# How much crimp?



## Savage260 (Oct 21, 2007)

I just set up my dies for reloading .444 Marlin. I have never loaded any thing that has needed a crimp. My bullet seating die has a roll crimp, but I am not sure how to judge how much crimp I will need. Is there a real danger of over crimping and causing extreme pressures? Any advice would be great! Thanks!


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## People (Jan 17, 2005)

Crimping is easy. The way most do it is if you have any factory ammo with the same bullet adjust your die to crimp that much when you are doing load development.

You can try going lighter and give your self a full mag and start shooting them, eject the last round and measure the over all lenth. If it changes you would need more crimp. If you do add more crimp it is best to back off your load a little bit and do more testing. Usualy adding a little crimp does not make pressure spike but it can happen. Sometimes crimping makes bullets shoot better.

The less crimp you use the less wear and tear you will have on your brass.

Fear is not the only emotion Chuck Norris can smell. He can also detect hope, as in "I hope I don't get a roundhouse kick from Chuck Norris."


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## Savage260 (Oct 21, 2007)

> The way most do it is if you have any factory ammo with the same bullet adjust your die to crimp that much when you are doing load development.


Is this done by measuring some how? I looked at the factory loads from Hornady, and I couldn't tell any difference between those and my dummy rounds, and I adjusted the crimp a bunch of times.

Will it be much different if they use a taper crimp and mine is a roll crimp?


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## ac700wildcat (Oct 30, 2006)

The taper crimp is basically used to close the bell back up on an auto cartridge that headspaces on the case mouth. A case that has been taper crimped properly won't really show a crimp. The roll crimp should actually roll the case mouth into the crimp groove on the bullet. I made a couple dummy rounds to kinda show you what it should look like. The left one is what a good tight crimp should look like and the two on the right are where I crimped a bit too much and actually started cutting into the brass. I'm not sure exactly why the die cuts in to the brass, but it does it with both Hornady and RCBS dies. I haven't had any set back with full power 357 loads while crimping like I did on the brass on the left.


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## Woodser (Sep 3, 2009)

For straight wall cases I always put on a maximum crimp, especially if they are too be used in a lever gun, a hard kicking revolver, or any tubular magazine. Slow burning powders will also receive a benefit from a full crimp. You do this from the start when working up your load and there will be no concern about over pressure. The real concern would be not using enough crimp, and having a bullet seated deeper by recoil, which would cause high pressure. Possibly very high pressure, depending on load.


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## Savage260 (Oct 21, 2007)

Thanks for the pix!! My dummy round crimps don't look any thing like yours. Could it be because the cannelure on the flex tip bullets doesn't allow them to roll in as much? I am not sure if this is really the case, just looking for reasons. I will screw the die down some more and see how that goes. Thanks for all the replies!!!


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## ac700wildcat (Oct 30, 2006)

When I turn my dies down to the point that the crimp hits the case it takes less than half a turn to get a full crimp. What brand of dies are you using? I've only used the lead bullets so far, but I have some 158gr xtp's that I'll make a dummy round out of and see what it looks like. I think the cannelure on the xtp's should be the same as the flex tips that you have.


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## ac700wildcat (Oct 30, 2006)

I just made a dummy round with a jacketed bullet with a cannelure and they crimp the same. Are you seating the bullet so the case is almost to the top of the cannelure or at least in the middle?


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## People (Jan 17, 2005)

The crimp is ususaly just eyeballed and when it looks the same you are good to go.


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## Savage260 (Oct 21, 2007)

I have the cannelure in almost the exact same spot as the factory loads. I don't have an insert for my comparator yet, so i am not sure exactly how close they are, but close enough. I just can't see the nice roll like in your pix.


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## Woodser (Sep 3, 2009)

It is possible you have a taper crimp die and not a roll crimper? There will be no pronounced roll from a taper crimper.


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## Savage260 (Oct 21, 2007)

That is very possible. I was told it was a roll crimp, but there is no mention of that in the info that came with the dies. I have never used a crimp before, so I have no clue!!


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## ac700wildcat (Oct 30, 2006)

What brand of dies are they? I'm wondering if they might be taper crimp as well. Are they making any marks on the brass at all?


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## Woodser (Sep 3, 2009)

I am wondering if he does not have the Lee collet seating die, which has no crimp at all. You will need a separate crimper if that is the case. Like the Lee factory crimp die.


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## Savage260 (Oct 21, 2007)

I only use Hornady equipment, and it has some sort of crimp ring in the bullet seating die, just no mention of roll or taper. The info just states a "crimp ring". It is making marks on the rim of the case, just doesn't look like a roll. I am going to play with a few more dummy rounds and check it out tomorrow.


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## SaberX01 (Sep 25, 2009)

There are two types of crimps, Taper and Roll. I've never used an Autoloader and thus have not had a need for a taper crimp. However, I have rolled many heavy 44's / 40's & 357's for use in lever action rifles. I use the instructions booklet that accompanied the die's to set the crimp range / depth as well as all the other aspect of the load. The loads are always very consistant, only the shooter makes the fly off target 

Here's an article that describes how to set up a 3-Die set (Roll or Taper crimp) using RSBC dies, but it could be used as a guide line for most any die set I would think, as the principal is the same. --> Set the bullet seat depth, then estblish the crimp range, in this case 1/8 - 1/4 of a turn on the crimp ring. I dont have a way to measure presure, but my chrono tells me the seats and crimps are solid, as the velocity's rarely change +/-more than a few FPS.

As the author states, proper die set up is also clearly laid out in the instruction booklet that accompanies RCBS die sets. I can't speak to other die mfg's as Iv'e only ever used RCBS die's.

Link: How To Adjust Reloading Dies:
http://www.chuckhawks.com/adjust_reloading_dies.htm

EDIT: If your not sure which Die you have; Taper, Rolled or Straight (no crimp), i'd call the MFG of the Die set and have them help you identify "exactly" what you have. Not to understate the dangers of misloading, but having to tear down 100+ rounds due to an error in preparation can be mightly frustraighting. Sucessfull handloads start with proper preperation & setup.

Good Luck with your loads.


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## Savage260 (Oct 21, 2007)

I appreciate the posts, but the Hornady info says

"Thread the seater die body into the press in small increments (one-sixteenth turns) each time operating the handle. At the completion of each stroke, inspect the cartridge for the proper crimp."

So my question is, what is the "proper" crimp?

I think I am just going to have to try some and see if the bullets seat farther in after taking the shock of recoil a few times.


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## ac700wildcat (Oct 30, 2006)

Try crimping and seating in two steps. Put an empty case in the shellholder and run the ram all the way to the top. Then turn the die down until you feel the start of the crimper touch the case and back it off 1 turn and lock the die in place. Adjust the die to seat the bullet to the depth that you want it to be. Once you get that set, turn out the seater part all the way. Put the ram all the way up again with the case that has the seated bullet in it. Turn the die down until you feel it touch the case again. After that, lower the ram and give the die another 1/8th or 1/4 turn in and see if you get any crimp. I use Hornady dies for my 357 and this way works for me.


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## Savage260 (Oct 21, 2007)

ac700, that is basically what I did, but was just wondering with a .444 Marlin vs. a .357 if the 1/8-1/4 turn adds enough crimp. I suppose there really is no way to tell until you try it.


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## ac700wildcat (Oct 30, 2006)

Gotcha. I suppose shooting some like you said would be the best way to tell.


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## SaberX01 (Sep 25, 2009)

Here's another good article with some visual examples of roll crimps (light, Good, Too Heavy), but it doesn't detail a way to physically measure the roll.

Link: http://www.exteriorballistics.com/reloadbasics/crimp.cfm

This was bugging me today so i thought about it a bit. You could do a couple things to "measure" an affective roll crimp. Innovative Technologies make a nice Head Space gauge for about 80 bucks or so, an you could measure virtually every external aspect on a set of factory loads to get get what I've heard it referred to as an acceptable tolerance / depth of roll for that given brass / bullet / load combination. The unit is capable of measuring to .001", so that should get you in the ball park.

Another Idea would be to measure the OAL of your reloads, before loading the rounds in the mag, load a full mag then fire the first round only, remove the remaining rounds and remeasure the OAL again, then fire the next, unload and measure, etc etc to see if your OAL is moving at all. By the time you get through 4 or 5 sequential shots you will know if the bullets are moving from recoil. If your OAL is not moving then you know your deep enough, if it is moving, clearly it needs more, but how much is probably going to be load combination specific.

I also discussed this with a friend who shoots 1000yd IBS and he recommended to chrono all the loads for consistency. Often times flyer's or inconsistent patterns can be traced back to excessive head spacing or your crimp is not holding the bullet firm, assuming your powder charges are fairly accurate and you get good ignition each time from the primer. He also said to use a run-out ( could use the Head Space Gauge here also ) gauge to profile the load from one end to the other along 4 axis line, including measuring the roll depth, as this way you have established a good reference point to work from. From there, once your velocity + grouping is stable, and you have little to no OAL movement, you'll know your roll depth it adequate. Then all you have to do is measure the roll and you've got your number. Bare in mind, this roll depth will change with any change in components, and could easily change with inconsistent brass as well.

Let us know what your final process turns out to be as I'd be interested in testing it out on my 44 Mag lever gun loads.


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## Woodser (Sep 3, 2009)

How much crimp is a good crimp depends on a lot of things, like what powder you are using, how much recoil you expect, the type of rifle used, the round you are shooting, ect. For example, a single shot rifle might need a little crimp for complete combustion in a straight walled case, but requires none for recoil. A lever action in a heavy recoiling round will require a heavy crimp to keep the bullets from moving in the magazined rounds. Loads using very slow burning powders in straight walled cases usually need a medium crimp to ensure complete combustion of the powder. Experimentation is the way to find out what degree of crimp is best. When in doubt, use a full, heavy crimp and start from there.


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## Savage260 (Oct 21, 2007)

For this hunting season my final process is going to be......use Hornady factory loads!!! They shoot great at 100yds, so I am going to give them a shot a 200. This winter I will have some more free time to work on loads, and I enjoy shooting in the cold much more than when it is 60+. I was planning on starting with just the 1/4 turn to start, and measure OAL after a few shots and going from there. I will post and let you know how it goes. Thanks for the replies every one!


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