GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: scion19801 on July 09, 2020, 07:07:55 PM
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after having my .25 cal gauntlet jsar super tune hammer spring go out on me, I notice a few things that have me kinda scratching my head.
i tired to keep the RVA and run the factory stock hammer spring spring and aftermarket poppet. LOL, way to hot a setup. 930 fps with modest 1400 psi reg pressure. Wicked loud, and super inefficient. hammer bounce was terrible. up pressure to 1600 psi, bit better but still too hot at 900 fps. Ok So took off RVA and put stock cap and spacer in. efficiency coming back, but FPS still to hot at 920. SO pulled out factory spacer and replace with washer stack. i believe i started with 9 and ended at 6 washers. Upped reg pressure to 1700 psi and hitting 882 fps. NIce. Gun quieted back down and efficiency seems to be back to normal. No noticeable hammer bounce. one more washer added is to much and gets to 910 FPS. 8 shot clip average is 882 FPS. nice.
So what i have noticed is that obviously the factory hammer spring is way too much for the gun, with aftermarket poppet. especially with a 58 gram hammer. have to spec the factory spring to see what its poundage is.
previously with the jsar kit i was getting 890 FPS with 25.4 gr @ 1900 psi. barrel port has been opened to .1875" (3/16").
Main thing i noticed is the gun will make impressive speed at lower reg pressure, but become wickedly inefficient. As reg pressure was increased FPS dropped off and efficiency came back.
I noticed that if i was to run 33.95 then my best possible setup would be to bump reg pressure up to 1900 psi. without changing the way the hammer spring is currently setup. for 25.4 gr the 1700 psi seems perfect.
What i've learned and noticed is quite interesting and baffling. I had always thought that you need more hammer spring to drive a heavier pellet, and less for a lighter one which the RVA give you that possibility, being adjust for different weight . But on the other side moving reg pressure around is another way to to adjust for as well, when an RVA isn't available.
I read through BOB's thread on hammer weight versus FPE, or Pellet weight. but can't wrap my head around the concept on how to figure out what would be the best way to optimize for both Pellet weight and efficiency.
I know that the .25 cal gauntlet has a 58 gram hammer. and soon to put the RVA back into play once my replacement 22 pound springs arrive. what would the ideal pellet weight/ slug weight be for the setup up?
Was always my thinking that as you increase reg pressure for the heavier lead, you had to generally increase hammer strike as well. But it seems this could not be the case. Especially when i noticed that even at a low reg set point of 1400 psi i was seeing excessive speed, but it was due to way too much hammer strike wasting air and hammer bounce. but if the hammer spring was adjusted properly, you could still get the same speed at lower set point couldn't one?
Just some of the things i noticed while being force to put a factory hammer spring back into a gauntlet after a Jsar super tune kit hammer spring lost tension. and get the gun back to being usable while replacements arrive.
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Don’t have one, just 👂 , interested in this conversation.
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To bad no one makes a lighter hammer for the gauntlet. It's a heavy hammer. An ssg helps dramatically when tuning at lower reg pressure. Will keep the hammer bounce at bay.
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lighter hammer spring, and more free play works also. harder to be consistent thought when more free play is added to the setup. i did an 8 shot clip at current setup and got
882 average fps
10 fps for extreme spread
and a standard deviation of 3 FPS
Free float/play length of 1/8" +/-
Yes that has been my next thought on trying to see what a lighter hammer would do for the .25 cal, but would be awesome to have some way to have it be an adjustable weighted unit, to dial it right in.
My thoughts would be that the adjustable weight would have to be on the back side (rear of the hammer) that way the distance between the striker face and valve stem would stay fairly constant. A spread sheet that i found on AGN has a recommended hammer weight of 28-46 grams. i think one around 37 grams would be just about right. it would definitely be a faster cycle rate, and probably improve accuracy even more.
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Watching this thread.
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what would be a good material to use if i was able to get one made up. need to get some measurements the next time i tear down on the hammer. and i highly doubt that i could get 21 grams off the original without it being compromised.
depending on my measurements and how accurate this spreadsheet program is on its number, but... it says that a 37 gram hammer would need a 17 lb spring, and be moving at 20.8 fps over .7" of travel and have a 3.9 ms lock time.
now with the 58 gram hammer would need only 10.5 lb of spring, and would be moving 15 fps over .7" of travel and have, with a 5.4 ms lock time.
hmmm... how would i figure out the lock time having a 22 lb spring driving the 58 gram hammer??
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Hopefully with that heavy of a spring the cocking effort still isn't too bad. I run a 15.7# spring in my 30 b-rod and once I put the sidelever action on it I enjoy it a lot more. With that heavy spring and only at 1 turn in it was a PITA to cock.
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my cocking effort isn't to bad currently. with the factory hammer spring parts in, its tough. but with the hammer spacer removed and a washer stack in place its lighter than factory. need to order to mds rod, so i can change the washers out and put a spacer in out of it.
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Thats good the cocking effort isnt too bad. Hopefully it remains manageable once you install the heavier spring. I know with the 15.7# spring it wasnt very easy to cock my 30.
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according to hajimoto the jsar tune kit (RVA setup) for the .25 cal gauntlet is a 22# spring. I just bought a 10 pack of some that were close. Plus not sure, but hoping my decision to go a touch longer doesn't bite me. i went with 2.5" spring.
you ca read that thread here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=175685.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=175685.0)