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Ordering new LRR build last minute advice!

 
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  #15  
Old 05-01-2013, 09:07 PM
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Re: Ordering new LRR build last minute advice!

Quote:
Originally Posted by Michael Eichele View Post
I recommend the 308 but with a 26" barrel and at least a 11 twist if not a 10 twist. This will let you get the heavier bullets with high BCs up to a good speed. With the right powder you can see 2550 to 2650'sec with the 208 Amax in a 26" barrel. This is a 700 yard deer hammer with the windage of a 260 rem. more recoil but more down range energy.

DEER HAMMER thats good to hear! Whats the right powder? Varget seems to get alot of use in the 155-175 range.



Quote:
Originally Posted by redneckclimbing View Post
Search 7mm GT on here! It takes some time to from brass, but with 60.7 grains of H4831sc and a 29" barrel, and 180 gr Bergers I am getting a "validated" 3010 fps. and have never shot a group over 1 MOA with any load.

It willl consistently shoot .5 MOA with fairly regular .4 and .3 groups, at 300 yds. I would even let you use my reamer. I really want to see someone else build one but all of my buddies are being cheapskates!

My rifle weighs in around 13# and kicks like a kitten, could be the weight, but even in a lighter rifle it shouldn't be bad. There are also some new 6.5 ideas on here lately that are looking pretty good, 6.5ss and some others as well. If you want a wildcat.
Sounds like a very interesting journey you had, i read the thread where you brainstormed the 7mm saum wildcat. However it sounds a bit more involved than i want to go with on a rifle i plan on shooting a very high volume of rounds from.
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  #16  
Old 05-01-2013, 09:53 PM
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Re: Ordering new LRR build last minute advice!

RL17 and VV N550
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  #17  
Old 05-02-2013, 09:20 AM
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Re: Ordering new LRR build last minute advice!

A 26 to 28 inch barrel with 1:11 twist will handle all bullet weights from 150 to 200 grains very nicely at .308 Win. muzzle velocities. They've been doing that winning matches and setting records since 1963.

All barrels are suseptable to harmonics. None's any different than another. But each ones harmonics (which are higher multiples of its resonant frequency) that are the same for every shot fired regardless of the load used. A 22 inch light weight sporter barrel can be just as stiff as a longer, thicker heavier one. How long or stiff the barrel is has little, if anything, to do with the accuracy it can produce.
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  #18  
Old 05-02-2013, 10:47 AM
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Re: Ordering new LRR build last minute advice!

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Originally Posted by Bart B View Post
A 26 to 28 inch barrel with 1:11 twist will handle all bullet weights from 150 to 200 grains very nicely at .308 Win. muzzle velocities. They've been doing that winning matches and setting records since 1963.

All barrels are suseptable to harmonics. None's any different than another. But each ones harmonics (which are higher multiples of its resonant frequency) that are the same for every shot fired regardless of the load used. A 22 inch light weight sporter barrel can be just as stiff as a longer, thicker heavier one. How long or stiff the barrel is has little, if anything, to do with the accuracy it can produce.

Would a 10 twist hurt me any, reason i ask is because as of right now thats whats on the invoice, if its going to be a problem i will see about changing it. From what i gather the comp guys dont want the 10 twist eating up any velocity so they go with 11 to squeeze every last fps. If the only effect of a 10twist over an 11 will be slight velocity difference i guess i could live with that. If we are looking at a major difference i may just change the order.
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Old 05-02-2013, 10:57 AM
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Re: Ordering new LRR build last minute advice!

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Originally Posted by Bishop View Post
Would a 10 twist hurt me any, reason i ask is because as of right now thats whats on the invoice, if its going to be a problem i will see about changing it.
The rifling twist rate may change muzzle velocity 5 fps going from a 1:12 to 1:11. The amount's not an issue and extremly hard to measure accurately. In several decades of shooting high power rifle matches, I never heard any of the top scoring folks worry about twist rate effecting muzzle velocity; the best one will pick a barrel that's 5% more accurate over one that shoots bullets 5% faster. Nor am I aware of anyone conducting tests with two barrels having absolutely equal chamber, bore and groove dimensions shooting the same ammo and the only difference being twist rate that's published anywhere. I think folks claiming measurable differences are WAGing their numbers. WAGing = wild ass guessing; not scientific at all. Go calculate the rifling angle differences and see how tiny they are. There's a greater spread in muzzle velocity for a given load for the life of the barrel than a small difference in rifling angles has.

More important is that one should not spin bullets any faster than needed to stabilize them all the way to the target. Too fast and the bullet's tiny unbalance issues will cause too much of a jump off the muzzle axis as they exit. A 1:10's ok in a .308 for 200 and 220 grain bullets, but a bit fast for best accuracy with lighter ones. If your heaviest bullet will be at 180 grains, then a 1:12 twist is ideal for them and others down to 150 grains; a 1:11 if you'll be shooting in cold weather below 40 degrees F.
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  #20  
Old 05-02-2013, 11:11 AM
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Re: Ordering new LRR build last minute advice!

Quote:
Originally Posted by Bart B View Post

More important is that one should not spin bullets any faster than needed to stabilize them all the way to the target. Too fast and the bullet's tiny unbalance issues will cause too much of a jump off the muzzle axis as they exit. A 1:10's ok in a .308 for 200 and 220 grain bullets, but a bit fast for best accuracy with lighter ones. If your heaviest bullet will be at 180 grains, then a 1:12 twist is ideal for them and others down to 150 grains; a 1:11 if you'll be shooting in cold weather below 40 degrees F.

Looks like im going to try and change it to an 11 twist, the heaviest i will ever go will be 200 most likely be shooting 175's. Lightest would be 150's for the kids and ladies shooting at 300yards or less. And in the winter here it does often get below 40 especially in the mornings.


The place i got the velocity and twist theory was from accurateshooter.com on their .308 win section in the part about twist rate.
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