I like 7mm's, especially the magnums. Two that I really like are the 7mm Mashburn Super Magnum and one of my own creation, the 7mm A&T Magnum. Both of the these cartridges will start a 160 gr. bullet at 3200 fps. This velocity is not guessed at but from readings on Oehler Chronographs. Both are formed from th .300 Winchester case. The Mashburn needs fire formed, but the A&T doesn't. Both are better that the 7mmSTW; I think the original data was either done at extreme pressures or on a typewriter. The loads I use in either the Mashburn or the A&T give me 10-12 loadings per case. My velocity readings are form 25" barrels.
Just curious how a 7mm case made for the smaller 300wmag brass giving less capacity than the 7STW will be better? What is your definition of better. Smae velocity at less powder yep that I would buy. Higher max at equal pressure I have trouble with.
As usual just my $.02 Paul K
Posts: 12881 | Location: Mexico, MO | Registered: 02 April 2001
Very simple if you had high school Physics; I only had a customer's 7 STW with a 28" barrel to chronograh, but it gave no velocities that were higher with 150-160 grain bullets than did the Mashburn or A&T. with 25" barrels when the case head expansion was kept the same. Until a 175 gr. bullet is used, there simply is not a powder that is slow enough, to generate more velocity with lighter bullets. If make all three .30 cal, the picture changes. You can use a good chrongraph,(mine is an Oehler) to check pressure by using the Physics Law of Diminishing Returns.
i think the key is the barrel length, here. the STW can use (needs) the long tube better with the heavier bullets...... at 25" they're all pretty much heating the air, the STW is just putting out a little more heat than the others.
I think you are correct, but if a longer barrel is used on a Mashburn in a Ruger No1 action as Bob Hagel wrote about in Rifle Magazine #103, the velocity of the Mashburn increases: from Bob's article 28" barrel 160gr Nosler 3290---24" barrel 3205 My chronograph readings with my rifles are very close-a little higher because of the 25" barrels-to Hagel's. If you call Rifle Magazine, I think a copy of #103 is srill available.
With the longer tube the STW SHOULD outrun it. Yes the Mashburn will go faster in a longer tube then a 24", but the STW will be carrying a larger powder charge that will actually get a chance to burn and push the bullet faster. With very long barrels meant for this kind of thing, capacity will always win. Its when we start going shorter (24" and below) that case efficiency plays into the game. After 25", efficiency be damned, its raw horse power.
If you think every possible niche has been filled already, thank a wildcatter!
Posts: 2287 | Location: CO | Registered: 14 December 2007
For the 7mm fans Kirby Allen has his 7AM. A 338 Lapua necked down to .284 and improved with a 30 degree shoulder. Will push a 200gr Wildcat bullet about the same as these others will a 160.
I spent several range sessions working up loads for a friend's 7mm-300 WBY, which is pretty close to a 7mm STW. It had a 28" 1-11" twist barrel and would only group with 120 gr. bullets. I settled on 120 gr. Nosler Ballistic Tip going between 3700-3750 fps.
Posts: 154 | Location: Texas | Registered: 05 January 2008
gunmaker yes and no, I have a 7mm Mashburn Super Mag and no I haven't used Quality Cartridge brass. I saw that they had the Mashburn brass and was going to order some just to have, but never got around to it. I use RCBS dies and simply necked down Rem or Win brass. My 7mm Mashburn is a early Rem 700 and set up as a mountain rifle with a orginal Mashburn Arms Company 22" barrel.
