bullet pull

is there anything wrong with a .001 bullet pull in an auto (45 auto, 9mm). if i got a expander plug @ .001 smaller than sized dia.; i understand that there
will be some brass shrinkage. and that should give more that .001 "pull"
the reason for the question is that i may be trying soft lead and was worrying about too much bullet pull might deform the bullet

What exactly do you mean by "bullet pull"?

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In .45 ACP and 9mm more important is bullet "push" in which neck tension is adequate to prevent bullets from telescoping deeper into the case during the feed cycle when the stripped round hits the feed ramp. Driving the bullet as little as 0.05" deeper in 9mm can dangerously spike pressure to the equivalent of a proof load. There are warnings about this in the Speer handbook.

Bullet "pull" is more important in revolver ammunition. where inertial dislodgement draws bullets forward, reducing load density, impairing ballistic uniformity, and possibly impairing cylinder rotation if the bullet creeps forward out of the cylinder.

Recommended practice is for the expander plug below the flared portion be 0.002" less than bullet diameter. Bullet push in automatic pistol ammunition is checked by holding a loaded round in a shell holder and then pushing against the bullet nose on a bathroom scale. In .45 ACP rounds should withstand 40 pounds pressure against the nose for 5 secs. without overall cartridge length shortening more than 0.005".
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In factory ammunition asphaltic varnish known in the trade as Black Lucas is applied inside the case mouth and allowed to harden before LAP (load, assble, pack.)

I suspect that he is referring to neck tension. If he uses various head stamps and a different number of firings, the neck tension will be all over the map. The tension needs to be sufficient to hold the bullet in place and not allow for "set back" when the cartridge is chambered.

Brass "Shrinkage"? Maybe the OP means spring back. Yes, there is some but that also depends upon case neck hardness.

I load lots of 9, 45, 357, and 41 with expanders 0.001" to 0.0005" under bullet diameter. Using a certain size expander actually gets you brass ID a little smaller than the OD of the expander anyway.

Try this sometimes...load a dummy jacketed bullet, rifle or pistol, then pull it. Now reseat it and tell me how much neck tension you actually had based on how easy it was to reseat the bullet.

IMO, Most of what you feel when you seat the bullet is the expansion of the case neck beyond the elastic limit.

Reloaders discuss 0.002", 003" or more of neck tension. Brass does not have 0.002", 0.003" or more elasticity. The brass permanently stretches and the case neck only has about 0.001" +/- elasticty or "grip" left on the bullet depending on hardness or annealed state of the case neck.

So yes, i see no problem with an expander 0.001" under bullet diameter as long as you cannot push the bullet into the case by pushing the cartridge against the workbench.

You should get a feel for how much pressure to seat a boolit properly.
If you have enough flare for it to sit on the case mouth and seat without visibly deforming or shaving it,
after its seated, while pushing down on it with your thumb and it won't go down into the case --- you're good.

I have loaded some 9mm rounds with test loads, and made up an expander die that gives an interference fit of 0.0005''. The cases were squeaky clean, and the bullets do not move in the necks.
The softer lead alloy retains the same bullet diameter.
I have also made up an expander that gives 0.0015'' and have yet to see if the bullet diameter has been reduced. I doubt it.

Brass temper also has to be considered if you are using random headstamp brass that has been previously fired.

Loading any rimmed case with cast bullets, the crimp takes care of controlling bullet movement.

Rimless cases like 9mm and .45ACP that headspace on the mouth are another matter.

I have tested bullet base swaging with a couple alloys and expander sizes. I have found that .002 will not swage bases even if cast from 50/50 WW/soft. I've not tried a softer alloy.

Decades ago, I remember reading where "bullet pull" was the term describing the force needed to move a bullet after being seated.

As noted in previous responses, neck tension helps prevent bullet movement into the case (called bullet setback) while in the magazine or while being chambered. Also as previously noted, an expander plug 0.002" under the bullet probably does not increase this neck tension much (if any) more than one 0.001" under the bullet.

Another important item to prevent setback is the depth of the expansion. If the depth of the expansion is just less than the actual seating depth, the bullet has to "expand" the brass to go any further in.

For many years I loaded .45acp without checking bullet tension. Everything went fine for thousands of rounds.

Then I got a new mold, flat nose, and had some rounds that I noticed were more recoil than normal. I ejected an unfired cartridge and found the bullet pushed back in the case.

I bought a taper crimp die and after that crimp every one. A 'push' test followed by a 'plunk' test were done when setting the die to make sure the bullet could not be pushed back into the case and that it would chamber in my pistol.

FWIW, I have always roll crimped revolver bullets. I tried them without once (.357mag) and had a bullet come forward and lock up the cylinder when it jammed against the frame.

Back in the early '80s when I shot I.P.S.C., I pitched every Remington .45 A.C.P. case I came across. Had the same problem as mentioned about the bullet getting pushed back in the case while chambering. Around that time I had purchased a few hundred new Remington .44 Magnum cases. As I was seating the bullet there was virtually zero tension felt. When I mean zero I mean zero in that I was able to pull the bullet from the case with my bare fingers before adding the crimp. This was after sizing the cases too. Traded the cases back for Federal brass and the problem went away.

Outpost has it correct. 9mm cases are harder (due to tapered case walls) than 45acp and can size down the cast bullet.

45 acp- After bullet seating, OD needs to be larger by .002" minimum .

The expander has little control over NT. Different brands of brass spring back at different rates. Bullet pull can be from 45 lbs to over 100 lbs, same expander.

My test-

9mm luger needs sized with a new RCBS die. It maintains the case taper. Expander is M type

I test buy pushing loaded round against my work bench and lean in a little if it moves time to find out why