Wolf 6.5 Grendel Split Cases

[JB62]

Yep, I was having issues with my 6.5G as well.

I have 20 inch with rifle length, H1 buffer. Have an adjustable gas block, however had way too open. Went out this weekend and started with it closed, adjusted just to was getting last round hold open. Brass looked perfect and the angry extraction marks are gone.

 

[rmbstyle]

I believe this is the same problem JB62 had in this thread: https://www.mdshooters.com/showthread.php?t=263674

What's happening here is you don't have sufficient dwell time- the pressure inside the casing is still very high when extraction occurs.
Unlike your split steel cases, the brass cases are much more malleable than steel and bulge at the base (where the casing is strongest), the rest of the casing fireforms to the chamber then contracts to a slightly bulged size. Steel is not as malleable and usually doesn't return to its original size so your cases are splitting as they fireform.
Remember- the moment extraction begins and there is still high pressure, the casing WILL expand to whatever the chamber surface is at that point until the pressure drops (i.e casing is 0.05in OOB on extraction, casing will expand to approx that)

Solution(s):
1. Adjustable gas block to increase your dwell time.
This may make your upper ammo-sensitive though if you finely-tune it.
2. Longer barrel with a longer gas system.
6.5x39 is a mid-long range cartridge and tends to work best in 18in barrels with a rifle gas system. Downside here is you will have to make sure your bolt matches the barrel.
2a. Heavier buffer or switch to A5 or rifle buffer.
Carbine buffers are notoriously light, and the H3+ weights get VERY expensive as you go up in weight. A5 and rifle buffers start at 5oz and go even heavier. The downside here is A5 uses proprietary parts and are moderately more expensive than carbine parts, and rifle buffer you lose the collapsing stock and there aren't many options out there for rifle buffers.

Personal opinion: if you know how to install a gas block and muzzle device and like your current setup, this is the cheapest and most-efficient option.

Thanks for all the info!! I'm going to try a heavier buffer and if that doesn't work I'll be trying an adjustable gas block.

 

[lazarus]

Is this kind of case expansion normal?

No. Brass will have more snap back than steel, but a quick check of my brass has between .1mm and .12mm depending on AR vs Howa bolt gun respectively for the brass for the same area.

I’d expect steel to have at most maybe .2mm.

I HAVE had a couple wolf cases split like what you’ve seen. Also wolf and Tula steel in ARs in .223.

But we are taking like maybe 5-6 cases total of 6.5 and .223 combined out of maybe 300 or so of 6.5 steel and 600-800 .223 steel.

Well, maybe not split THAT bad. They formed similar hairline cracks, not SPLITS like those are.

Then again I am running an 18” with mid gas. Of course my Howa doesn’t have extraction under pressure. So I am willing to believe it is an overly energetic gas system, but it still might be an oversized chamber. You’ll likely need to look at an adjustable gas block. A heavier buffer can slow extraction, but it doesn’t make it start any later really. So the case will start extracting almost as soon, it’ll just take longer.

 

[rmbstyle]

Swapped out the buffer spring for a Springco red and replaced the H2 buffer with a H3. Ran 40 rounds through it without a single case split.