.355 Blackout?

[random guy]

There are several different uses for .300 BLK. For me, it's purpose is to extract the potential energy of short barreled rifles/pistols. This is a simple function of its larger bore and better expansion ratio compared to .223. So it had occurred to me before that an even bigger bore would enhance this trait, at least for shorter range use.

While thinking about the .357 Ring Of Fire cartridge, I thought I'd see how tough converting brass to something similar would be. First I cut a range brass .223 case to the shoulder, trimmed and deburred and ran it through a couple of pistol dies. (Bottom in the photo). Not bad but needs blown out. Starting with a .300 Blackout case I repeated the final steps and that is even simpler.


The result is just about a perfectly straight wall case which would headspace on the case mouth. Out of a 7" or longer barrel at rifle pressures, it should be fairly ferocious at short range and maintain full AR magazine capacity. Something that would increase the downrange performance and likely improve feeding would be a 9mm version of the tipped spitzer bullets which work so well in .300 Blackout.

I seated the bullets (115 Rainier and 147 XTP) to a random length. Plenty of room for deeper seating and heavier bullets.

http://s107.photobucket.com/user/hva...tml?sort=3&o=0

http://s107.photobucket.com/user/hva...tml?sort=3&o=1

Maybe it's already been tried in some form. Seems like it would be good for some applications.

[ShootistPRS]

The base of the 223 case is .377+/- and a 35 caliber pistol bullet is .357. In order to make a straight case you have to thin the new neck down to just .010".
Without neck turning the neck will be larger than the base making a reverse tapered chamber or at best a chamber that is larger in diameter than the case at the base. Straight cases do not usually feed well in semi-autos - its why the 9mm has a tapered case. (I know it can be done but it is difficult)

I do like your thinking and would suggest a .323 or .338 bullet would be a better idea if you can find a short enough bullet to fit the case and magazine.
A 150 grain .323 would be a good fit, I believe.

[random guy]

That's the main reason I stuck with 9mm bullets although .357 would open up bullet selection a lot.

Using a .355 bullet leaves .0111 neck thickness with a straight wall. I'll take every thousandth! Don't know if there is any problem with a perfectly straight walled chamber. Extraction might be troublesome in a semi-auto as you say.

My original thought was .338 bullets but a) I don't have any to play with and b) they are traditionally tough bullets for heavy game. The selection may be better nowadays with some new cartridges on the market. There are some good looking .348 bullets as well.

[FrankenMauser]

.338 (a la .338 Spectre) is as big as you can go without getting into issues created by having no shoulder, or needing to make the neck walls too thin.

Remember, the cartridges need to stand up to getting beaten and battered by an auto-shucker, as the trip into the chamber isn't always a smooth and pleasant one.

Most auto-loaders also need at least a little bit of taper in the cartridge design, or they bind up while feeding. In order to get that with ".355 Blackout" the neck walls would need to be no thicker than about 0.008". (And that's being generous.)

[random guy]

That must be why it has not been done already. Such a cartridge might be based on the 9mm Win Mag case head, like the .357 ROF, but that gives up mega cheap brass.

The loss of the 300 BLK shoulder doesn't seem like much of a loss though. It is hard to even get a headspace measurement on that little thing.

New design .348 bullets might work but that is not a common bore size.

[FrankenMauser]

Two things:

1. What are you referring to by ".357 Ring of Fire"? The only references I come up with are to the Coonan .357 Mag -- which is just a .357 Mag auto-loader based on the 1911.

2. The .348" bore size. Though I don't think it's a good idea in an AR, especially with a cartridge based on .223 Rem / 5.56x45mm, an uncommon bore size is just a speed bump (Pac-Nor offers it). For a while now, I've been trying to convince myself to pull the trigger on a 7.35mm barrel (0.298" bore) for a custom wildcat (again, Pac-Nor offers it). More than likely, it'll happen sooner than later. The only real requirement: I'll have to cast my own bullets. (Three versions already designed. )

[jmr40]

What are you referring to by ".357 Ring of Fire"?

He is talking about this thread. A guy has developed a wildcat 357 caliber handgun round he is pushing.

https://thefiringline.com/forums/sho...d.php?t=585771

[random guy]

2. The .348" bore size. Though I don't think it's a good idea in an AR, especially with a cartridge based on .223 Rem / 5.56x45mm, an uncommon bore size is just a speed bump (Pac-Nor offers it). For a while now, I've been trying to convince myself to pull the trigger on a 7.35mm barrel (0.298" bore) for a custom wildcat (again, Pac-Nor offers it). More than likely, it'll happen sooner than later. The only real requirement: I'll have to cast my own bullets. (Three versions already designed. )

Sure, anything can be done, but having certain elements already in mass production and common use make adoption much more likely. I think bore size, case head (and boltface) size and appropriate bullets are some of these elements. They turn "possible" into "relatively easy".

We are in an era though, where design and manufacture of "new" elements can happen pretty quickly (unless it's say, a proper .40 S&W/10mm ammo box )

Always thought that 7.35mm had a nice ring to it. Especially with Argentine on the end. Conjures up exotic images. What case would your 7.35 be based on?

[FrankenMauser]

Thanks, jmr40.

random guy: 8x57mm; for 7.35x57mm, or "Bozo Heavy .29".

(There's a long story that dates back nearly 30 years, behind the name, but it's not worth telling.)

[random guy]

Apparently Winchester is unaware that such a cartridge is technically impossible. Went straight to .357 dia. Even heavier bullets which could serve a purpose. That is a really straight case!

[Sharkbite]

Hmmm... 9x39 sounds like what you are looking for

[FrankenMauser]

Apparently Winchester is unaware that such a cartridge is technically impossible. Went straight to .357 dia. Even heavier bullets which could serve a purpose. That is a really straight case!

That's a negative, Ghost Rider. The pattern is full.

Winchester didn't go with .357" diameter, even if that's what was standardized with SAAMI. They went to .355" diameter, but their factory ammo is loaded with bullets averaging .3545" diameter. (Allowable diameter is .3540" to .3570".)
They also make the brass from scratch. It's slightly larger in diameter than .223 Rem, in order to not be perfectly straight-walled or have neck walls that are too thin.

.350 Legend being "based on" .223 Remington is as realistic as .308 Win being a "stretched" .300 Savage (as is so often claimed to be the origin).
You can't make the child from the parent. The 'child' must be made from scratch.

[Mobuck]

The practical way to do this would using the x39 case(already mentioned and already a factory production round) or the 6.8 case (or 22 Nosler if you wish to retain the common .223 bolt face).
For "practical use", the 9x39 seems to be a one trick pony. When shooting subsonic ammo, the only way to increase muzzle energy (most likely to meet some random number proposed by authorities) is to increase bullet weight while maintaining the velocity under 1050 and cartridge OAL to fit a specific magazine length.

[stagpanther]

or .338 bullet would be a better idea if you can find a short enough bullet to fit the case and magazine.

Woodleigh would probably fit the bill.

[P Flados]

My 357 Max AR (357 Max rimless) uses 223 brass with the neck expanded and then the case trimmed to 1.6". It is normally made on a 0.358" blank, and it headspaces off of the case mouth. This wildcat round has been out for a few years (obviously well before the 350 Winchester Legend). Lot of info on this round at https://mdws.forumchitchat.com/?forum=645266

The guy that did the 357 Max AR (known as Moleman), also came up with a shorter version where a 223 is cut off to Dan Wesson 360 length. This shorter version became known as the Mini-Mole. Making brass for this one is much easier (cut, trim & go). Since this one is more targeted for using pistol bullets, making it with a 0.357" blank is probably a good idea. A Mini-Mole with a 0.355" blank would probably also work ok. See https://mdws.forumchitchat.com/post/...0174?&trail=25

Mad Dog weapon systems can be contacted to have a barrel made for either of these two rounds.

If you want a 35 with little more power for the AR-15 platform, the 0.358 Yeti (https://mdws.forumchitchat.com/?forum=467590) works good but uses 308 sized cases and requires a compatible bolt.

[silvermane_1]

^I remember that thread and Davelliott, at the time i like the 357 ROF, thanks jmr40.