I have a 1924 Ithaca Flues 16ga. Only after firing the gun is hard to breech. Top lever is to the right on lockup. No slack or wiggle when open or closed. Opens simply by moving top lever to the right when unfired. Floating firing pins but don't seam to be sticking. Cocking plunger (as i have seen in pics) hump is now flat. i am not sure wheather or not if this could be the problem or it lies elsewhere. Any help?
The cocking lever is either worn or bent, or the hammer toes that engage the cocking lever are worn or bent. Flues guns are notorious for this. The hammers are cocking too late due to the wear and the firing pins are dragging in the primers as the barrels try to open. This can be adjusted back to proper functioning via TIG weld and refitting by a competent smith. Be forewarned not to try to "bend" these parts back into compliance, they are hard and will most likely break, compounding the issue.
Check to make sure the gun is empty...
Then dry fire both bbls.
Now holding it shut,,open the lever all the way.
Then let the weight of the bbls drop down slowly till you feel the cocking arm/lever just start to engage the hammers.
You don't want to re-cock the gun,,just looking for the engagement point of the parts.
You may have quite a gap at the top of the breech at that point and the muzzles down more than a couple of degrees from horizontal.
What it tells you is that the hammers would be full down onto the firing pins and against the primers. Dragging all that distance the bbls had to open before the system started to retract the hammers taking the pressure off the pins.
As Dan says, don't try to bend things or hammer them back into position.