The 500ATP8SP showed respect here:

http://www.gunbroker.com/item/714039963

I know this is an old post but I just stumbled upon it. I'm not sure your answer is completely true. I have an older model Mossberg 500 ATP 12ga I purchased in Ogden, KS back in 1983. I always thought it had a 20" barrel but when I removed and measured it came out to 24". It has a ramped rifle front sight and folding rear and also a bayonet mount. It has a 7 rd magazine and the barrel and magazine are gray parkerized while the receiver is flat black. The wood furniture is not polished. The barrel is marked "Chambered for 2 3/4 and 3 inch shells-12 ga cylinder bore-Made in the U.S.A". The serial number is H700XXX. I emailed Mossberg about the shotgun and they told me it is a model 590 Military Model.

Welcome to ShotgunWorld, sdacbob. As you can see, your serial number H700XXX was made about 1981-1982 which matches your purchase in 1983. You may find "Mossberg 500 ATP8S" stamped just forward of its loading port, but I doubt it because that had a 20" barrel. Mossberg was not exact with those stampings back then, so it could simply be stamped Mossberg 500 ATP or even Mossberg 500. It could not possibly be a "model 590 Military Model" because they were not introduced until 1985 (usually reported incorrectly 1987). The Mossberg CS rep was mistaken because he associated the bayonet lug with the model 590.

You do not remove a barrel to measure its length. Please close your action and the bolt face will meet the chamber. Now drop a dowel into the barrel and mark it where it comes out of the muzzle. You will find that you indeed have a 24" barrel with a rifle front sight ramp, a folding rear sight, and also a bayonet lug, just as you say, with a 7 round magazine tube.



Sure, I could be wrong, but mick53's 500 ATP gun came with a 24" barrel that I doubt was original to his gun because it had a takedown screw set up for a 5 round magazine. How do I know? He traded it for an 18.5" barrel and they have always been made with a takedown screw set up for a 5 round magazine tube. He did think that the magazine tube is about 15" and he guessed a 5 + 1 capacity.

Unlike a 590 with its magazine cap, please confirm that your original 24" barrel has a takedown screw specifically placed for a 7 round magazine.

The 500ATP8SP has a "special non-glare finish on metal parts and oiled walnut stock and fore-end" and otherwise is the same as a 500ATP8. SP=SPecial and the S in this case could not mean "rifle Sights." True, it has a bayonet lug, but it has a 20" barrel with a bead sight. The models 500ATP6S and 500ATP8S has "blade front on ramp; folding leaf rear" rather than "bead front on ramp; folding leaf rear" as printed in the previous 1976 image; however, they have an 18.5" and a 20" barrel and neither have a bayonet lug.

I was unaware of your unusual model and Mossberg was probably not very exact if they stamped your 24 inch "500 ATP". Please do report your stamping forward of the loadng port. Do you still have the box or sales receipt?

You have a rare old 24" 500 ATP with rifle sights, a bayonet lug, and wood furniture. I have four 20" 500 ATP or LE Persuaders with wood furniture and I am still envious of you, sir. Good luck!