AR short stroking

jay007

jay007

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St Albert, Alberta
On the weekend at a local 3-gun match, my AR was not cycling in the next round. My first and hopefully correct analysis is the new low pro gas block.

The beginning of the day I ran 10 rounds through it just to test as it had been a while since it was fired, everything went perfectly.

When competition time came,

2 shots, then click, manually rack next round into chamber
4 shots, then click, change mag hoping just a mag issue
3 shots, then click, manually rack next round into chamber
1 shot, then click, manually rack next round into chamber
6 shots, mag empty but bolt not locked back

I then went back to the empty range and tried to run some rounds using my other mags, 2 shots at most then not chambering next round and not locking back when empty.

I am running the same loads as I did before changing the gas block (non-adjustable).

What is weird to me is that it just got continually worse however when I checked the gas block it had not loosened.

I ran 10 rounds of factory through and no issues. I don't want to have to load my rounds hotter as they ran great prior to this and are accurate for this rifle.

My first plan is to thoroughly clean everything , remove and realign the gas block.

I have heard of some people using thread lock on the barrel under their gas block to help seal, I may try this. Oil the hell out of it and give it another go.

Any other thoughts? anything I should try before heading to the range?

clean, realign, oil and try. Maybe take the stock A2 front sight with me to the range and swap it out to try if there's still an issue.

I am pretty green when it comes to diagnosing and working with Ar's.
 
Ensure the gas port and block are in alignment. Is it a free floating Handguard and you have the block touching the ridge/shoulder on the barrel? Their needs to be a gap the width of the Mil spec Handguard end cap. Is the barrel dimpled on the underside of the gas port as this is the alignment indicator? If it worked fine prior to the mod I would troubshoot what was changed.
 
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Check that the Gas Key on top of the Bolt Carrier is tightly secured. The screws ought to be factory staked to ensure that they remain tight, but I have seen them work loose and cause your lack of gas problem.
 
Sqr said:
Ensure the gas port and block are in alignment. Is it a free floating Handguard and you have the block touching the ridge/shoulder on the barrel? Their needs to be a gap the width of the Mil spec Handguard end cap. Is the barrel dimpled on the underside of the gas port as this is the alignment indicator? If it worked fine prior to the mod I would troubshoot what was changed.
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I am going to double check the alignment. It is a factory free float hand-guard and I did have the gas block right up against the shoulder. The barrel is not dimpled.
 
jay007 said:
I am going to double check the alignment. It is a factory free float hand-guard and I did have the gas block right up against the shoulder. The barrel is not dimpled.
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take the block off and measure the distance from the edge of the GB and gas hole. Measure the distance from the barrel shoulder and gas port. Before reinstalling the GB mark the barrel with a sharpie adjacent to the gas port and use it to align the gas tube and gas hole.

Now that you have used the rifle in its current condition you may get lucky as the gas port may have a carbon ring indicating a misalignment.
 
jay007 said:
I just found the specs for the gas block stating to place the gas port hole at .295" from the shoulder, I will measure tonight to see how close (or far) i was to that.
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Most mil spec barrels have the provisions for an end cap which can be measured with a credit card.
 
Most gas block has a way bigget pick up port than a FSB. I have 9 AR, some have the gas block up against the shoulder, some dont. It doesn't affect much of anything.

I would say check your buffer spring. Measure it, make sure its not a rifle spring in a carbine tube, i have had that happen to me once on a then new to me build
 
If it worked before the gas block change I'm going to say it's either gas block out of alignment or lack of lube. Always take a little bottle of oil with you to the range.
 
So I did checked and rechecked the new gas block, it does not need the space between it and the shoulder, I also put a small amount of red thread lock around the gas port prior to reinstalling the gas block and used a better allen wrench to tighten the set screws this time, with lock tite of course. I put more lube throughout than I usually would and 85 rounds at the range yesterday and not one failure.

Hopefully the issue is gone for good!
 
jay007 said:
So I did checked and rechecked the new gas block, it does not need the space between it and the shoulder, I also put a small amount of red thread lock around the gas port prior to reinstalling the gas block and used a better allen wrench to tighten the set screws this time, with lock tite of course. I put more lube throughout than I usually would and 85 rounds at the range yesterday and not one failure.

Hopefully the issue is gone for good!
Click to expand...

Whenever you mess with the gas block and gas tube, ensure the tube isn't binding with the carrier once you have the block and tube set in place.
An easy way to check this is run the carrier into the upper without the bolt (put a little pressure on the underside of the carrier to simulate an inserted mag with ammo). If you feel resistance, you may need to bend or change out your gas tube. While a binding gas tube predominantly affects accuracy in the form of vertical stringing, it may adversely affect function as well.
 
beltfed said:
Whenever you mess with the gas block and gas tube, ensure the tube isn't binding with the carrier once you have the block and tube set in place.
An easy way to check this is run the carrier into the upper without the bolt (put a little pressure on the underside of the carrier to simulate an inserted mag with ammo). If you feel resistance, you may need to bend or change out your gas tube. While a binding gas tube predominantly affects accuracy in the form of vertical stringing, it may adversely affect function as well.
Click to expand...

I will try this!
 
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