Does this look like a good fit?

[Marlin Junky]

I'd rather the mold cast a shorter, lighter boolit; however, it doesn't appear possible to get a better fit without going custom this and custom that.

If there's anyone out there who owns an RCBS 257-120-SP, what's the dimension from the base to the top of the leading lube groove?

What is the length of the leading band?

QuickLoad says this boolit is 1.1" long, is that correct?

Will it be a pain to limit run-out with this combo?

Can all that boolit length be stabilized down to 1700 fps with a 10" twist?

Thank you...
MJ

P.S. I don't have the rifle yet, that's why I supplied a SAAMI drawing.

[45 2.1]

I've never got that one to produce sterling accuraccy in the three 25-06s i've owned. I always had to seat the front body band almost all inside the neck to get it to fit. The only commercial mold that has given me sterling accuracy (5/8" three shot groups at 100 yd.) is the Lyman 257312 sized 0.258" out of 50/50 Pb/WW useing Unique. Good luck if you try it........ most 25-06s have short throats unless they're burned out.

[Marlin Junky]

........ most 25-06s have short throats unless they're burned out.

We'll I was going to get a new barrel for an H-R (yeah, I know... don't say it :D) and assuming it has a SAAMI chamber, that .105" long cylindrical freebore might fit the front band of RCBS nicely. I was also considering a .243 barrel but according to SAAMI, their throats are configured somewhat different:

.243 Chamber:

[Tom Myers]

I'd rather the mold cast a shorter, lighter boolit; however, it doesn't appear possible to get a better fit without going custom this and custom that.

If there's anyone out there who owns an RCBS 257-120-SP, what's the dimension from the base to the top of the leading lube groove?

What is the length of the leading band?

QuickLoad says this boolit is 1.1" long, is that correct?

Will it be a pain to limit run-out with this combo?

Can all that boolit length be stabilized down to 1700 fps with a 10" twist?

Thank you...
MJ

P.S. I don't have the rifle yet, that's why I supplied a SAAMI drawing.


MJ,

I scaled up a drawing from an R,C,B,S, image and came up with the dimensions shown.

If the bullet( or just the front band ) is sized to .257 and the chamber is to specs, it should be a good fit.

The bullet length scales to 0.990 inches plus 0.010 for the gas check thickness makes it 1 inch long.

The math shows that the minimum muzzle velocity for this bullet is around 1834 fps.

Hope this helps.

http://www.tmtpages.com/LinkSkyImages/forum_images/25-06%20Remington/R.C.B.S.%20257-120-SP.jpg

http://www.tmtpages.com/LinkSkyImages/forum_images/25-06%20Remington/R.C.B.S._Mold_257-120-SP_119_gr_Sketch.Jpg

http://www.tmtpages.com/LinkSkyImages/forum_images/25-06%20Remington/25-06_Remington_SAAMI~R.C.B.S._Mold_257-120-SP.Jpg

http://www.tmtpages.com/LinkSkyImages/forum_images/25-06%20Remington/Draw.jpg

[grouch]

According to the old formula, probably not.
Grouch

[Marlin Junky]

I've never got that one to produce sterling accuraccy in the three 25-06s i've owned. I always had to seat the front body band almost all inside the neck to get it to fit. The only commercial mold that has given me sterling accuracy (5/8" three shot groups at 100 yd.) is the Lyman 257312 sized 0.258" out of 50/50 Pb/WW useing Unique. Good luck if you try it........ most 25-06s have short throats unless they're burned out.

45 2.1,

Were all your 25-06's chambered with a SAAMI reamer; i.e., one made after Remington standardized the 25-06 in 1969? I can't understand from the drawing (from an ANSI document) why that throat would be considered short. It looks like a .258" boolit would snug up in there nicely for just about the length of an RCBS 257-120 leading band.

MJ

[45 2.1]

Were all your 25-06's chambered with a SAAMI reamer; i.e., one made after Remington standardized the 25-06 in 1969? New Rugers and a single Winchester. Wish I still had the Winchester. It looks like a .258" boolit would snug up in there nicely for just about the length of an RCBS 257-120 leading band. None of them would take it until half the front band was in the case neck.

[Marlin Junky]

45,

Thanks... is the actual length of RCBS 257-120 closer to 1.1" as QuickLoad indicates?

MJ

[45 2.1]

45,

Thanks... is the actual length of RCBS 257-120 closer to 1.1" as QuickLoad indicates?

MJ

Right now I don't know. That mold is put away and the remaining lot of boolits are gone downrange.

[x101airborne]

I will be watching with much interest. I have not loaded cast for my wifes 257 roberts, YET!

[runfiverun]

the picture that tom put up is what things are supposed to look like.
i am finding more and more that a shorter boolit seems to work better.
one with only the two driving bands, at least in the newer rifles.

[Marlin Junky]

the picture that tom put up is what things are supposed to look like.
i am finding more and more that a shorter boolit seems to work better.
one with only the two driving bands, at least in the newer rifles.

Yes, shorter to a point... high SD boolits are harder to shoot accurately at high speeds... probably due to increased inertia. I will stay away from RCBS 257-120 if it can't be driven to 1900 fps from a 10" twist accurately using 4759 in the 25-06. A smaller cartridge case full of medium to medium-slow powder would probably prove better but I'm not ready for a custom rig just to shoot targets and varmints with cast boolits. Muzzle blast is also a consideration on a 40 acre parcel with neighbors 1/4 mile away.

What's puzzling to me though is even if RCBS 257-120 weighs 125 grains ready-to-fly, it would have an equivalent SD to a 180 grain .30 caliber projectile. A 10" twist in a .25 caliber bore is equivalent to a 12" twist in a .30 caliber (in terms of pitch angle). Add the aerodynamic profile of RCBS 257-120 into the "equation" and you should have a combination (assuming compatible chamber dimensions) that would shoot well from 1700 fps to beyond 2000 fps and remain stable for at least a couple hundred yards.

MJ

[runfiverun]

it should and looks like it would, i have been on the fence of what to try in my 25's. i like the idea of the rcbs mold you show up there, but i have had no luck in many of the newer rifles with the longer bodies.
stuff like the saeco 248 in my ruger, and the identical rcbs 22-55 sp have proven to fit right nicely and have given me near jaxketed velocities with accuracy on par with the rifle.
i keep looking at that mold and say to myself if only the nose were a bit shorter, and that last drive band were gone.
it would be ideal in the 25/06's and bobs around here. two of one and three of the other.