I looked back at some of the reading I was doing and figured out that I was thinking of a similar (but different) issue between a lot of these new “shove a smaller diameter bullet in a fatter necked down case” trends. So I was slightly off, PB.
The .224 Valkyrie has been plagued by a number of barrels being too slow in twist to stabilize the heavier 90gr projectiles at the velocities they are pushing it. Someone smarter than me on SH commented that the .224 Valkyrie was a great way of breathing life into dead inventory of “match grade” 223 barrels.
Many manufacturers took their old inventory and re-chambered the dead stock of 1:7 .223 barrels with the new reamer for .224 Valkyrie and suddenly they had a new hot product on their hands; but this resulted in a lot of .224 Valkyrie barrels floating around with insufficient twist for the .224. JP put out a memo even acknowledging this:
“Dear JP customer,
If you are receiving this email, it means your current order for one of our JP Supermatch™ barrels in .224 Valkyrie is eligible for fulfilment in our first production run. But, because of the unforeseen complications of developing barrels for a brand new caliber like this, we wanted to contact you before completing your order.
After final testing of these barrels, we have discovered that accuracy specific to 90gr. Sierra Match King and the 90gr. Fusion hunting ammo is only mediocre. These results are not up to the JP standard, and as such, we cannot honor our accuracy guarantee with this 90gr. ammunition.
However, the Federal varmint load using the 60gr. Nosler Ballistic Tip and our personal test loads using 77gr. Sierra Tipped Match Kings shot well from these barrels. With the 77gr. Tipped Match Kings, we achieved maximum velocities in the 3000 ft/s range. This compromise of utilizing lighter projectiles with much higher MV and slightly lower BC may actually result in higher hit probabilities within the effective range of the cartridge. This is particularly the case with unknown distance targets.
At this point, we want to offer you the choice of confirming your order and receiving one of these first JP .224 Valkyrie barrels. Alternately, you may opt to wait for our next run of barrels with further design changes to improve the performance of the 90gr. bullets. The choice comes down to your choice of application and ammo.
Please respond to this email with your preference.
If you choose to wait, your order will still be fulfilled in the order it was received as soon as the new barrels arrive and are tested. If you choose to wait, we expect to ship your order sometime in May.
Sincerely,
JP Customer service team"
and for what it’s worth, the post I was confusing myself with about the jackets spinning off of bullets is from the 22 Creedmoor, where they are pushing 90gr bullets to 3000+fps, exceeding the 300k RPM threshold and disintegrating bullets in mid air
Similar issue seen here:
//youtu.be/07tseYJUvHA