After you minimize the case mouth flare (to maximize the bullet retention provided by friction between the cartridge case and the bullet) and increase the crimp you can test the adequacy by doing this:
Load 9 rounds. Mark one with a felt-tip marker. Measure its overall length.
Load five
Fire one (unmarked) round.
Measure the marked round
Fire another (unmarked) round
Measure the marked round
Repeat until all 8 unmarked rounds have been fired.
Examine the measurements on the marked round.
If measurements 1 and 8 are the same, your bullet retention is adequate.
If measurements 1 and 8 are not the same, you could improve things a bit.
If 1 and 2 are not the same, but 2, 3, 4, 5, 6, 7 and 8 are the same your roll crimp is probably in the wrong place. The bullet is moving to where the roll crimp stops further movement and you are probably OK, but could do better. Make sure the roll crimp goes into the crimp groove and the lead meets the brass (inside the case mouth - hard to see, of course, but clean the lube off a bullet, seat and crimp and use a magnifying glass). Also, your friction retention is contributing little and could be improved substantially. If your bullets are properly sized, usually this involves moving to a thicker-walled brass or polishing down your case-mouth expander a little.
If 1, 2 and 3 are showing increases but 3, 4, 5, 6, 7 and 8 are the same, then the same situation holds as above, but your friction retention is working somewhat. Just not enough. The cure is the same as above.
And so forth
If 1, 2 and 3 are the same but later measurements show lengthening, then start another thread, please. There will be a lot more questions.
If there is ever shortening between measurements 1 to 2, 2 to 3 and so forth, you have me stumped.
Note: It is better to depend on friction as much as possible for bullet tension. Roll crimping works the brass and makes it brittle, leading to cracking of the case mouths unless you anneal the brass periodically, which is barely worth it with handgun brass.
Aside: Your original assumption, that starting out with shorter brass would mitigate the problem, while dimensionally correct, does not address the underlying problem. It gives you an extra 1/8", true. But it does nothing for the crimp jumping.
Thanks for asking our advice.
Lost Sheep