Nice. With that twist I'd definitely try the 170 grain PVA Cayuga, G7 bc of 0.375. I ran the 151's in my 7Max, amazingly accurate. I tried the 170's but couldn't stabilize them in an 8.0 twist, your 7 twist would probably work.
Super Fast Twist Barrels for Hammer Bullets
- Thread starter nksmfamjp
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TAD it is
"We settled on 1:3 twist, although probably 1:2 is optimal, but with 1:3 all the commercial copper solid bullets and bonded bullets we tested stayed together and with the 1:2 some of them came apart out of the barrel," Brittingham says.
In short- the gyroscopic stability tables are good for the big solids- you would lean towards 2.0 (or more?).
Have you seen any argument against overspinning the solid bullet?
Skidding during the initial contact with the rifling?
I ask that, not in argument but from expensive experience (twist rate). We built two rifles based on claimed twist requirements (tables and by email) only to have both of them fail on the solids (shoot jacketed lights out). Only to find the limited number of competitors were shooting a twist value 1.5points lower than book values. Expensive lesson.
Also - please chime in- shooting ultra long distances (way past transonic) if you are down range you can here the differences in the bullets stability. Bullet Amfg sounds like a bubble bee, bullet Bmfg sounds like a fly. The only way to make that noise is nose gyration. You also find the ballistic solvers are... well ... +/- a couple of hundred yards. Not that we can expect them to take into account what is happening at max ordanance of 1500-2500ft.
Not sure, but I can confirm that the advertised bc of the 151 at 0.310 checked out with my drop data out to 600 yards and shot sub 1/2 moa.How does the 170 Cayuga have a higher BC than the 185 CE Laser…..
If the mfg suggests minimum twist rate of 1/9, and you can get a barrel with 1/8, I'd lean in that direction. I've tried some mono's that were recommended for the twist rate that I have confirmed on my barrel, that would not stabilize. Have had others that worked out fine. With that in mind I'd lean toward faster is better, but there's likely a point of diminishing returns.
Thank you.
This was a .375cal and the book said 9T but needed 7.5T. A 9T key holed at 100yds. Interestingly- Bartlein can shoot the bullet at 7.5 well. They cannot shoot others (anecdotal minimal stats- 8barrels). Two other barrel mfgs could not shoot the bullets in question but can shoot the bullets the Bartlein cannot. When asked we recommend the barrel to the bullet. Could be a minor subset or bore details are having an effect.
Does anybody know the spin decay over time/distance leads vs solids? My little mind says the less dense bullet will decay faster.
My little mind agrees
Now I know where all the H4350 is going.
I find this interesting and watching.
Stay tuned, more to comeNow I know where all the H4350 is going.
In my rifles I generally use the H powders, and I have plent of H4350 and H4831SC on hand. I finally got a lbs of H-1000 and Retumbo. I haven't tried them yet.
Now watching for prices to come down. It's moving downward.
Which would require a second stability calculator or different target values. I have two shooters shooting large calibers who have bipods break from the torque of the round. Well at least coincidently- same side. Just an indicator, and they are shooting big solids of more than one brand during testing.
Perhaps we can get a few shooters to note their twist rates per bullet/grain for solids and compare it to lead.
The guys shooting Hammer rounds seem to have it down pretty good.
RockyMtnMT
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I don't know that we have it down. Like a lot of this stuff it becomes a "feeling" you develop over time with success and failure. We learn more form failure than anything. I can say that the stability calculators are flawed, IMO. Particularly the longer for caliber a bullet gets. The calculators are only calculating ballistic stability. This is different than terminal stability. A marginally stable bullet can fly quite accurately but it will likely have a higher incidence of failure on game. What we have figured out is that calculating ballistic stability at sea level for a 1.5 sg is a good consistent calculation for minimum twist for good terminal performance. We consider it a "minimum" and more twist is a good thing. Guys that are hunting at sea level in cold temperatures should choose a bullet with higher stability. Again, the longer for caliber a bullet gets the more critical this gets. Short for caliber bullets don't seem to care. They just work.
