Not done any crimping but have been enjoying reading the theory, potential benefits and actual outcomes. Just one thing I'd like to clear up though - am I right in thinking seating dies that can also perform this operation will use a roll crimp, which is only suitable for bullets with a cannelure? ie, if I wanted to see what affect a crimp would have on a 40gr V-Max load, I'd need something like the Lee Factory jobby?
Crimping - different dies for different results?
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Steff
Well-Known Member
Correct in your assumptions.
But crimping is only beneficiary for bullets that might actually move due to outside physical impacts such as recoil.
Crimping a 40 grs. bullet is like wearing two belts and three pairs of suspenders at the same time.
They will not become more accurate if your case prep is otherwise halfway decent.
But crimping is only beneficiary for bullets that might actually move due to outside physical impacts such as recoil.
Crimping a 40 grs. bullet is like wearing two belts and three pairs of suspenders at the same time.
They will not become more accurate if your case prep is otherwise halfway decent.
Rifle I don't crimp other than M-2 Ball recreations I feed my M-1, 44 mag I roll crimp. I agree with no roll crimp with no crimp groove. I have yet too taper crimp and never have used the Lee factory crimp die. You may see better accuracy or worse or no change I cant predict one way or another. I should add seating and roll crimping is a separate task imo. RCBS says it can be combined however I am sure brass will be wrecked and prefer separate operations
Crimping is bad. Really not worth the effort unless you use a heavy recoiling rifle as was stated above. Despite what people claim, it does nothing to lower the extreme spread of your cartridge velocities. Nor does it, as widely claimed, add any degree of uniformity to your loads. (One enlightened fellow even shared the wisdom of his stockist who said quite confidently that crimping adds one more undesirable variable to your loads. A shopkeepers word is above contestation!) The fact that most factories crimp their production ammo is simply an archaic hold over from past times continued by engineers and ballisticians who have not yet learned the wisdom the internet has to offer. Avoid it. If you do dabble in crimping any die will do, but don't use the Lee Factory Crimp die with trimmed cases. You'll have wasted both time and money. JMHO ~Muir
(whew)
(whew)
Did you mean to say 'Don't use the Lee Factory Crimp die with untrimmed cases' ?
Steff
Well-Known Member
As of his third sentence he meant to say the exact opposite of what he wrote.
Whew indeed, a lucky escape...
(Just a question of sarcastic consistency though: does 'any die will do' translate to 'only a non-roll crimping die will do'? Just in case I wanted to create a real mess of my loads...
)
I use the Lee Factory Crimp Die as I was finding seating bullets took variable pressure, even on annealed cases sized with Forster dies and good case prep (I think). It has to add some sort of consistency to neck tension, but mostly because Muir is a proponent of it.
Steff
Well-Known Member
I you want to crimp use a collet crimp not a roll crimp.
Thanks for the confirmation Ed.
I think there is enough conflicting opinion here to warrant my own experiment one day...
No. The second assumption (that I have italicised) is incorrect. A very LIGHT roll crimp can be applied to bullets with no cannelure or, as sometimes, with the cannelure in (for your loading) an inconvenient place.
Or of course on a cast bullet with a crimp groove or even indeed a suitably located lubrication groove. Or even with a shouldered bullet (think semi-wadcutter) over the front of that shoulder.
The Lee "Factory Crimp" isn't actually a factory crimp as such. It uses a three finger collet to crimp using a variation on the principle of what was once called a "stab" crimp. That is the fingers (can be three or can be four) come inwards and "stab" the case neck inwards. Many rimmed British military cartridges and commercial cartridges used a "stab" crimp.
What the Lee "Factory Crimp" does is, in effect make that "stab" at the very very end...the mouth...of the case's neck. If you look closely you'll see three small "nibs" that aren't stabbed in. These correspond with the vertical gaps between each of its three collect fingers.
Another style of crimp that also needs a separate operation from the seating process is a "taper" crimp. It's most often seen on nominally straight sided self-loading RIMLESS pistol cartridges that headspace on the case mouth. These might be .45 ACP, 9mm, and .380 ACP aka 9mm Short.
An old British name for the process of adding a "taper" crimp explains well what happens...that old name was "coning". Now a "taper" crimp or "coning" works fine in stopping the bullet coming OUT of the case but ineffective at stopping the bullet being driven IN to the case.
So you'll often see military .45 ACP that has a rolled cannelure below the bullets' bases. To stop that inward movement. As here below.
However there are some straight sided self-loading pistol SEMI-RIMMED pistol cartridges such as .455 Webley Automatic, .38 ACP and its re-incarnation .38 Super and .32 ACP that are roll crimped. That's because the original as designed headspaced on that narrow semi-rim.
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4 topics should be barred on here 1 knecksizing 2 boreguides 3 boresnakes 4 crimping
In my defence it started as a question of technique rather than pros and cons!
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