300blk issue - bolt not going in to battery

[jclayto]

I have run in to an issue with my 300blk loads that has me a bit perplexed. I purchased new to me brass that was cut down from 5.56, trimmed to 1.365". When loading this brass with my standard leather head 220 @ 2.07" OAL the bolt on my ar15 will not go in to battery. Furthermore, the bolt locks up and it is incredibly hard to pull the charging handle back to eject the unfired round.

The leather head 220 @ 2.07" has always worked well in my gun with the only new variable being the brass. Is it possible that the brass is causing this or should I be looking elsewhere for the source of my problem? I will load of some of my other brass that has previously worked as soon as possible.

[mehavey]

1. Did you FL/size the brass before loading ?
2. Did you crimp the cartridge during loading?
3. Did you measure the neck diameter of the loaded cartridge ?


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[RC20]

As you noted, what changed? The Brass.

I have no idea what a Leather head 220 is (bullet?)

It sounds like the bullet is sticking into the lands.

Pull the gun down and check relationships of putting bullets in by hand, how far they go starting with empty.

[jclayto]

I did not prep the brass before loading because it was purchased as fully processed and ready to go. I simply measured to ensure trim length was within spec, lubed and loaded. Leatherhead is a brand of cast and coated bullets that are somewhat popular with blackout shooters and I am shooting the 220 grain variant for subsonic use. I apologize for not clearly specifying that earlier. The rounds are crimped using the Lee factory crimp die.

When I discovered the issue I happened to have a box of my previous loads with me as well as some commercial ammo. My previous loads (same bullet, same OAL, different brass) ran great as well as the commercial.

I size/de-prime on a different toolhead. I will swap heads and run some of this new brass through the FL size and see if that resolves the issue.

[mehavey]

I will swap heads and run some of this new brass through the FL sizer...

That may solve the problem (I always FL/size new brass to ensure uniformity if nothing else.)

BTW, compare your old brass/new brass (loaded) neck/mouth dimension as well. (eliminate/isolate any possible brass neck thickness problem)

[rg1]

Neck diameter of a loaded round should be not more than .334". I highly recommend Hornady's Headspace Gauge Set to measure how much the shoulders have been sized back. Some brands of brass have too thick neck walls and with a .308" bullet may be too large to fit your chambers neck. Or bullets could be oversize? You should see marks on the bullet if it's jamming into the lands.

[Sharkbite]

Sheridan slotted guage will show EXACTLY what is out of spec

[jclayto]

Thanks all! I have been meaning to pick up the slotted gauge. I have heard nothing but good things.

I have some ideas to work through thanks to your comments.

[HankC1]

What head stamp? Certain 223/5.56 brass are known to be too thick and won't chamber when converted into 300 BLK. I purchased converted 300 blk brass at one time and had problem, now I only buy converted from LC brass.
http://www.300blktalk.com/forum/viewtopic.php?t=88599

[disseminator]

What head stamp? Certain 223/5.56 brass are known to be too thick and won't chamber when converted into 300 BLK. I purchased converted 300 blk brass at one time and had problem, now I only buy converted from LC brass.
http://www.300blktalk.com/forum/viewtopic.php?t=88599

I was just gonna post this, not all brass is suitable for conversion. I buy once fired LC brass and cut my own with a jig off amazon. It works 100% so far over 1000 rounds no issues....

[Cavitation]

Time to trim?

[mohr308]

I also had a similar issue with converted brass 5.56 to the .300blk, no matter what I did, it would not chamber. I bought a bag of .300blk brass with zero issues! As a matter of fact I was at the range today! BTW, I'm shooting from a Ruger .300blk bolt action ranch rifle.