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differnce in 1-8 and 1-8.5 twist 6.5 barrel

C

Crotalus

Sergeant
Full Member
Minuteman
Feb 4, 2008
146
12
36
Santa Rosa, Ca
Is there much difference in a 1-8 twist compared to a 1-8.5 in .264 cal? I intended to get a 1-8 twist for my built, planning to shoot high BC bullets like the 140vld's, scenars, ect.

However when the rock creek group buy rolled around I really wanted in on a barrel. The 6.5 barrels were only available in 1-8.5twist. I assumed they would be fine...... will it shoot the heavier bullets?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

Not much. Only .5.
wink.gif
Sorry couldn't help it.

Either will work with 140s. Quite a few members use 8.5s here with the different 6.5mm cartridges.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

haha, thanks. I thats what I thought I just couldn't figure out why people would pick one over the other?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

I have 1-8.5" Pac-Nor for my 6.5 CM, and nope, haven't had any problems...
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

You will be very happy with a 8.5 twist. I shoot a 260 with a Kreiger 8.5, using 142gr Sierras, its a drill.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

I have an 8.4 twist Obermeyer on my 6.5x47L and it shoots the 142 sierras with no problem.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

ok sweet! Has anyone ever shot any of the 160grn 6.5 bullets? will they stabilize?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JDF_GSP</div><div class="ubbcode-body">I have an 8.4 twist Obermeyer on my 6.5x47L and it shoots the 142 sierras with no problem. </div></div>

Same barrel but on a 260, I have run berger's, smk's, lapua and hornady 139-142 weight bullets and no issues.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

My 8.5 twist sends the 139,140,and 142s like a laser out of my .260. I would only consider the 8 twist if I were shooting in 10 degree weather a sea level all the time. Call Terry Cross or Robert Gradous and ask them if a 8 twist is necessary. I did.... and that's why im shooting an 8.5.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Not much. Only .5.</div></div>
i was about to wite a paragraph, but you sum'd it up.

the 1-8 would only slightly increase your stability factor over the 1-8.5.

Send'em.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

I have tried both and NO noticeable difference with a 260 and 6.5-284 and 139-142's. A 1/9 can work well too.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

I am kinda in the same boat, while there might not be any diffrence, if they were the same price and the same weight, same everythying, is it still smarter to go with the 1:8?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

I've been looking at this real hard as well and everyone has told me 8.5tw is fine including Moon at CC who's doing my build.

According to the calculations in Litz's book and Shooter in order for the conditions around here to get to where I can't shoot out of the 8.5tw, i'm not going be outside anyway.

L
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

kind of off topic, but this is something that i've wondered a time or two.

if one bullet is spinning at a much higher RPM than another identical bullet, at the same speed.... will the bullet with the faster spin hit with more energy? Say on a soft target? I could be wrong, but in my head I imagine a fast spinning bullet boring into a soft target more easily, then expanding/twisting/shredding.

basically just wondering it the bullets RPM has any effect on ballistics/bullet energy?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Crotalus</div><div class="ubbcode-body">kind of off topic, but this is something that i've wondered a time or two.

if one bullet is spinning at a much higher RPM than another identical bullet, at the same speed.... will the bullet with the faster spin hit with more energy? Say on a soft target? I could be wrong, but in my head I imagine a fast spinning bullet boring into a soft target more easily, then expanding/twisting/shredding.

basically just wondering it the bullets RPM has any effect on ballistics/bullet energy? </div></div>

to test that would require a very wide span of twist rates like on a .223 from 6.5-14, even then I do not think a difference could be seen - in ballistic gelatin the wound channels seem to run pretty straight
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Layton</div><div class="ubbcode-body">I've been looking at this real hard as well and everyone has told me 8.5tw is fine including Moon at CC who's doing my build.

According to the calculations in Litz's book and Shooter in order for the conditions around here to get to where I can't shoot out of the 8.5tw, i'm not going be outside anyway.

L </div></div>

This plays into what I asked right above you.. People are saying "its Fine", but why wouldnt you go with a 1:8, what does going 1:8.5 get you that 1:8 wouldnt? Like, what are the Pro's and Cons of each, why would someone choose one over the other?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

Trade off. FPS vs stability? And people just think they have to go with a faster twist I guess. I did until I started asking around and doing the math myself based on MY expected shooting conditions.

Side note: I was going with a 9tw on my 338 until the guys at Bartlein and Moon told me to stay at 9.5. So i did. And the math works out fine for just about anywhere in NA.

L
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: REL1203</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Layton</div><div class="ubbcode-body">I've been looking at this real hard as well and everyone has told me 8.5tw is fine including Moon at CC who's doing my build.

According to the calculations in Litz's book and Shooter in order for the conditions around here to get to where I can't shoot out of the 8.5tw, i'm not going be outside anyway.

L </div></div>

This plays into what I asked right above you.. People are saying "its Fine", but why wouldnt you go with a 1:8, what does going 1:8.5 get you that 1:8 wouldnt? Like, what are the Pro's and Cons of each, why would someone choose one over the other? </div></div>

Because he got a 8.5 barrel in a group buy. The 8.5 will work. So will the 8 twist. I have an 8 on my 6.5 Creedmoor. I like to err on the side of caution and get a slightly faster twist. Same reason I won't use anything slower than a 11 twist on my .308s and prefer a 10. I know it will stabilize the bullet no matter what the conditions. Doesn't hurt anything being a little faster. You won't lose FPS between a 8 and 8.5 and both will stabilize a 140grn bullet.
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: REL1203</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Layton</div><div class="ubbcode-body">I've been looking at this real hard as well and everyone has told me 8.5tw is fine including Moon at CC who's doing my build.

According to the calculations in Litz's book and Shooter in order for the conditions around here to get to where I can't shoot out of the 8.5tw, i'm not going be outside anyway.

L </div></div>

This plays into what I asked right above you.. People are saying "its Fine", but why wouldnt you go with a 1:8, what does going 1:8.5 get you that 1:8 wouldnt? Like, what are the Pro's and Cons of each, why would someone choose one over the other? </div></div>

Because he got a 8.5 barrel in a group buy. The 8.5 will work. So will the 8 twist. I have an 8 on my 6.5 Creedmoor. I like to err on the side of caution and get a slightly faster twist. Same reason I won't use anything slower than a 11 twist on my .308s and prefer a 10. I know it will stabilize the bullet no matter what the conditions. Doesn't hurt anything being a little faster. You won't lose FPS between a 8 and 8.5 and both will stabilize a 140grn bullet. </div></div>

This is kinda what i assumed was going to be the answer, so given the choice between the 2, same brand, length, make, length of time to wait, its really a toss up in .260?
 
Re: differnce in 1-8 and 1-8.5 twist 6.5 barrel

Id' guess (and someone correct me if I'm wrong) that the 8.5 twist might possibly be a carry over for 160gr bullets and the 6.5x55mm or the 6.5x54R (or any of the older 6mm cartridges like the Navy Lee and such)?

Kind of like 1-9 twists for .17's (not too long ago, the only twist available), based on the 17 Rem (as nobody was shooting 30's at slower speeds to warrant a faster twist made by the manufacturers for the greater shooting community ).

Just guessing here...
 
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