Ultralight Ultralight Rifles

[Thegman]

Might the aluminum be less rigid/ more malleable and flex more, allowing the brass to expand more?

The only part of the bolt carrier group interacting with the cartridge during firing is the bolt itself, so I wouldn't think so.

My guess is the larger diameter cases have more surface area to stick against the chamber walls and/or their larger diameter bases increasing the force back against the bolt and forward against the chamber shoulder, resulting in the case itself locking the bolt lugs more tightly against lugs on the barrel extension, and those frictional forces increasing the force required to get the bolt to turn and unlock.

In a gas system, the gasses first hold the bolt as far forward as possible as the bolt carrier starts its rearward movement. That might reduce the friction between the bolt lugs and the extension during extraction, but those bigger cases are harder on extractors in gassers as well, so I imagine there's still more of those frictional forces being overcome with a gasser.

 

[JBradley500]

I wonder if a chrome lined chamber would help

 

[KyleR1985]

I think one of the problems is the side charger, if I’m thinking about it right. Especially if you have a chopped down bcg.

If you have a fully guided bcg, the side loading from side charger isn’t as bad.

 

[robtattoo]

Yeah, I tried 7.62x39 in a BCA () barrel.
It wasn't stupidly sticky, but it was bad enough that I decided that it was worth the effort & expense to build a .300 Ham'r with a Wilson barrel instead.

Speaking of barrels, if anyone decides to try & persuade X-Caliber to do a discount on a group buy of spaghetti profile, portless 6x45 barrels, I'm 100% in for one

 

[KyleR1985]

Yeah, I tried 7.62x39 in a BCA () barrel.
It wasn't stupidly sticky, but it was bad enough that I decided that it was worth the effort & expense to build a .300 Ham'r with a Wilson barrel instead.

Speaking of barrels, if anyone decides to try & persuade X-Caliber to do a discount on a group buy of spaghetti profile, portless 6x45 barrels, I'm 100% in for one

Working on it with Satern.

Emails asking about it might help…

 

[Luke S]

I just turned the gas block around on my 7.5 inch AR pistol and shot it suppressed while manually operating the regular bolt. Definitely felt less loud than when gas operated. I don't think I'd want to shoot it without ear pro but it's "less bad."

 

[robtattoo]

Working on it with Satern.

Emails asking about it might help…

I just sent them this:

"I was wondering if it's possible to have a barrel specially built.

There are a few guys on the Rokslide hunting forum that have built, or are building, ultra-utralight non gassed ARs as hunting rifles. I'm presently shooting a sub 5lb rifle, based on a TN Arms carbon lower & Solo 300 upper, chambered in .300 Ham'r, but I would really like a 6x45 for the extra range & bullet availability. Not that there are any flies on the .300, but it's really a 200yd cartridge.

I know that a bunch of us would jump all over a very light (16-18oz) 16" barrel. Especially if it had no gas journal or port! Currently nobody offers anything like this. I know it would be a very limited run, but would a run of, say, 10 or 12 be possible?

Thanks for your time & attention,

All the best,

Rob Peel"

Fingers crossed!

 

[BREAKCONTACT]

Not to further stir the pot, but did anyone ever end up doing a 6mm max barrel? Near same case volume as 6 arc sounds interesting. The numbers for it and the 90gr eld-x sounds like a really serious contender to 223 77gr tmk combo.

 

[KyleR1985]

Not to further stir the pot, but did anyone ever end up doing a 6mm max barrel? Near same case volume as 6 arc sounds interesting. The numbers for it and the 90gr eld-x sounds like a really serious contender to 223 77gr tmk combo.

How much is brass? Is it readily available?

Ive got the 95gr TMK at 2700fps in 6ARC at 2.255” coal. No doubt I’ll break 2700 with the 6ARC at 2.35” coal - just need to window my mags. This is with 16” barrel. If someone wants to file front of mag well, and upper, and barrel extension, to allow 2.41-2.45” coal, can probably be pushing 2800.

The 6x45 has already broken 2600fps with the TMK’s. Same as above, can probably get 2650-2700 with extra coal.

If you have some ELD-X’s you want to send to me I’ll load em up in the 6ARC and see what it can do. Hornady’s 18” gas gun data has 90GMX at 2750 max load with lever. I’ll probably match that.

Is there anyone shooting an ultralight AR well enough to need more speed or bullet than this?

 

[Hackleback]

Well, this thread is at 100 pages- I haven't kept up with all the goings-on. I was scrolling through an older reloading manual not so long ago and ran into this- the 7mm T/CU. seems like it might fit in here somewhere.


The 7mm TCU, like the rest of the TCU family, is based on a necked up and fireformed .223 Remington case. By far the most popular of Wes Ugalde's wildcats, the 7mm TCU has dominated the "production" category of both NRA and IHMSA silhouette competition. This should come as no surprise, since the 7mm TCU has virtually everything going for it. It is superbly accurate, and not at all finicky to load for. Its parent cases are readily,and cheaply) available, and case forming is a snap. It delivers reliable knockdown on the 200 meter rams without undue recoil. In short, it is exactly what is required for the silhouette game. The 7mm TCU is the most widely used,and still the winningest) cartridge in the "production" class today. Cases for the TCUs are formed by opening up the case necks on .223 Remington cases with a tapered expander. This is best accomplished with new, unfired brass. Frequently, .223 cases that have been reloaded a few times before forming will split at the neck during the expanding process. This can be minimized by using new cases, or by annealing older cases before attempting to expand the case mouths. The initial firing will blow the shoulders and body out to its final TCU dimensions. Once cases are formed, we strongly recommend neck sizing only, unless chambering becomes difficult. Contenders perform best when headspace is held to an absolute minimum, so great care must be taken to avoid setting the shoulder back during resizing. This simple step will extend case life, increase accuracy, and ensure reliable ignition. Silhouette shooters will find that the 140 grain Spitzer or Spitzer Boat Tail are outstanding performers for everything out to the rams. The heavier 160 grain Hollow Point or Spitzer Boat Tail will provide greater momentum for reliable knockdown on the heavier, tougher rams. Sierra produces a .284" diameter 130 grain Single Shot Pistol bullet specifically for cartridges like the 7mm TCU. Even with these lightweight, thinly jacketed bullets, the TCU is at its best on deer sized game when used in barrels not shorter than 14 inches. Although the 10 inch barrels can be just as accurate as the longer barrels, they sacrifice enough velocity to make reliable expansion somewhat questionable. Within these limitations, the 7mm TCU can be a reliable performer on deer, as long as shots are placed precisely.

Via Sierra Manual...

OAL 2.475 to 2.600" and velocities from 1600 to 2300 fps, depending on bullet used.

 

[Hackleback]

A couple other potentially interesting chamberings include; 7x45mm INGRAM (7x223 IMPROVED) and 6.5mm TCU. Now finding AR barrel makers might be a bit of a challenge.

 

[ezwy]

Well, it would work okay on the Solo with the caveat that you carry a rubber mallet while you're hunting to tap the bolt handle a few times. For whatever reason, it stuck more in the solo than with the steel bolt carrier. Maybe due to more inertia from the steel bolt carrier at the end of the recoil impulse, and that there was no "detent key" in Stupidlightweight's build helping hold the bolt closed(?). Those are the only variables I can think of.

Fortunately 5.56 and 6x45 are both very capable in and of their own.

One point on the 6x45 @ 18": X-Caliber says max length for the Spaghetti contour is 16", which I'm sure is also close enough to an 18" barrel that there would be no practical difference in the field, not that that should stop anyone...

I hadn’t caught that max spaghetti length of 16. I guess if I really want the 2 extra inches I’d just go light contour and be okay with a little extra weight to make it kid friendly. Thanks for pointing that out though.

 

[KyleR1985]

Someone can hand ream AI their 6x45 chamber, window mags, and probably having it pushing a 95gr bullet something close over 2700fps with 2.37” coal and a 16” barrel. With cheap or free brass. Fairly certain you can just swap out the bushing to 6mm in a 223AI set of dies, or use the reamer to make a die.

Hell we can probably send the reamer to Shaw and have them do it on their next run of port less barrels.

 

[KyleR1985]

View attachment 799092

Someone can hand ream AI their 6x45 chamber, window mags, and probably having it pushing a 95gr bullet something close over 2700fps with 2.37” coal and a 16” barrel. With cheap or free brass. Fairly certain you can just swap out the bushing to 6mm in a 223AI set of dies, or use the reamer to make a die.

Hell we can probably send the reamer to Shaw and have them do it on their next run of port less barrels.

And you can fireform brass from 6x45 to 6x45ai without dies. And they’re apparently no slouch on accuracy while fire forming. Neck size and trim cases use em 3-5 firings throw away and get more free or cheap .223 brass.

 

[Trackselk]

@Gman. Not sure what I was smoking (aluminum vs steel thing), my brain isn't working today....
@everyone. Take out the shipping, cerakote, and my bad memory and a green mountain chambered blank done up by LRI would only be about $365. Maybe even less if green mountain has non chambered blanks.
Enter into this equation your own custom chambering and you have a reasonably affordable option. No clue if they offer the sizes that you all have been talking about recently (?). FWIW

*that was purchasing the green mountain and LRI's work.

 

[BREAKCONTACT]

How much is brass? Is it readily available?

Ive got the 95gr TMK at 2700fps in 6ARC at 2.255” coal. No doubt I’ll break 2700 with the 6ARC at 2.35” coal - just need to window my mags. This is with 16” barrel. If someone wants to file front of mag well, and upper, and barrel extension, to allow 2.41-2.45” coal, can probably be pushing 2800.

The 6x45 has already broken 2600fps with the TMK’s. Same as above, can probably get 2650-2700 with extra coal.

If you have some ELD-X’s you want to send to me I’ll load em up in the 6ARC and see what it can do. Hornady’s 18” gas gun data has 90GMX at 2750 max load with lever. I’ll probably match that.

Is there anyone shooting an ultralight AR well enough to need more speed or bullet than this?

The max is based off of the 350 legend, so you just have to fireform, bci, the makers of the 6 max also sell brass. But I haven't seen a reamer print for it. It's a rebated rim case, but nowhere near as extreme as what the 22 nosler was.

 

[robtattoo]

 

[KyleR1985]

View attachment 799133

Haha we gotta get Deb and Stu talking.

 

[KyleR1985]

View attachment 799133

I forwarded her my correspondence with the other guy in the office so they realize it’s all the same thing.

Nice work!

 

[Thegman]

View attachment 799092

Someone can hand ream AI their 6x45 chamber, window mags, and probably having it pushing a 95gr bullet something close over 2700fps with 2.37” coal and a 16” barrel. With cheap or free brass. Fairly certain you can just swap out the bushing to 6mm in a 223AI set of dies, or use the reamer to make a die.

Hell we can probably send the reamer to Shaw and have them do it on their next run of port less barrels.

I've thought for awhile that the 6x45AI may be the best all-around cartridge for these rifles, though the 223AI with the same windowed mags would be afully close, especially if throated for the ELDs.

We'll see if the 6mm Max ever gets going. The 223-6mm Max would be another one.