model 11 barrel change

I bought a military marked barrel for one of my model 11 shotguns that has a military marked receiver. It fit the gun but will not feed the shells and work like the cut down barrel that was on the gun when I bought it. I put both barrels side by side and there are a couple of different changes. I thought the barrel might be for a much earlier gun, I have looked on the webb for information about these guns but have found nothing about this. If anyone could help with information on barrel changes thanks.

Are you sure it's a Remington barrel? Savage barrels will fit the Remy receivers but may need fitting to operate. They also had Ordnance marked barrels. I fitted a Savage barrel to one of my M11s and it took polishing the barrel extension to get it to fit. You have to disassemble the receiver and see that the extension freely travels the full length of the receiver.

Thanks Gunluvver for your suggestion the barrel is marked remington but has a couple changes that the barrel that works doesn't have. I tried the military marked barrel in another model 11 but the action would not cycle in it either. I bought a really nice walnut stock for an 11 at a gun show over the weekend it will not fit any of my model 11s, I think it might fit one of the guns with the safety in front of the trigger. I am not having good luck buying parts that work but these model 11s are my favorite shotguns.

late barrels wont usually work on early receivers without fitting.
very important to check headspace when swapping barrels on these shotguns.

I am trying to headspace a model 11. Most importantly I have no idea how to adjust Headspace.

Any advice on how to adjust it on an auto like the 11?

no way of {adjusting} if it wont safely headspace, then a nother bolt or barrel should be tried.