.260 Criterion & Lapua brass problem?

[BoilerUP]

Earlier this week, I shot some loads in my 26" CBI .260 barrel with virgin Lapua brass in what has proven to be fairly mild in Nosler & RP brass...123 A-Max with 39.0-39.6gr Varget. I experienced some decent pressure signs; pancaked primers that looked to slightly be backed out and cratered primers, slight sticky bolt, and light ejector swipes on a couple cases.

Never seen any pressure with these loads using RP or Nosler brass.

Threw this question up over on Sniper's Hide, and a few folks there think I may not have enough clearance in my chamber to use the thicker Lapua brass without neck turning, which is causing this issue.

So...anybody know the chamber dimensions of Criterion's 260 reamer (Jim?) or experienced similar pressure signs in their 260 CBI with unturned Lapua brass?

[keeki]

Thats max load and that thicker brass wont hold as much powder= pressure

[jinx-)]

I use 308 Lapua brass which are neck turned prior to forming and I haven't seen pressure signs you described, but I do not use Varget, my loads quiet mild like 41gr H4350, 43 gr RL-17 and my heaviest load was 45 gr RL-22, plus I only load 139 - 142 gr high BC bullets.

[keeki]

size a piece of the rem, nosler and lapua brass and seat a bullet in each, then measure outside neck.

[snipecatcher]

Thats max load and that thicker brass wont hold as much powder= pressure


I agree with this. It is generally accepted that Lapua brass has less capacity and while it will most likely last longer, you are giving up some capacity. You will need to drop a grain or two and work back up.

[northlander]

Criterion's spec sheet shows the 260 Rem chamber as having a .298 neck.

Jim Briggs
NSS

[BoilerUP]

Criterion's spec sheet shows the 260 Rem chamber as having a .298 neck.

Jim Briggs
NSS


Thanks Jim!

When I measure fired Lapua & Nosler brass on a set of dial calipers, I get a consistent .297.

[ShaneG.]

My 260ai was right at .298" as close as I could measure. I bought some PRVI 7mm-08 brass to neck down and had .288-.289 loaded. R-P 308 brass with no turning is .296 loaded. The PRVI brass shows pressure signs with the same load,43.0g of MR2000 for right at 2880 fps. I would back off or try a slower powder.

[J.Baker]

Reloading 101: Whenever you change a component in your load you need to work through the load development process again.

[BoilerUP]

Again, I've used these loads in both RP and Nosler brass and never experienced any pressure signs. I've seen pressure before from other loads that ultimately proved too hot, but nothing quite like this.

Perhaps I was naive to expect Lapua brass, with its reputation for strength, could handle what seemingly were mild loads in two other types of brass. I reckon I'll reduce a grain and work back up in small increments, and if I still experience similar pressure issues guess I'll be neck-turning them down a thousandth or three.

Thanks for the insight and advice all!

[jinx-)]

you might want to get you boltface bushed to prevent cratering, I think its dishing which is common issue in Savage bolts.

[Wildboarem]

I have a .260 CBI barrel on my Stevens 200 action. Ran into pressure issues on resized .243win, 7mm-08win and .260 rem brass with both h4350 and rl-17 with 140 gr amax bullets. A tight neck chamber is the issue. Now I have to neck turn all my brass PITA. The rem brass seems to have a thinner neck wall wall than the win brass. Win brass seems to be in the 15-16/10000th and the rem is around 13-14/10000th. I turn down to 11-12/10000th. Anything over 14/10000th I see pressure. I'm now rethinking not going with the 260AI, I didn't want the extra brass prep time.

[Jamie]

Again, I've used these loads in both RP and Nosler brass and never experienced any pressure signs.

Perhaps I was naive to expect Lapua brass, with its reputation for strength, could handle what seemingly were mild loads in two other types of brass.

As Mr. Furious stated. If you change a component you start over. Changing from RP or Nosler brass to thicker Lapua brass is a HUGE change, and your gun told you so.

Not sure about how naive you are but Lapua brass is thicker than the RP and Nosler which means it has less case capacity. It does NOT mean that it is a weaker case because you flattened the primer. It just means you did not follow the rule of starting over when you change a component and you created a over pressure round.

[savageboy]

I had the same problem/ issue w/ my 260AI. W rem brass I could use more powder and get 2930is fps (primer pockets were toast after 3 ish reloads and a fireform. When went to Lapua, had to drop back about a grain of powder or so and got great accuracy but lower velocities.

[Browningguy]

As Mr. Boilerup said, it's not the Lapua brass that is the problem, it's the load. I can get an almost unlimited number of reloads out of my Lapua brass in my .243, same can't be said for Winchester/Hornady etc. It's also practically perfect right out of the box, you could probably load it without sizing if needed.

[romulus]

Call me old school, but when a component changes in the system I more or less start over. The exact same charges in different brass take up a different % of volume and different pressures will result.

As a side note Lapua brass is not magical in any way. It is in many accounts more prone to splitting due to its stiffness. People buy it because of the name or to cut down time in making a certain lot of brass consistent. It doesn't matter what name is on the brass you are shooting as long as each piece is dimensionally consistent and consistent in hardness.

[BoilerUP]

Virgin Lapua brass necks measured .290 on my calipers; after running through a Lee FL die they measured .294 and they still measured .294, maybe .295 after a bullet was seated.

Fired 27 rounds today that I ran through the FL die prior to loading, and did not experience any of the pressure signs exhibited in my original post.

[jinx-)]

I did measure my fired brass and I get 0.2976, but that' my resized 308 Lapua brass

[jdg]

Perhaps I was naive to expect Lapua brass, with its reputation for strength, could handle what seemingly were mild loads in two other types of brass.

Brass has no real strength, but relies on the chamber to keep from becoming a grenade. What you are getting with Lapua brass is consistant thickness through out the case, but can only go by word of mouth on that claim!

[BoilerUP]

After a second trip to the range following my initial outing with Lapua brass, it would appear that FL sizing virgin brass before loading has eliminated the odd pressure signs I initially experienced.

Running 130 VLDs @ 2.94" OAL north of 3000fps with RL-17 and virgin FL sized brass and seeing zero pressure signs. Also nice that loads that long still easily fit & feed in the centerfeed blind mag.

I also measured case capacity of virgin FL sized vs. once-fired Lapua brass; 1x brass holds 0.7gr more powder than virgin brass.