338 Lapua Improved

Tyler Kemp

Well-Known Member
Aug 10, 2006
Columbia, MO
I plan on using Retumbo with 300 grain bullets in my 338 Lapua Improved. It is gaining around 12% case capacity, so my loads will need to be upped a lot, but since Lapua cases are so tough I want to make sure I'm running safe loads that have been done before.

What loads of Retumbo are people using with their 338 Lapua Improved or 338 AX, and what speeds are you getting? Any pressure? Have you gone further? Etc...

Tyler, I am running 92.5 gr of H-1000 in my standard 338 LM and I am as hot as I want to be. But I still have room in the case. I am getting 2850 with 300 SMK's, awesome accuracy and low ES. I know that is not what you asked for but I have heard of Retumbo loads in the same area. I do want to say, I have used Retumbo in the past in 2 of my 30-378's and it can go from ok to HOT in just a few grains. So work up slow. You sure don't want to loosen up the headspace on that new rifle.

Hope this helps.

Based on the information I gathered for my 338 LM AI build Hod. US869 is a pretty good choice with the 300 grainers. Supposed to get at or near 3000fps with a 30in tube.

I don't know this as an absolute because mine isn't finished yet but I have a new 8lber and a big box of 300SMK's ready to go when she is. Just in case the US869 doesn't work out I got some RL25 and Retumbo all in the same order.

My biggest issue is going to be the gun will be here before the dies. I kinda screwed the pooch on that one. :(
Tyler - I couldn't find any 338LM Improved data, but I did find this...


I've used Steve's data for some of my rifles and I haven't had any troubles with his max loads.
I am runnung 110gr of US869 with 300gr SMK. It cronoed 3035 out of my 30" barrel.

This is from a post by 'long ranger'. He's built alot of these and routinely gets well past 3K fps with 300SMK and 30" Rock Creek tubes treated with Gun Juice.

"338LAI has 126 gr water capacity, I have found 111.5 gr of US869 works REALLY well and no pressure.
Not sure why it works but it truly does. So far in 1 of my own rifles the original brass has 11 reloading and is still not showing any signs of growth or weakening.
The Edge if memory serves has 115 grains of water capacity and the Edge AI has 127."

See: http://www.longrangehunting.com/forums/f19/anything-between-338-edge-338-am-27830/

Kirby says he typically finds the sweet spot with 300SMK and his 338AX with Retumbo between 100-102g and typically runs between 2900 to 3050 fps or so with 300SMK. I phoned one of his customers lately who is running his load at 102.something Retumbo...so a bit hotter than what Kirby usually uses.

See: http://www.longrangehunting.com/forums/f17/couple-new-rigs-aps-35146/
Thank you very much. I'll start at 98 grains I'll figure and load some up to 103 grains looking for primer flattening. I'd like 3000 fps just because that was my goal, but if accuracy comes first 50 fps won't make a real difference. Once the Bergers come out...ooooh boy! :D
I am in prosess of having a 338 built. Custom action and 28 inch bbl. with break. I would like it in the lapua improved version. I need some advice as to what one. Seems there are many. Is there one better then the rest that would be easyer and faster to get dies for. 300 gr smk's and berger's is my choice. Need to act fast. Barrel on way
Thanks in advance Plott Hound
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