My AR15 is choking on certain ammo types - please help

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[ARCHIVED THREAD] - My AR15 is choking on certain ammo types - please help

Posted: 1/6/2014 6:58:02 PM EDT

Hi guys,

Rifle (Delton Sierra 316H) is relatively new. Purchased in August of 2013. Since then, I have shot maybe 500 rounds through it total. This has been brass-cased ammo, with VERY LITTLE Tul/Wolf/MFS etc fired through it, maybe 50-75 rounds total.
Recently I purchased a railed front gas block and a quad rail, and had the local gunsmith install them. Everything else is stock as from the factory. Only other addition has been an EoTech 512 and MBUS rear sight. The rifle originally shot fine for awhile, but now, randomly, it has been choking badly. Now it will ONLY fire 55gr M193. Anything else -- be it Speer Gold Dot 64gr, V-max 55gr, Hornady 75gr TAP, Black HIlls 69gr OTM, Federal Fusion 62gr, or MK318 Mod 0 --- simply will not feed. The rifle will fire fine for 2-3 rounds, then the next round will slam into the feedramp and jam the bolt, stopping it from going forward; instead of the round angling up and into the chamber it just plows right into the ramps and stops. This happens with enough force to cause setback in the non-cannelured rounds and greatly scars/gouges the case neck and ogive of bullet in the cannelured rounds. Racking the charging handle to the rear smartly and then releasing will re-feed the round, and the rifle will fire fine for an additional 4-5 rounds before the EXACT same thing happens.
If you look at the feed ramps, you can see a spot where the finish looks lighter grey than the surrounding areas on both the left and right feed ramps.
So I googled it, and came up with a list of possible issues, which I have addressed as below:

Dirty chamber/feed ramps/barrel extension/bolt carrier/bolt/firing pin channel. I addressed this by stripping the rifle into bolt, firing pin, cam, retaining pin, BCG and upper, then hosing down with Gunslick Foaming Bore Cleanser. I let this sit for 20 minutes then went to town scrubbing everything with a Wheler AR15 upper cleaning kit (upper brush, BCG brush, and chamber 'star' brush). Then I hosed everything down with BC Gun Scrubber. Repeated the above a second time, then lubed and reassembled. Same problem. So probably not related to grit or grime.

BCG and upper too dry. Squirted down everything with CLP until a visible sheen was present on all moving parts of the upper, and reassembled. Still no dice, same exact issue.

Magazine sitting too low in mag well. To address this, I disassembled into upper and lower, depressed the mag release button fully with the tip of an M855 round, and tried various positions on the mag catch screw; threads flush, threads protruding, threads recessed. Still the same issue

Burrs on the feed ramp. I haven't actually tried sanding yet, but isn't 500 rounds a pretty strange time for burrs to pop up?

That's it, I'm out of ideas. Del-Ton has offered to inspect and repair it for me, but I'd like to not be without my rifle if it's possible there's a home-fix. Any thoughts, guys? Anyone with similar issues?

Thanks
DTG

Posted: 1/6/2014 7:02:20 PM EDT

[#1]

Magazine sitting too low in magwel. Sounds out of spec man. Have you tried other mags of a different brand? If those dont work Send her in and let them replace what needs replacing and be grateful you are dealing with a company that cares enough to take care of it for you. Could also be multiple problems and tolerance stacking. Really weird that it worked before though.

Posted: 1/6/2014 7:03:43 PM EDT

[#2]

Yeah, I know right? Worked fine for awhile and now this. Why all of a sudden, ya know? Least they're going to send me a pre-paid UPS shipping label and check it for me.

Posted: 1/6/2014 7:04:27 PM EDT

[#3]

Also, I have a Bushmaster 30 round GI aluminum mag, and 10, 20, and 30 rounder Pmags from G2 and G3, all worked initially but are now causing issues.

Posted: 1/7/2014 1:14:53 AM EDT

[#4]

The only done to the gun that would affect it's operation is changing the gas block.

So, I'm guessing the the gas block was incorrectly positioned, or it's loose and leaking gas, either mistake will leave the gun undergassed, and could cause the problem that you're reporting.

You might also check the gas key on the bolt carrier to see if the screws are coming loose.

Posted: 1/7/2014 10:14:08 AM EDT

[#5]

Do you have the problem with multiple magazines? Could be you just bent a feed lip or something on one.

Posted: 1/7/2014 10:57:40 AM EDT

[#6]

No it's with multiple mags - Bushy and Colt aluminum, Pmag 10,20,30 and a Troy. Also it chokes when I try to hand cycle it as well.

Posted: 1/7/2014 11:03:06 AM EDT

[#7]

Quote History

Quoted:
The only done to the gun that would affect it's operation is changing the gas block.

So, I'm guessing the the gas block was incorrectly positioned, or it's loose and leaking gas, either mistake will leave the gun undergassed, and could cause the problem that you're reporting.

You might also check the gas key on the bolt carrier to see if the screws are coming loose.

View Quote

+1

Posted: 1/7/2014 1:48:12 PM EDT

[#8]

I suppose I need to clarify here: this problem has been encountered after addressing numbers 1-4, and while hand-cycling rounds at home.
Gas carrier screws are staked in and not loose.

If anyone uses P-mags here, can you please disassemble your rifle in upper and lower, and post a picture of the magazine inserted into the magwell? On the top of the pmags, there's a cartridge outline and 5.56 x 45 stamped inside the outine. I can only see about 1/2-2/3 of this detail when a mag is inserted into my magwell. Makes me think my mags are sitting too low?

Posted: 1/7/2014 2:01:24 PM EDT

[#9]

Did the problem start when the rifle was new, or after you had someone put parts on it.

Posted: 1/7/2014 4:09:53 PM EDT

[#10]

Quote History

Quoted:
Did the problem start when the rifle was new, or after you had someone put parts on it.

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"Recently I purchased a railed front gas block and a quad rail, and had the local gunsmith install them."

Posted: 1/7/2014 4:23:12 PM EDT

[#11]

Here is a shot of mine with a 10 round P mag inserted. I have no feed issues.

http://farm4.staticflickr.com/3782/11828951706_ef29c69ef7_b.jpg

Posted: 1/7/2014 4:27:38 PM EDT

[#12]

Quote History

Quoted:

+1

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Quote History

Quoted:

Quoted:
The only done to the gun that would affect it's operation is changing the gas block.

So, I'm guessing the the gas block was incorrectly positioned, or it's loose and leaking gas, either mistake will leave the gun undergassed, and could cause the problem that you're reporting.

You might also check the gas key on the bolt carrier to see if the screws are coming loose.

+1

+ 1000
Something was not done correctly, or the gas block is screwby.

Posted: 1/7/2014 4:33:17 PM EDT

[#13]

Quote History

Quoted:

"Recently I purchased a railed front gas block and a quad rail, and had the local gunsmith install them."

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Quote History

Quoted:

Quoted:
Did the problem start when the rifle was new, or after you had someone put parts on it.

"Recently I purchased a railed front gas block and a quad rail, and had the local gunsmith install them."

Yep, I read that. OP needs to acknowledge when the issue started.

Posted: 1/7/2014 7:56:15 PM EDT

[#14]

It was after he installed it. But it still happens even when hand-cycling rounds, so I don't think it's related to gas not being directed where it needs to go. I could very well be wrong thio

Posted: 1/7/2014 8:04:20 PM EDT

[#15]

If the problems started after the new gas block was installed I would point the finger at the gas block...is the gas block pinned or use screws?

Posted: 1/7/2014 8:56:23 PM EDT

[#16]

Quote History

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It was after he installed it. But it still happens even when hand-cycling rounds, so I don't think it's related to gas not being directed where it needs to go. I could very well be wrong thio

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Fist please don't cycle live rounds inside. Use dummy rounds. Are you riding the bolt home when hand cycling? How do the feed ramps look? Pictures would help us

Posted: 1/8/2014 5:53:54 AM EDT

[#17]

Good point Cory. I will use dummy rounds.
Also no, I am racking the handle fully to the rear and then releasing it to let it snap forward; the jams also occur when trying to use the bolt release tab.
Small thumbnails below. Click to see larger version at image shack, then click that version to get full-size. My camera sucks, best I can do for right now.
Yes, there are the remnants of a "bubba-ed up" desert camo paint job that I am in the process of removing.
The first few images show the jam, with the bullet getting lodged in the feedramps. The later photos show how far the bolt goes forward before jamming.

To note, Delton has offered to fix it for free, but I don't wanna be without it for the 15 business days (5 to ship each way, from NM to NC, then 4-5 to get fixed). Maybe I should just say screw it, buy the OD Green M400 Enhanced that's tempting at Wally World, let Delton fix it, then sell it off?

Posted: 1/8/2014 7:29:48 AM EDT

[#18]

Load 1 round in a magazine and fire it. If the bolt locks back, then you should have enough gas to cycle the weapon properly.

Do you (or a friend) have another AR? If so, try swapping BCGs and see if your rifle functions properly; if so, you have a faulty BCG somehow. Also, try a different upper on your lower and see if the weapon cycles.

Who was this "gunsmith" that installed your rail? If your rifle worked fine before and malfunctions now, then something got duffed. My suspicions would be:

+Misaligned gas block unless the smith installed a pinned low-pro GB (kinda rare)...Food for thought: you could have shaved your front sight and just re-pinned that back on & not have to worry about alignment.

Or, if the smith was a real gump / not familiar with ARs at all / didn't use proper tools they could have bent your upper or the pin holes so that things aren't aligned now.

Posted: 1/8/2014 8:02:34 AM EDT

[#19]

One round does fire fine, though it jams on the feed ramp and requires me to re-rack the handle. However, the bolt does in fact lock to the rear after the shot.
I unfortunately do not have another rifle, and my friends are mainly handgun people; the one friend I know who owns an AR15 lives 2 hrs away.

Posted: 1/8/2014 4:33:23 PM EDT

[#20]

So it's not feeding properly from what I got out of all of that.

Is it possible the gunsmith didn't torque the barrel nut properly and the rounds are getting cought on the feed ramps on the way in because the barrel walked very slightly outward? Or the opposite if way over torqued ??

If this is the case it will explain why it happens cycling by hand

Posted: 1/8/2014 5:49:04 PM EDT

[#21]

I'm guessing the the gas block was incorrectly positioned.

Posted: 1/8/2014 6:03:11 PM EDT

[#22]

Quote History

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I'm guessing the the gas block was incorrectly positioned.http://goo.gl/FD5Gqx

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Only reason I'm thinking it may not be the gas block is because he said it does it when operating by hand as well, not even live fire.

Interested to see what you find

Posted: 1/8/2014 6:06:23 PM EDT

[#23]

Quote History

Quoted:
Good point Cory. I will use dummy rounds.
Also no, I am racking the handle fully to the rear and then releasing it to let it snap forward; the jams also occur when trying to use the bolt release tab.
Small thumbnails below. Click to see larger version at image shack, then click that version to get full-size. My camera sucks, best I can do for right now.
Yes, there are the remnants of a "bubba-ed up" desert camo paint job that I am in the process of removing.
The first few images show the jam, with the bullet getting lodged in the feedramps. The later photos show how far the bolt goes forward before jamming.

To note, Delton has offered to fix it for free, but I don't wanna be without it for the 15 business days (5 to ship each way, from NM to NC, then 4-5 to get fixed). Maybe I should just say screw it, buy the OD Green M400 Enhanced that's tempting at Wally World, let Delton fix it, then sell it off?

<a href="http://img812.imageshack.us/i/2ns1.jpg/" target="_blank">http://img812.imageshack.us/img812/504/2ns1.th.jpg</a>
<a href="http://img203.imageshack.us/i/gu1a.jpg/" target="_blank">http://img203.imageshack.us/img203/5144/gu1a.th.jpg</a>
<a href="http://img716.imageshack.us/i/1ff1.jpg/" target="_blank">http://img716.imageshack.us/img716/3339/1ff1.th.jpg</a>
<a href="http://img89.imageshack.us/i/u4sg.jpg/" target="_blank">http://img89.imageshack.us/img89/2571/u4sg.th.jpg</a>
<a href="http://img7.imageshack.us/i/v8ly.jpg/" target="_blank">http://img7.imageshack.us/img7/1306/v8ly.th.jpg</a>
<a href="http://img10.imageshack.us/i/p3xx.jpg/" target="_blank">http://img10.imageshack.us/img10/254/p3xx.th.jpg</a>
<a href="http://img593.imageshack.us/i/gzfo.jpg/" target="_blank">http://img593.imageshack.us/img593/9718/gzfo.th.jpg</a>
<a href="http://img801.imageshack.us/i/0rmm.jpg/" target="_blank">http://img801.imageshack.us/img801/5936/0rmm.th.jpg</a>
<a href="http://img580.imageshack.us/i/33gq.jpg/" target="_blank">http://img580.imageshack.us/img580/4139/33gq.th.jpg</a>
<a href="http://img845.imageshack.us/i/cdp5.jpg/" target="_blank">http://img845.imageshack.us/img845/1136/cdp5.th.jpg</a>

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We need a picture of this malfunction with a dummy round. This sounds like a bolt over-ride malfunction which is often caused by the bolt not going far enough back. I notice that in your pictures your bolt is not correctly locked to the rear and if released on a round would cause a bolt over-ride malfunction. I am not convinced that you don't have both a gas issue from your gas block and a user issue with relation to charging your rifle correctly.

Posted: 1/8/2014 7:00:00 PM EDT

[#24]

In line with what G MAHN is saying, what kind of a buffer are you using? If it's hydraulic I think I know what the problem is...

Posted: 1/8/2014 7:40:31 PM EDT

[#25]

Also leaning towards gas block not properly aligned with gas hole, causing restriction (low gas pressure)

Posted: 1/8/2014 8:14:23 PM EDT

[#26]

Since you mentioned that this happens without firing and cycling the rounds normally. I had a similar issue, getting stuck on the feed ramps. I replaced the barrel and issue resolved. I could actually get a few rounds through it before it happened and it would happen whether live firing or cycling the rounds and not firing. I cleaned up the feed ramps some, it did help but not enough.

Its possible you have two issues, gas block and something wrong with the barrel. Wouldn't hurt to just double check the gas block first.

Posted: 1/8/2014 8:56:31 PM EDT

[#27]

It's probably all gummed up with spray paint.

Sorry. Couldn't resist.

Posted: 1/8/2014 10:02:22 PM EDT

[#28]

Someone correct me if I'm wrong but this sounds like a gas problem.

Specifically, It sounds like your system is cycling to fast which would make sense that it allows your lower grain ammo to fire but not the higher grains. This is also common in carbine gas systems.

Anyway I would specifically look into your gas system and get a second opinion on whether or not your gas block is installed properly.

Posted: 1/9/2014 7:33:46 AM EDT

[#29]

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It's probably all gummed up with spray paint.

Sorry. Couldn't resist.

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Yeah, you're probably right actually! No idea WTF made me want to do that.....

Posted: 1/9/2014 7:34:47 AM EDT

[#30]

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Since you mentioned that this happens without firing and cycling the rounds normally. I had a similar issue, getting stuck on the feed ramps. I replaced the barrel and issue resolved. I could actually get a few rounds through it before it happened and it would happen whether live firing or cycling the rounds and not firing. I cleaned up the feed ramps some, it did help but not enough.

Its possible you have two issues, gas block and something wrong with the barrel. Wouldn't hurt to just double check the gas block first.

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I wonder if, as others have said, the "smith" at the LGS fucked something up somehow. Regardless, it's on its way back to Delton as we speak --- via FREE UPS Ground, courtesy of Delton --- for warranty repair.

Posted: 1/9/2014 10:52:08 AM EDT

[#31]

I'm going to say the gunsmith probably did not do something right. Also don't be surprised if delton makes you pay after they notice your rifle has been bubba'd with to fix it.

Posted Via AR15.Com Mobile

Posted: 1/9/2014 12:54:44 PM EDT

[#32]

Yeah, I'm not looking forward to that part of it. Lesson learned - NEVER BUBBA-UP your rifle!
Anyways, the hell with the gunsmith, I'll make sure I never take anything back to him.

Meantime....I did go ahead and grab the OD Green M400 Enhanced from Wally World. Had a gift card for $100, so it came to $907 AFTER tax. Hopefully this one will be better --- heard good things about them so far.

Posted: 1/13/2014 12:22:11 PM EDT

[#33]

Rifle arrived to Del-Ton today. Received an email stating their in-house gunsmiths are evaluating the rifle and should have more answers in the next 24-48 hours. I'll keep everyone posted.

Posted: 1/15/2014 9:02:15 AM EDT

[#34]

Not sure if I trust Del-ton or not.

They received the rifle back, and apparently the smiths there shot 30 rounds each of PMC M855, Wolf 55gr FMJ, and Armscorp 55gr FMJ, from three different magazines, without any issues. They then loaded 10 rounds into a 10-round P-mag, and fired the rifle unsupported against the shoulder, and said that they did have issues like what I was originally having. So their answer is that nothing is physically wrong with the weapon, just have to make sure to have it snugged into the shoulder when firing.

Does this sound like a reasonable explanation?

Posted: 1/15/2014 9:16:29 AM EDT

[#35]

Quote History

Quoted:
Not sure if I trust Del-ton or not.

They received the rifle back, and apparently the smiths there shot 30 rounds each of PMC M855, Wolf 55gr FMJ, and Armscorp 55gr FMJ, from three different magazines, without any issues. They then loaded 10 rounds into a 10-round P-mag, and fired the rifle unsupported against the shoulder, and said that they did have issues like what I was originally having. So their answer is that nothing is physically wrong with the weapon, just have to make sure to have it snugged into the shoulder when firing.

Does this sound like a reasonable explanation?

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Yes. That could be a result of low gas flow. Something to do with the bubba job.

Posted: 1/15/2014 9:29:10 AM EDT

[#36]

Ok, but the smith said nothing was physically wrong with the gun? Ideas?

Posted: 1/17/2014 5:59:49 AM EDT

[#37]

Anyone?

Posted: 1/23/2014 12:37:16 PM EDT

[#38]

Update.

Gun received back from del ton today. Continues to choke when hand cycling dummy rounds and on live rounds. Sig m400' doesn't have issues with the same mags or ammo. Bcg from delton works fine in sig but not vice versa. Delton told me it was fixed........obviously it's not.......

Posted: 1/23/2014 3:09:18 PM EDT

[#39]

Edited...VA-gunnut

Posted: 1/28/2014 12:26:25 PM EDT

[#40]

First, when you say "hand cycling" and "racking the charging handle", are you using the bolt release button or riding your bolt forward a little with the charging handle?

If it chokes when the bolt release button releases, then you have a problem - not the other way around.

Racking the charging handle causes the friction between the upper and the charging handle to slow down the momentum of the BCG and will often be enough to cause the round to not feed properly. Add spray paint to that equation and you have a gummed up Upper, Charging Handle and Bolt Carrier Group that slows it down even more. Clean out the upper and charging handle, re-lube both the upper and the charging handle. If hand cycling, release from the rear-most position - Do not ride it forward at all.

Remember that when the weapon cycles, the charging handle doesn't move at all.

The new burrs are potentially caused by the Wolf or other steel jacketed ammo slamming into it repeatedly from hand cycling.

Lastly, your magazine may be part of your issue. Have you inspected it and tried several others with actual firing and not just "hand cycling"? Mags with damaged, bent or out of spec feed lips or misplaced retention holes can cause the problem you are having.

IMO, it is you and your "gunsmith" that are responsible for your gas and cycling issues, not Del Ton. You had a functional rifle until you had your gunsmith change it and you painted it, so I'm not sure that calling out Del Ton for crappy service/products is really appropriate and fair, especially since they have taken it back, inspected and test fired it at their expense.

Posted: 1/28/2014 4:17:42 PM EDT

[#41]

Quote History

Quoted:
Update.

Gun received back from del ton today. Continues to choke when hand cycling dummy rounds and on live rounds. Sig m400' doesn't have issues with the same mags or ammo. Bcg from delton works fine in sig but not vice versa. Delton told me it was fixed........obviously it's not.......

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Replace your gas rings. They are most likely worn since 500 rounds on a new BCG is usually what it takes to smooth the bore. When the rings are too loose, some rifles will choke due to the cam pin dragging along the channel once it encounters resistance from the bolt engaging a fresh round while cycling, thus trying to rotate prematurely. If you swap this BCG into another rifle, I bet the problem follows the BCG and is not gas-related.

Posted: 1/28/2014 5:34:41 PM EDT

[#42]

I'm wondering if the gunsmith somehow boogered up the gas tube somehow. It could cause resistance and slow down carrier velocity enough to cause your issues. Would also explain why the m400 bcg doesnt work in this rifle too.

I guarantee it has something to do with what the gunsmith did.

ETA: Do you notice any marks, burrs, scratches etc on the opening to the gas key for the gas tube?

Posted: 1/28/2014 6:57:26 PM EDT

[#43]

Here is a 30 round PMag Gen2, and my AR feeds rounds without a problem.

Posted: 1/28/2014 10:53:33 PM EDT

[#44]

Quote History

Quoted:

Replace your gas rings. They are most likely worn since 500 rounds on a new BCG is usually what it takes to smooth the bore. When the rings are too loose, some rifles will choke due to the cam pin dragging along the channel once it encounters resistance from the bolt engaging a fresh round while cycling, thus trying to rotate prematurely. If you swap this BCG into another rifle, I bet the problem follows the BCG and is not gas-related.

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Quoted:

Quoted:
Update.

Gun received back from del ton today. Continues to choke when hand cycling dummy rounds and on live rounds. Sig m400' doesn't have issues with the same mags or ammo. Bcg from delton works fine in sig but not vice versa. Delton told me it was fixed........obviously it's not.......

Replace your gas rings. They are most likely worn since 500 rounds on a new BCG is usually what it takes to smooth the bore. When the rings are too loose, some rifles will choke due to the cam pin dragging along the channel once it encounters resistance from the bolt engaging a fresh round while cycling, thus trying to rotate prematurely. If you swap this BCG into another rifle, I bet the problem follows the BCG and is not gas-related.

This is EXACTLY the same thing I was thinking. It sounds like your bolt is not rotating in the carrier the way it is supposed to so it is not where it should be when it strips a round from the magazine and goes to seat the round.

Here is a REALLY easy way to try to fix this. AND CHEAP. Go here, buy this, take the old gas rings off the bolt and install the new ones and see if you are still having the same issue. BCM is good about shipping quick so depending on where you live you should have these relatively quickly. I'm pretty confident this will fix the problem. (Someone let me know if I'm completely off base here). If you think its even plausible that this could fix the problem it is worth the 3 dollars plus 5 dollars or so shipping.

Also, I already saw you're other thread so I'm not going to give you crap about your delton, but it is cutting corners on small parts like these why most of us say companies like del-ton do not make reliable rifles... If this fixes it, do what you said you were gonna do, line up a decent rifle you want, buy it, and sell this thing and be done with it. If they will skimp on something as simple as the gas rings.... who knows where else they're cutting corners.

If you make up your mind to spend 100-1200 on a new AR depending on the deal you can get, you can pick something up where this sort of crap will never happen and if it DOES, it will A) be a freak occurrence, and B) the company will fix it ASAP.

If you decide to try new gas rings, let us know if this fixes the problem or not.

[ARCHIVED THREAD] - My AR15 is choking on certain ammo types - please help

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