Next Up AWB Build- .458 SOCOM SBR


NES Member
Jan 6, 2013
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That 308 M5 was a quick and lazy assembly for me, so I thought about what else have I always wanted to eventually build. The stupid AWB going to the Senate made me decide to get off my ass, get a lower SBR'd, then start on the .458 I always wanted to build. I'd be pretty bummed if I procrastinated too long and had trouble sourcing parts or worse yet... no, not gonna go there.

I already have a .458 rifle and from time to time shoot the tar out of it. I reload Starline brass with 300 JHP's and 4198 powder. This load turns pumpkins basket ball size and smaller literally into sauce. I've mentioned this before, but on a range day with a buddy we shot through the same hole in the target at 50 yards for a couple mags full. When we retrieved the target we saw that we had blown a tunnel over 4 feet through the berm sand and were hitting the railroad ties supporting the back of the berm. Such a fun round and it can be loaded on the cheap once you have enough brass. Absolutely devastating terminal ballistics.

My plans are to go with a Tromix 10.5" barrel and bolt combo so I have the "original" guts. Going to dig through the parts pile and see what lowers I have to SBR. Already completed the fingerprint sheet but need to complete the rest and take a trip to the Mill for the proper markings. I have most everything else I need in the parts pile as well except for possibly a trigger that I really like. Probably will pick up a LaRue for that.

Here's what 300 grains looks like after hitting a 45 degree wet sand berm (shameless repost):


Here are a couple of my typical loads next to what I think was a .223. The JHP's actually run very well and I never have feeding problems.

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I need to get tooled up to reload .458, what bullet are you using? Also any luck with subsonic rounds?
Mostly #4500 Hornady 300 gr JHP. Often I can find them for decent pricing. Haven't bought any in a long time because I stocked up. The tipped FTX or whatever they are cost more and don't really bring anything to the table IMHO. I'm going to try cast, I think 325's if I remember correctly- have not got around to running that mold. I'll use gas checks and hi-tek coating.

I have not tried subsonics yet. Can't have a can in Massachusetts plus subsonics are very heavy which = $$$$$$ to load factory projectiles or will consume a LOT of lead to cast. Might be fun to pop off a few rounds for fun and just to have a load developed, but for me they would be impractical. If I move to a free state I'd get the tax stamp and a can then load up some subsonics.
I've been neglecting my .458's, I have a second build that I haven't even shot. Last loads I made were LeHigh 300gr Match Solid's over 38 grains of CFK BLK, they worked wonderfully but I didn't crono them.
Haven't done any builds in a while so I just got a Tromix barrel/bolt in 450BM, was gonna go 375 SOCOM but there isn't much out there for ammo and parts whereas 450BM is a lot more available.
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