I need a little help on barrel twist

[wchartz]

I have a 260 with 8.5 twist that shoots Lapua 139s great. It will not shoot accurately the following; SMK 142, Berger 140 VLD, Hornady 140 AMax. The general difference is .25 MOA for the Lapuas and .75 MOA for the others. I detect no keyholeing on the targets. The AMax states 7.5 twist on the box. I do not know if the twist is really the reason the other bullets do not group well. The chamber was cut with what PTG calls a Lapua reamer which has a neck diameter of .298 and a freebore of .088. I do not know if there is any other difference from a standard reamer. Anybody out there have any experience on this?

 

[TGagnon]

Re: I need a little help on barrel twist

I have several 6.5 caliber rifles and the only one with an 8.5 twist is my grendel as it shoots the lighter bullets anyway. Give the 130 bergers a try as the 260 can push them fast enough to give the 140 class bullets a run for the money. Don't get to hung up about not being able to shoot the heaviest for caliber bullets as there is always heavier out there. I have a bag of 155 grn VLD style bullets I am waiting to try in a 6.5 twist swede. Look like pencil stubs.

 

[RugerSlinger]

Re: I need a little help on barrel twist

I have a 19" 8tw that loves the 140gns and my 28" 8.5 loves the 123gns. They both Shoot everything .5 moa but the 8tw will shoot .25moa with the 140gn and the 8.5 shoots the 123s .25moa. No key holing at 300 with either, haven't taken them out further yet.

 

[swampbuck]

Re: I need a little help on barrel twist

I wouldn't woory about it. Maybe the twist is too slow, maybe the rifle just likes the Lapua. Who cares? .25MOA with 139 ain't nothing to sneeze at. Lock those dies down and go shoot.

 

[wchartz]

Re: I need a little help on barrel twist

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Swampbuck</div><div class="ubbcode-body">I wouldn't woory about it. Maybe the twist is too slow, maybe the rifle just likes the Lapua. Who cares? .25MOA with 139 ain't nothing to sneeze at. Lock those dies down and go shoot. </div></div>
The reason I care is because of the cost and sometimes the lack of availabilty of Lapua. I plan to shoot this rifle a lot.

 

[Brutas]

Re: I need a little help on barrel twist

What are you using for seating depth for the .75 moa bullets?

 

[wchartz]

Re: I need a little help on barrel twist

I set them back .015-.060 from lands. The Lapua shoots best at .062 setback.

 

[rifleman700]

Re: I need a little help on barrel twist

Its definately twist. If you were shooting at a higher altitude you can get away with the heavier bullets and the 1-8.5 but at lower / denser altitude you need a 1-8. Shoot an email to Berger Bullets and they can explain it in detail.