M14 Forum

SAPPNASTY

Okay, I have done what I could and I still can't figure out a few problems I have been having with my most recent custom build. I built this rifle about 2 months ago and I have had a few issues with it from the completion day. This was my first full 100% build, so be easy guys. Okay here is the problem. First thing I noticed what at my first day at the range. I used a brand new Daniel Defense 16" 1:7 barrel for this build. Right out of the gate, I noticed that the accuracy was not what I expected it to be. I was obviously hitting a man sized target at 100 yards, however the groups were anywhere from 3-5"s. So problem number 1. Problem number two, from the first day I had several failure to feeds and sometimes the bolt would come back just far enough to eject and chamber another round. Other times, the bolt would open and eject, but fail to pick up a round...leaving me with an empty chamber. At first it was only one every 20-30 rounds..but know it has been one every 5-10 rounds. I have done everything I can imagine to fix the issue. I have replaced the buffer spring 3 times and even changed the buffer itself. I started with a Spikes Heavy ST-T3 buffer and though that may be the problem. Correct me if I'm wrong but I figured the heavier the buffer, the more force it takes to move it back and operate the bolt correctly. So I changed it to a standard weight mil-spec buffer...SAME PROBLEMS. I also took the rifle down and used pipe cleaners to clean out the gas system...cleaned all of the carbon off and basically made the rifle like new as far as clean goes....SAME PROBLEMS. I am using a Daniel Defense BCG, but it cycles fine under manual operation so no issues there. My guess is that it seems as though the rifle is not getting enough gas pressure to operate the system correctly. I made sure the tube was straight when I installed it and everything still looks correct....except for one issue. I noticed that at the gas block where the tube goes into it, there seems to be carbon build up on the tube and edge of the gas block...for the life of me I can't remember if this was normal or if I ever even looked at one of my older rifles. It almost appears as though a large amount of gas may be escaping through the gas block and gas tube where they meet. If this is thee issue, then how can I correct it? Also, would this effect the accuracy of my shots? I have used several different types of ammo (all premium) as well as a few match hand loads and I always get the same result. I have a 2 gun match on the 27th of this month and I would really like to have it worked out by then. Also, I have used several different types of mags both aluminum and polymer...same result. Please help, but be gentle...lol

82nd ABN

May sound strange but I had a problem similar to yours on my first build. I thought it was the gas block alignment so I took a piece of surgical tube and placed it over the end in the upper and blew into it to see if I was getting air in the barrel. Maybe you could do the same thing to see if there is a leak where the gas tube goes into the block I have not had any gas blowing out there but I have had carbon and not much blow out between my gas block and barrel. My problem turned out to be the heavy spring and hydraulic buffer. I changed everything to gi and it worked fine. No other combo would work. Not the heavy spring and gi buffer or the light spring and the hydraulic buffer. If that didn't work my next step was to start taking weights out of the buffer.
I have to ask, did you install the little roll pin on the gas tube to hold it in the gas block? Is the gas tube the correct length for the build? What is the build rifle length carbine mid length? Is the gas key on tight and staked does the gas tube go all the way into the key? What gas block are you using? Is it a A2 front sight base? It has been my experience which isn't vast that you were on the right track. If its not getting enough gas there is a miss alignment or a leak. Or the spring is to stiff still. You can try cutting off a coil at a time but or removing weights from the buffer. If you cut the spring and it keeps doing it you jut ate a spring. I have only built five of these puppies and only had trouble with short stroking on one, the first. Ia m sure more experienced builders will come along soon. I take it you are using oil rather than grease right.

jake2far

First I assume you are working on an AR platform.
Take the bolt out of the carrier and insure the gas ring is installed correctly. If the gas ring is not installed properly it can cause this problem.
The buffer weight has more to do with cycle rate than short cycle, it can cause short cycle but normal changes in weight of buffer slows down or speeds up the rate.
The gas tube should not be leaking gas around the block, you should find out why it leaks. This could be your whole problem.
As far as accuracy, fix what you know is wrong, get it running correctly and than see how it shoots.
Make sure the gas key is installed correctly to the carrier, insure the port in the carrier lines up with the port in the gas key. Make sure the key is tight to the carrier.
Good read here:http://ar15barrels.com/prod/operation.shtml

Jim

Bolt2bounce

A small amount of carbon at the gas tube and front sight block is OK, usually it will show up after a while of shooting.. is the Gas key tight and staked?? is the bolt gas ring a standard three rings.. or the one piece ring?? the one piece of mcfarlan ring can be too tight sometime and cause undue friction.. It sounds like your gun is trying to run so most likely the the gas tube being misaligned in the upper receiver and hanging up in the carrier key.. test this by taking the bolt out of the carrier and into the upper receiver and it should move closed all the way freely with out sticking.. lube the snot out of the BCG and use a standard recoil spring and buffer .. B2B

SAPPNASTY

82nd: I did install the roll pin for the gas block and was careful to make sure the gas tube was inserted correctly. The barrel is a 16” carbine length and the gas tube is also carbine length. The gas key appears to be on correctly, is tight and is staked very well (better than most I have seen) and the gas tube appears to go all the way in like it should. I am currently using a Midwest Industries low-profile .750 gas block. I would just think that with it working sometimes and others not, it has to be a gas issue…hmmm. If it is in fact, let’s say a misaligned gas tube, how the hell do you ensure that it is correct? As far as the springs go, I have tried 3 different springs and all were close to the same length minus 1/8 or so.

Jake: That was one of the first things I looked at and all three gas ring gaps are separated from each other or “mismatched” as I call it…so the gap on each ring does not line up. Again, I suspect the main issue is the gas block by the looks of the carbon around the tube and gas block…I only have about 500 rounds through it and would not expect this type of build up if nothing was wrong. If this does turn out to be the problem, how can I fix it? If the gas block leaks with the tube installed and the tube is the correct size, what else could it be? Crooked gas block or tube? It all looks very straight as far as I could tell.

Bolt: Now that you mentioned the tube being misaligned, I did notice several little marks on the very tip of the gas tube when cleaning it Monday. Although the thought ran through my mind, so I took the charging handle out of the equation and used gravity to slide the BCG back and forth in the upper receiver and it seemed smooth. It did not appear that the BCG was hitting the gas tube, but I could be wrong. As far as the spring and buffer go, I am still using the standard Mil-Spec version of each…same problems.

82nd ABN

I say try a piece of tube on end of the gas tube and ow through it. It might bs blocked with something. I'm out of ideas at this point. See if you can feel air leaking where you see the carbon coming out when you do it. A short piece of vacuum line hose or surgical tube or fish tank hose will work.

If the portion of the gas tube that protrudes into the upper receiver is not straight it can bs caused by a couple of things. The gas block not being on straight or the teeth on the barrel nut are not perfectly lined up with the hole in the upper.

82nd ABN

You want to ensure that the gas block poet and the gas port on the barrel are lined up also.

SOCOM42

Some aftermarket carriers were screwed up at the bottom of the bolt bore, gas rings could not seal properly. The relief cut was to long.

Mindfield

its a gas issue and/or a buffer issue, get rid of the heavy buffer it is NOT needed unless its full auto, try a standard one

check to make sure your carrier key is tight and that your gas rings arent aligned

also NEVER put ANYTHING inside the gas tube, not even the long pipe cleaners, some carbon buildup in the front sight can help seal the gas system so it runs better

make sure the barrel is aligned and the teeth around the delta ring arent canting the gas tube as well

Seventh Fleet

What I would do is take it back apart and then put it back together, inspecting each individual part as the rifle went back together. I would pay particular attention to the gas block and make sure that the hole in the barrel is the correct size.. While I had the gas tube off I would make sure that it is scrupulously clean. I would try another known good bolt carrier and bolt with a spring and buffer assembly. I've built several AR's have found them to be an easy build with no issues but I've used Stag Arms parts which I've found to be consistently good.

I would also get the weapon functioning correctly before I worried about the accuracy.

7th

Albud3

OK, you've checked the gas rings and they are misaligned per the FM. 500 rounds through the rifle so the rings and bolt have had enough time to smooth out within the bolt carrier...so far so good. Gas key "HEAVILY" staked...not so good. Check to insure that the displaced metal from the stakes is not contacting the track in the upper. If the stakes are too heavy or misaligned, they can cause short-stroking per your report. If you have access to any of the M-16 TMs to see what is allowed per displacement. Contact with the upper will show up as 'bright' or 'smooth' marks within the track the BCG slides in.

Pull the handguards off the upper and shine a bright light from the inside of the upper...make sure there is no contact between the barrel nut teeth and the gas tube. Any contact, however slight can cause a misalignment between the tube and gas key. The tube should be centered within the teeth, but not really necessary as long as there is no contact cold or hot. Shoot approx. 30 rounds and check again; sometimes gas tube will expand and contact teeth. Per your remark that there seems to be some marks on the gas tube: clean the gas key as well as possible, make sure it's dry and take a magic-marker (or Prussian blue if you access to it) and mark the inside of the gas key (NOT tube!). Run the BCG a few times as if fired and see if any of the marker has worn off or transferred to the gas tube. If yes, your tube is misaligned or bent. Or the key might be misaligned or bent, but this is very rare.

Next is a little involved. There should NOT be ANY leakage from the gas block! This is a big uh-oh as it shows there is a misalignment or leak from something. If the gas block is held on by pins, your best bet is to contact the manufacturer and see what they say. Do not allow them to blow it off by saying some leakage is normal...it is not! Any leak will decrease the amount of gas getting to the BCG and WILL (not could) cause problems. If the block is held on by screws, remove block from barrel and check roundness of the inside surface and the flatness of the mounting surfaces. Check that the gas port aligns with the gas tube with the pin installed. If everything checks OK, there might be a slight misalignment when assembled on the barrel. Get everything loosely attached (no tube), shine a very bright light down the barrel and make sure you see the light coming through the gas port of the block. Slightly turn the block both ways until you see the brightest light coming through the port and tighten to specs carefully so you don't misalign it. Reassemble everything and shoot enough to see if any soot shows up again. If so, something is wrong with either the barrel's or gas block's roundness or mating surfaces. Contact manufacturer.

This is about all I can think of at this time. It's been a long time since I worked on an AR/M-16 with this problem and I hope I covered everything. Good luck.

ArmyCPT

Okay, from a quick read of your initial post, OP:

1. It's not the rings. The staggered thing is an old wives' tale. As long as they're present and serviceable, they're GTG.

2. I'll go out on a limb and say it's not your BCG. A well-staked full-auto BCG from Daniel Defense should also be GTG.

3. You probably should run an H1 buffer for all-around performance; however, this doesn't sound like a buffer/buffer spring issue.

My stockade lawyer opinion is that it's your gas tube, and it's most likely not seated in the gas block correctly, or the block's not lined up 100% correctly. Try installing a new tube and see if the problem remedies itself.

Finally, lube the shiznit out of the BCG prior to firing...run it wet.

Good luck, and let us know how it turns out!

82nd ABN

Finally, lube the shiznit out of the BCG prior to firing...run it wet.


Love this!!!! have not heard shiznit in quite some time.