1x7 or 1x9

[outerlimits]

have had an eagle arms flat top since 93. beautiful rifle, and shoots great. but how do i determine the twist rate of the barrel. it's a 20', and the only markings on the outside of the barrel is "ss 5.56". i'm trying to decide if i can shoot SMK 69's & 77's. any ideas?

[TBF]

Stick a cleaning rod with a tight patch on a jag in the bore, put a flap of tape on the rod, pull back the rod and measure the distance it takes for the tape flap to make a complete revolution.

Travis F.

[rhino]

That's a good idea. You could also contact Eagle (now Armalite) and ask them. I'll bet all of their barrels were 1in9.

In any case, you should be fine with the 69gr with either twist.

[kellyn]

According to Derrick Martin, a 1 in 9 twist will shoot any bullet that will fit in the magazine (i.e. not the Sierra 80 grainer). So a 77 or 75 shoot should in your 1 in 9. This has been my experience. However some say that you need a 1 in 8 to shoot 75-77s.

Rhino is absolutely correct that either twist will shoot the Sierra 69. But the best way to find out is to load up some 69s and 77s and go shoot them.