Best taper Crimp

I see that there is basically two groups when it comes to taper crimp. One group ( including me) favor a crimp of .469 or .470. Then others use a tc of .463. So what is best? Does it depend on powder? Is there a difference between lead and jacketed bullets?

.467-.468 seam to work best for me it is hard to measure for sure I use  0 to 1 mike  and try to get on the very end it seams to over the years that the lighter the bullet the smaller the crimp ned to be.

For my 45ACP loads I use 0.469" - 0.470" for jacketed bullets, and 0.463" - 0.465" for coated / lead.

AP

I like the old school thinking for auto loads of just enough crimp to keep the bullet from moving in the case. Others, including, old schoolers like John Giles, advocated a .463" crimp. I tried it and it doesn't work well for me with Dillon dies. Maybe Star dies are the secret to the .463" crimp. The final test is to try the different crimps and see what works the best with your loads and equipment.

If I had to absolutely stick with only one crimp diameter, and thank God I don't, it would be .469.

I've done a lot of testing on the Ransom with crimp variations. Brass wall thickness, bullet hardness, cast-swaged-or jacketed. All come into bear when chasing this.

Most of my brass now is .009 wall thickness. For some reason beyond my ability to fathom, my Caspian likes Remington brass and my Springfield likes TZZ. Both built by the same BE smith with the same reamer and Kart barrels. The Caspian likes Zero swaged 200's with Remington brass crimped to .463 for short line and Zero 185 JHP for the long line. The Springfield likes my H&G 130 FB with TZZ crimped to .465 for short line & Zero 185JHP for the long line.

Now back to reality. In my hand it doesn't make any difference any longer, I just wanted to know . Have lost a lot of fine motor skills with surgeries & just paying for the abuse I heaped on when younger.

Who measures crimp?
All taper crimp is for is to remove the case mouth flare. Look at factory rounds and you'll see that the case mouth barely touches the bullet, if it touches it at all.
I assume you have done exhaustive testing of different crimp diameters for group size? You have also taken into account the variation in case wall thickness?
Would love to see your data from your testing.

noylj wrote:Who measures crimp?
All taper crimp is for is to remove the case mouth flare. Look at factory rounds and you'll see that the case mouth barely touches the bullet, if it touches it at all.
I assume you have done exhaustive testing of different crimp diameters for group size? You have also taken into account the variation in case wall thickness?
Would love to see your data from your testing.

Most factory ammo is jacketed so your statement doesn't always hold true for our low FPS lead loads. Crimp can also be used to control combustion of the powder and can change your pressures. I've seen good groups shot with both .463" and .469" but never seen conclusive evidence of one versus the other.

Greetings,

From the Guy (John Giles) that invented the Taper Crimp Die...

Cheers,

David

https://starreloaders.com/forum/index.php?action=dlattach;topic=2602.0;attach=3383

My warmer loads have shot 0.469 lswc with good results; sub 2” @50 yds.
My 3.4gr 180 short line loads will not consistently cycle with 0.469 crimp with slide mounted H1 optic. Crimping down to 0.465 same pistol will cycle slide mounted 9000 optic.
So I now use 0.465 for all my lead loads; 2.7 up to 4.0+.
Jon

zanemoseley wrote:

noylj wrote:Who measures crimp?
All taper crimp is for is to remove the case mouth flare. Look at factory rounds and you'll see that the case mouth barely touches the bullet, if it touches it at all.
I assume you have done exhaustive testing of different crimp diameters for group size? You have also taken into account the variation in case wall thickness?
Would love to see your data from your testing.

Most factory ammo is jacketed so your statement doesn't always hold true for our low FPS lead loads. Crimp can also be used to control combustion of the powder and can change your pressures. I've seen good groups shot with both .463" and .469" but never seen conclusive evidence of one versus the other.

I have seen factory crimped to .465, well into the jacket. 
Shot just fine.  I think it was Winchester Hardball.

I also have pulled some Winchester hardball in .40 and .45, and the crimp was excessive. Each had a very deep ring in the jacketed bullet. I can only assume this would be done to keep rounds that possibly would be chambered numerous times from being setback.

fc60 wrote:Greetings,

From the Guy (John Giles) that invented the Taper Crimp Die...

Cheers,

David

https://starreloaders.com/forum/index.php?action=dlattach;topic=2602.0;attach=3383

Pretty darn sure I've read this "article" before (in fact, probably posted by you), but thanks for posting (again). 

Dave

To satisfy my curiosity & not rely on memory. I measured 15 rds of factory match. 5 rds of each, pulled at random from each box of factory match ammo.
5 rds IMI 185 JSWC
5 rds TZZ 89 230 match ball
5 rds WCC 90 230 match ball
All measured to .001

IMI match 185 JSWC= .466, .466, .466, .466, .467
TZZ 89 230 match hardball- .467, .467, .467, .468, .469
WCC 90 230 match hardball-.468, .468, .468, .468, .469


Got to remember, the crimp is only a part of the whole. It's a balance of gun, bullet, case, powder, crimp and the biggest one... the shooter. 50 year old me, with a 6" 45, would kick the snot out of 65 year old me with a 1" 45.
Al

Very interesting article Dave, thanks for sharing.

>Most factory ammo is jacketed so your statement doesn't always hold true for our low FPS lead loads. Crimp can also be used to control combustion of the powder and can change your pressures. I've seen good groups shot with both .463" and .469" but never seen conclusive evidence of one versus the other.


Show test results, particularly double blind tests. So far, what I see is hand-waving and no proof.
I tried various levels of crimp back in the mid-70s and found ZERO effect, until I had enough crimp to reduce accuracy by quite a bit.
I wish I had my data from back then, but too many moves and too many boxes lost over the years.
All I ask is for data.

noylj wrote:>Most factory ammo is jacketed so your statement doesn't always hold true for our low FPS lead loads. Crimp can also be used to control combustion of the powder and can change your pressures. I've seen good groups shot with both .463" and .469" but never seen conclusive evidence of one versus the other.


Show test results, particularly double blind tests. So far, what I see is hand-waving and no proof.
I tried various levels of crimp back in the mid-70s and found ZERO effect, until I had enough crimp to reduce accuracy by quite a bit.
I wish I had my data from back then, but too many moves and too many boxes lost over the years.
All I ask is for data.

Dave Wilson just posted this. It's about as conclusive of a test as you will see without doing brand new testing.

https://starreloaders.com/forum/index.php?action=dlattach;topic=2602.0;attach=3383

OK, here's my experience and observation.

Hard cast lead and jacketed seem to do better with .468 - 0.470.

Older casts loads (softer bullets) and swaged sometimes do better or needed tighter with .463 - .468. 

Everybody will get some variation based on chamber specs, throating, barrel manufacturer, etc. etc.

Give it a try.  with lead loads you can get leading and bad groups with too little or too much crimp.  

Sorry, but there seems to be no completely definite answer since I have shot and have seen great groups with the full spectrum of crimps. What I have found is that when you find the crimp for your gun and load - write it down somewhere so you can find it again.

CR

The reason I ask was I can not or have not got my lighter bullets to group well. My 200 g. LSWC are OK with .469. I am casting a nominal 160 g. version of the H&G 242S. My groups are 3 1/2" plus. Load is 4.5 g. of Bullseye. I am going to tighten the crimp to .465 and try again.
 I am thinking tighter crimp may give better ignition. All loads are with WLP primers.

For my pistol I use a .464-.465 taper crimp for a 185 grain bayou lead SWC on top of 3.7- 3.8 grains of Bulleye.  I started out with a .468 but the pistol works a lot better with the tighter crimp. At 25 yards it is an X ring gun with that load.  Of course with the jerk pulling the trigger the groups are usually a lot bigger. 

good luck with yours.

I last posted on this subject 10-31-2020. I loaded the 160g. bullet (168 actual) with 4.5 g. of Bullseye. The results were much better. 9 shots at 1 3/4" and a flyer out to 2 3/4". This was with a .465 TC.
 So the tighter crimp seemed to make a large difference in my limited testing. My previous best was 3 3/4 with the same load and a .469 TC. I use a Star TC die.
 My 200 g H&G 69 are good at .469 but not the 160.

My .02,
I was lucky to have had Roddy Toyota tell me to try a .463" crimp years ago and it has worked for me with LSWC's.  
As an experiment recently, I made a 20 degree taper crimp ring (stock is 10 degrees) for my FCD; with the thinking it would deform less of the bullets bearing surface.
It worked well in testing with a 2-1/4" 20-shot group at 50yds in the RR. Also had some nice targets in T&R at a local match last month. 

For the record, my 30yr old Lee FCD that does not swage my bullets down in size - https://www.bullseyeforum.net/t16025-lead-swc-bullets-case-belling-and-seating-question