Jumped In With Both Feet!

A year ago I got permission to collect boolits from the dirt bank at the gun club I belong to.
I read reams of information from a ton of sites along with YouTube videos.
So I sifted dirt and finally collected four 5 gal. buckets of spent ammo. Also collected and cleaned , prepped about a thousand 9mm range brass.
Bought a 150,000 bTU propane burner, large cast iron pot and the muffin pans etc.

Then bought a twenty pound Lee pot, 9mm 124 gr. RN six cavity mold and a truncated cone 120 gr. six cavity mold as well.
Got into powder coating, buying everything for that- Smoke's triple sample pack, new toaster oven, etc.

Now I've bought a used RCBS single stage press with accessories- dies, Uniflow gunpowder dispenser, etc.

I'm finally at the final stage of starting to charge the brass and seating the powder coated boolits.

Man, it feels GOOD!

But I now have a situation.
I'm targeting 1.150 for the OAL. (A friend teaching me reloading came up with this OAL and powder charge.)
Although I'm getting a few of those 1.150, the rest are ranging from 1.139 up to 1.160 in length.

Is this due to variation in the powdercoat thickness on the boolits?
Most of them were coated with my new Harbor Freight vibratory tumbler.

So my obvious questions are how to reduce the broad range of the OAL?
And what amount of OAL range is OK?

Especially the shorter side since that will increase internal case pressure to some degree.
I'm charging at the middle of the manual's range for Winchester 231: 3.5 grains or 226.8 mg.

The new Lyman manual's case charging range for my Lee boolits [TL356-124-2R] I think is: 3.0 - 4.1

Is the top punch in your seating die made for the type bullet you are seating and is there any old lube or other foreign matter stuck in the recess?

My first thought would be to make sure you are setting up the die correctly. Follow mfg directions.

Second would be lube stuck in seating stem, but, it seems you PC.

Yes, PC will change the OAL a little bit and may account for the variance. Especially if you aren't knocking off the excess powder before baking.

After checking the suggestions listed above, there may be one more possibility. The seating die setting works off the head of the case. If any of your primers are sticking even slightly above the head the OAL you measure will be longer than the measurement from the head itself. I wasted a bunch of money on expensive seater dies to learn this lesson. Now I use Lee seater dies with the correct seater plug to match the boolit nose and everything works great.

I finished forty-eight boolits at my friends house on his press that he set up. He's been reloading for more than forty years, I'm sure its set up right. I'll check for foreign material in it.

Meantime, I bought new the four die set from Lee. My seating die is as yet unused since I'm just getting my press set up.
I'll give it a good acetone cleaning and see what results I get with it. Its made for round nose, as is my friends.

Maybe the variability is with the thickness of the powder coating. I've had a problem with it producing a full coat so I didn't knock much off. I just wore nitrile gloves and picked them out one by one and stood them on the baking tray in rows.

Thanks, I'll also check the primer depth.

I wasn't expecting a problem until I try to use my round nose die to seat the truncated cone boolits I've made.
I've read some guys have a problem with the round nose stem using it on truncated cone boolits.

I do not see how powder coat affects COL. Say one bullet has a PC thickness of .002 and the next has a thickness of .004. The bullet with the .004 coat will be seated a bit deeper into the case but the COL will still be the same. Certainly, will not affect COL by .021".

Yeah, that makes sense Don, now that you mention it.
Thanks for your thoughts.

From my limited experience with pistol calibers (much, much more with rifles) i would bet that the problem is with the last tenth of an inch in seating and crimping the bullet. i have never quite understood how to properly set it up to seat to and exact number for OAL and crimp at the same time. I usually ruin one or two till i get what I am looking for then lock the die and load eveything i have, before moving the die.

I say as long as they pass the plunk test and not at max load. Shoot them.
Order a seating stem from Lee and modify with epoxy will help if OCD is eating at you.

You have a +/- 10 thou OAL variation, PC normally gives +3. First, you load seems a little light for 231 so no pressure rise problem. TC nose needs a flat seater stem or at min one that is flat for your nose. I don't remember if I turned the RCBS 'punch' around or it came with a flat seater. Flare your case mouth (and expand the case properly for cast bullets - the RCBS expander is NOT right for cast!) so the bullets seat straight - crooked will give you big OAL variation. The tumbler method of coating may add excessive thickness to PC. You set YOUR COAL by a plunk test in YOUR barrel! Check EVERY loaded rnd as some may not fit. Too long (or thicker PC) will jam your gun and you have to pogo to clear it. Not fun! Especially check for shaved lead on loading - that will screw you up. Those 9mm cases are tough brass. Plunk test - pull your barrel, DROP in a rnd and the case head should NOT be farther out than the barrel hood. Proper ones may need to be pulled out, that's OK. They must DROP in.

LOL Pablo! No OCD here
Thanks for your thoughts popper. You shared a lot of very worthwhile information.
Thankfully all of my 9mm dies are Lee. I'm going to try my seating die as is, before filing one down like Fortunecookie45 demonstrated in his Youtube channel.
My load is a little light for 9mm?
OK by me starting out. I'm leaving room for Murphy to show up, being new at this.
Its hard to stay two steps ahead of him!
Once I wrap my understanding around this step, I may bump up a little the powder charge.

I forgot to ask, of the forty-eight rounds I have, how low of an OAL can I safely use? They range down to 1.140 OAL.
*Is there a rule of thumb?
I measured on my jeweler's scale every powder drop and know them to all be 3.5-3.6 grains.

For the upper range of OAL rounds, I'm going to plunk test all of them and reseat any that don't plunk.

Most good loading manuals will give you a minimum and maximum OAL for both the case and the loaded round.

But.....the seating stems typically contact the ogive of the bullet, not the meplat of the bullet. A 0.002-0.003" increase in the ogive diameter will give a much larger disparity is seating depth that just the 0.002-0.003". There is likely the difference in your overall lengths.

Most seating stems hit close to the nose of the bullet, not the ogive portion that is where the lands of the rifling meet the bullet. It still means that consistent thickness of the PC is needed if you want to control seat depth to 0.001" or so. And a thick spot of powder up on the nose where the stem meets can result in quite a change in seat depth. Of course, that same variation can cause a difference with the bullet engagement of the rifling.