lloydsmale
Well-Known Member
- Joined
- Feb 5, 2012
- Messages
- 991
you guys have way to much on the mind!
How do you say this, and keep it simple?
The shoulder angle acts like a funnel directing the hot gases into a flame path moving towards the throat and onwards. Where the two shoulders would meet in an imaginary angle is known to be the hottest point. The narrower the angle the further the vortex is projected out from the shoulders into the neck. Ideally we want this place to be in the first two thirds of the neck, or maybe even less. Now to get back to the .284 case a sec. The 35 degree shoulder angle is good, but the short neck length takes most of that advantage away. On the otherhand the 6.5-06 is just as bad with it's way too acute shoulder angle, but it does have a much longer neck length (about .32"). This is why a 6.5-06 imroved (there are several) has such a good barrel life. It's not really a knock on either case type, but it's to point "this is what you get." I personally like the 6.5x55 AI case design using a 6.5x57 as a parent case to make up for the known case shrinkage during fire forming (will be close to .04"). If you don't shoot but a hundred rounds a year, you'll never worry much about the issue. Yet if your a "F-Class" shooter you will.
The 6.5-06 is a little bit overbore as is the 6.5-.284. Not a tremendous amount, but still overbore. The 57mm case is not. Kinda reminds me of three guys I know that shot the 6-.284 in long range varmit rigs. They all used high end barrel blanks, but still changed barrels often. One of them gets the idea that he's going to mod the .284 case by pushing the shoulder back .100" with the rest going into the neck. He looses about 50fps, but is able to use the same barrel for well over twice the rounds. His buddy likes his idea and does one .150" short, but trims the necks back to about .33" (the other guy used the same neck length as a 6mm remington). He looses about 75 to 80fps compaired to the 6-284, but his groups are better. He gets almost two years out of the barrel! One of these guys sent me a pic of a marmet he shot at 800 yards using the Berger 88LD bullet. Had a grin on his face big enough to stuff a soft ball in it!!
gary