7mm-RCM/PRC wildcat

[AKshooter93]

I’m kicking around the idea of possibly wildcatting the Ruger Compact Magnum/6.5 PRC. I’m looking at necking down a .338RCM to 7mm since it’s shoulder is farther back and would give more neck to run longer 7mm bullets like the 175gr Accubond LR and ELDX. My intent with this would be to push these bullets at the same velocities my 7mm-08 pushes the 150gr Accubond LR. I’m mainly thinking it being based on the RCM because it’s a short action, doesn’t have a rebated rim, and only has a 30 degree shoulder. In theory this should make it relatively smooth to chamber in smaller and lighter actions. I’m thinking this would be an awesome round for sheep and goats.

I’m an experienced reloader, but have not messed with wildcatting too much.
I don’t want to reinvent the wheel. If this has been done before, I would love to hear about it. Any help or advice would be appreciated. Thanks in advance.

 

[Zero333]

I'd personally go with the 7mm RSAUM. It's got plenty of neck and the rim is hardly rebated.
I think the rim of the 7-SAUM is something like 0.018" smaller in diameter than the base of the body.

7 SAUM brass should be easier to get than 338 RCM brass.

 

[rardoin]

As Zero said.....or....look at the 7mm Sherman Short mag. Based off the RSAUM case so will cycle in a short action, has a longer neck/shorter body, a 40deg shoulder and reduced body taper and will drive a heavy 7mm at faster velocities than the 7 RSAUM with the same powder weight due to increased efficiency of the case shape. If you put a 6br and the 7 SS beside each other the 7 SS looks a magnified 6BR...which is arguably one of the most efficient cases ever designed and (including variants based off this case) has set more records across different disciplines than any other case design. The good thing about the 7 SS wildcat is that Rich Sherman has reamers in stock or for rent, dies from Forster ready to go, headstamped brass that is headspaced/ready to fireforman or fully fireformed if you prefer. Giraud actually makes inserts for his trimmer that accept various Sherman cases. I just received some ready to form brass (ADG) and dies from Rich and waiting on a custom throated reamer; his standard freebore is .110", optional is .160" but I want one at .240" so I opted to have him order one for me through Dave Manson since the turnaround time in 1 month instead of 4 months with JGS. My plans are to run Berger 190's in a single feed action for LR F-Class in an open rifle. For hunting Rich already has you set to go with current reamer options that will handle up to the 180 Berger still keeping the bearing surface within the neck. He also has a ton of load data with various hunting bullets and active threads on LongRangeHunting forum devoted to each wildcat he makes. These are proprietary non SAAMI chamberings so you won't find reamer prints anywhere (at least legally). I have one friend who developed a wildcat that is very close to Rich's 7 SS at the same time it was being developed and he had high praise for the design for heavy 7mm bullets at upper nodes with great barrel life but he said if I were to pursue that route he suggested going with the 7 SS as all the pieces of the puzzle were in place. I'm just waiting on the reamer and getting one of my Borden actions 're-bolted' for a magnum boltface and timed for the trigger.

Robin

 

[std7mag]

Myself, i say go for it!
I can't say that i haven't pondered a 7mm RCM myself. But then again, i've pondered a 7mm WSSM too.
Keep me updated to your project!

 

[AKshooter93]

I’ve been looking at the 7RSUM too. If I were to neck down the RCM, could I have a smith cut a .284 barrel with a .338RCM reamer or will that leave the neck and area in the barrel too fat? Also, to make the brass could take 300RCM brass and run it through a .338RCM FL die with out the expander ball to set the shoulder and then use a bushing neck die and step down the bushings? Obviously, I would have to turn an trim afterwards. Thanks

 

[std7mag]

No, a 338RCM reamer would just destroy your barrel.
I'm sure someone, somewhere has done the conversion already.
I'd check with PTG & RCBS. As in call them.
They have literally thousands of cartridges on file.

 

[AKshooter93]

Good to know. Thanks

 

[Nightraider]

Good to know. Thanks

I've built a few of them

 

[AKshooter93]

Who did you get your reamer and dies through?

 

[deadduck357]

This is what I would have liked instead of Hornady going with the 6.5. A modern available 7 saum would have been nice.

 

[Alex Wheeler]

The 7 saum is an excellent case. Efficient and accurate. The Prc is very close, with slightly less capacity, which may be desirable for some uses. The 7 saum with adg brass is the easy way to go.

 

[std7mag]

Eh, if we all wanted the easy way to go we'd still be shooting black powder.

Cartridges have gone up, down, and sideways since the metalic cartridge was invented.

Compared to the cartridges i've designed, the 7mm RCM is a cheap, easy one.
Try coming up with 7mm Dakota performance on a standard (0.473") bolt face.

 

[BigGame]

The 7 saum is an excellent case. Efficient and accurate. The Prc is very close, with slightly less capacity, which may be desirable for some uses. The 7 saum with adg brass is the easy way to go.

Stumbled across this comment from 3+ years ago. The current 7-6.5 PRCW is largely the 7mm RCM contemplated in this thread with some custom refinements you've added, yes? Just trying to make sense of it all. I find the 7-6.5 PRCW really attractive.

 

[Alex Wheeler]

Its close. I would not base anything off the RCM. Its all about brass. So base the case off the prc. At this point in time, the 7-6.5prcw is as easy as the saum. 3 plus years ago, for a hunting rifle the saum just makes a lot more sense. Even today, for a hunting rifle Id just flip a coin. Obviously we have seen the slightly smaller case outperform the saum in the competitive side of things. But keep in mind, in F class the barrels are long. So when you see guys talking about 2900+ fps, remember thats a 30-32" barrel. The saum can do that in 26". Also, the saum's base to neck shoulder junction is slightly shorter. So you have a very small advantage if your trying to fit a long bullet in a mag. But neither of these two is a short action cartridge unless you push the bullet down into the case. The only thing different about my 7-6.5prc design and everyone elses is my throat diameter and lead angle along with a little larger base.