Crimping consistency

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Kyte

Kyte

Well-Known Member
Hi folks, I’d like to start giving my reloaded hunting ammo a light crimp , mostly to make it abit more robust for field use, my questions are:
Is there a way I can guarantee repeatable crimp pressure from Lee crimping die as it is removed from the press each time after use ?

Also is this likely to alter pressure/ velocity much ? , should I back off and rework this load I use ?
(6.5 creedmoor , 41.2gr n555 , eld-x 143gr, hornady brass and magtech primers .

Any advice / experience gratefully appreciated
Cheers all
 
Kyte said:
Hi folks, I’d like to start giving my reloaded hunting ammo a light crimp , mostly to make it abit more robust for field use, my questions are:
Is there a way I can guarantee repeatable crimp pressure from Lee crimping die as it is removed from the press each time after use ?

Also is this likely to alter pressure/ velocity much ? , should I back off and rework this load I use ?
(6.5 creedmoor , 41.2gr n555 , eld-x 143gr, hornady brass and magtech primers .

Any advice / experience gratefully appreciated
Cheers all
Click to expand...
Don’t overthink it - the way a Lee die works is to close four collets around the case neck - once closed they are pretty much stopped.
From memory Dr Richard Lee deals with this in his excellent reloading magnum opus - something like “even a firm crimp will add only 1-200 psi to a round where perhaps 45-50,000 is the norm” - you will not be able to detect any differences as a result of your crimps.
All that said I certainly wouldn’t rush to crimp copper bullets - a light dipping of the FB toe into the world of copper did reveal increased pressure signs with a light crimp!
🦊🦊
 
Kyte said:
Hi folks, I’d like to start giving my reloaded hunting ammo a light crimp , mostly to make it abit more robust for field use, my questions are:
Is there a way I can guarantee repeatable crimp pressure from Lee crimping die as it is removed from the press each time after use ?

Also is this likely to alter pressure/ velocity much ? , should I back off and rework this load I use ?
(6.5 creedmoor , 41.2gr n555 , eld-x 143gr, hornady brass and magtech primers .

Any advice / experience gratefully appreciated
Cheers all
Click to expand...
The key to consistency with a Lee FCD is trim length. If the cases are all the same length, then the die will crimp with the same amount of pressure.
 
Foxyboy43 said:
Don’t overthink it - the way a Lee die works is to close four collets around the case neck - once closed they are pretty much stopped.
From memory Dr Richard Lee deals with this in his excellent reloading magnum opus - something like “even a firm crimp will add only 1-200 psi to a round where perhaps 45-50,000 is the norm” - you will not be able to detect any differences as a result of your crimps.
All that said I certainly wouldn’t rush to crimp copper bullets - a light dipping of the FB toe into the world of copper did reveal increased pressure signs with a light crimp!
🦊🦊
Click to expand...
Awesome info , that sets my mind at rest .. cheers👍🏻
 
I have always found a crimp adds to consistency of my ammo and improves the accuracy. My thinking is that as long as a crimp holds the bullet firmly then the pressure has to build up in the case before the bullet moves.

Without a crimp or consistent neck tension one bullet may start moving earlier than the next in the pressure build up.

The alternative is to seat the bullet close to the lands. This does work well, indeed I understand that some benchrest shooters load their bullets deliberately long with little tension in the case mouth. As the cartridge is loaded it is pushed in till it seats on the lands and then the cartridge moves forward till the bolt falls. This works very well until you try to remove an unfired cartridge - the bullet stays in the bore and powder goes everywhere.

Monolithic bullets prefer to have some run up to the lands.

Personally I full length resize, trim to length, reload, seat bullet to standard overall length, and crimp firmly.
 
I do things differently
Unless you neck turn your neck thickness is variable
Them your crimp die will hit the brass and impart a different crimp each time

Trim is also important but thats just determining how much of the neck is crimped
How wide
Vs
How deep

Set the die to allow manual adjustment
So that the arm hits the die tension just shy of the full stroke
By how much determines the amount of crimp

If you hit a thick neck the arm shows you as it will be further away from full travel
If a thin neck it will hit full or near full travel before resistance

I dont want a visible crimp
Just light
Its too easy to crimp right into the bullet shank

Unless huge recoil or slack brass this is too much IMO

Light crimp on variable brass thickness and quality does wonders for consistency
 
Fix all my die lock rings with a clear nail varnish, good enough to withstand being removed/refitted, but not enough to prevent another setting being made.
 
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