GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: shorty on July 13, 2022, 01:43:36 PM
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Had a good idea the other day so I decided to take a break from work and stay home and play.
Pulled the hammer spring assembly apart and started taking measurements. Looks like the idea just might work.
Then, wanted to see how much it could work in regards to spring adjustment.
At the lowest setting with the port at max, I was able to get 78 fpe for 18 shots with 7%es from 3k to around 2.2k pressure.
I have to stop here for now until I can get my hands on some new shorter stiffer springs.
That low tune was not stellar but ok at 1.13 efficiency.
Peak power was at 2.4k at 920fps.
I have been trying for 900fps using jsb's with a stable shot string for more than 2 mags on a 3k fill.
I think it can get there as long as I can get that preload off the valve stem.
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What happen with Lloyd's pcp efficiency calculator?
I ran efficiency numbers by memory in the above post from a 360cc tank and today I found out the challenger is only 300cc.
The long math stinks.
Anyone have a working link?
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Ordered springs today. 5 to be exact. Holy carp, 55 bucks with shipping.
I had to do up a drawing for the end cap and hand it over to a real machinist (not me). Luckily it's free work.
Printing out the inside guide using a resin printer😁 ( solid ). For the real part I think peek would be the only way to go.
So,
Its looking like a complete drop in hammer spring adjuster for all the challenger platforms.
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8)
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When I tried to shim the stock spring at the rear ,it wouldn't cock, bin uses shim washers at the front of the spring and it works so keep that in mind, I ordered weaker springs to help with the cocking effort ( I have the bullpup 357) and that helped , but I only fill to 3100psi , now that bin has a reg with plenum available I'm thinking of getting one so I can fill to a higher pressure and still have a easier cocking effort, I have extra springs if you need them.
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Re: efficiency calculation
I posted a spreadsheet in the following thread that you can download:
https://www.gatewaytoairguns.org/GTA/index.php?topic=197608 (https://www.gatewaytoairguns.org/GTA/index.php?topic=197608)
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Thanks for the efficiency link.😁
Shimming the original spring I can definitely see it coil bind.
Original spring length is 3.75" and 9 active coils with .064 wire. With the nearly 1.5"s of preload and using shims, will go coil bind.
The springs I chosen are 2.5". This kisses the hammer with little to no preload while maintains the same cocking force as stock spring.
The adjuster is an 8/32 and allows for 3 turns in.
This means that it can be tuned for less than stock power and more than stock power with the port at wide open.
How far and numbers to back it up are coming soon.
Just need to get the springs in.
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Springs finally shipped. Should see them sometime next week.
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Is this the 30 cal std Tim? Good to see you tinkering again!
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Yes. I have the 24" barrel one. I am pretty sure all the challenger platforms are the same.
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I was just curious if you had the standard or long barrel version. I have been contemplating putting a huma reg in mine. Any other tricks like this and the 30 could be a heck of a hunter.
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The reg does sound nice.
Iam just liking the 100+fpe for hunting. Mine has been shooting great at 50 yards.
My hopes are that the new spring and adjuster will increase some efficiency and give a longer flatter ES over 2 or more mags for target shooting and then be turned back up easily for a few shots at max power for bigger game.
The adjuster should really compliment this platform. I think it would be a necessity if it was regged.
Anywho,
I know it's taking me some time but it's coming. I promise.
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Your right Tim it would be needed with the instillation of a reg.
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Prototype parts are made.
Hopefully the spring guide will hold up for some trials with the cut down stock spring until the new springs arrive.
Testing this afternoon 👍.
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Got some pics? ;D
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This afternoon.
No pics of how it's made yet. I have a feeling a bunch of people will want one if it works.
Don't want to get a head of myself yet. Just hoping it will work properly.
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Will it fit the Challenger bullpup .25?
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It should fit all the standard challengers (bolt action ).
First tests at 3k psi with cut down oem hammer spring ( new one not here yet).
850fps at 0 turns and 945 at 3 turns in.
No coil bind and smooth cocking.
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I think it's gonna work😁😁😁
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Very tricky to put it up n the gun. I had to remove the guide and insert the cap,spring guide, and spring as one assembly.
At first I didn't think it was going to get in there but the above worked like a charm.
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Great work Tim. I haven't messed with mine at all since I got it.
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Houston we have a problem.
New springs came in (just now).
0 turn at 3kpsi was 960fps. 3 turns in was 870fps. 2 turns in was 890fps and 1 turn was just at 900fps.
Darn hammer must be bouncing off the valve.
Well,
The system works but just got to get the springs right.
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Following! :D
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This is why guessing blows and math is always there to back you up and put you down in your place.
I was really wanting to get 3 mags at a decent power level but it seems nearly impossible unless your running around 70fpe.Thats not for me with a 30 cal.
Anywho,
I think this will be a little more reasonable/realistic.
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Shot 2 strings using the jsb 45 grains without the spring guide adjuster. I wanted to see what the spring itself would do( the guide adds .125" preload).
890fps to 981 from 3500psi to 2500psi with the port open at max.
So,
It looks like I have the spring rate correct but the length is just a tad too long.
Gonna try to get some more ammo. I have a real strong feeling 60/70 grain is the wheel house for power and efficiency from 50 yards to 100 yards.
To be honest, iam starting to get bored and lose interest because I am liking the spring without the adjustment. But on the other side iam thinking some people may like the adjustment and want to support something like that. Iam just not sure I have it in me right now to go into production for a hand full of (wonderful) gta members.
It would be so easy for me to hand over the drawings and prototype parts for someone to produce it for you guys.
I don't think iam that guy right now.
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1 mag =9 shots at 50 yards from 3500 psi. Great accuracy for me into a 1/4" aluminum swinging plate.
Those jsb's just flatten out completely with such a loud ping of contact.
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Another 30 bucks spent on some neilson 30 cal .303's 61 grain.
Boy I hope they do well.
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Interested to see how those do. I was considering trying some of those but haven't been able to justify it lol. I will if I hear they do well out to a 100. That gun has some power and Me and my buddy were exploding soda cans at 75-80 yards.