twist rate on a 257

[greyling22]

I have an older semi custom 257 roberts improved I bought at a pawn shop a few years back. I have never had stellar accuracy with it, using reloads with heavier (100grn and over) bullets. I started thinking about twist rate recently, so I measured mine as best I could and came up with 11.5", which is a bizarre twist unless it is supposed to be 1:12. {(minimal markings on the barrel. The only marks are "257AI" on the top and "5 28 69 ES" on the bottom (may 28, 1969 ER Shaw?)} It's an old gun, a first gen savage action.

Now from what I can determine to shoot that weight of bullet I should be using a faster twist rate. That's fine, I can shoot lighter bullet if need be. The bullets hitting the target are impacting square, no keyholing or signs of tumbling. If I switched to a lighter weight bullet, say something 75-90 grains, in theory, should my accuracy improve?

Basically am I using bullets too heavy for the twist rate?

and here's a picture because, hey, we all like pictures.

 

[rcmodel]

Yes, I would try lighter bullets.

Typically, the .257 Roberts used a faster 1/10" twist rate.

1/11.5" or 1/12" would be unusually slow, and maybe built for light varmint bullets.

rc

 

[Riomouse911]

I agree, too slow for the longer bullets. My 721 Remington loves 100 gr, HATES 117 gr bullets.

 

[GooseGestapo]

My E.R.Shaw bbl'd .257Roberts has a 1/10" twist. It's a "standard" barrel and was produced by Shaw in 1983 pre-threaded for M98 Mauser. Barrel designation on bottom is similar to yours.

However, a 1/12" could be ordered.
If it's shooting "ok" with 120gr Flat-base bullets, no problem..."minute of deer" is adequate for hunting. For varmints, it's where you'll want better accuracy. Evidently the rifle was built with varmints in mind.
However, even my 1/10" shoots excellent with 75gr bullets.
Even if it dosen't shoot the 100+grain bullets suitably, the 100gr Nosler Partiton kills as well as the heavier ones.
Even Roy Weatherby preferred 100gr bullets in the .257wbymag for large game.

Is it indeed a LEFT HAND ACTION or is the picture reversed?
If you decide you want a different barrel, the Savage M110 action is easy and economical to rebarrel.
But, I'd try the 90gr Sierra Blitz King bullet. It works for deer as well as varmints. It's on my "list" of bullets to try in my .257Robt and .257wby.
Also, try some different powders. I had a Ruger M77MkII that was "particular" about bullets and powders. For some strange reason it liked IMR3031. With 38.0gr and 100gr Hornady Pt.Spt. it was MOA accurate at 3,000fps. My Shaw "gags" on that load, but is "normal" in that it really likes IMR4350, H380, H414, and H4831, and especially IMR4831 with 115gr Berger VLD. I doubt that your 1/12" twist will shoot the Berger, however....

 

[rcmodel]

If it ain't a left handed action, the scope turret windage dial is on the wrong side too.

rc

 

[dprice3844444]

what is the receiver make,model,serial? once you find out when it is made,you can contact the maker for the info.if it's a custom job,there should be a control number on the bottom of the barrel by the maker.

 

[greyling22]

It is indeed a left handed gun. No makers mark, so I think it's probably a home built custom rig. There are a fair number of guys in this area that do that back in the day. They're mostly dead now unfortunately. I think it's got a fajen stock. it's a savage 110 action, however, the barrel is threaded directly into the receiver and the bolt does not have the typical floating replaceable head, so if I decided to rebarrel I'd have to get a new bolt and magazine as well as barrel and barrel nut. Still, not a bad find in a pawn shop. Came with dies, about 100 pieces of brass, and a denver redfield 2-7 wideview scope for 470 or so in 10 years ago dollars. I bought it instead of my aggie ring for graduation.

accuracy isn't horrible, 2-3" at 100yds, but I think it could certainly be better.

 

[scottishkat]

Try the attached rate of twist and bullet weight chart it sounds like 100gr will be difficult I note that 1 in 12 stops at 85gr.


http://www.opticstalk.com/what-twist-rate-for-which-bullet-weight_topic19347.html

 

[stringnut]

The twist indeed may be marginal. However , I noticed that you refer to it as a 257 Roberts. You do state that barrel is stamped 257ai. This is an improved cartridge. You can fire factory ammo, or , reloads made with regular dies but the accuracy may be iffy. With all custom guns make sure what the chamber is for sure.

 

[greyling22]

I'm shooting fire formed brass that was neck sized. And I have ackley reloading dies. (2 sets, the rcbs that came with it and some lee dies. I like the lee a lot better. the rcbs sizing die was tilting necks.)

 

[Zeke/PA]

If it ain't a left handed action, the scope turret windage dial is on the wrong side too.

rc

So is the cheekpiece!

 

[NCsmitty]

Flat based bullets are easier to stabilize in slower twist barrels than the boattail versions. The 257AI will help with it's extra velocity potential too.
That's a nice old rifle to have around to play with.


NCsmitty

 

[savanahsdad]

Rifle Magazine has an article on the .257 Roberts Ackley Imp. this month (May #274) with some load data , might help ,I haven't read it yet , just got it today

 

[greyling22]

awesome. thanks. it is actually available as the downloadable sample article from rifle mags website. I must be living right.

 

[savanahsdad]

awesome. thanks. I must be living right.

me too my friend your welcome.

 

[Jim Watson]

12 twist was usual on the smaller .250 Savage which came out with 87 grain bullets. There was also a 100, but I bet it was rather blunt.

I can't say for sure that a lighter bullet will be more accurate, but it won't be hard for you to find out.