Pressure .338LM

[schmittchen]

Hello everyone,

I have an RPR .338LM / 2019 and enjoy experimenting with different cartridges. I recently found a website that lists a different pressure of 68,168 psi! According to CIP, the pressure is 60,900 psi.

How do you handle this issue when reloading?

Do you have a middle ground?

Here's the information:

https://www.accurateshooter.com/cartridge-guides/300-lapua-magnum-cartridge-guide/

Greetings from Switzerland

 

[ShaunBrady]

The link is for the 30/338 Lapua and 300 Lapua, not the 338 Lapua.

If you don't have pressure testing equipment, you're left with traditional reloading pressure signs for guidance. CIP/SAAMI contain wide enough margins to allow safe operation with worst case conditions on both the gun and ammo. Those conditions would produce pressures significantly above the rating.

Lapua manufactured 338 Lapua brass won't show ejector marks until past 70,000 psi.

The RPR is a 3 lug 1.125" tenon action well suited for the 338 Lapua. My experience with the factory barrels is that they do not produce the pressures and velocities of a match barrel. Match barrels are used as test barrels to develop factory ammo. Frequently, that ammo produces significantly lower velocities in factory barrels like the RPRs. You'll find numerous YouTube videos screaming about deceptive ammo advertising. In many cases, the velocity difference comes from the barrel, not the ammo. As a reloader, that isn't a problem. With the Ruger barrel, you may need to run higher charge weights to match reloading manual velocities. The ideal powder may be 1 step faster than what the test barrel data indicates. The velocity is the strongest indicator of pressure in the absence of actual pressure measurements.

I had good luck with Lapua brass, 215M primers and H1000 in both magazine length 285 ELDm and single loaded 5 thou jammed 300 ATips.

I have 2 of those rifles. One is now a 300 Lapua. The other is a 33XC.

 

[schmittchen]

Hello,

Thank you for your explanations; I guess I was a bit off. I also reload my own ammunition and have ordered a Garmin to measure the velocity myself. Currently, I'm using Lapua cases with
Lapua 300gr GB528 / 89gr RS 76

and Lapua 250gr GB488 / 94 RS76

I'm always running at 3800 bar / 55100 psi, so I still have some headroom.

I'm writing about a translator, please don't be surprised!

Unfortunately, the barrel is only 26".The cartridge length is 95.5mm and the bullet sits 1.75mm in front of the rifling, so there is still enough room for powder in the case.