onto a 5.56, and a known good 5.56 lower for your 300blk upper? |
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Posted: 8/27/2019 9:21:14 PM EDT
[#28]
Quote HistoryQuoted:
I use those same 20rd Lancer mags on my 300blk, they're good for me. I don't understand the how the bolt and trigger/light strike issues are related. Possible to try the trigger in another gun? Maybe swap lower the onto a 5.56, and a known good 5.56 lower for your 300blk upper? Only thing I can think on the click is the bolt isn’t going fully into battery. |
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Posted: 8/27/2019 9:49:14 PM EDT
[#29]
Not that it might help but tried to get some pics of the drop-in trigger mechanism. The ones in the end are just pics of the pistol build.
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Posted: 8/27/2019 9:52:15 PM EDT
[#30]
Are there any marks or gouges on the case or bullet after you eject it?
Maybe something in the chamber that I causing the rounds to drag on when chambering? |
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Posted: 8/27/2019 10:10:24 PM EDT
[#31]
Quote HistoryQuoted:
Are there any marks or gouges on the case or bullet after you eject it? Maybe something in the chamber that I causing the rounds to drag on when chambering? 
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Posted: 8/27/2019 10:12:49 PM EDT
[#32]
Quote HistoryQuoted: Yep swap uppers or lowers, either way. I have all three of those mag types and never an issue out of them. Only thing I can think on the click is the bolt isn’t going fully into battery. Thanks much for taking time to read through and providing inputs and guidance mate! Really appreciate all you guys out here. |
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Posted: 8/27/2019 10:22:29 PM EDT
[#33]
Quoted:
when I pull the charging handle, the bolt goes back slowly as something is stopping or pushing it backward. Either way a video looking into the chamber demonstrating this would be helpful. I'm curious. Did you try lubing it up and just using the charging handle to pull the bolt forward/back a hundred times just to see if it loosens up or figure out where the resistance is coming from? |
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Posted: 8/28/2019 12:32:43 AM EDT
[#34]
Quote HistoryQuoted:
You are right, will swap the upper with a different lower and try once again. Also, will put on my 5.56 upper on the current (supposedly) troublesome lower to see if that issue of light primer strikes presents itself. At this point of time, playing the game of elimination. Thanks much for taking time to read through and providing inputs and guidance mate! Really appreciate all you guys out here. Quote HistoryQuoted:
Quoted: Yep swap uppers or lowers, either way. I have all three of those mag types and never an issue out of them. Only thing I can think on the click is the bolt isn't going fully into battery. Thanks much for taking time to read through and providing inputs and guidance mate! Really appreciate all you guys out here. 
Good luck! |
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Posted: 8/28/2019 1:40:04 AM EDT
[#35]
Quote HistoryQuoted:
Kinda goes without saying, but be 1000x careful with your ammo when you start swapping them around
Good luck! |
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Posted: 8/28/2019 5:55:53 PM EDT
[#36]
Quote HistoryQuoted:
Not that it might help but tried to get some pics of the drop-in trigger mechanism. The ones in the end are just pics of the pistol build. https://i.imgur.com/GwPX9ZS.jpg https://i.imgur.com/8xRtZDp.jpg https://i.imgur.com/gKgmkhz.jpg https://i.imgur.com/2m2H1wm.jpg https://i.imgur.com/8RhCUfz.jpg ETA: Pic #3 - grind some of bottom of hammer, or swap out bolt catch for factory one and try first. May be the bolt catch interfering with hammer strike. |
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Posted: 8/28/2019 6:34:47 PM EDT
[#37]
Take out your fire control group and hand cycle it through a full mag. On that FCG does the hammer protrude on the front or bottom at all? With the upper off see how far you can push down on the hammer. I installed a hyperfire trigger in my AR and started have a similar problem. Turned out as the hammer was rotating back it was rubbing on the front of the FCG pocket preventing it from going back far enough, causing it to bind up on the BCG. If the BCG is going forward sluggishly that's probably the issue. While you have the FCG out look for wear areas on the lower and FCG to see where it's rubbing.
Are you saying you have light primer strikes when you pull the trigger, or from cycling it? If it's from pulling the trigger then I'd say it's all caused by you hammer binding up. If it's from cycling, that's normal. Do you have a standard FCG? You said you installed the CMC, so did you keep the old FCG? If so, put that back in. |
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Posted: 8/28/2019 6:44:44 PM EDT
[#38]
I’m going to go out a limb and say firing pin protrusion and pretty much anything related to the BCG itself isn’t the problem, considering you swapped the entire unit with no change. Same goes for mags, as you’ve tried multiple. That leaves you with a few options that could explain the hammer dropping but no good primer strike.
A) The rifle is not fully chambering the round. If the bolt is not fully rotated to the locked position, the firing pin can not protrude through the bolt face enough to touch off the round no matter how hard it’s hit. You might see a light strike like you’re getting, but that’s all. Are you sure the bolt is going fully into battery when it does manage to chamber? B) Something is off with your trigger setup. Maybe the bolt catch is preventing the hammer from fully dropping or something is up/binding with the trigger pack not allowing full cycling of the hammer. Swapping the lower with a known good unit should answer this question, but it doesn’t seem to be the cause considering the “sluggishness” issue goes away once ammo is removed from the equation. I’m inclined to lean towards option A. A hammer that can’t drop fully most likely isn’t going to cause a sluggish BCG issue like you’re describing. Are you sure you were shipped a barrel chambered for .300BLK and not something else? Is the barrel marked? If so, I’d think about looking into chamber issues. |
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Posted: 8/30/2019 12:51:14 AM EDT
[#39]
Thanks @RJeff21, @AASG, @83rdrecon, and all of you above. Went to the range again today. Got a small update.
Put the suspected lower, on my good 5.56 carbine upper to try and isolate the bolt catching, hammer issues if any.....turns out the lower is fine, shot two full mags through the 5.56 upper without any problems. So, the problem could be with the .300 BLK upper somewhere. I also checked the barrel (just to be sure, I have the right one), it is marked .300 BLK Match Series , Faxon something. By the way, just for the record the upper parts are as follows: - Aero Precision Blem upper - WMD Nickel Boron BCG (2nd one after replacing the Toolcraft BCG) - Faxon Match Series- 9" Gunner Barrel, 300 BLK, 5R, 416-R, Nitride - Faxon AR Gas Tube - Pistol Length - Faxon .750" Lo-Pro Gas Block SS - SLR Works Synergy BCF 30 Cal - Titanium - SLR Works SOLO 9" Ultra Lite Handguard -MLOK - Strike Industries Magazine Catch - Red - Strike Industries Latchless Charging Handle - Red - Strike Industries Forward Assist- Red - Odin Works Ambi Safety Selector - Red Since I am going to be traveling for about a week or so, left the gun at a recommended gunsmith. He couldn't figure out anything wrong upon initial physical inspection - the bolt cycle fine, although the upper seemed a bit dry. He is going to take it apart inspect everything, and then try firing it at the range to try to isolate the light primer strike and round not chambering (sometimes) issue. Will update the thread as soon as I get any feedback from him. |
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Posted: 8/31/2019 5:45:26 PM EDT
[#40]
If you’re still having issues after verifying the lower is functioning fine on a 556, you may want to get ahold of a go/no go set and check your chamber. At this point I am suspecting it maybe be a little out of spec causing the bolt to not fully lock, keeping the firing pin from fully engaging, and also this would mean your cases are difficult to cycle out. Alternatively, you could have someone with a 300 blk reamer make a few passes at it.
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Posted: 8/31/2019 5:58:04 PM EDT
[#41]
Quote HistoryQuoted:
If you’re still having issues after verifying the lower is functioning fine on a 556, you may want to get ahold of a go/no go set and check your chamber. At this point I am suspecting it maybe be a little out of spec causing the bolt to not fully lock, keeping the firing pin from fully engaging, and also this would mean your cases are difficult to cycle out. Alternatively, you could have someone with a 300 blk reamer make a few passes at it. |
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Posted: 9/1/2019 4:14:35 AM EDT
[#42]
Might want to check that tool loaning thread to see if someone can hook you up so you just pay shipping.
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Posted: 9/8/2019 11:16:02 AM EDT
[#43]
I’m late to this thread, but I’ve seen this before with 300 rifles before. Did you ever source headspace gauges?
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