They will likely shoot just fine. It will depend on the head-space of the particular gun. A good tight gun may never notice. A lose gun on the edge of maximum head-space may not fire, if the firing-pin can't reach the primer. If the extractor claw will hold it...it should shoot if it's short.
If I only had a few, I'd fire them and see if they will stretch-out to 1.28+ on the next sizing, but I wouldn't make a habit of it.
Thanks americanboy. I think I am going to change my trim to length to 1.285 in the future. I have lots of .30 carbine brass, but I hate to be throwing it out when it ends up being too short after a couple of reloading cycles. My loads are lower power 4227 12.5 grain loads so I should be able to get more than a couple of cycles out of my brass.
Same thing happened to me early on when I was using an inferior trimmer. I did shoot some that were below 1.28 without incident. I NEVER take a trimmer setting for granted when I use it the next time. The instructions may say to do this or that and you'll wind up here. I pay no attention to that and run a test on the first few rounds when I do trim. I start at the top and work my way down in .001 steps until I arrive at a 1.285+- on the first case and I will measure one now-n-then as I trim to be sure everything stays-put. Anal....maybe, but carbine brass is relatively expensive and you need to be able to reload them multiple times to make reloading pay-off.
Thanks for the advice guys. I adjusted my Lyman case trimmer back out to 1.285. For what it's worth I have been very satisfied with that trimmer once I found out they had a cutting head that would trim and chamfer at the same time.