7mm mashburn is one of the easiest wildcats I've ever messed with. I've been running 300 win mag into my mashburn FL die and been working fine vs using the form and trim die. I say go for it
Same here, I borrowed my first set of 7mm MSM dies from another fellow MSM shooter while I was waiting on my dies from Midway. Once I got the new ones, I simply forwarded them back to my buddy and kept his old ones since I have them all set up for my rifle.
I was a little hesitant to do all that fireforming but honestly, I can't hurt the first 50 cases I formed a year ago. I anneal them regularly and they just last. I have ran 65 grains of IMR4350 with 140 Accubonds, 139 Hornady SPBT's, 140 BT's, 145 Speers, 140 Sierra's and probably some others I have forgotten. All of them net around 3150-3200. This last time I used some IMR4451 to do my forming since it was supposed to be a little cleaner, but it was only around 2980 or so.. No big deal either way, the cases come out perfect.
I will say when I started with MSM, Bob and another said get some H1000. I did and followed their lead. Took all of about 24 rounds to get me a load with the 160 AB and the speed they said (3200). My only problem was all I could get were 1 pounders back then. A couple of them were from the same lot, but I ended up with 75.5 with the 160 AB's (3200) and 73 for the 175's (3050).. Well, I was finally able to get a fresh 8 pounder of H1000.. Quite alot slower than my older 1 pound containers as 73 grains with a 175 PT only netted me about 2890.. Not a big deal, I'll just keep adding coal to get it up to 3050 again and I'll have that load for a long time I bet.
I like the cartridge so much because of the ability to run a lighter rifle and maintain some excellent reach. Blasted a poor cow this past fast in Wyoming and it just stunned her at 250 yards with the 160 AB. Blew on through and she lifted her head up once and was done.. Nothing special and I am sure elk hunters have seen it a million times, but is nice to have a 0-500 yard rifle without having to think of much of anything.
Mines just an old beat up 70 XTR that a great friend let me borrow a reamer for. That rifle has turned out some EXCELLENT groups for me on the factory barrel. I have liked the cartridge so much, I am pretty sure when I can put aside some loot, I'd like to have a nicer one made up. Till then, I'll keep slumming this old, ugly Model 70..
Another nice part, that I think Doc Bill mentioned was being able to use 7mm Wby data to work up with. I recently tried that with some 150 ETip's. It works, you don't have to stone wall the MSM to get Weatherby speeds at all.
Just my take on it so far, but I hardly ever go to the range without it honestly. I have a harder time picking a bullet I wanna run out of it than anything else..
