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Posted: 2/9/2006 8:31:33 PM EDT
[Last Edit: 3/5/2006 1:48:17 PM EDT by NvrenufRR]
I have read through the posts and done the trial and error tests for this problem with no success.

Colt M4 SOCOM 14.5 1/7 Barrel
Noveske KX3 Krink
LMT M4 A3 upper
LMT M16 BCG W/Mcfarland 1 pc ring and blk oring on extractor
PRI lo-pro gas block
Magpul M93B W/H buffer and milspec spring
LMT factory lower

The symptoms of too little gas are very apparent to me. I've tried USGI mags, HK SA-80's, England SA=80's for mags. I've tried M855 with 100% reliability, Wolf 55 & 62gr polymer, WIN Q3131, and handloads with less than 50% reliability. Most the time its Bang, Bang, Click, repeat
What is happening is the gun will fire and extract but not load the next round, most the time the bolt will not hold open on empty.
I'm thinking it might have something to do with the gas block and its orientation to the gas port, or could the gas tube possibly be too far back or forward.
Anyone know how much to torque the screws on the gas gas block or how to tell how far to install the tube into the carrier ID?
This is getting a little upsetting, this is the 4th upper I've assembled and the 1st with problems. This is the one gun I absolutely want to run 100%, I have alot of time and money invested in this one and I want it to go bang in any situation with any ammo. I'm about getting ready to give up. I've torn this down 3-4 times already and am running out of options.
Anyone know how far from the shoulder the gas block should be spaced?
More info tomorrow
Link Posted: 2/10/2006 6:20:44 AM EDT
[Last Edit: 2/10/2006 6:39:34 AM EDT by Dano523]
Link Posted: 2/10/2006 6:25:41 AM EDT
Have you checked your carrier key screws for the correct torque/staking? You might have gas blow by between the key and the carrier.
Link Posted: 2/10/2006 7:41:31 AM EDT
[Last Edit: 2/10/2006 7:43:27 AM EDT by AR15barrels]
Link Posted: 2/10/2006 8:37:44 AM EDT
Link Posted: 2/11/2006 1:39:27 PM EDT
Alright, I broke down the upper and pulled the block off to check for obvious leak markd from carbon and powder. Everything looks to be ok, no obvious powder marks out of ordinary sizes or locations.

As far as micing the gas block port and gas port on barrel, figue the difference and align CTC, I set the block right up to shoulder on another occasion, ame results as in my previous post, bang, bang, click. The gas block is approx 1/8 in and the port is .060. I've tried a few different variations in spacing.

Is there a test with clp or soapy water to test for the lesk in the barrel, block?

I also noticed the barrel nut is slightly misaligned causint the tube to be a very minimal amount of left centering, I will try to correct the alignment when I can us a vice, I have the proper tools for torqing and tooling of the upper, barrel nut and barrel. could this be the problem?

I checked the torque on the carrier key, torqued to 44.6in/lbs on the tech wrench, and then staked. I tightend down as much as I could furthermore. the carrier does not seem to have any powder burns anywhere signaling a leak.

The tube inside the upper has a nice uniform shint lip where contact with the Carrier would be. The caarier keys ID does not have any sign of abnormal wear or contact, it seems a nice uniform burn all the way around. Powder marks and burns extend approx 1in out from the upper towards the gas block, seems to be in uniform with my other rifles.

I am not sure if the tube is bent or not, the barrel has a white spot centered for the alignment of the tube and nut, as a stated the tube is possibly less than 1/8in misaligned.

Possible other causes;
H buffer?
M16 BCG?
KX3 Krink?

Other possible corrections I am considering;
regular buffer or heavier buffer?
fat boy or pigtailed gas tube? New regular gas tube and swap out old one

I am going to the range tomorrow, I will be bringing tools to change alignment of gas block, AR-15 BCG, Regular buffer, and a wide array of ammunition to test cycling along with magazines, then I'll have an update on progress, I would like to leave drilling out until I have exhauseted every other option.

Thanks for the help so far guys, keep the feedback coming, I am willing to try alot at this point, if anyone can help mee by pics please let me know what you need a picture of and I will post it.
Link Posted: 2/11/2006 3:31:36 PM EDT
A few more questions regarding substitution of parts, If it cycles with a different combination of parts; different buffer or BCG or gas tube, why would it not function right with the other parts?

Take the KX3 for example, I thought it's purpose was to redirict sound and create backpressure to aid in cycling on sgort barrels? If I remove it and the upper cycles correctly, why not with the KX3?

This goes the same for any part I will try alternating, and more importantly, is there still a problem with the cycling, but just corrected by different parts?

When the upper was 1st built it had factory FSB and HG w/no FS and cycled fine w/ar-15 BCG. It wasn't until the adition of the Samson MRFS rifle length, LO-pro gas block and M16 BCG did any problems arise, this included cycling wolf fine
Link Posted: 2/11/2006 5:16:11 PM EDT
Link Posted: 2/12/2006 5:30:32 AM EDT

Also, while you have the gas block off the barrel, you may want to pull the back set screw out and confirm that the gas tube hole aligns with the gas block port hole.


I checked the alignment of the port and blocks, upon removing the gas block there was a nice uniformend mark where contact was made from the gas block around the port, it was slightly forward, but a good 1/16 still around the port on barrel. I realigned this to correct the slight misalignment

Take a look at the disco just behind the hook for signs of the tail of the hammer binding on it as the carrier lowers it down. If needed, you may have to remove some material from the hammer tail if you do find signs of binding.

The hammer looks smooth and fine no signs of abnormal wear on hammer or BCG

The key screws should have been torque at 35 to 37 in lbs. Could be that the screws where over torque, and may be stretching when the carrier gets hot. Also, you did check the key to carrier gas passages to confirm that they align?

As far as the torquing goes I did not loosen the keys due to they were staked, I just tested to see if they were at least 35inlbs tight and they were, possibly more, Can I loossen and retighten staked keys w/o a special tool for the staking?
When you ask about the alignment, do you mean Carrier key to gas tube? I cant physically see the contact, as I noted, the tube had a nice uniform mark around the mushroom, shiny from contact.

The B/C will pass the 45* free drop test in the upper receiver?

I missed this part, please explain

As with any new rifle/parts, make sure to lube the upper bearing parts/surfaces (including the gas rings) with a light coat of CLP. This will add with the parts mating in threw live fire.

The rifle is cleaned and lubed after each range session with Militec-1 and all is cleaned according to manual reference.

Above are just a few of the greatest hits of the FAQ, which are found in the "READ THIS BEFORE POSTING" thread tacked at the top of the first page. If you need the TM manual for specs, it is listed under the manuals under the information button.

Read threw the FAQ, and if needed, I can write the novel for a full-blown checklist related to your specific problem. But in the mean time, do check the above items, and when you do find that the rifle begins to have problems, see if a fresh coat of CLP on the upper bearing areas does resolve the problem. This will resolve if in fact the problem is Gas related or Binding related.


I do notice the rifle runs a little better with the first two mags, but will NOT cycle wolf fresh or hot. After a cool down the problems are consistent.

Going to the range now, more info in a bit, Thank you kindly for the help, I hope to get this resolved rather soon. I will look into FAQ's when I return again to see if there is anything else I missed or can try again and also a few threads tacked here again.
Link Posted: 2/12/2006 6:15:40 AM EDT

Originally Posted By NvrenufRR:
The B/C will pass the 45* free drop test in the upper receiver?

I missed this part, please explain



Hold the upper receiver at a 45 degree angle. Insert carrier and allow it to slide down into place. Does the gas key fit over the gas tube completely without additional force?

Also, you might want to swap out that one-piece gas ring for 3 conventional ones and see if that helps.
Link Posted: 2/12/2006 11:32:34 AM EDT
Range report;

55gr Q3131
55gr handloads- Varget 3050fps chrony
55gr wolf
62gr Fed M855
62gr Wolf

HK sa80 mags
BM 30rd mags upgraded w/ Magpul follower and ranger plate
England SA-80 mags w/ Magpul follower and ranger plate

OK, after a tear down and remicing gas port, tube and block orientation yesterday, to the range I go.
First mags, 20 rds of each ammo, Fed M855 and Win Q3131 function w/o a hiccup, wolf and handloads Bang, Bang, click, then bang, click most of all 20rds.

I changed the BCG to the original LMT bolt and BM 15 BC, reloaded 20rds of each ammo in the mags and try again. everything except Wolf functioned w/o a hiccup, this bolt had original 3pc gas ring.
Tried a few more mags of 20rds, different ammo and same results.
The 55gr Wolf will cycle more reliably than 62gr.

I swap the same bolt to the 16 BC, and results are 50-50 except for Fed M855 & Win Q3131.

Every once in awhile the bolt would still close on an empty mag. Even more rare, (about 4 times) I had double feeds with the fired shell not extracted from upper and next round in mag feeding in, this occoured with Fed M855, Win Q3131, and the handloads.

So I switch back to the LMT bolt w/3pc gas rings and BM 15 BC. Reload, feeds near 95% with some hiccups in Wolf.

Obviously the rifle is very picky about the Wolf, I know it is not good ammo, but it will cycle in anything else I have even W/1pc gas rings.

I put about 1200-1300rds down range, relubing about 300, Alot of problems at the end could have been from over lubing and fouling. DNK, Tonight or tomorrow I will be cleaning everything tip-top, then tear the rifle down again to check for new signs of leaking or carbon deposits. I will also pick a vice up to align pefectly the barrel nut and tube, I really doubt this is the problem. I will be ordering a normal weight buffer since I do not have one to try and some new 3pc gas rings for the other bolt.

Why is cycling more of an issue with the 16 BC?
Will the buffer make a difference and what is that saying?

The brass was coming out much cleaner today than in the past, a good sign I believe.
I did do a 45* test and it passed, you could move the carrier another 1/16-1/8, but it would fall enough on it's own to close the upper to the lower.

What about the Krink? Anyone ever heard of it causing problems?

Awaiting feedback for tonights teardown and inspection, thanks again guys, I'm getting very frustrated with this issue.

Link Posted: 2/12/2006 11:49:28 AM EDT

Originally Posted By NvrenufRR:
Why is cycling more of an issue with the 16 BC?



Because an M16 bolt carrier is heavier than a standard AR-15 bolt carrier.



Will the buffer make a difference and what is that saying?



Yes, too heavy a buffer can cause short stroking.
Link Posted: 2/12/2006 12:49:26 PM EDT
Link Posted: 2/12/2006 1:49:17 PM EDT
[Last Edit: 2/12/2006 1:53:18 PM EDT by NvrenufRR]
Thanks for the feedback guys, Does this still substitute your point in case short-stroke?

I understand the 16 BC is heavier than the 15, but if the rifle was properly working, this shouldn't matter should it?

The 2 bolts I used are Oly for this rifle, Both new and only matted with the upper, does this still matter? If it does I will save one for future replacement.

Regarding the buffer, is it normal for some rifles to not run properly with H buffers? Or is the rifle short stroking and the problem doesn't present itself until the H buffer is installed?

In short, If a rifle is functioning the way it was designed to, do the change/upgrade of parts make a difference?

I would like to believe that no matter what part is used, a properly functioning rifle will fire 100% reliably? I would like to make this rifle run with any part and any ammo.

I didn't add that although I had issues with my rifle, another member of the club showed up with an MP5, Gov't marked M16A1, M4, and a Steyr Aug A3, all title 3's, so at least it wasn't a complete bust, shooting those was very fun, especially the AUG!
Link Posted: 2/12/2006 2:02:45 PM EDT
[Last Edit: 2/12/2006 2:03:17 PM EDT by Dano523]
Link Posted: 2/12/2006 4:43:43 PM EDT
Will do on the parts, I'm going to change out the buffer for a non-H, I already have the stock spring, and will continue with 15 BCG and 3-pc gas rings for a bit, this might just be a long break in period. I am also going to replace the gas tube, ??? WILL A FAT BOY OR PIG_TAIL AID IN MY CORRECTION?

I didn;t add earlier that the CLP most the time while lubing earlier today seemed to fix the problem for a bit, but not with Wolf.

I retried the drop test, the BCG drops in on its own weight but WILL NOT go ALL THE WAY FORWARD. I have to nudge it slightly forward to let the receivers matte.
I lined the gas block forward to it's original position but it made no change

Also, when cleaning the gas tube I sprayed some cleaner (gun scrubber) down it, I couldn't tell if any ran in the barrel with it down, on flipping barrel up, alot came back out, I'm not sure if this is normal to the small gas port in the barrel.

Thanks Very much for the feedback and Help, The rifle cycles better, but not 100%. I will shoot it a bit and post a new report soon, I get to shoot once-twice a week.
Link Posted: 2/12/2006 4:53:24 PM EDT

Originally Posted By NvrenufRR:
I retried the drop test, the BCG drops in on its own weight but WILL NOT go ALL THE WAY FORWARD. I have to nudge it slightly forward to let the receivers mate.



It could be that your gas tube is slightly off center. Make sure that the gas tube does not contact any of the notches on the barrel nut, as this could deflect it to one side. If it is touching, adjust the barrel nut slightly to allow the gas tube to free-float.
Link Posted: 2/12/2006 6:14:54 PM EDT
Will do on the gas tube orientation M4; I am picking up a vise this week, I will realign the tube, it is slightly offcenterd. ?? I am assuming the drop test allows the the BCG to fall completely into the upper so both upper and lower matte?

Still wondering about the Fat Boy Tube, Anyone have any experience or thoughts? If I'm buying a tube anyway, if this would benefit me I would like to try it.

Maybe not the right forum, but, My KX3, how many rounds before I replace te cone? I clean it each session and the inside of the screw in cone is becoming non uniformed in shape.
Link Posted: 2/12/2006 6:24:43 PM EDT
Link Posted: 2/12/2006 10:29:22 PM EDT
Link Posted: 2/13/2006 5:17:25 AM EDT
[Last Edit: 2/13/2006 5:18:39 AM EDT by NvrenufRR]

Originally Posted By Dano523:
www.ar15barrels.com/gfx/223plot.gif
Credit for the photo goes to AR15barrels.

On short barrels, the bolt unlocks during higher barrel pressures, and the fat boy/ pig tail slow the gas system charge down (longer dwell until peek gas system charge pressure) to allow more residual barrel pressure to be lost the out muzzle before the bolt unlock (residual pressure on the spent case being pressure bound to the chamber walls is lowered).



I'm not understanding, I've heard on short barrels that the bolt unlocks before the pressure is max, so there is too much pressure in chamber, but, with my particular problem will this aid in correcting, or increase the problem, sorry for the confusion, thanks for the info
Link Posted: 2/13/2006 6:21:09 AM EDT
Link Posted: 2/13/2006 9:59:56 AM EDT
Link Posted: 2/13/2006 11:10:24 AM EDT
[Last Edit: 2/13/2006 11:12:17 AM EDT by Dano523]
Link Posted: 2/13/2006 12:03:35 PM EDT

Originally Posted By Dano523:
HUNTER223, since the port size for a 14.5" barrel is from .063" to .078" range, I am trying to confirm that your barrels are set up to run the Hot Nato ammo specific (.063 gas port with sidewall chamber on the looser side).



HUNTER223 is running the same barrel that I am on my M16 -- a genuine Colt M4A1 barrel. These are military barrels. Mine runs 100%, but I feed it nothing but Lake City ammo.
Link Posted: 2/13/2006 12:13:34 PM EDT
Link Posted: 2/13/2006 2:26:24 PM EDT
Hello again, Well, I tore down the rifle completely today for an overhaul,

The gas port mic'd @ .060, I also mic'd the gas block hole and aligned properly for CTC.
I checked the gas tube and gas block for any obstuctions and none found, I checked the gas port for obstructions and none found. Sprayed some Gunscrubber spray through the whole system unassembled and ran through fine, cleaned the tube w/pipe cleaner too before.
The carrier key was checked also for obstruction and sprayed too, passed with flying colors.

I took off the KX3 Krink and left it finger tight so next range session i can just remove it to test.
Loosened and retorqued the barrel nut for alignment of the tube into upper and tried drop test, still not a full lock, I have to nudge it about 1/16 in to seat fully.
Checked the gas tube for straightness and looked good to my eye and tests.

It may be a possibility this gun might only shoot NATO spec ammo for a bit, I am running a Genuine Colt M4 SOCOM barrel from SKICH here on ARFCOM.

I am going to give it a bit before anything other choices. I DO however think I am going to replace the gas tube and buffer. I do not want this rifle to cycle underpowered ammo only, if I have to feed it only Q3131, M855, & M193 for abit thats OK, I have a bunch. Hopefully after a couple of K through it this problem will disappear.

I'll update after next range session with buffer, tube and Krink fixes, To me though these steps are go arounds not fixing the problem, but if it will cycle properly, I guess I'm happy.

If anyone has anymore suggestions or comments please leave them, To everyone who has tried to help me correct this issue, THANK YOU VERY MUCH!!!

LMT BUILD $2500 someodd dollars
AMMO $$200
Fixng something yourself $ Priceless
Link Posted: 2/13/2006 3:59:41 PM EDT

Originally Posted By NvrenufRR:
It may be a possibility this gun might only shoot NATO spec ammo for a bit, I am running a Genuine Colt M4 SOCOM barrel from SKICH here on ARFCOM.



Mine came from Skich as well.
Link Posted: 2/13/2006 4:17:07 PM EDT
Link Posted: 2/13/2006 4:21:08 PM EDT
Link Posted: 2/13/2006 4:23:41 PM EDT

Originally Posted By HUNTER223:
now someone here mentioned and "adjustable gas tube"???? Please man, give us a link like right after you read this.



www.mgimilitary.com/gastube.htm
Link Posted: 2/13/2006 6:35:27 PM EDT
My understanding of the adjustable gas tubes are that they basically just help you tailor the brass ejection path??? Not so much can help with the issue of Short stroking or over pressure??
Link Posted: 2/13/2006 7:54:50 PM EDT
Link Posted: 2/19/2006 4:57:21 PM EDT
[Last Edit: 2/20/2006 9:02:23 AM EDT by NvrenufRR]
Alrighty, I'm back again.
I got out to the range after the complete tear down earlier for some R&D
Loaded up 8 mags of various man, including 3 brand spanking new D&H teflon w 2nd gen Magpuls.
Also removed the Krink forcing cone for the first 8 mags.

Everything functioned without a hiccup, every mag, every type of ammo, I was quite happy.

Put the Krink back on and got about 50% reliability, same old short stroking issue and the bolt would come back enough to pick up the next round from the carrier end, but not the bolt face, so i had a bunch of jammed rounds in between the BC at an upward angle into the chamber.

I respaced the gas block .065 from the bottom of the shoulder this time.

I take todays range trip as a good thing, no other changes except the Krink and had better reliability and a step in the right direction, at least the bolt will come back enough to start the next round.

Is there any possibility the whole setup is too heavy for reliable function? I mean this thing is Heavy with all the ubertactical gear on it?

Anyways, I'll do a thorough cleaning and lube including the mags and try again next week with an update. I won't rest until this rifle runs right ALL THE TIME!!!! I'll be removing the Krink for the whole session next time, this time I removed it and replaced it, all the time I had before I ran out of light.
I would be really shocked if the problem is the Krink, and really bummed out, it was expensive and works real well for recoil, plus it totally adds to the uber tacticalness of it all.
Link Posted: 2/19/2006 4:59:23 PM EDT
Link Posted: 2/19/2006 6:25:22 PM EDT
[Last Edit: 2/19/2006 6:27:45 PM EDT by AR15barrels]
Link Posted: 2/19/2006 6:51:23 PM EDT
Link Posted: 2/19/2006 7:07:11 PM EDT
Link Posted: 2/19/2006 7:10:33 PM EDT
Randall,
The extarctor marks on the brass are pronounced well, I didn't check Krink vs no Krink.
I am running a H buffer in the tube on Magpul M93B and o-ring in the extractor but no extar ower spring for the extractor or buffer assy.
The new problem is that the BCG will almost pick up the next round from the mag, but not with the bolt, only the carrier will make contact with the next round. I haven't had any extraction problems regularely, only twice last session, none this time or before switching the carriers and bolts. I think part of the original problem was the 1pc gas ring.
I have ordered a new FS to install and try this coming week to research the Krink theory, my understanding of the new Krinks is they work the same as the old ones, it is possible that it is creating too much pressure.
I read through the article you posted and don't really see my association with overpressure problems though.???
BTW, my 6.8 barrel is awesome and another thank you to you for the great work on that buy! What was the twist rate again??

I'll keep everyone updated to my status after next session with a new gas tube and FS.
Link Posted: 2/19/2006 7:20:38 PM EDT
Link Posted: 2/19/2006 8:41:09 PM EDT
[Last Edit: 2/20/2006 12:21:44 AM EDT by Dano523]
Link Posted: 2/19/2006 8:51:08 PM EDT
[Last Edit: 2/19/2006 8:53:09 PM EDT by AR15barrels]
Link Posted: 2/21/2006 10:28:25 PM EDT
Link Posted: 3/5/2006 1:55:32 PM EDT
I've had it!!! I quit with this thing!!!!!

OK, I tried a new ISMI spring and 9mm buffer today with all the loads and mags. The problem became worse. Bang, click, repeat on every load except for 5.56 mil-spec ammo.

I have noticed that the brass coming from this rifle comes out incredibly dirty, with almost a film on it, regardless of handload or factory manufacturing. I fired another AR with it today and the brass was night and day differece in amount of carbon deposit.
The rifle preferred neither style of BCG or FS.
All results were the same, bang, click, repeat.

I'm going back to the h-buffer and regular carbine spring and sticking to the 5.56 spec ammo only with this one. It's not that great of a conclusion, but it is the only reliability I can get.

Many thanks to EVERYONE who tried to help with the error correction and all the information, I lost this battle guys, but the war has just began. I decided to build a new AR in it's place for massive ammo dump and functions 100%, go figure, almost the same setup.
Link Posted: 3/6/2006 3:06:13 AM EDT
[Last Edit: 3/6/2006 3:08:34 AM EDT by metroplex]
Did you try:

Standard 3 piece gas rings?
Standard Buffer with standard carbine buffer spring?
Standard flash suppressor

The black film sounds like powder residue, and it may be from overfunction (removing cases too early?).

How is the condition of your chamber? Is it smooth or does it have nasty grooves?
Link Posted: 3/6/2006 6:28:30 AM EDT
Link Posted: 3/10/2006 9:17:09 AM EDT
OK, I had another brainstorm yesterday..

I am going to cut the top of the original FSB and fashion it to a low profile gas block to fit under the HG's and replace the gas tube, ( although I do not think the gas tube is bad, it flows unrestricted.

I'll keep you updated to the result, who knows, maybe the PRI gas block is just cooperating with the gas system.

I'm also going to try some other NEW ammo, Hornady, Remington, Black HIlls and some other commercial stuff, I'm willing to try anything twice!

Link Posted: 3/10/2006 2:56:57 PM EDT
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