Taper Crimp vs. Bullet Diameter?

[BT Sniper]

This cannalure grove has really got me thinking. I don't think I shall offer my bullets with the grove untill I can apply one without the diameter increasing.

So on to my question... I have shot severial hundred of the 44 cal made from the 40 S&W brass without appling a crimp grove. I do apply a very firm tapper crimp to the loaded round though. I must imagine that in the process of appling the taper crimp I am increasing the diameter of the bullet around it as well, just like the problem I am having with the hand held cannalure tool. Yet pull the trigger I do with no noticable problems.

What is your guys thoughts on this subject? Anyone else use a taper crimp die on bullets with no crimp grove?

Thanks,

BT

[blaser.306]

I use one all the time ! .38 super 124 gr. plated rn. ( no canelure) .45 acp 230 gr "j" word thingy no grove , I think it applies more to a heavy roll crimp than a taper . Just my .02

[sagacious]

So on to my question...
I do apply a very firm tapper crimp to the loaded round though. I must imagine that in the process of appling the taper crimp I am increasing the diameter of the bullet around it as well, just like the problem I am having with the hand held cannalure tool. Yet pull the trigger I do with no noticable problems.

What is your guys thoughts on this subject? Anyone else use a taper crimp die on bullets with no crimp grove?

Thanks,

BT
I have consistently found the exact opposite to be true. A strong taper crimp applied to a jacketed bullet will invariably reduce the diameter of the bullet at that location. I've seen it many times. Test it yourself: apply a hard crimp a non-crimp-groove bullet and then pull it and measure. Usually one can see the deformation by eye. If there is a dimensional change from applying a firm taper crimp, it'll be to reduce the diameter of the bullet. Note though, that excessive crimping when there is no crimp groove can certainly cause the case mouth to bulge outward slightly right below the crimp. That causes less case mouth tension. One can also easily test that effect to his own satisfaction.

Pressing the cannelure groove into a jacket, and crimping a case, must be considered as fundamentally different actions. Pressing the cannelure groove causes brass to flow, and some of it flows to the sides of the groove. Crimping a case mouth causes no metal flow in the bullet jacket beneath, and thus it simply compresses the bullet at the location of the crimp.

I do not apply a strong taper crimp to jacketed bullets with no crimp groove. Most reloading books advise against it for the reasons listed above, and it may well cause a varying distortion or dimensional change in the bullet. Proper case neck tension is much more important, and should be enough to secure the bullet. In the instance of 44cal bullets formed from 40SW cases, the case neck grip on the long bearing surface has always been more than adequate for me.