Twist rate 1:12 vs 1:10

bacardi

bacardi

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I know there are many articles on the net about this. I would like CGN opinions from your experience.

Considering the same exact rifle, which one is better for all around use. 20" barrel with 1:12 twist rate, or 24" with 1:10 twist rate?
I am looking to get into long range sniping.

Thanks.
 
long range requires fast twist for heavier(longer) bullets.
hands down 1-10 twist.

regardless of caliber general needs for target shooting longer distance is the heaviest bullet you can use with the most powder behind it.
flat trajectories is not a per-requisite when you have lots of time and known drop value's to calculate your elevation.
 
bacardi said:
I know there are many articles on the net about this. I would like CGN opinions from your experience.

Considering the same exact rifle, which one is better for all around use. 20" barrel with 1:12 twist rate, or 24" with 1:10 twist rate?
I am looking to get into long range target shooting.

Thanks.
Click to expand...

1:10...fixed it for you
 
Oh forgot to add that the calibre is 308 on bedded rifle with McMillan stock.
I like 20 inch for mobility and also the look. My goal is hopefully one day I can go for a mile shoot. Hehehe hey one can dream right? ;)
 
If we are considering the exact same rifle why are the barrels different lengths? Why not 20 inch 1:10 vs 20 inch 1:12?
I believe that you can't over stablize a projectile so the tighter twist rate is always better as it lets you shoot longer (heavier) projectiles if you choose to do so and still works fine with the shorter (lighter) projectiles.
Barrel lengh is totally up to the shooter. Longer gives more velocity for better wind fighting and less dial up for distance correction but a shorter barrel of the same profile will have less whip and will be slightly more consistent shot to shot. It's a balancing act you need to figure out based on the shooting you will be doing. If you are always going to be shooting from a stationary location like at a range then barrel length makes no difference and you may as well go with a longer barrel but if you will be carrying the rifle and shooting from different positions regularly then a little shorter overall length may be a benefit.
 
cr5 said:
If we are considering the exact same rifle why are the barrels different lengths? Why not 20 inch 1:10 vs 20 inch 1:12
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Because they are the same model but one has 26 inch barrel with 1:10 and the other is 20 inch barrel with 1:12. Is this uncommon?
 
1:10 will stabilize longer (heavier) bullets, thus helping going the distance. 1:12 is too slow to properly stabilize heavier bullets.

I have a 1:10 Broughton 20" bbl on my custom .308. Plenty accurate to 1000y at sea level pressure, stiffer and easier to carry than a longer bbl rifle. A fellow in the US tested the same bbl with 178 AMAX loads from the full 24" cut down from the muzzle to 20" with a total loss of only 30 fps.

"My experiences with cutting back a .308 barrel, which is a 10 twist Broughton:
24"- 2715fps
22"- 2700fps
20"- 2685fps

30fps in cutting back 4". That is with my 178 AMAX handload with Varget. Mitch is right it will vary greatly depending on rifle but also the ammo. Different bullet weights and powder will react differently to barrel length. That's why no one test can be taken that it will be the same on every rifle. Just what happened on that rifle with that ammo."
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If the task require to go beyond 1000-1200y, better switch to another caliber and a longer bbl rifle.
 
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My 24" Bartlein 1-11 does wonders with the 168 and 175 .30cal bullets.

I want to try the heavier pills soon to experiment.
 
It would seem that not to many have had the same barrel in different twist that could be changed for comparisons. I suggest you talk to the guys that make bullets and barrels. The above experience may be of some help and the general thinking the the heavier the bullet the faster the twist would be of course correct. You probably should be looking at 30" barrels min. but talk to the afore mentioned makers for long range.
 
Does anyone know the twis rate of FN SPR A5M XP in 20" and 24" barrel? FNH website only have the twist rate for the A5M model, but not the A5M XP ones.
Some forum suggests that the XP ones has 1:10, and the other suggests 1:12.
 
if you use your greenhill formula you will see that your 1/12 is good up till 180 grains( actually 1/13.5)-anything above that and you're into 1/10 territory- ( 1/11.5) but these are HUNTING BARRELS , NOT TARGET- all of my 308s are 1/12, and they stabilise 180s just fine
 
bacardi said:
Does anyone know the twis rate of FN SPR A5M XP in 20" and 24" barrel? FNH website only have the twist rate for the A5M model, but not the A5M XP ones.
Some forum suggests that the XP ones has 1:10, and the other suggests 1:12.
Click to expand...

From FNH:

•Calibers: 300 WSM or 308 Winchester
•Barrel Length: 20” or 24"
•Twist Rate: 1 in 12" RH 308 Win
•Twist Rate: 1 in 10" RH 300 WSM
•Overall Length: 40” with 20” barrel
•Overall Length: 43.5” to 45” with 24” barrel
•Length of Pull: Adjustable via interchangeable spacers
•Weight: 11.3 lbs. empty with 20” barrel
•Weight: 11.8 lbs. empty with 24” barrel
•Magazine Capacity: 4 rounds, with DBM; 5 rounds with TBM
Click to expand...

Offered in both .308 w/1:12 twist & .300 WSM w/1:10 twist in both 20" & 24" barrels in A5M trim. The .308 barrels (20" & 24") on the XP is the exact same as the A5M so the specs are to be the same. They must acheive 1 MOA or better Vs. no accuracy guarantee from the A5M... Marketing if you ask me.
 
I have a custom 28" barrel (Gaillard) in 308 that would give consistent 5 shot groups at .75 MOA, occasionally better but not consistant, using 155 gr bullets. However, using 185 gr bullets gave groups .5 MOA or better most always if I did my part. It has a 1:10 twist. I also have a Krieger and Bartlein in 1:12, 1:13 that are wonderful with the 155's. I'm restricted to using 155's so I'll never again get a 1:10 for what I need. Some people say you cannot over stabilize, I'm not so sure about that anymore.
 
Harry Callahan said:
From FNH:



Offered in both .308 w/1:12 twist & .300 WSM w/1:10 twist in both 20" & 24" barrels in A5M trim. The .308 barrels (20" & 24") on the XP is the exact same as the A5M so the specs are to be the same. They must acheive 1 MOA or better Vs. no accuracy guarantee from the A5M... Marketing if you ask me.
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I see that one, but that is under A5M one. Not under the XP one. This is the link for the XP one, and notice no twist rate.http://www.fnhusa.com/l/products/rifles/spr-series/fn-spr-a5m-xp/
 
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Harry Callahan said:
Twist rate on the XP is 1:10 RH. From the FNH 2015 product catalog Pg. 111... Specs are all over the place when you look at dealers listings or even forums...

http://www.fnhusa.com/files/2714/2116/8254/FNHUSA_2015ProductCatalog.pdf
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Awesome! Thanks for the link my friend. Now it is confirmed that it is 1:10 twist. I was worried a bit there since I don't want to spend over $3k and just getting 1:12. So my next question is, will a 20" barrel with 1:10 twist have trouble to shoot 1000 yard or a mile compare to the 24" one?
 
bacardi said:
Awesome! Thanks for the link my friend. Now it is confirmed that it is 1:10 twist. I was worried a bit there since I don't want to spend over $3k and just getting 1:12. So my next question is, will a 20" barrel with 1:10 twist have trouble to shoot 1000 yard or a mile compare to the 24" one?
Click to expand...

Nope, your good with either. Depending on the load, you'll be trans sonic at 850m to a tad over 1000m. ~20-30 fps loss per inch of bbl. Translate to .6 mil el. & .3 mil wind. (~10kt cross wind (9-3 o'clock), not taking any other factors into account) at 1000m from 20" to 24" shot with the same load, at the same time from the exact same position.
 
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