S&W 78g with MAC 1 hot valve

[Multigunner]

Can't give you a proper review, I don't have a chronograph and can't post images of my own .22 78g, but I'm so pleased with the results of my rebuild I just had to post of it.

This pistol has a long history with me. A friend found it buried in a lake bottom about thiry years ago or more and gave it to me.
The finish of the slide had disintegrated but the frame retains 100% of its finish even now. The frame is as well made and finished as I've seen on an air gun, and better than almost any of the less than top quality fire arms of today.
The grips were badly warped so I carefully heated these over a stove eye and reshaped them by hand.
I was able to match the finish on the slide by baking on flat black outdoor then lightly buffing with steel wool and then buffing with cloth.

I had to replace all the O-rings after its years submerged in mud, but the exhaust valve still worked fine and it lasted many years. When the original exhaust valve gave up the ghost I ordered an NOS replacement from Numrich Arms. That valve worked great till a couple of years ago then suddenly disintegrated without apparent reason other than age.

Awhile back I started looking for a reseal kit, but at first the only ones I could find had a dinky looking solid plastic valve. Then I discovered that MAC 1 Airguns was marketing a kit with a brass valve of their own design made from the highest quality materials. The valve's seal portion as well all the O-rings are made from a 90 Durometer urethane.
Price was right as well. The MAC 1 kit cost less than the plastic valve kits offered by other vendors.
If you choose to rebuild any CO2 gun with the 90 durometer seals you must remember that because the material is so hard and tough you should heat the entire gun up to toasty warm to soften the seals a bit before you first charge it with CO2. Not too hot, about as warm as you can get it with a hair dryer.

After I finished resealing and test firing I found the pistol now shoots harder at its lowest power setting than it had at its highest setting with the OEM valves. A review of one 78g rebuilt using this valve chrono'ed at circa 480 FPS using 14.3 gr pellets.

These pistols , the S&W branded version at least, are very well made and very accurate.
Aside from the finish coming off the slide and a dusting of rust on the grip screws the metal parts showed no sign of corrosion at all after years in the mud, the bore remained perfect and unblemished.

Daisy bought the rights to the design and manufactured it as the 780 and 790 (.177)pistol. I haven't handled one of those but owners of those seem to like them.

So if you ever run across one of these in complete but non working condition I suggest you get one and rebuild it using the MAC 1 hot valve kit. It should last several decades , mine will very likely outlast me.

[jh45gun]

I like my 78 G. I was not aware Mac 1sold the parts. I got my reseal kit from JG Air guns which had all the seals and a new valve stem designed to let more air out faster.

[Multigunner]

I just looked those up. It shows what appears to be a solid plastic valve with steel shaft, a scaled up version of the type found in the Crosman 760 and probably most recent Crosman guns. Not bad but the MAC 1 valve is made of brass with a urethane seal, much like the older ones but without the large square portion and much lighter. I would guess that either works very well, but the brass MAC 1 has more class and may be more durable in the long run. Prices for the kits are the same. The MAC 1 O-rings in their kit are all the same white urethane as the end cap seal in the kit you got. These are a beast to get on because they are not stretchy at all.
I think the MAC 1 valves are made one at a time by the owner, not really mass produced. He can also replace the seal on the original valve with the urethane seal at a reasonable price. He is certainly a skilled craftsman.