With the recent aquisition of FWFL bullet lube, I decided to load up a batch of the Lee 240gr HP GC bullets for my Contender, using the new (to me) lube.
Load was 23.5gr H-110, under the above bullets (which run about 235gr, from my alloy), CCI lg pistol Mag primer, and mixed WW and Federal cases-about half and half. This load should be about middle of the road, as a check of several manuals shows an average spread from 20gr to 25gr for the 240gr bullet - some cast, some jacketed.
When I fired this load from my 10" T/C Contender, it turned it into an auto-unloader! First shot, something hit me in the lower lip - Hard! The gun was locked up tight, but it had no case in the chamber. I'll admit to being bumfuzzeled for about a minute, until my brain kicked in. It bounced back down on the front rest, and closed itself. As I had been doing some work with a homemade muzzle brake, I fired 2 more, with the brake removed, for testing (I might also add, these were fired with my hand on the other side of a metal plate from my head & body!) Results were the same, with the exception that it didn't bounce back down on the rest, and close - it stayed unlocked/open.
The primers looked normal, i.e., they exhibited a very slight(normal) amount of flattening, but the radius was still fine, with no cratering. There was a slight dragging of the firing pin on the bottom of the indent, but I would expect this with it comming open due to an aparent overload. Sorry, but the chrono didn't make this trip.
Aside from questions about the gun, what would you suggest might have caused this aparent overload? I can't say I have fired this particular load (I did find one load at 22.5gr)from this gun before, but it has digested comparatively much heavier loads, without problems - like 20gr 2400, and a 315gr cast.
Pulling the bullets showed correct powder charges, and correct bullet weights. I was going to try them in my Taurus, but decided not to push it, and pulled them all down. For those of you that will say "work up to your load" reducing a max charge (25gr) by 10% would be 22.5gr.
I wasn't looking for a really hot load, and picked what I thought would be a reasonable one. T'wasn't so... What 'chall think?

P.S. This barrel had the lugs fitted by T/C, and I havent messed with it since. I couldn't find any reason for this ocurrance, but rest assured, I WILL reduce some more! And, the cases had been wiped off after loading, so lube on the cases shouldn't have been a factor. And, recoil, while a bit stiff, wasn't anything remarkable for this barrel. It's sure got me scratching my head!

Update: I found some of the 22.5gr loads, I had loaded a year or so past. I tested them, and they only unlocked it about 1/2 the time! Then a little light went on... I think this barrel had been fitted to my other frame! Can switching frames cause something like this, without having lock-up/misfire problms? Please help........Bug.

I would say that the lugs aren't catching/ engaging properly on this frame. Try another frame and see if it still does it. I had this happen on a 30-30 before and it was the engagement of the lugs. FWIW..

I had the same exact same thing happen on two different barrels, one was a 14" 7mm Intrl-R and the other was a 10" 7-30 Waters.

Come to find out there are more than one size lugs and changing them out to the next larger size up solved my problem on both barrels.