Armory Sponsor
Posted: 5/24/2011 12:58:03 PM EDT
|
I've been researching ways to reduce runout lately. It seems that the consensus is that a large part of runout is caused when the expander ball is withdrawn from the case, assuming that you are using reasonably decent dies.
My question is this, what would it hurt to deprime with a universal deprimer and resize without the expander/deprimer in the die if you are using boattail bullets? Thanks. |
|
You would have to use a bushing die. A regular full length sizer die with the expander ball removed would have your case mouth closed down way to much. I think this was what you were refering to.
The main issue I have with the bushing dies is that your neck thickness had better be consistant or your neck tension wont be either. |
|
I doubt much runout is caused be the expander ball being pulled through the neck. It's the result of manufacturing processes for the most part and possibly the exact composition of the brass used when making the case.
Cases that exhibit a fat side at the neck will usually run the entire length inside the case. |
|
Try this:
Use a universal de-capper. Install your FL sizer die, run a case and leave it in the up position. Adjust your expander ball all the way up until it touches the case. Now back it down a half a turn and let it float. Your case neck will be in contact with the die and expander ball when you withdraw the case. This will help your run-out. Try just sizing a case with out the exp-ball and check run-out. The problem is with the expander/de-capper rod. The RCBS competition sizer has a higher exp-ball, just not high enough. |
|
Agree that you will probably over work the neck with a standard FL die which is intended to be used with an expander.
You can always check you die to see what the ID at the neck measures, but it will probably be too tight. A bushing die or a collet die will do a better job. Most of that runout issue is a characteristic of the brass which runs the length of the case as stated above. The expander ball would have to be very gross and the case would have to be over constrained to be caused by the expander ball being drawn through. Even turning the necks does not address the runout in the rest of the case body. I have run all types of brass in all types of fashions then checked the results with a NECO gage and see that the issue is caused by the brass thickness runout more so than the expander ball. You will need to try expander balls of carbide and steel, at different diameters over the long haul. Sometimes, I use a collet die to avoid all of the above. The condition of the inside of the neck determines which one I choose. Bolt and single feed rigs are one thing, autos are another. Sometimes you have to shoot fairly far to have the effect become significant. A good seater will make a bigger difference. |
|
Quoted:
I've been researching ways to reduce runout lately. It seems that the consensus is that a large part of runout is caused when the expander ball is withdrawn from the case, assuming that you are using reasonably decent dies. My question is this, what would it hurt to deprime with a universal deprimer and resize without the expander/deprimer in the die if you are using boattail bullets? Thanks. According to M.L. McPherson, who wrote the instruction manual for the NECO concentricity gage and who is a published author on reloading and precision shooting (Google his name), runout is mainly caused by brass being fired in a chamber. Since brass is imperfect and varies in thickness across the case body, the subsequent cycles of sizing and firing cause the brass walls to expand and contract at different rates, due to said thickness variations. Thicker brass will expand differently (and hence contract differently) than thinner brass. Cases come out looking like an exagerated banana and this creates runout. Other factors come into play, no doubt, but there's not a lot you can do to cull the cases out before this happens. You can further mitigate runout by removing expander balls, making sure you have an inline seating die, spinning cases as you seat and finally...making sure your press is nuts on and your dies are concentric. Personally, I use a Bersin Concentricity gage for 7 RemMag and I'll be getting the bodies for 223 and 308 shortly. This gage uses a side bolt, kind of like the Hornady 'fixer' to nudge the bullet back over to the other side, based on a measurement from a .0004" dial gage, which shows the ecentric orientation of the bullet already seated. I've used this gage to measure runout after I've loaded rounds using my Redding dies sans expander ball and they're actually pretty good in conjunction with my Dillon 550b. In the even that some are found to be out of round, I just nudge them back 180* and I'm golden. And no, neck tension isn't compromised, as we're only talking about a few thous worth of movement, in the worst case. Chris |
Armory Sponsor