Speed FPS

[Allen in MT]

Shooting Hornady 75gn BTHP with 23.4 gn of Varget in a 7.7 twist 26" Bartlein 223 varmint barrel and avg 2845. This speed is over what max loads are showing with more powder. At what point if there is a point is this to fast or a barrel burner.

 

[Varminterror]

There’s not an inflection “point” where barrel life suddenly gets worse as long as you’re not seeing a significant pressure/velocity spike in your velocity curve.

It’s a Bartlein and it’s 26”, it should be about 250fps faster than the 20” Hornady book data. The 75 BTHP tends to run a little faster in my experience than the other 73-75’s in the Hornady book, then 223rem tends to pick up about 40-45fps/inch of barrel, and I expect any Bartlein to be as fast as any published data, if not a touch faster. Max load of 23.5grn Varget shows 2600 in the 10th, you’re .1grn from max, and 6” longer - being 250fps faster sounds perfectly normal to me.

 

[Strat Rider]

I've heard the RPM limit for any bullet should be 288,000. I assume over this speed the bullet jacket would warp or fly off.
2850 fps on a 7.7 twist is 266,494 rpm. You are getting close. 3,080 fps on that twist hits 288k

 

[Varminterror]

I've heard the RPM limit for any bullet should be 288,000. I assume over this speed the bullet jacket would warp or fly off.
2850 fps on a 7.7 twist is 266,494 rpm. You are getting close. 3,080 fps on that twist hits 288k

Really strange that my bullets still find the target running 298,000 rpm out of my 6 creed. 7.5 twist running 3103fps. Even more strange that my 223rem running 3200+ (even 3400fps in older long barrels) in 7” twist barrels hitting 329,000rpm can find their way to targets in one piece too.

........

 

[Strat Rider]

Those are some pretty impressive numbers.
What weight projectile in a 7" twist will hit 3200 fps accurately?
I'll modify that spreadsheet.

 

[Varminterror]

Those are some pretty impressive numbers.
What weight projectile in a 7" twist will hit 3200 fps accurately?
I'll modify that spreadsheet.

A 50grn 223/5.56 will top 3200fps out of a 20” tube, and blow 3200 out of the water if you give it a 24”+ pipe to play in.

All kinds of data out there for 1:8” twist 6mm Creed shooting 55grn bullets at 4000-4150fps, that’s over 360,000rpm.

The 288,000rpm is an arbitrary (largely BS) construct, not based in any reality. Some bullets are documented to come apart even at 240,000rpm, some are documented as good to go clear up over 350,000.

I’ve shot over a hundred thousand 50grn vmax’s over 300krpm in 7 and 7.5” barrels, if they wanted to come apart because they were over 288,000, I’d have to think I’d have noticed when at least one of them would have. Just in the last month and a half I have put 400 6mm 105 Hybrids onto targets out to 1,000yrds, all of them spinning over 297,000rpm. Doubt they’d make it to 1,000yrds and hit 2moa and smaller targets if they were coming apart out of the muzzle - and I’ve pushed these bullets up over 3200fps, which puts them over 300krpm, and I know guys shooting them from 1:7’s at these speeds - over 320krpm.

Bullet weight, diameter, jacket thickness, alloy, and rifling depth all play a part in bullet integrity, and tolerance for centripetal force (dependent upon rpm). The red herring 288krpm is a (poor) rule of thumb meant to keep varmint shooters from blowing up high speed, thin jacketed frag’ers. Some of these come apart even lower, TNT’s, for example, if I recall correctly are sub-250krpm, and Sierra Varminters are something like sub-225krpm.

Some bullets will obviously tolerate a lot more than others, and blindly stating 288,000 isn’t of much value.