Author Topic: XS60C PCP Repeater project (Read 456059 times))

rsterne · « **Reply #800 on:** February 02, 2015, 12:13:42 AM »

They are made by Crosman, and snap into place the same way as the magazine.... I have a modified .25 cal tray for my .30 cal Disco Double, works just fine.... Only problem is, they are nearly as expensive as a mag....

Bob

stalwart · « **Reply #801 on:** February 02, 2015, 07:58:39 AM »

Got some time in on the Cothran valved rig. Cut the bolt's slot as far forward as possible, cut the receiver's pin and bolt handle slots as long as would fit. Got 36mm of bolt travel. The poppet stem protrudes 4.35mm, and I'll find out what we lose rolling the sear into place, when I get that set up. We'll get somewhere around 28mm... stock was 13mm (IIRC). This little thing is gonna be nasty.

rsterne · « **Reply #802 on:** February 02, 2015, 12:45:21 PM »

Since I have to make a new hammer, I figure I may as well go for broke and extend the bolt slot (and the pin slot) to the rear as well.... 36mm looks right.... I'll make the hammer so that it touches the cocking block when forward and the pin just misses the bolt lug.... and the rear of the hammer just touches the new adjusting block when the bolt is at the back of the slot.... Then I'll machine the sear slot so that the sear resets with about 1mm of bolt travel left under load and see how much effective stroke we can get.... I figure about 27mm with 5mm of valve lift, so we are looking at the same numbers, which is comforting.... In reality, an inch of travel (25mm) is pleanty for the Grizzly as I can get the hammer well over 100 grams (stock is 48).... That works out to double the energy and 4 times the momentum in the hammer....

Bob

rsterne · « **Reply #803 on:** February 03, 2015, 02:24:55 AM »

I was away part of the day today, so I only got the new hammer spring preload adjuster done....

The casting that came with my gun was pretty much useless.... It was drilled in the wrong places, and it was machined crooked and the adjusting screw hit the hammer instead of entering into it.... I decided to completely change the design and fabricate one out of aluminum bar stock.... The boss is round, and a proper fit in the back of the receiver, and mounts with the two original screws.... It has a lug on the back the same length as the original, drilled and tapped 5mm to accept the original mounting screws for the rear of the trigger and the rear stock mount.... However, it is drilled and tapped 7/16"-20 NF, so that if the adjusting screw is removed you can swap out the hammer spring without having to completely pull apart the back of the gun.... The adjusting screw is made from a 1.5" long bolt which I softened by heating to cherry red and allowing to cool slowly.... Grade 8 bolts are very hard to machine, especially to drill, and I drilled the bolt to allow a piece of 7/32" diameter drill rod to slide easily through it to act as a full length spring guide, a design that I really like and use on all my builds now.... That rod will have a head on the front which will be captured between the spring and the hammer, and travel with the hammer, adding weight.... Since it can stick out the back, I can slide on an O-ring (shown) which will give me a way to directly measure valve lift, to insure that the hammer isn't impacting the backing block when the gun is properly tuned.... The original head of the bolt was turned down to 7/16", and then machined square to accept a 5/16" wrench for adjusting it.... To prevent the screw from self-adjusting, there is a 6-32 set screw pressing a brass pin against the side of the adjuster to act as a brake.... You can see it in the flange that sits against the back of the receiver.... I have a total of well over an inch of adjustment, plenty for the new hammer spring, which is 3" long made from 0.051" wire.... you can see it in the photo.... Tomorrow I plan on making the new hammer....

Bob

stalwart · « **Reply #804 on:** February 03, 2015, 03:27:28 AM »

Elegant.

I really like the ability to change springs with ease. These guns have a lot of potential, and anything that makes tuning easier is going to pay for itself.

stalwart · « **Reply #805 on:** February 03, 2015, 01:37:44 PM »

Here's a tip for getting rid of those extra holes:

JB high temp epoxy putty. After about an hour it can be filed and sanded smooth. It gets rock hard overnight. It can be painted... and as it is high temp, I am going for powder coating.

Those holes bug me. The plastic plugs you can get look somewhat better, but this will disappear them for good.

RMM · « **Reply #806 on:** February 03, 2015, 09:37:25 PM »

Quote from: stalwart on February 03, 2015, 01:37:44 PM

Here's a tip for getting rid of those extra holes:

JB high temp epoxy putty. After about an hour it can be filed and sanded smooth. It gets rock hard overnight. It can be painted... and as it is high temp, I am going for powder coating.

Those holes bug me. The plastic plugs you can get look somewhat better, but this will disappear them for good.

Great idea and thanks.

What's going to happen to the ball detent contraption in the upper right of the receiver??

rsterne · « **Reply #807 on:** February 03, 2015, 10:32:56 PM »

Today I lengthened the cocking slot towards the rear in the receiver and tube, and lengthened the bolt slot at the back by 1/8".... That gave me extra bolt and hammer travel, and allowed me to determine how far to extend the nose of the new hammer and how far forward to move the sear lug.... I then made the new cylindrical hammer, and on first trial found I couldn't close the bolt once the gun was cocked, because with the cocking pin aft the milled flat in the bolt wasn't long enough, so that had to be extended to the rear as well.... Here is the new hammer assembly.... The hammer weighs 84 grams, and the spring guide another 22, so the total weight is 106 grams....

While checking clearance at both ends of the hammer travel, I found that in order to be able to preload the spring to coil bind I had to allow the 7/16" D adjusting screw to move into the hammer, so I drilled a 1/4" deep recess in the back of the hammer for that.... Then I found out that the adjusting screw I made yesterday was too long.... it projected too far aft and would hit the stock when backed off.... so I had to make another one from a 1" bolt.... In the position in the photo above it is set for no preload with the hammer sitting against the back of the valve (backing block), which I had shortened slightly.... I also ground almost 1/16" off the end of the MRod poppet so that it is flush with the back of the block when closed.... The nose of the hammer extends 0.200", so that is the limit to the valve lift, more than it will ever need.... Here is the finished spring guide, the new 3" spring, and the original 2.3" spring....

After looking after a few other small details, it was time to assemble the action and measure the hammer stroke.... In the photo below the gun is uncocked, the preload adjuster is set where it would be to have no preload on the spring with the hammer just touching the valve stem, and the distance between it and the O-ring is the maximum lift available before the hammer face hits the backing block.... When the adjuster is wound in to coil bind, it is about 1 thread from fully in....

In the photo below, the gun is cocked.... You can see how far back the spring guide is projecting (it will be shortened after testing to not hit the stock), the O-ring indicates the available hammer travel, including the valve lift.... That measured out to 30.4 mm, and the lift is 5 mm, so I ended up with exactly 1" of hammer stroke to valve contact.... The bolt handle actually moves 36mm total, and the gun cocks less than 1mm from the back of the slot, so you can see how much the rolling sear has to rotate aft to reset, over 4mm.... You will also note that the front of the bolt is retracted clear of the magazine slot, you don't have to pull the bolt back past the cocking position to change magazines, a really nice feature....

This day emphacized how many things change when you start modding an airgun.... A day that started as "I think I'll make the hammer" turned into a full day in the shop, solving one problem, which created two, and those created four, etc.etc., and pretty soon it was dinner time.... Now don't get me wrong, I enjoy this kind of project.... but it sure shows how much work goes into doing this kind of a conversion.... and the huge number of hours you have to be prepared to spend to figure everything out.... Tomorrow I plan to fit the stock, and tidy up a few small jobs and then take a break to contemplate the next step in this conversion....

Bob

stalwart · « **Reply #808 on:** February 04, 2015, 03:07:57 AM »

Very nice...as always!

Would there be anything to gained by making the bolt's nose (the lift) adjustable?

stalwart · « **Reply #809 on:** February 04, 2015, 03:10:13 AM »

Quote from: RMM on February 03, 2015, 09:37:25 PM

Quote from: stalwart on February 03, 2015, 01:37:44 PM
Here's a tip for getting rid of those extra holes:

JB high temp epoxy putty. After about an hour it can be filed and sanded smooth. It gets rock hard overnight. It can be painted... and as it is high temp, I am going for powder coating.

Those holes bug me. The plastic plugs you can get look somewhat better, but this will disappear them for good.

Great idea and thanks.

What's going to happen to the ball detent contraption in the upper right of the receiver??

With the slot lengthened, it will actually work to hold the bolt back during mag changes. Stock, not so much.

stalwart · « **Reply #810 on:** February 04, 2015, 06:48:59 AM »

It just occurred to me that if the stock is relieved as I do for the tails, a removable set of weights could be attached to a longer version of Bob's spring guide... all the way at the back. It would eliminate the need for a tail, as it would function identically...

Yes? No?

stalwart · « **Reply #811 on:** February 04, 2015, 06:51:45 AM »

Heck... thread that end of the rod, make 2 thin knurled nuts (think quill stop)... and just stack washers between them.

stalwart · « **Reply #812 on:** February 04, 2015, 07:10:10 AM »

If you put a short tail on it, and that rod came out the back and had a t-handle at the end... and was threaded into the hammer... you could lose the pin, and get all the stroke you would need by cocking it separately. The longer the tail, the farther you could push the port/mag forward... there's enough room for an absurd amount of stroke.

You wouldn't have to use a t-handle... there has to be a few clever ways to cock the thing. I want a pump. I asked, a while back, who made a good pump action... got crickets. Maybe we should?

RHytonen · « **Reply #813 on:** February 04, 2015, 11:09:45 AM »

Quote from: stalwart on February 04, 2015, 07:10:10 AM

... You wouldn't have to use a t-handle... there has to be a few clever ways to cock the thing. I want a pump. I asked, a while back, who made a good pump action... got crickets. Maybe we should?

A lever would be best for me- or maybe even an underlever(with a necessarily external mechanism, fine.)

I definitely need some M.A. over straight bolt action, so a T-handle is also out of the question..

-and the spine surgeon says, in general, (of house, shop & yard work etc.) "always PUSH - never pull."
I notice (unmentionable) has a QB Lever kit - but it looks like pressed sheet metal, flimsier than what I'd want - I always prefer billet.

Annyway... it's barrel ordering day.
Can't decide between .300 and .308 though. Probably that (26?) twist 300, depending on what's developed since, and of course, price..
Going for 43" (being generous, usable outer barrel is about 37")

(shoot. Mike's away. Eric, any advice on the barrel, please email or call!)

Rod

RHytonen · « **Reply #814 on:** February 04, 2015, 11:54:33 AM »

Quote from: stalwart on February 02, 2015, 07:58:39 AM

Got some time in on the Cothran valved rig. .... This little thing is gonna be nasty.

The Cothran valve will fit in the through tube, yes?

Rod

rsterne · « **Reply #815 on:** February 04, 2015, 02:46:51 PM »

Yes you could add weight to the end of the spring guide, but the percentage gain would be small.... In addition, when the action is installed into the stock with the spring guide the length it is in the photos above (let alone longer with an added weight), you can't cock the gun because as soon as you pull the bolt back 1/4" the end of the spring guide hits the stock.... Yes, you could drill a small hole to clear it, but I don't think you want one big enough for a weight.... Although the action would fit into the stock easily with the new adjuster on the back (it slides into the large recess there), once I put the trigger in place, no way.... I had to open up the top front of the recess as in the photo below so that the adjusting screw and the top shoulder on the adjusting block would clear when the action is on an angle as dictated by the trigger group on installation.... You can't see where it is ground out after the action is in place.... You can also see the new hole for the front stock mounting screw.,,,

Here is a photo of the bottom of the stock, showing the location of the new front screw.... I didn't have a blued one, only a plated one.... It screws into the existing 5mm threaded hole in the bottom of the brass valve which is no longer used to hold the valve from moving back, that is done by the three high-tensile screws in the backing block....

Once both screws are in place, the action and stock are mounted together very solidly.... You will notice that the front of the stock has been cut off to clear the back of the tank, which will serve as the foregrip.... I checked the location of where a rear cocking rod would come out, and it should be possible to have about 2" of stroke for a "T-handle", but I have no idea how you would install it.... The spring guide has to be threaded into the hammer to draw it back, not just sitting in the spring pocket, which means alignment with the hole in the adjusting screw is critical to avoid hammer drag.... In addition, the cocking handle could now drag in the hole in the stock, it would be so long it would be prone to bending, and you would have to have a slot in the top of the stock to drop it into place.... I don't think it is really practical on this design without a lot of thought and work.... I would likely go to a side cocking knob screwed into the side of the hammer right at the front and working through a slot in the tube and receiver.... There is just shy of 2" of room between the magazine slot and the vertical bolt slot, so with enough room at the ends of the slot plus the 1/4" diameter of the handle you could get about 1.5" of hammer travel (about 38mm).... Unfortuately, that includes the valve lift (5mm) and the sear rotation (4mm), so the gain would only be about 2mm of stroke, not worth it just for that.... However, it would allow using a much stiffer spring once you are pulling directly on the hammer, the handle has weight, and by using a longer tail in the tube the hammer could be longer and heavier as well.... Certainly not something I am considering for this build, but a possibility if you want to persue a gun in the 200+ FPE range and the Cothran valve doesn't allow that with the existing hammer....

Here are photos of two cocking arrangements I have used on other projects.... "T-handle" rear cocker on my Disco Double....

and the side-cocking arrangement on my Hayabusa....

I find the T-handle awkward, as I have to move my head out of the way to get my hand behind the handle to pull straight back with two fingers.... The side cocker doesn't require you to move your head, but if the cocking effort gets up over 20 lbs. you may have to drop the gun down from your shoulder to get a better grip and better leverage on it to overcome the high effort required.... Bottom line is that increasing the cocking effort too far makes the gun unpleasant to shoot.... None of this is an immediate consideration for this build, we should have tons of hammer energy and momentum.... they are just food for thought for any future stalwart star-wars projects....

Bob

stalwart · « **Reply #816 on:** February 04, 2015, 04:45:51 PM »

Quote from: RHytonen on February 04, 2015, 11:54:33 AM

Quote from: stalwart on February 02, 2015, 07:58:39 AM
Got some time in on the Cothran valved rig. .... This little thing is gonna be nasty.

The Cothran valve will fit in the through tube, yes?

Rod

Yup.

Bob, the orbiting ring of airguns wasn't supposed to be announced until next week. Please check with someone in the PR/Media dept, next time, before leaking any hints? They get edgy about that kind of thing...

rsterne · « **Reply #817 on:** February 04, 2015, 05:44:37 PM »

OOPS!.... ME BAD !!!....

Bob

cwlongshot · « **Reply #818 on:** February 05, 2015, 08:52:04 PM »

Quote from: rsterne on February 04, 2015, 02:46:51 PM

Here are photos of two cocking arrangements I have used on other projects.... "T-handle" rear cocker on my Disco Double....

LOVE the stock!!

My Disco has a nice "for a disco" stock. But I fancy swapping to something like yours.

CW

rsterne · « **Reply #819 on:** February 05, 2015, 10:28:13 PM »

Norm at Disco R Us inlets the Blaster (above in Forest Camo) for the Disco and MRod.... You could probably get him to inlet it for the XS-60c if a few guys lined up.... just a thought (not me, BTW, haven't got the cash).... I laid my project gun up against the stock above, and the back of the trigger mounting lug (stock or my new one, but a cylindrical one would look better) comes level with the back of the breech in the photo above.... and the main tube needs to be set about 1/4" deeper than the upper tube in the Disco to have the trigger group sit in the right place.... OR the stock at the trigger location could be cut thinner to expose the XS-60c trigger with the tube set the same depth as the upper tube in the Disco.... Using the same tube depth would allow a twin-tube setup within the Blaster stock with an XS-60c.... Either way, it could be done....

Bob

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XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 456059 times))