Inconsistent Seating Depth

J*nvier said: I am loading some ammo, using an RCBS Rockchucker mounted to my desk, with RCBS dies. I am going for *edit* overall length * 2.350, and that's what the first couple cases I ran came out as. Then they started to vary from 2.355 to 2.346. I've loaded hundreds of rounds already without this problem. The die is firmly locked in place, with the set screw, and I'm doing nothing different. Any ideas?

gth said: 0.009 difference???? Doesnt seem like a lot. Are you measuring from the ogive or the tip of the bullet?

J*nvier said: Tip of the bullet. All my previous loadings have had consistent +/-0.0005" tolerance.

J*rlath said: Different brand of bullets which have less profile consistency? You may have used a single brand/mass/type (say Speer .308 150gr Grand Slams) for the last 1000 rounds and then bought new bullets which have less quality control?

R*german said: I measure from the ogive and I still get variations with trimmed brass. I agree with GTH , it's not that much. Are the bullet tips a different configuration from previous loads? Lead tips can deform more than polycarbonate tips. Do you use competition seating dies? Seating dies can get dirty. You could check them and clean with a q-tip if necessary.

J*nvier said: I am loading .224 bullets, have used Speer 52gr HPBT Match, Hornady 52gr HPBT Match, and Sierra 52gr HPBT Matchkings. I am loading the Sierras again. Just checked seater plug and inside die, they are clean.

m*ynard said: +/-.0005? You must have a CNC loading machine:p Even match bullets vary in length. Your seating depth to the ogive needs to be consistant, the OAL means nothing.

J*nvier said: I never thought about bullet length. I just measured a few, and they do vary. I guess that's probably the issue, though I don't know if it explains how I got such good tolerances before today. Anyway, thanks for the help everyone!

m*nitou210 said: For me the RCBS seater dies are not the quality of Redding competition seater die, and I have a lee for 222 that I use and find it better than RCBS. But like Maynard said OAL means Dick it the ogive thats important this past winter i did some testing on many bullets, for weight on digital scale, and ogive with Sinclair Gauge and OAL I took ten out of each box and checked all the only bulklet that had the same on everything was a old box or Remington Benchrest 52gr match bullets, I could not beleive it as all the other manufactures where different in weight ,OAL and Ogive from best to worst Remington #1 224cal Speer Lapua #2.309 al Berger #3, 224cal Sierra #4 224,.308 & 7mm Speer gold Match #5 168gr..308cal Hornady was just plain terriable in everything Amax's,V max and HPBT Speer Gold Match

r*berti11 said: What you need to measure is the ogive, not the tip. Use one of these... It is the ogive that engages the rifling, this is what you want to be consistent.

B*omer said: I don't think the difference is anything to worry about, but there are a couple of things you can do to limit what variation you get. First off, as has been stated, measure to the ogive of the bullet rather than the tip. There could easily be .009" variation in the actual bullet length from the same box. If you were getting .0005" variation in OAL, perhaps you should be giving us advice!! Keep your dies clean. A slight build up of mung on the contact surface of your seating stem could cause inconsistant results. When you seat your bullet, don't slam the press handle to the end of it's travel. Gently push the bullet in about half way, then turn the case a quarter turn and push it in the rest of the way, then turn the case another quarter turn and ensure that it is pushed all the way home. A compressed powder charge could cause the bullet to push back slightly resulting in some OAL variation. A rubber O ring under the lock ring of the seater stem will allow the seater stem to find it's own center. I got rid of the retaining spring that holds the shell holder in place and use an O ring for that also, allowing the shell holder to slide freely in the ram slot for the same reason. Lube your case necks with dry graphite, particularly if you resize with an expander ball. Inconsistent neck diameter due to poor expander ball use will cause variation in bullet seating depth. For easiest results resize the neck with a bushing die and resolve the problems that can be associated with an expander ball.

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