Chamber should stay closed . . . right?

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Prof Young

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I have a Winchester 1300 12ga. It's a pump, of course. When I fire it, the chamber comes part way open. That should not happen, right? When you shoot a pump shotgun the chamber should stay closed until you pump it, right? It's been doing this for a while but it didn't click in my brain until yesterday that something is wrong. Help?

Prof Young
 
Perfectly normal. When you fire it it unlocks the pump mechanism. The swelling of the shell under pressure and recoil keeps the chamber closed until well after the ejecta is long gone out of the barrel. Most pumps do the same thing, but Winchester touted the fact theirs did it faster. If I shoot my Wingmaster one handed it will eject the empty shell.
 
Defining part-way ???

It's a pump, of course. When I fire it, the chamber comes part way open. That should not happen, right?
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Partway really has to be defined and if it's clearly noticeable, than for what ever reason, it's not normal. I have the same model and even though I understand that this is how it operates, I am have never noticed it. Keep working with it and see if the problem, goes away..... :confused:

Be Safe !!!
 
Clean the gun make sure there is no crud built up where the bolt locks, then
Fire the gun without your hand on the forearm (so there can be no question of you opening it) if the action opens, on its own, it needs work.
 
If the shooter has a normal forearm hold, that hold is in slight tension.
When the action unlocks upon firing, that tension will naturally open the (now) unlocked action and pre-initiate the slide moving backward.

It's one of the reasons that pump actions can be so incredibly fast.
 
Took the tightest of the three 870's out tonite -- the ATAC.
Ran light 3/4-oz skeet loads

two loads with forearm hold -- it opened upon firing/unlock
one with no forearm hold -- it was already unlocked/cracked open when I took hold of it again.
 
That is not unusual at all. Most pump guns unlock when you press the trigger. Then the recoil hits the bolt and trys to shove it to the rear. Sometimes that force is enough to move the fore-end/ bolt slightly open.
 
Winchester used to advertise that as a feature to make them faster to operate. They called them the "Speed Pump".

http://looserounds.com/2020/07/13/the-winchester-model-1300-the-forgotten-shotgun/


Winchester always claimed that the 1300, which they nicknamed the “Speed Pump” was a faster design than what Remington and Mossberg offered in their designs, and I can actually agree. According to the manual; after the shotgun is fired, the locking lugs of the rotary bolt begin disengaging from the barrel extension and the recoil forces assist the slide in moving rearward. You can actually see this when you hold up a empty unloaded Model 1300 muzzle up. The shotgun unlock itself.
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In my experience the feature works as advertised, but I don't think it actually made it faster to operate the action. In the end how fast you work the action comes down to how smooth everything operates. While the 1300 got a head start, I could never work the action any faster than an 870
 
OK,so newer shotguns are supposed to work that way, I guess. I know for a fact that the Winchester Model 12 does not.

ITs action remains firmly locked shut after the trigger is pulled, UNTIL you put some FORWARD pressure on the forearm. THEN it unlocks. Most of the time, the forward bump needed is supplied by a firm hold on the forearm, during recoil, Most model 12 shooters learn early on that you don't pull back on the forend when shooting you push forward until after the shot.

The model 12 can be fired as fast as you can pump it, if its one of the originals without a trigger disconnector. Done that, too!

the Rem 870 works a bit differently is slicker feeling, and of course has a disconnector.

I don't have personal experience with the Win 1300 but if it was based on the Win 1200 its inferior to the Rem 870. In my opinion.
 
Gough Thomas once clamped weights to the foreend of an Ithaca 37 and shot it without holding the foreend. When he got the weights right, it kicked itself open and ejected the empty.
 
OK,so newer shotguns are supposed to work that way, I guess. I know for a fact that the Winchester Model 12 does not.
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Not all newer shotguns. To my knowledge only the 1300 with the rotary bolt. And I'm not even sure if all of them have the rotary bolt. The current production 1300's are made somewhere overseas and I don't know if they are even the same gun. I've not handled one in years.

The 870 and most others that I've used do not, but once well broken in most of those will unlock and cycle plenty fast.
 
It is normal. I shot a 1200 & 1300 for many years. It only unlocks AFTER the shot charge is gone. So no big deal. It will help you pump it faster........Don't worry.......Go shoot!
 
The Winchester Model 12 was designed so that after the hammer drops the fore end must move forward slightly before it will come back. When a round is fired recoil takes care of that.
In reading over this it would appear a lot of people do not understand the basic physics that govern operation. A.22LR or a 9mm semi auto basically operate as blowback designs, consider that. BTW, neither design loses velocity versus a fixed breech design.
 
A.22LR or a 9mm semi auto basically operate as blowback designs, consider that. BTW, neither design loses velocity versus a fixed breech design.
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Strange, MY 9mm is locked at firing same as my auto shotgun.

A gun writer once made a clamp to hold the bolt of a Ruger Mk 1 closed. He found slightly HIGHER velocity with the gun allowed to cycle than with the bolt held shut. His theory was that the initial slip as the bolt started to move let the case seal a bit better.
 
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