Tolerances


PDA






Comrade Mike
April 17, 2013, 01:18 AM
What kinds of tolerances do you guys hold to in trimming and in bullet seating.

Trimming I try and keep it to +/- .003, generally don't have any problems doing that.

When seating a bullet (rifles especially), ill dial my dies in with a round slowly pushing the bullet in until I get the length I want. Then, not touching the dies, I can seat 5 more and see variances as large as .01 in COAL from tip to base. Does this variance effect anything? Should I worry about it or is it just irregularities in the bullet? How much is too much?

If you enjoyed reading about "Tolerances" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
jr_roosa
April 17, 2013, 01:32 AM
variances as large as .01 in COAL from tip to base

Measure using a bullet comparator and almost all of your variance should go away. I get within a few thousandths for seating, and I'm not doing anything special.

-J.

troyheckman
April 17, 2013, 01:36 AM
When you measure from the tip of the bullet you have to remember that the bullet tips aren't perfect. The tip of the bullet can be deformed pretty easily so it will change your measured OAL. Also, the bullet seating die pushes on the bullet at the ogive (roughly) so you need to measure from the ogive to get accurate results. Look for some bullet comparators that attach to your calipers to allow you to measure from the ogive. That will give you an accurate reading on the OAL and you can work from there if you need to tighten up the tolerances. I was in the same boat as you when I first started, having variances up to .01 from the bullet point but when I measured to the ogive I was running +/- 0.001ish.

Another thing to remember is not to get too wrapped up with extremely low/tight tolerances. I'm just as addicted to tiny +/- as the next guy but at the end of the day if your getting the accuracy you want don't fret over minuscule details.

What method are you using to trim? I use the cheap lee trimmers and haven't paid alot of attention to my tolerances, I just make sure they are under max length. I'll leave that question to one of the resident experts.

*Looks like jr_roosa just beat me. Great minds must think alike.

rg1
April 17, 2013, 01:43 AM
My hand operated trimmers, a Lyman Universal and a Forster, will keep trimmed lengths to .003 or less depending on me and whether brass is all the same lot or brand. Bullet seating depths vary with the bullet tips themselves and how consistent they are. Measuring lead tipped spire points or hollow point bullets have the most oal variations but if you measure to the ogive of the bullet and not the tip then they measure very close to the same seating depths. I don't think .003" in case lengths will make much difference in accuracy with most shooters or guns.

gamestalker
April 17, 2013, 03:33 AM
As for trimming, the case length gauge does it all. Using most trimmers there is no reason to have any fluctuation of more than .001" or less.
When seating bullets, seating depth should be adjusted using the seating plug in the die. Set it to what you want, lock the die down, and every bullet will be seated to to the same depth off the olgive, not the tip. It kind of sounded like you are controlling seating depth by how far you are running the press ram, rather than using the die implement, (seating plug adjustment). And also, measuring off the tip is not what is important, beyond how the cartridge fits your magazine that is. Once you have magazine fit, then you can play around with your seating depth if necessary, based on accuracy.
GS

Walkalong
April 17, 2013, 08:35 AM
gamestalker has got it covered. I'll add that a difference in .003 on a trimmed brass will never show its self on target. There are far too many other variables that really make a difference for 99% of the applications out there. That said, +/- .001 is doable.

How much is too much? If you are using quality bullets seat them all using the seater as designed and forget about it.

Muddydogs
April 17, 2013, 09:21 AM
Assuming you are using your seating die correctly seating depth can very as much as .020 measured to the ogive depending on the bullet. If you are getting wild swings in seating depth measure your bullets from base to ogive and sort by this length. I find pulled bullets are the worst. Speer Grand Slams seam to have a large variation in there base to ogive measurment as well.

Comrade Mike
April 17, 2013, 11:41 AM
I'm using the RCBS trim pro 2 with the spring tensioned shell plate.

Sounds like I need to put the calipers down after I set my seating die

Arkansas Paul
April 17, 2013, 11:44 AM
I don't know if it matters in your instance, but keep in mind if you're loading a polymer tipped bullet, seating depth can read all over the place because of the tip getting deformed. They will rarely read consistently.

If you enjoyed reading about "Tolerances" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!