My Father used to reload and hopefully one day I will be able to get back into it, but I do have one question.

What is the difference between a roll crimp and a taper crimp?

Pictures would be helpfull if they readily show the difference.

Thanks.

Sir, if you have them handy, get out a straight-wall auto pistol cartridge (.45 ACP, 9 mm, etc.) and a revolver cartridge (.357, .44, etc.) and compare the case mouths. The revolver cartridge's case mouth will be pinched (crimped) into the cannelure of the bullet; this is a roll crimp. The auto cartridge's case mouth will be "straight" and not pinched into the bullet; this is a taper crimp.

Auto handgun cartridges use a taper crimp because they typically headspace on the case mouth. Revolver cartridges headspace on the rim, so the exact location of the case mouth is less critical than it is in autos. A taper crimp is basically a friction fit, like clamping something in a smooth-jawed vise. A roll crimp is more of a mechanical lock, which is good with magnum loads.

Hope this helps, and Semper Fi.

Ron H.

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Wishin' don't make it so.

don't have pictures, but...

A Roll Crimp is a slight inward roll of the cartridge case into the crimp groove (cannelure) of a bullet. It can't be used on bullets without the groove.

A Taper Crimp just "tightens" the casing around the bullet -- essentially, it removes the slight belling that occurred with the expanding die to allow the bullet to smoothly enter the case.

(Ron -- you covered more ground! Semper Fi. --vic)

Here is a picture of a .45 Auto Rim with a heavy for the caliber 250 gr NOE Lyman 454424 with a roll crimp.



Here is a .45 Auto Rim with a 200 gr H.P. MiHec
with a tapered crimp:



Dale53

Nice pictures & good descriptions.

What Ron said, to a "T".

Revolver cartridges that are loaded lightly can utilize a taper crimp if desired. Anything at normal velocity or above should employ a roll crimp to avoid having bullets "jump crimp" and tie the cylinder up. I think there are other things that can contribute to this, but crimp probably is the main factor.

This would seem to be a fairly rare occurrence; I have been around tens of thousands of revolvers cartridges fired by a lot of folks who were handloaders and never saw this happen.

A roll crimp tool rolls the top of case mouth into the bullet usually into a crimping groove or cannelure and is used for revolvers where the case does not head space on the mouth of the case. The first picture below shows a close up of a .357 mag with a roll crimp.



A taper crimp squeezes the ends of the case mouth inward along the side of the bullet but does not turn the case mouth in. The picture below shows an example of a .45 ACP case with a taper crimp. Notice the shiny ring just below the case mouth where the dies has worked the brass and pushed the sides of the case evenly against the bullet. The constriction of the case is narrower at the top of the case mouth than below it.

I just ordered the 9mm Luger w/roll crimp from Cabelas. As everyone knows, things are difficult to find in stock and I've been slowly assembling my Lock-N-Load AP for both 9 and 40. I feel like Dr. Frankenstein getting a plate here, a die there, ...

Since I couldn't find a roll crimp 9MM die set on the Hornady site, I just presumed that Cabelas had the description wrong, something that happens more often then I'd like!

I didn't want to miss the chance to buy. I can always return it but did I get the WRONG die set for my MP 9MM Pro????

Cabela's: Hornady® Custom Grade Pistol Dies

Good pic of crimps. Semi-auto rounds are taper crimped to facilitate feeding/headspace (9mm) and revolver rounds are roll crimped to prevent bullet movement...

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As I'm reading these replies, I have a question. If roll crimps are for revolver rounds to prevent bullet movement, and taper crimps are for auto loads, why does Lee sell a taper crimp for 38 spl/357? Also-if I use a taper crimp on my revolver loads, am I wasting my time?

A roll crimp is tighter than a taper crimp,which is important with slower burning powders.

I just got back from Cabelas and the guy in the reloading department said he uses the same die set for his 9MM semi-auto with no problems. THAT is the question I was asking Does anyone else have supporting or other opinions?

Also found out the nearby Cabelas has free reloading classes on Sundays. 2PM for intro and 4PM for intermediate. Can't wait.

The link you provided only shows a 45 acp and 480 Ruger which would have a roll crimp for revolvers.

What product number did you buy??

Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Handgun Reloading Dies :: 9mm Luger - 9X21 :: 9mm Luger-9 x 21 (.355) 3-Die Set

As to why there are taper crimps for 38/357 those can be used for Plated bullets or if you have a semi auto that shoots 38 Special.

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Occam's Razor

Could be they sold out. The item gets taken from their site. That's my whole problem, it doesn't give the Hornady part #. The Cabelas SKU is IK - 216132 for 9MM Luger. When it showed on the site, the description said Hornady New Dimension Pistol Dies Type II w/Roll Crimp. I just check the link and the 9MM is now sold out That's why I ordered without validating. I knew I could return them if need be. Hoping I don't have to.

Cabela's: Catalog Quick Order - Item(s) Found

Cabela's: Hornady New Dimension Pistol Dies

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Sorry, without the part number I can not say what you have coming??

I doubt that the 9mm would have a roll crimp.

The only way to be sure is call Calbelas and ask for the part number. I just looked in their master catalog and it does say roll crimp but again no Hornady part number. The list all the calibers together 2 are semi auto (9 and 40) the rest are revolver so it may just be the description is not clear.

You want a taper crimp for 9mm, which if I was a betting man it will be so.

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Occam's Razor

Many reloaders prefer taper crimps for revolvers using light loads (.38 Special especially) where neck tension is sufficient to keep bullets in place. I'm sure you can get both taper and roll crimp dies in every handgun caliber. For heavy recoiling loads (heavy loads, light guns) a taper crimp may not keep the bullets in place...

Also with experience crimping many, many rounds and a lot of care, roll crimps can be used on semi-auto ammo. For a beginner, stick to tried and true, proven methods.

Is the taper crimp indenting side of bullet (2nd diagram) a problem to be avoided on 9mm, or OK if some indentation occurs?

The roll crimp serves 2 purposes. To help slow burning powders build pressure for efficient burning and to prevent bullet jump under recoil.

In light range fodder with fast powder I just put enough taper crimp to make sure all belling is gone. My revolver seating/crimping die is a roll crimp so I back that off and apply the taper with the LFCD.

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A warm bed of smokin' brass

Yep, the center pic is too much crimp. Caption for the pic, explaining the crimps, was not included in my post...

Since the item has now shipped, Cabelas was able to get me the Hornady SKU. It is 546515 and I think I really want 546516, THOUGHTS???? Or will either work for my M&P 9 Pro?

515 -
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Handgun Reloading Dies :: 9mm Luger - 9X21 :: 9mm Luger-9 x 21 (.355) 3-Die Set

516 -
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Handgun Reloading Dies :: 9mm Luger - 9X21 :: 9mm Luger-9 x 21 (.355) Taper Crimp 3-Die Set

A taper crimp is normally used for light target loads using soft lead bullets without crimp grooves. Light target loads using fast powders don't need a roll crimp to prevent bullets from jumping the groove. A taper crimp also works the brass less, so it will last longer.

A common mistake is assuming that because a roll crimp is used to stop a bullet pull under recoil, a taper crimp in an auto prevents bullet setback. It does not, the taper crimp just undoes the case mouth belling done before seating the bullet. Too much taper crimp decreases neck tension and makes setback problems worse.