Good afternoon. I am semi new to reloading and am experiencing inconsistent bullet seating depth and looking for answers about the cause and searching for a solution. May not matter, but anything less than perfect is driving me nuts.
I’m reloading for 7PRC using a Forster (custom polished) bullet seating die. 175 ELD-x, Gunwerks/ADG brass, 67.1 gr H1000 (not a compressed load). Not using an expander mandrel when sizing.
When measuring base of the case to the ogive of the bullet I’m experiencing variation of 2-10 thousandths. It seems to me that the die should seat the bullet the exact same EVERY time but this is not happening. Can someone explain what is happening and help me correct my mistake(s).
Well 2 thou is within the error of measurement of even the best calipers.
10 thou is a bit much, although I’ve measured factory match ammo and found variation up to 7 thou.
Same die, cartridge and powder load, but Peterson brass and LRX bullets gave me grief, until i started seating longer. Even though that shouldn’t have been compressed, it sure acted that way.
Came across this not too long ago and I’d think this is generally the most likely culprit: it happens in the resizing rather than in seating.
The gist is that if the base to shoulder measurements aren’t exactly the same after resizing (which for me there tends to be 1-3 thou difference especially if I mix cases) that difference will be reflected in final CBTO (assuming you keep the seating die at the same setting).
I dont know what type of press you are using, but making sure dust, debris, old primer parts, etc. are not interfering with the ability of the press to cam over completely can be a culprit. I know things get in the way sometimes on my presses if I dont keep them clean. 5 thousandths isnt much so a little item can stop the full motion of the seating stroke.
If you are using a bushing to resize your brass, if the tension is too light after sizing, a bullet can move, or not be secure enough in the neck.
Check your bullet comparetor also, make sure something isnt inside it, you never know.
Good luck
The video by Erik C. is good, so it could be in the bump, but like it was stated earlier, 10 thousandths is a lot of variation. Is your sizing die custom made to represent your chamber and reduce oversizing?
Sizing die is a Forster full length die. Measurements after sizing are good. I’m really wondering if it has to do with neck tension. The brass is once fired but not annealed…but it seems like if the press cams over all the way that the length of the seated bullet should be the same every time. Am I wrong on this?
Also, most are within .005 variation with an occasional one higher. Loaded 50 last night
10 thou is a bit high but there will always be some variation. I’d say if you’re keeping them all within 5 thou you’re doing it right.
I usually check the first 3-4 shots and then I’ll load 10 and just check every 10th round to make sure I don’t need to make a tiny adjustment to the die.
A few comments about shoulder bump. I’d consider that irrelevant to seating depth measured base to ogive.
Yeah, I guess in the final analysis, the question is how do they shoot for you? If 5-10 thousandths is giving you good groups…then that is what that weapon likes. If the brass is resized, all are trimmed to the same length, then the COAL or base to OG should be consistent. Only other thing I can think is the consistency of the tips. BTHP meplat can have variation in length due to the way the tip is shaped; ballistic tips give a better finished point to measure with calipers, but if they shoot, they shoot.
Good luck
Some bullet types are not sensitive to seating depth at all. Thus A variation of 5 to 10 thou isn’t going to make a difference. Some even claim that all bullets are not sensitive to seeing depth.
This is a long shot, but make sure your seating die isn’t crimping your rounds while you are trying to find the correct seating height. Some redding dies crimp AND seat. I learned the hard way that if you wanted to not use the crimp you had to thread the die a full turn out from where it hits the shell holder. I could see that being a reason why you have gotten a few that are not sized correctly. If this was the case it would crush the shoulder while you are seating.
While I still would like perfection, the loads have performed flawlessly during this hunting season. It is very satisfying to take an animal with a cartridge you loaded yourself!
I still consider my self learning but what I have come to realize is that really clean brass is more difficult to seat bullets. Neck tension is mostly the cause of inconsistent seating depth but also if you are near 100% case capacity the bullet will encounter more resistance seating into the powder. Don’t slowly seat the bullet with the press, once the bullet has started into the brass, confidently run the press arm to quickly seat the bullet with force gives me more consistent results. Hope that helps.
I think I have this figured out finally. I believe that inconsistent neck tension was causing the inconsistent seating depth. I have started using an expander mandrel which has resulted in much more consistent seating (within .002 of my goal). Kind of satisfying to figure out these little things as frustrating as they may be along the way. Definitely what Cmarcum is describing.