375 Win - 356 Win

[Cowboybart]

Looking at the factory pressures of the 375 Win (52,000 CUP) and the factory pressures for the 307/356 Win (52,000 CUP),  why is there no factory barrels in 307/356 Win.  I realize that the 356 is bottle necked and the 375 is straight walled.  How much more back thrust can this send to the frame??   I have seen custom barrels in these 2 calibers as well as 300 Savage, 6.5x55 and 7x57.   My guess is T/C afraid of somebody loading the 300 Sav up to 308 pressures, and the 7x57 to 280 pressures, but what about the 356 or 307???

[TNrifleman]

Your question is a good one. Your assumptions are probably correct. I think the 356 would be a good Contender cartridge. I have a 375 Win. Contender barrel (14" Super 14) and I really like it combined with a Leupold Gilmore red dot sight.

[Hopalong7]

Sorry guys but it just won't fly.  The force on the standing breech of your Contender is a function of chamber pressure AND case head size.  The .375Win uses the 30-30 case which is smaller.  The 45-70Govt. at factory level pressure is safe in a Contender, but if it was used at the pressure level of a .22Hornet(also quite safe in a Contender) it would destroy the gun or worse in short order.  GOOD SHOOTIN', Walt 

[Cowboybart]

The 375 Win, 30-30  and 307/356 Win all have the same head size,  .506".    The 44/ 444 Marlin are very close, .514"

[Hopalong7]

Cowboybart, I don't know where you're getting your numbers.  My .375Win measures exactly .420".  I don't have a .307 or .356 to measure, but Hornady's loading manual shows .470".  I suspect maybe you're looking at the diameter of the rim instead of the diameter of the base of the case just in front of the rim.  Yes, you could get a Contender chambered for a .307 Win or .356 Win and load down to some safe pressure, but then you're not gaining anything, and just one factory round gets mixed in by mistake and Disaster! SAFE SHOOTIN', Walt 

[Lone Star]

The force on the standing breech of your Contender is a function of chamber pressure AND case head size....

Not quite:  the force is the pressure times the maximum case internal cross-sectional area (high school physics) - contrary to what some believe it has nothing to do with the rim diameter. The maximum internal diamter of the .30-30 family is about 0.380" for an area of 0.113 in2.  A .356WCF case is about 0.435" or 0.148 in2, about 30% greater.  At the same pressure, the larger case exerts 30% more force on the breech.

The bottom line is, do not assume anything when it comes to pressure and force.  There is a very good reason that no responsible barrel maker chambers a Contender barrel for certain cartridges....it is called safety.


.

[Cowboybart]

I was comparing RIM size between the 375 and 356.  What Lone Star said clears things up as the area just ahead of the rim is signifigantly larger on the 356 than the 375.     
Thanx Lone Star.