257-112-FN (Bob’s Boat Tails)

Looks interesting Al! Only problem I can see, is that in .257, the weight, and twist requirements. There are a LOT of .257’s out there, and almost all of them are 1-14 twist.

Can’t see having a custom barrel made for all those people just to test the new bullet.

Perhaps a shorter one? You already know the accuracy I am getting from My .257 and your Ranch Dog 80 GR and the fp spititzer mold I got from you. but I had to deck the mold to 81 grains for my gun. It is now a superb bullet. In fact, I will be sending it to Eric for his magic, just as I did the RD mold.

My .257 is more powerful than most, so If I need less weight, it may very well be the norm.

KnifeMaker

There are lighter .257 cal BBT designs on this board, 65 gr., 78 gr., 90 gr. and 100 gr…. I have read the statements that fast twist rates lose a lot of velocity, but the math certainly doesn’t support that…. I have also seen statements by other long range shooters that the velocity loss is minimal…. I think the jury is out on that…. A custom mandrel to make a 7″ twist .257 barrel is $300, find me 2 more guys and I’ll put up $100 towards it…. Then anyone who wants one can get it for the price of a regular TJ’s barrel…. Then we can find out for sure just what the difference in velocity is….

This bullet has the highest BC of any Bob’s Boattail I have designed, except for the .308 Whiteout, which was designed to make use of the added power of Helium…. This bullet requires less twist, relative to caliber, than the Whiteout, because it has a 20% lower SD…. Just a few months ago, if you told somebody that an airgun could duplicate the ballistics of the .300 AAC Blackout, they would have called you crazy (and did)…. but now it is reality…. I personally think this bullet is capable of winning the next EBR, and using AIR, not Helium…. Hey, sometimes dreams become reality…. 

Bob

I have been down the twist rate path on my way to developing a long range air rifle. In .30 caliber I started with a 1 in 14″ twist. That ended up being an expensive mistake. I was shooting the RCBS 165 gr. Silhouette bullet and the RCBS 180 gr. bullet. Both turned out decent groups at 100 yards. But at 200 yards and beyond obvious oblong holes started appearing on the target. And the oblong holes were the hits on the paper that tended to open up the group size. Thoroughly disappointed with the way the rifle was shooting I had the rifle rebuilt for a 3rd time. I ordered a 1 in 10″ twist match grade Shilen stainless steel barrel and had Brent at Extreme Big Bore airguns fit it to the rifle. Many nay sayers said that I would suffer velocity loss from the faster twist rate but this was never measurable. Some bullets shot 10 to 15 fps slower but others actually shot faster in the 1 in 10″ twist barrel. The point is that I can’t be sure that I set the regulator exactly the same each time I set up the rifle. I try to regulate at 3800 psi. But is it actually 3750 psi? Is it 3850? Who knows. Were both barrels the exact dimensions? I.E., .308″ inch grooves and .300″ inch lands.  The 1 in 14″ twist was a T.J.’s. Were both chambers cut exactly the same? The Shilen is also 1 5/8″ longer than the T.J.’s barrel was. So there are lots of variables besides just twist rate when comparing the two barrels. Bottom line–I could detect NO significant change in velocity when I went to the 10″ inch twist barrel. But all bullet instability problems disappeared even at ranges to 700 yards. My best 10 shot group is currently at 5.1″ inches at 300 yards so I have been very pleased with the accuracy of the 1 in 10″ inch twist barrel.
        As far as a group buy, it would never work for me because the chamber that was cut in my rifle measures .3104″ inches. My best accuracy has been with a cast bullet that was specifically modified by Mr. Ohlen to fit the .3104″ chamber. What I will probably do will be to take Bob’s 172 gr. 1 in 10″ inch twist design and have a custom bullet mold made for my rifle. I’ll have the 2 driving bands cut at .311″ and the cylinder shaped portion of the bullet (the area between the 2 driving bands) increased to .301″ so that I get a bore riding effect out of this portion of the bullet. This should provide greater stability for the bullet’s path down the bore without creating a lot more friction. I would also shorten the cylinder shaped portion of the bullet by about 1/10th of an inch to get the weight into the 160 to 165 gr. range.
          When I get out to shooting long range my biggest challenge is always the wind. And the measured B.C. of my best bullet is only .249. So any improvement in the B.C. should translate into greater long range capability. I think Bob’s on the right path.

This bullet is critical to my .257 Monocoque PCP project, so if you have any interest, please post in this thread…. I’m in, obviously….  :

Can it be done with a Lyman style HP pin in one cavity?….

Bob

I am making an appeal to any that want to try this bullet to PM me…. I need to get this going NOW as my .257 Monocoque PCP project, which is designed around this bullet and the 102 gr. is getting to the point I need some ammo to cut the chamber and test it…. The 7″ twist barrel needed to handle them is now available from TJ’s….

http://noebulletmolds.com/smf/index.php/topic,1219.0.html

If you have any interest in getting a mould for this bullet, please contact me ASAP…. I am looking for guys to share the $200 cost of the tooling to make this bullet available….

Bob

HI Dave….

This bullet will require a 30″ barrel and 3600 psi minimum to get into the 900s, and it needs a 7″ twist…. TJ’s made a mandrel for me to the appropriate specs, and it is available from Mike…. The last thing I heard from Al, they were having trouble making tooling to machine the moulds, even the lighter 100 gr. was problematic for them, only a few moulds exist…. I would suggest you put your name on the Group Buy, the more interest there is, the more incentive NOE will have to work on getting the tooling to work…. This bullet and my Monocoque PCP were designed together, and I plan on running 3600 psi in the 33″ barrel, but I’m willing to go to 3800 if necessary, and the gun is safe to 4500…. Basically, we are working with unknowns here to some extent, this is leading edge stuff….

Bob

Any chance this could be made in a HP version?…. It would be acceptable to push the Meplat back to a 0.125″ diameter in doing so…. I think it would expand the use of this bullet from just target work to long range Varmint hunting….

Bob