458 Socom upper build. I finally committed or should be committed

[osprey]

I have always reloaded and shot 45-70 but also have been intrigued by this AR chambering, so I finally did it. I have parts coming for a 458 Socom upper build. It will consist of an Anderson stripped 458 upper coupled to a stainless Tromix 16.25" barrel with a matched bolt. The rest of the parts will come from my current stockpile as I see fit. I did however order a couple of Tromix modded mags with center feed followers to feed the beast. My intent is for a hunting/critter protection weapon. With the high quality Tromix parts it looks like I will be in it for about $550 or so when done. Anybody else build one of these lately? As always comments and advise is welcome!

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[_torque_spec_]

Mostly seen 10.5" suppressed in 458 socom.

 

[osprey]

I can't say enough about Tromix and their service. Package arrived today from Ok and I just ordered it Wed. Very cheap shipping cost also. The parts look flawless and I can't wait to start assembly. I will try and get some pics up tomorrow.

 

[SpongeRock]

Are you planning on loading your own ammo? If not, where will you get your ammo? I've tried several brands and types and keep coming back to Black Butterfly 300 grain Hornady JHP but dang the stuff ain't cheap!

 

[osprey]

Yes, I will reload, brass and dies already enroute. I will start with bullets I have already for my 45-70. I may buy some controlled fracture projectiles when I get serious about hunting with it. Here are some pics. Note the single groove follower Tony machines for use in the Lancer Mags compared with the stock version. Machine work is top notch on everything.

 

[Member 34319]

I've always liked the idea of a big bore AR. I've had the opportunity to shoot a handful and they are a thump or two. I've never looked into the ability of the cartridge, I figure it wouldn't perform as well as say a rifle projectile?

Those Tromix parts look very high quality.

I have to ask if you heard of 45-70 auto? It's relatively new, but it is designed for the 308 AR platforms, it is basically a 45/70 without its rim.

 

[osprey]

I had not heard of the 45-70 auto, it looks interesting albeit costly. I load my 45-70 only to midrange to slightly hotter and I believe the 458 socom will closely match it ballistically. With today's projectile choices, max velocity is not always required. It will be fun to wring this one out! Here is a mock up of what finished rifle will look like. I used a viltor stripped upper I had laying around just for a look, as the Anderson 458 upper and gas block are still in transit. Second pic with hybrid can attached.

 

[osprey]

She may kick a bit. It will probably come in at 7.5-8# full up depending what optic I use.

 

[titsonritz]

I can't say enough about Tromix and their service. Package arrived today from Ok and I just ordered it Wed. Very cheap shipping cost also. The parts look flawless and I can't wait to start assembly. I will try and get some pics up tomorrow.

Tromix is THE .458 SOCOM manufacturer.

And I love their warranty if you've not read it check it out under the FAQ's.

 

[osprey]

Lol. Here is the Tromix warranty with a slight edit for adult content.

Q: What is the warranty on Tromix parts?
A: If you act like a reasonable adult, there is an unlimited warranty on all parts. However, if you act like an a**hole , there is no warranty.

I really like these guys, my kind of people!

 

[osprey]

The rest of my parts showed up today so I went ahead and built the upper out. All went well with just a couple notes. The finish on the Anderson 458 stripped upper seemed harder and deeper Black than previous Anderson's and it took much longer to lap the front face of the receiver than usual. This is a good thing as I was never too impressed with their finish before. Also a tip to new builders, always have spares of small parts that seem to fly into oblivion never to be seen again. Having spares will save you the grief of waiting for a replacement before being able to finish your build. I managed to launch a gas tube pin into never never land but was saved by a spare. Barrel nut ended up torqued at about 32 ft/lbs with no shims required. I topped it with a strike eagle for its first range session. I can't wait to build some loads this week and maybe shoot it next weekend. I am hoping for a moa thumper.

 

[titsonritz]

Lol. Here is the Tromix warranty with a slight edit for adult content.

Q: What is the warranty on Tromix parts?
A: If you act like a reasonable adult, there is an unlimited warranty on all parts. However, if you act like an a**hole , there is no warranty.

I really like these guys, my kind of people!

I thought you'd like that.

 

[osprey]

Tony Rumore, the owner of Tromix is very approachable and knowledgeable when it comes to big bore AR's. I have been in contact with him regarding projectiles and load data and he has been very helpful. Tromix also offers .375 socom and .450 bushmaster Components and complete uppers. If anybody is on the fence about a big bore AR my experience to this point with Tromix has been very positive. I would usually check headspace on a new build before live fire but being I bought the barrel and bolt from Tromix I feel comfortable it is going to be spot on.

 

[osprey]

Range report: Although I have almost 40 yrs of reloading experience, I approached loading this one with more caution than usual. There is just not enough hard data out there with the various bullets I wanted to try so the first four shots were taken with the weapon strapped into the lead sled and me 20' back pulling the trigger with a string. The four shots were done with four different recipes single loaded with an empty magazine installed to see if action would lock back. All were loaded with new starline brass using cci 350 primers. Results were as follows.

Speer 400gr spfn
33.7 gr AA1680
2.110 COAL
This load ejected and locked action back with no signs of excess pressure.

Acme 500gr rnfp
28.8gr AA1680
2.150 COAL
Ejected and locked back with no excess pressure signs.

Missouri bullet Co. 405gr. Buffalo #1
32.2gr AA160
2.085 COAL
Ejected and locked back with no excess pressure signs.

Maker sub Rex 500gr
13.7gr A2400
2.265 COAL
Did not eject or lock back and no signs of excess pressure.

All rounds exited barrel.

I then shoulder fired all loads at 50 yds from a makeshift bench after bore sighting. All but the Maker 500gr cycled action fine and locked back on empty chamber. The 500gr Maker load did make a half attempt to cycle on one shot but clearly does not develop enough gas pressure to cycle action properly. Accuracy was decent on all loads and all bullets seemed to stabilize properly with no keyholing with the 1-14 twist Tromix barrel. I tried to get some chrono data but I could not get my magneto speed configured properly to read due to a stripped screw head on the base spacer stack.
Overall I was very pleased with the funtion and potential accuracy. I can't wait to get to a proper bench to do some accuracy and chrono testing. The thing is a hoot to shoot!
Disclaimer, these loads were safe in my gun but I cannot recommend them as safe in any other 458 Socom. Use proper caution.

 

[osprey]

I am hoping to get out and move my load developing forward this weekend. I have 3 different bullets to test at various load levels and different powders both super and sub. Center in first pic is 500gr Maker Rex subsonic expanding projectile and yes she is stuffed way the hell in the case. I have my magneto speed configured properly now so some chrono data should be obtained as well.

 

[MDL]

Very nice! Although I did not go with Tromix I used a KAK industry 16 inch barrel and Toolcraft BCG with Anderson arms upper and lower. A nice case gauge from Tromix helps with your reloads and checking out www.458socomforums.com - Index is a plus.
Xcaliber ammo has decent prices. XCaliber Ammunition - Search Results for "458"

On the cheap side shooting Rainier 350grn is fun and decent out to 100 yards but can't go too hot.

 

[edslhead]

Nice lookin rifle! If you haven't already, get the case gauge for the 458's.( like MDL said ) I ruined some brass resizing them too short and the extractor wouldn't reach them. Turned my gun into a jamomatic. I had the same problem with my 375's. Their real finicky on the resizing. Also if you get the COL too long the bullets will hang up on the rifling and the AR doesn't have the spring power to chamber rounds. Was kind of embarrassing at the range having to get out the screwdriver and pry the bolt open Get some melons and do a vid

 

[MDL]

@osprey , Does the AA1680 burn clean? Just been using IMR 4198 and Lil Gun. I am fairly new to reloading...

 

[osprey]

I was keeping the cases separate after last shooting session to examine them later at home. Unfortunately my range bag got jostled on some washboard road on the way down the hill and my brass got all mixed up, so I can't say for sure about 1680. Some cases were fairly dirty and some pretty clean. The action of the AR was not unduly dirty after the session and there were no signs of unburnt powder. I will pay more attention next range session. I have loads with 1680, H110, and AA #9 for this session. Will report back.

 

[osprey]

Nice lookin rifle! If you haven't already, get the case gauge for the 458's.( like MDL said ) I ruined some brass resizing them too short and the extractor wouldn't reach them. Turned my gun into a jamomatic. I had the same problem with my 375's. Their real finicky on the resizing. Also if you get the COL too long the bullets will hang up on the rifling and the AR doesn't have the spring power to chamber rounds. Was kind of embarrassing at the range having to get out the screwdriver and pry the bolt open Get some melons and do a vid

A case gauge would be too easy lol. Now that I have modded the jaws of one of my kinetic bullet pullers to work with the socom case I have been making dummy rounds with each bullet type to check for function in chamber. My sizing seems ok but I have had to adjust seating depths on some bullets based off the dummy rounds.Here is a pic of jaw mod on puller done on my metal lathe.