30 Cal, 1:9 Twist

[257Roberts]

My barrel maker had a 30" 1:9 twist in stock for 30 cal. Is a 1:9 too much twist for a 2156 155gr Sierra?

I know 1:10 is pretty much the go to for Palma, will work with about anything except maybe the super heavy 200+ gr.

I guess I havent heard off too many folks going 1:9 for Palma. Curious to hear thoughts.

 

[billshehane]

Too much for me-- I like 11 twist.

 

[mgunderson]

12 or 13 twist would be common for that bullet.

 

[LCazador]

My barrel maker had a 30" 1:9 twist in stock for 30 cal. Is a 1:9 too much twist for a 2156 155gr Sierra?

I know 1:10 is pretty much the go to for Palma, will work with about anything except maybe the super heavy 200+ gr.

I guess I havent heard off too many folks going 1:9 for Palma. Curious to hear thoughts.

If you go to the Berger website and calculate twist rate SG for the 155 Hybrid which is similar, it comes up with 2,0 SG which will work perfectly.

 

[DaveTooley]

I wouldn't want 2.0 I like 1.2-1.4 myself. I've shot as low as 1.1 with no problems.

 

[wkdickinson]

I had a 28", 1:8.5", 30 cal Obermeyer 5R about 10 years ago that would not shoot 155gr Palmas. It shot 168gr SMK fine and 200gr SMK were amazing, but not 155's.

 

[DirtySteve]

The faster the twist the better. Until a certain point. If the velocity is such that the twist rate causes the jackets to strip or rupture, then it becomes a problem.

 

[David Milisock]

The faster the twist the better. Until a certain point. If the velocity is such that the twist rate causes the jackets to strip or rupture, then it becomes a problem.

I would agree with th with one caveat and that's when shooting quality bulletts.

 

[DirtySteve]

I would agree with th with one caveat and that's when shooting quality bulletts.

Yes very true... The faster twist helps stabilize the bullet in the trans-sonic zone and also stabilizes the fast arm bullet nutation in the yaw.. I may have that part wrong it may stabilize the precession.. I need to re-read Litz's books..

 

[Kurz]

My barrel maker had a 30" 1:9 twist in stock for 30 cal. Is a 1:9 too much twist for a 2156 155gr Sierra?

I know 1:10 is pretty much the go to for Palma, will work with about anything except maybe the super heavy 200+ gr.

I guess I havent heard off too many folks going 1:9 for Palma. Curious to hear thoughts.

I have used the Bartlein 1:11.25" twist for years in the Palma rifles I shoot.

Even so, your 1:9" twist using the 155 gr. will still only generate 236,000 RPM at a top end velocity.

Running a what-if for the 230 gr. Berger in a .308 Win. will still be plenty stable with the 1:9" twist.

I wouldn't use the 1:9" for Palma but certainly would consider it for another Long Range cartridge and VLD bullet.

 

[Ned Ludd]

In my opinion, use the absolute minimum twist rate that will net you full intrinsic BC (or very close to it) of your bullet of choice. That typically means a twist rate that will provide an Sg of 1.4-1.5. Grossly over-spinning a bullet can generate undesirable factors such as increased torque, which can affect gun handling, jacket failure issues, and increased aerodynamic jump. These affects may not be as noticeable as those generated by grossly under-spinning a bullet (loss of stability, key-holing, etc). However, they are still undesirable effects. As has already been noted above, I doubt the RPM that would be generated by a 155 from a 9-twist barrel will be sufficient to caused a major risk of jacket failure. Nonetheless, you do not need a 9-twist barrel to fully stabilize the 155s when an 11-, or 12-twist will do.

I understand the current lead times for obtaining barrel blanks and the natural tendency to want to use the barrel your smith has in hand to minimize the wait. Unfortunately, even if you had the notion of shooting the 200s out of this new barrel on occasion, there is no "intermediate" throat length that would work optimally with both 155s and 200s, so you'd still end up with a compromise that might not do everything you want as well as an optimized barrel dedicated to a specific bullet weight group/class. My suggestion is to consider how long you may be shooting the rifle with this new barrel and do yourself a favor and obtain the correct barrel blank for the bullet you intend to shoot. I think you will be glad you did in the long run. If necessary, ordering from barrel vendors such as Bugholes (Southern Precision) that have standing orders to various barrel manufacturers may be able to cut down dramatically on the lead time you might expect if ordering direct from the manufacturer yourself.

 

[Swampbuck]

I would probably stick to a 1-12 if just shooting the 155. I have had great luck with the 11.25 twist as well

 

[284winner]

Not being a competitive shooter makes my knowledge limited in this subject of what's best for that particular bullet. What I can say is for me if I couldn't find a particular barrel and may be months and months before finding that "ideal" barrel, I'd settle in a 9 twist (for me). I've shot 150 grain bullets from a 9 twist barrel in a 308 and they shot well. As a hunter not target guy tho. My 10s stabilize almost everything I shoot. Exception being the heaviest(longest)of bullets. Barrel wait times are really long right now so depending on it's use, I'd probably have to think hard on that one.

 

[dcali]

That's way too fast. A 12 or 13 is what you want for 155s. Overspinning a bullet won't do anything for you except decrease accuracy and can even cause problems with jacket failures. For context, a 10 stabilizes 215s plenty well.

I don't know where this idea that "faster is better" comes from. As Ned says above, it increases aerodynamic jump, which is a major contributor to inaccuracy. When you spin something that isn't perfectly balanced (like any bullet), the faster you spin it, the worse things get.

 

[Ledd Slinger]

Don’t over twist your bullets. 9 is way too fast for 155gr and your accuracy will suffer. 10 twist will stabilize great all the way up to Berger’s 230gr provided muzzle velocity is sufficient. But I wouldn’t even use a 10 if I knew I’d be sticking to 155gr.

I’d say 12 twist is where you’d want to be with 155gr. I shot 180-200gr hunting bullets with a 12 twist for over a decade in a 300 win and no issues. Tried shooting 200gr bullets with an 8 twist in a 300 Norma Mag Improved and I probably could have thrown the bullets by hand more accurately at the target. Lol

 

[Swampbuck]

You should be able to find the barrel that you need with a quick search in the buy, sell, trade forum. I have a couple of 30 cal M40 size barrels on there right now. I'm sure you could probably find a long Palma barrel in fairly short order. Try here and snipers hide. Might want to post a WTB thread. With powder, bullets and primers being so hard to get these days I'm sure there is a Palma barrel out there sitting on a shelf.

 

[284winner]

Don’t over twist your bullets. 9 is way too fast for 155gr and your accuracy will suffer. 10 twist will stabilize great all the way up to Berger’s 230gr provided muzzle velocity is sufficient. But I wouldn’t even use a 10 if I knew I’d be sticking to 155gr.

I’d say 12 twist is where you’d want to be with 155gr. I shot 180-200gr hunting bullets with a 12 twist for over a decade in a 300 win and no issues. Tried shooting 200gr bullets with an 8 twist in a 300 Norma Mag Improved and I probably could have thrown the bullets by hand more accurately at the target. Lol

I've shot a 9 twist at 800 yards in a 308 with the 155 Berger's. We'll under one MOA at 800 yards. As I said I wouldn't compete with that set up but it worked just fine on game. Many deer shot with 9/10 twist barrels with 150+ grain bullets. I personally prefer a 10 twist but had a 9 T once that was almost shot out when I got it. Shot lighter bullets very good. Not like an 11-12 would but impressive for a wornout barrel

 

[Ledd Slinger]

I've shot a 9 twist at 800 yards in a 308 with the 155 Berger's. We'll under one MOA at 800 yards. As I said I wouldn't compete with that set up but it worked just fine on game. Many deer shot with 9/10 twist barrels with 150+ grain bullets. I personally prefer a 10 twist but had a 9 T once that was almost shot out when I got it. Shot lighter bullets very good. Not like an 11-12 would but impressive for a wornout barrel

Yeah I’m not saying it “won’t” shoot them ok, but why spend hard earned money on a barrel with a twist rate that you know will not shoot the bullet you intend to use to the best of its ability? Which I think that’s basically what the OP is asking. And in my personal opinion the answer is a hard NO on a 9 twist for 155s.

BR shooters never over twist their bullets for a reason. Some of the LR competitors will over twist by about 1/4 to maybe 1/2 of a twist but that’s it because they know anymore and their accuracy will start to fall off slightly.

In this scenario we are talking about over twisting a 155gr bullet by 3 full twists more than it needs. Don’t think you’ll ever find a 1K BR shooter winning matches with a 1 in 5” twisted 6mm barrel

 

[284winner]

Yeah I’m not saying it “won’t” shoot them ok, but why spend hard earned money on a barrel with a twist rate that you know will not shoot the bullet you intend to use to the best of its ability? Which I think that’s basically what the OP is asking. And in my personal opinion the answer is a hard NO on a 9 twist for 155s.

BR shooters never over twist their bullets for a reason. Some of the LR competitors will over twist by about 1/4 to maybe 1/2 of a twist but that’s it because they know anymore and their accuracy will start to fall off slightly.

In this scenario we are talking about over twisting a 155gr bullet by 3 full twists more than it needs. Don’t think you’ll ever find a 1K BR shooter winning matches with a 1 in 5” twisted 6mm barrel

Absolutely. Not a barrel for just shooting targets. Agreed

 

[dkhunt14]

My barrel maker had a 30" 1:9 twist in stock for 30 cal. Is a 1:9 too much twist for a 2156 155gr Sierra?

I know 1:10 is pretty much the go to for Palma, will work with about anything except maybe the super heavy 200+ gr.

I guess I havent heard off too many folks going 1:9 for Palma. Curious to hear thoughts.

We have shot the 240 Sierra in a 10 twist for 1000 yard BR. They shot really well. I would not go with anything faster then an 11 twist for the 155. Maybe even a 12 twist will be better. Berger bullets has a twist calculator on their website. Accuracy will suffer if you spin them too fast. Matt