1x8 vs. 1x7 twist rate for 16'' bbl

AR/M4 Custom Build Forum
1

Which twist should I get for my upcoming recon/reece build? 1x7 vs 1x8?

I know the military uses 1/7, but the Navy is using 1/8 Lija’s for thier reece’s.

If 77 grains is as heavy as it can get while still being magazine length isnt 1x8 a fast enough twist while still being fexible enough to use 45 grain varmit rounds?

Lastly is there any reason why Noveske offers 1/8 only in thier lightweight versions of thier 16’’ recon barrel?

Thanks for the input

2

My 18" 1:8 shoots everything from 45gr up to 80gr with no problems. My 1:7 over spins 45gr and they blow up (but shoots 55gr and up just fine).

Currently 77gr is the heaviest projo that will fit in the magazine (that I am aware of).

3

Edit – Incorrect info so it has been removed

4

62gr M855/SS109 is about the same length as a 69gr lead bullet and works fine from a 1/9 twist. The military uses 1/7 because of the M856 tracer rounds which are about the length of a 90gr lead bullet.

As far as 1/7 vs 1/8, unless you’re shooting the really long tracer ammo the difference between those two twist rates are pretty small and should be secondary to a lot of other considerations. Pick the barrel that has the size, length, weight, availability, price, etc. that you want and take whatever twist rate it happens to come with, so long as it’s one of those two rates.

5

I’m not sure of many 1 in 7" match barrels. Many are 1 in 8", Kriegers are 1 in 7.7", there are some 1 in 6.5" designed for 90 grain VLDs, but I just can’t think of any 1 in 7" out there. Maybe there are some.

6

75gr VLD and 75gr AMAX is long, SS109 is not long.

7

The 1x7 was used in the M249 (and then later the M16A2 and M4) because of the length of the tracer M856 which is very LONG and wouldn’t stabilize in 1x9. SS109 will stabilize in 1x9, but again the tracer will not.

8

Don’t worry about 1/7 vs 1/8, I wouldn’t loose any sleep over it for what your needs are.

Another reason the Mil went 1/7 twist was extreme cold.

I think we did a run of 1/8 poly for one of our dealers, he got them in light so I think that’s all that are on the market right now.

9

Douglas, llija and many others make 1:7’s

I would not sweat it

Personally since I shoot M856/L110 tracer at people occasionally I go for 1:7 in all my guns.

10

WOA barrel are 1/7

11

WOA barrels are 1/7