XS60C PCP Repeater project

[QVTom]

Just ramblings.  Use the smallest piston possible that won't mushroom in use and doesn't require too much pressure.  3/16 would need ~715 psi for 20lbs of force.

[stalwart]

Just rambling, huh? Hmmm.... do you tend to "ramble" more after a couple drinks? I could set that up. 

On it.

[stalwart]

As I wait for the P.O. to open, thought I'd toss this in:

The GRS, made in house, will be able to do any length stroke, and have a piston of any length. This means that the adjustability can be used in anything from mild to wild, and that it can be used with anything from a slug style striker to a stocker.

I'm very interested in learning what it can do inside 13mm of stroke (stock 60). In a thru-tube, the stroke can be set to any length by spacing the caps the proper distance apart, and making a piston that ends a couple mm before it touches the striker, at rest. If target shooting is your thing, the consistency of this setup will reap good ESs.

Tick... tock...

[stalwart]

Guys, I have come to the conclusion that I can no longer sell the small stuff (caps, strikers, etc) as customs. The ratio of correspondence to actual sales is coming very close to making these parts an exercise in charity.

This does not apply to established customers, who already know what is available and what they need.

From now on, if it isn't in the Hobbyist's Gate... or, in the upcoming "In Stock" section of my site... it isn't available at the time.

Also, any prices I have quoted to date are good until August 1.

Thank you for your understanding!

[stalwart]

It's here. I have been looking for this since before it was ever made. It's a rare beast... 2 in the world, and Tom Costan (QVTom) gave me one of them. Can you believe that??

It's a Slayer mag, made before the finalized design went into production. It varies a tiny bit from the production piece, in ways that mean nothing to this project.

I can honestly say that my search for a mag for this project has lead me to trying to get a good look at every mag available in the US... at least until very recently. I have MANY hours into that search... it's over, and I'm as happy as I get, about that!

It's a thing of beauty. Perfectly made. I intend to do it justice, with everyone watching.

When I saw the Slayer, I immediately thought about trying to get one... and when Tom told me that there weren't going to be any production spares for a while, I figured I'd just be patient, and persistent. When I told him that it was for my personal project, he suggested that I would be fine with this one, if it fit. He sent a drawing to make sure I could set it up, and (as you will all see), it will be a piece of cake.

*

Tom, I don't know what else to say... I can't thank you enough. We are gonna have a TON of fun building the baddest Fusion on the planet, and it wouldn't be possible without your (un-returnable, unless you need a kidney?) generosity and support. Only thing I can think of is to do us all proud here. I can't tell you how tickled I am right now...

BTW, guys... I have owned watches with tolerances sloppier than those of the air fitting Tom sent with this. Impressive.

[stalwart]

What size screws should I use to hold the end caps, so that the fronts fail reliably at about 2K... and the rears never do? I'd like to use the min number of fasteners.

[rsterne]

Are you installing end caps at both ends of the piston?.... the front one the piston slides through and the rear one contains a male Foster?.... What is the ID of the tube you are installing the plugs in, the main tube (0.745") ?....

Bob

[stalwart]

Yup, yup, and the tube is the main tube, extended through the back.

[rsterne]

For the front screws, you might try two 6-32 cheesy quality screws.... At 2000 psi, the force on the front plug is 872 lb.f.... If the screws are Grade 2 (74K psi tensile), derated to 60% of that in shear (44K) they should have a shear strength of about 350 lb.f. each.... so "in theory" should fail at about 1600 psi.... Figuring out how to make them fail so that they don't damage the plug or the tube, and so that they, and the plug can be removed after failure, might be a bit tougher.... How about a 3/32" brass shear pin, that should fail at about 400 lb.f., or about 900 psi?.... but would give you a working pressure of only 300....

The rear screws should have a 3:1 safety margin on whatever pressure you could possibly put in there.... Any chance of somebody hooking a 4500 psi tank to the wrong Foster?.... How strong do you want to go?.... You know what you need for 3000-3500 psi, three low profile, high tensile 10-32's with the head in a pocket in the tube.... same as the valve....

Bob

[stalwart]

I'll be running (3) 1/4-28 screws as you suggested, in the valve/block combo for 4.5K use.

Isn't that overkill for the GRS, as the total pressure is meaningless if the F always fails before the R?

[rsterne]

Agreed.... You probably should have 3 times the strength in the rear, so that the working pressure at the back is the failure point at the front.... Either three 8-32 with the heads in pockets, like a Disco valve, or two 10-32s, will give you 3.0:1 safety margin at 2000 psi if the screws are 120K Tensile (Grade 5 equivalent)....

Bob

[stalwart]

That makes good sense. Build the R as if it's real job is to blow the F out... every day. I like that.

I got a pic of the Fusion before the mauling began. It's now completely apart. It's going to be a long time before it's 1 piece again.

[RHytonen]

I got a chance today to make a limited travel spring guide for the Grizzly.... It looks like this....



The 7/32" OD spring guide is threaded both ends to 10-32.... On the front, the single nut is loctited and peened in place and turned down to 0.36" OD (same as the spring) to be a loose fit in the 3/8" hole in the hammer, and tapered to match the bottom of the drilled hole.... The space between that and the rear nuts is the length of the spring plus RVA screw, minus just over 1/2", which results in 7 lbs. of preload in the spring as installed in the photo above....

The original plan was to use a 3" long, 11 lb/in. spring, with 5 lbs. preload and 15 lbs. force when cocked, but to get that to work I had to run it right up until it touched the hammer.... I ended up with a 13 lb/in. spring, with 7 lbs. of preload....

Bob

Is that a standard McMaster spring, or did you have to make it?

-Rod

[stalwart]

Just a quick pic to show everyone why seeing Tom's drawings got me so enthused.

It shows that the bolt slot is just long enough to clear the barrel seal and the mag. If the horizontal slot is extended far enough to push the bullet past the port, the bolt can be probe-less for the best flow.

[RHytonen]

Just a quick pic to show everyone why seeing Tom's drawings got me so enthused.

It shows that the bolt slot is just long enough to clear the barrel seal and the mag. If the horizontal slot is extended far enough to push the bullet past the port, the bolt can be probe-less for the best flow.

-Rod

[rsterne]

That is a Century Spring, 3" long x 0.36" OD x 0.049" wire.... with a rate of 13 lb/in.... if my notes are correct # 71215....

Bob

[RHytonen]

That is a Century Spring, 3" long x 0.36" OD x 0.049" wire.... with a rate of 13 lb/in.... if my notes are correct # 71215....

Bob

They are - and THANKS!

BTW: aircraftspruceDotcom/catalog/hapages/an3.php

OR: (also ACS -) NAS464P3A48     
(see gen-aircraft-hardwareDotcom/images/pdf/nashhb.pdf  for NAS specs)

OR (for longer thread) ..? NAS66P03A48C  (10-32, 3" chrome 'grip')
Then all you have to do is turn down the head... just sayin', if stalwart's mass producing..

-Rod

[stalwart]

The stripped stock weighs 785grams, about 100 less than the wood 60 stocks.

There's room in the forearm for quite a bit... but, not a double.

[stalwart]

Guys, I'm authorized to share the story of the very special custom bullet shown in the mag pic... by it's designer, manufacturer, and only tester. John Cripe (johninthecamper... http://pelletgarden.com/ ) is the man behind the world's first Boat Tail Wadcutter.

He invented it in seconds. By inserting a Slayer mag in backwards (this kind of thing takes real genius!). As a result of it's poor feeding in the new gun (a last round partial feed resulting in a partial investigative teardown of the gun, rather than forcing it in) , the manufacturer of the Slayer came up with a good way to prevent more innovation of this kind. My mag was made before the change, and is one of (it turns out) 5 ever made capable of allowing this kind of out of the box research.

It's gonna be worth a LOT of money some day!

 

[stalwart]

John just contacted me, and pointed out something I didn't realize:

He has a number of these bullets designed to give the shooter "field ready options". They're easy to use... just before loading, turn the mag or gun 180*. Clean holes in paper... no extra charge.

These guys on GTA... they're always thinking.

Seriously... this points out something important. The value of (end user) field testing cannot be overstated. Tom, having seen that mag in his head long before it ever saw 3D, isn't very likely to put it in backwards. John, faced with multiple jack rabbits, carrying a gun he was unfamiliar with... did what any of us might in a hurry... and improved the breed before Tom had to learn the hard way (we've all had that customer).