45ACP Crimp.

I was previously crimping at .469 for everything (25Y and 50Y).  But some literature
suggests tighter for lead and swagged lead.

Taper crimps:

Cast and swagged lead = 0.463

FMJ and JHP = 0.469 

Anyone care to chime in with experience?

I'm  at .463 and it doesn't blow up. Seems to improve the burn.

Dardas hard cast.

. 468 crimp.  Shot at 25 yards from a rest while chronographing. 

Can you explain how to measure the crimp.

unfortunately, I think most shooters have a difficult time accurately measuring crimp.
most use calipers, using the thin edge (still probably .020 thick)just allow the crimped brass to seize in the gap.

I have several machined holes of known diameter. If one enters one and not the other, I know what the crimp is.

others, Like the late J. Keefer, might use an optical comparitor!

Good topic! The more I know, the more I really don’t know.

Sorry, my entire post didn’t show up completely. From past discussions, my understanding was that the lesser the crimp, less damage to the lead bullet resulted. Thus, more accurate rounds were made. Obviously, many have had good success with tighter crimps. An advantage which I can appreciate would be the cleaner burn. With 3.8 gr BE powder and my .469 crimp, I experienced a lot of crud buildup and quickly although the rounds were very accurate. The only meaningful test groupings would be done at 50 yards and not at 25 yards. Are there any shooters who have tested their rounds with the looser and tighter crimps for accuracy and be willing to share their results? Thanks in advance.

I think it depends on what crimper one uses. It seems like the Star crimp works well with a tight crimp, while others, like Dillon, work better with a .470 ish crimp. I think that, back in the day, Giles recommended the tight crimp. It's tough to argue with that kind of expertise. That being said, the machine rest at 50 yards is the real test.

Dang!   That adds one more dimension to the Ransom Rest testing I will be doing this summer.

Don

Thank you!!!

Thank you Don! A friend who uses a Star reloader also uses a tight crimp, although not sure of the exact measurement. He is a fan of Bob Chow and owns several of Bob’s 1911’s. Looking at some of the old Gil Hebard catalogs of the 70’s, Star seem to be the only progressive reloader available at that time period. BE Mike may be on to something. Reputable old timers probably did extensive testing and found tighter crimps such as .463 to be the best (with the star). This is just conjecture on my part until we hear from some of these knowledgeable old timers or those who were close to them. I have Dillon equipment.

Accuracy is not the only reason to try different crimps.  On my Salyer built 1911 it functions better with a .464-.465 crimp than a 4.69 crimp (using 185 grain lead swc bullets) While accuracy is important an un reliable round will probably cost you more points than a slightly less accurate but reliable round.  Just my two cents worth which with 5 bucks will get you a happy meal.

Talk about a tight crimp.   Look at what Roddy Toyota put on the ammo he used to target my wad gun.   Yikes!

Don

I use .463 (as close as I can measure) I was under the weather yesterday and was not able to shoot our local match. So when the sun snuck out today so did I. 10 shot group (25yd) with hand on a rest. Some vertical stringing with one flyer but overall almost acceptable.  It was the first time trying out the Aimpoint on the RO. RO is mostly stock.

Seems like the gun shoots ok Len.

I thought I should mention that I don't really measure my crimp anymore. It is too hard to measure without go-nogo gauges. Instead I measure the length of my crimp. I use a Dillon taper crimp die. I figured out years ago that I need a crimp .050" long to give me my desired .463 crimp (lead bullets).

eezzy-peezy Len...

Multiple schools on this and there many different results.  

In the 1960s NRA Handloader Guide, there were two articles of interest.  Alton Dinan claimed that accuracy improved with a heavy roll crimp to .460.  He was using an alloy of 18-1-1 which would Brinnell at around 13 or so and would be similar to “magnum alloy “.  In that same publication, the article Pistol Champions’ Target Loads, we find the following: 
Gertrude Backstrom Taper    ;  F Bob Chow   None ;  GP Defino   Light;  William Guiette  None;  Gil Hebard  Taper to .460;  John Hurst None;  Ellis Lea   None;  Harry Reeves  Light;  WT Toney  Taper.
So there’s hardly a consensus here.

Al Miller in Handloader wrote an entire article on this very subject inHandloader 54 in the mid 1970s.  His accurized pistol preferred a very light taper and his GI 1911A1 would not tolerate ANY roll crimp at all.  

The upshot of all this?  You have to test what your pistol likes.  Start with a taper crimp.   Since the case mouth diameter is close to .471 with jacketed loads, you have .011 to play with.  I wouldn’t crimp below .460.  

For the experimenters, I’d first select one of the many known loads with good bullets and then;  
- vary the charge weight in 2 tenths increments, when the best charge weight is discovered,
- vary the crimp from .471 to .461 in 2 thou increments. 

Then go shoot holes in the x.

Too bad we don't know what cases they were using back then.
I'm assuming the "no crimp" was probably WRA brass...

james r chapman wrote:Too bad we don't know what cases they were using back then.
I'm assuming the "no crimp" was probably WRA brass...

In the Pistol Champions’ article there was no mention of cases used.  Gertrude Backstrom stated she used primers “depending on make of case” which would indicate that she sorted her brass by maker.  Other than that no indication.  I would imagine that the vast majority used military brass on the short line and commercial cases of one make at 50, though I have no information to back me up on that.

I've never given a whole lot of attention to the crimp. I set it on the press and thought what I had was good enough and moved on. I use a Lee die set for 45 ACP and 38 Special which includes a "Factory Crimp" die. I do no know if it's a roll crimp or a taper crimp. If someone here knows please let me know. I'm curious.

The “Factory Crimp Die” is more roll than taper.  But it is accomplished differently in that there is a collet that squeezes the mouth of the case in radially rather than wedging the mouth in from a bevel.