loading 357 on lee turret, do I need to seat and crimp seperately?

[Petrol & Powder]

I don't see how performing the operations separately would negate the need for cases to be of equal length, or at least very close. With a roll crimp, would not a longer case get more "bite" on the bullet than a shorter one, regardless of whether you seat/crimp it in one step or two? A consistant crimp is fairly important to getting consistant results, in my book, especially when you are pushing the performance envelope a bit. JMHO

When the seating stem is pushing the bullet into the case at the same time the die is pushing the brass into the crimp groove, small variations of case length can give you headaches. Maximumbob54 hints at that problem.

These aren't huge issues across the broad but we all find the methods we like.

[str8wal]

When the seating stem is pushing the bullet into the case at the same time the die is pushing the brass into the crimp groove, small variations of case length can give you headaches. Maximumbob54 hints at that problem.

These aren't huge issues across the broad but we all find the methods we like.

This doesn't answer my question. I still don't see how you can get a consistant crimp if the cases aren't of equal length or very close to. A short case will not have the same crimp as a longer one regardless of whether you do it in one step or two.

[str8wal]

Set the seating depth on a case that's slightly shorter than some of the rest and you will quickly see what happens as it tries to crimp at the same time.

Right. But this still doesn't address the issue of crimp consistancy. A shorter case will not have the same degree of crimp as a longer one regardless of whether you do it in one step or two.

[Carrier]

This doesn't answer my question. I still don't see how you can get a consistant crimp if the cases aren't of equal length or very close to. A short case will not have the same crimp as a longer one regardless of whether you do it in one step or two.

I use the seating/crimp die as well. Been told that I should be using a separate crimp. Like you I don't see how it would make a difference either.

[bzajdek]

I wonder if most people seat and crimp revolver or roll crimps in one operation, what is so different about a taper crimp on an auto loader?

[Petrol & Powder]

This doesn't answer my question. I still don't see how you can get a consistant crimp if the cases aren't of equal length or very close to. A short case will not have the same crimp as a longer one regardless of whether you do it in one step or two.

Fair question and a valid point to discuss.

If you are seating & crimping in one step the bullet is being pushed down in the casing continuously until the end of the ram stroke AND the die is simultaneously pushing the brass in on that bullet up until the ram bottoms out. If you set that combined seating/crimping die up on a case that is shorter than the rest of the casings in the batch the remaining longer casings will end with the bullet relatively deeper in the brass (the distance from the case head will be the same but bullet will be deeper in the longer casing) and the roll crimp will start higher on the bullet. This can result in the case mouth catching the driving band in front of the crimp groove as opposed to falling into the crimp groove.
The opposite happens if you happen to set the die on an aberrant longer casing. All of the subsequent shorter casings will have bullets that are not seated deep enough (relative to the case mouth) and the roll crimp will catch the driving band below the crimp groove.


NOW, if you seat in one step and set the seating depth so that the edge of the case mouth ends up somewhere between the middle of the crimp groove and the top of the crimp groove when the bullet is fully seated you will have several thousands of an inch (.001"-.015?") to play with in which a perfect crimp can still be obtained. Because the bullet is not still being pushed into the casing when the crimping process is started you have a larger window in which a good crimp may be obtained.

Let me be perfectly clear - BOTH METHODS ARE CAPABLE OF PRODUCING QUALITY CARTRIDGES!
It is NOT a matter of which method produces better ammunition. It is a question of which method is more forgiving of slight variations in case length. If all of your casings are exactly the same length and you set your seating/crimping die appropriately, you will get perfectly good crimps on all of your completed cartridges. The seating stem will bottom out the bullet in exactly the right place at the instant the roll crimp is completed.
However, if you seat & crimp in two separate operations and there is a little variation in your casing lengths you can still get acceptable crimps on all of your completed cartridges and not need to worry about a few thousands of an inch difference between your longest casings and your shortest.

As I said earlier you are just trading one step (trimming cases) for another step (separate crimping). We're not talking about huge variations in case lengths, we're talking small spreads that can easily be accommodated within the upper 1/2 of the crimp groove.

I load my pistol cartridges on a progressive press and the separate crimping operation doesn't add to my work load but trimming 1000 cases would.

[str8wal]

It is NOT a matter of which method produces better ammunition. It is a question of which method is more forgiving of slight variations in case length.

So then you are sacrificing consistancy of results for simplicity of procedure? I can understand that if production of product is the goal rather than quality of product. In my experience, trimming is required only once with straightwall cartridges so that step becomes irrevellant in subequent loadings. If all one is using their ammo for is pinging steel silhouettes at close range I can accept that rationale, but when one intends to use their handloaded ammo to take big game at much further distances, there is much less room for error and crimp consistancy becomes much more relevant, IMO.

[opos]

I don't hunt...too old and too beat up...but did for many years....I now just shoot paper so if my groups are not a clover leaf every time...who cares? Years ago I thought I'd like to trim my handgun cases to the same lengths for "consistancy" of crimps...I'm a cheap skate so I use lee trimmers...they are a fixed length...I bought one for my 45 acp and found that most of the cases were shorter than the lee fixed length so there was no way to trim....so I put it in the drawer and the thousands and thousands of rounds I've loaded have not been trimmed...I don't trim "roll crimp" rounds for the same reason...

Now if you want to spend bigger bucks than I'm willing to spend you can get a trimmer that will give "infinite" lengths and you can trim all to the shortest length....I'm too lazy and too cheap to do that...I trim all my rifle rounds (lee trimmer) but they stretch when being fired where handgun brass shortens on firing...my 2 cents.

[Petrol & Powder]

str8wal - I hear you but I wouldn't characterize it as "sacrificing" consistency for simplicity of procedure. I would consider it to be achieving consistency while maintaining high production.

It's not like we're talking about casings that vary by 0.025" in length but rather 0.005" over hundreds of casings.

It's easy to start splitting hairs in these endeavors but I'm with opos on this one, there comes a point of diminishing returns and I think that the limit of diminishing returns occurs long before we get to the point of needing to trim handgun cartridge casings.

I'm not a fantastic marksman with a handgun but I can hold my own. If trimming cases allows you to extract a little more accuracy from your handgun ammunition that you can notice; more power to you. It's just not worth it to me nor can I justify the time spent with improved results.

Now, with bottle neck rifle cartridges - That's an entirely different game. I always trim those cases and I take a great deal of time to make the most consistent cartridges possible. That's not to say that handguns can't benefit from careful case preparation but the returns for that work on handgun cartridges are overshadowed by other factors.

Again agreeing with opos, I've seen little, if any, need to trim handgun casings and by using a two step seat & crimp process I can achieve high production rates AND excellent cartridges.

[David2011]

Doesn't matter what kind of press you're using. Some of my molds produce boolits that shave lead if seated and crimped in one operation. It seems like smaller diameter boolits are more susceptible to this than larger ones. The depth and length of the crimp groove is very important to allowing crimping and seating in a single operation as is a consistent overall length. With heavy recoiling rounds the crimp has to be good, especially in revolvers, to prevent the cylinder from locking up. A consistent crimp also helps obtain more consistent ignition.

I agree with opos about .45 ACP. I've never seen one that was the maximum overall length and some of mine have been shot until you can't read the headstamp.

Cartridges that are roll crimped will be more sensitive to cartridge length and crimp groove than taper crimped cartridges. Taper crimping is very likely to cause lead shaving if done while seating. I always taper crimp as a separate operation.

David

[1hole]

David - "Doesn't matter what kind of press you're using."

That's the answer to the question.

How picky someone is about crimping is the real issue and consistency of case length IS the controlling factor for that, not the press. Lee's 'factory crimp' dies (rifle and handgun) are the most tolerant of modest variations in case lengths.

[RogerDat]

If you are roll crimping you need to have all the cases the same length. This means trimming. Lee makes an inexpensive option that works excellent. I crimp and seat in one die.

I'm using a Lee Quick Trim with the hand crank but hoping to get the head that allows using a power screwdriver to drive the cutter. I'm often doing range brass for revolver, stretch is not really an issue once I get everything trimmed to a common length. I want the roll crimp to be consistent which means the brass length has to be consistent so I trim once and then I only re-trim if I see a specific issue. If I was purchasing new brass and reloading it or reloading my own store bought rounds that were already pretty consistent I might feel less need to trim. Lord knows it is my least favorite activity in reloading.

I mostly use two dies for seat and crimp, as others have said less complicated to adjust each die for a single operation. I will also sometimes do a large batch of some caliber and switch bullets from RN to SWC to WC etc. Crimp is at same place since the brass is the same, most often the only real adjustment needed is to the seating die. I'm using a 4 hole Lee turret press. Size/decap, Powder through expander, Seat, Crimp. However for a couple of calibers I have singe die for both operations and am generally using the turret press with the indexing rod removed and powder measure off press, so a little different for bolt rifle cartridges.

[DaveInFloweryBranchGA]

I do have the 4 hole classic turret, BUT because I use a lyman m die to expand and the lee powder die with a lee pro auto disk i am out of room on the turret. I have read about NOE powder through expanders for the lee powder die, there was either a problem with the revolver or auto ones not being long enough to actuate the powder measure and they were going to make the newer ones longer. I read it in a thread on this forum.

To gain back the die space on your Lee Turret head, go to NOE and buy his Lyman M-die style expanders for the Lee powder through die. Then you can separate seat and crimp operations again while having the best of both worlds. You can sell your M-die or use it in another application.

To me, that's the simplest way to resolve your issue.