I have the 338BR reamer on the way. The AMP is less expensive but after some consideration the BR case is the way I am going to go.

My gunsmith has suggested that he can make a 338/7mmBR chamber by first running a 7mm BR reamer with a 338 pilot, then run in a reamer for a 338-06 to cut the neck them a 338 throat reamer if the throat needs to be deeper (it will for 300 SMKs) Personally don't want a 338/7BR in an AR-15 becasue the magazine won't handle the long bullets and if it won't magazine feed why bother with an AR? It would work in an AR-10 or DPMS LR-308 which already has the right bolt face. If the magzine is too short to load over 240 grain 338 bullets you might as well use the 300-221. With subsonics about all you get with larger diameter bullets of equal weight is lower BC and less range,

Max weitght for available bullets
224 - 90 gn Matchking
264 - 142 gn Matchking
284 - 180 gn Berger VLD
308 - 240 gn Matchking
338 - 300 gn Matchking
375 - 330 gn Lehigh (solid VLD) 350 Wooleigh not VLD
408 - 375 gn Lehigh (solid VLD)
416 - 582 gn Lehigh (solid VLD) 700 gn cast bullets not VLD
500 - 600 gn SPRBT (for 50 Beowulf or 500 S&W stanadard chambers) Not low drag.
510 - 800 gn Barnes solids

If you know of heavier commercially avaialable low drag bullets in each caliber I'd be interested.

Dont forget the MGI lowers that except 308 mags. This along with their 308(high pressure) bolt to be released soon you will have an AR10 in the AR15 package.

Hi Ron,
I only see a interchangable 223 - AK47 magazine on the MGI site. Do you have a link about a stretched AR-15 which can take 308 sized cartridges. That would be great for a 338/7mmBR. There are (were) the Cobb MCRs whcih could do up to 300 Win Mag length

My understanding is they are working out mag issues. Variations in mags & such. Looks like it might be a little longer:mad:

Seems a lot simpler to just go with an LR-308 or AR-10. Both work fine with 308 cartridge length and pressure. It will even handle the 300 Saum 300 WSIM sized cartriges.
For one thing the AR-15 bolt and carrier are too short to cycle a 308 besides being too weak. What's left of an AR-15 modified to 308 which differs from the LR-308? Lots of LR-308 parts interchange with AR-15's. (stocks, grips, triggers,l etc. With decent bc bullets the 338/7BR is a 2.8" (308) length cartridge. With a decent BC bullet the 458 Socom is a 458 Win Mag length cartridge! It jsut wastes their performace capability to use them in short actions.

Louboyd, I have to agree with you. I realy do but the only problem is I dont want or need another AR platform. If I were "mainstream" or "conventional thinking" the ony thing in my safe would be my G30 & my Marlin guide gun in 45-70!

I just finished my 11'brl. Using an 8twist shilen. Just calculating gas port. Running a pistol lenght system. I trim BR the case to an oal of 1.4 & the Hornady 225g Spire point when seated to the grove, 2.255oal drops right into the 6.5Grendel mag. I need to get some 300g 338SMKs & see how they seat in the case. Everything seems to point to this working:smile:

nebie, info on 338 whisper?
 

Can anyone help me with pressures for a 338 whisper?? I have a old 95 C:smile::confused:hilean action and would want to run this baby with 300 grn matchkings for a woods rifle here in pa. These would be set for the subsonic version based on the 7 br. The action is for only 46,000 cup and below.

Thanks for your assistance,

Hatchet

I see no reason it wont work. My load program shows 300g SMK at 1200fps with H110 running 40k cup.