Bullet Tumbling


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putteral
November 24, 2007, 12:59 PM
Got back from the range yesterday and noticed on the target that the some of the bullets appeared to hit sideways. Was shooting 9mm 147gr LFP with 3.5grs of Tiegroup. What could be the cause of this? Any advice appreciated.

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rcmodel
November 24, 2007, 01:10 PM
Your pistols rifling twist too slow to stabilize that heavy a bullet at reduced velocity.

Titegroup is too fast a powder to get good velocity out of a 147 grain bullet.

You need to switch to a slower burning powder to get more velocity in order to stabilize those long bullets in your barrel.

Try Power Pistol, or Blue Dot, or Unique.
Any of those powders will easily give you another 100+ FPS more velocity.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

putteral
November 24, 2007, 01:14 PM
Thanks, I have some power pistol and unique on order.

Morgan
November 24, 2007, 04:07 PM
Titegroup is not, in my experience, too fast for 147gr 9mm (hell, I've even used Clays).

I agree that velocity is the issue - bring it up a bit, and the tumbling will go away.

Make sure you're running the OAL as long as possible, and watch for pressure signs.

rcmodel
November 24, 2007, 04:14 PM
But he is already over maximum with his 3.5 Titegroup load, according to my Speer manual. They list 3.3 as a maximum load with a 147 bullet.

I don't think he can "bring it up a bit" from where he is already at with Titegroup powder.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

alucard0822
November 24, 2007, 04:29 PM
while not a terrible load for a 147gr jacketed, it might be a tad hot and fast for lead, is the barrel leading badly? I have seen some hot and heavy lead loads that tumble in an auto with shallow rifling, where they are perfectly accurate at lower velocities with the same powder, or sometimes even at higher velocities, in front of a slower powder. what are you shooting this out of?

putteral
November 24, 2007, 06:45 PM
I started out using 3 grs of Titegroup with similar results. Not every bullet tumbled but probably about 1/3 did. Have not had any major leading . I am also shooting 122gr LFP's with 4 grs of Titegruop without any problems. I shoot a Ruger KP95

alucard0822
November 24, 2007, 07:40 PM
that is quite odd, most 9mms I have dealt with have a 1:14 or so twist rate, ruger states on their website the kp95 has 1:10, should stabilize, no problem, if bullets are concentric and not an undersized batch (I once got a bag of 100 win bullets where all measured at .353, the rest were .355) , and they are actually keyholing, not just tearing the paper funny, then it is a conundrum.

jmorris
November 26, 2007, 10:31 AM
There are many in IDPA and USPSA that use 3.1+-gr Titegroup and a 147gr to make the power factor. Also, many use VV-N310 with good results and it’s even faster. So, are you shooting lead out of a polygonal rifled barrel? If so try a jacketed or plated 147gr. Have you tried more or less crimp? Over crimping often is the cause for 147’s tumbling. There are many out there running 9mm 147’s between 850-900fps every weekend, so you can do it, stick in there and you’ll figure it out.

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