max fps in 20 twist ?

[charger 1]

If a fella were shooting a 380-390 grainer with 70-75% contact out of a 1-20 twist 458 bore, provided his boolit is of quality,balance,hardness,lube,etc etc ,what would be the reasonable fps limit in above twist?

[Bass Ackward]

If a fella were shooting a 380-390 grainer with 70-75% contact out of a 1-20 twist 458 bore, provided his boolit is of quality,balance,hardness,lube,etc etc ,what would be the reasonable fps limit in above twist?


I assume you are theoretical here. Because it isn't simply about rifling contact. Meplat size plays a big part in how much weight isn't pulling it's load. The more bullet weight that is unsupported, the lower the limit of that design. But base pressure is going to kill before rotational forces in smaller case designs.

So let's say you are running a 460 Wby and can get the velocity without the pressure, then you could possibly reach 2600/2700 fps with WDWW? Softer and that comes down. Extend the bearing length and it goes back up some. If you make one with taller rifling, then you can go softer or raise the limit.

So the only one that can answer in your specific case is Professor Gun.

[Larry Gibson]

If a fella were shooting a 380-390 grainer with 70-75% contact out of a 1-20 twist 458 bore, provided his boolit is of quality,balance,hardness,lube,etc etc ,what would be the reasonable fps limit in above twist?

Bass is correct. Given just RPM limit on accuracy a 1-20" twist is upwards of 2900+fps as a limit. But as Bass said there are other factors and they are going to limit the fps. I have shot a 385 gr (linotype) 458483 GC'd bullet to 2400+ fps out of my Siamese Mauser 450-400-70. It has a 1-22" twist. In my case the limiting factor was recoil and case capacity. My rifle weighs just a tudge over 8 lbs without the scope and I was shooting 3 shot groups of 3" or so with the reciever sight. Recoil was fierce off the bench and I stopped at 2400+ fps because that was all the "fun" I could stand.

Larry Gibson

[jhalcott]

I got to 2300 in my Siamese Mauser with a pointed 405 gr bullet.Then I leaded the stock to 15# total gun weight.I STILL kept the velocity below 2000 fps though.