Big bore Build: The winner is...

[stagpanther]

Spent the past couple of years trying to decide if I really wanted to build a "big bore" AR 15--and mostly sat on it since I couldn't decide between 450 bushmaster and the 458 socom.

Things got a little more decisive today when I stumbled upon Obsidian arms web page and couldn't help but notice they have 16" socom barrels made by saturn for about $300--including a matched and headspaced bolt to boot.

Figure this should be REAL interesting.

[precision_shooter]

What caliber did you choose?

[stagpanther]

Got the 458 socom--mostly cause I like the fact it has a slight shoulder so presumably gettint the bullet to stay put in the case won't be as much of a deal as it might be in a straight-walled 450 bushmaster.

[FrankenMauser]

Congrats. It's a fun one.

But...
Watch the bolt when you get it together, to make sure everything is operating correctly and that the extractor isn't going to cause stove-pipes that will munch the pricey brass. Most of the posts about the Satern barrels on the 458socom forums are people trying to figure out what's wrong with their bolts and/or extractors.

You could have picked up a Tromix barrel and bolt for the same price. High quality. Great service.

Starline ran some brass recently. Shouldn't be too difficult to obtain. (Not like it was 3-5 years ago, with 2-year backorders. )

CH-4D dies are said to be the best for the cartridge.
Redding and Hornady get high marks.
No one seems to like the RCBS version (might even be discontinued now).
Nor are the Lee dies well-liked (always very, very rough, the PTE expander eats case mouths, and a few people have stripped the threads right off the adjuster in the seater die, due to the crazy neck tension that new brass has).

[stagpanther]

Thanks for that Franken--I guess I should have researched it a bit more thoroughly. Do you have an links that you think i should look at it?

[FrankenMauser]

Nah. Nothing really bad. Just watch the extractor. If it runs correctly in dummy testing and initial live-fire, you should be golden.
They seem to be good barrels (using Teppo-approved reamers) that just get paired with bolts that occasionally have QC issues and bad geometry on the extractor.

The 458socom forums can be quite helpful, though. Lots of knowledge. All kinds of load data (but hard to sift through). Small number of members. (A few with large egos and unbelievable brand loyalty. You'll spot them quickly. )
I think you still have to send an email to get approved to register, but it isn't too difficult. Read the stickies, they change the process once in a while.
But be warned: Spend some time there, and you'll want to play with some of the .458 SOCOM wildcats. The .375 SOCOM, in particular, is an amazing performer (at least in discussions and on paper -- I haven't drunk the Koolaid).

[stagpanther]

I've actually eye-balled that 375 socom wildcat--liked it alot because it seems the 375 has more "real" pointy ogive bullets than 458--but I like the idea the 458 has been out for a while and already gone through "teething" issues.

I have a wide range of sprinco power springs for the extractor if that ends up being an issue--I've also seen "overpowered" ejectors on bolts sometimes flip a case so hard during extraction that it jams inside the upper. I can't remember who makes it--but I ended up ordering a "slab-side" big bore upper (no assist or port cover). Thanks for the pointers.

[FrankenMauser]

As I've mentioned before, I went with a MEGA SBU upper, paired with a YM National Match side-charger BCG for the initial incarnation of my .458 SOCOM.
But... too heavy, and I really didn't need it to be side-charging.

Tore it apart, used files and sanding drums on a rotary tool to open the port on a blem PSA upper, blended the feed ramp**, put the upper together with a standard 'full auto' BCG, and haven't' looked back.

** I forgot to mention the feed ramp before. Feeding is smoother if you blend the feed ramp to the barrel extension; since the barrel extension should have a larger cut on the bottom to let the fat bullets and cases ride straight down the middle. There's an image showing a blended receiver at the top of the Tromix .458 SOCOM parts page.

[stagpanther]

Yeah--saw the "single slide ramp" on the upper and already have a plan to dremel it in--I'm pretty sure the upper I have on the way has simple M4's--no biggie--easy to do. I've started looking at load info--is lil' gun the acknowledged top powder? I use it alot in my 44 mag loads--along with H110 and win296 as well as 4227.

[stagpanther]

Congrats. It's a fun one.

But...
Watch the bolt when you get it together, to make sure everything is operating correctly and that the extractor isn't going to cause stove-pipes that will munch the pricey brass. Most of the posts about the Satern barrels on the 458socom forums are people trying to figure out what's wrong with their bolts and/or extractors.

You could have picked up a Tromix barrel and bolt for the same price. High quality. Great service.

The barrel and bolt from Obsidian came in today--well in advance of the rest of the parts--that's a big change!

The barrel looks outstanding to me, and Obsidian's 45 colossus brake looks like a perfect match, has a unique collar which fits over the barrel and has a lock screw--the only thing I worry about that is if the screw crushes the threads on the muzzle--we'll see. Notably, the extension ramps are machined into one broad ramp instead of the two M-4's--which is to be expected, but it looks like to me saturn "went the extra mile" by not only putting a nice radius on the breech chamber opening, but the breech face itself is sloped in towards the chamber opening. What a great idea!

The bolt, however, is another story--and I can see why that it may be causing issues. As far as I can tell it's nothing more than a 5.56 bolt with the bolt face reamed out to accommodate the "big sausage" 458 socom case; those walls are paper thin and scream "begging for trouble."

We'll see what happens when I get the thing assembled in a week or so after the rest of the parts come in.

[FrankenMauser]

Interesting.
I wouldn't mind seeing some photos of the bolt, chamber face, and barrel extension, if you get a chance.

[stagpanther]

On their way.

[stagpanther]

Extension:


bolt:

[FrankenMauser]

Thanks.
Doesn't look bad at all.

Bolt looks good.

The lower, middle locking lug looks a bit thin on the barrel extension, but I'm sure there's more meat there than it appears. Probably shadows and lighting making things look funky. Looks like the .458 SOCOM barrel makers finally figured out that they shouldn't mill away the entire locking lug (not a joke -- several companies milled the middle one away, entirely, and severely reduced the width of the adjacent lugs).

I think it'll run well for you.

Thanks again for the photos.


Waiting on the rest of the Lego set to come in is always torture...

[rickyrick]

That's a big hole!

[stagpanther]

That's a big hole!

Indeed--none of my regular jags go through with any notable resistance--thinking of trying my blackpowder cleaning rod.

[FrankenMauser]

I use a 20 ga bore swab for the chamber.

[gshayd]

Young manufacturing makes the bolts for the .458 SOCOM that are thicker.

[stagpanther]

Young manufacturing makes the bolts for the .458 SOCOM that are thicker.

thanks--I'll take a look. Do they have to be matched to a particular extension?

[stagpanther]

Slab-side "big bore" upper from Cross Machine Tool came in this morning.



Appears to be pretty well made, but two "issues" right off the bat; the barrel extension is quite loose in the collar--given a choice between too tight or too loose--I'll always opt for too tight.

The other thing is that the M4 ramp cut-outs do not seem to take into account the single ramp cut-out on the extension. As you can see on the picture below, there is no sense in further working the cut-outs on the upper--all they do is create a "trip ledge" for the bullet or case to hang up on. I'm wondering if it would not be better in fact to fill the receiver cut-outs in altogether with some kind of high-temp epoxy. Or maybe would it be better to just simply look for another upper with no cut-outs at all--and just open the ejection port myself?



BTW Franken--I took a much closer look at the bottom extension lugs and you are right--they have most of their depth cut away in the process of making the single ramp.

I have a bad feeling about these combinations even before putting them together.

[FrankenMauser]

Eewwww.

That's a nasty combination.
I wouldn't like that either.

I really don't like that barrel extension, now. I didn't notice that the feed ramp wasn't milled lower than the diameter of the extension. Quite a few guys have had major feeding issues with feed ramps like that. Those that get them to work usually have to run only pointy bullets like the Hornady FTX or Barnes TTSX.

Why do companies always have to try to reinvent the wheel?...
Man, that sucks.
What a headache.

The options that I would consider, if it were my stuff (in no particular order):
1. Throw a barrel nut on there and blend the feed ramp all at once - barrel extension and receiver - using the M4 cuts and Tromix photo as a guide (not that the Tromix photo is the best -- there just aren't many out there).

2. Find an upper without M4 cuts, open the ejection port, and see if it will run. (Drawings/dimensions online. Take most of the meat out of the bottom, and only what you have to on top. Carefully done on a good upper, the dust cover will still latch closed.)

3. Fill in the M4 cuts and see if it will run.

4. See if you can return the barrel and bolt to Obsidian, and replace them with parts from a Teppo Jutsu approved maker* (Rock River Arms, Southern Ballistic Research [SBR Ammunition], Tromix, SSK Industries, Red Creek Tactical). Tromix is the easiest to obtain, has the best service, and costs the same.


*(Marty from Teppo Jutsu owns the rights to the chamber/reamer dimensions, but didn't claim the ".458 SOCOM" name. As such, companies that don't want to bother asking permission (*cough* PTG *cough*) can just reverse-engineer it, tweak a few things, and slap the same name on their version of the reamer/chamber. Hence, there are "approved" and "unapproved" makers; with several variations of "unapproved" chambers. Because Marty has been off the grid in Southeast Asia for quite some time; it is currently unknown to the rest of us if Satern is approved, unapproved, or somewhere in between.)

[stagpanther]

As if that's not bad enough--the barrel diameter at the port is around .877-not .875 as advertised. I've already scraped the barrel a bit trying to get the .875 block on.

[FrankenMauser]

I'm sorry.


If it makes the headache feel any better...
For the first time in my life, I had to break a stock off of a rifle a few weeks back.
Old mil-surp. Too much rust. Broken stock, anyway. No amount of oil, heat, vibration, or patience was helping the action screws let go.
I finally just bit the bullet, made some careful cuts in the wood to aid in "controlled" breakage, put some support blocks down to further direct the stresses, and smashed it with a 4 lb hammer as precisely as possible.
And once I was in there, almost everything was too far gone, anyway.

[stagpanther]

LOL--that's half the challenge of building your own--scratching your head trying to figure how to make things work that sometimes (often) don't quite measure up to what they're supposed to be. I've never built an AR that was more or less a pistol cartridge--which is what I regard the 458 socom--so this will be a learning experience (like all the others).

Talk about mysteries--I've been watching my parts shipments on line through the various shippers and I'm trying to figure out what the heck is going on--packages initially going the opposite direction of where I live--or sometimes taking a few days to make it towards me--then mysteriously turn around and go back towards the shipper's address, then turn around again and continue on back towards me. Then of course there's USPS--which doesn't even bother listing any progress from one point to the next.

Sorry about your rifle franken--I hope it wasn't a classic; though given your handle I'm guessing it was.

Took apart a brand new boron bolt to clean it out and stone down the extractor and ejector edges tonight--the extractor pin was bent pretty bad

[FrankenMauser]

Wandering shipments are fun.
As recently mentioned elsewhere, I had an AR lower and a Beretta 92 go on Walkabout not long ago. One went to the wrong FFL and then got held up by FedEx for a while before going back to the shipper, and the other got lost in SLC before spending a week's vacation in San Francisco.
It's one thing for something like a UPS "Super Saver Ground" package to take its sweet time, but 2nd-Day Air...?

The broken rifle was nothing special - just a 1916 Spanish Mauser. There are hundreds of thousands of them still out there ... mostly in far better condition, too.