Tonight I spent a little time cleaning up some brass from last week's shooting with the .243. Since the last time I loaded some up, I bought a Wilson case gage on the high recommendations in this forum, and I was looking forward to optimizing my resizing die adjustment using this simple, but brilliant tool. After sizing and decapping the cases, I carefully wiped off the lubricant and dropped a random sample of cases into the gage.
For those not familiar with these gages, the bore is machined to a precise profile to match the case dimensions, especially the shoulder for bottle-necked rifle cases. On the Head end, two flats are machined, one low and the other high, which precisely match the SAAMI minimum and maximum headspace lengths. On the Neck end, the flats are machined to correspond with the minimum and maximum case length. The tolerance for the head is 0.005", and for the neck, it's 0.010". Ideally, the properly sized case should fall midway between the limits for each end.
After sizing using an RCBS Full Length Resizing die adjusted to contact the shell holder with no gap between them when the ram is fully raised, I tested a sample of the cases and found that every one of them extended very slightly above the maximum head space flat. I haven't tried measuring the excess, but as an eyeball estimate I'd be surprised if it was more than 0.003". I tried lowering the die a bit, to the point that the turret on my press deflects a little at the top of the ram's travel, and this did not change the results. I really didn't expect it to, but I tried it anyway, just because someone here would probably suggest it.
Flipping the gage over, I also measured the neck length using a metal straight edge across the upper flat and found that each of the sample cases had a neck length which fell between the upper and lower limits. That's a pleasant surprise!
So, my question/issue is, does the excessive height of the head of the finished cases require correction, or is it just the way my gun likes things, and perfectly safe? I guess that leads to a second question, in that the necks after resizing are still within specs, is there a good reason to trim them? I do use the Lee FCD for crimping, and that tool seems to eliminate a lot of problems with inconsistent neck lengths.
What are your thoughts?
For those not familiar with these gages, the bore is machined to a precise profile to match the case dimensions, especially the shoulder for bottle-necked rifle cases. On the Head end, two flats are machined, one low and the other high, which precisely match the SAAMI minimum and maximum headspace lengths. On the Neck end, the flats are machined to correspond with the minimum and maximum case length. The tolerance for the head is 0.005", and for the neck, it's 0.010". Ideally, the properly sized case should fall midway between the limits for each end.
After sizing using an RCBS Full Length Resizing die adjusted to contact the shell holder with no gap between them when the ram is fully raised, I tested a sample of the cases and found that every one of them extended very slightly above the maximum head space flat. I haven't tried measuring the excess, but as an eyeball estimate I'd be surprised if it was more than 0.003". I tried lowering the die a bit, to the point that the turret on my press deflects a little at the top of the ram's travel, and this did not change the results. I really didn't expect it to, but I tried it anyway, just because someone here would probably suggest it.
Flipping the gage over, I also measured the neck length using a metal straight edge across the upper flat and found that each of the sample cases had a neck length which fell between the upper and lower limits. That's a pleasant surprise!
So, my question/issue is, does the excessive height of the head of the finished cases require correction, or is it just the way my gun likes things, and perfectly safe? I guess that leads to a second question, in that the necks after resizing are still within specs, is there a good reason to trim them? I do use the Lee FCD for crimping, and that tool seems to eliminate a lot of problems with inconsistent neck lengths.
What are your thoughts?