Yeah, I think I can get to 3200 with the nitrided barrel. The throat spec is .3085 x .200 with a 1*30 angle. The 230's barely fit in the 3.820 mag box about .010 off the lands.
In making the 230, Berger kept the same nose and tail as the 215, only lengthened the bearing. I think Berger tried to cram as much bullet in the Hybrid design as they could and make it work in a 10 twist. At our elevations they work OK, but I've read some other reports that guys were having some stabilization issues with them in a 10 twist. Using worse case inputs like 0 degrees temp and 0 pressure altitude @ 3200 fps, the Berger twist calc gives an SG of 1.33 which is marginal for terminal performance. With more normal inputs like 20* and 3000' altitude, the SG goes to 1.55 which is perfect. Upping the velocity to 3400 fps only boosts it to 1.58 I'm finding out that velocity doesn't have a huge affect on stability, whereas temp and altitude do.
So bottom line is, to make a hybrid style bullet in a 250 gr would require a 9 twist. Heck, I would like to see them do a 260. I would consider 30/338 LM Imp build for that.
When Richard Graves still owned Wildcat bullets we talked about a new bullet for a possible 300 Allen Magnum. As most of you know, there is not a 300 Allen Magnum in the stable here at APS. That is not entirely true, there is a 300 Allen Magnum reamer, its simply the 338 AM necked down to 30 cal. Being based on the 408 CT parent case its a HUGE case capacity.
Working with Richard, he sent me some simply AMAXING 290 and even 300 gr ULD RBBTs in 30 cal. These things looked like pencils they were so long. In testing the 300 AM, it was a serious pain in the rear to be honest. We were testing these in 1-7 and 1-8 twist barrels and at lower velocities the bullets were shooting OK. 1 moa or so. But pressures were so low that velocity spreads were terrible and the WC872 powder we were using was burning like wet coal!!!
As we upped pressure, we ran into the problem that these bullets were so long, that the forward portion of the bullet would engage the rifling and begin to rotate but because the bullets were so long and heavy, the rear of the bullet would resist this rotational force and the bullets, in my theory, were being wrung like a wet towel. This really weakened the core jacket bond and accuracy went south or there was total bullet failure. We know this because we found several partial bullets down range that were only the OGIVE of the bullet. They had ripped from the body of the bullet where the ogive contacted the bore.
We saw this in lesser calibers as well (107 gr .224 cal). Richard was going to fix this by ordering custom jackets that had a heavy tapered jacket that was roughly 0.070" thick at the base, roughly 0.050" at the body/ogive and then tapered to 0.030" at the meplat. To top things off he sent me some with aluminum tips installed. These were so long that I never even shot them, did not have a barrel that would keep them on point.
Soon there after, Richard sold his business and the heavy tapered jacketed bullets never got off the ground.
When you get a bullet to a certain length, lead core/cup jacketed bullet anyway, it seems that you run into many other issues that you would never expect but slap you right in the face anyway.
I have still not given up on the 300 Allen Magnum, perhaps someday we will have the right combo of bullet and powder that could handle the velocity potential of this wildcat but for the time being, its not practical.
