GTA
Airguns by Make and Model => Vintage Air Gun Gate => Topic started by: Tack Driver 10 on July 17, 2019, 07:32:48 PM
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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.
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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.
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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
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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
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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.
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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’...🤨
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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
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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.
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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
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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.
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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.
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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!
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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:
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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. ;D
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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.
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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!
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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.
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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 8)
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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.
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Outstanding craftsmanship... thanks for sharing.
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Made a few more parts over the weekend
Amazing the goodies that are going into this 317.
When you try it out I don't think it will recognize itself ;D
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Put the gun together without incident.
Ran it over the chrony to get a base line.
With 7.9 CPHPs
3 pumps 435 FPS
5 pumps 601 FPS
7 pumps 644 FPS (dumped all the air)
Respectful numbers but, I have only just begun to mod....LOL
The bolt leaks and there's a blast of air when the gun is fired even when adjusted.
The stock bolt not only leaks but the probe tip is 1/8" and cocking the gun is rough.
Best described as dragging a bag of rocks down a cobblestone drive.
One of the problems is the breech is very short and the bolt hangs out the back usually scraping against the tube when cocked.
The heavy hammer spring compounds the matter.
When the going gets tough, the tough get going and make a new bolt....LOL
Made a prototype brass bolt with an o-ring seal and .070" probe tip.
The elongated back will sit on a Delrin saddle resulting in a buttery smooth cocking experience.
The saddle is set in a counter bore in the PA.
Might have to make a new, slightly longer PA to accommodate the saddle.
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644 FPS - Respectful numbers for sure given how long it's been in a coma ;D
I'd say those first few words are pretty encouraging.
Loose bolt probe, no oring, blast of air, scraping against the tube when cocked with the sense of dragging rocks down a cobblestone drive..........sounds pretty normal from what I remember. :-[
Amazing it shot the FPS's you just reported as well as it did.
Many thanks for the encouraging update with the best is yet to come news.
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The lug on the bolt requires a 5-40 thread so I have a tap in the mail.
Should be in around the end of the week.
In the meantime since I have some spare rods I made an experimental piston.
It's made from Delrin with a 80 duro polyurethane seal.
Same poly I used for the bumper.
Instead of a slot I drilled 8 holes equally spaced around the edge.
The holes will allow a certain crush factor and expand with pressure as the gun is pumped.
Plus I think it looks kind of cool....LOL
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You definitely have my attention Ron. As you know I have a 312 here. I wonder if you would consider putting together a kit that would include some of these upgrades as a drop in? If so, please PM me.
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Instead of a slot I drilled 8 holes equally spaced around the edge.
The holes will allow a certain crush factor and expand with pressure as the gun is pumped.
Very imaginative!
Talk about boldly going where no one has gone before!
Braking new grounds with this idea or have you see it used somewhere else?
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Nice rehab. Can't wait to see the
finished re-finished product!
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Instead of a slot I drilled 8 holes equally spaced around the edge.
The holes will allow a certain crush factor and expand with pressure as the gun is pumped.
Very imaginative!
Talk about boldly going where no one has gone before!
Braking new grounds with this idea or have you see it used somewhere else?
Something I came up with instead of a groove in the seal, patent pending....LOL
I like this version better, easier to make and can vary the hole size, depth and spacing.
I stated there were 8 holes but there are actually 12 spaced 30 degrees apart.
Once the bolt is finished I'll run another chrony test with the stock piston then with this one.
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You definitely have my attention Ron. As you know I have a 312 here. I wonder if you would consider putting together a kit that would include some of these upgrades as a drop in? If so, please PM me.
Ron...
Well, I guess we can forget about this...
As I'm sure you know, a deal is in the works for this gun to be headed your way then on it's way to a new owner... pretty sure you'll find that it won't need much mechanical improvement.
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You definitely have my attention Ron. As you know I have a 312 here. I wonder if you would consider putting together a kit that would include some of these upgrades as a drop in? If so, please PM me.
Ron...
Well, I guess we can forget about this...
As I'm sure you know, a deal is in the works for this gun to be headed your way then on it's way to a new owner... pretty sure you'll find that it won't need much mechanical improvement.
Looked like a nice gun.
Thanks for the update.
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Not a safe queen but a solid shooter with lots of cosmetic potential. I was proud to be it's care taker while I owned it.
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Instead of a slot I drilled 8 holes equally spaced around the edge.
Don't the holes create dead volume that effectively limits the maximum pressure that can be reached?
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Not a safe queen but a solid shooter with lots of cosmetic potential. I was proud to be it's care taker while I owned it.
How many owners before you Bill? Or is it too late to ask ;D
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Instead of a slot I drilled 8 holes equally spaced around the edge.
Don't the holes create dead volume that effectively limits the maximum pressure that can be reached?
Thinking on the same line. Thinking that it's being offset by the holes expanding the cup which make a tighter seal as the compresses the air ahead of it.
The advantage I see to this design as the seal gets used over time the seal is still able to expand to help overcome the wear that's overcome by the conventional seal design.
I'm sure Ron will fill us in though.
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Instead of a slot I drilled 8 holes equally spaced around the edge.
Don't the holes create dead volume that effectively limits the maximum pressure that can be reached?
Exactly, these guns are not built for high performance.
The long stroke brass/bronze wall tube is only about .055" thick and will bend when pushed hard.
Could also jeopardize the solder joint between the tube and barrel.
Leaving some air will limit max pressure but provide some spring back for the return pump.
A man's got to realize the limitation of the gun and leave a little safety margin.
I tried a FT o-ring piston on the last gun and the return was heavy with a strong gasp at the top.
Even the long stroke Crosman tubes made of steel and .060" thick walls will bend to a lesser degree.
To me an ideal stroke length is between 4"-5".
I have a 13xx gun with a modified 766 pump link and have pumped it to over 3400 psi.
The short 3 1/2" stroke and tube make for a very stiff pump engine.
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Not a safe queen but a solid shooter with lots of cosmetic potential. I was proud to be it's care taker while I owned it.
How many owners before you Bill? Or is it too late to ask ;D
Sorry, I don't know the answer to that.... Matter of fact... I have so many that I lost track and can't even tell you who I got it from... :-\
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Matt.... sent you another PM.
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Ron -
I have a 13xx gun with a modified 766 pump link and have pumped it to over 3400 psi.
The short 3 1/2" stroke and tube make for a very stiff pump engine.
When is it going to make it's day-view in the Classifieds? ::)
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Received the 5-40 tap for the lug on the bolt and got that done.
Ran it over the chrony with the original piston using 7.9 CPHPs.
Piston is adjusted at 7.375" the max without hitting.
3 pumps 556 FPS 05.42 FPE
5 pumps 662 FPS 07.69 FPE
7 pumps 694 FPS 08.45 FPE
Next installed the Holy Grail piston adjusted at 7.375".
3 pumps 508 FPS 04.53 FPE
5 pumps 648 FPS 07.36 FPE
7 pumps 750 FPS 09.87 FPE
8 pumps 763 FPS 10.21 FPE
Adjusted the Holy Grail piston to just over 7 7/16"
This allowed a slight cam over and the piston just cleared the breather hole in the tube.
For the 8 pump test I oiled the piston to see if the gun would beat 800 FPS.
3 pumps 544 FPS 05.19 FPE
5 pumps 727 FPS 09.27 FPE
7 pumps 773 FPS 10.48 FPE
8 pumps 826 FPS 11.97 FPE (full dump)
Interesting that there was still a slight puff of air coming from the breech area.
I dry fired the gun and figured the air is the result of the hammer pushing forward as the puff was still present.
Food for thought:
Generally a 17 cal will perform about 150 FPS faster than a 22 cal gun of equal design.
That means a modded 312 should produce about 675 FPS 14.35 FPE.
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Impressive results considering the original would be hovering around 500 fps at 5 pumps from what I've read.
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Drilled and tapped the bolt for the typical 8-32 Crosman bolt handle.
One is SS and the other is the stock handle.
I like them both but there is also a vast plethora of them available on Ebay to choose from.
The long SS bolt handle is p/n 392LE-009, about $10 from Crosman.
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It's hammer time, actually hammer spring time....LOL
Since the heavy valve spring has been replaced with a light version it's time for the hammer spring to follow suit.
The stock spring is .039" wire and 3 3/4" looooong.
Replaced it with a Disco spring with .034" wire and 2 3/4" in length plus a 7/16" Delrin spacer.
Also replaced the tiny ball bearing on the bolt with a Delrin rubbing block.
Can now cock the gun easily with my little finger.
Getting very close to the buttery smooth cocking experience we all dream of.
Personally I can't believe it's not butter!
How buttery smooth is it?
After cocking the gun a few times my phone rang.
It was my doctor.
I said what's up Doc?
He said your cholesterol!
He advised me to cut back on the butter....LOL
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Someone snitch on your using too much butter again 😄
The 317 (now know as 317 Express) is looking and shooting like a Twenty Century model had Crosman kept it updated.
Maybe Crosman would take your idea and run with it?
A carbine with this much power should be a hit!
Many thanks for the updates.
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Someone snitch on your using too much butter again 😄
The 317 (now know as 317 Express) is looking and shooting like a Twenty Century model had Crosman kept it updated.
Maybe Crosman would take your idea and run with it?
A carbine with this much power should be a hit!
Many thanks for the updates.
Can't a guy have at least some guilty pleasures?
What's next, take away the bacon and ice cream?....LOL
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Bacon and ice cream are bad? I'm doomed.
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Ron & Bill....you are not here in this world to think and feel you are on some kind of cruise ship. Ya here to work for da Man till ya drop or until he dismisses U by throwing you overboard in these shark infested waters.
Think of this as being on a Roman Galley as that is the closest thing you’ll experience to a cruise ship.
Today’s entertainment will be demolition derby with possible fireworks/flaming arrows.
Now back to it and put your backs into it girly men😜😭
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Ron & Bill....you are not here in this world to think and feel you are on some kind of cruise ship. Ya here to work for da Man till ya drop or until he dismisses U by throwing you overboard in these shark infested waters.
Think of this as being on a Roman Galley as that is the closest thing you’ll experience to a cruise ship.
Today’s entertainment will be demolition derby with possible fireworks/flaming arrows.
Now back to it and put your backs into it girly men😜😭
Such a fitting post to read on a Monday morning before starting the work week..
Thanks for the reality slap.... :o
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The pump arm had about .020" side play in the main pivot.
The pump arm was .250" and the slot in the front cap was .0270".
Cut two .010" brass shim washers to take it up.
The main pivot bushing and the link rivet looked good.
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I love this thread, been watching and enjoying.
You are so talented Ron and so funny with it too.
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The good, the Bad and the Ugly.
This ain't no spaghetti western pardner!
How's a cowboy gonna shoot straight with a crooked tootsie roll?
The tootsie roll on this gun is a wee bit off kilter to say the least.
Possibly a rough day in the wood shop, a Monday/Friday gun or too much Tequila....LOL
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Made a new test piston using a 392 style cup seal.
I was surprised the the dead air space is actually about 10% less in the cup seal.
Diameter measured .790" mounted in the piston vs .770" for the original seal.
I'll get it in the gun and chrony it post haste.
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Should take less pumps to max it, but wasn’t it retaining pressure @ abt 7pumps before?
Valve cap. Prolly still the same..
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Guessing a gain of about 10 more fps with the new cup seal?
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Adjusted the piston to a strong 7 3/8" and when installed in the gun due to the seal compression just cleared the breather hole.
So this version is at max length as tested.
With CPHP 7.9 g
3 pumps 575 FPS 05.80 FPE
5 pumps 675 FPS 07.00 FPE
7 pumps 750 FPS 09.87 FPE
8 Pumps 775 FPS 10.53 FPE
Performance wise, comfortably nestled in the bosom between the stock (worn) seal and the poly seal.
Realistically I believe this is the best alternative.
It pumps nice and smooth and the power is linear, very strong right out of the gate.
Replacement seals are available and inexpensive from Crosman.
I'm giving it the Tack Driver Good GunKeeping seal of approval....LOL
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Sounds like a winner, good job!👍
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Made a new piston seal from high end 90A cast polyurethane.
This one has 18 smaller holes spaced at 20 degrees and closer to the perimeter.
Adjusted the piston to 7 13/32" which is max while clearing the breather hole.
With CPHP 7.9 g
3 pumps 595 FPS 06.21 FPE
5 pumps 710 FPS 08.84 FPE
7 pumps 780 FPS 10.67 FPE
8 Pumps 796 FPS 11.11 FPE (full dump)
The low dead air space builds high power at the low end.
I ran it twice because I thought there might be a quirk, second time 3 pumps=593 FPS.
This version performed better than the cup seal and similar to the purple 80A poly seal.
It got harder to pump the last 2 strokes as it topped out but that is to be expected.
De-tuning the gun by adjusting the piston to 7 3/8" should be a good setup.
I'm also thinking of removing the spacer in the valve to gain more valve volume.
I think a good plan is to make a piston that will take either the cup seal or a poly seal.
That way either seal can be used.
A few more piston seal versions and you can have one for every day of the week....LOL
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So, if someone were to take the bull by the horns and make a piston that would accept either the stock cup seal or a poly seal.......
It might look something like this:
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A few more piston seal versions and you can have one for every day of the week....LOL
And or for what ever game ya going after ;D
Those are some very interesting designs Ron!
What a talent ya got!
Many thanks for infusing it into the 317!
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So, if someone were to take the bull by the horns and make a piston that would accept either the stock cup seal or a poly seal.......
It might look something like this:
Would this work for/on other air rifles that use piston or spring?
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Decisions ,Decisions , Decisions ;D
90A cast polyurethane:
With CPHP 7.9 g
3 pumps 595 FPS 06.21 FPE
5 pumps 710 FPS 08.84 FPE
7 pumps 780 FPS 10.67 FPE
8 Pumps 796 FPS 11.11 FPE (full dump)
Tack Driver Good GunKeeping seal of approval....LOL:
With CPHP 7.9 g
3 pumps 575 FPS 05.80 FPE
5 pumps 675 FPS 07.00 FPE
7 pumps 750 FPS 09.87 FPE
8 Pumps 775 FPS 10.53 FPE
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Decisions ,Decisions , Decisions ;D
90A cast polyurethane:
With CPHP 7.9 g
3 pumps 595 FPS 06.21 FPE
5 pumps 710 FPS 08.84 FPE
7 pumps 780 FPS 10.67 FPE
8 Pumps 796 FPS 11.11 FPE (full dump)
Tack Driver Good GunKeeping seal of approval....LOL:
With CPHP 7.9 g
3 pumps 575 FPS 05.80 FPE
5 pumps 675 FPS 07.00 FPE
7 pumps 750 FPS 09.87 FPE
8 Pumps 775 FPS 10.53 FPE
I'm going to make the decision easy for you.
Going with the last 90 duro poly seal.
De-tuned it should get around:
3 pumps 550 FPS
5 pumps 650 FPS
7 pumps 750 FPS
Won't know for sure until the deed goes down.
Should be able to get er done in the morning.
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Going with the last 90 duro poly seal.
That what I was hoping for but didn't know how this would effect the longevity of the 312 since they were never designed to shoot that hot.
Should be quiet the interesting rifle to shoot now.
It will be a basement or range only since I'm sure it will be pretty noisy now ;D
While I'm thinking of it......what is that number stamped on the bottom of stock on the 312?
It looks like a date code but not sure. I didn't think Crosman did that when they made them.
I did contact Bill this AM to request a refund of $140 which he promptly credited me this AM.
He said he was going to send you the $ to ship it back to him.
I said to him that I would pay to have the sights sent back to him so not to worry about the $10.
Matt
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Ron, I sent you a PM.
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Made the new 90 duro poly seal and cleaned the felts.
I'm always amazed at how much gunk comes out of them.
Put a new Big Fat American Felt up by the piston....LOL
Adjusted the piston to just under 7 3/8" and installed it.
It fully clears the breather hole with the pump arm open.
Chrony with 7.9 CPHPs:
1 pump 360 FPS 02.27 FPE
2 pumps 465 FPS 03.79 FPE
3 pumps 548 FPS 05.27 FPE
5 Pumps 672 FPS 07.92 FPE
7 pumps 732 FPS 09.40 FPE (full dump)
7 pumps 767 FPS 10.32 FPE (oiled)
About what I expected and gained 35 FPS when oiled with 7 pumps.
Possibly some wear in the tube bore but normal for an older gun.
If it's like my first gun, it got shot a lot more than it got oiled....LOL
The number stamped on the butt end of the stock is 361.
So March 1961.
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Those numbers are the best this 317 has seen even when it was new I'm sure. It should outlive me now for sure.
That's a mighty fine piston and rod assembly. Too bad the tube is not made of glass so it could show off it's stuff.
I'm saving the pictures as you update your progress. It will make a really great scrap book to go along with Resto Mod.
I have to figure a way to put this all together for a scrap book.
Many thanks for the update!
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I was thinking I was close to finishing this gun but it threw me a curve.
That's what I get for thinking....LOL
After the first pump the arm would spring open some.
It would pump up but something was amiss.
Looks like the poly check valve got smoked and was leaking.
Time to put on my Teflon Ron hat and fix this once and for all.
First thing I did was polish the check seat with 400 grit paper on the end of a dowel.
It had a weak area between the 1-3 o-clock position.
Then made the Teflon check valve and seated it using the PA and a wood dowel.
Installed the check valve, dowel and PA then tightened the PA screw and left it sit for a bit to form fit.
You know what they say, you never have a second chance to make a first impression....LOL
Now the only original parts in the valve are the washer and check valve spring.
The Teflon check should last the life of the gun as well as the Delrin seat.
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Is this going to turn out to be the "Million Dollar 317" ;D
If it is I'm glad it's in the right hands to work out the bugs before it goes back on duty. ;D
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Put the gun back together and it held air overnight.
With the smaller blue spacer in the valve it will have more volume and lower velocity.
It will also be easier to pump up to 8.
Final chrony with 7.9 CPHPs:
3 pumps 516 FPS
5 pumps 606 FPS
7 pumps 690 FPS
8 pumps 723 FPS
I like this pump curve.
500, 600, or 700 FPS without pushing the gun too hard.
Stick a fork in it, it's done.
Like sand through an hour glass, so go the guns of our lives.
I really have to say, I'm going to miss this old gun.
It was a fun project........now back to my Crosmans....LOL
Before the curtain closes, one last picture of the tools.
The valve seat in this gun has a 14-28 thread vs the stock 9/32-32 thread so made 2 brass ends for either seat, SS hardware.
The valve nut tool is made from an old Crosman barrel.
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Put the gun back together and it held air overnight.
With the smaller blue spacer in the valve it will have more volume and lower velocity.
It will also be easier to pump up to 8.
Final chrony with 7.9 CPHPs:
3 pumps 516 FPS
5 pumps 606 FPS
7 pumps 690 FPS
8 pumps 723 FPS
I like this pump curve.
500, 600, or 700 FPS without pushing the gun too hard.
Stick a fork in it, it's done.
Like sand through an hour glass, so go the guns of our lives.
I really have to say, I'm going to miss this old gun.
It was a fun project........now back to my Crosmans....LOL
Before the curtain closes, one last picture of the tools.
The valve seat in this gun has a 14-28 thread vs the stock 9/32-32 thread so made 2 brass ends for either seat, SS hardware.
The valve nut tool is made from an old Crosman barrel.
That shot curve does make more sense for this pumper. It will make it more enjoyable to pump up at my age :'( and my grandson when his dad gives him the go ahead to graduated from BB gun to pumper. Hopefully he won't wait till he's out of college ::)
I do like those chrony number Ron. Thank U!
I'm very happy to know that you enjoyed your tinker time with my 317. I was hoping you would.
The timing was just right for the project you wanted to experiment with.
Must be destiny. ;D
Hope you hang on to those tools and get to use one on your next project.
I'm going to get a Yellow Ribbon and Tie It Around The Old Lamp Post. I don't have a Old Oak Tree ;D
Will be waiting for her to come home to Papa. ;D
Don't forget to include your bill for time, labor and parts.
That's the part I'm worried about given how much time and effort you put into this one.
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How rude, crude and socially unacceptable of me to not allow the guest of honor to have a final word.
Where are my manners?....LOL
Should get it in the mail in the A.M.
I'll send you a PM with the TN.
USPS online says expect it Thursday.
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How rude, crude and socially unacceptable of me to not allow the guest of honor to have a final word.
Where are my manners?....LOL
Should get it in the mail in the A.M.
I'll send you a PM with the TN.
USPS online says expect it Thursday.
I know ;D
I was really wondering if all the edict your parents, military and your wife taught you were all but forgotten because ya spending too much time with the guys here on GTA ::)
I'm sure you'll do better the next time.
Look'n forward to talk about the good ole days with my RestoMod 317.
Going to be rather difficult keeping my hands off of 'er but I don't think she'll mind. ;)
Looking froward to more of your RestoMods here on GTA.
Will be and staying in touch.
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Late to this but what a great thread. I read every word and you actually made the process make perfect sense....am just amazed....
Want to take a crack at a Bam B5-10. accurate, rock solid platform, good condition.
kidding...not kidding. ;)
Seriously, great work and posting.
Thx for the read.
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Late to this but what a great thread. I read every word and you actually made the process make perfect sense....am just amazed....
Want to take a crack at a Bam B5-10. accurate, rock solid platform, good condition.
kidding...not kidding. ;)
Seriously, great work and posting.
Thx for the read.
Thanks, seems folks take a more traditional approach to these guns leaving them mostly stock.
I also have a Benjamin 312 that I need to upgrade, maybe later this winter.
The next project will probably be a 766-M16 assault carbine.
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Thanks, seems folks take a more traditional approach to these guns leaving them mostly stock.
I'm happy to report that I/we didn't go the more traditional approach.
Performance with 4-5 pumps is more than adequate for basement plinking.
It's in the safe (yep with 2 pumps) building up my anticipation of using it after the holidays when the long hard days of winter here in Maine can be brutal.
Hope all is well!
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Late to this but what a great thread. I read every word and you actually made the process make perfect sense....am just amazed....
Want to take a crack at a Bam B5-10. accurate, rock solid platform, good condition.
kidding...not kidding. ;)
Seriously, great work and posting.
Thx for the read.
Thanks, seems folks take a more traditional approach to these guns leaving them mostly stock.
I also have a Benjamin 312 that I need to upgrade, maybe later this winter.
The next project will probably be a 766-M16 assault carbine.
Thanks, seems folks take a more traditional approach to these guns leaving them mostly stock.
I also have a Benjamin 312 that I need to upgrade, maybe later this winter.
The next project will probably be a 766-M16 assault carbine.
[/quote]
I would be curious to see the results of your 312 when your finished. I have a 312 (12 pumper)
that is clocking at 644.3 fps max using 14.3 gr.Crosman Premeir hunting pellets. Keep us posted on it! BTW, beautiful job on that 317! 8) dave
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"766-M16 assault carbine"
Hope I come across it. It's amazing what you and the other real builders do transforming production run guns into custom shooters. Fun to watch in awe.