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rifling twists
guntrucker
Member Posts: 63 ✭✭
I have a thompson center encore 7mm mag 26" bull brl.i buying a 308 win brl. for it.I found out the 28" prohunter brl.has a 1in 12" twists were the 26"bull brl has 1in10" twists i have a springfield 4x14x56 with bullit drop compensators calibrated for 168 match. witch barrel would be better for long rang shooting 26" 1 in 10 or the 28" 1 in 12"twists. thanks to all
Comments
http://www.snipercountry.com/hottips/TwistRate.htm
The 7mm Rem mag will have better ballistics than will the .308 as long as each has adequate barrel length. Especially if both are shooting the 168 gr. bullet in their respective calibers. The 2" difference you are talking about is not as important as case size and natural ability to put the respective bullet out at necessary speed. Now if you were talking a smaller 7mm cal. vs. a .308 then the barrel length would make a difference. But it would have to be much smaller. A 7mm-08 has better ballistics than does a .308 and they are pretty much the same case just necked differently.
To specifically address twists, the key is length vs dia. at speed. with some other factors involved. The 1-10" will stabilize the heaviest in 7mm Rem Mag. It will stabilize them because it pushes the heaviest bullets fast enough that they get enough rotation to stabilize them. The 1-12" is optimal in .308 Win. for 168 gr. bullets, but as noted the same weight bullet in 7mm will do better. To gain advantage in .308 Win. you need to increase length(weight). The .308 Win case will only normally stabilize 180-190 gr. bullets, depending on muzzle velocity with a 1-12" twist. But by then you are going way slower than the 7mm mag any way.
-hope that helps
Edit: clarified to complete thoughts.
Also, the 4-14x56 Springfield is ballistically compensated for the 7.62x51 M118 special ball or the .308 using 168 gr. bullets @ 2650 fps out to 1000 yds. I like the rangefinding ability of the scope but as with all compensators there is no way to compensate for all altitudes and temps. Thats why I prefer the mil-dot where the drop is calcuable.
You could help us give you a better answer if you would tell us what you are considering for "long range shooting". Are you going to be plinking, target shooting for pleasure (at what yardage?), competition target shooting, hunting at long ranges. etc.?
"i have a springfield 4x14x56 with bullit drop compensators calibrated for 168 match."
Which bullet diameter and cartridge is your scope set up to use? Is it for the .308 Win. or the 7mm Rem. Mag.? These scopes are calibrated for a particular bullet and cartridge combination not just one specific bullet weight for all cartridges. I suspicion that when you check the scope specifications, you'll find that it is probably designed for the .308 Win. but read the specs to be sure.
Please let us know what you decide and find out.
Best.
Congratulations!
Keep us in the loop when you start to work up loads and shoot some targets.
Best.