Problem with too many AR Projects: do I have .458 socom bolt head?

[RussellC]

Having finished my .458 SOCOM AR, I decided to buy a little factory ammo to try it with once it warms up a little. I have not yet purchased the ammo, or dies, brass and bullets to load any.

Looking over the gun and my various receipts, I see where I ordered a bolt head which receipt shows the 3 flash hiders and muzzle breaks I bought to try, and shows a bolt head for ".223/Grendel."

I know I have thought about an AR in Grendel, and may have bought a bolt head for such purposes.

Problem is, wouldn't that bolt head be the same as .223? I may have just scored another bolt head as extra? I can't find one for a .458 SOCOM, which I recall buying (or thought I was) from Deltateamtactical.com, where all the aforementioned stuff came from.

So, either I have lost the receipt for the .458 bolt head, or inadvertantly checked the wrong box when ordering. Unlikely, I waited for it to come back in stock, but anything is possible.

Don't have any .458 brass to see if it fits in bolt head, I figure if .308 brass fits it, it must be too large for .223/Grendel, right?

Not like me to make such an error, but safety first, particularly with this powerful round. Once I get some .458 brass I can make some dummy rounds for function test, but for now? Particularly if I need to order another. 458 bolt head! (Which again is out of stock at Deltateam)

Russellc

 

[<*(((><]

223/556, 300 Blackout, 277 Wolverine, .204 Ruger, and others: .378"
6.8 SPC, 30 REM AR, .224 Valkyrie: .420"
6.5 Grendel, 7.62x39: .445"
.458 SOCOM, .50 Beowulf, .308 Win, 30-06, .270 etc, 7mm-08: .473"


Those are close bolt face diameters, bolt face depths vary as well between cartridges, do your research.

 

[Varminterror]

a bolt head for ".223/Grendel."

You can rest assured - it's NOT a 223/Grendel bolt. If it measures out at .473", it's a Socom bolt. A Grendel should be a .445" bolt face, NOT a .473".

 

[<*(((><]

Thanks for the clarification @Varminterror, I was going off what I remembered, and forgot the Grendel is different than the 7.62x39. I think everything else in my post is accurate.

 

[adcoch1]

The Grendel and 7.62x39 are the same diameter, the socom is larger. There may be differences in bolt depth depending on chamber design.

 

[Varminterror]

Thanks for the clarification @Varminterror, I was going off what I remembered, and forgot the Grendel is different than the 7.62x39. I think everything else in my post is accurate.

Grendel is NOT different than x39. Type I Grendel bolts are exactly identical to 7.62x39 bolts. Type 2 Grendel bolts are .135” deep bolt face instead of .125”, but are the same .445” rim and nominal boltface.

The 458 Socom uses a .473” rim and nominal boltface, which is the same as 7.62x51, aka 308win, but is not the same as Grendel or 7.62x39mm.

 

[LoonWulf]

Brownells also stocks .458 socom bolts.

 

[Varminterror]

Brownells also stocks .458 socom bolts.

I bought a pair of 458 carrier groups over Black Friday, as well as a couple 5.56’s and x39’s, on sale plus a $15 card included. Very good quality machining, maybe a little sharp on some edges I would prefer to see radiused or broken before shipment, but overall very nice. Looking forward to trying my damnedest to wear them all out.

 

[RussellC]

So easy for me to figure with measurement, and checking .308 brass for fit.....would never go with .223 bolt head.

Yes, Brownells has an excellent bolt carrier assembly for .458 SOCOM, but I had a few sitting around and the bolt alone was available for 50 bucks from Deltateam.

Then time went by, then checking receipts started this inquiry.

Russellc

 

[RussellC]

Grendel is NOT different than x39. Type I Grendel bolts are exactly identical to 7.62x39 bolts. Type 2 Grendel bolts are .135” deep bolt face instead of .125”, but are the same .445” rim and nominal boltface.

The 458 Socom uses a .473” rim and nominal boltface, which is the same as 7.62x51, aka 308win

As I thought, (Re: .308 Win.) thanks for making that clear.

Russellc

 

[RussellC]

Well, here's the punch line, I really dont know what I've got! The receipt I THOUGHT went with it says 6.8/.224 Valkyrie! Two things, I had been thinking about a .224 Valkyrie back when I ordered the parts, so no doubt may have bought one....I thought I ended that thought pattern with "someday build the 6.5 Grendel instead, but just finish the .458 for now" Using my micrometer, a quick measurement was .445" but if I jimmied around a little one measurement was .450....which may have been inaccurate. I see .445 IS in fact correct for 6.5 Grendel, so either I misordered, or I need to search through all my stuff and see if there is a .458 SOCOM bolt in there, and maybe a .224 valkyrie? Too many projects. Only thing I am sure of is that I have a receipt for a "6.8/.224 Valkyrie."

Thanks for the info,

Russellc

 

[RussellC]

Checking back on Gunny's "Big bore build" thread, where I was building mine, I must have misordered....I posted when my muzzle brake came and am talking like it was done....looks like I need either a bolt or complete carrier. If complete carrier, I will do Brownell. If Deltateamtactical gets the bolt shortly, I will try one of those. Looks like I have a 6.8/.224 Valkyrie bolt....not really interested in that caliber, but it is what it is, and isnt what it isnt!

Russellc

 

[RussellC]

duplicate.

 

[Varminterror]

I’d have to put the calipers to a 6.8 bolt, but .450” sounds like a Grendel/x39 bolt to me - I measured the bf on one of mine earlier. A 6.8spc is slightly smaller, running a .422” rim, to the Grendel’s .445”. .450 would be a lot of clearance...

 

[RussellC]

Well maybe my measuring? I just pulled gun from safe, removed bolt carrier and put the calipers to it, and put gun back up. It could slipped after withdrawal. Not big enough to be for .458 anywho.

Thanks for the help here,

Russellc

 

[RussellC]

Looking at measurements given in post #2,
It can't be what the receipt says, "6.8/.224 Valkyrie" that would be. 420", but this thing is .445"? Oh well.

Russellc

 

[Varminterror]

Not saying everyone cuts the same exact bolt face, but they certainly should be nominally the same. Side by side, measured by pulling vernier calipers apart while wiggling to the point of nearly abrading the finish on each to find max ID.

5.56x45mm = .3870”
6.8mm SPC = .4335”
7.62x39mm = .4600”
458 Socom = .4870”

Notice the ejector on each - the ejectors are bored at the same position relative to center on all of these, and as such, reveal clues about the thickness about the relative rim wall thickness: on the 5.56, the ejector is sunk about 1/4 of the diameter into the wall of the bolt rim, and the wall is obviously very thick. On the 6.8, the ejector is only slightly cut into the rim, the crescent cut is just visible if zooming in on the photo. The x39/Grendel ejector just kisses the rim wall, but the rim isn’t cut to inlet the ejector at all. The 6.8 and Grendel/x39 wall thickness look very similar, but that small crescent cut to relieve the ejector in the 6.8 which isn’t present in the x39 gives away the larger boltface cut, and thinner rim wall. For the big 458soc bolt face, the ejector is removed away from the rim entirely, free standing in the boltface, with an obviously VERY thin rim wall.

So with yours measuring .445”, there’s not enough clearance for a Grendel/x39. More clearance than my 6.8 bolt measured here, but call it a generous 10thou clearance all the way around, to the ~5thou my bolt would have. Maybe they relieved to the edge of the ejector bore?

But at .445”, as we’ve surmised, it sure ain’t a 458socom bolt!

 

[adcoch1]

Not saying everyone cuts the same exact bolt face, but they certainly should be nominally the same. Side by side, measured by pulling vernier calipers apart while wiggling to the point of nearly abrading the finish on each to find max ID.

5.56x45mm = .3870”
6.8mm SPC = .4335”
7.62x39mm = .4600”
458 Socom = .4870”

Notice the ejector on each - the ejectors are bored at the same position relative to center on all of these, and as such, reveal clues about the thickness about the relative rim wall thickness: on the 5.56, the ejector is sunk about 1/4 of the diameter into the wall of the bolt rim, and the wall is obviously very thick. On the 6.8, the ejector is only slightly cut into the rim, the crescent cut is just visible if zooming in on the photo. The x39/Grendel ejector just kisses the rim wall, but the rim isn’t cut to inlet the ejector at all. The 6.8 and Grendel/x39 wall thickness look very similar, but that small crescent cut to relieve the ejector in the 6.8 which isn’t present in the x39 gives away the larger boltface cut, and thinner rim wall. For the big 458soc bolt face, the ejector is removed away from the rim entirely, free standing in the boltface, with an obviously VERY thin rim wall.

So with yours measuring .445”, there’s not enough clearance for a Grendel/x39. More clearance than my 6.8 bolt measured here, but call it a generous 10thou clearance all the way around, to the ~5thou my bolt would have. Maybe they relieved to the edge of the ejector bore?

But at .445”, as we’ve surmised, it sure ain’t a 458socom bolt!

Thanks for the visual, you know what they say about a picture worth a thousand words... I was going to do the same but I don't have a 6.8 bolt handy!

 

[RussellC]

Not saying everyone cuts the same exact bolt face, but they certainly should be nominally the same. Side by side, measured by pulling vernier calipers apart while wiggling to the point of nearly abrading the finish on each to find max ID.

5.56x45mm = .3870”
6.8mm SPC = .4335”
7.62x39mm = .4600”
458 Socom = .4870”

Notice the ejector on each - the ejectors are bored at the same position relative to center on all of these, and as such, reveal clues about the thickness about the relative rim wall thickness: on the 5.56, the ejector is sunk about 1/4 of the diameter into the wall of the bolt rim, and the wall is obviously very thick. On the 6.8, the ejector is only slightly cut into the rim, the crescent cut is just visible if zooming in on the photo. The x39/Grendel ejector just kisses the rim wall, but the rim isn’t cut to inlet the ejector at all. The 6.8 and Grendel/x39 wall thickness look very similar, but that small crescent cut to relieve the ejector in the 6.8 which isn’t present in the x39 gives away the larger boltface cut, and thinner rim wall. For the big 458soc bolt face, the ejector is removed away from the rim entirely, free standing in the boltface, with an obviously VERY thin rim wall.

So with yours measuring .445”, there’s not enough clearance for a Grendel/x39. More clearance than my 6.8 bolt measured here, but call it a generous 10thou clearance all the way around, to the ~5thou my bolt would have. Maybe they relieved to the edge of the ejector bore?

But at .445”, as we’ve surmised, it sure ain’t a 458socom bolt!

Nice info....I will do a more accurate measurement of mine, but yes, it is clearly not a .458 SOCOM bolt.

Russellc

 

[RussellC]

Not saying everyone cuts the same exact bolt face, but they certainly should be nominally the same. Side by side, measured by pulling vernier calipers apart while wiggling to the point of nearly abrading the finish on each to find max ID.

5.56x45mm = .3870”
6.8mm SPC = .4335”
7.62x39mm = .4600”
458 Socom = .4870”

Notice the ejector on each - the ejectors are bored at the same position relative to center on all of these, and as such, reveal clues about the thickness about the relative rim wall thickness: on the 5.56, the ejector is sunk about 1/4 of the diameter into the wall of the bolt rim, and the wall is obviously very thick. On the 6.8, the ejector is only slightly cut into the rim, the crescent cut is just visible if zooming in on the photo. The x39/Grendel ejector just kisses the rim wall, but the rim isn’t cut to inlet the ejector at all. The 6.8 and Grendel/x39 wall thickness look very similar, but that small crescent cut to relieve the ejector in the 6.8 which isn’t present in the x39 gives away the larger boltface cut, and thinner rim wall. For the big 458soc bolt face, the ejector is removed away from the rim entirely, free standing in the boltface, with an obviously VERY thin rim wall.

So with yours measuring .445”, there’s not enough clearance for a Grendel/x39. More clearance than my 6.8 bolt measured here, but call it a generous 10thou clearance all the way around, to the ~5thou my bolt would have. Maybe they relieved to the edge of the ejector bore?

But at .445”, as we’ve surmised, it sure ain’t a 458socom bolt!

Wiggling it like you say, a Mitutoyo caliper says .450.5, if I really wiggle I can get .451. I guess its for a Grendel?

Russellc

 

[RussellC]

Guess I need a .458 bolt again! Eas going to get the one Deltateam tactical sells for 49.99, but may just default to The Brownell bolt carrier assembly. Gunny used one in his thread and had no problems.

Russellc

 

[CarJunkieLS1]

223/556, 300 Blackout, 277 Wolverine, .204 Ruger, and others: .378"
6.8 SPC, 30 REM AR, .224 Valkyrie: .420"
6.5 Grendel, 7.62x39: .445"
.458 SOCOM, .50 Beowulf, .308 Win, 30-06, .270 etc, 7mm-08: .473"


Those are close bolt face diameters, bolt face depths vary as well between cartridges, do your research.

100% the 30 Rem AR is NOT the same bolt head diameter as the 6.8SPC and 224 Valkyrie.

 

[someguy2800]

100% the 30 Rem AR is NOT the same bolt head diameter as the 6.8SPC and 224 Valkyrie.

The original 30 Remington cartridge (circa 1906) is the parent case for the 6.8 spc. The modern 30 RAR is based on a 450 bushmaster case, but uses its own special bolt and barrel extension.

 

[RussellC]

I didn't think 6.8 spc and .224 Valkyrie were either. Apparently I need a Grendel barrel, and STILL need a .458 SOCOM bolt....

Russellc

 

[Varminterror]

@RussellC - What’s the depth on that Grendel bolt face? Is it .125” Type I or .135” Type II? I might be able to give it a home.