XS60C PCP Repeater project

[rsterne]

Not too sure you can find a valve that would cover that range of calibers, but then again I've never tried a .22 cal barrel on my .45 cal Hayabusa.... Somehow it doesn't make sense to me to use a monster hammer spring to open a huge valve against 4500 psi and then restrict the whole system back down to do what you can do with a smaller, easier to open valve, running much lower pressure....

I'm not saying that one gun can't do it all.... but the concept of just interchanging barrels "at will" and a simple retune seems to me to be just a slightly larger than life goal.... However, the concept of using a single platform, with several sets of internal parts, used in conjunction with the caliber change, is not at all far fetched....

Bob

[stalwart]

Given that the GRS can act as any strength of spring, I'm thinking it and the reg should allow a lot of choices.

Guess we'll see!

[Sfttailrdr46]

Not speaking specifically about AG's but it has been my experience with tools owning just one saw to fit every job makes no sense any more than having only one pipe wrench or one of any specific tool can you do multiple tasks with one saw or wrench yes but as Bob says why take a .45 and choke it down so you can have a .22 also there are numerous obstacles   to having a practical end product and he has way more knowledge about building and performance than I do with AG's

[stalwart]

I'm trying to wrap my head around why, with the GRS, lowering the striker force by lowering the pressure wouldn't work... especially with the reg to play with. I get that it's easier to just own and tune 2 guns, but many I know here don't have the option. They are PB guys, and given that a decent airgun costs more than the equivalent PB, air is already a hard sell. It would be easier to sell a squirrel gun, that could be set up to go big once in a while.

[StevenG]

I think to make that kind of thing reasonable, swapping out internal parts makes sense. Not because you can't do it without swapping them, but because it makes it so much simpler. Instead swapping the barrel and spending 3 days in front of a chrony, drop in internals mean the user can be up and running again in half an hour. I realize that doing this will mean not every gun is getting the best efficiency ever or the ideal tune for that pellet. Let face it, for 99% of use cases that does not matter. That soda can is just as dead with 12fpe or 12.1fpe. Losing one shot at the end of the string does not matter that much.

If I am the imaginary PB guy with one airgun and I only ever use it to shoot tree rats, but I find that just once I want to shoot a pig then I need it to be dead easy. At that point though I wonder how much would really be saved. The barrel, valve, regulator and SSG/GRS have to add up to a considerable fraction of the total cost.

The idea of standardization however is huge for the fellow selling them. He can fab up everything at once and fill boxes to ship out at the customer's request.

[stalwart]

I think to make that kind of thing reasonable, swapping out internal parts makes sense. Not because you can't do it without swapping them, but because it makes it so much simpler. Instead swapping the barrel and spending 3 days in front of a chrony, drop in internals mean the user can be up and running again in half an hour. I realize that doing this will mean not every gun is getting the best efficiency ever or the ideal tune for that pellet. Let face it, for 99% of use cases that does not matter. That soda can is just as dead with 12fpe or 12.1fpe. Losing one shot at the end of the string does not matter that much.

If I am the imaginary PB guy with one airgun and I only ever use it to shoot tree rats, but I find that just once I want to shoot a pig then I need it to be dead easy. At that point though I wonder how much would really be saved. The barrel, valve, regulator and SSG/GRS have to add up to a considerable fraction of the total cost.

The idea of standardization however is huge for the fellow selling them. He can fab up everything at once and fill boxes to ship out at the customer's request.

All true... but... If that guy wanted to shoot a pig once a year, he really wouldn't care about efficiency or shot count. He would probably just crank it all up, and sight it in. As long as he got 3 shots... he'd be happy.

He could then return to his original settings (if he was smart enough to count turns, and write down GRS pressure) then sight it in. Back to the rats for another year.

Makes me think a sticker, with graduations (w/o numbers) might be a cool thing for the new regulators.

Heck, the gunsmith could easily run a few tunes through it, chrony, and produce a spreadsheet (see what you've DONE to me, Lloyd?!?) that that guy could use as a guide. Being able to read (and record) the striker force, in psi, would simplify a lot of things. It would also allow people to share reasonably accurate tune data.

[stalwart]

A gun with a gauge on the upper tube, and GRS, could be accurately tuned (and returned to a specific tune) with a screwdriver and a pump. Or, am I missing something?

[rsterne]

To put it simply, just build it, tune it, and prove it can be done; there is no point arguing about it, because it is uncharted territory.... I personally think that a gun shooting 500 FPE in .45 cal won't produce a .22 with enough efficiency, and consistency, to be an accurate 20-30 FPE gun with lots of shots, which is what most users would want, most of the time, just by retuning with no parts changes.... However, I've never tried (because of the limitations of coil springs, hammer weight and travel, and current valves), and I've been wrong before, so I wish you luck.... Perhaps the GRS, once you perfect it, will allow those order of magnitude changes in FPE within a single gun.... You may need a balanced valve, to be easy enough to open, to accomplish it without a half pound hammer with 2" of travel, of course.... You would have to build the gun as a .45 and then have the ability to detune it to a .22 cal plinker, IMO....

Bob

[stalwart]

I hadn't quite imagined that large a range, but your point is taken. I would be happy if it would go down closer to .22LR power most often used on the ground squirrels here, ~150fpe. You can't get close to them, and lots of guys use .177 CFs to reach out there. I don't see anyone around here paying much for a plinking gun...

I'm not talking about 1 gun to adjust to fit every man, I'm talking about a gun that can entice a PB diehard hunter into the sport, and keep him here. If he decides he wants to shoot beer cans... we have Walmarts, too.

Yup, it will take building one to see what kind of range that would allow without hammer changes, but, within that range... I can't imagine an easier to tune gun.

[Buldawg76]

I have been keeping up on this thread built seem to have missed out on just what a GRS is as compared to the SSG or if they are in fact similar at all.

So what exactly is a GRS and how does it work or perform in an air gun.

Mike

[stalwart]

Gas Ram Striker... discussed a while back. An air spring, adjustable over a very wide range by changing the pressure in it.

[stalwart]

Bob is correct that a balanced valve would go a long way toward making the gun versatile. http://www.cothranmachine.com/WhatNew.HTML  I hope to find out how far, after the move. The Cothran isn't cheap, but the time it takes to work around it isn't either.

I'm hoping 150 to ~400fpe can be pulled off without too many changes to the base design, as that would give SA a line of guns from 7fpe up (with Bob's grizzly specs dead center, after which is the perfect point to go balanced). If I can do 150 and up with 2 or 3 hammers, that's cool.... but, if I can do it with 1? I could built the entire lower gun, and the caliber kits, in advance. Ship in no time. Anyone who knows me, knows how hard I work to eliminate excess part #s... I learned that's never a bad idea.

Also, if "that guy" bought a dual caliber set up, and decided it was enough of a PITA (it is) to change over... he could come to me, and we'd put a gun under his second caliber. In a few mins. If we need multiple hammers to cover him.... oh well, it's coming down.

I can't wait to see what the GRS can do for these.

We'll see. It's all "dreaming out loud" for now.

[Buldawg76]

Gas Ram Striker... discussed a while back. An air spring, adjustable over a very wide range by changing the pressure in it.

Thanks and sounds very interesting and I can see how it would very adjustable for a wide range of levels. Is it small enough to fit in a normal spring pockets constraints and by chance do you have a page range where it was discussed to narrow it down in rereading the entire thread.

Mike

[rsterne]

Once you start talking 400 FPE, unless you have a balanced valve, the hammer weight, travel, and spring energy required get oppressive in a hurry.... In addition, there is no need to go to 7/16" or full bore porting to get 400 FPE, particularly if you have 4500 psi available.... Going with huge ports means the valve is harder to open.... My .457 Hayabusa hit 550 FPE with a 336 gr. bullet on 3600 psi with "only" 3/8" porting.... but the 0.406" valve throat at 3600 psi still took a 237 gr. hammer with 2" of travel and a 4.5" long, 0.072" wire spring to open it.... It could be tuned for 6 shots at 419 FPE on 640 cc of air.... Could that be tuned down to "only" 150 FPE, possibly.... but you would still have the half-pound hammer slamming around in there....

Bob

[rsterne]

I just ran across this thread about DiscosRUs closing and up for sale.... http://www.gatewaytoairguns.org/GTA/index.php?topic=109598.0

Since Norm recently stated that he could still do inletting of stocks for the Double Tube setups, it might be a good idea to ask him if/how this decision impacts that statement....

Bob

[stalwart]

Once you start talking 400 FPE, unless you have a balanced valve, the hammer weight, travel, and spring energy required get oppressive in a hurry.... In addition, there is no need to go to 7/16" or full bore porting to get 400 FPE, particularly if you have 4500 psi available.... Going with huge ports means the valve is harder to open.... My .457 Hayabusa hit 550 FPE with a 336 gr. bullet on 3600 psi with "only" 3/8" porting.... but the 0.406" valve throat at 3600 psi still took a 237 gr. hammer with 2" of travel and a 4.5" long, 0.072" wire spring to open it.... It could be tuned for 6 shots at 419 FPE on 640 cc of air.... Could that be tuned down to "only" 150 FPE, possibly.... but you would still have the half-pound hammer slamming around in there....

Bob

It looks like the best way is to go with the Cothran, at least until something can be built in house. I looked things over, and there is no way to to come close enough to the cost with a conventional set up, unless I farm the parts out (with 2 hammer choices? 3?)... and that might not be that much cheaper.

I avoid single source parts like the plague, for some good reasons learned the hard way... but, Cothran has a good reputation, and seems to be in this for the long haul.

[stalwart]

Gas Ram Striker... discussed a while back. An air spring, adjustable over a very wide range by changing the pressure in it.

Thanks and sounds very interesting and I can see how it would very adjustable for a wide range of levels. Is it small enough to fit in a normal spring pockets constraints and by chance do you have a page range where it was discussed to narrow it down in rereading the entire thread.

Mike

I don't have a range for you, when you find it please post the beginning post #?

I have been keeping a table of contents, but neglected to put that in it.

I no longer discuss prototypes here. The GRS concept was brought out in Russia, 2 months after it was posted here. The guy got it wrong, but the point remains... I have had people waste a bunch of my time (the list is growing, VRD LLC ring a bell?), trying to steal my ideas while pretending to want to help, invest or buy. I'm quite embarrassed at how much of my time I let these kind steal from me... I don't need to worry any more about being made a fool of.

[rsterne]

I have never had a Cothran valve, but I rather doubt that the Disco version is capable of 400 FPE, I don't think the MRod version is even in that league, but so little information is available on that one (just released) I could be wrong.... The 1/4" (or smaller) ports, throat, etc. in the Disco version will never be able to produce 400 FPE, however, so I think you will be in the situation, just like the GRS, of designing and building your own balanced valve to produce that kind of power in a 3/4" ID tube (if possible)....

BTW, Eric, it is not my intention to rain on your parade here.... only to hand you an umbrella to shelter you from what may be a downpour of (over)enthusiasm.... ie a reality check.... 

Bob

[lloyd-ss]

I have never had a Cothran valve, but I rather doubt that the Disco version is capable of 400 FPE, I don't think the MRod version is even in that league, but so little information is available on that one (just released) I could be wrong.... The 1/4" (or smaller) ports, throat, etc. in the Disco version will never be able to produce 400 FPE, however, so I think you will be in the situation, just like the GRS, of designing and building your own balanced valve to produce that kind of power in a 3/4" ID tube (if possible)....

BTW, Eric, it is not my intention to rain on your parade here.... only to hand you an umbrella to shelter you from what may be a downpour of (over)enthusiasm.... ie a reality check.... 

Bob

From what I have seen in my years of non-airgun manufacturing in a very mechanically technical environment, truly "original" ideas are extremely rare.  But to me, what really matters is who can actually get the ideas  to work, first as a proof of concept, and then the really difficult part, getting them to work in a manufacturable manner.  That can be extremely difficult, and is often not succesful.

But what I really wanted to comment about is the new Don Cothran valve.  I talked to Don at length on the phone the other night and ended up buying an M-Rod Power House valve from him.  It is in my hands now, he he, he.     Don spent a lot of time perfecting this valve and for that I have the ultimate respect.  I will be starting a thread about the installation and performance of the valve very shortly, trying it in  a couple of different Marauder Rifles.  A fella at the Fun Shoot had one in a Disco based rifle and it was pretty scary. 
I am excited about this.  I have no expectations regarding air efficiency,    but for power, I am expecting big numbers.
Lloyd

[Sfttailrdr46]

I have never had a Cothran valve, but I rather doubt that the Disco version is capable of 400 FPE, I don't think the MRod version is even in that league, but so little information is available on that one (just released) I could be wrong.... The 1/4" (or smaller) ports, throat, etc. in the Disco version will never be able to produce 400 FPE, however, so I think you will be in the situation, just like the GRS, of designing and building your own balanced valve to produce that kind of power in a 3/4" ID tube (if possible)....

BTW, Eric, it is not my intention to rain on your parade here.... only to hand you an umbrella to shelter you from what may be a downpour of (over)enthusiasm.... ie a reality check.... 

Bob

From what I have seen in my years of non-airgun manufacturing in a very mechanically technical environment, truly "original" ideas are extremely rare.  But to me, what really matters is who can actually get the ideas  to work, first as a proof of concept, and then the really difficult part, getting them to work in a manufacturable manner.  That can be extremely difficult, and is often not succesful.

But what I really wanted to comment about is the new Don Cothran valve.  I talked to Don at length on the phone the other night and ended up buying an M-Rod Power House valve from him.  It is in my hands now, he he, he.     Don spent a lot of time perfecting this valve and for that I have the ultimate respect.  I will be starting a thread about the installation and performance of the valve very shortly, trying it in  a couple of different Marauder Rifles.  A fella at the Fun Shoot had one in a Disco based rifle and it was pretty scary. 
I am excited about this.  I have no expectations regarding air efficiency,    but for power, I am expecting big numbers.
Lloyd

Lloyd a suggestion please start a new thread with your Marauder Cothran Powerhouse valve as a part of your project . I am sure myself among others will be following your efforts , but my request is somewhat motivated by my personal Marauder project