It's long enough and then some. At 3.125", it is about perfect for the 7x57 or any of the other rounds designed off of that case (6mm Rem and .257 Roberts). The standard 2.80" short action is actually also long enough for the 7x57.
Most gun writers and the gun buying public claim that bullets have to be seated too far into the case (to function in the 2.80" magazine) and use up space that "rightfully" belongs to the powder.
A basic rule concerning the relationship between an increase in case capacity and the corresponding increase in velocity states that for every percentage of case capacity increase, velocity increases at at factor of 0.25%. So if by seating the bullet out an additional 0.20" gives one a 4% increase in case capacity, you can expect velocity to increase by 1%...on a 2,700 fps load that give you a whooping extra 27 fps!
Any 06 length action is best for a 7x57, just be sure the throat is long enough to match....that way you can shoot bullets seated way out and in fact expect with the added powder space to compete with 280 velocities, at least with H414 powder...
Brno 21 and 22's are so set up and man can the churn up the velocity...Amazingly I seat the 175 gr. bullets half way to the cannalure, but every one of those guns shoots the 130 gr. Speer very accurately and they have to jump a mile to the rifling.
Posts: 42226 | Location: Twin Falls, Idaho | Registered: 04 June 2000
quote:Originally posted by Selkie: Well alrighty then, a MRC 1999 it is. My next question is barrel length and contour for a 7x57.
Yes indeed, the short M1999 is long enough for a 7x57 (3.125").
Sensible barrel lengths for a 7x57 probably start at 20" - after that it is really up to you, whether you like longer or shorter barrels. A 22" barrel would probably be pretty much standard - although lovers of long barrels might find a reason to put on a 24" tube...
Just like there is no hard answer about barrel length, there is no hard answer to your question about barrel contour. In general it is easier to get a stiff (stout) barrel to shoot well, although it is indeed possible to get a skinnier barrel to shoot well as well. I believe Dan from MRC once suggested .150" wall thickness at muzzle as a sensible compromise - for a .284 bore, that would give you a muzzle diameter of .584". Other suggestions I have heard are .180" wall thickness - muzzle diameter of .644". Barrel length also has much to do with how stiff a barrel is, the shorter you choose the barrel, the smaller the muzzle diameter you can probably choose - all within limits, naturally. Personally, I'd probably go with a 22" barrel with a #3 contour - as a sensible compromise between length, stiffness and weight. Your mileage may vary...
Does this help, or simply confuse the issue??
- mike
[ 07-28-2003, 19:03: Message edited by: mho ]
Posts: 6653 | Location: Switzerland | Registered: 11 March 2002
The 7X57 should be just fine in that action. I am not into "seating the bullet out" and "powder capacity lost due to seating depths" as it does not really make sense.
I would order a M 70 Featherweight contour barrel 22" long for such a action/cartridge. I don't see the point of a #3 barrel with a mid range cartridge. Pacnor and Douglas make such contours.
Go handle a M 70 Featherweight and then a standard grade M 70 and you will see what I mean unless of course you like hunting rifles with heavy barrels.
I also don't understand all this about seating bullets out and chambering short cartridges in long actions. If you want the 7X57 to go faster, why not get a .280? Same with the .257, just get a 25.06 if you want a faster bullet. Once you go to a longer action, don't you negate the supposed short action "advantages"? Also how much advantage are we talking? What velocity can you expect from a 175 grain .284 in a normal 7X57 action and what do you get in a long throated or longer action with the bullet seated out and more powder dumped in? Are the gains that great or are we talking 100-200 fps here? Not trying to be an ...hole here just somebody clue me in 'cause I'm missing the point.
NoCAL
Posts: 167 | Location: Woodland, CA USA | Registered: 11 February 2002
