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rsterne
I received my 4-cavity Mould from Al a couple of days ago, and had a chance today to cast the first bullets…. It took me a while to get the right temperature, the long skinny bullets were somewhat wrinkled until I got the mould hot enough…. I did some with 1% tin and some with 2.5%, and I think the higher tin content worked better…. Here is a photo of the mould, in a Lee 6-cavity handle….
This is my first NOE Mould, and I was delighted at the quality…. The bullets dropped at 100.7 gr. in 1% tin and 100.3 gr. in 2.5% tin, and I couldn’t measure any difference in size…. The back of the nose ran 0.2575-0.2585″ and the driving band about 0.002″ larger, just like it was designed…. The center portion measures 0.246″, so it shouldn’t drag on the lands…. Here is a closeup of some of the 2.5% bullets….
I was pretty picky when I sorted the bullets, and threw about half back into the pot for next time…. but I got enough bullets of each alloy to allow me to test in my Monocoque, once I get the chamber machined…. Here was what I ended up with….
I’m really looking forward to testing these…. They certainly look like they should have a great BC….
Bob
rsterne
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davidgoldstein
I been talking to Lloyd about a build. He ran the calc’s and seems the difference between 3000 and 3500 psi is roughly 40fps in this particular build.
Still throwing some idea around. I have a couple of spare TJ barrels laying around. Obviously the 1:14 won’t work to well for such a long/heavy .257 slug. We are talking about 100-120gr bullet in a 30″ 1:10 barrel at 3500 psi. Can probably push it to 3700 if I go with a UK spec 500cc bottle, or we briefly talked about a 4K disco based gun. The problem were running in to is “barrel whip”. Even sleeved, and tensioned, accuracy is not quit sub moa at 100 yards. At least not in with my .257 Brod or .30 brod bullet shooters. Shortening the barrels has helped a bit but growing very frustrated with these dang .257’s accuracy. Starting with Benji based guns seems to have some major disadvantages to the AirForce guns, which have are reporting much better accuracy. Hope all my ramblings make some sense. Thanks
Dave
I’m not positive that even the 101 gr. will stabilize in a 10″ twist, which is why I had Mike at TJs make a 7″ twist mandrel…. Long stiff barrels are a challenge, you need to chat with Tofazfou (Cedric) and rifle50 (Carl) or possibly dyotat100 (Doug)…. They seem to have the long barrels figured out…. My personal choice would be a 1/2″ liner inside a 3/4″ OD (1/8″ wall) Carbon Fibre sleeve, with the sleeve mounted inside the receiver for at least 2″…. or the scope mounted directly on the barrel…. Trying to use an MRod breech is problematic, IMO, there is little benefit to making a super-stiff barrel and hinging it at the front of the breech on a 1/2″ stub secured with a couple of setscrews….
Bob
Doug Noble is the guy to talk to for that…. He is having a lot of success with the 85-92 gr. bullets in .257 cal around 3400-3600 psi…. long barrels, of course….
BTW, I did get to test these bullets in the 7″ twist, 33″ long barrel…. At 4000 psi, the 98 gr. HP hit 1003 fps, and the 113 gr. FN managed 950 fps (219 & 227 FPE respectively), so the 7″ twist is not an issue…. Detuned about 50 fps, at 3800 psi tethered, I am hopeful they will be good performers, plan to test that this month….
Bob
davidgoldstein
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