Projectile seating and crimping

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Projectile seating and crimping

Post by Blr243 » 29 Jul 2020, 11:50 am

About 20 year ago when I was experimenting crimping 357 loads for my Rossi , I was attempting to seat and crimp in the single operation and I gave up due to no success / possibly poor research. ...never crimped anything since. Now that I await the arrival of my 4570 marlin and I’m aware of the dangers associated with recoil/ bullet setback , I need to switch on and get it right....I have recently become aware of the separate Lee factory Crimp die ... I might add that the 4570 head spaces on the rim. Should I seat my projectiles and then use the factory crimp die as two separate operations? Another question.... In 243 and a few other calls I have for a long time preferred boat tails mainly for the easy bullet seating factor. I’ll bet my dog I’ll be waiting a long time before anyone starts producing boat tails in 458...... so when seating projectiles in 4570 , do we have to flare the case a bit , or do we just be real careful seating ?......if no case flareing die comes in my set, I have a lathe, I can make a nice flareing tool
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Re: Projectile seating and crimping

Post by boingk » 29 Jul 2020, 1:44 pm

Hi mate, if you've gone the Lee Pacesetter kit (red box) you'll have the lot. Full length sizing, expanding die (with powder-through function) and bullet seating die.

I've had no issues with the expanding die included, especially when using bevel based projectiles.

Check the Black Widow Range, they do bevel base in 350 and 405 but flat base only in the 500gn. Click here for the selection.
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Re: Projectile seating and crimping

Post by bladeracer » 29 Jul 2020, 4:31 pm

Blr243 wrote:About 20 year ago when I was experimenting crimping 357 loads for my Rossi , I was attempting to seat and crimp in the single operation and I gave up due to no success / possibly poor research. ...never crimped anything since. Now that I await the arrival of my 4570 marlin and I’m aware of the dangers associated with recoil/ bullet setback , I need to switch on and get it right....I have recently become aware of the separate Lee factory Crimp die ... I might add that the 4570 head spaces on the rim. Should I seat my projectiles and then use the factory crimp die as two separate operations? Another question.... In 243 and a few other calls I have for a long time preferred boat tails mainly for the easy bullet seating factor. I’ll bet my dog I’ll be waiting a long time before anyone starts producing boat tails in 458...... so when seating projectiles in 4570 , do we have to flare the case a bit , or do we just be real careful seating ?......if no case flareing die comes in my set, I have a lathe, I can make a nice flareing tool


I started out trying to seat and crimp in one and found it painful. Now I set up my seating dies avoiding crimp, and crimp separately using the FCD, so much easier and the results are more consistent.

I can't recall ever having problems seating flat-base bullets in any caliber, just chamfer the case mouth after trimming. I haven't had to flare any bottle-necked cartridges for jacketed or plated bullets, but I always flare for cast or painted ones. The pistol caliber die sets generally come with flaring dies so I use them regardless of bullet type just for consistency.
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Re: Projectile seating and crimping

Post by Blr243 » 29 Jul 2020, 10:19 pm

Thanks for th replies...I had a quick chat to th lgs when I picked up my dies and components today ....there’s a flareing die for the case mouths in my three die set and after seating ,a quick Read of the factory crimp die instructions had me doin very nice crimps in no time ... it’s amazeing how easy it is just by reading the instructions
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Re: Projectile seating and crimping

Post by Grandadbushy » 29 Jul 2020, 10:51 pm

G'day Blr mate crimping is like ''How long is a piece of string'' i to have dies with the all in one move but found that the crimp die was easier for me my old 22/250 liked crimped ammo ,just a slight crimp though, my 7mm likes a crimp as well but my new 22-250 doesn't require crimping so i think it's up to the person and their rifles . I think the rule of thumb is rifles with a fair amount of recoil probably would need crimped ammo, then some say that projectiles with no canular don't need crimping but i gave my non canular 22-250 projectiles an ever so lightly crimp so as not to dent the projectile basically just tightening the neck a tad, I just find setting up a die for doing it all in one foul sweep is to much mucking around, but that's just me
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Re: Projectile seating and crimping

Post by SCJ429 » 30 Jul 2020, 8:03 am

Are you sure the 45/70 needs a crimp? There is a large surface area holding .458 bullets and you can use a fair amount of neck tension which will hold the bullet secured. I load for a 45/70 and some other fairly large recoiling calibers such as a 460 Weatherby Magnum and the 416 Rigby and have not had the bullet move in the magazine. I don't have any lever actions but the recoil does push the rounds into the front of the magazine when firing in a bolt action.
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Re: Projectile seating and crimping

Post by in2anity » 30 Jul 2020, 8:43 am

DISCLAIMER: don't follow arbitrary advice on a forum. :D

Ok with that out of the way, FWIW I don't crimp my 30/30 loads anymore; with my specific load. They don't get set-back. But I'm loading for accuracy.That's 21gr AR2207 under a 150gr pill @ 2000fps. I have tonnes of different FLS dies for the 30/30, and I just settled on the one that yields the most tension, which coincidentally is a hornady die.

I agree with SCJ - I'd be aiming to take the crimp out, if possible, mainly for brass life. But only if you're shooting reduced loads - full-power 45/70 loads are gonna boot. You could experiment with shooting, then measuring the OAL of the incoming rounds in the mag. I do that with all my levers to decide whether or not to crimp - but I only neglect the crimp for reduced recoil, target loads.

Just my 2c. Others will angrily disagree, at which point I will refer you to my disclaimer at the top. :drinks:
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Re: Projectile seating and crimping

Post by Blr243 » 30 Jul 2020, 3:42 pm

Noted. Good info. I play safe, learn adjust measure modify and measure
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