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AI .338 LM mags (standard mags) and 250gr 300g?'s

pc3

Sergeant
Full Member
Minuteman
May 26, 2008
775
3
Australia
I am having a .338 LM built on a surgeon XL. Action is here and it will take the standard AI mags not the newer type coming out. Am I better to use the 250gr pills rather than the 300 gr sierra's etc as the heavier 300 gr will have to be seated to deeply (to feed through mag) and reduce powder capaicity to much in comparison to the 250gr pills ?
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

I'm interested also I'm about to have the same problem
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

I've been very happy with the performance of the 250's. The 300's can still be driven to max pressure at mag length, but the weight/velocity differance not worth it for the minor decrease in wind drift you get. I can run 250's at 3000 fps, the 300 only makes 2700, so to me it's just not worth it.

Cory Trapp
Gunsite Academy, Inc.
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

In general I agree with CoryT, but it really depends on the ranges you intend to shoot. While the AI was basically designed around the 250gr bullet and performs very well indeed with it, the reduced wind drift of the 300gr's small advantage becomes significant if you regularly go beyond say 1200 yards in windy conditions. In my experience that is the approximate range where the 300gr really comes into its own. If the great majority of your shooting is inside that, just load the 250gr and be happy. There is of course also single loading the larger ones as needed -- at those ranges mag-fed capability is the least of your concerns. I run 250gr @2950, 300gr@2700 in stock AIAW. If you're starting this project there is always the .338 Norma mag, which will reputedly solve a lot of these issues.
Best,
James
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

.338 Norma Mag sounds good I read abit about it on the other thread. Mu Surgeon XL action however has the lapua case head bolt, I have .50 cases already. I suppose I just want to know if it will still shoot accurately with the 300 gr when mag fed and it seems it will.

Also living in Australia its hard to get anything a bit odd.

I also own a 375/408 IMP and shoot 350's in that (I dont know how to drive it properly yet, hence building 2 smaller rifles for practice one being a 6.5x47) so I could run 250's and be happy, gun will have a 30" barrel as well.

cheers folks
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

Well, at 1500 meters, using Metro Std conditions, I can see only .5 moa differance in wind between a Lapua 250 Scenar at 3000 and a Lapua 300 Scenar at 2700, the Lapua 300 BC is .810.

While every little bit helps, I'm actually looking at running some BoreTech 245's at 3000, they show a BC of .849, that would be 1.1 MOA LESS wind than the 300gr. THAT performance I'll accept single loading, if that's what it comes to. Now if only I could get my delivery of Retumbo...
 
Re: AI .338 LM mags (standard mags) and 250gr 300g?'s

Thnaks folks, I may just run the 250 scenar with only that little diff between the 300gr and 250 scenar it will be less diff with the 300 match King as the BC is less than the 300 gr scenar I guess.