6mm Comp Match... Lapua .308 Palma case?

[DP425]

I'm likely going to shoot 6mm Comp Match next season as my primary cartridge in my AXMC. I'll be gathering all my crap to make the switch over through the next few months. Obviously, a big part of that is the brass I'll use. I'm trying to figure out if there would be any advantage to running small primer, Lapua .308 Palma brass. Obviously I'd end up turning necks in the sizing process; not that big of an issue since I've got a 21st century lathe and now neck turn all my precision rifle brass.

The question becomes, is there any advantage to be had running a small rifle primer in the 6mm Competition Match? Theory goes, that small rifle primer pockets handle pressure better... But how do small rifle primers perform vs large rifle with the slower powders used in 6mm Comp Match (H1000, Retumbo, RL-26)? Would this possibly end up a case of chasing better pressure handling at the expense of ignition and burn quality?

 

[Mayday Malone]

Tagged due to my extreme interest in this cartridge.
I've been researching this cartridge for the past few weeks due to the fact my barrel is about to go. Why would you have to turn necks when you neck down to 6mm? I'm guessing the 308 Palma brass thickness in the neck/shoulder junction doesn't jive with 6mm CM chamber dimensions. Also alpha makes 260 brass with a small primer pocket, still new to this but another option can't hurt, lapua's availability of certain types of brass has absolutely sucked in the latter half of 2017, espically 6br. One last question and I'll stop your thread hijack. What gunsmith is chambering you barrel ? Or are you going to have to order your own reamer and send it to your gunsmith due to it being a uncommon chambering?

 

[DP425]

Tagged due to my extreme interest in this cartridge.
I've been researching this cartridge for the past few weeks due to the fact my barrel is about to go. Why would you have to turn necks when you neck down to 6mm? I'm guessing the 308 Palma brass thickness in the neck/shoulder junction doesn't jive with 6mm CM chamber dimensions. Also alpha makes 260 brass with a small primer pocket, still new to this but another option can't hurt, lapua's availability of certain types of brass has absolutely sucked in the latter half of 2017, espically 6br. One last question and I'll stop your thread hijack. What gunsmith is chambering you barrel ? Or are you going to have to order your own reamer and send it to your gunsmith due to it being a uncommon chambering?

Neck thickness will increase considerably going from .30 down to 6mm; of course, it will grow in length too. But, turning necks in general, reduces run-out; neck thickness uniformity is really lacking, even in the best brands of brass. A lot of guys are now running their bushing dies just slightly smaller than final neck dimension, then expanding up to final using a mandrel. This uniforms the inside of the neck vs the outside with a bushing. Just another way to reduce run-out; I prefer turning the necks though. Anyway, yes, the necks would need to be turned due to excessive thickness when sizing down that far.

Good to know on Alpha; I'm trying to stay with Lapua since that's been my brand of choice, but you're right, it's good to have options.

Mile High said they can spin me up a barrel in any caliber I want for my AX, so I'd just planned on having them handle my barrel for me.


I'm surprised no one has chimed in with any input on this small primer issue. Maybe it's just not something to be bothered with?

 

[Hoser]

I have been shooting a 6CM for the past 10-12 years or so.

I mainly use Lapua 243 brass but I occasionally use Winchester 243 brass for lost brass matches.

I have not tried the Palma brass, but I would imagine there would be neck turning involved. That sounds like zero fun.

The reamer that Fritz at Mile High uses is excellent. I have another Bartlien for my AI PSR that I need to send up.

 

[JaredCO]

I have been shooting a 6CM for the past 10-12 years or so.

I mainly use Lapua 243 brass but I occasionally use Winchester 243 brass for lost brass matches.

I have not tried the Palma brass, but I would imagine there would be neck turning involved. That sounds like zero fun.

The reamer that Fritz at Mile High uses is excellent. I have another Bartlien for my AI PSR that I need to send up.

Hoser, I’ve just about had it with my 6xc adventure. Great cartridge but brass headaches have me bummed. I’m seriously considering the 6cm as an alternative. All I want in life is a 115 dtac going a little over 3000fps lol. What dies are you using? I see lri sells some. Is the 4831-h1000 burn rate the place to be?

 

[Hoser]

Hoser, I’ve just about had it with my 6xc adventure. Great cartridge but brass headaches have me bummed. I’m seriously considering the 6cm as an alternative. All I want in life is a 115 dtac going a little over 3000fps lol. What dies are you using? I see lri sells some. Is the 4831-h1000 burn rate the place to be?

I started this game shooting an XC and a Tubb2000 because its what I had when I stopped shooting High Power. My last season in High Power is when I grabbed a CM.

The 6CM will get you there easily with zero pressure and excellent barrel life. I am using H-1000 and Redding 243 Egolf Improved resize dies. I got the dies from Joe Hendricks. I hear the LRI dies are excellent.

 

[whatmeworry_45]

I can vouch for LRI's sizer, very nicely done and worth the coin.

Cant help with the small primer question though, as all I've used so far is Lapua 243 brass, and I still haven't wrung out all the kinks in a load I feel good about. But good Lord, the velocity is there if you want it!

 

[prcomte]

There have been studies done on small primer cases in the 46-51 grain powder weight class. I've asked this question on accurate shooter before, and I've seen the results myself. Small primers have a harder time consistently igniting slow powder especially when you begin putting roughly 50 grains in the case. I've thought about it too, but I quickly talked myself out of it. I have to neck turn my brass in my 6 competition match because its a picky little B****, but that's getting off topic. I run 243 Lapua brass, and if you don't beat the heck out of the brass you'll get ample brass life out of it. Though, if you're dead set on small rifle primers, look at Alpha Munitions brass, they have a small rifle primer 260 case that'd be much easier to neck down to 6mm. You may not even have to turn the necks depending on how consistent they are. If you do this, share the results with us. I'm curious and always open to new ideas. Also, your second question. The LRI dies are TOP NOTCH. These guys know what they are doing. They turn my barrels, and of course I have their die to match. H-1000 is the powder range to be in. H4831 is a little fast, and will eat up the barrel faster than H-1000 will, and if you're not looking to have a crazy muzzle velocity it'll work for you. Hope I've helped a little.

 

[prcomte]

I also have a word document with all the loads I've came up with for mine. If you want it I can email it to you, and you can use it as a starting point. If you want it just PM me your email address and ill send it to you.