Home Forums Hunting & Shooting Custom Rifles & Wildcats Preferred twist for 165 - 168 out of 30 caliber?

As I noted earlier, Bryan Litz has found that while accuracy can be good or even great, when a bullet isn't what many would consider "over-stabilized" then BC is reduced, sometimes enough to make a difference at longer ranges, and certainly enough to make a difference in wind-drift. He's come to the conclusion that a little too much twist is far better than the "minimal ideal" twist.

But whatever. All he done is work for the U.S. Air Force on missile design, thanks to his aerospace engineering degree, been the head ballistician at Berger, started his own company to scientifically study rifle ballistics, and shot on the U.S. Palma team.

Wasn't doubting you John. Just trying to learn something new.

The mystery to me is why some rifles seem to be more accurate with one weight of bullet, while another barrel of the same make and twist will do better with a different weight bullet.

I would like to believe it is science, or something that could be adjusted like twist rates that could give a guy a better probability of an exceptionally accurate rifle with the bullet weights he has in mind. But it does seem like it is part mystery, part science, and part luck.

Throating, seating, ogive type of the bullet and bullet length all play a role.

I will say I've never seen a 30 caliber rifle bughole a Speer plinker or the Remington Accererators, regardless of twist.

1-10 for a 308....because eventually the 165-168's get ditched for 175-178's....

Very good statement, John! Probably went over the heads of most.
The key words were "at longer ranges". Bullet yaw due to over spinning decreases B.C. at shorter ranges, as you stated.

Guys shooting the 30BR in benchrest shoot a 1-17 twist that is appropriate for the 117-125g bullets that are VLD's.

Check out Berger's site as a listed for their minimum recommended twist rate for their bullets:

http://www.bergerbullets.com/products/hunting-bullets/

My custom 308 had a 1-12 twist and it would shoot tiny groups with all bullets up to the 168g range that was available back then, which agrees with Berger's Minimum twist required. I also worked up loads for the 180g Sierra BTSP and the 180g Hornady BTSP, accuracy again was fantastic.

The poster started this thread wanting to know what was the best twist for 165-168g HUNTING bullets, does not sound like he is a long range shooter, does he?

A 1-14 twist might be appropriate for him if wants to shoot Nosler, Hornady, and Speer cup and core bullets. Also, as you jack up the RPM's on a bullet, cup and core bullets are more likely to shed their jackets quicker. I saw this on predators and smaller varmints when going from 1-14" and 1-12" twists to a 1-9" twists in 22 caliber and 243 caliber bullets. I also found that slowing down the twist rate can also lower pressures, which can allow you to get more velocity. Every barrel is different, and there are no absolutes.

I put a 1-11 twist on a custom 7 STW that has zero freebore and a minimum SAAMI spec chamber, the velocity in this barrel is so fast checked with an Ohler 35P, I will not speak of it.

If a guy does not know what he may want later on down the line, then an appropriate twist rate for the Heavy 200+g bullets VLD target bullets would be a prudent decision.

The standard 30 caliber 1-10 twist has been a tradition for a long, long time. After Remington got busted on putting a 1-12 twist in the 244 Remington, effectively killing the new cartridge, everyone wants to over twist a barrel, just in case...safer to go to a 1-8" twist, just in case he wants to shoot a 240g VLD.

I figured there would be strong opinions on both sides. The Rock 11.27 Twist aalf speaks of will work for most all practical .308 bullets, current twist of many precision rifle and replaced the 1-12 of the old M40 sniper rifle. Litz's work on stabilization factors and bc is more than very interesting. But how much more drop or drift one would experience at normal hunting ranges would still be minimal and not sure one would notice it when the rifle shot bugholes. Not saying the 1-10 wouldn't either, but a buddy of mine makes a hell of a 12 twist .308 barrel and with the exception of my long range 300 RUM, I'd use that given the choice. Well not totally true, I am building a lightweight 300 Win Mag for elk on a Pierce Ti action and I will go with a little faster twist to shoot the 200gr Accubond. Just my opinion and I'm just a small time (nobody) rifle nut.

Spinning a 190gr SMK ain't the same as spinning a 168gr TTSX.

Do they teach stupid in Wisconsin? I've had 1-12" 30/06's, I'll never have a 1-12" again.

Agreed, it's a [bleep] stupid decision.

"Do they teach stupid in Wisconsin? I've had 1-12" 30/06's, I'll never have a 1-12" again."


Steelhead, so what were the issues with your 1-12 30-06? Barrel/rifle etc? I'm going to try the 168gr TSX mentioned above in a 1-12 308 because now I'm curious....I did say curious, not butthurt enough to to start name calling.

Barnes does recommend 1-11 for that bullet (just checked their website) so I'll try it in both, 1-11.27 and a 1-12. I am curious...I don't consider myself stupid by any measure.

Issues where that it would stabilize a bunch of the bullets I wanted to use in it.

The fact that you boys are spouting 1-12" without actually ever used a 1-12" with HUNTING bullets is some funny shiet.

190gr SMK, really? Bullets aren't getting shorter and I've NEVER had a problem making a 1-10" 30 caliber shoot everything well.

Again, we are talking HUNTING rifle. Extra twist will always trump JUST NOT ENOUGH.

And I'm not butt hurt, just tired of folks that don't know offering suggestions on what they don't know and wearing the don't know like a badge of honor.

Again, comprehension......

I never suggested a 12 twist, it was a point of interest on the 190's.

My choice was a 11.25", and I built one on it...your's a 10"...deal with it.

aalf,

While I have nothing but respect for your experience, why go as slow pass possible, or refine twist down to 1/4", for a HUNTING rifle? Especially when there is no downside to a 1-10" for the OP's purposes?

Right now I'm working on a article an article on "over-engineering" for a well-known periodical that basically specializes in hunting rifles. I'm going to discuss a lot of things, including triggers, magazines and safeties, but am now going to add rifling twist to the list, because this thread is a perfect example.

John,

In reality there's nothing wrong about going 10, but the OP never really defined his cartridge, what was his intended "deer" bullet/s were going to be, the terrain, comfortable/average shooting distances, etc. Although he's from Tx, it still leaves the questions, whether you assume a tower blind over feeders or not. Kinda like asking "I'm buying a new truck, what trailer should I buy"?

As to "down to the last 1/4", for years, Rock's standby twist is a 11.27", just by design of the gearing on the Pratt and Whitney machines.

While somewhat relevant to most loonies, accuracy is the is the defining barometer of a new barrel/build. So while Litz says over spinning has no downside, in reality, matching the twist to the bullet yields the best accuracy, a proven fact.

A lot guys don't have the knowledge, desire, ability, or platform to milk the best accuracy from their firearms, so the differences could never be utilized anyway.

I've changed my views on this due to Litz's research. I used to be in the camp of optimizing twist to the bullet weights I was going to shoot but now think the increased BC of a faster spinning bullet is going to benefit me more down range than a .1" smaller group at 100. I have an 8.5" twisted .260 and a 12" twisted .308. Both shoot very well with any bullets I care to put in them, up to 140gr VLDs in the .260 and up to 175gr VLDs in the .308. In fact, my best 10 shot group from my .308 was using 168gr VLDs. This one measured .662 MOA for 10 shots at 100m:



Even with the slower twist shooting this well for me, with the quality of bullets nowadays I highly doubt that spinning them too fast is a concern. Next time I'll be going 8" in a 6.5 or 10" in .308.

John

Well, he's partly right. A 1-12 will handle most lead-cored bullets up to 190 grains, but it's right on the ragged edge of even stabilizing at all for a 168 Tipped TSX in colder Texas hunting temperatures, say 25 degrees. And in a 1-11 twist a 190 Berger VLD will be leaving some of its BC behind at that temperature, even if it's very accurate, so would be more susceptible to wind-drift.

So whether the OP is shooting deer at "normal" ranges with something like a 168 Tipped TSX, or wanting go longer with a Berger VLD, a twist slower than 1-10 isn't any advantage.

Have you read any of Litz's research?

I've been thinking 1-8" twist just in case you want to thread, suppress, and go subsonic! I'm sending off an action and barrel (Brux 1-10") to do up a 308 with a 16-1/2" barrel just to be a suppressor host. I'm now wishing it was a 1-8". But the 10 twist will be fine with 208 A-Maxes and I can take those subsonic if I so desire.

I would never go less than 1 in 10 twist in 30 caliber.

1-10 out of a 30 cal is like peas and carrots, covers a lot of ground.

Another popular twist is the 1-8" with a 223 AI shooting the 75g A-Max, hands down winning combo. 1-9" twist is border line on a good day with the 75g A-Max, while the 1-8" twist is spot on perfect.

However, since I could go to 90g 22 caliber bullets in my 223AI and 22/250 AI, why should I not put a 1-6 twist on my rifles to accommodate the 90g? Answer: The 1-8" twist is perfect of the 75g A max, that's why!!! I don't have any intention of ever shooting a 90g, but maybe I should go ahead and order 1-6" twists just in case I really don't know what I want.