Loading 6.5CM for A Semi Auto

[daved]

After many years of reloading and shooting BA rifles exclusively, I acquired a JP LRP-07 in 6.5CM and need some advice in getting started reloading for it. There are some obvious differences in loading for a BA vs SA rifle, including:

-Optimal powder charge is not determined by chrono data and group - reliable cycling has to be considered.

-The rifle has an adjustable gas block so that is another variable.

-COAL/CBTO are determined to a large extent by mag length so chasing the lands for accuracy seems limited.

-Brass prep will be different – I FL size for bolt guns so that won’t change but I assume a little more bump will be necessary for reliability and maybe more than .002” bullet tension

-Optimal bullet weight may be less than the 140 range that usually yield great results in a bolt gun

-The H4350 I use exclusively for my BA loads may not have the best pressure curve for a SA.

I appreciate any input from on these points, as well any specific loads that have been found to work well in SA rifles.

Thanks,

Dave

 

[BBVDD]

Your adjustable gas block greatly determines your reliability of the rifle.
You set the block to the load.

The main difference between my two guns is that I crimp my gas gun loads but not the BA

I use H4350 in my gas gun with no problems. Again, the gas block is your friend here.

Also, My gas gun likes 140 bergers the best. It shoot around .35" at 100yds with them and 42 grains of h4350

Just my experience

ETA: I load the bullets up as long as possible. Long enough to barely fit in my magazines.

 

[Ledzep]

Load well off the lands and crimp if you can. I tried bushing dies that pushed neck ID as much as .006" under bullet diameter, and without a crimp they sloshed back and forth in the neck (backwards in the magazine from banging around under recoil, and forwards after chambering from inertia) exactly the same as .001-.002" 'neck tension' cases. A crimp stops the sloshing, but too much can hurt accuracy (deforms the bullet and can jack with seating concentricity). If you don't have a crimp and you're anywhere near the lands, a few will touch, a few won't and you'll get really erratic results. With a crimp I'd seat at least .020" off the lands, and without I'd be more like .035-.050.

Don't go down the rabbit hole and lay off your expectations. Guys will claim a lot of sub 1/2 MOA stuff but if you pull up the 6x5 informal competitions here and elsewhere, you'll see that very rarely does the claim pan out. Flimsy barrels with gas systems attached mounted in thin aluminum receivers. If you go into it convinced you'll have a knothole producer, you'll be $300+ into components testing stuff out before you know it. I will accept it if 10 shots are under 1.5 MOA. I stop trying if it's under 1.2 MOA.

I would give H4350 and 140's a shot first because you already load for them, but if the cases get nasty ejector swipes, I'd go 130-136gr and Varget if you can. In any gun, I always try a couple different powders before switching bullets.

*Side note*
Neck tension does not increase past .001-.002 under bullet diameter in the I.D. Neck tension is the elastic hoop stress imparted on the bullet, and the limit of ELASTIC tension can be found by grossly sizing down a neck (.004" under bullet on the ID), then loading a bullet, then pulling the bullet and measuring the ID of the neck. Usually it's about .0005-.0015" under bullet diameter, and that's all that is "holding on to the bullet". Anything extra is just absorbed as heat/work as you PLASTICALLY deform the neck.

 

[Darqusoull13]

After many years of reloading and shooting BA rifles exclusively, I acquired a JP LRP-07 in 6.5CM and need some advice in getting started reloading for it. There are some obvious differences in loading for a BA vs SA rifle, including:

-Optimal powder charge is not determined by chrono data and group - reliable cycling has to be considered.

-The rifle has an adjustable gas block so that is another variable.

-COAL/CBTO are determined to a large extent by mag length so chasing the lands for accuracy seems limited.

-Brass prep will be different – I FL size for bolt guns so that won’t change but I assume a little more bump will be necessary for reliability and maybe more than .002” bullet tension

-Optimal bullet weight may be less than the 140 range that usually yield great results in a bolt gun

-The H4350 I use exclusively for my BA loads may not have the best pressure curve for a SA.

I appreciate any input from on these points, as well any specific loads that have been found to work well in SA rifles.

Thanks,

Dave

I run a pair of JP LRP-07's. This load should run super without having to touch your gas block and it should also be reliable no matter how dirty it gets. Likely wont matter what carrier you have either.

My favorite load:
144 Berger Hybrid
41.5 grains H4350
CCI#200 Primer
Federal Brass
COAL 2.800" to fit in PMAG
Trim to length (1.920" iirc)
Chamfer/Deburr
Annealed in AMP Aztec Code 141
Should be about 2740-50 fps.

Congrats on the rifle! Let us know how it works out

 

[HemiPowrd]

^^^I'm just getting started reloading and have the LRP-07 in 6.5 CM. Do you crimp? If not what amount of neck tension do you use?