So I am building a new 338 Lapua. I am trying to decide on a barrel length. At first I was going to use this as a pure long distance target gun so I had the gunsmith order a 31 inch barrel. now I am thinking I might want to carry this to hunt. Will this cartridge lose a lot of velocity if I cut it from a 30 inch barrel to a 27 inch barrel? Is it worth the velocity/weight difference?

The build is a rock creek barrel, manners 6a stock, Stiller 338 action,seeking bottom metal with detachable magazine,near manufacturing alpha mount, Nightforce AC ATR scope.

Thanks

I only have a little experience when it comes to custom rifles and none with 338. That said...

When I think of awesome high end 338lm's I always think of AW/AM rifles. I think they make some of the finest rifles and in my head they have good knowledge of the caliber. They make their 338's in 27". Must not be a big deal to the,.

Very good angle to take.

Thanks

I've seen them as short as 24 1/2 "

you lose some velocity when shortened,,,,, but with so much energy packed
in that thing I don't think it matters much when you hunt

mine is not a custom but a SAKO TRG 42

All of my 338/378's are 29" barrels. With the slow powders you're running in the 338 Lapua, I expect you'll see probably a 50-75 FPS per inch difference for every inch you gain or lose vs. published data.

Regardless, a 27" barrel will still get you plenty of speed. It wont save you that much weight, but it does improve handling a bit. It wont be quite as unwieldy.

You will lose/gain about 15-20 fps per inch. A 27"-28" will run a 300 grain about 2675 to 2700 fps, which is where you want to be. Barrett has a 20" 338 LM rifle option, and it's a flame thrower. the shortest I'd run is a 26" barrel. The 338 needs barrel length to get the big, heavy bullets up to max speed.

Chad have you seen those kinds of #'s on 338LM's and such? i.e. that small of a gain? The reason I threw out the 50-75 is because that's what I've seen on the 378 based rounds, and it's been pretty consistent especially with super slow powders like 50BMG, 8700, etc. Obviously the numbers will be smaller with the faster powders. Just curious. You're certainly running a lot more volume, reloading wise, than I am.

If you have a fast catridge to begin with, then you will see more of a lose/gain per inch. But in a normal round with general speeds, like a 338 LM, you will see about 20 fps per inch. Your heavy overbore calibers pushing your light, fast bullets will see more of a lose/gain. I don't have any direct velocity, but here are some calculations I ran through QuickLoad. I know my 300 SMK match load runs 2700 in a 26" barrel.

338 LM with 300 grain SMK
28"= 2736 fps
27"= 2716 (20 fps less)
26"= 2694 (22 fps less)
25"= 2670 (24 fps less)
24"= 2646 (24 fps less)
23"= 2619 (27 fps less)
22"= 2591 (28 fps less)

The average is a 24 fps decrease per inch, which should be very close to actual results with this round. Notice how as the barrel gets shorter, the more velocity loss per inch there is. This is realistic, as the barrel gets longer, you have diminishing returns.