Thread: Roll crimping 308 subs

Hey guys,

I finally got all my parts to try out some subs in the 308. Done all my research and pretty sure I have it sorted except the roll crimping bit so am I on the right track here?

I have a RCBS seating die that by all research and looking down the hole is capable of roll crimping. If I load and seat my projectiles as per normal then remove the seating stem I can then run it back through the seating die to achieve a roll crimp?

Projectiles are the 151gr casts and will seat down to the groove.

Understand I will need to have a play first to determine the correct height and there for amount of crimp and all brass will need to trimmed to correct length.

Any guidance or input much appreciated.

Greetings @Bobba,
I am a little confused on the need to crimp your cast sub loads in your .308. Crimping is usually needed to stop the projectile from moving in the case due to recoil or pressure from the spring in a tube mag. Neither of these is likely to be a problem in your sub loads. In some pistol loads the crimp is needed to get a decent powder burn but as before not applicable here. Best results from crimping are often gained by crimping as a seperate step as you suggest. Test both ways before going to crimping.
Expect the primers from your fired sub loads to be backed out of the case a little. This is the result of the low pressure of your loads and nothing to worry about. Starting with cases previously fired in your rifle and neck sizing only will help with this. I would be interested to know your powder load.
Regards Grandpamac.

Hi @grandpamac.

Thanks for your input. From all the research I have done( mainly this forum) the cast 151gr projectiles can be quite a loose fit in the neck and prone to moving. The crimp will fix this along with providing more consistent pressure and therefore accuracy.

Below thread along with a few others has plenty of detail.

https://www.nzhuntingandshooting.co....d-308-a-60565/

I found a wild increase in accuraccy just by crimping mine

I dont know what a roll crimp is tho, I just used the one in the lee die set box and followed the instructions included

at 30m my group went from 12" or more down to about an inch

this was 300blk and robs 151s, I mostly used 165gr nosler BTs in the 308

I also noticed it makes for less occasional one that pops above the sound barrier,

These factory crimp dies from LEE are the answer.I used Unique and now trailboss in 45/70 and 303 and found better accuracy with a crimp.
The 357, 45 colt and even 7.5x55 Swiss dies all came standard with a factory crimp die and if not standard I will buy one separately for cast bullets reloads.

Originally Posted by Bobba

Hey guys,

I finally got all my parts to try out some subs in the 308. Done all my research and pretty sure I have it sorted except the roll crimping bit so am I on the right track here?

I have a RCBS seating die that by all research and looking down the hole is capable of roll crimping. If I load and seat my projectiles as per normal then remove the seating stem I can then run it back through the seating die to achieve a roll crimp?

Projectiles are the 151gr casts and will seat down to the groove.

Understand I will need to have a play first to determine the correct height and there for amount of crimp and all brass will need to trimmed to correct length.

Any guidance or input much appreciated.

You just need to use a light crimp slightly more than taking the flare out a roll crimp is not nessecary it will damage the projectiles internal structure if not done correctly
there is no way they can be loose in the neck they sized sized to .310" the .308 expander button is .304" to .305" depending on brand of Dies if you are serious about shooting cast bullets
order a Lyman Short .30 cal M die best tool for expanding the case neck and flaring the cast mouth.

I use Lyman dies that do a roll crimp. It is different from the Lee factory crimp.

For seating the bullets, you put a case in the press, wind down the die until you feel it touch the case mouth, then back off a little.
Then seat all your bullets to the cannelure.
Then wind down the die a bit and back off the seating stem (I occasionally forget this bit!), then run all the rounds through the die again to crimp.

Originally Posted by shooternz

You just need to use a light crimp slightly more than taking the flare out a roll crimp is not nessecary it will damage the projectiles internal structure if not done correctly
there is no way they can be loose in the neck they sized sized to .310" the .308 expander button is .304" to .305" depending on brand of Dies if you are serious about shooting cast bullets
order a Lyman Short .30 cal M die best tool for expanding the case neck and flaring the cast mouth.

Thanks for putting me straight on the size, must have red it about something. Just getting into casts so will see how I go before getting any new gear.

Originally Posted by Cigar

I use Lyman dies that do a roll crimp. It is different from the Lee factory crimp.

For seating the bullets, you put a case in the press, wind down the die until you feel it touch the case mouth, then back off a little.
Then seat all your bullets to the cannelure.
Then wind down the die a bit and back off the seating stem (I occasionally forget this bit!), then run all the rounds through the die again to crimp.

Yep this is my plan. Will have a play and see what happens.

Originally Posted by Bobba

Thanks for putting me straight on the size, must have red it about something. Just getting into casts so will see how I go before getting any new gear.

I can source Lyman reloading tools when in stock, It is the best for cast bullet reloading Lyman made their name
back in the Black powder era; their current dies are the best quality they have made to date the only problem is
get shipments from the US, the shipping industry is in chaos

I'd be more concerned about your case capacity, a 151gr cast is pretty short. I run 190-225gr in my blackout and with such a large case capacity I wouldn't be keen to run a 151 in the blackout let alone a 308. remember if the primer can burn over the top of the powder when laying flat/chambered it can give you a very big boom that the suppressor wont help...

Anyway I run the 225gr eldm as a compressed subsonic load so I'm probably just as bad...

Originally Posted by PeakViewRange

I'd be more concerned about your case capacity, a 151gr cast is pretty short. I run 190-225gr in my blackout and with such a large case capacity I wouldn't be keen to run a 151 in the blackout let alone a 308. remember if the primer can burn over the top of the powder when laying flat/chambered it can give you a very big boom that the suppressor wont help...

Anyway I run the 225gr eldm as a compressed subsonic load so I'm probably just as bad...

ummmm Dude,there are literally hundreds of folks using these awesome 151s with great results....your 225 has way less case capacity than the 151s...the 151s are not too small to use and they work great in the 30/30 and the .308....... heck there are many folks who use "the load" eg 10grns of unique in just about and .30 calibre with just about any cast .30 projectile.......sometime folks over think what isnt really that hard......

Originally Posted by Tedz50

Attachment 203428

These factory crimp dies from LEE are the answer.I used Unique and now trailboss in 45/70 and 303 and found better accuracy with a crimp.
The 357, 45 colt and even 7.5x55 Swiss dies all came standard with a factory crimp die and if not standard I will buy one separately for cast bullets reloads.

I got Redding dies for 44mag and also the LCD which I gotta say is impressive. The Lee hand case trimmer mandrel needed a lot of work with W&D to fit in the case mouth. Poor machining. Yet the LUD for depriming is outstanding.

Originally Posted by PeakViewRange

I'd be more concerned about your case capacity, a 151gr cast is pretty short. I run 190-225gr in my blackout and with such a large case capacity I wouldn't be keen to run a 151 in the blackout let alone a 308. remember if the primer can burn over the top of the powder when laying flat/chambered it can give you a very big boom that the suppressor wont help...

Anyway I run the 225gr eldm as a compressed subsonic load so I'm probably just as bad...

8gr of trailboss fills up the case enough that it isnt a problem
other options include a bit of packer on top of the powder charge to keep it in place

trail boss is easier tho

My (limited) understanding of the roll crimp thing, is neck length, case length and also neck concentricity and wall thickness all play a bit in how consistent the crimps are. In other words, crap cases and crap case prep = crap results. Neck length all being equal affects the result with the roll crimp being shoved further in on longer cases, and if you have long and short cases (eg different rifles supplying cases with the dies set to the longest one), you can actually shove the neck of the case back into the shoulder.

The collet type crimp die seems to be by reputation more tolerant of these sort of issues e.g. more consistent in operation with variability. I have a nutjob mate (he's actually a top bloke but a bit full on) that found somewhere on the internet about swapping the bushing out of a bushing die for one a couple of sizes down or so and then using that to crimp by just tapping the neck, he seems to believe it's miles ahead of any other option. To be fair, that and the Lee collet crimper are where my experience of crimping stop and honestly after the lee crimp die I kinda swore off crimping and just avoided loading for tube mags. Never shot that much centrefire semi and never found I needed to crimp when I did.