If we were only considering 18" barrels shooting 75 grain 556. How much different would we expect the two barrels to perform? Shooting 100-600 yard type situations.

Small? Huge?


I would assume that the barrels would perform a lot differently if we expanded the ammo selection, and especially if we were shooting something like 55 grain ammo.

Likely not huge but depends on the barrel, ammo and how they play together.

I have one 1:7 that loves both the 55gr 193 stuff and the 77gr imi razercore, and another that does great with the 77s and patterns with the 55s, and another where thats vice versa. My 1:8 faxon does better with 55 than 62, etc

Just gotta test each barrel to find out, usually.

The quality of the bullet is more of a factor in accuracy, versus the twist. That assumes a sufficient twist rate, for stabilization, and a quality barrel.
A 75gr bullet is happy in a 1:7 or 1:8 twist.

I think the length is the key here...in an 18" barrel I cant imagine it would make a lick of difference.

1:8 should stabilize anything up to 77 gr just fine.

The reason 1:7 is used for military 5.56 weapons is to properly stabilize 62 gr tracer rounds, which, because part of the ass end of the bullet is red phosphorous instead of lead, have to be longer for the same bullet weight, and longer bullets require tighter rifling rates to stabilize.

Very little difference, if any.

Smeghead4761 said:

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1:8 should stabilize anything up to 77 gr just fine.

The reason 1:7 is used for military 5.56 weapons is to properly stabilize 62 gr tracer rounds, which, because part of the ass end of the bullet is red phosphorous instead of lead, have to be longer for the same bullet weight, and longer bullets require tighter rifling rates to stabilize.

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You hit what was bugging me.

I have two barrels and one is from a DD and is 1:7. In the back of my mind it was "better" because it was selected by the US Military for the high speed guys.

But I was also wanting to use my 1:8 fluted barrel because its so much lighter.

Knowing what you posted has pushed me to the lighter 1:8.