Because of Hornady’s once in three years, production schedules, I have had to make cases out of Nosler 350 Rem. Mag. virgin brass. Finally, some 6.5mm Rem. Mag. virgin brass has shown up. All of these bulge out ahead of their belts and blow out slightly at the shoulders. My case taper has to be ironed into the Rem Brass before firing.

I too, have shorty necks. I should have left Hornady/Ruger’s 30 degree shoulders. They look neat, until I fire form them.

Now the new kids on the block are the newbies 6.5mm PRC, and the 6.5mm GAP 4S. Both of these can be necked down to 6mm, but for what it’s worth, I still like my design, as it cycles through a military Mauser’s magazine. ( Feed rails are slightly ground away to do this ).

I also did a 7mm version and in a 3.3 inch Mauser Mag. I equal the 7mm RSAUM, when that puppy is in a true short action, ( 2.83″ ), when shooting 175 gr. semi spitzers. ( Pull Downs ), so I don’t know exactly which product #.
An ancient Mauser military 7mm barrel was trimmed to 23 inches, and I cut off two tenon threads, to make a crude 2R chamber. But it’s a terror out to our club’s 500 meter gong. But so is the Rem. 7mm RSAUM.

The 6mm Rem. is 57mm, mine is 53.94mm, the 300 RCM is 53mm, the 6.5mm Rem. Mag., and the 6.5mm x 284 Norma are 55mm long.

But consider that these imp. 243’s are all 51mm or less. Shilen said that when their 6mm Rem BR is shot out, the barrel will be toast for some 12 inches. The big bruisers will burn their throats quicker, but you can set them back, re-chamber, and you’re off to the races again, or at least, as ‘lope and yote’ killers.

The real sleeper, IMO, after all of my trials, would be the 55mm long 6mm x 350 Rem. Mag. wildcat. I too would have that reamer ground back to 30 degree shoulders. But in this case, pardon the pun, the belt would still be what head spaces this modified case. So the new 30 deg. shoulders depths, wouldn’t be that critical. My RCM’s .530″ case heads do center these belted jobs, against my Mauser’s claw extractor, but I still have to play with false shoulders in order to safely fire form them.

The 6mm x 350 Rem. Mag. uses a belt, so there’s no sweating, pushing back those shoulders to 30 degrees, and leaving the case a mite short.

Maybe I’m just dense, but these results weren’t that obvious, when I started this project. And neither of the two newbie Hornady 6.5mm’s were around, a few years ago. And both of these 6mm x 6.5mm wildcats/improved barrels can be re-bored and re-rifled, to their parent cases’ factory chambers, down the road.

All of these shorty 243’s will take longer to burn out, but when they do, there’s a 6.5 C.M. in your future, if your magazine cannot handle a 257 A.I.

At least, I can have all of my test beds re-bored and re-rifled out to the 300 RCM, and end up with true 300 Magnum performance, without all of their noise and recoil. My new donor rifle is a Ruger Compact Magnum L.H. which has been a pleasant surprise. It still needs a standard length L.H. action to load three rounds down in the magazine. I figured that in a 6mm, two down are plenty, as it’s no way, any bear gun.

FWIW, with enough meat in the barrel, I can work out to a .430″ wildcat chamber, with just enough shoulder for my PT&G GO Gauge to hang up on. But so will the .416 x 350 Rem. Mag. And these were well known gunstock splitters.

All of Remington’s short belted cases used 25 deg. shoulder angles. And IMHO, this means that the new Hornady 6.5mm PRC, just necked down to 6mm, is poised to rule the varmints’ roost.

To this end, I necked down one each of George’s GAP 6.5mm PRC, and 6.5mm GAP 4S virgin cases, made dummies, and mailed them back to Kansas City, for GAP to peruse. I haven’t heard back to date.

I also have been bugging Ben S. at Hornady’s custom die desk, over a 7mm RCM with a 0.321″ long neck, but they have since gone with their two newbie 6.5’s.

I guess with suburban sprawls, target matches are trumping varmints, and open country Big Game. My 18 inch long barreled Ruger Compact Magnum rifle may be their last real stalking rifle, development. Both my 6mm x 6.5mm PRC, and 6mm x 6.5mm GAP 4S dummies feed O.K. through this CRF Compact Magnum Rifle.

Sadly, it’s only my 300 RCM ammo, and my wildcats, which jam up the feeding, when you put three rounds down into it’s magazine. So now, I hope that I’ve touched all the bases for anyone, here, wanting to make up a CRF rifle in one of these 6mm short mag. hotties, without running into any SAAMI’s Delta problems.

Hornady has been sneakily putting less and less case body tapers into shorter and shorter RCM based cartridges. is this like the 8mm Mauser, and 308 Win. not quite going into the 30-06G’s chamber???