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All Springer/NP/PCP Air Gun Discussion General > Daisy Gate

Metal Receiver Separation on the 880 style guns

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pblawler:
I have noticed on several guns and even since I was a kid that on some of my 880s the receivers won't stay closed.  After a bit more thought I think it is aggravated by scope mounts (examples below).  The dovetail is on the right receiver and when the scope mount clamps down I think it is putting pressure on the receiver halves and pushing them apart.  The receiver halves only connect directly through the rear large stock bolt.  They are cantilevered off the main frame.  I think this could lead to the Zero drifting over time.





 The new plastic receivers have two additional screws that connect the halves near the dovetail.  I think adding similar connections for the metal receivers would help accuracy and prevent the zero from shifting over time.  I found some 3mm aluminum standoffs that looked like they could work.  I took a salvaged receiver and drilled a 1/8" hole above the bolt guide on the inside of the right receiver.  I then put the two halves together and drilled through the left receiver using the previous hole as a guide.  I did the same thing to the front of the receivers making sure the first hole was above the barrel.  I then used 3mm pan head socket screws to connect the halves.  I screwed one side into the standoffs then put the halves together and installed the screws on the other side.  The result was a nice and securely assembled receiver set.  I will be doing this mod to all my modified guns with metal receivers.

pblawler:
I haven't assembled this yet but I believe it should also help with loose stocks.  The electrical tape around the stock tangs to tighten up a loose stock has been around since the 80s I know of but I think it just makes receiver separation worse.  As the receivers split further the stock will get loose again and the so on. 

pblawler:
So I shot my metal receiver 1977 Mod today and it was hitting right 3" at 50 yards.  I have encountered this over and over.  The plastic receiver 1977s actually hold zero better.  It must be the upper receiver screws on the plastic receivers that keep the receiver halves held together so there is less movement.  On the metal receivers the scope is cantilevered with only the two tiny screws on the side of the receiver and the one low mounted rear screw.  Each time the gun is leaned up against the wall and the scope has pressure on it it can move the right receiver.  Even 0.010" movement can be very significant at 50 yards through the scope.   Over weeks of torque leaning against the wall touching the scope that can add up fast.  Even being careful not to touch the receiver or scope that's too much to keep confidence in a gun and takes the enjoyment out of an air rifle.  I am going to do the above mod to my 1977 modified 177 and see how long it holds zero compared to the factory fasteners.  I suspect it will be a HUGE improvement.

pblawler:
I did the mod and it has helped hold zero for a month of hard use.  I did the mod to three of my modified guns.



M3x6mm  Socket Head Rivet Connector  (Just for 822 over barrel screw)


Pan Head Screws  (For 880,822, 1977)


Aluminum Standoffs M3x15mm (For 880,822, 1977)

Ronno6:
You sure tale the venerable old 880 to a new level!
Nice work and great video!

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