.458 SOCOM anyone?

Ian

Ian

Notorious member
I finally gave in to the dark side and have started collecting stuff to do this. Platform will be an AR-15 and the plan is to shoot powder-coated, soft, monster, hollow-point slugs just below the speed of sound through a suppressor. You see, there's this Mastadon that keeps sneaking over to crap on my lawn....

So, does anyone here have one? I'm looking at Tromix for barrels, thinking about an 8" barrel with perm-attached, ventilated shroud to make it rifle length so I can keep my suppressed OAL short and handy. In an effort to save myself a mistake in barrel length choice I emailed a couple of "the" industry guys and they were helpful with what load data they had for the AR platform but didn't have much information on subsonic cast bullet shooting. I read everything there was to read at the socom forum and it seems that most everyone is trying to use Trail Boss with ~500-grain cast bullets, which puzzles me when I forget that not everyone on the internet gun boards has a lifetime of experimenting with cast bullet shooting under their belt, much less any experience with shooting lead out of a gas-operated automatic. After a lot of experimenting in Quickload I think I understand the dynamics of the pistol-length gas system and based on my various Blackouts and .45 ACP AR I get a general idea of the gas pressure and volume required for correct timing and function, but still it's all an educated guess to me at this point. I'm all ears if y'all have anything to add to the equation.
 
L1A1Rocker

L1A1Rocker

Active Member
One of these days I'll follow and have one of those! Of course, one of these days I'll have a Bridgeport milling machine. . . .
 
Will

Will

Well-Known Member
Ian I have looked at the Rock River upper for almost a year. I really like rock rivers beast.

I usually really want one till I start looking at the $0.80/piece brass.

I have lots of 45/70 molds so a 458 would suit me perfectly. One day I'll take the plunge.
 
Ian

Ian

Notorious member
Midway has brass on sale for .74 each, not out of line with 45/90 WCF and some of the other big-bore rifle calibers. I figure a couple hundred should last me a while.
 
Hawk

Hawk

Well-Known Member
Was at the range the other day and the guy next to me was shooting one.

We had a very interesting conversation about it.

He was shooting full power factor loads. I don't remember the grain bullet, but I think they were Hornadys.

I figured since he was shooting an AR, the recoil wouldn't be too bad. He told me I was wrong and showed me his red (soon to be blue) shoulder to prove it.

I'm not too sensitive to recoil and have always wanted one of these.

I will be watching this thread with interest.
 
Ian

Ian

Notorious member
300 grains at 1800 fps out of a seven pound carbine is a recipe for sore shoulders. Lots of people run an A2 stock with a lead weight in it, and add a slip-on Limbsaver pad on top of that.
 
L1A1Rocker

L1A1Rocker

Active Member
Hawk said:
Was at the range the other day and the guy next to me was shooting one.

We had a very interesting conversation about it.

He was shooting full power factor loads. I don't remember the grain bullet, but I think they were Hornadys.

I figured since he was shooting an AR, the recoil wouldn't be too bad. He told me I was wrong and showed me his red (soon to be blue) shoulder to prove it.

I'm not too sensitive to recoil and have always wanted one of these.

I will be watching this thread with interest.
Click to expand...

A good silencer will soak up a lot of recoil.
 
F

freebullet

Guest
Don't have 1 either. Be inclined to go with the 450 or 45 raptor as I have molds for them.

Still watching with interest though.
 
Ian

Ian

Notorious member
450 has either a 1:20 or 1:24 twist, no good for subsonics. .45 Raptor obviously requires a .308 platform, not that I'm opposed to that, but the bullet length is very limited by the case and throat...unless that part is fixed. I always thought it would be cool to throat the bejeezus out of the Raptor and load magazine-length cartridges and, say, 500-grain bullets. :D Load data would be a bit of a complication though unless there are similar cartridges to use for extrapolation, maybe the .458 Win Mag or others...
 
Ian

Ian

Notorious member
Getting deeper. Picked up a good forged upper, GI barrel nut, and pistol gas tube on sale tonight. Still on the fence with the barrel but the Tromix 10.5 with Lee 500-grainers should work very well with Herco and keep the muzzle pressure in the low 2Ks at 1K fps. At least that's what the numbers say. The 8" barrel drives muzzle pressure WAY up and takes about 5-8K more chamber pressure for the same velocity as a 10.5". Going to a 12 lowers muzzle pressure somewhat but doesn't gain all that much, not worth the trade-off for another 1.5" of barrel length. I think the 10.5" will also do a whole lot better with full-house 300-grain loads than the 8" will, in case I want to play with full-power stuff.

Now I gotta figure out how to ream a .750" GI gas block up to .800" for a forearm plate and barrel extension mount. Oh, and buy a barrel....
 
Ian

Ian

Notorious member
Got a new Lee C457-500-RF mould and cast with it tonight, it's going to be perfect for the SOCOM. Made a dummy cartridge and checked in GI magazines, good to go. Even room for powder coat, I think. Will have to get a case gauge. Looking a little closer at the Tromix 10.5" barrel now, I think there will be room for a low-profile gas block, a fake front sight block in front of that, and a ventilated barrel extension. Time to spend mo' money.
 
Will

Will

Well-Known Member
Ian what made you decide on the tromix? I've looked at them several times but don't know much about them.
I personally have been eyeballing the rock river beast upper.
 
Ian

Ian

Notorious member
Muzzle thread pitch and diameter. Tromix is one of the few if not only ones using standard .30-caliber muzzle threading instead of some kind of non-standard, proprietary pattern (seen at least three other muzzle thread patterns on SOCOM barrels besides 5/8" x 24 tpi). This is important if you run a silencer with proprietary muzzle brake mounts which only come threaded for standard barrels.
 
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waco

waco

Springfield, Oregon
My Lapua brand .338 Lapua brass is $2.80 per case on sale:eek:
300gr bullet @ 2700fps
Granted my rifle weighs 16lbs. It still gets your attention after 10-15 rounds.
 
Ian

Ian

Notorious member
After a phone call and couple of emails, I found out that Tromix makes a faux picatinny gas block for their completed pistol uppers that is bored out to fit the barrel, and they hide a low-profile gas block in the pistol position under the handguard. In the carbine/rifle world I think this is what's called a "diffuser" so you can run a traditional rifle-length handguard on a carbine length barrel and gas system. I want to run an M4 handguard on this rig and this is one way to do it, but the Tromix faux block is aluminum, and I suck at welding aluminum. All of that ate up Friday and I didn't get a barrel ordered, but will do Monday. I did come up with a take-off GI front sight gas block to play with, might see about turning the barrel down to .750" on the front part and just using that for a barrel extension mount.
 
Ian

Ian

Notorious member
10.5" barrel, bolt, low-pro gas block, and Sheridan case gauge are headed my way today :)
 
Ian

Ian

Notorious member
Quickload agrees with your gut. 21.4 ounces of chrome-moly steel is quite a chunk of pipe, but it's a Mastadon killer, what can I say.
 
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