.463 crimp

I hear of so many people recommending crimping to .463" and it really baffles me.  At that amount of crimp the lead bullet IS being deformed and not just a little.  I'd like to know why this is helpful and how accuracy can possibly be achieved with an undersized projectile.  Technically leading should also be pretty sever since gasses should blow by and cut the lead.  

When I crimp to .468" I can measure a slight reduction in the diameter of a pulled bullet at the top driving band.  The bottom is still .452" though.  If I go lower than that, I see the bottom of the bullet getting skinny too.  .463" should swage the bullet down to .447" or so.  Not beneficial in my experience.

Hello Lightfoot,

I won't speak for others but I have not had much luck with that tight of a crimp.  I believe that the argument is that it improves the combustion of light loads.

Jim

The crimp was popular in the 1960s.  An American Rifleman article by Alton Dinan used that crimp to develop target loads for the 45 Auto.  I believe Giles and Shockey also advocated a .463 crimp.  

It might be worth a try, but I’ve been getting good results with a .468 crimp.  Like you I don’t want to work the bullet any more than necessary.

I used 0.468 until I started shooting softer loads. Found I needed 0.465 to get them to run.
Land Variance I see for barrels is 0.442 to 0.443, so driving band still getting good contact in the rifling. Bases are 0.452 and sealing up the gases.
In my experience consistent crimp is more important than OAL or powder charge used.
Last year I loaded some 38 148 hbwc and did not roll crimp the cartridges enough. 50 yd groups were horrible. Added more crimp and they shot on call. 45 more forgiving but not enough crimp will open up the groups some.
I have not tried 0.463, I’ve always thought that to be extreme.
Jon

IMHO .463 only necessary for the 160's that come from the Magma Mold for both function and accuracy with light loads.  My 200 & 185 crimp is .467.

Also the crimp is only deforming the very top of the case & bullet so 95% of the bullet remains intact. I've been using .463" with good results but not done tons of testing. Would be interesting to see in depth testing showing the crimp results with different bullet profiles, powders and barrels. Anyone got a bunch of free time on their hands?

zanemoseley wrote:Also the crimp is only deforming the very top of the case & bullet so 95% of the bullet remains intact. I've been using .463" with good results but not done tons of testing. Would be interesting to see in depth testing showing the crimp results with different bullet profiles, powders and barrels. Anyone got a bunch of free time on their hands?

What dies only crimp the top?  With my Hornady die and that much crimp, even the base is reduced to under .450"

I use the Dillon taper crimp die. I can check but pretty sure it just tapers the top of the case.

I am thinking my crimp at .472 is not enough and could be why I am getting unburnt powder on my lighter loads.

I've been advocating a .463 crimp. I get a lot cleaner more consistent burn with Bullseye powder. The die I found that works the best is the Dillon taper crimp die. I don't crimp the whole case. Just the last 1/16". You can visibly see if you have a good crimp. That crimp is much smaller then the lube groove/s.

With that much crimp are you guys seeing any brass shavings on your press or output trays?

Ray Dash wrote:With that much crimp are you guys seeing any brass shavings on your press or output trays?

Depends on the die.  The crimp area in some dies does not extend smoothly in enough area to give a clean tight crimp.  Lee FC comes to mind.  Lee shreds brass.  I have no use for the Lee.  Dillon TC does good.  But my favorite is an old RCBS TC seater used crimp only.  Very smoothe crimp.

Here are what my cases look with a .468 crimp. I am using the Dillon taper crimp and getting a lot of brass shaving.

That particular die is not made to crimp that tight.  You get shreds as you go beyond the machined area.  First thing to do is find out how far any single die will go.

Do you think polishing the die with a good metal polish would help?

Ray Dash wrote:
Here are what my cases look with a .468 crimp. I am using the Dillon taper crimp and getting a lot of brass shaving.

Are you sure that's .468" crimp? That is worked down on the case a long way. I run .463" and mine look like Len's, it only works the top 1/16" or so of the case. I do get some brass shaving that build up in the crimp die, I clean it out every couple thousand rounds.

I think what you are seeing is the bell where the bullet is seated to. The actual crimp area is the shiny part at the very top of the case which is about 1/16th inch.

Ray Dash wrote:I think what you are seeing is the bell where the bullet is seated to. The actual crimp area is the shiny part at the very top of the case which is about 1/16th inch.

Right but your picture sure makes it look like there's something rubbing the case a good ways down. A bullet bulge doesn't look like that on my finished rounds.

Here is a better pic. Going to polish the internals on the taper crimp and if that doesn't work order a new die. I have loaded 9mm for years and never had a taper crimp shave brass. 

One thing is with 45 the majority of people use lead which you typically bell the case more to avoid lead shaving, especially if you use flat base bullets. On 9mm a lot of people are using JHP which doesn't need near the bell. I think maybe the brass shaving during the taper crimp is dictated by how much bell is having to be removed.

I'd like to ask the .463 users to pull a bullet and measure the diameter at the crimp and the base.  I'd  like to see it even though I'm not from Missouri.  LOL.

zanemoseley wrote:One thing is with 45 the majority of people use lead which you typically bell the case more to avoid lead shaving, especially if you use flat base bullets. On 9mm a lot of people are using JHP which doesn't need near the bell. I think maybe the brass shaving during the taper crimp is dictated by how much bell is having to be removed.

I believe you may be right. I took a case with much less bell and ran it through the crimp die and there are no brass shaving at all. I guess I will have to live with a little shaving because I need to keep the bell for my bulletfeeder and to keep the case from cutting the lead bullet. 

I did take the dremel out and polished the crimp die insert for a couple minutes and it made a pretty good difference. You can see from the pic that the bullet on the top has a polished ring around the top 1/16" and the one on the bottom after I polished the die doesn't. The bottom one fed much smoother too but I still got some brass shaving. 

I learned about .463 here. I get better accuracy by my tests.

It works for me.

David

Negligible. .452-.453

This was discussed a long time ago. Mr. Toyota is a big believer in the .463" crimp. I did some tests and through my pistols, the .463" crimped ammo produced much bigger groups from the machine rest at 50 yards. That being said, that was with my guns. I use a Dillon taper crimp die. A long time ago, the test for crimp was to just make sure that the bullet stayed in place under recoil. There were other articles that promoted a roll crimp for .45 ACP loads. I don't know for certain, but I think that it is likely that Mr. Dinan, Giles, Shockey, et al. used Star machines with Star taper crimp dies. One thing I don't see on here much anymore is accuracy testing at 50 yards. That's where the rubber meets the road!