Has anyone tested how varying these two methods effect accuracy? I am wondering if it would be worthwhile to buy a collet type crimp die for rounds I fire in a semi auto 7.63x51. I have tried crimping my Grendel ammo, and found that I have to reduce powder charge to offset the extra pressure caused by the crimp.
The amount of crimp is dependent on a number of factors, so I think it is less precise than I like. I haven't found any significant shift in my bullets from cycling through the action, so going either way may not be necessary.
If what Lee says about crimp offered the slightest increase in accuracy everyone in the precision community would use it...Nobody does.
The collet die is fine, but it is not a crimp die.
A crimp does not increase pressure in a significant way.
I shoot dangerous game bolt action rifles and don't ever crimp...Not even with my 416 Rigby and 400 grain bullets.
If you're experiencing a significant increase in pressure from crimping, you're likely overdoing it. I'll sometimes crimp if it enhances accuracy, but not with the mindset of firmly holding the bullet in place.
I usually take a Lee FCD in a hand press to the range. If a load doesn't perform to my expectations, I'll try a light crimp.
As an example, I stopped after 3 shots @ 100 with this uncrimped Grendel load in new brass:
With the exact same load, I crimped the next 5 shots and this was the result:
Similar load in 1x-fired brass did fine without bothering to crimp. This is 10 shots:
I can't predict when crimping will and won't work, but it's not difficult nor expensive to test it with any given load.
I suggest a crimp so light that you question whether it's doing anything at all. Let the group sizes guide you.
Last edited by Drifter™; 04-05-2013 at 01:15 PM.
The only crimp die I have used is the lee die that functions when the cartridge pushes upward, and a sort of collet pinches on a small crimp. the point about precision shooters is very good, and I don't crimp any of my precision rifles. I will try some Grendel ammo with a very light crimp.