i have a question for ya. i have one each of the 257 Roberts and 25-06 Rem. my intention for both of them was to shoot 115 or 120 grain bullets. one rifle has a factory barel and the other has a Shilen. both barrels have a 1:10 twist. this is the factory standard twist for both rifles. yet i find that at 200 yards, i have trouble keeping a 4-5 inch group. i looked at a Greenhill Calculator and entered the required data and it says i should have a 1:8 twist to stabilize the heavier bullets. this would certainly account for the spread out groups.

but...........why in the heck would Ruger, Remington, and Savage all use a 1:10 twist for these 25 caliber rifles if the 1:10 twist won't stabilize the 115 grain bullets? after all.....the only cartridges manufactured today for the 257 Roberts are 115 or 117 grain and the 25-06 has several loadings up to and including 120 grain bullets. according to the Greenhill formula, the best i can hope for is to use a 100 grain bullet.

do any of you have this similar problem??

My 250-3000s and 257s all have 10" twists and handle 115-120 grain bullets just fine to 300 yds and beyond. How big are the groups at 100 yds?

At Roberts and 25-06 velocity, the 1:10 should have no problems with 115-120 grain bullets. What type of scope set-ups do you have (including bases & rings)?

A minute amount of play can result in larger groups at longer ranges.

Your problem may be within the bullet selection or the powder charge if you reload. If you don't reload, your gun may simply just not like that load you're trying.

Hard to figure I have 3 .257's, 2 25'06's and 1 250 savage all with 1:10 twist. All shoot very well with 117-120 bullets. Have you tried 117 sierra 117 flat base bullets, they are the shortest pointed bullet and the 117 hornady round nose is the shortest.

The shelin twist calculator says 1:8 for 120's but I just ordered a 3 grove from Lilja and they recommended a 1:10.

Bill, you are on the right path. The 10" twist is marginal for long bullets in the 1/4 bore. It works most of the time, but....I got a Bob that won't shoot 115-120 grain Partitions fer crap. Loves the shorter stuff though. If you want to use some of http://wildcatbullets.com/ very long bullets you'll wind up with an 8" or even a 7" twist IIRC, but for the garden variety 115-120 grain bullet a 1:9 is good.

Bill,
I've been thinking the same thing.There are now a lot of premium 110-120gr, long bullets in .257,when I get around to building a new roberts, I'm going to use a 1-9" twist.

Bill-over the years I've used a 10 in rounds from the Bob to the Roy and most inbetween.

I've always found them to shoot the 75's to the 120's with no problem!

I kind of think there is another issue here than twist.

I honestly can't imagine a 10 not shooting those slugs.

Mark D

the groups at 100 yards are normally between 1.0 - 1.5 inches.

the scope is a Leuplod VX-II, 3-9x40. the mount is a Tikka mount. the rifle itself is a Tikka.

the ammo i am using is Remington. personally, i never had really good luck with Remington, but this seems a bit unusual.

i bought some Hornady Custom ammo for the 257 and have not yet tried it. i'm hopeful that the different ammo might make a difference. if it does, i'll try the same thing for the 25-06. i really don't want to have to get into reloading for these particular rifles. thanks for the help.

Scope Paralax may be your problem. Check it out.