I have always used the traditional roll crimp on revolver rounds. However, a couple of recent events have me thinking of taper crimping for revolver rounds. Here is what leads up to this question...

A fellow on another website made a statement that started me thinking. He said he taper crimps all his .357 Magnum rounds instead of the more common roll crimp because the taper crimp applies even pressure concentrically around the entire bullet base within the case. In his experience this provides a much stronger and consistent crimp that resist bullet creeping much better than a roll crimp. He said to prove the taper crimp is better, take two rounds with identical bullets and a decent crimp pressure for both, one roll crimped, one taper crimped, and put them in an inertia hammer type bullet puller and whack away. The roll crimped one will come unplugged much easier than the taper crimp. That started me thinking...

The next event was that just because, I bought a new set of RCBS Carbide Dies for the .357 Magnum/.38 Special. I have two other sets for the same cartridges, but they are getting a little rough and I just wanted the new set. To my surprise, this die set came with a taper crimp die for the revolver round instead of the more common roll crimp. Interesting...

As I began to mull this over I started thinking about how hard it can be to really know the amount of crimp you are putting on a bullet with a roll crimp. That is a thing that experience and feel develops after loading and shooting quite a bit. It isn't too hard to over crimp a roll crimp. When that is done, you actually lessen the grip on the bullet. That little bulge from over roll crimping is the case buckling away from the bullet and loosing tension. Of course, that can also cause the round to not chamber in the cylinder. Both are problematic. Additionally that cannot be a good situation for uniformly consistent velocities and accurate ammunition.

Then there is the matter of repeatability with roll crimps. Once you've found an accurate consistent load, if you reset your die at some point and then come back later to load another batch of those first rounds, how do you accurately get the same amount of roll crimp? Other than guessing and by feel, how can you accurately measure the amount of roll crimp for consistently reproducing that special load you developed?

A taper crimp actually does apply pressure around the entire bullet base evenly. So in this case it isn't just a lip of brass in the cannelure or crimp groove that is holding the bullet. Isn't this pressure surrounding and gripping the entire bullet base a stronger union than the roll crimp? This should also provide a more consistent bullet pull and allow propellant gases a more even burn. Wouldn't this be better ballistic? More accurate?

And finally, isn't it easier to repeat a taper crimp by measuring the case in the same place near the case mouth. As an example, I taper crimp my .45ACP rounds for my 1911 semi-auto handguns to a consistent .470." I can repeat this amount of crimp from brass lot to lot, various bullets, or in the case of special loads I can duplicate this over and over time after time. Why would this not work for a revolver round as well? Find a suitable amount of crimp, measure that, make a note, and you can always replicate the crimp on future batches of that particular loading.

Am I making sense, can you follow my train of thought? Or, am I derailed?

Sgt Preston here. I'm with you on this. I taper crimp all my rounds for all calibers. I feel like I get a better fit, a snug hold & more consistent overall lengths. I also set my crimp die to give me the OD I am looking for. I use .469 / .470 for my 45ACP'S. I have similar dmiensions for my 9mm's & 38 specials as well, but the numbers are written down at home & I'm at work (lunch). And best of all, my rounds will all fly to the center of the target everytime IF I do my part correctlty. I never had "fliers" since I've been loading. Sgt Preston USMC LLA

As long as you are putting a good, stiff crimp on the ammunition, it doesn't matter.

There are only two concerns which may affect you on this...

Speed of reloading- which if you use the taper crimp, you will have an edge on the brass like an auto pistol round which is not desired if using them during fast, timed events with unchamfered cylinder chambers.

The other concern would be bullet pull if you are using them in an extremely lightweight revolver such as a 340PD or similar. The roll crimp goes over into the bullet groove and better holds the bullet in the case against "jumping."

My two cents.

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A taper crimp actually does apply pressure around the entire bullet base evenly. So in this case it isn't just a lip of brass in the cannelure or crimp groove that is holding the bullet. Isn't this pressure surrounding and gripping the entire bullet base a stronger union than the roll crimp? This should also provide a more consistent bullet pull and allow propellant gases a more even burn. Wouldn't this be better ballistic? More accurate?

It is a good idea to know what kind of dies you are using, some of them will give a taper crimp and a roll crimp, depending on how far down you adjust it.

Many people will tell you they get better accuracy with a taper crimp, and they do. They will also tell you they don't trim their pistol brass and this is why. If you want consistency you must load with consistency.

First off, in a revolver it doesn't matter what type of crimp you use. The reason it can become a factor is if it is too small and an auto round can't seat on the case mouth. Use whatever suits your fancy.

For me, a traditional roll crimp for revolver rounds BECAUSE I use bullets designed for it. Most of mine have an "Elmer Keith style" crimp groove. I like it that way. I guess I should backtrack a step though, I use no crimp on my light target rounds. I just close the case mouth back to straight and seat the bullet so that only about .030" of the last driving band is showing.

As for setting up your dies for a new batch, here is how I get in the ballpark.


Like I said almost all of my bullets, and I cast my own, have one kind of crimp groove. All I do is fill it with case.

Skip, they are truely magnificent looking rounds! Let me clarify for some of our other readers why I use taper crimps on all my rounds. I do all my shooting ia a new indoor range which has a state of the art air filteration system. The idea here is to get the lead & toxic gases away from the shooters. I have medium ++ blood lead levels, so no lead is a good thing. That said, the range owner requires either total copper plated rounds or total metal jackets. FMJ, all lead or partially plated rounds are prohibited. This even applies to 22's. I use Berry's Copper Plated Rounds & they do not have the cananlure groove. The copper serves as a lubricant on not "bullet lube" is required. So the taper crimp works very well on my "straight wall" bullets. Sgt Preston USMC LLA

Ok, I’m OCD… I decided to experiment with the two crimps this afternoon and see what results I came up with. I began with twelve new unfired Remington .357 Magnum cases. I trimmed them to the same overall length for consistency, then lightly chamfered and deburred the case mouths. Next I full length resized each case with the new set of carbide dies from RCBS. Then I applied a slight flare of the case mouth. No primer or powder charges were needed, or wanted, for this experiment so I skipped those steps.

For bullets I choose six Oregon Trail hard cast 158 gr. SWC, and, six Remington bulk pack factory 140 gr. SJHP's. With the seater die screwed out far enough to not apply any crimp I seated each of the bullets as one normally would at the appropriate depths. The hard cast was seated to the crimp groove and the semi-jacketed hollow points to the middle of the cannelure groove.

I now separated the twelve into two groups. Each of the two groups had three 158 gr. hard cast SWC, and, three 140 gr. SJHP. I applied a fairly heavy, not excessive, roll crimp on Group R's (R for Roll Crimp) three SWC's and three SJHP. This was the type of crimp one would apply for a heavy magnum type load.

Group T (you guessed it - Taper Crimp) got a taper crimp. Here is where I had to do a little speculating on the right amount of taper crimp to apply. How much taper crimp would be the right amount? All I had to go on was experience with semi-auto loading and the feel of the case in the crimp die. The .45ACP case mouth specs at .473" and a very commonly accepted taper crimp for this semi-auto is .470". So three thousands of crimp is expected to hold heavy weight jacketed .45 bullets as it slams its way from the magazine, is shoved up the feed ramp, and into the barrel. This amount of crimp also prevents bullet set back in the magazine of the gun and from repeated chambering as a semi-auto is unloaded and recharged, ect.

The .357 Magnum specs at .379" along the side walls at the case mouth according to the drawings in the load manuals. I began taper crimping Group T's bullets to .375" but it really didn't feel like much crimp was being applied. I kept fiddling with the amount of crimp, trying to get the same resistance on the press as when I roll crimped the first group. I quit at .370" that felt like the same resistance as the more familiar roll crimp. Plus, nine thousands of crimp seemed like a lot.

I grabbed my inertia hammer type bullet puller and went out in the garage. The concrete step leading from the garage floor into the house would be my striking point. I started with Group R 158 gr. SWC. Trying to use a controlled and smooth swing I beat the bullets out of the three 158's. It took nine whacks each to unload these. Next was Group T's 158 gr. SWC's. It took only seven whacks each to uncork these. Hummm... the roll crimp held better than the taper on these two lots.

The 140 gr. jacketed hollow points were next. Group R held until the tenth hammer strike. Again, Group T let loose earlier at the eighth hammer strike.

I know this isn't a very scientific experiment and the data base of only three samples of each bullet per crimp type isn't perfect. With that said, I am fairly certain we've been doing it right all along... roll crimp those heavy recoiling revolver rounds.

Since the taper crimp hold so much better, wouldn't that increase the pressure of the round? If it takes that much more to pull a bullet = more pressure to move it!! right or wrong?? Later John

OK GC,
(I love your byline by the way. Sounds like what I have told all 5 of my kids growing up!)

The most important thing learned here is not that we have been doing it right all along though. The most important thing learned is that most folks have opinions and can be just as wrong as us given the opportunity!

I believe there are few things that need to be figured out again when it comes to handgun loads. Bigger, sure. Faster, sure. Different bullets to do different things, sure. But when it comes down to it, the loading practices figured out by the old timers will still work, and quite frankly, most of the time better than what comes out today.

I understand what the Sarge is saying. If I shoot plated bullets in my revolvers, which I almost never do, I would still use a roll crimp. The plating is not hard enough to keep my die from making it's own cannalure. If you use a Speer Gold Dot in the 500 S&W Magnum you had better use a crimp of some kind. I did. It was a roll crimp from an RCBS die and it made it's own crimp groove. If the pressure in the cartridge is where it should be, it will have expanded before the bullet moves any at all, nearly.

Like I said earlier though, my lead bullets are designed for the heaviest crimp of all. One designed to make a slow pistol powder ignite completely. Just like a whole bunch of 2400 in a 44spl case way back in the '40s and '50s!

I have taper crimp dies on all my Dillon shell heads for revolver rounds and I've always liked the consistent result I get. But one word of caution - with a heavy taper crimp it is possible to have a 44 mag round that may actually chamber in a 44 special cylinder. The ramification of that could be catastrophic, as in addition to the hotter round, there isn't sufficient clearance when the round fires to open up the full chamber length thus driving pressures through the roof. Very bad things will happen.

Just out of curiosity I wanted to see how deep the chambers were on my 696. Factory magnums - seated out as expected. But out of a dozen taper crimped 44 hand loads I tried, two chambered to the rim. They were tight, but they chambered. And the cylinder on the 969 is long enough to accomodate a round that long. An 'accident' waiting to happen. Made me re-think taper crimping the mag loads. Just a word to the wise . . . .

I too use a taper crimp die on all of my revolver catridges. The especially help when shooting competition and every milisecond on the reload counts.

Tapered go in much faster. If you rool too much that case will not co in the cylinder.

Just taper enough to hold the bullet, not enough to damage the shape of the lead. Try it a few times and when it's set you will just leave it alone forever.

BTW, I never trim before sizing, except today for some stupid reason. I was in a hurry and for some danged reason that is the order I went at it today. I didn't even realize it until I typed my second reply. When I typed it, it suddenly struck me what I had done and I thought, "Why in the world..." Pays to stick to your routine in the loading room and keep your head in the ballgame. Straight wall pistol cases aren't too critical fortunately and I'm not all that worried about those twelve cases. But it is noteworthy.

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Since the taper crimp hold so much better, wouldn't that increase the pressure of the round? If it takes that much more to pull a bullet = more pressure to move it!! right or wrong?? Later John

Right.

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If you rool too much that case will not co in the cylinder.

Seating and crimping in two seperate steps should cure that problem.

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I too use a taper crimp die on all of my revolver catridges. The especially help when shooting competition and every milisecond on the reload counts.

What caliber revolver do you use?

What kind of competition do you shoot it in?

I have been taper crimping (RCBS dies) my 342ti 125gr xtp loaded with 5.1 gr unique. I have not been able to crimp them tight enough to keep from jumping. Sounds like I need to get me a roll crimp