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colt sp901


jon308

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For awhile a 20" barrel was optional.  Then it was 18".  Long ago it was 22".

Depends upon powder used, bullet, system, etc.

I forget what the loss is between 20" and 16" in .308 Winchester but it is negligible at the muzzle.

I wouldn't worry about.  Find what your rifle likes and blast away!

Jon

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You really only gain 30-40 fps per inch passed 16". After 20" you only gain 20-25 fps till you reach 24". From 24" to 26" you only get about 10 fps per inch.

See?

And that is from some other study with different ammo.

Back in one of the early '80s Gun Digests, there was an extensive article comparing .30-06 and 7.62x51 NATO.  Surplus or issue ammo only (at the time...choices are much greater today for the little brother) and fired in a variety of then-fielded bolt-action rifles.  After 22" the 7.62x51 started losing steam quite a bit, with 20" determined to be optimal (think Remington's fat barrelled bolts these days). 

The .30-06 however kept gaining steam to an optimal length of the tested 26" barrel.  However, other factors such as barrel length and weight had them rule that the optimum for .30-06 barrel length should be 24".

I used to be on the poo-poo-the-16"-.308 bandwagon...until I got one.  Many things had me questioning old school "knowledge" rattling around my brainpan.

Besides everyone and their mothers making 16" barrels, there was some Mini14 tweakers that were chopping barrels fro 18.5" down to 16".  Reports were even old Minis that "patterned" at 100 yards were now shooting between 1-1.5 or 2 MOA, due to the increased rigidity or the shorter barrel (maybe there is something to the "size doesn't matter" argument).  The same effects of more favorable harmonics were noticed by those shortening the barrels on leverguns from 20" or longer down to 16" or so.

Then, when Ruger came out with their M77 Compact, people were getting match-grade accuracy from this tiny rifle with a 16" barrel.  Less barrel, less whipping around.

Another factor was learning more and more about reloading/hand loading ammo.  The ability to tune a load for an optimal exit from your barrel, while burning all the fuel and maximizing gas expansion in a shorter distance is awesome!  Now if I could just do that with Mexican food.

You'll have fun with your Colt!

Jon

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