Crimp tight, loose?

Ive reloaded many thousands of 45 acp target loads, many with the star 185 swc-hp, and was testing the other day and found out something interesting. I usually crip my rounds to .469 , they shoot and feed good so i stuck with it. Back years ago when i ransomed many loads i would keep the targets and list the load info. The other night i was looking thru them for a good load using Bullseye powder since i have been loading with just Vit-310 and wanted to change things up a little. I ran across one that had a great target, 1.5'' @ 50 yds, the basic difference in my load that day and now was the crimp was .472. So i loaded 9 rounds with .472 and 5 with .469, just to play with, i was very surprised at what resulted. Both targets shot off hand at a indoor range that was only 50 feet deep, target on left 5 in the 10 ring, i thought ok not bad, then shot target on right with same load except with the .472 crimp. Shot 5, all in one hole, reloaded and shot the other 4. 2 more in x and 2 right together which was do to my grip, loosening a little i suppose. I know this was not a perfect test but it did open my eyes as to how the crimp can make a difference.

maybe the looser crimp causes less distortion to the body of bullet which would mean better accuracy....when I shot varmints at 3-600 yds none of my loads were crimped at all ...I would simple size the case neck only and seat the bullet into the sized neck........all of my rifles with their pet loads would do 3/4'' or less @ 100yds.....one of my .223's would shoot into 3/8'' 5 shot groups normally and shot less than a 1'' @ 200 with no crimp....

Too add to my post, the lighter crimp while more accurate sometimes leads to failure to feed in a 1911, so i only use the lighter crimp on 50 yard loads and .470 on timed and rapid loads.

Crimp is one variable to test when trying to get the most accurate load. I've heard some knowledgeable people say that they use a very heavy crimp and get great accuracy. IIRC, most were using a Star loader and dies. I did some tests years ago with Nosler bullets and Star bullets loaded for .45 ACP. I don't remember the brand of taper crimp die I was using, but it wasn't Star. I shot the ammo on a Ransom Rest. I used a very heavy crimp and moderate crimp (.470"). The heavier the crimp was, the worse the groups got at 50 yards. A heavy crimp might work for some, but it doesn't work for me.

heavy crimps only work on hard bullets and then .467 is as low as you should go.

"heavy crimps only work on hard bullets and then .467 is as low as you should go." David R

Why??????????? John

From In My Experience - Dec 1992 American Rifleman
More On Taper Crimp

Editor: In my gunsmithing days (‘51-’83) I
specialized in target pistols, primarily .45s. Early on I would get
customer complaints where the gun failed to go completely into
battery, i.e. the slide did not go all the way forward. Nearly always
the cause was a reload with a short case.

The case had been flared to receive the bullet and the standard roll
crimp did not quite remove the flare. Or alternatively, the customer
believed the case should not be crimped at all and the roll crimp
failed to straighten the flare, which would hang up in the taper of
the .45 chamber. The answer, of course, was to sort the cases
carefully, eliminating the short ones. As usual, not everyone wanted
to bother.


Another disadvantage of the roll crimp was that the degree of crimp varied
directly with the length of the case. Long case, hard crimp – short
case, no crimp. This caused not only malfunction but inaccuracy as
well. Since I test fired every gun at least 100 rounds and guaranteed
a specific level of accuracy. I looked for a way to avoid trimming
all cases to a standard length. But I could not afford to discard the
short ones.


My previous toolmaking and inventing experience led me to the tapered crimp. It
requires a separate operation, of course, but has several advantages
over the roll crimp.

• One was that a slight difference in case length made little difference in
  the degree of crimp.
  

• Another was that cases lasted a lot longer before splitting. The taper crimp
  did not “work” case mouth brass as severely as the roll crimp.
  Crimp-caused malfunctions were eliminated.
  

• The taper crimp also prevented telescoping, where the bullet slides back
  in the case when it hits the loading ramp.
  

• Finally I seldom had to discard a case because it was short. So what kind
  of accuracy are we talking about for these taper crimped reloads?
  
  

First a bit more history. It soon became apparent that my time would be better
spent if I bought reloads even though I had two Star reloaders.
Fortunately, I knew a few really capable reloaders. Gene Wilson and
Joe Maszk come to mind. Frank Shuster was a top bullet caster also.
Joe Mazak loaded sample quantities of those good bullets with powder
charges from 3.3 to 4.4 grs. of Bullseye, taper crimped to about
.463” at the case mouth gave the best accuracy. Cases were all one
kind and loaded on Joe’s Star machine. Seldom did I see factory
ammo that would shoot as well, and when I did, the military guys had
it.


And the numbers? Well, I made more than 4,000 target .45s over the years and
must certainly have fired at least half a million taper crimped .45
reloads. I guaranteed each .45 capable of shooting five shots into
1-3/4 in at 50 yds. and fired an average 1-1/4 in test group. My
personal best from a Colt .45 was 5 shots in .39 in. at 50 yds. And
I had a fair number of groups at ½ in. Under 1 in. was not uncommon
at all. I didn’t always send the best test group with the pistol
but I did always include loading data. I designed a taper crimper
for the Star machine so there was no extra operation. Ernest Whalen
of Heatbath Corp. made and marketed the taper crimper for a number of
years, paying a small royalty for use of my design.


My customers had most of the above info. Guess I should have made it
available to all handgunners. But I tend to put things off, like
trimming cases, for instance.


John E. Giles
- Odessa, Fla




Well ya never know til you tried it.....
I have crimped below 465 with no problems.

Jack H wrote:[size=9]




Well ya never know til you tried it.....
I have crimped below 465 with no problems.

I would be interested to know if you were using a Star taper crimp die and what type of bullet, i.e. cast or swaged. I think this goes to show that there are no absolutes in this game. What works for one may not work for another. Although, there are good guidelines and starting places from which one may begin without re-inventing the wheel.

Within the Giles article:

Frank Shuster was a top bullet caster also.
Joe Mazak loaded sample quantities of those good bullets with powder
charges from 3.3 to 4.4 grs. of Bullseye, taper crimped to about
.463” at the case mouth gave the best accuracy.

Cast bullet, .463

John wrote:"heavy crimps only work on hard bullets and then .467 is as low as you should go." David R

Why??????????? John

Crimp is only suppose to straighten out the bell of the case and taper to allow a good entrance of the bullet into the barrel and give enough pull out force to allow a good powder burn. Any more than that really doesn't increase accuracy, and if so tight it deforms the bullet will decrease accuracy. Also the amount of precieved crimp, is also based on the thickness of the case. A thin case with the same amount of crimp as a thick case will read different, .465 can be the same as .467 just from the different brass. My tests were done with mostly starline cases some other brands are thicker, some like Remington are thinner. Back when Giles loaded from my research, he was loading bullets he had cast and they were very hard. If you try and crimp a soft lead bullet more than .469 you start to deform the bullet, you might crimp a hard cast lead bullet to .467 or even .465 with no deformity. If your crimp doesnt deform the case or bullet and allows good feeding, then dont worry about numbers.

I've been down this road.
My first Kart barrel liked a very hard crimp (.463-.465) that I found through extensive Ransom testing. I was using a hard cast H&G 68 bullet and 4.4 gr WST. I tried every crimp level from .463 to .471 in my tests along with several fast powders (Bullseye, Solo 1000, WST, Clays and a couple others I can't remember). That barrel really liked a hard crimp.

My second Kart is more in line with the norm. It likes .469 with a softer bullet than what I originally used (I quit water quenching my bullets) and the same powder charge. Short line I stick with 3.5 gr Clays with the H&G 130 and a harder crimp (only because I'm paranoid about feeding failures in sustained fire) of .467.

I had some dialog with Dave Sayler some time ago, he also likes a hard crimp, but he sets his creations up to digest and deliver excellent accuracy with those parameters.

FWIW