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Posted: 6/30/2013 4:43:16 PM EDT
| I have a set of RCBS full length dies in 300 BA. After setting the sizer 1/4 turn lower than contact with the shell holder in the Rock Chucker, the case measures 1.110" from the head to the base of the neck/front of the shoulder. My Hornady manual says that measurement should be 1.102". Needless to say, these loads won't chamber well enough to fire in my MP15. Anyone else had this problem? I've sent RCBS an email, but haven't heard back from them yet. |
| You can try getting a thinner shellholder if you can find one. For example a Lee shell holder may allow the die to be pushed downward a few thousands more than an RCBS because the top is thinner. I've seen differences between the different brands but now just use a set of Lee shellholders no matter what brand die I use. |
The Lee shell holder is doable, though.
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First, not sure what cartridge? Did you mean 300 bk (blackout)? Die setting instructions are just a starting point. You adjust them to fit your chamber. All tooling has tolerances and you adjust to your own equipment/tooling. Measuring a case with calipers is not the correct method. You need either a case gauge or a headspace gauge. You will need to adjust your die down a little more and check the setting with a case gauge or a headspace gauge. Keep adjusting in small amounts until you get the sizing die adjusted correctly. Cutting the end of the die off is not the answer.
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| Also, check your shellholder. It should be .125" from the top to the shelf the case head sits on. I checked a couple rounds loaded with my Hornady sizer die and by taking the fixed blade of the caliper and putting the point of the blade on the neck and gently sliding it towards the shoulder until it stops then sliding my calipers closed until the other blade stops against the case head it does give me close to the 1.102" dimension plus or minus a couple thousands. However, since you have tried the die in the Co-Ax also, I wouldn't think it's the shellholder. Trying to measure where the neck stops and shoulder starts isn't a very good way to check headspace. I highly recommend getting Hornady's Headspace gauge set to use with your calipers. Much better way to adjust your sizing die. Make sure your expander ball isn't hitting the bottom of the inside of the case. Try taking the expander ball and spindle out of your die and sizing a case without the expander and see if the measurement is the same. Could be the expander ball isn't letting the die bottom out on the shellholder? |
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Quoted: Is a case gauge or headspace gauge something peculiar to loading for semi-autos? Yes I've been hand loading rifle cartridges for ~36 years...everything from 17 Rem up to 470 NE...but not for semi-autos. That part is new to me. That's why I mentioned them. You need to screw die down lower and cam over your press. Go down 1/16 of a turn at a time. Normal for the shellholder to touch the bottom of the die. Without any gauges you will have to size a case, try case in chamber. Move die down, resize case, try to chamber. Repeat as needed. This process is called "setting up your sizing die". It's easier with a gauge, but can be done with your chamber.
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