December 11, 2008, 09:30 AM
Hi, I have been reloading a few months, getting comfortable with the routine and seeing (anecdotally) good results. But the other day after a few hours with a gunsmith I was told that my taper crimp was not good enough. He wrote like a doctor would write a prescription the outside diameter at the throat for a good crimp.
I have been getting all my edumacation from Speer #14 and this site, and I thought I was crimping well. When I got back to my bench and checked, sure enough the factory loads were in the range the good Dr. Gunsmith prescribed. Nowhere could I find among all the pictures and words in Speer #14 the dimensions for a good crimp.
Are there better sources I can get a hold of that would cover this? The gunsmith I visited is amazing, and a wealth of knowledge, but I'd like to get a nice hard copy source for all the "tricks" for other calibers. Any suggestions?
December 11, 2008, 11:09 AM
The cartridge case drawing in your loading manual gives you the SAAMI spec for outside case mouth measurement.
Use that, or just a frog-hair more.
All the taper crimp is supposed to do is straighten the case mouth bell back out straight, plus a hair more.
There actually is no exact way to say what your measurement "always" should be, because it all henge's on the brand of brass you are using.
Some brands may have thicker necks then other brands.
December 11, 2008, 12:52 PM
I agree with RC. The SAAMI spec on the 9mm is .380" right at the end of the case. If you try to measure this, the 9mm case is highly tapered, so only place your mic or caliper on the last 1/32 of the case.
Most people generally agree you'll end up with about .002-.003 smaller than the .380 dimension. If you have doubts about this, measure some factory loads.
I find the best way for me to test my crimps is when cartridges will fall into a 9mm cartridge gauge all the way using only their own weight. 9mm chambers vary so much, you really can't use your gun for this test. I highly suggest getting a cartridge gauge; it makes a nice Christmas present.
December 11, 2008, 01:14 PM
What the gunsmith told me was .373 to .375. Speer does show the .380, and factory loads are around the .375, just as the gunsmith suggested. (The gunsmith did bring the chamber of my one troublesome pistol up to spec. The man is amazing, so I can always go back to him for the right combination of load-specs to pistols for my other firearms.)
The reason I was asking for a good resource was when I start doing .40S&W and .45 ACP I'd like to know what to do with them as well. I think the best thing to do is just measure factory loads and follow their lead.
December 11, 2008, 01:35 PM
Those numbers sound good. Remember, as RC alluded to, we're discussing a "range of crimp", not a SAAMI spec number. Remember also that the 9mm and 45ACP head space on the front of the case. If you get too small, the cartridge will go too far into the chamber, and we don't want that.
I like to crimp until the cartridge will fall into the gauge. Then I extract the bullet and check to make sure I'm not leaving a ring around the bullet's waist. A ring generally indicates "over crimp". If you're in that "range", then I'd say you were doing really good.
December 11, 2008, 02:05 PM
I shall be asking the Elves for a few different caliber cartridge gauges! Thanks again, all.