Home Forums Hunting & Shooting AR and Tactical Rifles 6.5 grendel to 357

I have been looking at cartridge dimensions and looked at the grendel. Has it been necked up to 357 or358. Looks like it would be a good match for pistol bullets. Would that work in an AR or would it be better in a bolt gun.

Yes it has been done. I forget the various names for it on the Grendel case but there are at least a couple variants. I did it on the 6.8 SPC case because dies are easier (just use 357 Herrett dies shortened a little), but either version works well in an AR15. These are best with 180-200gr bullets much like the 35 Remington. My 16" duplicates performance of a 20" 35 Remington lever action.

Thanks. I figured it would be a hoot with pistol bullets.

yeah, you can push pistol bullets pretty fast. I haven't done a whole lot of development yet with pistol bullets in mine, but did work up a 9mm 125gr FMJ to 2800 fps from my 16" barrel. It could be pushed higher, that was a very brief development out of curiosity.

The Hornady 180gr SS/PB is a good choice in these wildcats, as is the 200 FTX and any of the other standard 35 Remington bullets.

I'm about to start working up some (relatively) mild loads for my 10.5" SBR with the 140gr FTX bullet that's designed for the 357 mag. I'll probably aim for ~1600-1800 fps although it could be pushed much faster.

These are all in my "358 Herrett" as mentioned above, but you can expect very similar results in a Grendel based version. The Grendel case gives you a little wider body, but shorter with more room for long bullets. That's nice for long range VLD type bullets in smaller calibers, but doesn't have much advantage for the 35 cal in an AR.

An improved version of the Russian 9x39 round would also be functionally the same thing as a 35 cal Grendel.

Thanks for taking time to reply. I am using the Barnes copper solid in my SP101. It is very accurate and destructive on the targets I've shot them into. Being a solid copper bullet I thought it could take the higher velocity and be good for varmints. We are moving to the country soon and will be raising chickens and rabbits. Pest control around them was the thought.

Seems to me to be a lot of time, effort and money to develop a round for varmints.

What's wrong with a .223 and a 40 V-MAX pushed fast? They are devastating on coyotes and have a long reach. Or a .300BLK with suppressed heavies it you don't want to disturb the neighbors?

Just curious, not trying to talk you out of anything.

For the time being it'll be the 223 taking care of business.

Just for fun, my 358 Herrett based on the 6.8 case. The Grendel case will have a little more shoulder, with the shoulder farther back. These are the Hornady 200gr SP and my own 255gr subsonic HP.
I would not consider this a varmint round, any more than a 35 Remington lever action would be.



And with a 9mm bullet, compared to a 5.56 round. I was thinking I'd tried FMJ 9mm bullets, but it was actually 115gr Montana Gold JHP (.357 bullet) and 125gr Speer Gold dots.

In the first picture what cartridge is the one with the white bullet. Would you consider the 125 grain gold dot a short range deer cartridge?

I've often thought that a stretched 9mm case - same base & rim dia as a .223 would be pretty interesting. OAL would be matched to factory ar15 mags. Size it to use .357 and .35 Rem bullets, and add a fast twist to use heavier bullets.

Seems like it would offer good punch super & subsonic for hunting & defense. It could use the same magazines and bolts as a 5.56.

TnC, That sounds like a rimless 357 max. That would be awesome as far as I'm concerned.

The one with the white bullet is 300 Blk, there for comparison against the 358. The 300 Blk rounds are 125gr Nosler BT and a custom 230gr cast HP subsonic.

I definitely would not use that 125gr Gold Dot on deer out of my Herrett; you have to work within the intended velocity envelope of any bullet, and most pistol HP bullets will fragment like varmint rounds when pushed to rifle velocity.

I considered a straight wall 35 caliber 223 case; the resizing die situation would be easy (357 Max), but headspacing on the case mouth can be a picky affair in long straight wall cases at 5.56 pressure. I'm not sure how well it would feed in an AR anyway.

Looking at the 460 S&W and the 450 Bushmaster, they are very similar. Difference appears to be a rebated rim on the Bushmaster. A rebated rim on the 357 max looks like it would work.

I have a PTG reamer and gage for this. I don't have it in front of me but I think it is based on the 6mm AR Turbo 40*. So it is Grendel brass with .35 cal neck and 40 degree shoulder. This project has been delayed for me and I may never get to it so if you are interested in buying the tooling, shoot me a PM.

There is a website dedicated to just such things. Sorry, can't remember what it was called, but the consensus among those who tried it was that simply necking up a .223 to .357 had 2 problems: not enough shoulder and too long to feed.

In my limited experience with the BLK I've been getting tremendous case stretch when I push loads.

Necking a 223 case to .357 doesn't leave any shoulder. Thats why I called it a straight wall case.

Yonderling, that looks like a very nice and useable cartridge!

Thanks!
I'll admit that I use it most of the time as a subsonic round for heavy bullets; it is excellent for that. In full power form, it's not as good for general plinking as something common like 223, but it's a good hunting round.

As a side note, the Green Mountain blanks I used are proving to be very accurate.

Grendel necked to 375 on a CZ527 for subsonic work, Ive also done it in 338 , very efficient and quiet.

Hey now that's pretty cool!

Are there any commercial .375 bullets that expand at subsonic speeds? I haven't done much with that caliber.