I understand that the 1.7 twist allows for a heavier bullet allowing a truer flight for longer distance. So whats the pro of having a lighter bullet from a 1.9 twist? Is it more accurate at shorter range(100 yds)? I'm referencing for AR's such as BushMsster 5.56.

Well for one price. Lighter bullets are cheaper all thing being equal. In my experience 1/7 shoots 55gr bullets just fine, it only starts having issues with the lighter varmint bullets (like 50gr and below). If you are hunting prairie dogs you might want those lighter bullets, but then the odds are you also want a even slower twist that 1/9.

Well for one price. Lighter bullets are cheaper all thing being equal. In my experience 1/7 shoots 55gr bullets just fine, it only starts having issues with the lighter varmint bullets (like 50gr and below). If you are hunting prairie dogs you might want those lighter bullets, but then the odds are you also want a even slower twist that 1/9.

 

Vlad, it would depend on what you define as just fine. In my recent tests of Wolf 62 grain , Privi 62 grain and Wolf 55 grain out of BC 16" 1:7 barrel, the 55 grainers performed the worst of the three. I got about 1.5 MOA out of Wolf 62s, Just under 2 MOA on Privi 62s and around 2.5-3 MOA with 55 grain wolf. I will be the first to admit that the sample here is not huge. I also did not measure the groups so these are eyeball results. But there does seem to be some visible degradation in performance. On the other hand, in my experience with wolf it can be less than consistent from case to case (and maybe even box to box). I seem to recall shooting decent groups with 55 grain wolf out of that barrel when I first got it...but now I have to wonder if I was using 62 grain and not 55.

I'd say use something other then wolf for testing dude. You know I shoot a lot of it, but it isn't a good benchmark.

I'd say use something other then wolf for testing dude. You know I shoot a lot of it, but it isn't a good benchmark.

 

Fair enough. Now that I am starting to load for rifle, I will test with my hand loads.

Right tool for the job... as other posters said...

 

Practice 55gr is cheaper than 62gr and up

Varmint 50gr bullets with hollow cavities for rapid expansion would be a use also

 

Nobody says you absolutely cannot shoot 55gr out of a 1:7. Just that the general consensus is you will not get as good as accuracy you would from using heavier bullets. Also, it has been noted that there is a potential for overspin, and the jacket coming apart on the bullet from this condition.

So let me see- lighter bullets(55, under) are preffered for 1-9 and are cheaper. The more heavier bullets want the 1-7 twist. But what about performence over different distences? And can you still shoot the lighter bullets thro 1-7 and heavy bullets thru 1-9? If you could only have one barrell to mix it up what would that be?

Yes you can mix just fine. Heavier bullets are "better" at longer ranges, they buck the window better, have higher BC, etc. In a 1/9 you can shoot up to 69gr bullets but that will be dependent on bullet with diminishing returns, the low end being around 45-50gr depending on bullet weight. In a 1/7 the low end is 55gr and the high end around 75. Again, different bullet profiles behave differently so each barrel will act a bit different with each bullet.

I've seen 1:8 spoken of as an ideal compromise. Can apparently go as heavy/long as 77gr, but still pretty accurate when shooting lighter bullets. Only thing is that they seem to only be offered in stainless steel barrels without chrome lining.

I've seen 1:8 spoken of as an ideal compromise. Can apparently go as heavy/long as 77gr, but still pretty accurate when shooting lighter bullets. Only thing is that they seem to only be offered in stainless steel barrels without chrome lining.

 

A government profile, 1/8, chromed lined, rifle length gas system is my ideal barrel really, and thanks to some people in a different thread here I now found someone who is very close (no chrome lining) and for a reasonable price.