Hello again from the wonderful, if slightly infirm, world of Vindicare Assassin.....
Just a quick report on this topic before I get to the real reason of this post..... http://www.airsoftsniperforum.com/32-general-sniper-talk/7346-diy-gun-mods-13.html ..... post #195..... it works and its a keeper, no faffing with hop patches, just use the hop rubber as the contact patch, though it does require the feed to wear in a little before it becomes smooth to load.
Now..... This is really going to bake your bean when I put this to you all and you start to think about it from a physics point of veiw.
Just rescently I've given airsoft a back seat and been concentrating on Airguns, more over spring powered Airguns and the tuning that goes into them. I'll also hasten to add, none of this applies to HPA (PCP in airgun speak) guns as forcing maximum air/gas into the shot cycle is always going to be the best way forward
With that in mind I'm slowly coming to an opinion we are tuning our rifles all wrong, and this will fly straight in the face of all those who believe we are.
In Airsoft we strive to gain the most power, from the softest spring, with the lightest piston, using the largest diameter nozzle, to force the largest amount of air down a narrow tube as smoothly as possible, we use sorbo/silicone as a buffer pad to help prevent the heavy crash of the piston into a heavily ported cylinder head.
This is grand, it produces lots of fps easily, the recoil is minimal, and with all the new 'long' hop patches it sends a BB out nice and consistently.
What we fail to take into account is "why" this all works, and I've come to a conclusion we are selling ourselves short on possible performance.
Has anyone actually considered 'why' these new long hops work so much better??
In Airguns everything is based around compression ratios, pellet position within the barrel and the Trasfer Port diameter and length, and tuning them to give the chosen pellet the best flight caracteristics as efficiently as possible, with the shortest lock time possible (time it takes the pellet to leave the barrel).
I used to drill my nozzle on my VSRs out to 5mm to allow the air to push through easier and create higher fps, what I didn't consider was that easier pushed air was infact pushing the BB right from piston release, which is bad because this means that the BB is potentially halfway down the barrel, or worse still out of it if its short, before the piston has any time to reach maximum compression, this is why the long hops and LRBs all appear to work so well. It means the piston is farther into its compression stroke before the BB becomes 'off hop'.
My Airgun is restricted in the UK by law to 12ft/lbs with any pellet, I use 16 grain pellets ( quite heavy when you consider a .2 only weighs 3 ish grains) and my gun gives 550ish fps with them, yet the Transfer Port (read nozzle in airsoft parlance) is only 3.8mm in diameter and 14mm long and it isn't ported or flowed in any way, it just has a slight radius to its inlet and outlet faces. There is even a BSA Gas-Ram rifle that has just beeen released that produces 12ft/lb and only has a 2.8mm Transfer port!
This is done for a reason.... it stops the piston head slamming into the cylinder head by using the compressed air as a spring, yet the high pressure spring pushing the piston continues to increase the compression, all this happens and yet the pellet has only moved a couple of millimetres, maintaining the compression in the cylinder until it has built enough to expand its skirt and over come the drag of the barrel/rifling.
So, I put it to you what we should all be doing is infact the polar opposite of what we are doing.
What we should all be doing is running the highest power spring we can, through the smallest nozzle we can, to enable our hop units to maximise their potential AND to increase the longevity of our cylinder/piston heads.
Now, as most of you who know me will be aware I wouldn't just come on here spouting crap without having done at least some testing of the theory, and here it is....
The test gun is a Ares Dragunov SVD-S, Fps before test 447 +/-3(w/.2), useing Guarder .28s, it has a 6mm long flat hop, on a 550mm long LRB with 2mm droop, nozzle diametre - 5mm, M120 spring (AEG spring rated @400/420 fps) plus 22mm preload washer. Shot cycle is a nice solid snap from the piston, a bit of felt surge type recoil( forwards) from piston impact and a percieved reasonably flat trajectory out to about 80 yrds.
So, I glued a nozzle restrictor in with a diameter of 3.5mm x 6mm long, just rounding the leading edges a bit, cutting it flush with the nozzle end, re-installed everything 'as is' and tested again.... first, I'd lost about 50fps!! Test fire showed the drop off in power also lost range of about 10/15 yards but BB flight had straightened out.
Next, as this is the stiffest AEG spring I possess, I pre loaded the hell out of it and re tested, chrono is now showing 438 +/- 3(w/.2), again test fired, using .28s, and the trajectory is noticably flatter, the firing cycle is now alot smoother, cocking effort is not much more than before and there is now no felt surge recoil, but the lock time still appeared slow.
This time I added weight to the piston, only about 10grams, and re-tried it, this time the lock time speeded up, but for only a 5 fps gain. I can only put this down to the heavier piston increasing the compression ratio within the cylinder before the BB gets released, surge recoil didn't increase noticabley.
The other thing of note, was a noticable resistance to cross wind in the trajectory, we have 30mph gusting winds here this weekend pushing 90degrees(ish) across my test range, on the original set up the BB appeared to start to drift as soon as it left the barrel, with the new high compression system the BB appeared to fly alot straighter, alot farther, before the wind took it... bear in mind I'm only using .28s..... at first I thought this was just the wind and more effective hop helping to over hop the BB, but after firing some more shots I realised the BB was still flying down my cross hairs, so it couldn't be over hopping.
I can only put the percieved flatter trajectory down to the fact that the hop and LRB are actually doing their job more efficiently, as the air compression has built up to a higher ratio before the BB starts to move.
.... So, there you go, I plan on doing more testing on this in the future using my VSR as test bed as its due a full rebuild, and also probably in the SVD but with the heaviest AEG spring I can purchase here in the UK, but as of now it can stay like it is as I've got 2 Airguns on the bench in need of a rebuild.....
So what do you think, if I am correct, and it is the way forward for high powered rifles/AEGs should we all be buying high torque everything, putting up with a trigger response that is slightly slower, as in the real world even the fastest trigger response makes no difference if the BB lock time is as slow as a gun shooting sub 300fps and your only getting half the hop effect your gun has the potential to provide, and of coarse this all gets worse the higher up the fps scale you go.
Also think of the benifits to V2 gearbox owners, reduced front end impact, as you potentialy fit a ruddy gert spring infront of the piston just for 1.....
Have fun trying to get your heads round all this... Let me know how you get on.....
Just a quick report on this topic before I get to the real reason of this post..... http://www.airsoftsniperforum.com/32-general-sniper-talk/7346-diy-gun-mods-13.html ..... post #195..... it works and its a keeper, no faffing with hop patches, just use the hop rubber as the contact patch, though it does require the feed to wear in a little before it becomes smooth to load.
Now..... This is really going to bake your bean when I put this to you all and you start to think about it from a physics point of veiw.
Just rescently I've given airsoft a back seat and been concentrating on Airguns, more over spring powered Airguns and the tuning that goes into them. I'll also hasten to add, none of this applies to HPA (PCP in airgun speak) guns as forcing maximum air/gas into the shot cycle is always going to be the best way forward
With that in mind I'm slowly coming to an opinion we are tuning our rifles all wrong, and this will fly straight in the face of all those who believe we are.
In Airsoft we strive to gain the most power, from the softest spring, with the lightest piston, using the largest diameter nozzle, to force the largest amount of air down a narrow tube as smoothly as possible, we use sorbo/silicone as a buffer pad to help prevent the heavy crash of the piston into a heavily ported cylinder head.
This is grand, it produces lots of fps easily, the recoil is minimal, and with all the new 'long' hop patches it sends a BB out nice and consistently.
What we fail to take into account is "why" this all works, and I've come to a conclusion we are selling ourselves short on possible performance.
Has anyone actually considered 'why' these new long hops work so much better??
In Airguns everything is based around compression ratios, pellet position within the barrel and the Trasfer Port diameter and length, and tuning them to give the chosen pellet the best flight caracteristics as efficiently as possible, with the shortest lock time possible (time it takes the pellet to leave the barrel).
I used to drill my nozzle on my VSRs out to 5mm to allow the air to push through easier and create higher fps, what I didn't consider was that easier pushed air was infact pushing the BB right from piston release, which is bad because this means that the BB is potentially halfway down the barrel, or worse still out of it if its short, before the piston has any time to reach maximum compression, this is why the long hops and LRBs all appear to work so well. It means the piston is farther into its compression stroke before the BB becomes 'off hop'.
My Airgun is restricted in the UK by law to 12ft/lbs with any pellet, I use 16 grain pellets ( quite heavy when you consider a .2 only weighs 3 ish grains) and my gun gives 550ish fps with them, yet the Transfer Port (read nozzle in airsoft parlance) is only 3.8mm in diameter and 14mm long and it isn't ported or flowed in any way, it just has a slight radius to its inlet and outlet faces. There is even a BSA Gas-Ram rifle that has just beeen released that produces 12ft/lb and only has a 2.8mm Transfer port!
This is done for a reason.... it stops the piston head slamming into the cylinder head by using the compressed air as a spring, yet the high pressure spring pushing the piston continues to increase the compression, all this happens and yet the pellet has only moved a couple of millimetres, maintaining the compression in the cylinder until it has built enough to expand its skirt and over come the drag of the barrel/rifling.
So, I put it to you what we should all be doing is infact the polar opposite of what we are doing.
What we should all be doing is running the highest power spring we can, through the smallest nozzle we can, to enable our hop units to maximise their potential AND to increase the longevity of our cylinder/piston heads.
Now, as most of you who know me will be aware I wouldn't just come on here spouting crap without having done at least some testing of the theory, and here it is....
The test gun is a Ares Dragunov SVD-S, Fps before test 447 +/-3(w/.2), useing Guarder .28s, it has a 6mm long flat hop, on a 550mm long LRB with 2mm droop, nozzle diametre - 5mm, M120 spring (AEG spring rated @400/420 fps) plus 22mm preload washer. Shot cycle is a nice solid snap from the piston, a bit of felt surge type recoil( forwards) from piston impact and a percieved reasonably flat trajectory out to about 80 yrds.
So, I glued a nozzle restrictor in with a diameter of 3.5mm x 6mm long, just rounding the leading edges a bit, cutting it flush with the nozzle end, re-installed everything 'as is' and tested again.... first, I'd lost about 50fps!! Test fire showed the drop off in power also lost range of about 10/15 yards but BB flight had straightened out.
Next, as this is the stiffest AEG spring I possess, I pre loaded the hell out of it and re tested, chrono is now showing 438 +/- 3(w/.2), again test fired, using .28s, and the trajectory is noticably flatter, the firing cycle is now alot smoother, cocking effort is not much more than before and there is now no felt surge recoil, but the lock time still appeared slow.
This time I added weight to the piston, only about 10grams, and re-tried it, this time the lock time speeded up, but for only a 5 fps gain. I can only put this down to the heavier piston increasing the compression ratio within the cylinder before the BB gets released, surge recoil didn't increase noticabley.
The other thing of note, was a noticable resistance to cross wind in the trajectory, we have 30mph gusting winds here this weekend pushing 90degrees(ish) across my test range, on the original set up the BB appeared to start to drift as soon as it left the barrel, with the new high compression system the BB appeared to fly alot straighter, alot farther, before the wind took it... bear in mind I'm only using .28s..... at first I thought this was just the wind and more effective hop helping to over hop the BB, but after firing some more shots I realised the BB was still flying down my cross hairs, so it couldn't be over hopping.
I can only put the percieved flatter trajectory down to the fact that the hop and LRB are actually doing their job more efficiently, as the air compression has built up to a higher ratio before the BB starts to move.
.... So, there you go, I plan on doing more testing on this in the future using my VSR as test bed as its due a full rebuild, and also probably in the SVD but with the heaviest AEG spring I can purchase here in the UK, but as of now it can stay like it is as I've got 2 Airguns on the bench in need of a rebuild.....
So what do you think, if I am correct, and it is the way forward for high powered rifles/AEGs should we all be buying high torque everything, putting up with a trigger response that is slightly slower, as in the real world even the fastest trigger response makes no difference if the BB lock time is as slow as a gun shooting sub 300fps and your only getting half the hop effect your gun has the potential to provide, and of coarse this all gets worse the higher up the fps scale you go.
Also think of the benifits to V2 gearbox owners, reduced front end impact, as you potentialy fit a ruddy gert spring infront of the piston just for 1.....
Have fun trying to get your heads round all this... Let me know how you get on.....
