180 Gr Lead and Longshot

[Taterhead]

Both Rainier and Berry's have moved the velocity down to 1250fps btw.

Thin copper plate and soft lead core, at 1300+fps in a 1:16 twist barrel is a pretty hefty RPM. There is a guy on the Cast Boolits forum who has a very interesting study into the "RPM Threshold" and how it adversely effects cast bullets. It is very possible, the bullets are spinning themselves apart. Any imbalance in a soft core like that is going to magnify that imbalance even more at higher velocities. 1375fps for a bullet that was not meant to go above 1250fps(realistically 900-1050fps since it is meant for a .40sw) is a big jump.

A soft hollow point varmint bullet shot from a 22-250 at 4000 fps can come apart. Swaged lead not going to rip apart at service caliber velocities and twist. lead is frequently shot from carbines under much more abusive conditions than a service pistol can bring. I have reproduced the precise conditions that you describe where a plated bullet seems to vanish.. Almost certainly, if you were to move the target distance in by 10 yards, you'd see indications of tumbling. Now I agree that there is an imbalance due to copper becoming displaced.  But the effect will be a tumbling bullet. It isn't going to tear apart by RPMs. 124 gr 357 mags run lead bullets at that velocity and twist all day long.

[control_the_trigger]

I don't have my exact velocities with me, they are at my parents house.  I went up to 9.5 gr LS with 180 gr lead sized at .402 in glock 20 sf, glock barrel, with 22 pound spring and saw no pressure signs.  OAL 1.26.  I like 9.2 grains of LS for 180 XTP and decided to stay with that for the lead as well as my range load currently.  Velocities for the lead were 10-20 feet per second faster then the XTPs if I recall correctly at various charges.  I can post the data when I have the exact numbers.  At this point Longshot is my 10mm powder, the only powder I would like to test is BE-86 (and I do have some) to compare velocities and flash with Longshot with 180 xtp.

[Ryushin]

X-Treme's 180gr Heavy Plate Concave Base Flat Point is supposed to be good to 1500fps.

My plinking load is:
Powder: Longshot   
Pistol: Kimber Eclipse 1911
Barrel Length: 5.00"
Primer: WLP
Bullet: X-Treme 180gr HPCB RNFP   
COL: 1.260"
Powder Charge: 9.30gr
Temperature: 83
10 Shot Group: 1251 Low, 1305 High, 1278 Average

Very, very accurate.  Less then 12" at 100 yards.  No signs of primer flow or any other signs of high pressure.