wboggs
Gold $$ Contributor
Very well thought out article.Keeping with the theme of blowing up bullets...After many years of shooting I have blown up a few bullets! 223/223AI, 6PPC, etc...shooting light bullets with fast twist as we all know it can happen. 50-55 gr ...60-65 gr...all at 3400-3600 and fast twist (1:7), my friends and I have blown up many. The consensus amongst us became bullet spin rate. With the calculation of velocity x 720 divided by twist rate...we all decided that once rpm is above 300,000 it starts to become anybody's guess. I've also seen lightweight 308 bullets blown up with fast twist. This may not be the reason here and very well could be rifling. Rardoin will probably confirm that for us. With what can be gathered from these posts...allow me to put together this compulation.
In getting the info out to us ShootDots has plenty of reason for concern...look at the rpm from these shooters.
ShootDots...blew up....2930...7.5 tw...281,000 rpm
Park Ranger..............2780...7.5 tw...267,000 rpm
SWD....coated bullets..2800...7.0 tw...288,000 rpm
Longrange57.............2940....8.0 tw...265,000 rpm
Rardoin....................2950...8.0 tw...266,000 rpm
1shot.......................2960...7.5..tw..284,000 rpm
2980....7.5.tw...286,000 rpm
3100...7.5 tw...298,000 rpm
wboggs...................3100...7.5 tw...298,000 rpm
tzaun......blew up.....2845...7.25 tw...283,000 rpm
bbarber25...............2745...8.0 tw....247,000 rpm
If I missed something or made a mistake...please forgive! With the fast twist barrels, we are closing in on that magic 300,000 range where anything can happen with excess heat and maybe a barrel thats tighter than another one. It very well could be barrel and rifling, but I would have to conclude that we are also closing in on the spin rate threshold for this bullet. Some may handle 300-320,000, others may not! To the contrary I've also seen some very small calibers shoot at 340,000 with no known problems....but probably not in competition! This thing has got us all scratching our heads because the last thing I want to do is have it happen in a match....especially on the very last shot! That would make me ill!
I shot some 5 shot groups today, 5 shots in 5min, then 3min cool down. Outside temp was 88 F and mv was 3116. Barrel did not get extremely hot under these condition. No bullet failures to date with about 75.bullets fired. Not exactly match conditions but apparently I am on the edge with rotational velocity.
The bullets are accurate, grouping just under 1" at 300. I will try to slow them down to the 2900-2950 range and see if they are still as accurate as the 3100 load.
Bill