Bullets fragment in flight

[Bart B.]

Sierra had at least two incidents of jacket failure at rifling grooves in bullets.

One lot of their 30 caliber 168 grain HPMK shot 2750 fps or more from 1:12 twist 7.62 NATO barrels. About half would fly apart around 50 yards away; a few much closer. I saw the dirt clouds from a couple at about 20 yards. Embarrassing for our team as those Mexican Matched M80 rounds were all we had for short range. Sierra replaced those the USN Rifle Teams used in Garands. The US Army Rifle Team kept theirs that failed with M14NM rifles as their International Team's 300 meter free rifles shot them about 2200 fps in reduced loads with exceptional accuracy.

When Sierra's 7mm 168 grain HPMK came out, some barrels conventional rifling in 7mm Rem Mag engraved them enough they flew apart from long, 1:9 twist barrels with max plus powder charges. Obermeyer 5R rifling solved the problem. Sierra was able to get better quality jacket material that led to better quality 26 and 24 caliber HPMK long, heavy bullets.

 

[Beau]

An 8 twist is way too fast for the 55 Blitz. I was blowing them up in a 9 twist at about 2,900fps.
That Sierra recommendation of <=3,600 probably assumes a 12 or 14 twist.

 

[jk80]

I had the same thing happen with 50 Hornady super explosive bullets in a 220 swift. They worked outstanding in a 222 and I thought they'd be awesome in the 220. Turned out not so much! A call to Hornady let me know I should have read the little slip of paper in the box saying not to push them past 3600. I knew something was up when they were leaving what looked like vapor trails until a little puff of smoke like in the above post. Lol

 

[searcher]

Contrary to Beau's experience, a few days ago, I was shooting the 55 Blitz Kings (moly coated) in a 1-8 twist barrel at 3,400 f.p.s. in my .22 Nosler. No problems of bullet blow-ups.

 

[headhunter1111]

I have a .22 cheetah with a 7 twist. It blows up 55gr bullets regularly. With an 8 twist I would recommend loading down or shooting heavier bullets. Might as well enjoy the benefits of higher bc’s. 80gr ELDs are mean on varmints, 68gr match kings are also a great bullet.

 

[msinc]

The lead is not going to reach the melting temperature of lead, 621.4 degrees F, in the fraction of a second of barrel and flight time prior to disintegration.

A bullet that is overspun disintegrates due to centrifugal force. There may be other precipitating factors like jacket damage but the function is disintegration due to centrifugal force.

I agree on the heat. Centrifugal force is not the only culprit either...had a buddy with a 220 Swift {1-in-14 twist} and it disintegrated Hornady 50 grain SPSX bullets. I guess it was the speed. Those bullets are definitely not for that caliber. He didn't know and he didn't tell me the day he used my range for sight in what they were. At 100 yards the target was not even touched, at 25 it looked like it was shot with fine lead dust. Actually it was.

 

[Zero333]

Worked up a sweet load with 80gr Berger FB in my 8" twist 243 in the middle of the winter.

Shot so damn good I was very happy.

Once the temp went went up to around 30 f I had missing bullet holes at 200 meters and at 100 meters the groups were not as good as in the deep freeze temps.

When the bullets fell apart in mid air it was noticeably audible that something is not normal.

 

[snert]

Nothing like watching that beautiful grey streak thru the scope headed right for a groundhog and then seeing it veer way off like the space shuttle in a puff...

Seen it with Sierra blitz and Speer HP's run real hard in 22-250 and Swifts. Cool to watch, irritating to miss.