60 question

[3rd Gen Neal]

Hi everyone..happy Memorial day to you all. My question is probably as tired as the 'ol "+p's in my 37?" deal but...I recently picked up a 60-7 thats in pristine condition and finally got a chance to fire it yesterday. For the first time ever I ran into bullet tumbling. I cleaned the bore before I went to the range and was firing some Monarch 158gr semi jacketed hp's that I had fired through a dffnt m60 with no problems. What is the cause of that? I guess try dffnt ammo obviously but Id hate to think I can't use 158gr. Thanks for the help with a rookie sounding question, though Im far from a newbee...just never encountered this.

[alwslate]

I have a 60-7 and two 37-2s all with 1 7/8 " barrels and have experienced no problems using 158 gr cast bullets in handloads. I can
only offer a guess. You didn't say at what distance you were from your
target but I would suspect your problem is related to low velocity and
a jacketed bullet.

[KEN L]

I would suspect the ammo. Try a couple of different brands, I believe you'll find your culprit! If Monarch is reloaded ammo, it could be undersized projectiles. I don't think underloaded ammo would necessarily tumble, but if not engaging the rifling properly then tumbling would occur.