Loading 357 magnum pistol: is flaring and crimping necessary?

I load centerfire rifle for 25-06 and 300 Win Mag. I have bolt action rifles and don’t crimp. I am starting to load 357 Mag pistol bullets. Is it necessary to flare the case mouth? With rifle I usually have boat-tail bullets with cooper cladding, friction bullet seating is fine. If loading lead flat-based pistol bullets, I can see how getting bullet into case rim might shave bullet without flaring. If loading FMJ bullets is flaring still required. And if shooting in a revolver is crimping required for pistol? I have a Pacific Durachrome 3 die set for straight wall cases with 3 different seater plugs. I bought this die set 30 years ago and loaded 1 box of ammo and started buying factory ammo after that. I recall using the flare die but now I can’t remember why or if required. Thanks much, new again to pistol reloading.

Not as much as with cast bullets but you do need to slightly flare the cases for jacketed bullets. Just enough to guide the bullet into the case when seating. If you don't flare, good chance of the bullet crushing the case when you go into the seating die. Roll crimping is strongly suggested as well. If you don't crimp, the bullets will tend to back out of the case with recoil. The crimp doesn't have to be excessive, just enough to firmly hold the bullet in place.

So is the flaring die dimensioned such that the OD of case mouth still does not exceed the OD of a new case and still chambers fine (cylinder of revolver)? I’m assuming the full length resizing reduces the OD down (after expanded ball passes thru) so that you can still flare and chamber fine?

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Originally Posted by Rmiked

So is the flaring die dimensioned such that the OD of case mouth still does not exceed the OD of a new case and still chambers fine (cylinder of revolver)? I’m assuming the full length resizing reduces the OD down (after expanded ball passes thru) so that you can still flare and chamber fine?

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Crimping after seating the bullet should remove all of the flare. The flaring/expanding the case mouth should not effect the majority of the body of the casing, it should just expand the case mouth and possibly expand a small amount into the case due to the expander plug.

ETA: In my opinion crimping all revolver cartridges is a necessity due to the possibility of bullet pull during recoil. It is easy to do, most seating dies can be set up to seat and crimp at the same time.

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Originally Posted by jws

Crimping after seating the bullet should remove all of the flare. The flaring/expanding the case mouth should not effect the majority of the body of the casing, it should just expand the case mouth and possibly expand a small amount into the case due to the expander plug.

ETA: In my opinion crimping all revolver cartridges is a necessity due to the possibility of bullet pull during recoil. It is easy to do, most seating dies can be set up to seat and crimp at the same time.

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Yes, my Pacific Durachrome seating die will seat and crimp simultaneously. It also came with 3 different seater plugs to match bullet nose shape. Thanks for advice. I failed to consider the flare would be removed when crimping. I was thinking I would seat only with friction fit but now see the wisdom in a slight crimp.

Yes, and yes.

Excess belling/flaring may overwork the case mouth and cause it to fail prematurely, and if you really overdo it, you may have trouble getting it to pass through the seating die. Too little, and you’ll shave bullets, ruin concentricity, smash cases trying to seat in some situations.

Crimp is necessary to get proper ignition from some loads and to prevent bullet pull in adjacent chambers.

I use a separate crimp die, and just use the seating/crimping die for seating.

I flare and crimp because it's standard procedure for .357 loading. Also recommended by loading manuals.

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Originally Posted by Duelist

Yes, and yes.

Excess belling/flaring may overwork the case mouth and cause it to fail prematurely, and if you really overdo it, you may have trouble getting it to pass through the seating die. Too little, and you’ll shave bullets, ruin concentricity, smash cases trying to seat in some situations.

Crimp is necessary to get proper ignition from some loads and to prevent bullet pull in adjacent chambers.

I use a separate crimp die, and just use the seating/crimping die for seating.

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This.

Revolvers can be extremely accurate, even at long range, but there are some tricks.

The first is to use flat-based cast bullets sized to .002-3" over bore diameter. From there you want to ensure that bullet pull, which is the tension that the case exerts on the bullet, is uniform. Most people loading for accuracy size normally, then use a slightly undersized expander, such as a .410" for the 44 Special and Magnum. This results in a loaded cartridge with a little waist on it like a Coke bottle just below the base of the bullet. This, combined with crimp, helps make ignition more consistent.

Bell the case just enough to let the bullet stand upright in the case mouth unaided before seating. Sometimes this amount of belling is easier felt than seen. Your goal is to prevent damage to the heel of the bullet. If you damage the heel in any way, then throw the bullet away, bell your cases more, and continue on.

Seating seating and crimping in separate steps tends to increase accuracy, especially as range increases. I've been doing it for decades. I think you get a more consistent crimp because you're not driving the case up around the bullet while you're also crimping it.

Don't go too light on the crimp. (Rimless straight-wall cartridges need a taper crimp because they headspace on the case mouth. Revolvers headspace on the rim, so you can use a roll crimp that might cause misfires in a semi-auto. Your 25-06 headspaces on the shoulder and your 300 WM headspaces on the belt.) Revolver cartridges with a heavy roll crimp tend to be more accurate than those with a light roll crimp because the crimp and bullet pull help to make ignition more consistent.

The 45 Colt cartridge in this image has about the right amount of crimp and you can see the "waist" below the bottom of the bullet. If you look closely, then you can also see the lube groove in the bullet through the case about halfway between the crimp and the waist.

Attachment 66855

This advice pertains to maximizing accuracy in magnum and near-magnum revolver loads from the muzzle out to several hundred yards. The art of creating super-accurate revolver loads for use inside of 50 yards is focused on reducing recoil to reduce wear and tear on the shooter. Those loads are no more accurate than ammo loaded as I've described but the shooter tends to flinch less at the end of a long string of fire, and that's where matches are won.


Okie John

Thanks for the very detailed explanation. I have not measured the diameter of my expander plug in my Pacific die. I’ll note that dimension when I resize my next case.

I reload 9 calibers and every case is flared. For some, especially cast bullets, the flare is larger than plain based jacketed and boat tailed bullets get less or none. It's kinda hard to push a .308" slug into a .305" tube without some sort of "entry way". Even with cartridges I don't crimp, I'll use a crimp die to straighten out any flare. (I tell new reloaders to flare as much as you need to be able to seat bullets straight to get good shootable ammo now, and worry about case life later). Flaring revolver cases is almost a necessity as many times cases will be ruined/crumpled by trying to shove a .358" slug into a .355" tube and bullet damage (jacketed too) is common with too little flare. Too much flare is when the case won't enter and/or scrapes the ID of the seating die. All flare is removed from flared revolver rounds with the crimp die. My semi-auto rounds aren't crimped but deflared with a taper crimp die. Most of my rifle handloads aren't crimped, but I normally use minimal flare, check the rounds for chambering and if necessary (rarely) I remove flare with either the stock crimp die (just touch the case mouth to deflare) or I have several collet crimp dies to just deflare. Case life is an issue, but for a reloader not familiar with flaring/seating/crimping it's better to get good shootable ammo now and after his methods are refined from experience, then worry about case life...