Excitement

[Doc Sharptail]

Just to see if it holds overnight. Dry fired it once, and it sounds like a single-six going off in here.

From the bit of playing around I've been doing, pressure seems to drop by 100-200 PSI by using the bleed screw.

The tube is easy to pump up to what's shown in the photo. I'm one of those 6 ft 140 lb bean-poles with a bad back to boot, but the pump is easily with-in my abilities on a smaller volume like the hpa tube.

I likely won't get a whack at shooting this until late Monday night. Can't wait!

The valve actually touches the support ring at rear. That's good to know. There's three screws there holding that valve in place. They're not head-in-shear, but thick enough for my liking...

Regards,

Doc Sharptail

[sholo]

Looks great with the HPA tube, Doc!

How many pumps to fill? I'm guessing (?) not enough for the pump tube/seals to heat up much - always a good thing!

Must be reassuring to know that even in your sick, weakened state at the moment (and yes, I realize that didn't come out right...but you know what I mean!) that you still find it easy to pump. It can and will only get better/easier!

Now you will have to make some sort of RVA to fine tune and maximize your shot count/power level. The tinkering never seems to end, huh?


Todd

[Doc Sharptail]

I think it was about 37 pumps from nothing in the gun. The spring pictured is a lot lighter than the factory valve spring. The Hill pump seems most effective with moderate full length up and down strokes. I can feel it moving a slight amount of air on the up stroke. Hurrying: eg.- short up stroke and/or forcing the pump beyond a moderate operation speed- seems to be what causes the pump to "warm". I don't really have to lean on it hard to get it to move air.

A few thoughts. I'd like to get a gauge onto this tube- the sooner ,the better. Any ideas on how, and where, it should go?

I'd like to have an RVA, or 3 here. I think this is probably something I'm going to have to buy.

England is not the best place to be packaging dessicated silica gel beads. What came out of the sealed envelope was just about full "indicator brown", instead of white. I think a cost effective remedy for me would be the king-sized jar of Super Dri-Aid, with it's 100% re-usable beads. Just zap them at low defrost in the mike until the indicator beads return to full blue.

How do you guys transport and store your pumps? That "erectile" pump hose seems to be getting in the way a lot. I don't really want to be bending it all the time. Is there a flex hose available that can handle these pressures?

Shooting time can't get here quickly enough...

Regards,

Doc Sharptail

[SeanMP]

Ya it does look like something is sticking. I was almost thinking hammer or rolling sear.

The airgun elf is delivering the delrin stems to a certain little birdie tomorrow. Fastenal was kind enough to ship a whole bundle of thoroughly rusted drill rod which had to be sent back and then the wait for the original manufacturer to deliver unrusted material.

The RVA's for QB's are as you know a real head scratcher. Mainly because everything that anyone has done including the one Todd and I made up require the end user to drill an accurate hole through the breech. The only solution I can come up with is a supplied end plug the has an adjustment hole at a slight angle so that the original screw configuration can stay the same.

Would that appeal to anyone?

[Doc Sharptail]

Would that appeal to anyone?

I'd be interested in the delrin units for sure. As for the RVA, the tube I have here is a bit thicker walled than a stock factory tube~ in fact, a stock factory tube cap won't fit it. I don't have a lathe here- nothing to turn down a cap enough to fit. I have a brass tube cap from scopesandammo that fits perfectly...

Regards,

Doc Sharptail

[Doc Sharptail]

AHA! It's most likely the hammer binding inside the tube. Just occurred to me now, thinking about tight fitting end caps... I had to do some serious de-burring on the back of the hammer, just to get it to fit inside the tube...

Regards,

Doc Sharptail

[rsterne]

What is your valve stem seal made of?.... If it's the stock soft material, it was likely stuck on the seat slightly on the first shot.... Even Delrin can show a slighly low velocity on the first shot, but only 20ish fps or so....The 6th shot, I have no idea..... How much volume do you have in the reservoir?....

Bob

[Doc Sharptail]

Bob-

The volume escapes me right now. I did know it when I ordered the tube in January last year- it was one of the selling points for me. Spent the last hour searching my machine for the volume, and am drawing a blank. Maybe Eric remembers?

At any rate, I'm hoping to tear the gun down a bit tonight after work, if I've got enough steam left. May end up getting the volume the old school way with measuring tape and caliper.

It's a completely stock valve stem and seal. I'm more than a bit curious as to what's happening inside that valve, and also want to polish up the stem shaft a bit. It could use it.
Also considering reducing the air flow a bit- I've got another valve here to work with. ~Pretty sure the upper 9's are a bit faster than what the Predators were designed for, anyways. From what I've read around, mid 8's seems to be the sweet spot accuracy wise for them.

Regards,

Doc Sharptail

[rsterne]

Doc, on your 2000 psi string you are missing most (if not all) of the first half of the shot string.... I wouldn't be surprised to see you get nearly 20 shots with a higher pressure fill.... You want your first shot to be about 4% below the peak, which if it doesn't go much over 753 fps (the fastest you have so far) would be ~723 fps.... The first half of the string is more efficient than the downhill side, so you could easily double your shot count by filling to 2200-2400 psi....

Bob

[Doc Sharptail]

I shot it tonight, and I'm a bit further ahead then I thought I would be. More on that in a bit.

As near as I can tell, the tube is holding air well. Only way to be certain sure is to get a gauge on the tube.

The gun is very loud. I've got a bit of a headache from the session I had tonight.

I was worried about the transfer port not sealing properly- I don't know why. Crosmanitis maybe?

I got sort of a couple of strings out of it tonight. Flat strings? Heck, no. Nosedives.

I had better clear up what's been done, and not, before going any further.

The valve spring is quite a bit lighter than the original factory spring. I have no pre-load of any kind on the hammer spring. I cut flow holes on the front half of the valve. They are not that big, and extend about 1/2" up the side of the valve, and are 1/4" wide.

First "string" @ 1500 PSI with the 16 gr. Predator:

1.) 689.7
2.) 685.4
3.) 676.5
4.) 667.3
5.) 662.7
6.) 652.7
7.) 646.5

I didn't like where that was headed, so I stopped, and re-filled the tube to 1600 PSI.

1.) 746.5
2.) 739.9
3.) 735.4
4.) 731.6
5.) 720.6
6.) 715.8
7.) 706.3

40 fps over 7 shots ain't that bad- not for the purposes I'll be putting the gun up to this fall. Wouldn't mind improving on those strings though. It doesn't sound like it's hammer bouncing. Thoughts, comments, anyone?

There was much ado about finding how the gun balanced, and shouldered. There was even a shot or twelve plinking at that soda can pull-ring tab rivet...

...a quite enjoyable session. It's been a while, almost a week!

Now the tweaking begins....

Regards,

Doc Sharptail