Help - Resizing Lapua 308 Win Palma (small primer) brass to 260 Rem for 260 AI

[spclark]

All sounds good Romulus. Sometimes it works better to get close to final forming with the COW (or alternates, like your barrel 'supressors') method then proceed to actual live-fire loads.

Only caveat I have after reading your post is to watch out with the extended hours & long drives. Now that it's dark more than light you don't want to be dozing off behind the wheel....

 

[Romulus]

I've taken the 260 AI Palma for a few spins. The first 3 shots clover leafed at 100 yds using 1/2 grain intervals which was pretty surprising. I had obvious nodes every 200 fps that could be simply stated as centering around 2650, 2850, & 3050). Graphed in Excel the nodes showed up as 3 plateaus with steep rapid climbs to the next node. At least graphically the nodes looked wide/forgiving ;D . My ES testing of two loads across the higher "node" make me feel confident this barrel/ ammo combination does not require a narrow fps band like some combos require.

I began seeing slight ejector marks at 2990 fps out of this 28" barrel, and I finished off the loads that day ending up at 3111 fps with no increase in bolt lift friction or any visual increase in shininess of the flow.

I have not tested lower nodes, but a few days ago I loaded up 20 rounds centered at 3050 and 10 loaded for 2990.

I'm using the cheap RCBS bullet chrono, but it has served me well over the years and when it blows over my heart doesn't drop into my stomach since it's cheap and lightweight. When there's light I've had 100% but when the light runs out it's 0% real quick too lol.

I got ES's of 9 & 13 on the two 10 shot strings at 3050 which is good enough for the purpose of a medium range tactical competition gun. I plan to clean, foul, and repeat using 50 rounds for data to simulate common tactical/practical courses of fire when I get some time off.

On the 2990 load I got an ES of 9 on 10 shots as well. I am tempted to try other powders or push it a little more but there's a 3100 fps speed limit on the club I'd shoot in if I find the time to do so and I'm fine with the 10 shot ES I got. I'm used to shooting 2700-2815 fps out of my 308 and 284 so I'm having fun with this little hot rod.

A lot of times, the oilfield slows down Dec-March so I hope to get some good data collected and put up in case anyone is interested in trying out a 260 AI using Palma brass. Although I have gotten great ES, good accuracy, moderate recoil, and plenty of velocity compared to most tactical comp cartridges I'm still wondering if I will just go 6.5x284 next time. :-\

At any rate, it's fun to play around and do something a little unique.

May you all find plenty of powder, projectiles, and the time to burn them, lol. And thanks for the help offered along the way in terms of brass work.