Top Hat O-ring and FPS
I am in comparison to most of you guys a very novice air-gunner. I have now had my Condor SS in .22 for 2 months. I had problems with my end cap coming out due to the set screw. ( poor design). Sent the rifle back to airforce and they took care of it. Great customer service in my case. Just got my gun back and was ready to start testing again.
Before I sent my gun back for repair I did some chrony work.
25 yard range, 3000 psi, power wheel on 3 Shooting Barracuda 21.14 round nose
Everything stock on the Condor my first ten shots had an average of 1027 fps. The pressure dropped from 3000 psi to approximately 2450. The accuracy was ok but I wanted to do more testing. This gave me approximately 37.61 ft/lbs of energy.
Today I did the same test but I installed an o-ring on the top hat. Major result differences. Once I re-zeroed I shot nine 5 shot strings so I could monitor the pressure drop and the fps drop.
My first five shots averaged 665 fps. Pressure in the tank dropped to approximately 2975 psi
Second five averaged 666fps. Pressure in tank dropped to approximately 2900 psi.
Third averaged 682 fps. Pressure dropped to approximately 2850 psi.
Fourth averaged 680 fps. Pressure dropped to approximately 2775 psi
Jumping to strings 8 and 9.
Eight averaged 697 fps. The pressure in the tank was approximately 2580 psi.
Ninth averaged 700 fps. Ending pressure in the tank for my test was approximately 2550.
The calculated energy dropped 39% to 22.91 ft/lbs
This is still enough for hunting but I do not know about longer range accuracy. I want something to be able to reach out about 75 yards.
With my superior observation skills ,(LOL), I quickly noticed that the o-ring was certainly helping in the air usage arena.
Having more pressure left after 45 shots (2550) compared to 10 shots with no o-ring on the top hat (2450 psi) should make everyone want an 0-ring or adjustable top hat.
So, my first question is this. Maybe Tony has an answer. How long with this 0-ring last. FPS is going up so repeated shots are compressing the o-ring. I have to say I was extremely happy with the results although I would like a little more velocity.
Second question…. If I turn up the power wheel will I indeed get more fps? Third….What fps would you recommend for 75 yard shots?
Fourth….If I purchase a TT tophat will I get similar results? I like the idea of TT tophat rather than relying on a piece of “rubber” to help control the air flow.
Hopefully I can duplicate this test over the weekend. My last ten shots gave me a littler under 1/2 ” group at 25 yards.
Thanks for any insight…..
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One thing that you are seeing is that the o ring is giving you very consistent results. Besides limiting how much the valve opens, it is also helping to reduce bouncing which can cause the valve to open up a little and waste air.
Diabolo pellets are designed for subsonic flight. It will vary from gun to gun and pellet to pellet, but you will likely get your best accuracy in the 800-950 FPS range. You might try a slightly thinner o ring to increase your velocity, that is after you determine your optimum fill pressure.
You noticed that your velocity was increasing as your pressure was decreasing. That is because your fill pressure was likely above the optimum fill pressure (OFP) of that particular valve and you were experiencing “valve lock” where the internal pressure was hindering the opening of the valve. The valve on my Talon SS has an OFP of 1800 PSI. Most are higher than that and if you know what you are doing and/or are very brave/foolish you can adjust it.
To determine the OFP, take a tin of cheap pellets, fill your tank to 3000 PSI, turn your power adjustment all the way up and start shooting across your chrony. Very likely you will see your velocity keep going up for a while and then it will peak and start down. Check the pressure in your tank and try it again. You will likely see it peak at about the same velocity. Check your pressure again. It also will likely be close to the same. That is your OFP. If the top of your curve is flat enough, you can fill a little higher and get a greater shot string.
The QCTH is a must have if you want instant changes from plinking to hunting, I use mine on a .25 Condor.This is the best money on an option that I have spent on my rifle.
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Spoke with Tony today and ordered his top hat.. More testing to come. I will post actual fps using my Condor SS in 22 caliber.