Hello to everyone.I've been out of the sport for 3 years or so, but I'm getting back now.
Some 4 or 5 years ago I decided to mess up with my crow magnum.Long story short, I got up to 40 FPE out of it with CP .22.Yes , I know , if you do the math , yes , they were going supersonic.I just wanted to see what could be done as far as power goes.Needless to say accuracy went out the window, so it was detune back to between 970 to 950 fps ,wich happend to be the sweet spot for MY particular gun.
The messing up part involved a complete redesign of the piston and seals and home made lubes.The new piston was a dead blow hammer type of my own creation.At the end I retired the gun for good until the day I have enough time to make a new compression chamber and trigger assembly(the factory ones suck , in my opinion).
It got replaced by a 350 in .177.Perfect out of the box.Some little tuning ,lube , deburing ,new seal, normal stuff, and voila! You cannot get any more power out of a .177 without going supersonic.It is dead accurate and it shots better than I can.
The big question now is: can the same be done with a .22 model? say having Kodiaks moving at 950-970 fps, or is the swept volume not enough to create hat much energy?(about 43-44 FPE)
I'm thinkin of getting one and mess with it too and see what I can do, but I'm sure some of you guys have done just that.My plan is to redesign the piston ,make it way heavier, same dead blow concept and use the standard spring for the 48 instead of the 350 spring , to gain room for a heavier piston made entierly out of brass (wich is heavier than steel)and use the same seal used on the Crow magnum.
The general idea is to get maximun power amd still keep the accuracy, 'couse who cares how hard you miss the target!
What do you guys think?
By the way , if you want that much power, why dont you get a PCP? some may say. Because I like a self contained unit.I dont understand the need of scubadiving gear in the middle of a forest, and I think the pump is more suited for a bike, isn't it?
Thank you guys.
I think that the biggest battle you have is how to get a shuttle-cock shaped pellet, fly well and true at supersonic speeds.
I'd much rather have accuracy than power, but whatever floats your boat....that's fine by me.
If you want more power, get a bigger calibre still, say .25, but then generating the kind of push needed for it to climb up to around 900fps, you are talking of a very unwieldy airgun that probably weighs a lot.
Perhaps you might want to consider a bullet shaped "pellet". Then again barrels with standard airgun rifling might not be suitable.
Its never ending, but good luck and keep us posted.
having done a lot of research and time in the 350 platform. I would be hard pressed to see any thing more than 925 to 930fps. Cant say it CANT be done as they all said getting abouve 900 with a 350 would make it unshootable. Its my most accurate hunting gun. I have my .22 doing a solid 915 to 920 with 14.2 Super H. That gun is modded in every way. As for brass piston . Bad Idea Brass will not hold the abuse of hardened steel. You only have so much air volume to work with. Id be real interested to hear more of your ideas as many here know I am a hunting gun builder. Id love nothing more than a 40 ft lb monster that is doing 950 with a 25 grain pellet !
David suggested a bullet type pellet can you get these 30 grain ones in the picture where you are? just a idea.
I am interested in hearing about peoples experiments with springers, Chris has already done a great job on a 350 but I have not heard of any real experments with the 460 as it has got the same swept volume also plenty of room for a big fat spring. It sounds like you have the facilities to make parts so it must be fun. I agree about the PCP thing.
Barry.
I know about brass not being the ideal candidate for material, but there are ways arround it.The original piston on the Crow magnum is NOT harden.Harden steel can crack and break (springs come to mind).I could share ideas with whom ever wants to.I am a injection mould designer and maker.Have a very well equiped shop in Barrie Ontario, and have a top of the line german machining center, swiss made cnc EDM,mill ,lathe,swiss made wire cut EDM , grinder,.....It goes on.I have a background in mechanical engeneering and a passion for airguns and muzzleloaders.If any of you guys are in my area let me know and we can get together for some fun "air" time.
I suppose it is better to shear ideas than to share them
May 18 2009, 6:33 PM
once separated into little pieces you can come up with new ideas! LOL!
Hiya Otto! I still remember you, nice going with that dead-blow piston of yours!
I think that from the standpoint of construction, the 350 is the better gun to start with. IIRC, The 350 has a peculiar piston that uses a pillared extension, that space could be used to hold tungsten "sand" and turn the exactly same machine into a de-bounced spring gun.
Look at the piston in the 350 and decide.
Perhaps some friends here could volunteer some pictures of their pistons?
HI hector,
I always look for your posts, always some interesting technical info.Another idea that I would like one day to experiment with, is a gun with NO thansfer port.What!? Yes , just to see what happens , a piston that completly fills the transfer port.The ideal candidate for that is my 52 luxus (beatiful gun, hope it doesn't end like the Crow magnum LOL).
Something that you can clarify to me is some observations that I made on penetration.
For the sake of argument lets consider two of my guns.The first is a crow magnum set at 30 fpe with CP .22, the other the 350 at 21and change fpe with CPH .177.Both guns achived the same penetration on many diferent materials.
I red many times that the .177 is for feathers and the .22 for fur.The reason behind that seems to be that a .177 tends to drill easier tru feathers and the .22 has more mass.
In my own experience I tend to agree and desagree at the same time.After cranching some numbers I got a big surprise.Both those guns were shooting the same pellet(here I am talking about the same head shape, same alloy ,disregard completly the ballistic coeficient and weight )and both caused the same damage on game.I even tested on the same animal at diferent angles (that one went for science).Even the damage on bones was similar .
I came to the conclusion that both gun are equal.How is it possible? one is only 21 fpe and the other a monster 30 fpe.are you ready? they both have 853 fpe/sqr inch with the same pellet shape on impact.
If you do some numbers ( I know you like that) you will see that it is easier to have more penetration with a .177 because , for a given speed ,you reach more fpe/sqr inch.In other words you need more gun in .22 than you need on .177.
Do I make any sense?
PS:that dead blow piston is sooo sweet,But that was just the first one HEHEHE!
I always enjoyed your well-thought out machinings (pun intended) LOL!
There are a lot of shooters and a few whiners, but very few doers. Luckily, you are a good shooter and good doer! My pleasure to correspond with you, sir!
On the transfer port thing, you are very right, except probably not in a Diana airgun. The flat face of the cylinder would not make it a good candidate. Ideally, the cylinder should have a cone end that finishes in the transfer port, and the piston have the same conical end (plus 1/4°) and a small "knob" to protrude into the transfer port after the first initial impact has reached its end. This will yield maximum energy transfer from the cylinder into the barrel. BUT it will also reduce the overall volume and it will raise the top temperatures by a substantial amount, special O-rings would have to be used in that design.
As it is now, the architecture of the seals allows for the extra compression of the air trapped WITHIN the seal's lips and that is the final-top push.
On the penetration issue.- What you say is true, the 0.177" has much more penetration than a .22", it's simply a question of how much force you need to punch a big hole as opposed to a small hole. Force is obtained from the deceleration of the pellet once it hits the target, and what defines the "punch-through" is pressure, which is what materials resist to. So, given that you have made the calculation, I will believe you and concurr that 21 ft-lbs in 0.177" is about the same, penetration-wise, to 30 ft-lbs. in .22"
There is ONE exception, though, and that is that the smaller pellet should not arrive to the target with enough speed to expand the pellet (each pellet has a different expansion speed). If the pellet expands, then the equation becomes much more complex.
Now, from a purely ergonomical standpoint, I would ask if you have calculated the Energy Efficiency of your airguns, meaning that you need to measure the compression force applied for every small incremental arc of the cocking lever (let's say every 10°) and then compared it with the energy output. You can get 50 ft-lbs of energy out of an airgun, question is if it is practical to do so in terms of effort, endurance, reliability, accuracy, etc. etc. etc.
I just happen to like the 22-25 ft-lbs region in .22" it is a very stable region for pellet and gun, and it enables you to shoot to nearly POA from 22 to about 55 yards, so no need for anything more complicated in the field. The same goes for about 18 ft-lbs. in 0.177"
But that is JMHO.
Do keep us posted and it would definitely make some sense to use the small Tungsten shot now available as part of your design, or you can buy tungsten powder (sand) from Corbin Manufacturing.
HI Hector,
You are correct in terms of the current design on a Diana gun when it comes to the piston face and seals bunning due to very high temperatures.I simply would make a new compression chamber with a taper end face and a piston with the same angle.The same goes for the port ,say, 5 degrees per side and 4,5 degrees on the piston on that said "knob".As for seals, they would have to be on the bigger diameter of the piston, just a few thousands form the beggining of the taper face.For that I can look up on hydraulic catalogs for seals inthe range of 5000 and up psi and extreme temperature conditions.No need to reinvent the wheel here, and take it from there.
In the case of a 48-52 platform , the advantage is that the barrel and cylinder are concentric, and the mod just drops in without any change to the rest.If it does not work ,oh well, just put the old ones back.
Too nice of a gun to retire yet LOL.
As soon as I have time,I will start with this mod before I go to the 350.Is a lot esier and faster.Who knows, if it works I may make a few and have others try them for a second opinion. I can even sell them too.
So many thigs to do, so little time...
would still insist in the 1/2° difference f the cones, though, more than the 5° you suggest, it seems to me that the slack volume could lead to the pounding of the piston into the cylinder and further deformation of the piston, leading to reduced life/lockup.
And, exactly the same angle would lead to the possibility of air being trapped at very high temperatures and we do not want that either. We want some way for air to go through to the barrel. As MUCH as we can, therefore we need to allow "escape routes" that lead to the barrel/bore.
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