How to measure a roll crimp?

[Shrinkmd]

I did fine with setting up a taper crimp for my 45ACP, bringing the case mouth to exactly what it should be (and no more).

How about roll crimp? People say use a "light" or "heavy" crimp. Are there accepted measurements for how much you crimp? And where exactly would you measure it to be consistent and logical about it? I don't want to overcrimp my 38's and 357's.

Thanks

 

[The Bushmaster]

By "eye ball"....It either looks good or it don't...

And I'm serious...

 

[loadedround]

Most reloading manuals will have pictures of roll crimps in them, or the instructions that came with your dies will give you a detailed explanation of the crimping procedure.

 

[jim147]

I have a box of odds and ends factory rounds sitting in my reloading building so I can do a good eyeball compare.

jim

 

[41 Mag]

As a general rule, I use just enough to see that the leading edge of the case is rolled into the base edge on the grove of the bullet. Depending on the powder and desired use of the loaded round, I will check some at the range to see if there is any slippage when using new bullets or a heavier powder charge.

If I see a change in OAL from the first round shot to the last in the cylinder, I will adjust ever so slightly, and recheck. Generally I have found that nothing will move until after the third round, and most times the fourth or fifth round.

I have played with differing crimps over the years and found that they DO make a big difference with some loads. What I have seen the most of however is folks over crimping loads due to reading "heavy crimps", and not realizing that a heavy crimp can be done with out squashing the end of the case and the side of the bullet.

Cast bullet require a bit more roll due to the lead being soft enough to allow it to smear under recoil. However this is also an area to try your loads out before loading a couple hundred and calling it good. It might make a big difference in both leading due to the case lip cutting the driving band, or accuracy due to to much pressure building up behind the bullet.

Don't make more out of it than it is however, after working through some for your self you will quickly determine what is good for your loads and simply go from there.

Good luck and have fun in the process.

 

[Walkalong]

I'm with The Bushmaster on this one. Eye ball it. With lead bullets with a crimp groove, just fill the groove.

 

[fjlee]

I have a dial indicator mounted on my press, so that it measures ram travel.

This enables me to quantify what my "eyeball" sees when I roll crimp my .357 Mag cartridges. I load only jacketed bullets, and prefer WW un-plated brass.

This is an RCBS press, and I use an RCBS die.

I roll crimp as a separate operation.

Thru lots of experimentation, I have found that .017 inch of ram travel gives me the roll crimp that I want. Much less than that, and there is the risk of "bullet creep" on the more brisk loads. Much more than .017 inch, and the crimp die will start to shave off a little whisker of brass from the OD of the case mouth.

Based upon what I've experienced, using this 1 individual die.......I feel that another individual crimp die might have enough of a dimensional difference, that I would need to tweek this .017 inch crimp a bit.

I'm sure that different brass, other bullets, used with other roll crimp dies.......would require a different amount of ram travel to achieve an optimum crimp. But......the dial indicator would enable me to quickly "close-in" on the correct amount of ram travel, now that I have a bit of experience with it.

An added benefit of having the dial indicator is that it's not necessary to always length-trim 100% uniformly. If case length varies a bit, no matter.....I just watch the dial, and move the ram .017" after case-mouth and die make initial contact. It's very controllable.

Lee in Denver CO

 

[Shrinkmd]

Here is another question: If your roll crimp isn't adequate, do the bullets creep out or slide deeper in? What is the main danger here?

I made up a batch of 158 gr LSWC with both 3.0 gr and then some 3.5 gr Bullseye charges. I increased the amount of crimp on the higher charged ones, and it is more obvious to the naked eye.

Should I go back and recrimp all the lighter loads a bit to make sure they are safe? I had one or two get the slight ring of brass peeled off, but the rest were fine. I will also compare to some factory ammo.

 

[Floppy_D]

I've shot a good bit of 357, 44 and heavy 45LC in the last few years, and I've always eyeballed my roll crimps. I tend to crimp on the lighter side, in effort to preserve brass. I've yet to see a bullet move in the case due to recoil from it's five adjacent brethren. I'm pretty convinced that the crimp is more for consistent ignition than for bullet offset, because I can't manage to get a bullet to budge from recoil. Picture the amount of movement it would take to move that bullet in the case, and then picture your hand feeling that same recoil. Snubnose 454 Cassull? Maybe. Most revolver loads? No. Get a decent looking crimp and be done with it.

 

[lordgroom]

fjlee- how did you attach a dial caliper to your press? Can I see pictures?

 

[Howard B]

While I don't disagree with the other's comments, especially the calibrated eyeball technique, I also use the fingernail method. If you drag your fingernail along the bullet and onto the case and the nail doesn't snag on the case rim, then crimp is at least adequate. I typically do not shoot heavy loads in my revolvers that require substantial crimp and have had pretty good luck with the nail method. Also, it important to adjust bullet depth to ensure the case mouth is in the crimp groove.

 

[ranger335v]

roll crimp? People say use a "light" or "heavy" crimp. Are there accepted measurements for how much you crimp?"

It's a visual thing, you will develop a "feel" for it. No one I've ever known tried to measure roll crimps.

Crimp heavy bullets in the .357, forget crimps in the .38 --- except enough to remove the mouth flair.

 

[jfh]

well, actually, I have tried to devlop objective criteria--

after a fashion. This "light" and "heavy" description bothered me when I first started revolver loading two years ago. It particularly bothered me afer I realized I had no bullet jump in that 640 / 38-Special-17+grains-of-AA#7-under-a-140LTC experience. Yes, I had been applying a "heavy" crimp.

So, I did set out to try to quantify it, besides the "look at it" routine. What I have found is that, given my particular and fine-tuned swing, four raps or more to remove the bullet with an inertial hammer means it is a heavy crimp.

Personally, I use shorter 'raps,' not full-arm swings when I use the hammer. And, I use a wooden block on the concrete floor under it.

Keep in mind that the crimp amount will vary by the bullet's characteristics. For example, the Speer 158LSWC-HPs appear to be 'undersized' and one has to noticably step up the crimp, as compared to the house-brand 158LSWCs from my LGS. IOW, you need to set that crimp for each bullet you use--and it may vary not only by brand but also by bullet-production runs.

Given the fact that I use a Lee FCD as my 4th / crimping die, I have been able to tweak its settings--particularly the body height--so that a full range of crimp can be dialed in, once it has been set for the bullet being used.

Two years later, I do mostly rely on a visual inspection--but each time I change out bullets, etc., and go through tweaking the crimp, I do double-check with the "four-raps-plus" test.

Jim H.

 

[Walkalong]

This "light" and "heavy" description bothered me when I first started revolver loading two years ago.

Dang it jfh, I still mark it down in my load book like that, light, medium light, medium, medium heavy, heavy, etc. I am so low tech.

 

[243winxb]

If your roll crimp isn't adequate, do the bullets creep out or slide deeper in? What is the main danger here?

They Creep out from recoil in a revolver, to much and they lockup the cylinder. The bullet is held in place by the brass case. The expander opens the case to the correct inside diameter after Full Length Resizing. The crimp helps some, but now a whole lot. For a proper crimp, and there is only one, no lite, or heavy IMO, the brass must be trimmed to the same length, with in a few 1000's. Then seat a bullet to the correct OAL without crimping. Now turn down the crimper by hand onto the loaded round as tight as you can. Back off round, turn die down another 1/8 turn. All set.

Should I go back and recrimp all the lighter loads a bit to make sure they are safe?

I would not, unless there is movement on firing. Check the last round in the cylinder after firing 4 .

 

[jfh]

"...I still mark it down in my load book like that, light, medium light, medium, medium heavy, heavy, etc. I am so low tech."​

Heh, IIRC, I even pestered you about what "light" and "heavy" looks like. Somewhere along the way, there have been good pictures (yours?) posted, too.

But, I really did have trouble, at first, figuring out what "light' and "heavy" meant--particularly after I thought I had it figured out, and then tried some Speer 158LSWC-HPs.

So, the "rapping" scale is the one I check crimp with now--at least when I set up a new load.

Jim.

 

[Walkalong]

Like this "Medium" roll crimp.

Light, medium, and heavy are in the eye of the beholder.

My medium may be something else to someone else.

 

[jfh]

Excellent, truly excellent.

How about doing a whole series--but with a white paper background?

Jim H.

 

[Tequila Mockingbird]

The Lee factory crimp die is one of the best tools for getting the crimp right. Just follow the directions, and you really can't go wrong. And the FCD is cheap; I think they run less than 15 bucks.

 

[buck460XVR]

With handguns, the bigger the kick, the more the crimp. Most of my H110 loads have a tad more crimp than Walkalong's and my Unique plinkers a tad less. Cases generally get three or four heavy crimps before being tossed into the plinker box. The .460 cases generally grow enough by then, so I trim and start over. I too use the eyeball type gauge.

 

[Clarence]

The eyeball method has yet to let me down over the last 30+ years of reloading.

 

[ranger335v]

"Two years later, I do mostly rely on a visual inspection--"

"The eyeball method has yet to let me down over the last 30+ years of reloading. "

"It's a visual thing, you will develop a "feel" for it."


No experienced loader tries to "measure" his crimps.

 

[jfh]

yes, one obviously develops a feel for it.

However, the OP is querying about making a (roll) crimp with no experience at it. Having some sort of "objective criteria" does give a reference to use until one "develops" a feel for it. The standard answer is to look at a factory round. The trick or a beginner is learning how to create that kind of crimp.

Reloading is an art--and fundamentally, at the most limited base, it is a series of operations that can be described 'precisely' and visually. The problem is, getting all those steps in the right order to reliably produce the crimp one needs for a given round.

What I'm hoping can come out of this thread's discussion is a series of really good pictures (by Walkalong) that can be a sticky.

Jim H.

 

[Sunray]

You don't measure it. 'Enough to keep the bullet in place' is the measurement. As daft as it sounds. 'Enough' isn't a whole lot either. Less is better.
"...3.5 gr Bullseye charges..." Shouldn't need any crimp.

 

[The Bushmaster]

"The Lee factory crimp die is one of the best tools for getting the crimp right."

I have to disagree on this one. It's just handy and an easy way out. You still have to learn how to use it too. Besides you should to learn to walk before you fly. If you don't know how to roll crimp with your seating die you will have no idea what a crimp should look like. One should learn all aspects of the reloading of his particular cartridges. I profected the crimp on my .30-30s and .38 Specials before I decided to go with the FCD...Then went back to roll crimp on my.38 Specials.