Need help with AR-15

[Chiquita]

The rifle is
Aero precision lower and upper,
Krieger 7.5 Wylde heavy, (could be 7.75 don't remember)
Geisele trigger,
Superlative adjustable gas block.
BCG from a previous cheaper build,
shooting Hornady 75grain factory round.

The grouping is within 3/4" to 1".

My first issue is the bolt does not cycle all the way and I have tried to open and close the gas block to no avail.
Besides lower buffer weight and lighter or shorter spring, what troubleshooting would you recommend?

Also, I am sure that quality of the BCG is important. But I don't know how it will help the proper operation and/or help with accuracy. Hence, I have kept the BCG from my low budget build. Please explain why and how the BCG is important.

What BCG would you recommend? and why?

If I am way off base, set me straight.

Thanks.

 

[karrarararararar]

What buffer weight are you currently running? M16 carrier? What exactly isn't the rifle doing? Failure to eject? Failure to lock back? Failure to feed? It's possible the bolt my be moving too fast for proper operation. The first step is to determine if it is indeed short stroking or if it is cycling too fast. Do White Oakes test.

If it is a failure to lock back, are you running a bad lever?

 

[Walt Krafft]

Use a bore scope to check the gas port to gas block alighment. Check the fit of the gas tube to the carrier key. Is either one worn? Are they properly alighned? Have you cleaned and lubed the bcg? Is the tail of the bolt or the hole in the bc worn? Gas rings in good shape? Any gas leakage around the carrier key? Try a different bcg.

 

[tikkaman308]

I would look at the gas hole diameter in the barrel (being a Kreiger it should be big enough) I have had to open the hole diameter up before on more than one barrel for the gun to function properly, but the above suggestions should be addressed as well

 

[Herzo]

What length barrel? What length gas tube? These will determine the appropriate diameter of the gas port. Alignment of gas block is critical, not only radially, but also linear. You may need a spacer to move the gas block towards the muzzle.

 

[Tireguy]

You and I have 2 things in common.....a superlative gas adj gas block and failure to lock back.
For piece of mind I replaced mine with a non-adj gas block and all my issues went away. After monkeying with the adj gas block, the juice was not worth the squeeze.

 

[Jeff Porter]

Swap the BCG with one that you know works in another rifle. That will cover gas key and rings in one test.

Bad Lever or other bolt releases are often problematic without some modification of the spring.

You didn’t mention barrel or gas tube length. 20” / rifle length ? 24” +2” tube ?

I have not found adjustable gas blocks to be necessary on an AR -15.

AR10/LR308/M110… different story.

 

[Rocketvapor]

Shooting a 28" +2 with adjustable gas block, and an H2 buffer, the wife's AR can be adjusted to lock back every shot (slow fire prone) and toss cases about a foot.
Pretty stiff loads for 600 F-Open (85.5 moving 2050fps across the 600yd E-Target) and the case trashing 22 Nosler
Most land in the ammo box lid. Different loads and bullet weight might require a click one way or another.
No one likes shooting next to an AR on a line tossing hot brass across your position
The barrel is from X-Caliber and gas port is larger for use with an adjustable. I think 0.114".

BCA Side charger, with a LWRC 6.8 bolt, 22 Hagar brass resized to 22 NosGar.
Would be 1 MOA if it wasn't for the 9's

 

[whatsupdoc]

1)Make sure the bolt carrier can travel fully to the rear, that there are no mechanical
issues preventing it from full travel.

2)Make sure the gas block is aligned with the port on the barrel.

3)Make sure your gas block is adjusted correctly. Your Superlative gas block
can restrict or it can bleed off. Read and follow the instructions and start with the gas block in the full open position not bleeding off gas.

4)Confirm the size of the gas port in the barrel.

 

[Mark M.]

Most likely, and as already mentioned above, your short cycle issue is the gas block alignment , as far as your BCG question, bolt head spacing plays a sizable role in accuracy, most builds quality builds, like your, would have a bolt that's been matched to the barrel.

 

[SKWERLZ]

Try another known working bolt and carrier.
If tolerances in them isn’t right they leak excessively.

 

[jelenko]

What buffer weight are you currently running? M16 carrier? What exactly isn't the rifle doing? Failure to eject? Failure to lock back? Failure to feed? It's possible the bolt my be moving too fast for proper operation. The first step is to determine if it is indeed short stroking or if it is cycling too fast. Do White Oakes test.

If it is a failure to lock back, are you running a bad lever?

Do the test from White Oak FIRST. It determines whether it's a gas system problem or a lower parts issue.

 

[Forum Boss]

1. Check that the inside of the action is clean and the bolt carrier group has been cleaned from the inside out. Make sure there is clean lube on the contact rails of the bolt carrier.

2. Check for gunk/lube residue and brass shavings in the ejector and extractor recesses. The majority of ARs I’ve seen with cycling problems had this issue.

3. Check the alignment of the gas rings on the bolt. Make sure the rings‘ breaks are in different places, not lined up. Consider the one-piece spiral rings (I know people are skeptical, but these worked great for me and were foolproof).

4. Check for interference of buffer spring. Easy cheap fix sometimes.

 

[SecondsCount]

1. Check that the inside of the action is clean and the bolt carrier group has been cleaned from the inside out. Make sure there is clean lube on the contact rails of the bolt carrier.

2. Check for gunk/lube residue and brass shavings in the ejector and extractor recesses. The majority of ARs I’ve seen with cycling problems had this issue.

3. Check the alignment of the gas rings on the bolt. Make sure the rings‘ breaks are in different places, not lined up. Consider the one-piece spiral rings (I know people are skeptical, but these worked great for me and were foolproof).

4. Check for interference of buffer spring. Easy cheap fix sometimes.

Regarding number 3- Gas ring alignment was a wives tale. It has been proven to not matter.

Forum Boss: Beg to differ regarding #3. Been there, done that, in the field, the real world. Ring alignment DOES matter, based on my extensive experience working on over 70 ARs at public ranges. I worked as an assistant rangemaster and regularly attended to guys who had problems with their black rifles. I definitely saw issues with some ARs when the slots on the rings were lined up. We spun the rings and the problems abated. I also saw more reliable performance on my own ARs with the continuous one-piece rings.

 

[Rocketvapor]

Make the wife happy, stagger the rings just because.

 

[Chiquita]

Thank you all.

I will follow all of your suggestions and get back with updates.

Curiosity question, does it make sense to shorten the spring? Is there a formula on so many coils equals so much weight.

 

[Sandstorm]

What do you mean by the bolt does not cycle. You fire one round and then what happens.
Does it eject, does it not load the second round an go into battery or does it jam, malfunction.
more info needed.

 

[Coyotefurharvester]

1. Check that the inside of the action is clean and the bolt carrier group has been cleaned from the inside out. Make sure there is clean lube on the contact rails of the bolt carrier.

2. Check for gunk/lube residue and brass shavings in the ejector and extractor recesses. The majority of ARs I’ve seen with cycling problems had this issue.

3. Check the alignment of the gas rings on the bolt. Make sure the rings‘ breaks are in different places, not lined up. Consider the one-piece spiral rings (I know people are skeptical, but these worked great for me and were foolproof).

4. Check for interference of buffer spring. Easy cheap fix sometimes.

Have you tried shooting without gas rings, I have and with one,two in place.

 

[Walt Krafft]

Thank you all.

I will follow all of your suggestions and get back with updates.

Curiosity question, does it make sense to shorten the spring? Is there a formula on so many coils equals so much weight.

Don't start chopping on springs until you get the rifle working. A little more info on the rifle would help - barrel length, gas port position.

 

[Derick549]

I am definitely no expert. But I have experience with a failure to lock back issue. Make sure to try different magazines and check the follower for smooth operation.

Shooting across the course. My rifle performed flawlessly shooting 77 MK. But at 600, single feeding 80.5 bergers. I would have a failure to lock back about 30% of the time. After following all of the above suggestions. I also tried different buffers, springs, even powder charges. I ended up replacing the lower and bolt catch/release. And that corrected my issue.

Edited to further explain.

I wanted to replace just the bolt catch/release. My smith and I felt like the catch was flopping around too much. I was also using a magpul clamp on extended bolt release lever. I ordered a phase 5 EBRV3 extended bolt release. It would not work on the 17 designs lower I had. Instead of machining on the lower. We replaced it with an Anderson lower.

Good luck
Derick