XS60C PCP Repeater project

[rokitman60]

Whatever way you do it...hard or easy, it ALWAYS seems to lead to something else, doesn't it?

[stalwart]

That's a great offer Eric.  Even when doing things the hard way I may not realize it at the time but later on do find I have learned or pick up something on doing the next hard way project.
As for the trigger mod I think its worth doing no matter which method its done.  JMO

-

Whatever way you do it...hard or easy, it ALWAYS seems to lead to something else, doesn't it?

Not an XS trigger, it's from the QB, but they are alike in function as two peas in a pod....

Note the spring loaded plunger in place of the overtravel screw.... That, plus a lighter trigger spring (which provides the first stage) gives a true 2-stage trigger.... They are a commercial part that fits in a 6-32 threaded hole....

Bob

Nearly every day, I get solid proof (like this) that I am hanging with the right crew. 

The Fusion will be here Tuesday. In anticipation, I've been pondering pics... and this one brings up something: It appears the stock is deep and wide enough to take a much larger tube (but, not enough to go double). It looks like a 1" ID tube will fit without leaving a paper thin forearm.

What are the specs (and the threads) on an MRod tube?

[nodak]

I have a Fusion we could play with.

[stalwart]

I have a Fusion we could play with.

Around here, those are what's known as "famous last words"! LOL... stick around, it won't get boring...

If you would, I'd love a pic of the inside of the forearm, from above?

[stalwart]

Mrod tubes are 1" ID, and use 1 1/8" x 20TPI threads, according to the net.

What would be the material choices on this, for 3K?

[rsterne]

The MRod tube is 1.25" OD x 0.095" wall, so that is 1.050" ID.... no idea on the threads....

Bob

[stalwart]

Big Bore Bart saved the day... a long time ago.  http://www.gatewaytoairguns.org/GTA/index.php?topic=68971.0

Are we stuck using steel for the tubes? What would the OD be on any alternatives (it appears we are close to max OD for the stock)?

[stalwart]

Would using a tiny gas ram, instead of a striker spring, reduce or eliminate bounce?

[Kailua]

I may be picturing the idea of a gas ram wrong.  But wouldn't a gas ram hold the valve open?

[QVTom]

Yes and no.  It would be a balance of mass of the ram piston and force.  The other possibility is to use a gas ram to power a lightweight striker with some negative preload.

Tom

[stalwart]

http://www.mcmaster.com/#9417k1/=xxt6u3

With a 1" stroke, and 26mm available (with my mods) within the tailless design, I would be able to leave negative preload. These have a 4mm shaft, and it would only go into the striker a few mm, so a lot of striker weight would be left where the spring would normally go.

There are a lot of choices in force... how would I figure out which is best?

[stalwart]

I'm thinking the way to set this up for tuning would be to either make a striker with adjustable weight (and min neg preload)... or make a solid one, use an adjustment of the gas spring's location, and fire the striker over the tunable gap. Am I lost in space here?

Bob answered this long ago, but I can't figure out where... what is the max force a standard bolt handle can manage comfortably? How about a separate lever with a fat handle?

[stalwart]

Another possibility might be to make a striker with an adjustable stroke. Piece of cake to make... make the catch a threaded (and locked) ring. A striker set up for this would also be easy to make weights for.

[rsterne]

It depends on what you are building the striker for, high power, or lots of shots at low power.... If you are looking for lots of FPE, I would leave the stroke at maximum, use the heaviest hammer you can, the heaviest spring you can cock, with a bit of negative preload.... The same would apply to a gas ram, the difference being that the first part of the cocking stroke would be heavier, and the ram less likely to be recompressed by the hammer flying back.... Since the force on the hammer is more constant, for the same average force, you can reduce the maximum cocking effort, which seems like a good idea.... You would tune the preload by varying the gap between the hammer and the ram, meaning that for a given cocking stroke the ram would be compressed less as you increase the gap.... If you can find the right ram, it would seem to be an excellent thing to try, my Grizzly could use one.... I need something with about a 10 lb. force uncocked and at least 1" of travel.... My current setup uses a 24 lb/in spring with 1/8" negative preload and a 1" stroke, so it is compressed 7/8" to a maximum force of 20 lb., and an average force of 8 lb. over the hammer travel, producing 0.66 FPE of energy in the hammer.... A quick check of N-Forcer gam rams shows that to get a 1" stroke the overall length is 3.6" (2.6" compressed), and they are 19mm (3/4" ) OD....

Bob

[stalwart]

Thank you, Bob. As usual, you seem to be able to make sense of the stuff ricocheting around in my cranium (not a common skill). We're gonna run this thing down, and eat it alive.

The Fusion is here. I'm tickled. I really like the stock! It's hollowed out as much as possible (stash!), and the grip is solid. Those finger grooves are OK for my hand, but could be (and might be) taken off, or reduced, quite easily.

The forearm is narrower than I perceived it might be, by looking at the pic. 1.25 OD will be a tight fit, if it goes at all.

The fit and finish are quite good. IMO, the gun is worth the price.

I took it apart without charging and firing it (it's an illness), and dropped in one of my G1 trigger groups (the stocker is, not surprisingly, horrid). GTG.

When time permits, I'll light it up, and report on the moderator. Then I'll put the barrel and moderator up for sale... it's going bigger bore.

[rokitman60]

Something WICKED this way comes...

[stalwart]

Something WICKED this way comes...

Indeed.

[stalwart]

It's pretty clear why G2 trigger jobs aren't as nice as G1s. The auto safety actuator requires a slot through the sear area, which means that 3X the overlap (creep) is needed to achieve the same sear contact area.

Fitting G1 sear parts eliminates the auto function, and give it as crisp a trigger as this design allows (pretty nice, actually... plenty of sear area to work with).

I smoothed the seams on the plastic housing of the Fusion. It's good plastic, and looks a LOT better with the flash gone. All set now.

[stalwart]

Finally shot the Fusion...

The gun is louder than the ad shows (silent there) and gives off no red ripples...lol. 



It goes a long way toward eliminating the sharp snap, though. If someone doesn't buy the barrel/moderator, I'm thinking of cutting it down into a custom P17 set up. At half the speed, it might really quiet the pistol.

[RHytonen]

... what is the max force a standard bolt handle can manage comfortably? How about a separate lever with a fat handle?

and I'm trying to answer it a different way ( a double-ended 8mm through-pin each, for bolt and for hammer; external cocking plates for both sides.) I think the main problem of cocking effort is galling partly due to pulling the bolt from only one side.
I'm sure your slick coating will also help- on bolt, hammer, pins and receiver sliding slots. (Tube slots can be oversized, NP.) I might even want it on the inner surface of the external sliding plates.

- will have dimensioned receiver pics for you this month.
Trying to make clean drawings disturbs the design flow.
I made some (messy!) progress on the bolt retractor for the windowsill cannon today.

Still have to look up the Grizzly cocking and bolt throws to get a preliminary plate design dimensioned.
(The plates are the easy part compared to the retractor
2 Mags coming from Lloyd this week to get the loading throw nailed down.
You're making me SO glad I insisted on the Gen1 trigger for my Gen2.
Need another pack though, for the other receiver.

Rod