Benjamin 312 RestoMod

[Techie]

There's nothing better than actual scientific testing of results. 

[avator]

BTW.. I figured out which gun I was referring to earlier when I spoke of the butt plate being removed.... it was the Sheridan stock I sent to DeZ.... CRS !!

[Tack Driver 10]

Made a new FT test piston with polyurethane o-ring seals.
Chrony tested almost identical to the previous poly seal piston.
Ran it with 70 and 90 duro seals.

With 14.3 CPHPs   70 duro seal
05 pumps 602 FPS 11.51 FPE
08 pumps 703 FPS 15.69 FPE

With 14.3 CPHPs   90 duro seal
05 pumps 600 FPS 11.43 FPE
08 pumps 702 FPS 15.65 FPE

[Dave S]

Made a new FT test piston with polyurethane o-ring seals.
Chrony tested almost identical to the previous poly seal piston.
Ran it with 70 and 90 duro seals.

With 14.3 CPHPs   70 duro seal
05 pumps 602 FPS 11.51 FPE
08 pumps 703 FPS 15.69 FPE

With 14.3 CPHPs   90 duro seal
05 pumps 600 FPS 11.43 FPE
08 pumps 702 FPS 15.65 FPE

Very impressive! Will it dump all the air with 10 pumps? Just curious. dave

[Tack Driver 10]

Made a new FT test piston with polyurethane o-ring seals.
Chrony tested almost identical to the previous poly seal piston.
Ran it with 70 and 90 duro seals.

With 14.3 CPHPs   70 duro seal
05 pumps 602 FPS 11.51 FPE
08 pumps 703 FPS 15.69 FPE

With 14.3 CPHPs   90 duro seal
05 pumps 600 FPS 11.43 FPE
08 pumps 702 FPS 15.65 FPE

Very impressive! Will it dump all the air with 10 pumps? Just curious. dave

It retains some air with 10 pumps but it's set up for 8 pumps.
Gets difficult to pump 8-10 pumps.
I'm going to make a new brass valve seat that will allow 10 pumps this weekend.
Similar to the one I made for the 317 restomod.

https://www.gatewaytoairguns.org/GTA/index.php?topic=160425.msg155784790#msg155784790

[Tack Driver 10]

Made the new valve seat.
It has an 1/8" shaft, Delrin head, and .195" throat vs .215" on the stock seat..
Threaded the tail 1/4 x 28 vs 9/32 x 32 for the stock seat.
Opened up the port sideways since there is no alignment key, just have to position the seat at 12 o'clock mol.

Not sure if I'll put the seat in this gun or a 342 I just acquired.

[2K1TJ]

A work of art! Can't wait to see how it performs.

[Tack Driver 10]

Ordered a Mac-1 billet lever for this gun as well as the 342.
Should make the guns more solid when pumping and durable.
Need to make a larger wood pump arm also.

Like Hans and Franz said...."We just want to pump you up!....LOL

[avator]

Ron, you're gonna make me wanna buy that gun back..... lol

[Tack Driver 10]

Pulled the stock bolt out and made a brass replacement with an o-ring seal.
The original bolt is a flow through type but I like this style better.

[Tack Driver 10]

Installed the brass bolt on the gun and tested.
With 14.3 CPHPs   
08 pumps 708 FPS 15.91 FPE

With 15.9 JSBs   
08 pumps 680 FPS 16.32 FPE

Swapped out the valve seat.
With 14.3 CPHPs   
08 pumps 703 FPS 15.69 FPE

With 15.9 JSBs   
10 pumps 740 FPS 19.33 FPE (full dump)

The brass bolt didn't seem to make a difference so the stock bolt was sealing good.
The stock bolt had almost .010" of clearance in the breech so made the new bolt plus .008", .288" vs .280".
No need for the little spring and ball anymore.

The ported valve seat and sealed bolt combo really came alive with 10 pumps and the heavier JSB pellets.
The barrel is only 19" so a longer barrel with larger ports would really help at the high end.
I'll run some more tests with heavy pellets after I install the Mac-1 billet pump arm.
An interesting note, the valve seat only has the front seal installed in all the tests as was done previously.

[avator]

I bet that thing has a nice 'crack' to it when shot.

[Tack Driver 10]

I bet that thing has a nice 'crack' to it when shot.

Has a nice crisp snap reminiscent of my hot rod V1 760 with the blow off valve.

[Tack Driver 10]

Received the Mac-1 steroid pump levers today.
Super heavy duty and high quality, AAA+++.
Came with a bottle of "Secret Sauce".

Have a nice piece of walnut for the pump arm.
Turned it to 1.70" vs 1.20" of the original.
Here it is on the 342 gun still needing some final fitting and sanding.

[Dave S]

Received the Mac-1 steroid pump levers today.
Super heavy duty and high quality, AAA+++.
Came with a bottle of "Secret Sauce".

Have a nice piece of walnut for the pump arm.
Turned it to 1.70" vs 1.20" of the original.
Here it is on the 342 gun still needing some final fitting and sanding.

Man, that handle looks like a  33 Louisville Slugger!   Some sanding , a little Walnut Minwax and some  Tung Oil.....and you're good to go! dave

[Tack Driver 10]

How do you like me now?....LOL

Sanded and stained the pump arm.
Matches this 342 stock really good so may have to make another for the 312.

[avator]

Wow !    I'm liking that Ron.

[Techie]

This is just great Ron.  I didn't know the steroid billet lever would fit the 312.  Did you have to modify it and make a new endcap? Really nice job on the forearm.

[Tack Driver 10]

This is just great Ron.  I didn't know the steroid billet lever would fit the 312.  Did you have to modify it and make a new endcap? Really nice job on the forearm.

The forearm and steroid link make the gun look like a serious pump shotgun.
Makes you want to grab it and rack that mutha!....LOL

The Mac-1 billet levers are a direct drop in.
They're pre-drilled so the tootsie can be transferred from the old link.

I'm going too use the original end cap for now but may make a new one.
The stock cap has a good deal of play and it is too short by about .435".
The pump arms are .250" thick and the slot in the cap is about .280".
Both my 312 and 342 have 2 roll pins that hold the front end together.
The fit of the pump link to the end cap makes a huge difference in how the gun pumps.

[2K1TJ]

That really looks nice, Ron!