300 BLK cycling problem *INFO UPDATE*

[sscav]

I took my 300 BLK AR out yesterday to do some load testing. These were the first rounds out of this gun.
The gun:
16 Wilson Combat barrel, .106 dia. gas port
Carbine gas setup
Carbine buffer with weights remover and filled with #7 shot. (works very well in 5.56)

The Loads tested:
18.0 gr H110
18.5 gr H110
19.0 gr H110
MK319 130 gr bullet
All loads were shot using a C products 5 round magazine

None of the rounds fired would fully eject. The bolt carrier would come back approx. 3/4 way across the magazine and stop. This was the case using all loads. I had to use the charging handle to finish ejecting the case each time. Next round would chamber and fire without problems, just wouldn't complete the extract/eject cycle.
This rifle was assembled by myself, and I can swap out the magazine and put the factory weights back in the buffer. Also the gas tube looks to be aligned correctly, but I'm going to check. Other than that, I'm at a loss.

The best group was approx. 2 inches at 100 yards, with the 18.5 gr. load, but I'm new to shooting a scoped rifle and the crosshair wobble was really throwing me off. (They look so steady in the movies!)
Any help would be appreciated.

 

[tiNdvenTFHwMdqKW]

Re: 300 BLK cycling problem

I had that problem with my SI-Defense Barrel and I opened up the gas port a hair and it is much more reliable now.

I would double check your gas port alignment with the air compressor technique (stick an unloaded/fired case in the chamber as a plug and then blow compressed air in the other end and listen to the airflow coming out the gas tube while adjusting the position of the gas block) and a make sure it has a nice full flow. You may also want to try a standard Buffer.

Try supporting the rifle on sandbags to get your best groups. It's not really a fair assessment of a gun to shoot off-hand or unsupported - that's an assessment of the shooter.

Disclaimer - I'm no expert just an average shooter.

 

[johnson]

Re: 300 BLK cycling problem

How much does the buffer weigh with #7 shot? Does it do the same with factory ammo?

 

[Jer]

Re: 300 BLK cycling problem

What were your results with the factory buffer/spring? Why are you messing with the buffer on a rifle you haven't fired yet?

 

[rsilvers]

Re: 300 BLK cycling problem

How much does your buffer weigh?

 

[sscav]

Re: 300 BLK cycling problem *INFO UPDATE*

The collapsable stock and buffer was off of another 5.56 AR that I put an A1 stock on. I had it available, so I used it. This buffer setup works in all my other 5.56 guns, no feed or cycling problems noted.
I've never fired factory ammo through the rifle. This round is unheard of here in Vermont, and I've been on the road visiting the kids for Christmas since Thanksgiving, so loading my own has been my best bet. After the holidays settle down, I'll order some.


Ok, the buffer weighs 1452.3 gr. which is 3.319 oz. Not much heaver than the 3oz buffer, but might be just enough. I'll swap the factory weights back and re-shoot. Another thing I'll try is to load 1 round in the mag, charge the rifle then remove the mag before firing to eliminate any magazine influence on the extract/eject cycle.
The gas block is a folding Yankee hill front sight. Again, never had a problem with it before. The gas tube is clear and seems to be aligned correctly.

*****UPDATE******
I was wrong about the buffer. This was the buffer that came with the stock, not one I had modified. When I took the buffer apart to replace the weights I found that there were only about 100 #7 shot pellets in it. The rest of the weight was taken up by a very heavy metal cylinder. Total internal weight was 914.3 grains. I replaced it with 3 standard weights and associated rubber washers, with an internal weight of 824 grains.

I then took the charging handle out of the upper, removed and disassembled the Bolt Carrier Assy. Sliding just the BC in the upper, I found the gas tube dragging in the gas key. Some light tapping on the gas tube and now the BC slides in the upper without resistance.

Additionally, two of the four screws that hold the YHM front sight on weren't even tight. So those were torqued down.
Tomorrow morning I will fire several rounds and test the functions of this rifle. Hopefully, I'll have good news. Sorry to be so long winded, just want to get the info out there and maybe help the next guy.

(As an aside-Mr. Silvers, your 300 BLK website wouldn't register my Yahoo, or Gmail.com addresses, and I never heard back about my Mac.com address. Is there a preferred email host to use so I can register on that site?)

 

[rsilvers]

Re: 300 BLK cycling problem *INFO UPDATE*

mac.com will work, but I don't see anyone recently trying to register with that.