Planning on a 24" Bartlein 5r for mainly 175 SMKs. May shoot 178 or 155 grain pills too.
Thinking 1/11.
Thoughts?
Thinking 1/11.
Thoughts?
What barrel twist rate for 308 build?
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Go for the 1 in 11.25" it will work great for 168 and 175grs. I would not go with the 1 in 10" unless you are going short and shooting heavier grain bullets or subsonic.
IF all you are going to shoot is 175 or 155's, then sure, the 11 will do. but if you plan on shooting anything bigger ever, then I'd go 10.
1-10" would be ideal, but just for the record I shoot 168g A-MAX and 175g Bergers out of my AW with a 1-12" twist and achieve .5 - .75 inch groups at 250 yards.
A 1-12 twist will handle most bullets up to about 190gr. A 1-10 twist won't give you any better accuracy. Most of my barrels on my guns are 1-11 or 1-11.25 and I shoot primarily 155's and 175gr. bullets. The only reason to go to a faster twist like 1-10 is if you intend on trying to shoot bullets heavier than 190gr.
Later, Frank
Bartlein Barrels
Later, Frank
Bartlein Barrels
Of the 5 308 barrels I've had, 4 of them were generally great - all 10 twists. The one that wasn't great was a 12.
I would personally choose an 11 or 11.25 if I was going to be shooting FGMM 175 or M118LR ONLY.
If I were going to be making my own ammo, trying different things, and wanted the most flexibility possible, I'll choose a 10 twist every time.
Questions you have to ask are:
"What are the negatives associated with a 10 twist, compared to an ~11 or 12?"
-increased spin drift @ long range - I can't hold, or windcall the difference of a couple inches @ 1000 yards, so this is a moot point for me
- potential to overspeed (and blow jackets off) bullets at high velocity - 308 doesn't have enough horsepower to do this with any 30 caliber bullet, so a moot point
- more elevation deflection due to wind via increased bullet precession - Again, I can't call the wind or hold good enough for this to matter at all.
- slight loss in velocity because of increased twist - I write this one off because I think there is more variability from one "identical" barrel to the next. I've never seen any compelling evidence or data supporting this.
- Not the "perfect theoretical twist" for the 175smk - I think there is some merit to this, which is why I stated above that if I was ONLY going to shoot 175s, I'd get a 11.25 twist barrel. That said, all my 10 twists have done beautiful with 175s.
"What are the negatives associated with an 11, 11.25 or 12 twist, compared to a 10?"
- less flexibility with bullets, particularly the heavies
- increased chance of keyholing with subsonics when using a can
For me, the easy answer is 1-10, but YMMV.
I would personally choose an 11 or 11.25 if I was going to be shooting FGMM 175 or M118LR ONLY.
If I were going to be making my own ammo, trying different things, and wanted the most flexibility possible, I'll choose a 10 twist every time.
Questions you have to ask are:
"What are the negatives associated with a 10 twist, compared to an ~11 or 12?"
-increased spin drift @ long range - I can't hold, or windcall the difference of a couple inches @ 1000 yards, so this is a moot point for me
- potential to overspeed (and blow jackets off) bullets at high velocity - 308 doesn't have enough horsepower to do this with any 30 caliber bullet, so a moot point
- more elevation deflection due to wind via increased bullet precession - Again, I can't call the wind or hold good enough for this to matter at all.
- slight loss in velocity because of increased twist - I write this one off because I think there is more variability from one "identical" barrel to the next. I've never seen any compelling evidence or data supporting this.
- Not the "perfect theoretical twist" for the 175smk - I think there is some merit to this, which is why I stated above that if I was ONLY going to shoot 175s, I'd get a 11.25 twist barrel. That said, all my 10 twists have done beautiful with 175s.
"What are the negatives associated with an 11, 11.25 or 12 twist, compared to a 10?"
- less flexibility with bullets, particularly the heavies
- increased chance of keyholing with subsonics when using a can
For me, the easy answer is 1-10, but YMMV.
What were the variables outside of the twist rate on these that caused your 1 in 12 to not be good? I've got a 1 in 12 that consistently shoots 1/2 MOA just curious.
If I had to do it all over again I would most likely choose the 1 in 11 though it does give you a larger range of options IRT to bullet weight.
I have a 1 in 11.25 twist on mine and it shoots both the 155 & 175 grain bullets very accurately. Rock Creek 5R.
Is there any drawback to the 1-10 twist when shooting lighter than 190gr? I am asking because I have one of your barrels in 1-10 and I shoot the 178 Amax. It does a fine job putting them in the same hole.
No not really. When you shoot a lighter weight bullet in a faster twist barrel the key is in the quality of the bullet and or the loaded ammunition. A poorer quality bullet and or loaded ammo where the bullet/loaded round has a lot of run out the faster twist will amplify the run out and this is what leads to the groups going sour. I'll give you an extreme example.
Had a rack grade Colt AR15a2. Factory 1-7 twist barrel. Shooting handloads with 69gr. Sierra's the gun would actually group in the 3/4" to 1" range at a 100 yards. One time at the range I ran out of my handloads but had some ball ammo with me. So I thought what the heck I'll use the handloads to practice my off hand shooting. Out of the first 5 rounds 3 of them went thru the target sideways (perfect looking keyholes). Went back to the range a few days later. More handloads with 69gr. bullets, some more ball ammo and I also loaded up some Hornady 52gr match boat tail bullets. The 69gr handloads shot the same. So all checked out there. Shot 5 rounds of the 55gr ball ammo. Again 2 out of 5 rounds went thru the target sideways. I then shot 20 rounds of the handloads with the 52gr. Hornady bullets and those loads averaged right around 3/4" at a 100 yards. Those 55gr and 52gr. bullets would've properly stabilized in a 1-14 twist barrel. The key with shooting the lighter weight bullets was the quality of the components/ammunition that I shot.
Later, Frank
Bartlein Barrels
A 1/11.25 works fine in my wife's Rem7005R with 168s and 178s. However, I don't see any disadvantage to getting a 1/10.
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