Canadian Airgun Forum

Nice! So you must be getting a little higher velocity now at 10 pumps if you are dumping it all. How's the velocity at 15 now turned in? [SMILING FACE WITH SMILING EYES]


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Is the trigger a lot tougher turned in 4 turns?

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I was pretty well at coil bound before the RVA installation. It put quite a load on the sear- very noticeable at trigger pull. No extra pull weight at 4 turns in, which is making me a happy camper. I won't get any more juice out of the gun with that limited valve volume. She tops out at mid to upper 6's until I get a bigger valve into her. Haven't decided yet if power is what I want- I've got a couple of p.c.p's should the need for velocity arise. Still pumped over target velocities out of 3 cranks on the handle with a cup piston...

-D.S.

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"Ain't no half-way"
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That's great! You had mentioned you kind of like that 500fps range. 3 pumps is sure nice! I suppose with a bigger valve you might be able to get 2 500fps shots with 10 pumps if you adjust things a bit[WHITE SMILING FACE]️

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Got the 13-XX valve into the gun tonight, and cut the hole in the tube for the front grip screw. Everything appears to work as it should, and it still retains air at ten pumps with the RVA out of the end cap. I didn't get to clock it. It wants to leak at the transfer port. I have had trouble with this valve leaking at the port before. I'll mill a recessed flat over the port hole, and go with a poly tube port. The factory flat on the valve was mis-cut on an angle.

Personally, I don't really care for poly porting, because they need to be replaced fairly often. The poly has to crush slightly for an efficient seal. Sort of a pain if the gun is taken apart on a regular basis for testing...

Glad to have the front grip screw done. The gun is much easier to work on...

-D.S.

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"Ain't no half-way"
-S.R.V.

Will be interesting to see how it performs with the flat top and new valve!
I almost have my 760 tube in working order, just need to tap the 4-40 screw hole in the breech. Going to buy a 18" barrel for it and steel breech, the barrel isn't in stock at the moment. Already tapped the hole out the side of the valve, but still need to flat top it for my new flat top piston once it's ready, from innovative machining. Looking forward to trying it out! Sure would be nice to have that 2100 pump setup though, would make pumping it up a lot easier!
This 760 pump tube came terrible looking, bluing was all worn and discoloured. I sanded it all off, will have to do something with it, either polish it or reblue.


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Got the transfer port leak eliminated.

Low end performance is about what I was expecting with the decrease in swept volume, and increase in valve volume.
3 pumps averages 430.6 fps over ten shots. Extreme spread is very good here at 4.9 fps. 5 pumps yields a little closer to my hoped for target velocity at mid 550's. I' m very pleased with that. E. S.'s are still good at 8.3 fps over ten shots.

Biggest surprise was 10 pumps with no RVA load on the hammer spring. Not 2, but 3 (!!!) shots out of 10 pumps.

I think to be fair, I should really start another thread on this. Pretty excited about this....

-D.S.

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"Ain't no half-way"
-S.R.V.

Awesome! Definitely, you should write the whole thing up in a thread! Very exciting! What kind of fps are you getting in those three shots?

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Well, having some trouble tuning my 760/1322 in, using the same rva and spring but where I was getting 50 good shots with the 1322, I'm getting like 10 shots at around 500fps and it's really loud like way too much air is escaping. This valve had the detuned hole in the back and I had put jb weld in from the back side. Kinda wondering if I blew it out. Will have to check that by taking hammer out. If it's not that, not sure what the difference could be. Kinda disappointing so far!

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Yep, that was the problem, at least one problem, detuning hole had blown out the jbweld. Guess I need to wash the valve first and maybe try plug both sides of the hole this time. Pays to do things right the first time!

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Tapped and put a screw in the hole, and cut the head off. hopefully that will fix things up, thanks to Doc Sharptail for the suggestion.

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Made an ssg for my 760/1322, using a 3/16 rod and capped nut on the back going through a 3/8" bolt. I put a 2240 spring on it to tame the power. I also have a new flat top piston from Ron at innovativemachining.ca which is working well, and Derek Vinyard recently got back to me and offered to send me a delrin one, which I paid $15 shipped for. I had already got the nice brass one from Ron, but couldn't resist such a great deal. Tried it out, giving it a break every 50 pumps to cool it, and it is working fine, seems like equivalent pumps as the brass one, which in turn so far seem about equivalent to my stock non flat top piston that I had stuffed with rod and jbweld. I'm sure these will be more durable though under high pressure.
Using my 12g adapter I was able to get a curved string starting at 1150psi, 492, 516, 513, 511, 531, 537, 534, 513, 486. 9 shots. The one picture with the ssg has my 88g tank with the foster valve in the end, which I had planned to retire but am still using at lower pressure [emoji4].

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Here is the delrin piston, brass piston and my poorly jbweld and rod stock piston

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Here is a new experiment with a 16g cartridge, with a 1322 tube, so it'll be set under 500fps. Will have to start a new thread for it, lol

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Here's the gun with the 12 gram adapter on it, which I've already posted various times. Either this or the 16g cartridge will probably be the most practical I think as the big tank just takes way to many pumps! Another with the 16g as well.

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