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SL1 · March 21, 2009, 09:18 AM

amathis,

Well, suddenly you have lots of advice, some of it a little premature and some of it that doesn't apply at all to your situation.

The thing that you needed to work on first is getting the proper die set-up.

Then, you need to understand that this particular die takes a lot of force to do its job properly. In your original post, you said "I am assuming it is correct since there is a little resistance." I think you will see in your instructions for this die that you need to put a lot of force on the press handle to properly form the case mouth on the mandrel. Exactly how much force you need to use really depends on your press design. Compound linkages take less muscle than single-linkage presses, for example. I can do mine on a single-linkage press (an RCBS Junior).

Anyway, once you get that right, you can start figuring-out if your mandrel is too large for the case neck tension you want. One thing that some of the other posters mixed up (with bushing-type neck sizing dies) is that the collet-type dies do not need different internal parts to accommodate cases with different wall thicknesses at the mouth. However, brass is a little springy, so it will spring back from the madrel surface by about 0.002" as you release the pressure on the press handle. (That is a good thing, or you would have a hard time getting the case mouth off the mandrel.) AFTER the brass has sprung back, you want it to still be about 0.001" to 0.002" SMALLER than the bullet diameter so that it will grip the bullet tightly. Brass gets harder and springier as it is worked, so the amount of spring-back will change from lot-to-lot of brass and , for the same lot of brass, with the number of times reloaded.

So, you may need a smaller mandrel to get as much tension as you want. I did in one of my collet dies. Unless you are good at machining things uniformly, I suggest that you simply buy another mandrel from Lee. If you try to reduce the mandrel you have by yourself, there is significant potential for you to get things uneven or too small. But, try loading with the one you have, first, using the proper die setup and appropriate level of force on the press handle.

It is hard to precisely enough measure the inside diameter of a case mouth with calipers so that you can use the measurement to determine what mandrel diameter you need. So, see how what you have works for your situation. If you are shooting single-shot, you don't need much bullet grip. If you are loading your rounds from a magazine, you need enough to keep the bullets from being pushed back in the case by either the recoil while they are in the magazine or by the force against the feed ramp when you feed them from the magazine. (Folks who shoot autoloaders need MAXIMUM bullet grip or even a crimp, since maximum bullet grip is limited by brass springiness.)

If there is not enough grip, then go to a smaller mandrel. Typically, a 0.001" or 0.002" reduction is all that you need.

I hope this gets you going in the right directionto solve your problem.

SL1

March 21, 2009, 09:18 AM	#14
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	amathis, Well, suddenly you have lots of advice, some of it a little premature and some of it that doesn't apply at all to your situation. The thing that you needed to work on first is getting the proper die set-up. Then, you need to understand that this particular die takes a lot of force to do its job properly. In your original post, you said "I am assuming it is correct since there is a little resistance." I think you will see in your instructions for this die that you need to put a lot of force on the press handle to properly form the case mouth on the mandrel. Exactly how much force you need to use really depends on your press design. Compound linkages take less muscle than single-linkage presses, for example. I can do mine on a single-linkage press (an RCBS Junior). Anyway, once you get that right, you can start figuring-out if your mandrel is too large for the case neck tension you want. One thing that some of the other posters mixed up (with bushing-type neck sizing dies) is that the collet-type dies do not need different internal parts to accommodate cases with different wall thicknesses at the mouth. However, brass is a little springy, so it will spring back from the madrel surface by about 0.002" as you release the pressure on the press handle. (That is a good thing, or you would have a hard time getting the case mouth off the mandrel.) AFTER the brass has sprung back, you want it to still be about 0.001" to 0.002" SMALLER than the bullet diameter so that it will grip the bullet tightly. Brass gets harder and springier as it is worked, so the amount of spring-back will change from lot-to-lot of brass and , for the same lot of brass, with the number of times reloaded. So, you may need a smaller mandrel to get as much tension as you want. I did in one of my collet dies. Unless you are good at machining things uniformly, I suggest that you simply buy another mandrel from Lee. If you try to reduce the mandrel you have by yourself, there is significant potential for you to get things uneven or too small. But, try loading with the one you have, first, using the proper die setup and appropriate level of force on the press handle. It is hard to precisely enough measure the inside diameter of a case mouth with calipers so that you can use the measurement to determine what mandrel diameter you need. So, see how what you have works for your situation. If you are shooting single-shot, you don't need much bullet grip. If you are loading your rounds from a magazine, you need enough to keep the bullets from being pushed back in the case by either the recoil while they are in the magazine or by the force against the feed ramp when you feed them from the magazine. (Folks who shoot autoloaders need MAXIMUM bullet grip or even a crimp, since maximum bullet grip is limited by brass springiness.) If there is not enough grip, then go to a smaller mandrel. Typically, a 0.001" or 0.002" reduction is all that you need. I hope this gets you going in the right directionto solve your problem. SL1