77 TMK Spinning Apart?

[dårlig jeger]

Was out shooting prairie dogs with a 22 creed and 77TMK over 44gr superformance. With the heat, I had some shots go from 3400 where I had the load to 3550. This is a 7.5tw 26" barrel. I calculated about 340k rpm at 3550fps. No pressure signs on Peterson 3x fired brass.

The fast shots were almost making a ricochet type zipping noise as soon as they left the barrel and veering wildly off target, 10+ feet. No evidence of baffle strikes in a 30cal can.

I've never been around bullets spinning apart, is that what they sound like or do? I guess imagined they just went "pop" and didn't make it to the target.

Another guy was shooting them at 3350 and 320k rpm with no issues. Is there a known limit in rpm for tmks beyond the numbers Sierra uses?

 

[rayporter]

a rough [ or uncleaned throat] can cause jackets to degrade and bullets to disintegrate.
a new barrel can shoot some bulldts while one with a few hundred rounds on it can have problems.

 

[Nine Banger]

The bullets that I have seen disintegrate look like a puff of dust from a few inches in front of the barrel to a few feet in front.

Like a genie disappearing.

55s out of a 22-250 1:8 pushing 4000fps. Hot barrel, low altitude, nearly 100% humidity.

 

[wind gypsy]

Is there a known limit in rpm for tmks beyond the numbers Sierra uses?

I haven't seen anything suggested. I know hornady has referenced 300k rpms but really it seems like it's a cocktail of a number of factors - engraving forces of a given bore config, how rough the lands are, barrel length, and velocity/rpms.

Your barrel length and velocity/RPMs is working against you for sure.