Been working on this project since February and finally getting it all where I want it. I have played with just about all the 7mm Wildcats trying to find the best balance between performance, barrel life, powder consuption, ect. I wanted a cartridge that would fit into a standard magnum action and that could be fed from a detachable magazine if needed. Over the years, I have tested the following and kept records of performance:
7 Rem Mag
7 Allen Mag
7/338 Norma Imp
7mm Super Mashburn
The 7AM, 7/338 Norma and 7 RUM were all a little larger than I wanted to go with and usually need a super slow powder to get the performance. Most of the time its not a "extreme" powder. I like them, but just wanted to try something different.
The 7-300 WM had a short neck, although it didn't affect accuracy, it just didn't look right. I noticed with it and the Practical, bullets liked to jump. Seemed like there was a capacity cap where a little bullet jump came into play to get good accuracy. Reading Broz's post, this seem to confirm my thoughts as well. Wasn't a big deal, but I did want something forgiving. I tried to neck down the 375 Ruger case next, but it was a pain, so I abandoned it after ruining several cases in the process.
My 7 Rem Mag reamer that I developed is very forgiving and doesn't seem to matter what the load is, it just shoots. I had been doing alot of reading and research on the 7mm Super Mashburn and they were getting great velocity out of them back in the 60's with mil sulplus powder, so I thought, lets give it a try. It performed well and wasn't finicky at all. In a 26" barrel it was running right at 3100fps with top end loads using 180 Bergers. I almost just stayed with it, then a customer decided he couldn't live without it, so off it went. I had a theory based on today's recent accuracy cartridges, so I started drawing up a print based on my theory. I have a special throat design that I have tried on a couple of 6mm's, so I included that on this reamer as well. While the reamer was being made, I sent off the print to Hornady to get 3 sets of dies. Once the reamer showed up, I barreled up my test rifle with a 27" broughton between customer builds. I had great success with H1000 in the Mashburn, but this case had more capacity, so I started with Retumbo, which is what I use the 7RM. I added a few more grains than the 7RM, added a 180 Hybrid .010" off, and off to the hills to break in. When the first few rounds went into .482" CTC, I was pretty happy. Speed wasn't to bad at 3100, and I was still forming the cases. I ran up to 76gr of Retumbo before hitting pressue signs, great velocity...3240fps, but accuracy wasn't what I wanted and was getting sticky on the bolt. So, I grabbed some H1000 and started the test again.
75gr was shooting well under 1/2 moa, so that was the load I was going to run. Time to shoot it at distance and check it out. Everything performed perfectly and the cases lasted 9 firings before primer pockets were starting to loosen up. (This is using Winchester brand brass. Domestic brass is the only thing that will work with this case design. During the necking down forming process, RWS brass developed a hell of a donut and would require inside neck reaming. )
Time to put together the real rifle now. A few late nights in the shop after customer builds and she was finished up. Still awaiting on a new stock design from Manners, but bear season is approaching, so I dropped her in a A-3 I had on the shelf.
R Bros Rogue Action
Broughton R Bros contour, 27" fluted, 1-9 twist
DE Muzzle Brake
DE Cheek Piece
PTG Alum Bottom Metal
NF 5.5x22-50mm w/UL Rings
weight w/o bipod: 10.5lbs
This barrel is a little quicker, probably due to being a new barrel vs the old take off test barrel. The same 73gr forming load runs 3140fps. I haven't run any hot load through it yet, starting over with new brass to keep track of barrel life. Still shoots well under 1/2moa. Shot a nice sub 3" group at 675 and is boringly consistent. Here are some pics:
7mm Rogue (left) vs 7 Rem Mag (right)
Now, since this has been asked before. The reamer is proprietary to R Bros and I will not post a pic of the print. At this time we are continuing to test it out and will start doing builds with this chambering this winter. There will be a few of them out there for testing this fall. If all continues to go well, then we will continue.
I know I could have just gone with a standard case design, but everyone know what happens when gun guys get a theory in there head. I had to try it out and wasn't dissapointed at all. Might not be for everyone, but I am happy with it and I think it will be another good 7mm option.