Guys, 

I'm not that great at math so I don't even try to use the Greenhill method of working out bullet lgt to bore & twist ratios. Would like some help with this one if any of you are so inclined to help the math handycaped. 

My rifle is a Stevens 44 in 25-20 SS. The twist rate is 1 turn in 13" for sure, I've measure it 3 time just to make sure. Some shooters of the 25-20 SS tell me that they get their best accuracy up around 1550 to 1600 fps. So my question is -->What is the max bullet lgt that a 1 in 13" twist will handle accuratly with in the speeds that it can be pushed with a cast bullet in the Stevens 44? I plan to shoot a taper bullet that will be breech seated. 

Purchased a Hoch 258/105 mold from CPA in hope that the bullet it cast will shoot well in this rifle. Plan to start the test firing this Monday with IMR4227, AA#9, and Rem 1 1/2 sm pistol primer and Fed 205M primers. Any suggestions?

                         Thanks, Sendaro

Do you know the exact groove diameter. Believe it or not a couple thou can have a big impact when your playing close to the edge.

Seanmp, Have been told that the groove dia. is .257 by a reliable sorce that I sent 3 slugs to for measurement.

                       Sendaro

John forget the math and the opionons, shoot it and see how it does and you might be plesently suprised. What works at your altitude and air density might not work for me and mine and vice versa. Only the target will tell the truth the whole truth and nothing but the truth.

JLouis

That is exactly what I would do.

Just for discussion there is nothing wrong with twist rates that are just barely stable. In fact in top level benchrest shooting they are using twist rates which are even lower than what is considered average stable. A stability factor of 1.5 is the norm but they will use factors as low as 1.2 in benchrest. This gives the bullet the best chance of "going to sleep" and minimizes all of the various gyroscopic effects.

For example my partner and I developed a 30cal airgun barrel that has a 26" twist. It's designed to shoot a specific rebated boattail cast bullet. In theory it is barely stable but it is so accurate that it has become one of TJ's best selling barrels. In fact it's so popular that one of the major US airgun companies tried to steal it and make it and the bullet design proprietary. However we gave the mold design to Accurate and it's listed in their catalogue and I leave my mandrel designs at TJ's for common use and by doing so we thwarted their attempts.

Jeff, Thanks for the suggestions. Working at getting to the shooting house this AM. Will let you know how things work out. It's going to be a very busy week. We have the NYS IBS Score Championships this weekend at the Pine Tree Rifle Club. I've a great crew of members to run it, but there's a lot of details and things to do. 

Seanmp, Where would I look to find more information about the 30 cal air rifle youmention?

                               Senaro

Jeff, Tried the IMR4227 8 grain load you suggested and had good results. Didn't have time to finish the testing today. It did well at 100 yards and at 150. However it is tipping at 200 yards. Looks like I need to go up with the velocity a little and maybe the tipping with stop. Will be testing in that direction. Velocity was running 1340 fps at 10 feet in front of the muzzle. See test target attached. The Hoch 258/105 was pan lubed with JSL from CPA. Bullet breech seated so that lands cut half way through base band. 

                       Sendaro