6ARC pressure problems

[TxBowHunter409]

Ok, awhile back on a whim I purchased a Howa Mini barreled action in 6ARC. My thinking was, if it didn't shoot good, I'd either have it rebarreled or just write it off as a gamble that didn't pay off. Shot some different factory loads through it once 8 finally got it put together, and as to be expected, it shot like crap. So I stuck it in the corner and just sorta forgot about it for a few months.

Fast forward.. I was digging out a tripod one day from that corner and saw it. Told myself that I really hadn't given that gun a fare shake, because even though I had everything to reload for it, I had never actually tried a hand load to see what it could really do. So I worked up a load test on the gun. Ran down to the range, and the little gun surprised the heck out of me. As recommended by someone on here, I was using LeverEvolution powder and Berger 110 grain Hybrid Target bullets. That day the average group size was like 0.4". Thought that was pretty good for a barreled action with a pencil barrel. But I noticed, I seemed to start showing about midway through my load test. Not bad, just a heavy bolt lift and slight plunger marks. I was using Peterson brass at the time because you couldn't get 6ARC brass in Lapua.

Fast forward a few weeks more. Picked up some Alpha brass, and decided to redo the load test. Met some friends out at the range one evening, and between all the talking it ended up getting dark before I really got to start shooting. Kicked the range lights on so I could see the targets, but it was dark at the bench so visibility was pretty bad. The bolt lift was even worse, but I finished out the load test anyways. Once I got home and could actually check my brass, they looked like they had been put through the ringer. Flattened providers, ejector imprints and all. Brought the gun to my local gunsmith and had him check headspace, even though I had to bring my set of 6ARC headspace gauges for him to do it with. We both confirmed that there's not a headspace issue.

Fast forward again to present. Was listening to a Vortex podcast while driving the other day and the guy on there was talking about his 6ARC and how he was having all sorts of early pressure signs with the gun. Made me think. Then last week I can't across a guy at the range who had a 6ARC with all sorts of pressure issues way to early and with light loads. The common factor is, all 3 guns were Howa Mini's in 6ARC. Now the guy on the Vortex podcast seems to think that the 6ARC doesn't have enough case pressure to fully expand better brass to fire form to the chamber.

So my questions are, has anyone else experienced this with a 6ARC or Howa Mini shooting 6ARC? Do you think swapping out the barrel with a new one would fix it? I hate to drop the money on new barrel, just to end up in the same boat. And since the factory ammo I shot initially, which I am assuming was loaded to gas gun pressure specs, should I just be using gas gun load data for the gun instead of bolt action load data?

 

[1shot]

I'm doing load development on a 6 ARC right now. It's a Kelbly Atlas Lite action with a 24" Bartlien bbl. Using Peterson brass, a max charge of either CFE 223,
A-2520 or 8208 XBR certainly creates enough pressure to form the cases. As you stated, you are getting pressure signs so one would conclude the the pressures are sufficient to form the case. My velocities as recorded on a Garmin are very close to the published data on the Sierra web site.
What is your twist rate?
Have you tried other bullets other than the 110 SMK?
Although I haven't tried Leverlution, there are multiple posts on different forums that it shows similar traits to RL 17, as in going from mild to wild with small increases in charge weight
If you are loading for a bolt rifle, the use the corresponding data. I see no reason to intentionally handicap yourself by down loading.
I would suggest trying one of the powders I have tried as well as some lighter bullets. I'm currently having good success with 95-100 Sierra TMK and 87 Hornady Vmax bullets.
Ultimately, work up your loads, and let the rifle tell you what it likes.
I hope this helps,

Lloyd

 

[WyleWD]

From April through November last year we shot 3 different 6ARC in short range benchrest using 65-70gr bullets out of 12 and 14tw barrels. Alpha and Peterson brass. VERY good accuracy and not one issue with them. LT30, LT32, N133, and 8208 powders, Federal GM Match primers. Alpha brass and Peterson brass shot literally in the same hole, same loads. FWIW. WD

 

[Walt Krafft]

I would start by checking loaded neck clearance and overall case length. You may ve crimping your bullets in the chamber.

 

[FrankG]

Also.... do you know the actual bore and groove size of the barrel? If the bore is tight / even slightly undersize... that will bump pressures more than most will think it can. I've seen plenty of factory barrels under spec.

Later, Frank
Bartlein Barrels

 

[AWS]

Ever thought about backing off a grain or two. I shoot a Mini Howa in 6mm ARC and have no problems with it. Very accurate and great on coyotes. I use AA-2230 in mine with 75gr Speer's.

I can't imagine working up a load to the point your getting ejector marks and staying there let alone introducing different brass without starting over.

 

[jelenko]

First question would be - how much leverevolution?