Quick hammerspring question

[TheCarFather]

Currently I have an Umarex Origin in 25 caliber, and a Benjamin Cayden in 22 caliber. These are my first PCP guns, and I absolutely love them. Because of the adjustable power settings on the Cayden, I got myself a chronograph so I can log the results.

I just chrono'd my Origin last night with 25.39gr JSB's. Shot from 3200psi down to about 2100psi. FPS peaked around 875. JSB 33.95 heavy's peaked at 775fps. I've watched multiple youtube reviews of the same gun where they chrono and test different pellets. In those tests, they were closer to 950fps with the 25.39's, getting around 50ftlbs of energy. My Origin is only generating 43-44ftlbs max right now.

Would adjusting the hammerspring help bring the velocity up? Since this is my main hunting rifle I want the most energy possible, while keeping accuracy in check. Is it safe to adjust the hammerspring with the gun filled with air, or do I need to degas first? I tried a quick search first and couldn't find the answer, apologize if it's a dumb question.

[PasadenaMike]

Currently I have an Umarex Origin in 25 caliber, and a Benjamin Cayden in 22 caliber. These are my first PCP guns, and I absolutely love them. Because of the adjustable power settings on the Cayden, I got myself a chronograph so I can log the results.

I just chrono'd my Origin last night with 25.39gr JSB's. Shot from 3200psi down to about 2100psi. FPS peaked around 875. JSB 33.95 heavy's peaked at 775fps. I've watched multiple youtube reviews of the same gun where they chrono and test different pellets. In those tests, they were closer to 950fps with the 25.39's, getting around 50ftlbs of energy. My Origin is only generating 43-44ftlbs max right now.

Would adjusting the hammerspring help bring the velocity up? Since this is my main hunting rifle I want the most energy possible, while keeping accuracy in check. Is it safe to adjust the hammerspring with the gun filled with air, or do I need to degas first? I tried a quick search first and couldn't find the answer, apologize if it's a dumb question.

Don’t get caught up on the #s first see How is it shooting on paper ? Those #s your getting are good #s for pellet stability which results in accuracy which results in good shot placement which is what you want with an airgun when your out hunting it’s shot placement that kills game (you only need something like 6 foot pounds placed in a kill zone to humanely kill a squirrel)  You mess with the hammer spring it’ll get louder, you’ll lose shot count……that’s just me

[TheCarFather]

Accuracy is fantastic right now, but I like tinkering with things. I bought the compressor and chronograph so working on them would be easier. The Origin wasn't bad filling with the hand pump. I'd only fill to about 2900psi and shoot down to 2000psi. It would take about 60 pumps to top it back off. That pressure range is where it shoots most consistent as well.

To answer my question, can you adjust the hammer spring with air in the gun, or does it need to be degased? Non regulated.

[PasadenaMike]

Accuracy is fantastic right now, but I like tinkering with things. I bought the compressor and chronograph so working on them would be easier. The Origin wasn't bad filling with the hand pump. I'd only fill to about 2900psi and shoot down to 2000psi. It would take about 60 pumps to top it back off. That pressure range is where it shoots most consistent as well.

To answer my question, can you adjust the hammer spring with air in the gun, or does it need to be degased? Non regulated.

As far as hammer spring adjustment goes you don’t have to degass

[TheCarFather]

Thank you! Also realized I'm an idiot and completely forgot I added a Buck Rail moderator on my Origin, which I assume is lowering the velocity. Trouble is I have the inexpensive chrono from amazon that clamps onto the barrel, or in this specific case the moderator. If I removed the moderator the clamp isn't big enough to fit over the barrel and air tube together. I suppose I could try stacking some books or something to set the chrono on and then shoot through it to test.

[Hawkeye51]

The moderator shouldn't slow you speed much if any, it may change your point of impact some.

[Mr Fluffy Tail]

id guess alot of people 'work' their guns also ie, basic check cleanup and polish in key areas .. that can yield numbers like you quoted also without messing with the hammer .. what can happen with 'just' cranking the hammer down is you lose that 'hump' sweetspot and it just goes hard, but down every shot from the top .. but its easy to see with a chrony, just count how many turns you move it, half a turn at a time is a good checking rate for me anyhoo ... and just to say it and be the black sheep as usual, i havent found running pellets fast to be a disadvantage at all, in fact they shoot just as good or better than a slow pellet in a well sorted gun.. if the 'have' to be run slow to get accuracy, its masking something that needs to be fixed, my experience anyway .. to a point .. pellets will do at least 1050 lol .. they may react to hard wind differently but overall accuracy should be right there to at least that speed ..

[TheCarFather]

I ended up working on my Origin today, and started with measuring a shot string shooting the JSB MKII Heavy's with the gun as it came from the factory. I started with "only" 3000psi and managed to get 26 shots before it fell on it's face. That made me realize the gun was indeed "tuned" down slightly as the manufacturer claims 20 shots from a fill, which is 3650psi. Max FPS stock was 796, entire first mag of 8 never got above 770. Second and third mag was the sweet spot, with a low of 770fps and a high of 796fps over those 16 shots.

Turned the hammer spring in one full turn and got exactly 20 shots when filled to 3000psi. First shot was 802fps, peaked at 829fps on shot number 11. Shots 19 and 20 were 805fps and 801fps, then shot 21 fell off hard down to 652fps.
 
I also chrono'd a string of 26.54gr Hades, which stayed in the 885-900fps range through 2 mags of 16 shots total, starting with a 3000psi fill once again. Lastly I did once more test starting with a fill pressure of 3300psi, still short of the max 3650psi. Went back to the JSB Heavy's, first shot was 755fps and last shot on first mag was 799fps. Climbed the entire first mag and first couple rounds into mag 2 before it leveled off. I did get more shots in total, but it wasn't worth the accuracy drop off on the first mag. I didn't bother adjusting the hammer spring again as 16 shots was the minimum I wanted to retain.

When playing around I'll fill to 3000psi and know I can get a consistent string from 2 mags (16 shots), then top back off. The Origin is my main pesting rig for around the house so I'll keep it around 2500psi for max energy, that seems to be it's sweet spot. Accuracy did not change with the hammer spring increase, which is a good thing since it was grouping well out of the box.

Just wanted to update. 

[TheCarFather]

Well, I spoke too soon. I ended up giving the hammer spring a second turn in, which seems to be the Origin's sweet spot. FPS went up to 925 with the Hades pellet, and still managed 20 shots from a 3200psi fill.

I also took the Buck Rail moderator off and shot through my chrono, velocity didn't change. Maybe 5fps at most. So it went back on. The Origin in 25 caliber isn't very loud out of the box, quiet enough for my backyard shooting. But the Buck Rail moderator did quiet it down even more.

It's so quiet that when I dispatched the latest groundhog this weekend, there was a squirrel standing right next to it. Once shot, the squirrel didn't even run away.

[JimD]

Congratulations on getting results you like from your tuning.  I have one unregulated gun, a Prod, and have enjoyed tuning and shooting it.  I have a chronograph that sounds like the one you are using but I like a different chinese chronograph that I bought from Alli Express.  It mounts to a tripod and not to the barrel.  I don't put it on a tripod, I just rest it on a 4x4 offcut on the rail of the porch I shoot from.  The clamp on chrony changes my POI and group size, the tripod model does not.  So I can shoot groups and measure velocity at the same time.

My Avenger shoots FX 25.4s about 930 fps.  I can only shoot to 33 yards in my backyard and at that distance accuracy is good.  But I shot it once at 100 yards and it was not very good.  I need to shoot it more to decide if I need to detune it.  I want to shoot at 50 yards or more.  Especially in the wind, some report accuracy is not so good well over 900 fps with pellets.  My 4 other guns are tuned to 900 fps or less.  The Prod will not get to even 800 fps with the pellets it likes.