Benjamin Franklin 317 RestoMod

[Tack Driver 10]

Received a BF 317 to fix and add some performance mods.
This is a 1961 version and is in pretty good condition.

The gun won't build pressure and the arm springs back to 90 degrees.
Possibly a sticky check valve or a pump arm adjustment.

The gun has been opened and rebuilt in the past and more recently resealed.



 

[bantam5s]

Well it definitely looks nice.

These little guys have some decent pop so I don't know what kind of performance mods one could want, but I'm sure the results will speak for themselves.

[Tack Driver 10]

Time to open this gun and get down to the nitty gritty.

The valve retaining nut unscrewed without incident but the removal tool wouldn't thread onto the valve seat.
Went with plan B, pumped the gun and the valve internals exited with one pump.

Houston we have a problem!

The valve seat threads are all but missing in action.
Magilla Gorilla must have worked on this gun.

Aside from the valve seat issue the check valve seal is deteriorated causing the original malfunction.

No problem:

"We can rebuild it.
    We have the technology.
        We can make it better than it was.
            Better...stronger...faster."

and it won't cost 6 million dollars.....LOL

[BrushPopper]

Fascinating little rifles.
They put alot of pepper in a tiny package.

I’ve got a spare seat, good threads but the rest is in pretty poor shape. I doubt you’d want this one, else I’d mail it over

[Tack Driver 10]

Fascinating little rifles.
They put alot of pepper in a tiny package.

I’ve got a spare seat, good threads but the rest is in pretty poor shape. I doubt you’d want this one, else I’d mail it over

The game plan is to make a new seat with a concave Delrin stem.
Would be nice to have the original seat though.

[BrushPopper]

You have a lathe, then...

Might it be easier to cut new threads on the seat, and fab a simple insertion tool with with matching threads?

Maybe something to consider, prolly take less time than a scratch replacement.

Maybe even an insertion tool with a slip-fit for that stripped nipple.

Just thinkin’...🤨

[Tack Driver 10]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

Just for fun made a removal tool to resemble the wood pump arm.
Check out the touching father and son moment....LOL

[avator]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

Just for fun made a removal tool to resemble the wood pump arm.
Check out the touching father and son moment....LOL

This is why I waited to respond.... I've seen your work before.

[Matchstickshooter]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

Just for fun made a removal tool to resemble the wood pump arm.
Check out the touching father and son moment....LOL

This is why I waited to respond.... I've seen your work before.

Makes me wish Oklahoma was next door to Lyndon,Vt 

[Psipumper]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

Just for fun made a removal tool to resemble the wood pump arm.
Check out the touching father and son moment....LOL

I like the way you built a better part optimized for .177. You could use a  Maurauder poppet with the new stem size.
I have not seen anyone attempt to improve a 312/317 before. I would think a smaller valve cc could help the 317.
Glad you are on the job. Interesting to follow this.

[Tack Driver 10]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

Just for fun made a removal tool to resemble the wood pump arm.
Check out the touching father and son moment....LOL

I like the way you built a better part optimized for .177. You could use a  Maurauder poppet with the new stem size.
I have not seen anyone attempt to improve a 312/317 before. I would think a smaller valve cc could help the 317.
Glad you are on the job. Interesting to follow this.

The way the valve seat is cut allows either a concave stem or a 13xx or Mrod stem.
This one will be made using 1/8" drill blank with a Delrin head and concave seat.
A light SS valve spring will replace the heavy stock spring.
A poly bumper on the back of the valve will limit stem travel to 1/8" and protect the valve from impact.
Should get the valve internals done in the morning.

A power adjuster and FT piston are next on the list.
The current piston seal looks very good.

[BrushPopper]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

I was reading DT Fletcher’s book on the 160. When T Mac designed the QB guns, he made the TP dia. .180.

I guess he decided it offered optimal performance, but this was using Co2. Might be different dynamics vs compressed air.

Good looking parts there!

[Tack Driver 10]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.

I was reading DT Fletcher’s book on the 160. When T Mac designed the QB guns, he made the TP dia. .180.

I guess he decided it offered optimal performance, but this was using Co2. Might be different dynamics vs compressed air.

Good looking parts there!

Right, CO2 needs larger ports as does 22 cal.
Here's a good reference for determining TP size:

[Matchstickshooter]

Made the valve seat this morning.
Has a concave seat and .125" shaft, the stock shaft was .156".
Throat is .200" vs .220" for the original.
Made the TP opening .156" and ported it.
Oddly the original TP is .187" which is big even for a 22 cal.
The thread is 1/4-28.
[/quote

I was reading DT Fletcher’s book on the 160. When T Mac designed the QB guns, he made the TP dia. .180.

I guess he decided it offered optimal performance, but this was using Co2. Might be different dynamics vs compressed air.

Good looking parts there!

Right, CO2 needs larger ports as does 22 cal.
Here's a good reference for determining TP size:

You sure turn out some nice stuff! I'm amazed at what you can make.  

[Tack Driver 10]

Made the valve internals this morning.
Replacing the heavy spring with a spacer and light SS version.
Made the check valve and valve stem.
Orange seals are duro 90a cast polyurethane, white is Teflon.
Also fit the power adjuster to the tube.

[jackssmirkingrevenge]

RestoMod

I like this expression, and for older airguns that aren't exactly a rarity I think extracting more of their potential is a nice path if tastefully done.

Excellent work, looking forward to see this finished!

[Tack Driver 10]

RestoMod

I like this expression, and for older airguns that aren't exactly a rarity I think extracting more of their potential is a nice path if tastefully done.

Excellent work, looking forward to see this finished!

Roger that, don't want to get too crazy with the cheese whiz on these classics.
All the mods performed on this gun are reversible, none of the original parts were harmed.
The mod equivalent of having your cake and eating it too....LOL

The power adjuster can be left au naturale to tarnish or painted/coated.


 

[USAFANG6799]

It's a interesting sight to see a master craftsman at his best working on a iconic classic like the 317.
I bet the original designers never envisioned the 21 century would bring these wonderful ideas to the 317.
Keep the camera rolling you have your audience on pins and needles 

[Tack Driver 10]

Made a few more parts over the weekend.

The bumper is duro 80A polyurethane and limits stem travel to .140".
With it the gun can be dry fired all day without harm.
It's Barney approved....LOL

The little screws on the PA are #2-56 for those with inquiring minds.

Should get the gun together in the morning.

[cobalt327]

Outstanding craftsmanship... thanks for sharing.