GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: robs5230 on June 19, 2021, 05:27:47 PM
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Hi.
Finally decided to reg my 1720T which I'm using as a rabbit rifle at sub12 in the uk.
Prior to regging, its been running with a 3.5mm TP and some adjustments on HST and throw, and giving 25 shots in the sweet spot at 795 fps with a 7.87 pellet and just shy of 700fps with JSB heavy.
After regging, I'm peaking at 735 with express and 670 with JSB heavy.
The reg is set at 95 bar.
Any advice to get the power up to around 800 with express and 700 with heavys, would be much appreciated.
Do I need to be upping reg pressure?
Is a 3.5mm TP too big?
Do I need a different hammer spring or hammer?
Many thanks
Rob
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Hi Rob
I have my 1720 setup with a Lane reg set at 90 bar and am getting 725 fps with 10.34s and 790 with 8.44s using a 3.5mm port all the way from valve exhaust, TP and barrel so if you have not opened the valve exhaust and barrel to 3.5mm yet it needs to be done. I am using a JSAR end cap with the dual spring setup but you may be able to just get by with a short heavy spiting since I do not think the JSAR Kit is still available.
I get about 45 shots with it set up this way. the big key is no restriction in air flow from valve to pellet and eliminate all hammer bounce so you just sip enough air for each shot. You need a short heavy spring so you can hit the valve stem hard enough but still have some free play between valve stem and hammer when uncocked so the hammer is not rebounding off spring after each shot. I run about .060" to.080" free play between hammer and valve stem when uncocked.
Hope this helps.
BD
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Hi Rob
I have my 1720 setup with a Lane reg set at 90 bar and am getting 725 fps with 10.34s and 790 with 8.44s using a 3.5mm port all the way from valve exhaust, TP and barrel so if you have not opened the valve exhaust and barrel to 3.5mm yet it needs to be done. I am using a JSAR end cap with the dual spring setup but you may be able to just get by with a short heavy spiting since I do not think the JSAR Kit is still available.
I get about 45 shots with it set up this way. the big key is no restriction in air flow from valve to pellet and eliminate all hammer bounce so you just sip enough air for each shot. You need a short heavy spring so you can hit the valve stem hard enough but still have some free play between valve stem and hammer when uncocked so the hammer is not rebounding off spring after each shot. I run about .060" to.080" free play between hammer and valve stem when uncocked.
Hope this helps.
BD
Hi BD
Looks like I have a bit of work to do then with the valve and barrel porting. Whatever setting I have it on at the minute, it does seem to be using air for no benefit,beyond what I'm currently getting.
Can you give me any idea of a suitable hammer spring? Still running the original 1720T spring at the minute.
It would be useful if one from another model would fit.
Looks like the 1720 is capable enough, if I get it right.
THanks Rob
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I am not sure but I think the maximus uses a shorter stiffer spring. Its best just to take the stock one out and go compare to some from a hardware store or indusrtial supply house to get several to try for the best tune.
The part number for the maximus spring is GBMP-009 from crosman.
The tuning is half the fun IMO.
BD
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I am not sure but I think the maximus uses a shorter stiffer spring. Its best just to take the stock one out and go compare to some from a hardware store or indusrtial supply house to get several to try for the best tune.
The part number for the maximus spring is GBMP-009 from crosman.
The tuning is half the fun IMO.
BD
Thanks
I'll look into a maximus spring. Thanks
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Hope it works out for you and have fun.
BD
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I would recommend Magnum Air Power hammer springs in either .042” or .045”.
I use MAP springs on all of my builds.
Yes, they are shorter than OEM.
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Hi Rob
I have my 1720 setup with a Lane reg set at 90 bar and am getting 725 fps with 10.34s and 790 with 8.44s using a 3.5mm port all the way from valve exhaust, TP and barrel so if you have not opened the valve exhaust and barrel to 3.5mm yet it needs to be done. I am using a JSAR end cap with the dual spring setup but you may be able to just get by with a short heavy spiting since I do not think the JSAR Kit is still available.
I get about 45 shots with it set up this way. the big key is no restriction in air flow from valve to pellet and eliminate all hammer bounce so you just sip enough air for each shot. You need a short heavy spring so you can hit the valve stem hard enough but still have some free play between valve stem and hammer when uncocked so the hammer is not rebounding off spring after each shot. I run about .060" to.080" free play between hammer and valve stem when uncocked.
Hope this helps.
BD
Hi BD.
Any idea where you have your hammer spring and valve throw set on this setup?
Thanks
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Hi Rob
I have my 1720 setup with a Lane reg set at 90 bar and am getting 725 fps with 10.34s and 790 with 8.44s using a 3.5mm port all the way from valve exhaust, TP and barrel so if you have not opened the valve exhaust and barrel to 3.5mm yet it needs to be done. I am using a JSAR end cap with the dual spring setup but you may be able to just get by with a short heavy spiting since I do not think the JSAR Kit is still available.
I get about 45 shots with it set up this way. the big key is no restriction in air flow from valve to pellet and eliminate all hammer bounce so you just sip enough air for each shot. You need a short heavy spring so you can hit the valve stem hard enough but still have some free play between valve stem and hammer when uncocked so the hammer is not rebounding off spring after each shot. I run about .060" to.080" free play between hammer and valve stem when uncocked.
Hope this helps.
BD
Hi BD.
Any idea where you have your hammer spring and valve throw set on this setup?
Thanks
Hammer stroke is set fully CCW or maximum throw and hammer spring is about two turns CW in from fully CCW but I am running the JSAR twin spring setup so it will not correlate to your gun with stock or shorter stiff spring.
I would set reg at 90 bar, open valve exhaust port, TP and barrel to 3.5mm/.140" and hammer at full stroke then just play with hammer springs and settings of them to get desisted tune.
Your plenum size on the huma reg could be different volume than my lane reg so that can make some differences as well with settings.
BD
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Hi Rob
I have my 1720 setup with a Lane reg set at 90 bar and am getting 725 fps with 10.34s and 790 with 8.44s using a 3.5mm port all the way from valve exhaust, TP and barrel so if you have not opened the valve exhaust and barrel to 3.5mm yet it needs to be done. I am using a JSAR end cap with the dual spring setup but you may be able to just get by with a short heavy spiting since I do not think the JSAR Kit is still available.
I get about 45 shots with it set up this way. the big key is no restriction in air flow from valve to pellet and eliminate all hammer bounce so you just sip enough air for each shot. You need a short heavy spring so you can hit the valve stem hard enough but still have some free play between valve stem and hammer when uncocked so the hammer is not rebounding off spring after each shot. I run about .060" to.080" free play between hammer and valve stem when uncocked.
Hope this helps.
BD
Hi BD.
Any idea where you have your hammer spring and valve throw set on this setup?
Thanks
Hammer stroke is set fully CCW or maximum throw and hammer spring is about two turns CW in from fully CCW but I am running the JSAR twin spring setup so it will not correlate to your gun with stock or shorter stiff spring.
I would set reg at 90 bar, open valve exhaust port, TP and barrel to 3.5mm/.140" and hammer at full stroke then just play with hammer springs and settings of them to get desisted tune.
Your plenum size on the huma reg could be different volume than my lane reg so that can make some differences as well with settings.
BD
Hi.
Just rebuilt with the barrel port now at 3.5mm, so 3.5mm straight through and still maxing out at 690 with a 10.34 and despite trying a couple of springs I have here, so I'm still no better off.
I have no idea where to find the short stiff hammer spring that's been recommended. Would you be able to advise of any source over there, and a spring spec that may do it?
The only other thing I can think to do is to lower my reg pressure, from the 95 that its currently set at.
It still seems to be using a lot of air per shot.
This thing is driving me nuts. It was making lovely power before regging , and giving me a very good 25 shot string. Now I cant seem to get it anywhere near
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You have already been told that Magnum Air Power has them.
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You have already been told that Magnum Air Power has them.
The spring is £7.00
Shipping is £57.00
I could do with another option. Thanks
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I have a MAP .042 that is unused 'cuz I use .038 on my builds.
Just pay me the shipping cost when you receive the item.
PM me your full name and addy if you want it.
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Does your reg set right against the valve face or is there a spacer of about a 1/2" to 3/4" that sirs between the reg and the valve face. Or is the spacer part of the huma reg so that there is some plenum between the valve face and reg body. If no spacer or plenum you likely do not have enough volume of regged air to provide sufficient amount of air to get desired fps.
Need at a minimum of 1/2cc per fpe desired. Or if desire 12fpe you need at least 6 cc of plenum but 12cc would be ideal.
BD
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Does your reg set right against the valve face or is there a spacer of about a 1/2" to 3/4" that sirs between the reg and the valve face. Or is the spacer part of the huma reg so that there is some plenum between the valve face and reg body. If no spacer or plenum you likely do not have enough volume of regged air to provide sufficient amount of air to get desired fps.
Need at a minimum of 1/2cc per fpe desired. Or if desire 12fpe you need at least 6 cc of plenum but 12cc would be ideal.
BD
Hi
Sorry for the late reply. The project has been on hold whilst barrel porting was done and I'd sorted a leak.
I've bypassed the gauge with the Huma plenum, so now power isnt the problem. I need to improve the shot count now. At present only getting 24 shots at best settings and I feel it could be a lot better.
Still on the lookout for a shorter stiffer hammer spring to try and prevent valve bounce
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Since you have the power you want from it now your goal is to use the air more efficiently per shot. You likely don't need a short stiff spring now, you just need to eliminate the hammer bounce which is wasting the air.
If you do not have any gap between the hammer and valve stem when uncocked with spring tension fully CCW and hammer stroke fully CCW then you need to cut coils off your current spring until you have between .060 to .080" of gap between hammer and valve stem or put another way you want .060 to .080" of free flight of the hammer before it contacts the valve stem to stop the bounce caused by the hammer rebounding off the valve stem when the valve closes and then having the hammer spring recompressed throwing the hammer back into the valve stem.
Its all a balancing act to get your power desired with only one single opening on the valve stem per hammer strike.
Measure your hammer spring length, wire diameter and number of coils and go to a hardware store that has a supply of coil springs and find ones of similar dimensions to test with and modify to find one that gives you the desired results.
BD
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Since you have the power you want from it now your goal is to use the air more efficiently per shot. You likely don't need a short stiff spring now, you just need to eliminate the hammer bounce which is wasting the air.
If you do not have any gap between the hammer and valve stem when uncocked with spring tension fully CCW and hammer stroke fully CCW then you need to cut coils off your current spring until you have between .060 to .080" of gap between hammer and valve stem or put another way you want .060 to .080" of free flight of the hammer before it contacts the valve stem to stop the bounce caused by the hammer rebounding off the valve stem when the valve closes and then having the hammer spring recompressed throwing the hammer back into the valve stem.
Its all a balancing act to get your power desired with only one single opening on the valve stem per hammer strike.
Measure your hammer spring length, wire diameter and number of coils and go to a hardware store that has a supply of coil springs and find ones of similar dimensions to test with and modify to find one that gives you the desired results.
BD
Thanks.
The factory hammer spring won't be man enough when I cut it, but I do have a slightly stiffer spring (.93mm) wire that I will try to shorten a little. That makes 12ftlb at fully CCW on tension and throw.
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If using the factory hammer ... it has more than enough weight.
WANT MORE POWER ..... Raise the regs output pressure
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If using the factory hammer ... it has more than enough weight.
WANT MORE POWER ..... Raise the regs output pressure
Scott
He has the power he wants from it now but is wasting air with only 24 shots and is trying to improve efficiency, upping the reg pressure will not accomplish that goal. He needs to eliminate hammer bounce IMO.
I do not believe he has any hammer free flight right now.
BD
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Since you have the power you want from it now your goal is to use the air more efficiently per shot. You likely don't need a short stiff spring now, you just need to eliminate the hammer bounce which is wasting the air.
If you do not have any gap between the hammer and valve stem when uncocked with spring tension fully CCW and hammer stroke fully CCW then you need to cut coils off your current spring until you have between .060 to .080" of gap between hammer and valve stem or put another way you want .060 to .080" of free flight of the hammer before it contacts the valve stem to stop the bounce caused by the hammer rebounding off the valve stem when the valve closes and then having the hammer spring recompressed throwing the hammer back into the valve stem.
Its all a balancing act to get your power desired with only one single opening on the valve stem per hammer strike.
Measure your hammer spring length, wire diameter and number of coils and go to a hardware store that has a supply of coil springs and find ones of similar dimensions to test with and modify to find one that gives you the desired results.
BD
Thanks.
The factory hammer spring won't be man enough when I cut it, but I do have a slightly stiffer spring (.93mm) wire that I will try to shorten a little. That makes 12ftlb at fully CCW on tension and throw.
You can also do the Bstaley mod to it by adding o rings between the hammer and valve stem to control bounce and valve stem travel while using the same spring. Just search Bstaley mod to see how it works and how to do it. Then the hammer stroke adjustment becomes your velocity adjustment.
https://www.gatewaytoairguns.org/GTA/index.php?topic=42273.msg395135#msg395135 (https://www.gatewaytoairguns.org/GTA/index.php?topic=42273.msg395135#msg395135)
BD
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Rob sir, I hope you get the tune that you want with either of the 2 size MAP springs.
My builds seem to love the .038”.
Shame the 1st one that I sent you got lost in transit >:(
It might still arrive though when you least expect it ;D