Measuring the taper crimp

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Measuring the taper crimp

Post by LenV on Mon Sep 07, 2015 10:25 pm

Has anyone else noticed how stinkin hard it is to measure your taper crimp on your .45? I get out the loop and light and use my calibrated eyeball to just barely measure the very tip of the case and then I get a different but close reading every time with the calipers. I have given this some thought and taken a lot of measurements and I have developed a method of measuring my crimp that my old eyes can do and get repeatable results.
  To make a long story not quite as long I measure the length of the crimp on the case mouth. The crimp is very visible and easy to measure. Repeated measurements of my "Dillon" taper die shows a 10:1 length vs crimp. A crimp line .040" long gives me a crimp of .004". If I have a .472 case and a .040 visible crimp then I get a crimp of .468.
  I have only done this with Dillon dies. Hopefully someone will try this method with other brands and post some feedback.

Len

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Re: Measuring the taper crimp

Post by james r chapman on Mon Sep 07, 2015 11:02 pm

I just look at them at 50x on the optical comparator....

What a Face

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Re: Measuring the taper crimp

Post by Ed Hall on Tue Sep 08, 2015 12:51 am

I lock my caliper to a setting such as 0.470 and then see if the case mouth makes it between or not.  Then I adjust my caliper in or out and lock it again, or adjust my die in or out if that's what I'm looking for.

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Re: Measuring the taper crimp

Post by LenV on Tue Sep 08, 2015 1:44 am

I know there are a lot of ways to get the measurement. A go-no go gauge like Ed suggests or a 50x optical comparator (Walmart isle 7). But I was trying to come up with something anyone can do easy with the tools on every re-loading bench. It would be just as easy to say (with Dillon) to crimp the case till it shows a .040" mark as to say " crimp to .468" and one of those statements is a lot easier to measure and yields the same results. I know that is re-inventing the wheel but it might make it easier for some.

Len

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Re: Measuring the taper crimp

Post by Rob Kovach on Tue Sep 08, 2015 2:41 am

You can get a caliper with a locking screw at Harbor Freight Tools for $12 to do the operation that Ed Hall described.

....you might be able to find enough coupons on the internet to get it for less.

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Re: Measuring the taper crimp

Post by Jack H on Tue Sep 08, 2015 3:19 am

I find the often stated .470 crimp to be straight wall.  I.E. no taper. 

My crimps are at least .004 less than straight wall (diameter)

With a trained eye, holding the round side and a straight edge on caliper together against a light you can see the taper when it is there.  And I do not hesitate to crimp deep like .465 ala Giles.

Oh! And I have 3 calipers.  The cheep digital never agrees with the better Starrett or Mauser set even when each is set tp a 1" standard and zero checked.  Someday I should compare them all to my mike.  At this time I am satisfied with the visual against the light with an initial setting to be .004 (or more) under straight wall

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Re: Measuring the taper crimp

Post by Ed Hall on Tue Sep 08, 2015 10:12 am

In a similar action to Jack, I often place two cartridges side by side to evaluate the crimps.

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Re: Measuring the taper crimp

Post by BE Mike on Tue Sep 08, 2015 10:17 am

Jack H wrote:I find the often stated .470 crimp to be straight wall.  I.E. no taper. 

My crimps are at least .004 less than straight wall (diameter)

With a trained eye, holding the round side and a straight edge on caliper together against a light you can see the taper when it is there.  And I do not hesitate to crimp deep like .465 ala Giles.

Oh! And I have 3 calipers.  The cheep digital never agrees with the better Starrett or Mauser set even when each is set tp a 1" standard and zero checked.  Someday I should compare them all to my mike.  At this time I am satisfied with the visual against the light with an initial setting to be .004 (or more) under straight wall
I have taken custody of my father's bullseye equipment and I was fascinated to find a paper with instructions, for Star produced equipment, that indicated (as you state) that a crimp of .465" was recommended. My accurized pistols never performed well (tested with a Ransom Rest) with a crimp tighter than Ed Hall's .470", but I've never used Star reloading equipment.

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Re: Measuring the taper crimp

Post by Fire Escape on Tue Sep 08, 2015 9:19 pm

Looks like I will be testing my .469 crimp tomorrow. The latest batch of ACME cast bullets that I opened to load yesterday seem to mic right at .452, they don't feel all that 'secure' although I only had one round that I could pull back out with my fingers after crimping. I always thought that cast ought to be a few thousandths larger than bore diameter ...... Probably just 'seat of the pants' testing but we'll see how it goes. I may be turning that crimp die down a bunch more tomorrow night!

Bruce

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Re: Measuring the taper crimp

Post by LenV on Tue Sep 08, 2015 9:42 pm

Fire Escape

I posted this idea to see if it would help anyone figure how much crimp they are getting. When/if you turn that crimp die  down take a look at the case. When I have the right (about .004") crimp then I have .040" of taper showing on the case. It is really easy to see. Like Jack looks for, you should see a definite crimp when comparing to a straight case.
Len


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Re: Measuring the taper crimp

Post by Jerry Keefer on Tue Sep 08, 2015 11:00 pm


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Re: Measuring the taper crimp

Post by james r chapman on Tue Sep 08, 2015 11:03 pm

Walmart, aisle 7?

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Re: Measuring the taper crimp

Post by Wobbley on Tue Sep 08, 2015 11:13 pm

https://m.mscdirect.com/mobileweb/product_detail?id=89305940&hasRestrictedParts=false. Not quite Walmart but close.

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Re: Measuring the taper crimp

Post by LenV on Tue Sep 08, 2015 11:29 pm

james r chapman wrote:Walmart, aisle 7?


  I guess my point was that it was not a common item. That was my feeble attempt at humor.

Len

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Re: Measuring the taper crimp

Post by Ed Hall on Wed Sep 09, 2015 12:54 am

I should probably mention that my 0.470" crimp is pertaining to the Nosler and Zero 185gr JHP bullets.  I do not believe in over crimping these bullets.  But, then again, the best anyone got from my loads out of a barrel tester and my barrel, was 0.989" CTC at 50 yards...

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Re: Measuring the taper crimp

Post by john bickar on Wed Sep 09, 2015 1:18 am

Bullseye season must be winding down in the cold parts of the country. Y'all are welcome to come shoot with us in sunny California.

(Bring water - please!)

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Re: Measuring the taper crimp

Post by james r chapman on Wed Sep 09, 2015 6:58 am

OldMaster65 wrote:
james r chapman wrote:Walmart, aisle 7?


  I guess my point was that it was not a common item. That was my feeble attempt at humor.

Len
I  thought it humorous and was just carrying it on...

Jim

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Re: Measuring the taper crimp

Post by Wes Lorenz on Sat Sep 12, 2015 1:27 pm

This was easy to make & use.
Wes

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Re: Measuring the taper crimp

Post by jglenn21 on Sat Sep 12, 2015 11:41 pm

I knew someone would wipe out the boring bar.


very nicely done

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Re: Measuring the taper crimp

Post by kwixdraw on Sat Sep 12, 2015 11:51 pm

Now that is a worthy project.

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Re: Measuring the taper crimp

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