Home Stretch Now!

[Doc Sharptail]

The more I think about it, the more sense having a small regulated bottle on the gun makes. An "a-ha" moment for me, yes. I'm betting there's a few around here wondering when I would get to it

Is there a bottle around small enough for me to manage with the Hill pump?

For my current set-up, a reverse tank block is gonna be the most practical way...

There's no big rush on this yet- I'm having a great time with the 3K tube. But I fear it will become one of those hard to scratch itches...

I'm thinking it will end up being easier on the gun, especially for the reduced striker spring pre-load, and I'm pretty sure lowering pressure on the gun side will be advantageous some how...

Regards,

Doc Sharptail

[sholo]

I'm betting there's a few around here wondering when I would get to it

LOL...it was only a matter of time, Doc!

A 13 ci bottle reg'd to 1500-1600 psi should work nicely for you. IIRC, it takes me around 255 strokes from my Hill pump to fill from 0 - 3000 psi (85 strokes per 1000 psi +/-). This was using a 30" S/S hose from Eric, but if you are using the shorter fill hose that came with the pump, you can knock a few strokes off that total.

Granted, my '78 is .177, but with a full 3000 psi shooting down to 1500 psi using a 13 ci bottle I am getting anywhere from 108 shots @ 16.7 FPE to 510 shots @ 3 FPE, depending where I set the RVA...

Bob has thee best looking/functional reverse tank block I've seen by far, but for us guys with no lathe (and in my case - the smart's to make such a block) this might be an option for you? http://www.canadianairguns.com/showt...-AR2078A-stock , although the 3K tube is longer than a stock one so it might make it more "nose-heavy" as a result.

Hope this helps somewhat, or at least give you some food for thought! Good luck scratching that itch!

Cheers,
Todd

P.S - Plus, if you running 1500-1600 psi as opposed to 2000 psi (or higher), your factory valve stem seal shouldn't give you any problems. I've had my gun pressurized at 1500 psi for about 1 year now with roughly 3000 shots through it with no problems at all.

[Doc Sharptail]

I'm currently @ 37-42 pumps on the 3K tube: 2400 on the pump gauge-22-2300 in the gun by my calculations.

Depending on how my back feels, and how tired I am, I sometimes take a 5-10 min. break around stroke #20. Not always, though. On a good day for me I can fill the gun non-stop.
By what I'm reading here, I'll probably need 3, maybe 4 rest breaks filling that 13 ci bottle from empty. It should get easier than that, after the initial fill. I don't shoot the gun right down when I'm shooting strings- I'm guessing I refill around the 1300 psi mark- which = around 12-17 pumps or so.

I suppose the only way to find out is to try. Mean-while, I have a bit of pellet work-up to do... haven't had this much fun since discovering the "finer" things.

Wonder what Freud would of made out of perusing this forum?

Regards,

Doc Sharptail

[Doc Sharptail]

Was shooting the gun down tonight, so I could get the breech off. Last shot before empty tube, something goes "toing". It was loud enough to have me thinking hammer spring. Gave the gun a shake and no rattles.

Went ahead and did the t.p. Put the gun back together, and pumped up to 850 psi. Another leak at the breech. Kept ripping bbl o-ring #1, and replacing it. I had been dipping into the wrong o-rings compartment - they were too big/loose, and rolled out of the groove too easily, and ripped themselves on that first edge going into the breech. Finally got the gun to no leaks at 600-850 psi. Back up to 2200 PSI, and I'm back at the lemming leap for strings. I bet it's that hammer spring- not surprising considering all the over/under compression I've been putting it through.

Enough for one night. I'll have at it again tomorrow night...

Regards,

Doc Sharptail

[Doc Sharptail]

Got the top end to where it doesn't leak. Gun now leaks from the valve stem on firing @ 1500 psi and below. I don't have any curve to my strings, either. Top of the string isn't bad- the first ten shots decline about 10 fps for each shot. Over-all velocity is down about 200 fps for the hammer spring pre-load I'm using.

I'm going to have to leave this, until I can get a couple of more replacement valves in. Apparently, 2200-2400 PSI is enough to make the stem seal flow/extrude...

Regards,

Doc Sharptail

[rsterne]

Apparently, 2200-2400 PSI is enough to make the stem seal flow/extrude...

If you're still using the stock QB valve poppet seal, I would think that likely.... It distorts pretty badly at 1600 psi over longer periods of time.... Delrin is required at higher pressures....

Bob

[Doc Sharptail]

Hi Bob:

Yes, I'm still on the factory stem seal. They are not lasting long. Going back through my notes, I got about 180 shots out of the last one.

I'm just wondering if it's the pressure alone that is doing the damage, or firing on pressures around the 2200-2400 mark. 2400 is the highest I've taken it. I note the fill adapter in-shear screw heads slightly pushed against the tube wall... That stem must be really slamming home at 2200. Any thoughts?

I think I'm almost there. If I can't come across either delrin stems, or stem seals, I'll take both pressure and caliber down for this tube. Either way, I won't be leaving a .177 out of my plans...

Regards,

Doc Sharptail

[rsterne]

I would think SeanP could make you a Delrin stem no problem....

Bob

[sholo]

If I can't come across either delrin stems, or stem seals, I'll take both pressure and caliber down for this tube.

Eric now has them listed on his site: http://scopesandammo.com/storefront/...2-rifles-p-886


Todd

[Doc Sharptail]

Great news. I'll be putting an order in this coming friday.

Regards,

Doc Sharptail