Alternate calibers for ARs?

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Re: Alternate calibers for ARs?

Postby Archer » 10 Dec 2017 14

One problem I see with a lot of these caliber changes is they often appear and once they start to get popular some changes are made to the components or chamber size. This is often the case with rounds produced as wildcats for bolt guns but it appears to be pretty rampant for the AR oddball calibers.

As an example the 7.62x39 was apparently designed by Colt for a military contract with a deeper bolt to give the extractor some more meat. The contract died and the concept was all but forgotten. When the caliber was revived by other commercial interest they merely increased the diameter of the bolt face without deepening it as Colt had done. The weak point on the existing 7.62x39 guns seems to be the extractor.

The Grendel and Beowulf have both been created with essentially a 7.62x39 case head. The bolts for the Grendel have been produced both with a deepened bolt face (Typically known as Grendel II by everyone except Alexander Arms who deny the label concerning their components) compared to the 5.56/.223/.300 Blackout or the commercially available 7.62x39 bolt face AND also with the same commercially available 7.62x39 bolt face.

The Beowulf has AFAIK only been produced with the deepened bolt. As it is still AA proprietary the clones on the market typically use dimensionally compatible components but avoid the trademarked 'Beowulf' term.

I think 6.8 SPC has gone through a couple sets of chamber dimensions.

Even 5.56 NATO and .223 AND .223 Wylde are dimensionally different chamber cuts even if they use exactly the same brass dimensions and reloading dies.

I'm not even going to get into magazines at the moment.

You have to KNOW what your components are and what's compatible with what.
And this is especially true when you are building your own out of components.
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Re: Alternate calibers for ARs?

Postby Archer » 15 Dec 2017 05

Still on hold on the 12.7x42 (generic Beowulf) waiting on an adjustable gas block.
Managed to pick up another receiver set during the black Friday madness and there's a AR-10 set calling my name even though I don't need another .308 and I'm not certain I want to put together a 6.5 Creedmoor. I guess I might wind up building it as a 243 Winchester if I could find a good barrel...

Darn things are like Lays potato chips and leggo sets. Start off building one and pretty soon you've got a passel of tools and a home defense locker full of ARs.
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Re: Alternate calibers for ARs?

Postby GasGuzzler » 15 Dec 2017 20

I need a parts set with a door, door axle, axle clips, forward assist to put this upper together....and upper I don't need.
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Re: Alternate calibers for ARs?

Postby Archer » 15 Dec 2017 22

Yeah, I've got two stripped upper AR-15s, one big bore AR-15 upper and one stripper AR-10 either in the parts bin or at the gunshop waiting for me to pick them up.

I know I've got the upper parts for at least 1 or 2 of the AR-15s. The Big bore needs a FWD assist but I don't think anyone is making a door for them currently. AA leaves the door off theirs to increase reliability and probably because it's a bit of a pain to put one out oversized. Somewhere I've got the door and hinge pin for the .308 but I need to get the fwd assist it's the same parts as the smaller receiver.

I've also got several with the door and assist in place already and one slick side AR-10 upper with the door installed.

Typically the small ones take 1 Circle/E clip. The AR-10s often don't take a clip but use a blind socket instead of a through hole.
I forget who it is but somebody's making an aftermarket headed pin that doesn't require a clip at all.
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Re: Alternate calibers for ARs?

Postby GRV01 » 20 Dec 2017 05

http://www.thefirearmblog.com/blog/2017 ... 5-70-auto/

Well talk about an alternative caliber. This company had just announced a modified AR10 platform firing 45-70 caliber called 45-70 Auto that has the rim remachined to be rimless I guess. Dont worry! Buying the rifle will also get you 50 cases!

Im not an AR guy, but from what little I know avout that family of firearms and its chamberings I do,t see how this is supposed to he better than 450 Bushmaster or even 458 SOCOM.

Also swallow that sip of coffee first before looking at the price
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Re: Alternate calibers for ARs?

Postby Ranch Dog » 20 Dec 2017 07

GRV01 wrote:Im not an AR guy, but from what little I know avout that family of firearms and its chamberings I do,t see how this is supposed to he better than 450 Bushmaster or even 458 SOCOM.

Ahh... first guess is big boy bullets and a case that has 18 to 19 grains of additional H20 capacity. The 450 Bushmaster will never get there with its use of .452 bullets. It and the 458 SOCOM were designed for a specific suppression role. The 450 had its chamber's throat designed around a 250 to 260-grain bullet and the 458 a 300-grain bullet. Both of these cartridges can use heavier bullets but with their chamber's having no throat, the bullets immediately compromise case capacity.

If they follow the 45-70 Govt spec they really don't have a throat to worry about only a leade that was designed for 405-grains of lead. In that 45-70 Govt data can be used to reload the cartridge, it indicates they are keeping with the parent case. Price is the only limiting factor on success, but that wood rifle sure is purdy!
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Re: Alternate calibers for ARs?

Postby Archer » 22 Dec 2017 04

Bring the price down to a U-Build it at $1800 or so plus optics and make the brass readily available and I might just be in.
5K Seems a bit stiff. Might be a whole lot of developmental funding that they are trying to recoup before the copy cats get rolling. Unless they are doing something special with the gas system or the recoil system all they really have are dimensional changes, none of which are unique, and which can't be patented. Even IF they are doing something odd with the gas system or the recoil system it's probably just parts swaps. Looking at their website they are using an adjustable gas block but it's a standard bolt and gas impingement so nothing much odd there. Everything else looks like variations on standard parts.

Standard .308 bolt carrier group ~$180 to $300 depending on finish (I picked up AeroPrecision's Nickel Boron for ~$180-$225 for my last two AR-10 builds.)
AR-10 receiver group ~$250-$350 (retail, many of these will include the takedown pins, bolt catch pin and sometimes even the installed dust cover. I picked up a matched set with the takedown pins for $160 in early December. )
Lower parts kit ~$80 (DPMS or AeroPrecision were on sale over the last month for $70, ARStoner was on for $47 last week.)
Carbine buffer tube $43 (Midway VLTOR)
Magpul ACS stock $86 (Midway on sale right now for $77)
Heavy Buffers extra heavy .308 buffer and spring $125 (Could go DPMS .308 standard carbine for $40 total from Midway)
Douglas Barrel $400 (price list from their website for polished, turned, threaded and crowned maxes out at $380)
Tank Brake $150 (Flat out guess, you can get the Chinese ones on Ebay/Amazon for $50. U.S. manufacture starts there (I picked up a cheap one for my .50 Beowulf black Friday made in U.S. for $47.) and goes to about $200 or so)
Fore end / Hand guard $450 Phoenix Weaponry ('KIT' should include adjustable gas block at $125 and handguard at $350 w/ rifle length gas tube. This seems about a hundred high vs. most quality production parts but prices go a bit higher than the Midwest Industries guards I tend to favor. An AeroPrecision guard would probably work well however at $235-$250 Max with a $125 SLR adjustable gas block for a $75 savings. They do mention a custom barrel nut however so maybe it's a wash.)
Trigger upgrade $160 (Geissele SSA & SSA-E runs $240 retail. I've purchased a couple over the past year or two for $160-$180 and they are on sale at $200-$220 almost every weekend from somebody. I'd not be buying P.W.'s version ala cart for the same kind of price.)
Magazine $45 (Probably more likely $28 but figuring oddball caliber markup similar to 50 Beowulf.)
Magpul pistol grip $20.

That adds up to about $2210 using the higher prices above, not counting optics. I did allow for cerakoted upcharge in most of the above pricing but figure around $200-300 for a complete rifle single custom color job. That'd still be only $2500. Figure another $100 on shipping for peace parts although if you are buying that way and not in a hurry you should be able to save 3 times that on sale pricing over the course of the build.) Whups I forgot to add a castle nut and a QD endplate so there's another $30.

Figure in a set of Warne rings for $100 or so ($80 on sale if you can wait for one. or go for an American Defense 30mm steel QD one piece mount for around $120-140 to save a little weight but still stand up to the recoil.) and a decent scope say a Leupold VX Patrol for ~$600.
Quality flip up iron sights for around $200 either inline with the scope or offsets. (on sale at Midway Magpul Pros for $170-180)

Figure around $2 per each for the brass maybe and that's an extra $100 for 50 and they might be charging more. Although they say you could buy the brass from them they don't appear to have it listed on their website. They also mention selling a form cutter if you wish to turn your own brass on your lathe but that price isn't listed either. I'm not real interested in turning my own brass to be honest but if I was buying an oddball caliber that showed no visible sign of support I'd be tempted to get the cutter and learn how to use it.

It only took about 10-15 years for the shorty big bore calibers to start catching on and they only did so because parts and ammo were starting to become available. It'd be nice in a way if it didn't take that long for this to catch on but realistically given the added expense of a large frame setup and the added weight I could see it taking longer or fading out entirely. Could be a heck of a lot of fun however.
Last edited by Archer on 22 Dec 2017 05, edited 1 time in total.
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Re: Alternate calibers for ARs?

Postby Archer » 22 Dec 2017 04

As Ranch Dog mentions price is a prime discriminator...
And even the $1800 I mention is a pretty hard sell vs. a Marlin 1895 guide gun at $750 with a rail already on the top of it. Not to mention a .308 AR can be had starting around a grand to $1200 for a baseline S&W or Remington off the shelf.

The prices I mention above are for quality parts and a free float setup. you could however easily assemble a similar set of parts without the names behind them or settle for a standard BCG instead of nickel boron and save $50-$100 and pick a Ballistic Advantage barrel for another couple hundred discount. You could easily assemble a very nice .308 for several hundred less than I mention simply buying parts on sale. A PSA .308 might be had for $750-$1000 although reviews on those have been a bit mixed.
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Re: Alternate calibers for ARs?

Postby Missionary » 23 Dec 2017 10

Good morning
Price and gearing up another caliber is what will keep me away.
Have enough good proven 308 battle rifles now that will do anything the AR can so I am content.
Have lever flippers for big brute force trauma.
But the 300 BLKout is a dandy ! Good close quarters thumper for all sorts of fine applications.
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Re: Alternate calibers for ARs?

Postby Archer » 24 Dec 2017 13

I've got several buds with the .300 BLK including one who's building one right this moment.
Another couple buds have gotten a little leery of them due to posts from folks who managed to chamber .300 BLK in 5.56 guns and touch them off. Some of that's people who just don't understand enough about firearms to own them in the first place and some of that's honest mistakes.

I like the 6.5 Grendel and 6.8 SPC over the .300 BLK. Probably a lot of that opinion is based on what I see as a better compromise between bullet weight and range and the fact I'm not planning on suppressing it.

I totally understand the urge NOT to get into yet another caliber. I've added 3 in the last six months and another 5 or 6 in the preceding 3 years or so. In almost every case it was adding another projectile caliber or if not a new set of grain weights and another brass casing plus dies and press accessories and in about a third of the cases new powder choices. That's a lot more expense than just adding another .308 or .30-06 and having all the infrastructure dies, components and ammo already on hand.
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