Author Topic: AR15 short stroking  (Read 1485 times)

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Offline manik

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AR15 short stroking
« on: December 27, 2017, 09:42:59 PM »
Hey yíall!! Pretty much an AR Newbie here. Iíve got a PSA complete lower thatís mated to a complete Davidson Defense upper. Standard 16Ē 5.56 NATO M4 contour 1/9 twist using a brand new magpul 30 rnd pmag. It appears to be short cycling from what I can find on the interweb. Running the cheap Tula steel case 55 gr, it will eject, but not load the next round, I believe itís American Eagle 55 gr brass case, it will run, occasionally short stroking and will not hold the bolt open after the last round. I do not know the angle of the ejection, Iím guessing I need to be using at least a 62 grain green tips or heavier. Could someone enlighten me please?


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Online Gilgondorin

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Re: AR15 short stroking
« Reply #1 on: December 27, 2017, 10:40:18 PM »
If this is a home-built AR from various manufacturer parts and pieces, you may be in for a bit of a challenge finding what the problem would be, because any number of the parts/pieces could be out of spec.

Off the top of my head ó I don't have much experience with AR's ó I'd look into checking the buffer weight. A friend of mine's brother was having some of the same problems you're describing while trying to adjust the buffer weight on his AR. You might need something lighter (I'd imagine) than what's currently equipped. The failure to B.H.O. may also be a spec issue, or a mag problem; here too you'll need to experiment with disk calipers and/or different magazines.

If you aren't very experienced with guns the quickest way to fix it might be to just take it to a gun smith for troubleshooting purposes.

Offline mike609

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Re: AR15 short stroking
« Reply #2 on: December 28, 2017, 05:26:40 AM »
Gilgondorin is on the right track. But first try feeding it some good ammo along with a good military spec lubricant like Break Free CLP or Rand CLP. If it runs you are good.  Trying to get it to run crap ammo can cost you more than the savings buying crap. 

First place I would start is a new buffer and buffer spring. PSA has a bad reputation for putting out junk and getting that up to spec will help. If it still doesnít run you may need to dig into the gun possibly spending hundreds of dollars with a smith.


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Offline Ceejmo

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Re: AR15 short stroking
« Reply #3 on: December 28, 2017, 07:36:49 AM »
Is the bolt locking back after the last round?
Could the buffer spring be too strong?
My son changed out his upper from a 5.56 to a 300 and the AR wouldn't cycle properly. He had to order a different strength buffer spring to solve the problem.
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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #4 on: December 28, 2017, 08:38:20 AM »
I have been shooting AR's for a while. I'm not a gunsmith, but I did attend the WECSOG.   :)

Tula is probably the worst of the steel cased ammo. Considered under-powdered by most people.
That being said, I would not own an AR that will not shoot it. It's actually my test ammo after I complete a build.
If the rifle has problems, Tula will highlight them  :thumbsup1:.

If I am reading your post correctly, it sounds like Tula is always short-stroking, but American Eagle works, but still short strokes occasionally.

The weight of the bullet (62gr) should not have anything to do with short stroking. Your rifle should be able to cycle any 5.56 or .223 ammunition, as long as it fits in the magazine without binding.

There are a few things to look at. If you have access to a working AR, and other magazines, that's good.

First thing to do is check the bolt carrier and inside of the upper to see if anything is binding or if the carrier is hitting something other than the buffer.

You should be able to cycle the action easily. If you pull the charging handle back slowly, it should feel smooth.
If you feel things grabbing, you need to look closer.

Pull the carrier out and check for scrapes, scratches, etc. on the bolt, carrier and the buffer, buffer retainer and the buffer tube.

If all that looks good, go back to the range. 

1) Check to make sure the problem persists with other magazines. P-Mags are generally good, but you might have gotten a bad one.
You should have more than 1 magazine anyway.

I would continue to use the Tula since that is consistently not locking the bolt back, try a few different magazines.
Load only 1 round into a mag, shoot it and see if the bolt locks back.
- If other magazines work, you found the problem.

2) Look to see how far the rounds are ejecting. If they are just dropping next to you within a foot or 2, that is a problem.

3) If you have access to a different AR that works, try swapping your lower.
If the short stroking goes away, then you probably need a lighter spring or buffer.

If it continues to short stroke, then its probably the upper, and this is where it gets tricky.

4) You will need to check the gas tube and the gas block to make sure there are no leaks and everything is lined up properly.
Also look for any kinks in the tube that might be restricting the gas flow. You can also pull the gas tube off and check for blockage.
You can probably google youtube videos on how to do this.

5) If nothing is obvious, it could be that the gas port on the barrel is undersized. This will require someone (gunsmith) with the proper tools to gauge the hole, if it's undersized, it can be enlarged.

-or, once you narrow down the problem to the upper,
you could just contact Davidson Defense and they will probably have you send in the upper to be checked.

NOTE:
I am not familiar with Davidson Defense, and unfortunately a quick Google search shows a lot a negative reviews on build quality and customer service.

Hope this helps.

Offline manik

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Re: AR15 short stroking
« Reply #5 on: December 28, 2017, 10:45:11 AM »
I have been shooting AR's for a while. I'm not a gunsmith, but I did attend the WECSOG.   :)

Tula is probably the worst of the steel cased ammo. Considered under-powdered by most people.
That being said, I would not own an AR that will not shoot it. It's actually my test ammo after I complete a build.
If the rifle has problems, Tula will highlight them  :thumbsup1:.

If I am reading your post correctly, it sounds like Tula is always short-stroking, but American Eagle works, but still short strokes occasionally.

The weight of the bullet (62gr) should not have anything to do with short stroking. Your rifle should be able to cycle any 5.56 or .223 ammunition, as long as it fits in the magazine without binding.

There are a few things to look at. If you have access to a working AR, and other magazines, that's good.

First thing to do is check the bolt carrier and inside of the upper to see if anything is binding or if the carrier is hitting something other than the buffer.

You should be able to cycle the action easily. If you pull the charging handle back slowly, it should feel smooth.
If you feel things grabbing, you need to look closer.

Pull the carrier out and check for scrapes, scratches, etc. on the bolt, carrier and the buffer, buffer retainer and the buffer tube.

If all that looks good, go back to the range. 

1) Check to make sure the problem persists with other magazines. P-Mags are generally good, but you might have gotten a bad one.
You should have more than 1 magazine anyway.

I would continue to use the Tula since that is consistently not locking the bolt back, try a few different magazines.
Load only 1 round into a mag, shoot it and see if the bolt locks back.
- If other magazines work, you found the problem.

2) Look to see how far the rounds are ejecting. If they are just dropping next to you within a foot or 2, that is a problem.

3) If you have access to a different AR that works, try swapping your lower.
If the short stroking goes away, then you probably need a lighter spring or buffer.

If it continues to short stroke, then its probably the upper, and this is where it gets tricky.

4) You will need to check the gas tube and the gas block to make sure there are no leaks and everything is lined up properly.
Also look for any kinks in the tube that might be restricting the gas flow. You can also pull the gas tube off and check for blockage.
You can probably google youtube videos on how to do this.

5) If nothing is obvious, it could be that the gas port on the barrel is undersized. This will require someone (gunsmith) with the proper tools to gauge the hole, if it's undersized, it can be enlarged.

-or, once you narrow down the problem to the upper,
you could just contact Davidson Defense and they will probably have you send in the upper to be checked.

NOTE:
I am not familiar with Davidson Defense, and unfortunately a quick Google search shows a lot a negative reviews on build quality and customer service.

Hope this helps.
Johnny, it does. It gives me a place to start anyways. Iíve actually had this lower, bought complete from PSA, and have used two other uppers on it without issue. Both were 556 uppers that friends built and both ran flawlessly. One running a 24Ē barrel that was built for coyote hunting and the other was a 16Ē with carbine length gas system. Iím leaning towards this uppers gas system. When I get a chance, Iíll run some hand loads through it that I have. I appreciate all the information.


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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #6 on: December 28, 2017, 04:47:55 PM »

Offline Shipwreck

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Re: AR15 short stroking
« Reply #7 on: December 28, 2017, 04:49:34 PM »

Offline manik

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Re: AR15 short stroking
« Reply #8 on: December 29, 2017, 07:45:26 PM »
Update. Sitting on my hind end watching the tube and decided to partially disassemble the upper. Found the gas block loose and slightly misaligned. Yet to get out and test it, but, hope thatís the fix.


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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #9 on: December 29, 2017, 09:35:42 PM »
Update. Sitting on my hind end watching the tube and decided to partially disassemble the upper. Found the gas block loose and slightly misaligned. Yet to get out and test it, but, hope thatís the fix.


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I hope that works for you.

Offline Shipwreck

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Re: AR15 short stroking
« Reply #10 on: December 30, 2017, 11:24:15 AM »
Yes, good luck!

Offline manik

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Re: AR15 short stroking
« Reply #11 on: December 30, 2017, 03:54:33 PM »
Well, it would appear that the issue has been resolved. Just ran about 30 rounds of tula through it earlier only had 2 issues and that was the first magazine. First issue, bolt wouldnít hold open on last round and second was a failure to pull the spent round and tried to load one right behind it. All other subsequent shots after that were good, no short stroking and failure for bolt to lock back on last round.
I am going to buy a lot more of the Tula just to make sure that a: the issues resolved and b: pulling the trigger is ALOT of fun!!


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Offline papabear

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Re: AR15 short stroking
« Reply #12 on: December 30, 2017, 04:38:59 PM »
Good read for me. I learned a lot here.
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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #13 on: December 30, 2017, 09:31:15 PM »
Good to see your problems may be cleared up.  :thumbsup1:

I'm not a big fan of steel cased ammo myself,
not because of the steel cases,
but they usually have a bi-metal jacket bullet. (lead core w/steel jacket w/copper coating) which is harder on your barrels.

How much harder is debatable, but I just prefer not to shoot it a lot,
although I still have a few SPAM cans of it that I bought cheap.

Keep in mind that the steel cases do not expand like brass, so there is more powder residue left in the chamber than with brass.
Make sure you have a chamber brush and know how to use it.  :icon_wink:

Don't forget to keep your rifle properly lubed when you head to the range.
Some people like to run their AR's soaking wet, but I have never needed to have them that wet.
-it you get spattered with oil when you shoot, it's way too wet.

I was in the army and just clean and lube it as I was taught.

Offline papabear

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Re: AR15 short stroking
« Reply #14 on: December 31, 2017, 04:52:03 AM »
JohnnyDollar said:

Don't forget to keep your rifle properly lubed when you head to the range.
Some people like to run their AR's soaking wet, but I have never needed to have them that wet.
-it you get spattered with oil when you shoot, it's way too wet.

This was 1/2 my experience before I retired when I was teaching the LTC classes. One of 2 things and both are wrong.
Don't clean them.
Dripping when held barrel down.
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Offline manik

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Re: AR15 short stroking
« Reply #15 on: December 31, 2017, 10:12:07 AM »
Good to see your problems may be cleared up.  :thumbsup1:

I'm not a big fan of steel cased ammo myself,
not because of the steel cases,
but they usually have a bi-metal jacket bullet. (lead core w/steel jacket w/copper coating) which is harder on your barrels.

How much harder is debatable, but I just prefer not to shoot it a lot,
although I still have a few SPAM cans of it that I bought cheap.

Keep in mind that the steel cases do not expand like brass, so there is more powder residue left in the chamber than with brass.
Make sure you have a chamber brush and know how to use it.  :icon_wink:

Don't forget to keep your rifle properly lubed when you head to the range.
Some people like to run their AR's soaking wet, but I have never needed to have them that wet.
-it you get spattered with oil when you shoot, it's way too wet.

I was in the army and just clean and lube it as I was taught.
Great information. Clean and lubed, I absolutely agree. I will need to get a chamber brush. Until then Iíd assume that I could use a brush from the cleaning kit that fits the chamber?
What are yíalls favorite lubes for ARís? I have RemOil on hand that I use on my bolt actions, downside is it doesnít seem to last on semi autos.


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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #16 on: December 31, 2017, 10:28:05 AM »
yeah, lets start a lube war...    :th_thicon_lol:

again,
I was in the army and continue to use Breakfree CLP since that is what we were issued and it works.
For the actual cleaning, I still fall back on Hoppes #9. :)

Pretty much any oil is fine.

Getting the powder residue out of the chamber becomes a problem when switching from steel cased to brass.
Since brass expands better, the buildup of powder residue can cause the brass to get stuck and not eject.

Internet rumors suggest this is due to the lacquer coating on some steel cased ammo melting onto the chamber, but it does not.
Besides, most steel cased ammo is now polymer coated.

Offline manik

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Re: AR15 short stroking
« Reply #17 on: January 05, 2018, 08:47:30 AM »
yeah, lets start a lube war...    :th_thicon_lol:

again,
I was in the army and continue to use Breakfree CLP since that is what we were issued and it works.
For the actual cleaning, I still fall back on Hoppes #9. :)

Pretty much any oil is fine.

Getting the powder residue out of the chamber becomes a problem when switching from steel cased to brass.
Since brass expands better, the buildup of powder residue can cause the brass to get stuck and not eject.

Internet rumors suggest this is due to the lacquer coating on some steel cased ammo melting onto the chamber, but it does not.
Besides, most steel cased ammo is now polymer coated.
Johnny,
Thanks for the information. I use RemOil now as well as hoppes, itís great stuff and what I was taught as a kid to use for cleaning.


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Offline JohnnyDollar

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Re: AR15 short stroking
« Reply #18 on: January 05, 2018, 09:21:17 AM »
Johnny,
Thanks for the information. I use RemOil now as well as hoppes, itís great stuff and what I was taught as a kid to use for cleaning.


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My kid is always looking for a "new and improved" lube.

we have had "discussions"....   smh.
 :th_thicon_lol:

Offline RAEIndustries

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Re: AR15 short stroking
« Reply #19 on: January 09, 2018, 01:16:52 PM »
Welcome to the forum!