Retained air-2100-13-XX conversion

[rsterne]

The flat on the bottom of the valve allows it to move back.... that means you have to move back the hole for the transfer port as well....

The valve is shortened on the front, the O-ring groove is moved back behind the original hole for the trigger screw.... The valve was machined off flat level with the back of that hole.... These changes combine to move the front of the valve back quite a long ways, which then results in increased swept volume for the pump.... Not quite as much as on a 2100/2200, but 50% more than a 13XX/2289....

There is a additional tapped hole in the bottom of the tube, just in front of the stake that locates the valve.... to provide additional setscrew to secure the valve since it no longer has the front trigger screw holding it.... Here are the sketches of what I did....











Bob

[Doc Sharptail]

I'm pretty sure that flat top valve Bob has pictured there has a shorter front end on it, looking at mine anyway looks short. I guess that wouldn't affect the port but moving it back with that notch in the back of the valve would make it necessary to drill another port hole wouldn't it?
I should keep my comments to myself, just end up showing how ignorant I am, lol.

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Not at all. Any and all commentary is welcome- it's how I did most of my learning. You appear to be a bit ahead of the curve already- just based on the work we've seen here so far.

I'm already looking forward to starting on that 2200, and this one will be a bit different again.

-D.S

[wesb2007]

Thanks, I appreciate it, you've very helpful and I love these projects you and Bob have done and are doing. Would like to try that 2100 pumper project myself sometime, first I have to finish the ones I'm already doing lol. [SMILING FACE WITH SMILING EYES]

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[Doc Sharptail]

Those drawings are the cats eye, Bob.

They sure help to visualize your always informed discussions.

Thanks for posting them up- much appreciated.

-D.S

[Doc Sharptail]

Got a few things done with the build tonight. Finally got that 4 X 40 screw for the breech hole turned down, shortened the head, and drilled and tapped her in. Biggest reason for that was the Daisy's and R-10's kept falling into that machined hole.

Took the adjuster nut off the RVA bolt, and no retained air at 15 pumps now. No chance to clock her- I ran out of time.
Hopefully tomorrow, a decently long chrony session...

I got pix on the phone, but have to figure how to tap into home Wi-Fi before I can post...

-D.S

[Doc Sharptail]

Things have improved velocity wise with the adjuster nut off of the RVA bolt. I gained almost 48 fps at ten pumps for an average of 747.9 fps.

Top end has stretched quite a bit- 829.8 fps at 15 pumps.
20 pumps yields 862.9 fps.

With the RVA set that way, it's just half a thin hair off complete coil bind. In all practicality, there isn't much sense in pushing the gun that hard. I think I want to back off on the RVA a bit- upper 790's will be fine until I can find some way of relieving that heavy stress on the fire control system.

Considering making another RVA for it- this one about 1/4" to 1/2" deeper. There are some different hammer springs for me to try here. If I can get a longer spring behind the hammer, it may take some of the load off the sear and bolt handle....

-D.S

[wesb2007]

That's some great numbers! Even at 10 pumps it's really getting that pellet moving!

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[sholo]

Hiya Doc,

Been quite awhile, but I'm finally back. Been reading furiously the last couple days trying to catch up on everything.

I like your build so far & you’re getting some good numbers to boot…nicely done!

until I can find some way of relieving that heavy stress on the fire control system.

I know they are a bit pricey, but maybe(?) look into getting a Prod trigger group for your build if possible. With its drop-sear design you could install as heavy a hammer spring as you need/want without affecting trigger pull….mind you, it won’t help with cocking force on bolt though. Just a thought…

I know Eric @ ScopesAndAmmo was selling them for awhile, not sure if he still has them or not.

[rsterne]

If you use a PRod trigger group, you will need a hammer that is straight on the bottom (no waist) or you will have to pull the trigger to cock the gun....

Bob

[Doc Sharptail]

Hi guys! Finally here on computer!

Nice seein you around Sholo. Its been quite a while....

I have a P-rod grip frame on a 13-77, with a non-waisted hammer. I will get to that once hammer spring tension is lightened a little. the 13-XX trigger group will be fine for test purposes.

once I get this lap top figured out, will get some build pix up. Too technically under developed to figure how to do it from phone- besides, the Nikon takes better pix.

-D.S.

[wesb2007]

That'll be great! Looking forward to some pictures

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[Doc Sharptail]

Man, am I ever rusty at this.
This first one is a phone image, and shows where I ended up locating the rear end cap.

I'll get some more up off the Nikon in a bit....

I'm doing really nice at 4 pumps and no hammer spring pre-load- avg 564.8 over 10 shots with an extreme spread of just 2.3 fps. Gun and pellet appear to be very happy there...



Complete (for now) rifle. I kind of liked the old A/M cover over the pump arm pivot- so I made a bushing for it to accept a 7/16" bbl....

-D.S.

[wesb2007]

Looks great! I'm envious of your four pump fps! That's awesome!

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[wesb2007]

That rva worked out great with the longer back end on the tube

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[Doc Sharptail]

There's the flat top piston. It's an oldster from Crusty B's. Anyone remember those halcyon days?

Still going strong, even after burning it trying to do 90 pumps at a time Fortunately there was enough delrin there for me to turn the burnt face off...

I had tried with a single section of 1/4" X 20 rod, but it was too long and was bending in the tube around pump number 6. The long union nut took all the flex out of the piston rod....

- D.S.