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Posted: 10/13/2004 3:34:22 PM EST
Hi Guys,

I have a bone stock, bought brand new 24 years ago AR-15-SP-1 and was wondering what the barrel twist might be so I could start firing the correct ammo. I have always used 55gr. FMJ but was thinking of trying 62gr.

Any hints?

Thanks,

Boli

Link Posted: 10/13/2004 3:36:35 PM EST
Generally, they are 1/12 and I'm not sure if the 62gr bullets will work or not. Likely that they will, but I have no experience with this.
Link Posted: 10/13/2004 3:40:02 PM EST
I know the older ones are 1/12 My SP1 is a '64 and it's a 1/12 I don't know when they might have changed to 1/7 but yours might be if it's from the 80's Look under the barrel at the muzzle end and see if it has any markings. If it is a 1/12 I'd stick with the 55 Grn. I tried the 62 Grn stuff and it was all over the place.
Link Posted: 10/13/2004 3:45:36 PM EST
1/12.
Link Posted: 10/13/2004 3:46:21 PM EST
I think if it's an sp1 all original with a pencil barrel it should be 1/12. When the sporters came on the scene with the gov't profile a2 barrels in when colt had switched to 1/7. The 16" pencil barrels must have come out around this time as well...but not sp1...I think
Link Posted: 10/13/2004 4:09:22 PM EST
55gr is fine, there is nothgin 62 gr does better, except M855 and armor penetration.
Link Posted: 10/13/2004 6:14:39 PM EST
Cool...thanks guys. I'll just stick with the .55 gn.

Boli

Link Posted: 10/13/2004 6:18:01 PM EST
Yeah, 62 gr. will keyhole after 90 yards. read ammo-oracle.com.
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