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Posted: 12/7/2014 3:54:31 AM EDT
| I have rcbs full base dies for my ar. i was wondering about increasing the neck tension when resizing. as of now after i size the case and measure the inside diameter of the case neck it is usually around .222 but sometimes is around .223. I was thinking maybe if I pull the expander ball out of the die and chuck it in a drill I could take some 600 grit sand paper or finer and polish the ball? If this would work could I get some more detail on how to do this? Thanks. |
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Just work carefully, but that will work.
It is extremely iffy getting an inside measurement with dial calipers inside a case neck. Unless the bullet moves when pushed HARD against your bench I wouldn't worry about it much. Sometimes the die is just screwed. I have a Lee 30-06 sized that no amount of button whittling would fix. Never figured it out so I just chucked it. |
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Quoted:
I have rcbs full base dies for my ar. i was wondering about increasing the neck tension when resizing. as of now after i size the case and measure the inside diameter of the case neck it is usually around .222 but sometimes is around .223. I was thinking maybe if I pull the expander ball out of the die and chuck it in a drill I could take some 600 grit sand paper or finer and polish the ball? If this would work could I get some more detail on how to do this? Thanks. Measuring the inside of a case can be difficult without the proper mic. An easy way to do it is, Measure the outside of a few sized cases, Seat your bullets and measure the OD again, Subtract for your "neck tension", "bullet grip" whatever one wishes to call it. Why do you wish to increase "neck tension"? Are you having issues with your bullets moving in and out? |
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A more accurate way to measure how much neck tension you have is to measure the resized case neck exterior prior to seating a bullet. Measure it again after the bullet has been seated. The difference is the actual neck tension in .001" increments. You must have a minimum of .002" but you don't want or need more than .003" difference.
Anything less than .002" will not hold a bullet securely when fed from a magazine. Anything over .003" is wasted and will induce run-out when seating a bullet and otherwise stress the brass. If given a choice go with .003", no more. Simply removing the expander ball and stem from your die, this will allow you to chuck it in a drill. Use your calipers (or better yet a micrometer .0001" accuracy) and spin polish the expander ball enough to get the desired amount of tension. 600 grit wet/dry works great. Go slow, metal removed can never be replaced. If you go too far expander balls are cheap to replace. |
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Quoted:
I have rcbs full base dies for my ar. i was wondering about increasing the neck tension when resizing. as of now after i size the case and measure the inside diameter of the case neck it is usually around .222 but sometimes is around .223. I was thinking maybe if I pull the expander ball out of the die and chuck it in a drill I could take some 600 grit sand paper or finer and polish the ball? If this would work could I get some more detail on how to do this? Thanks. Sir, I suspect the variation you're getting in case neck ID after sizing with the same die set may be due to variations in the case neck wall thickness and or inadequate lube inside the case neck. Try a bit of lube on the inside. My preference is Imperial sizing wax. You can reduce the OD of the expander ball by polishing what you have, and I agree you need between .002" and .003" less than bullet OD which I assume is .224" JMHO, 7zero1. |
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