XM16E1 clone troubles

I finally got a chance to go to the range for the first time and shoot my XM16E1 clone. I was pleased with it, except for the fact I have a single shot rifle. It is ejecting, but isn't picking up the next round. I tried it with a newer commercial colt mag, a PMAG, and an old aluminum follower mag. The aluminum follower one also created a few double feeds. I popped in my M261 22 conversion, and that worked great. So I am assuming it is a gas issue? I think eiher the bolt isn't going far enough back, or it is going too fast? I am using just a standard GI buffer, the BC is DPMS with a Colt bolt and USGI parts. Any ideas on how to fix it before I throw it down the driveway?

Thanks!

If you load one round into a magazine and fire it, does it lock the bolt back after ejecting?

Is it possible you have an A2 buttstock screw instead of an A1 buttstock screw?

Having a few more facts might better help to diagnose the problem...

What type/brand & weight of ammo are you using? (also how old/new is it?)
Were you supporting the gun by the mag when you were firing? (if firing from prone, bench, or kneeling position)
Got any pics of the interior of the weapon or of the mags? (to show for pos. indications of dragging or abnormal wear)
Are you using a full-auto or semi-auto type carrier?
Did the fired casings show any abnormal marks on them (bulging, abnormal dents, or gouges, ect.)?
Any abnormal wear marks near the rear receiver ring or buffer retainer pin area? (gouging, ect?)

This. Or, replace the buffer spring. The more details/pics about the build, the better. Listen, don't freak - we'll get it running for you. Did you lube the snot out of it? I always do that, especially when breaking new uppers in. I wouldn't use a DPMS part period, but I doubt that's it. Really need to get more details.

No to the A2 stock screw as well.

More details about the build (pics will come later, too dark to get good ones now)
Citadel barrel, no flash FSB, pinned by John Thomas
Colt bolt, surplus parts, DPMS carrier.
Colt/surplus lower parts
NDS lower
Type D stock on surplus tube
Surplus 603 upper

Yes to lubing it. Yeah looking back I probaby shouldn't have done the DPMS carrier, but it looked solid I guess.

Make sure your gas tube isnt slightly bent in the upper receiver. My brother had a similar issue and it would cycle some of the time other times it would only eject.

Try some brake cleaner in the gas tube to insure it's clear. .22LR willl clog a gas tube quickly - you should always run a few rounds of 5.56 afterwards to clear it out. Did you run the .22 LR first, without trying the 5.56? I'm wondering if the previous owner was using it for .22LR as well. Just a thought - the only one I have this early unfortunately.

Most of the time problems like this are caused by a bad magazine or bad ammo. It looks like the mags are not the problem because you switched them around.

You may have a bad lot of ammo. It happens. It happen to me a couple of years ago. Same problem as you. I couldn't figure it but it was fixed with different ammo. I had bought 500 rds of surplus XM 193 and it simply did not have the pressure to cycle my rifles. I had to dump the ammo.

If it is not the ammo or magazines and you have a good rifle buffer and it is lubed right then it has to be the bolt or the gas tube.

You can see if it is the bolt simply by switching it out with another and see what happens. It is probably not your bolt if the problem is not cycling. Usually bolt problems are extractor problems.

If it is the gas tube then it could be clogged or not aligned properly. It is even possible the gas hole is obstructed.

I would check out the gas tube.

I had a modern rifle that I had built, first time at the range it would shoot a round then lock up.
Re charge it, it would fire two then lock up.
Turns out it was a slightly bent gas tube , just enough to catch the bolt key and drag.
New pipe and it ran great

5.56 first, then 22 after to see if there was a problem. The previous owner didn't use it for 22, because there isn't a previous owner, I built the rifle. Brand new barrel and gas tube.

I am going out again today and I am going to shoot a few founds of M855 and see if it is just a bad batch of ammo causing it. I'll pull the gas tube if not.

I have also this situation if the gas tube key is not staked to the bolt carrier and it comes loose.

––fjruple

Get rid of the POS DPMS carrier, then let us know. I've seen gas keys that weren't bored concentrically etc. LC's onto something. First thing you do when you have an issue like this is swap the BCG.

Just got back from the range. Pulled the handguards, no weird bends. Used friends BCG, same issue. Used 3 different kinds of ammo, no dice. Cleaned out the gas tube, nothing. Tried 4 more different mags, nothing. I am thinking it is a feed ramp issue, they don't quite match up. Going to check headspace as well. Thanks to everyone for their suggestions!

I bet money that the gas tube is bent inside the upper receiver.

this is excessive, but it doesnt take much to hold the bolt up and stop it from working.

Okay, you're on. I will paypal you $1 USD if you're right. (Not being snarky, I appreciate all suggestions and will gladly lose this bet if it means my rifle is fixed.) I have visually inspected it, and it doesn't seem crooked, but I will pull the tube and check it out.

What i did was pull the upper off, insert the BCG and slide it forward. it should really smooth till you get the bolt all the way into the barrel extension. the last .250 of a inch shouldn't be hard to push forward. once all the way in slowly slide it out.

If you feel it get stuck then free up see what the bolt is is doing when it free's up.

If all else fails, it may be that the FSB is installed improperly. Or possibly the gas tube isn't seated into the FSB properly. I've seen both happen before. The big difference was that the guy assembling the rifle put the FSB on himself and didn't align the gas port in the barrel with the FSB. The only thing that saved him was that it was a gas block that only required set screws. Five minutes worth of adjustment time and the gun was cycling.
No guarantees, just a possibility.

It wouldn't hurt to check the alignment of the gas tube hole with the hole in the FSB. I had one that the tube hole did not quite line up and it was cutting the gas off. I pinned the tube and ran a drill bit up thru the FSB. It's unlikely, but it doesn't hurt to check.

Ok, something else to check would be to remove the bolt-carrier assembly - extend the bolt & see if the bolt will support the weight of the carrier when balanced by the bolt head on a flat surface. The bolt should stay extended when balanced... If the bolt fails to support the carrier (carrier collapses down onto the bolt), then replace the gas rings (as well as the cheap $5 cam pin) as this usually means that gas pressure is leaking around the rings & is contributing to the problem. These parts are both very inexpensive & easily replaced.
Also - as stated by others here - check the alignment of the gas tube with the carrier key by the following method: With the bolt removed from the carrier & the charging handle removed from the upper receiver, manually slide the carrier into the upper receiver until fully seated while checking for any resistance from the carrier key hitting the tip of the gas tube. repeat this process with the receiver in both the normal upright position (as when shooting) as well as with the receiver lying on it's top face (upside-down as when servicing or cleaning the weapon) If resistance is noted - either adjust (carefully bend) or replace the gas tube until alignment is achieved (at it's worst, there should only be the slightest of perceivable vibration or resistance when the gas tube enters the carrier key.) Use extreme caution if / when making any adjustments to the gas tube as it doesn't take a lot of force to cause it to bend or flex!

Hope this helps...

It's looking like I owe someone a dollar after trying the method of slding the carrier in without the bolt in it.

The rounds are scraping on the feedramps, which threw me off a little bit, but I am going to replace the gas tube as soon as I can pick one up. I will keep everyone updated! Thanks for all the help!!!

Glad you figured it out. when my brother had the problem we just bent it back using a screw driver and tweaked it back.

Well I got a new gas tube from Jhud, and checked it again with the bolt-less carrier, and it feels way smoother, so I am thinking it's fixed. I will be testing it out this weekend hopefully, and will report back. THanks again guys!

Just an added 2 pennies.Sometimes the tube looks bent inside the receiver,but this is caused by not having the barrel nut notches perfectly aligned with the gas tube hole on the receiver face.You may remove the tube and inspect it but not find an actual bend,but if the nut is off a degree or 2 it will force the tube to one side or the other inside the upper.

I'd have tried the BCG in another weapon immediately and one from a smooth running weapon in your new build. Is your Colt bolt one of the $25 used specials? If so probably needs a re-build. I've also seen 77 and 80gr ammo hang at the feed ramps, main reason for M-4 ramps. Don't sweat it. We can get you smooth running. Many times the surplus stuff needs a little finesse work. Most got switched out simply because armorer couldn't keep it running smooth until complete A-2 upgrades. DPMS isn't as bad as it sounds. I know of two DPMS BCG's with over 10K through each with no hicups to date. I sold one of them at 7K. Where you live? Check hometown section. I'm sure most any local retroland member will help you out. Also check both sides of the feed ramps. Take a round out of the mag to swap side of feed and see if it cycles. Narrow down the problem.

Yep, I did check a different BCG right when it started. Bolt was a brand new MPC bolt. I'm in Utah. F4ENUT (I think that's the proper spelling, going off memory) was generous enough to offer me help when I first started this build, but I haven't had to take him up on it yet. I really think this new gas tube will solve it, if not, I will try these other suggestions. Thanks again guys!!

Always look for the obvious first.

Most the H-D's I repair have been back to the dealer trained technicians a couple times before they bring them to me and it's usually very simple stuff like axle out of alignment or drive belt or clutch adjustment too lose/tight. Almost feel bad about charging them but the dealers sure didn't and they can't charge repair bills if the parts don't wear out. H-D dealer repair is a fine example of not getting what you pay for in my opinion. Almost like a dealer service is paying for them to screw something up.

With AR's I've virtually never had a problem on a build. Never had a bad mag, etc. No FTF in over 23K rds. One day for sure but not yet. Have fixed others that had parts wear out but usually a pretty simple fix. I do keep spares in my tool/gun bag. I ride 40 miles to shoot and I'm gonna shoot. Also usually take two with me. Failing to plan is planning to fail.

Polecat30 - Just another Utah option here if you want some help troubleshooting - not that I am an expert but if an extra set of eyes can help, let me know. I have to get back out and check my latest build - I had cycling problems on a XM177 so have a couple of different buffers to try (supposed to be nice weather tomorrow!)
Good luck!
Mike

Polecat30,

I'm also in Utah in the Salt Lake area, so feel free to tap into the resources at your disposal. I've been dealing with AR15's/M16's and variants since 1988, and I have many specific armorer-level tools for bolt carrier key work, bolt disassembly, along with the other standard wrenches and punch blocks.

I continue to learn a lot about this system, so I'll never claim I'm a know-it-all, as things I didn't know have been literally sitting under my nose for over 20 years with this design.

I do have an extensive trouble-shooting regimen I go through when working on my guns, or those of friends. Gas system issues are a common problem usually resulting from substandard parts, improper assembly, or improper collection of components. Since JT did your FSB/gas block, I think we can generally rule out improper assembly, and I would bet that he ensured your gas port was a good diameter, and the FSB was properly aligned with the port.

I have seen issues where misaligned gas tubes caused cycling problems, including worn "doughnuts" where the gas tube has a larger diameter at the point of insertion into the carrier key. If that area is worn, the gas curcuit will not be complete, and the weapon short-strokes.

Looking forward to seeing this resolved.

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