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New 7mm Wildcat....7mm Rogue

 
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  #1  
Old 07-29-2012, 11:04 AM
TMR TMR is offline
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New 7mm Wildcat....7mm Rogue

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 STW
7 Allen Mag
7 RUM
7/338 Norma Imp
7mm Super Mashburn
7-300WM
7mm Practical

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.

73gr: 3117fps
74gr: 3160fps
75gr: 3193fps
76gr: 3216fps

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
McMillan A3
DE Muzzle Brake
DE Cheek Piece
PTG Alum Bottom Metal
Jewell Trigger
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.
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Old 07-29-2012, 11:43 AM
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Re: New 7mm Wildcat....7mm Rogue

Thanks for the write up. Looks like you have a winner in the 7mm department here. Our thoughts and experiences are almost identical. I haven't seen the donut wth RWS brass in the necked down 300 win I do, Maybe that is something to do with the dies and necks length? But I sure seen the need to drop the charge in RWS brass due to its thick case and lower case volume. Takes about 3 gr less and velocity is still good.

My next one I will be digging into my brass stash and using some of my 300 win Lapua brass. Or even better I have heard that maybe Lapua will be offering 300 win again?? Time will tell, but I have a hunch the Lapua brass will add a little to this chambering and I want to test it out.

Glad to see someone move forward like you did with this. I see it as the perfect 7mm and a barrel life I can live with. Plus I don't really feel I am giving up a thing as the velocity is plenty good. So this is definatly the 7mm I want to hunt with and shoot.

Jeff
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Old 07-29-2012, 12:17 PM
TMR TMR is offline
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Re: New 7mm Wildcat....7mm Rogue

Because the shoulder is reformed and pushed way back vs the 300wm, that is where I was getting the donuts. Just necking down to make 7-300wm cases won't cause any issues. The 300wm shoulder becomes part of the neck with this case design. I will try to get a pick of the parent case vs a formed case.
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Old 07-29-2012, 01:22 PM
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Re: New 7mm Wildcat....7mm Rogue

Quote:
Originally Posted by TMR View Post
Because the shoulder is reformed and pushed way back vs the 300wm, that is where I was getting the donuts. Just necking down to make 7-300wm cases won't cause any issues. The 300wm shoulder becomes part of the neck with this case design. I will try to get a pick of the parent case vs a formed case.
Very interesting and good writeup! Isn't wildcatting fun. I ran into the same issue using 6.5x65 RWS brass to form my 6.5 Sherman cases becasue the neck material was originally part of the (Thicker) shoulder portion of the RWS case. Once you get that cured, it is a heck of a case. I'm curious as to where you had so much problem with the Ruger case? That is the parent for my 30/375 S.I. and even though there are a couple of steps, the cases form very nicely. Good luck and keep the data coming......Rich
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  #5  
Old 07-29-2012, 01:33 PM
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Re: New 7mm Wildcat....7mm Rogue

I cant wait to shoot out my 7RM and get my rifle back to you.
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  #6  
Old 07-29-2012, 06:15 PM
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Re: New 7mm Wildcat....7mm Rogue

Very interesting. In your original post however I would like to point one thing out about the super magnums in the 7mm family. As you mentioned and I would agree, they are not needed for alot of big game hunting, no arguments there but they sure are nice when you need the extra power.

Anyway, you mentioned that you had to step up to the ultra slow powders for this class of chambering. When I started development of the 7mm Allen Magnum I had just got finished developing my 257, 6.5mm and 270 Allen Magnum and with these there was no choice, you simply HAD to use the ultra slow burning ball powder such as WC-872 and WC-860 surplus powders and also US-869 from Hodgdon. As you correctly stated, they tend to be more sensitive to temp changes and can be a bit off as far as velocity consistancy.

When I started developing the 7mm Allen Magnum I simply deduced that it would be a waste of time trying the stick powders and went right to WC-872. Well over the years I had to develope loads with the 140, 160, 175 and 180 gr bullet weights and decided to try Hodgdons Retumbo and to put it simply, its a perfect powder for the super 7mms. I have used Retumbo in my 26.5" 7mm AM to drive the 140 gr Accubond to 3625 fps, the 160 gr Accubond to 3475 fps, 175 gr SMK to 3410 fps and the 180 gr Berger to 3390 fps with consistant velocity, no powder bridging issues at all and consistantly fine accuracy.

Just wanted to let guys know that Retumbo has been working extremely well with the 7mm AM and that is now my recommended powder for that wildcat. For smaller calibers with large capacities, yes, the surplus or ultra slow ball powder are perfect.

Sorry for the hijack, back to your wildcat. I used the 7mm Rem Mag for many years and loved it and built several 7mm-300 Win Mags for guys that shot GREAT as well but the 7mm STW kind of made it unpractical EXCEPT for those that wanted to use a true standard length receiver.

My biggest complaint about ANY belted magnum chambering, standard or wildcat is the variation in belt thickness, IE headspace measurement. I have measured pretty much all brands of brass and every one has had lot to lot belt thickness variations that were large enough that I could not chamber my barrels to a true zero headspace setting. The best brass generally had less then 0.005" variation but some US commerical brass had variation up to 0.020" and that was from a US brass maker that touts its amazing quality in brass. In reality it was terrible.

I generally use Win brass for my belted magnum chambered rifles but when I started I would set up my chambers so that there was no more then +0.005" headspace but no less then +0.002" thinking this would be plenty to chamber all belted magnum brass.

Well, that was not the case. The rifle got to the owner, he tried to chamber his virgin brass and it was not even close to chambering because his brass had belts that were 0.010" thicker then my brass and he was even using Win brass.

Simply put, I hate dealing with the variation in the brass, yes you simply chamber the barrels so that all possible brass will fit, that means headspace is very loose compared to a non belted case which can have the headspace set at a true zero setting and even if the virgin brass does not chamber easily, its a simple matter to slightly bump the shoulder so it will. That is not possible with the belted magnum, there is no bumping the belt back. Guess you could cut it back but that would be a PITA!!!

Anyway, Just curious how your setting up your barrels to offer proper chambering with all brass lots, even if same brand or if you have ran into this same issue of belt thickness variation?

Very interesting and obviously a hell of a good shooting rifle. I have always liked the accuracy of the 7mm Rem Mag and 7mm-300 Win Mag, not surpised your version is stacking them on top of each other!!
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  #7  
Old 07-29-2012, 07:52 PM
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Re: New 7mm Wildcat....7mm Rogue

I thought head spacing off the belt was ancient history???
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