How will 62gr do in a 1:12 barrel?

h8mtv · #1 10-07-06, 16:59

I am wanting a 20" upper and really like A1 sights and lite barrels. I have tons of 62gr ammo (pretty much exclusively). I'd like to know if it'll run fine or not. I realize the 1:12 was made for stabilizing a 55gr bullet but I do not know if 7gr will make much of a difference.

TOrrock · #2 10-07-06, 17:04

Quote:

Originally Posted by h8mtv

I am wanting a 20" upper and really like A1 sights and lite barrels. I have tons of 62gr ammo (pretty much exclusively). I'd like to know if it'll run fine or not. I realize the 1:12 was made for stabilizing a 55gr bullet but I do not know if 7gr will make much of a difference.

From what I understand the bullet will destabilize very quickly, with keyholing not out of the question.

I know that there are some 1/7" twist A1 style barrels out there, they aren't common at all, but I wish someone would make some more.

I think FN made them when they were in the development stage for the SS-109 and the longer tracer ammo, but I could be wrong.

Boom · #3 10-07-06, 17:12

davemcdonald · #4 10-07-06, 17:24

I have seen a couple units try to qual with A1s and M855. It keyholed at 25m. At 50m some rounds were hitting broadside.
So good luck.
Dave

h8mtv · #5 10-07-06, 18:45

Sounds like a 20" A2 barrel is what the doctor ordered. Thanks folks.

STLRN · #6 10-07-06, 19:24

Quote:

Originally Posted by h8mtv

Sounds like a 20" A2 barrel is what the doctor ordered. Thanks folks.

The 7 grain is not so much what makes the difference it is steel insert, making the 7 grain heavier projective allot longer than if it was lead.

There was a heavier projectile tested along with the SS109 round called the XM777, it was shorter and could be used in A1s, but it didn't have as good long range capability.

Skintop911 · #7 10-07-06, 20:10

Quote:

Originally Posted by STLRN

The 7 grain is not so much what makes the difference it is steel insert, making the 7 grain heavier projective allot longer than if it was lead. .

That's my experience with commercial loadings in that weight, in early M-16A/1s and other 1/12 guns. Accuracy degrades as distance increases, but it's safe and serviceable training ammunition.

The BHA 60gr JSP, and it's "heavy FMJ" 62gr counterpart, shoot very well in one of my Fulton Armory rifles.

Hoplophile · #8 10-07-06, 23:37

Quote:

Originally Posted by h8mtv

I realize the 1:12 was made for stabilizing a 55gr bullet but I do not know if 7gr will make much of a difference.

Twist rate is based on length, not weight. The 62gr with steel penetrator are the same length as a 69gr solid lead bullet.

h8mtv · #9 10-08-06, 10:05

Thanks, I learned something.

Kisara · #10 10-10-06, 15:54

Quote:

Originally Posted by Templar

I know that there are some 1/7" twist A1 style barrels out there, they aren't common at all,

I've seen those by Colt- What model was that on, anyone know

jmart · #11 10-10-06, 17:16

Bushmaster 16" Superlight A1 Profile

May want to contact BM and see if they could build you a 20" in the same profile, or see if they could take a std 20" barrel and turn it down to A1 dimensions. They are 1 in 9" twist which would work fine with 62 grain pills.

TheDutchman · #12 10-12-06, 09:04

I have seen M855 keyhole broadside at 15m from a 1/12 twist barrel.