I have to roder a barrel and was wondering what you all think is the optimal twist. This will be a hunting rifle --- that I expect 1/2 MOA

I'm thinking 1/10 as I wish to shoot 150gr to 200gr. I've already decided I will not go the 5R route.

Thanks for the input.

quote:

I'm thinking 1/10

That would be my pick!

How long?

22"............1:8

24"............1:9

26"............1:10

Best .308 barrel= Shilen #3 Sporter 26"





3 Sporter A=1.200 / B=.815 / C=.625 / D=2.5 / E=6 / F=24 / G=26/ Weight= 3 lbs 7oz.

Mr Lilja recommends 10" or 11" for up to 200 gr. http://www.riflebarrels.com/pr...iber_twist_rates.htm

a 12" twist is optimal for 165 - 200 gr bullets. A 13 or 14" twist is optimal for 130 - 155 gr bullets. For hunting I use the 12" twist. BTW; a 12" twist is standard for milsurp and many commercial rifles.

Larry Gibson

quote:

Originally posted by Kabluewy:
What's barrel length got to do with it? I can't imagine why a 8" or 9" twist rate would be appropriate for a hunting 308.

Mr Lilja recommends 10" or 11" for up to 200 gr. http://www.riflebarrels.com/pr...iber_twist_rates.htm

I just ordered a new Pac Nor barrel in 308, #3 contour, throated for 165 - 168 gr bullets, in 12" twist, 20" long. If I want to shoot heavier bullets, that's what the 30-06 is for.

I have one 308 with a medium heavy (Sendero contour, #17 I think) Shilen stainless barrel, 12" twist rate. It's the most accurate rifle I have ever fired, and that's with Nosler factory ammo, using the 165gr Accubonds. It's a Hog Whacker Supreme.

KB

Only offering tested information here. How many RPM's do you think you can get out of a 20" barrel with a 1:12 twist? With 4" of "run-out" before the bullet engages the rifling? Perhaps 1 1/8? Is that fast enough to fully stabilize a 165 Gr. bullet? Or do you think with a short barrel like that, a 1:8 twist giving the bullet 2 full revolutions will provide more? "what does the barrel length have to do with it? If it didn't have anything to do with it, why don't you just hunt with a pistol? Do you thing that a longer barrel may add more accuracy due to "travel" and more engagement with the rifling? Take your .308 "#17 Sendero contour" with a 1:12 twist and I'll take my .308 Shilen #6/LT 26" @ 1:10 and lob a few down range with some 165's. I think/know you'll change your mind pretty quick.

All just a suggestion....

Still smokin that whacky weed in So. Cal., eh? Maybe the laws of physics are different in So. Cal., compared to the cold North, California being closer to sea level and all, thicker air, etc.

Maybe someone smarter than me can engage in this conversation with you. I'm pretty sure I would fail to connect, if I tried.

I didn't mention earlier that my 308 #17 is 25" long. Lobbing a few down range through it is what caused me to think it's the most accurate rifle I ever fired. Comparing it to a 10" twist would prove nothing to me, since at some point the limiting factor isn't the rifle, but me.

I've tried arguing with you fast twist guys before, and the discussion went nowhere. Think what you want. Do what you want. I'll have a 10" twist .308 barrel again only if I want to use 200gr or heavier bullets, and it won't be in a 308 Win. I can say with a great deal of certainty that I'll never own a 8" or 9" twist .308 barrel. I can't even imagine why they are made, except perhaps for sales to folks in So. Cal.

KB

You are correct, the air is a bit thick down here! However, it's not lacking the oxygen you are being deprived of up there. In any event, this is too elementary to discuss any further. I spent to many years testing thousands of barrels, contours, twists, combo twists, ratchet & forced grove twists, metal alloys, etc., etc., to try to prove already established facts. I was only offering a solution to a question. If you feel that a slower twist is all that is required or superior with heavier bullets than knock yourself out!

Seems to me like if the super fast twists were correct, the match shooting bunch would have somehow figured that out long ago and get the edge on the competition.

Maybe I'm just out of touch with the latest and greatest discovery.

KB

quote:

Originally posted by Kabluewy:
Seems to me like if the super fast twists were correct, the match shooting bunch would have somehow figured that out long ago and get the edge on the competition.

Maybe I'm just out of touch with the latest and greatest discovery.

KB

Thanks, been shooting BR/F-Class/Relay/Service rifle for 27 years, we figured it out long ago!

Oh and just for grins, maybe you can figure this one out? The military uses the M40/M24 .308 (7.62X51) sniper rifle. As we all know, it's a modified version of the model 700. In any event, it uses a unique rifling in that the risers/groves are NOT 180 degrees opposing. This is because those risers/groves are radial cut to a finish of 5-in & 5-out @ 65 degrees as opposed to normal 90 degree conventional cuts. Here's the question: Other than fouling and the obvious POI increase, why is the radial cut pushed at a rate of 1 RPM over 11.25" using the Sierra 175 Gr. MatchKing bullet in a 24" barrel?

quote:

Originally posted by Kabluewy:
Seems to me like if the super fast twists were correct, the match shooting bunch would have somehow figured that out long ago and get the edge on the competition.

Maybe I'm just out of touch with the latest and greatest discovery.

KB

The Match Shooting Bunch has figured it out. They most often use the heavier for caliber bullets with the largest BC's available, therefore, faster twist rates to stabilize them.

quote:

Originally posted by WhatThe:
why is the radial cut pushed at a rate of 1 RPM over 11.25" using the Sierra 175 Gr. MatchKing bullet in a 24" barrel?

I dunno

What does "RPM" mean?

KB

quote:

Originally posted by rcamuglia:
The Match Shooting Bunch has figured it out. They most often use the heavier for caliber bullets with the largest BC's available, therefore, faster twist rates to stabilize them.

Does the Palma bunch still use the 168 gr? At what twist rate?

http://www.sierrabullets.com/i...ing&volume=2&issue=2

KB

quote:

Originally posted by Kabluewy:

quote:

Originally posted by rcamuglia:
The Match Shooting Bunch has figured it out. They most often use the heavier for caliber bullets with the largest BC's available, therefore, faster twist rates to stabilize them.

Does the Palma bunch still use the 168 gr? At what twist rate?

http://www.sierrabullets.com/i...ing&volume=2&issue=2

KB

I'm not sure. I shoot a .300 WM and a 1 in 10 easily stabilizes the 208 A-Max and it is great with the 168's. My 6.5 Creedmoor uses a 1 in 8 with the 139 gr Lapua.

I guess your question had to do with the faster twists WhatThe recommended for the shorter barrel?

Leave the Creedmoor out of it, since it will only confuse the issue.

My 30-06 also shoots the TSX 165 gr very well, with its 10" twist. Also, besides the point.


Length of barrel? - besides the point as well.

Palma match shooting = 168gr, 13" twist rate, so I recommend 12" twist for 165 gr .308 hunting bullets, just to be sure that it has a fast enough twist rate.

KB

Kabluewy,

Palma rules have changed, however recently. The max bullet weight allowed prior to the rule changes was 155.0 grains with a .5 Gr. lead. This is why Berger came out with the 155.5 Gr. VLD Match. Palma (traditional) is now open to all bullet weights but is still limited to .308 or service using iron sights. We all use different bullets, bullet weights, powders, primers, cases, etc., etc. There is no "standard" other than "work-up" based on established ballistic facts like heavier bullets (better coe and wind "re" and YES A FAST TWIST RATE to stabilize the heavier bullets.

quote:

Originally posted by Kabluewy:

quote:

Originally posted by WhatThe:
why is the radial cut pushed at a rate of 1 RPM over 11.25" using the Sierra 175 Gr. MatchKing bullet in a 24" barrel?

I dunno

What does "RPM" mean?

KB

Revolutions Per Minute, the rate at which the cut is being performed over a particular length.

As my attorney said: "Please, don't confuse me with the facts".

KB

quote:

How long?

22"............1:8

24"............1:9

26"............1:10

Could you explain why a 1:8" twist would be any different in a 22" barrel than in a 30" barrel. Isn't 1 rev per 8" the same regardless of barrel length?

quote:

Originally posted by wistrapper:

quote:

How long?

22"............1:8

24"............1:9

26"............1:10

Could you explain why a 1:8" twist would be any different in a 22" barrel than in a 30" barrel. Isn't 1 rev per 8" the same regardless of barrel length?

I'll ask you... I have a TC/custom 357 Mag hand gun with a 10" 1:8 twist barrel. You have a 357 Mag bolt action rifle with a 20" barrel with the same rate of twist (ROT). For this query, we are going to be shooting the same bullet and load. 158 Gr. SP in front of 16.5 Grs. of H-110. Both weapons are "viced" in a universal block allowing no movement during pre-shot and post shot.

Which in your opinion is going to be more accurate and why?

First that is a really fast twist for a 357 but that does not matter for this. If they are the same contour and everything being equal the short one will be more accurate because the barrel is stiffer.

I kick myself for arguing, because I already know where this is going - nowhere. But anyway.

Say you have a Palma rifle. One in 13" twist and another in 9" twist. What do you have?

One Palma rifle, and another for which I don't know what one would use it for. Maybe impress Californians.

KB

I seem to have !!!!

I'm looking Remington #3 or #4 countour (probably #3) and 20 -22" barrel. Not that it matters, but it will be into a McMillian Montecarlo Hunter stock, Hart barrel, Stiller Predator action, Jewell trigger (man I love those triggers).

quote:

Originally posted by WhatThe:

quote:

Originally posted by wistrapper:

quote:

How long?

22"............1:8

24"............1:9

26"............1:10

Could you explain why a 1:8" twist would be any different in a 22" barrel than in a 30" barrel. Isn't 1 rev per 8" the same regardless of barrel length?

I'll ask you... I have a TC/custom 357 Mag hand gun with a 10" 1:8 twist barrel. You have a 357 Mag bolt action rifle with a 20" barrel with the same rate of twist (ROT). For this query, we are going to be shooting the same bullet and load. 158 Gr. SP in front of 16.5 Grs. of H-110. Both weapons are "viced" in a universal block allowing no movement during pre-shot and post shot.

Which in your opinion is going to be more accurate and why?

I'm not worth a tinkers damn at riddles, furthermore lay off the hair trigger as it was not my intent to quarrel with you. I am simply asking "Why would a 1:8 twist react differently due to barrel length. I'm a novice at best and am trying to learn.

quote:

I'm not worth a tinkers damn at riddles, furthermore lay off the hair trigger as it was not my intent to quarrel with you. I am simply asking "Why would a 1:8 twist react differently due to barrel length. I'm a novice at best and am trying to learn.

Didn't take it that way nor was I being facetious and I don't like hair triggers. I put the question in reverse in a hypothetical in hopes it would stand on it's own. In any event, to give you some idea in why you want to increase the "ROT" (rate of twist) in a shorter barrels is a multi-answer senerio, so I will leave bullets and their surface area out although it plays an important role, it will reduce a chapter in my explanation. To begin with many people believe that the propulsion starts in the chamber/case and ends in the chamber/case. This is NOT true. Depending on the "RBC" (reactive burn rate) powder continues to burn in the barrel. This of course causes expansion to the barrel which leads to greater "slip" across the lands. To prove this fact all you have to do is watch a high speed video of a bullet leaving a barrel. You will notice that gasses in the form of grey smoke exiting prior to the bullet. Timing of these gasses is a ballistic tool rarely talked about however, prove that gasses are passing the bullet and slip is in fact an issue. When you see a flame coming out of a "cold" barrel, this indicates the use of a slow burning powder and perhaps ignition. In any event, it is the tell-tail sign of major slippage. Of course it is normal for hot barrels due to existing expansion. With that, many people feel that the projectile engages the rifling groves right away and follow the rifling the length of the barrel. Again, this is NOT true otherwise concentricity (how straight the bullet lies within the case and its alignment with the barrel) would not be of concern. To think that the bullet follows the rifling in its entirety would lead to major slowing of the projectile. As we know, this is not true as well. Heavy barrels to reduce expansion have shown us all that; reduction of slippage and gas escape have provided great improvements in accuracy. This is more proof. So lets say that you have a 20" barrel and 1:10 ROT and after you developed your load you determine that your bullet travels 4 inches before engaging the groves and that your slipage equals 1/2 turn every 10 inches. What is your "true" ROT and will that provide enough in flight RPM's to stabilize your projectile?

Since the invention of long guns, it has been a well established fact that a longer barrel provides better accuracy and velocity. The lenght provides stabilization while at the same time the lenght allows all the propellant to burn putting more gas/pressure behind the projectile leading to faster velocities. So should you wish to have a shorter barrel, you must increase the ROT to provide for the lack of "grab" due to slippage and to increase the "in flight" RPM's of the bullet due to the lack of velocity you would get in a longer barrel.

When all is said and done here, I am NOT a good teacher nor do I always explain things as well as I wish to. But I do hope this brings some light to your question..

Thank you What The, I had never given that a thought. Is this the reason why some use progressive rifling twist rates?

quote:

Originally posted by wistrapper:
Thank you What The, I had never given that a thought. Is this the reason why some use progressive rifling twist rates?

Absolutely! Many match shooters have taken these barrels to the games. But and a big BUT, the jury is still out on a few details on the combo. One of them is the transfer rate in length and the transfer rate in twist. A formula has not yet been developed for these issues as of yet. However, even with the "SWAG" system (scientific wild ass guess) large improvements have been established based on HS video results and ext. ballistics. We'll see where this goes in the future...

Too bad they don't have one of those little emotiacons with a cross-eyed figure with his tongue hanging out.

KB

If anyone gives a damn, I ordered it yesterday and after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

And I'm looking to go 22" completed barrel length.

Man, I love rifles!!!!!

quote:

Originally posted by Kabluewy:
Mr Lilja recommends 10" or 11" for up to 200 gr. http://www.riflebarrels.com/pr...iber_twist_rates.htm

quote:

Originally posted by vapodog:

quote:

I'm thinking 1/10

That would be my pick!

quote:

Originally posted by BISCUT:
after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

You did the right thing, got the right advice, and I'm sure you will be happy with your choice.

If it was not for the 200gr requirment, I would have recommended a slower twist.

Regards,
KB

quote:

Originally posted by BISCUT:
If anyone gives a damn, I ordered it yesterday and after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

And I'm looking to go 22" completed barrel length.

Man, I love rifles!!!!!

Just realized that post sounded like I was being an ass!! Wasnt the intention....

quote:

Originally posted by BISCUT:

quote:

Originally posted by BISCUT:
If anyone gives a damn, I ordered it yesterday and after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

And I'm looking to go 22" completed barrel length.

Man, I love rifles!!!!!

Just realized that post sounded like I was being an ass!! Wasnt the intention....

Another part of the equation here (if anyone can stomach it) is: what is satisfactory accuracy to one, may not be to another. Unfortunately your 1:10 with a 22" barrel won't have the ability to stabilize the length of a 200 grain bullet for what I would call "satisfactory accuracy" regardless of what you were told. "Completed" or rather finished length will only leave you with about 19 inches of travel. Will it work? Yes, if you're not going for precision accuracy. It will however, shoot quite good with short surface bullets in the 150,55,65 range.

Regardless of all said, I hope this does just what you want. You couldn't of picked a finer cartridge! The .308 has been doing the job on deer, elk, black bear, boar and everything in-between for over 50 years. I'm sure it will shoot good for you...Good luck..

And all this time, I was thinking that the only detriment to accuracy a shorter barrel may cause, is due to the center turning process. The bore being more centered towards the ends. Where if cut back to 20" for example, the barrel muzzel amy not be as close to center.

The barrel maker must have just lucked out with my two 9.3s (9.3x62 and 9.3x57) when they cut the barrels to 20", because they are very accurate, just like the one with a 23" barrel. Hummm.

I'll have to inform them just how lucky they are, that I'm so satisfied with their barrels, after all, and dispite the obvious flaws.

And my 458 with a 20" twist rate, in a 20" barrel, just barely making one revolution as the bullet passes through the barrel, counting slippage and all. It's a wonder that big 458 slug isn't hitting the target on the back side. Even if the slug is backwards at 100 yards, what do I care? It's still making 1" to 1.5" groups.

I think I'll get some 45 cal round lead balls, so it won't matter which side hits first.

KB

I have an old Savage that Mark Lammers (LOSOK) retro fitted a decent barrel from a donor --- nitrided it and cut it down to 20" and its a 308.

I must be expereincing a fluke....because she prints well under MOA 5 shot groups with 165-200 and does it with AB, BT, SGK, Interbond, and most recently 200gr GameKings.

WhatThe:

Oh and just for grins, maybe you can figure this one out? The military uses the M40/M24 .308 (7.62X51) sniper rifle. As we all know, it's a modified version of the model 700. In any event, it uses a unique rifling in that the risers/groves are NOT 180 degrees opposing. This is because those risers/groves are radial cut to a finish of 5-in & 5-out @ 65 degrees as opposed to normal 90 degree conventional cuts. Here's the question: Other than fouling and the obvious POI increase, why is the radial cut pushed at a rate of 1 RPM over 11.25" using the Sierra 175 Gr. MatchKing bullet in a 24" barrel?

Becuase when the M40 concept was adopted the "old" shooters who were running the program were still of the opinion that an 11" twist was "best" for LR shooting with the 7.62/.308W. This was based on using the 180 gr MK for 1000 yard shooting out of M14s at 2450 fps. The Sierra 175 MK or the lighter 168/175 VLDs had not yet been produced. Thus M40/M24 has the twist for a bullet that saw little if no use in either rifle.

I've the ability to actually measure a bullets BC and TOF with a M43 Oehler PBL. Having tested numerous bullets through 10, 11, 12 and 14" twists including several M24s (Army's M700 sniping rifle) the 168 - 175 VLDs and the 168 and 175s always give shorter TOFs and higher BCs in 12" twists. Compared to the 10" vs 12" twists with the 175 MK to the tune of as much as .475 to .525 BC comparison. That makes a considerable difference in drop and wind drift at 1000+ yards. Also the higher the BC a given bullet has means it is more stable and will be more accurate, especially as range increases.

Larry Gibson

quote:

Originally posted by WhatThe:

quote:

Originally posted by wistrapper:

quote:

How long?

22"............1:8

24"............1:9

26"............1:10

Could you explain why a 1:8" twist would be any different in a 22" barrel than in a 30" barrel. Isn't 1 rev per 8" the same regardless of barrel length?

I'll ask you... I have a TC/custom 357 Mag hand gun with a 10" 1:8 twist barrel. You have a 357 Mag bolt action rifle with a 20" barrel with the same rate of twist (ROT). For this query, we are going to be shooting the same bullet and load. 158 Gr. SP in front of 16.5 Grs. of H-110. Both weapons are "viced" in a universal block allowing no movement during pre-shot and post shot.

Which in your opinion is going to be more accurate and why?

I am not wrapping my head around your theory.

My 45 ACP uses a 1 in 16" twist out of a 4" barrel and that seems contrary to your philosophy regarding twist vs barrel length. I always understood it as a factor of bullet length vs diameter as having the most to do with twist selection and the barrel length has very little to do with it.

What you are saying is that the greater the twist the better the stability for a given barrel length regardless of bullet shape, so a longer barrel wouldn't require as much twist because the barrel has more time to impart its forces onto the projectile.

Correct me if I this is not an accurate paraphrasing.

Bullet length decides twist rate not weight or SD. Example a 220 grain 30 caliber round nose bullet does not need as much twist to stabilizes as would a 220 grian spiter. The pointed bullet is longer but maintains the same weight and SD.

Twist rate is independant of barrel length. Velocity plays a part in the amount of twist needed. Example is a 220 grain SMK bullet that does not stabilize in a 12 twist 308 win will in a 30-378

quote:

Originally posted by WhatThe:
I put the question in reverse in a hypothetical in hopes it would stand on it's own. In any event, to give you some idea in why you want to increase the "ROT" (rate of twist) in a shorter barrels is a multi-answer senerio, so I will leave bullets and their surface area out although it plays an important role, it will reduce a chapter in my explanation. To begin with many people believe that the propulsion starts in the chamber/case and ends in the chamber/case. This is NOT true. Depending on the "RBC" (reactive burn rate) powder continues to burn in the barrel. This of course causes expansion to the barrel which leads to greater "slip" across the lands. To prove this fact all you have to do is watch a high speed video of a bullet leaving a barrel. You will notice that gasses in the form of grey smoke exiting prior to the bullet. Timing of these gasses is a ballistic tool rarely talked about however, prove that gasses are passing the bullet and slip is in fact an issue. When you see a flame coming out of a "cold" barrel, this indicates the use of a slow burning powder and perhaps ignition. In any event, it is the tell-tail sign of major slippage. Of course it is normal for hot barrels due to existing expansion. With that, many people feel that the projectile engages the rifling groves right away and follow the rifling the length of the barrel. Again, this is NOT true otherwise concentricity (how straight the bullet lies within the case and its alignment with the barrel) would not be of concern. To think that the bullet follows the rifling in its entirety would lead to major slowing of the projectile. As we know, this is not true as well. Heavy barrels to reduce expansion have shown us all that; reduction of slippage and gas escape have provided great improvements in accuracy. This is more proof. So lets say that you have a 20" barrel and 1:10 ROT and after you developed your load you determine that your bullet travels 4 inches before engaging the groves and that your slipage equals 1/2 turn every 10 inches. What is your "true" ROT and will that provide enough in flight RPM's to stabilize your projectile?

Since the invention of long guns, it has been a well established fact that a longer barrel provides better accuracy and velocity. The lenght provides stabilization while at the same time the lenght allows all the propellant to burn putting more gas/pressure behind the projectile leading to faster velocities. So should you wish to have a shorter barrel, you must increase the ROT to provide for the lack of "grab" due to slippage and to increase the "in flight" RPM's of the bullet due to the lack of velocity you would get in a longer barrel.

When all is said and done here, I am NOT a good teacher nor do I always explain things as well as I wish to. But I do hope this brings some light to your question.

The power of the internet - is to cause otherwise intelligent people to pause and contemplate BS.

Occasionally we find absolute proof of the theory of over-education, and over-thinking something.

KB

quote:

Originally posted by Gundog 64:

quote:

Originally posted by BISCUT:
If anyone gives a damn, I ordered it yesterday and after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

And I'm looking to go 22" completed barrel length.

Man, I love rifles!!!!!

Wise choice Grasshopper. You will be happy with your decision.


P.S. This has to be one of the weirdest threads I have ever read here.

1-10 twist is what I would have gone with as well

quote:

Originally posted by BISCUT:
If anyone gives a damn, I ordered it yesterday and after a lengthy discussion with Hart Rifle Barrels I went with 10 twist to ensure I could properly stabelize the 200 grainers.....

And I'm looking to go 22" completed barrel length.

Man, I love rifles!!!!!

IMO you just made a fine decision!