My P35 in 25 caliber was my first bullpup. I liked it so much I bought a 177 and 22 as soon as Krale got them back in stock. I shot it with H&N FTTs which are only 20 grains for about the first year. Only about 32 fpe but it worked fantastic on squirrels. It still has my most of any of my airguns with 18. All but three passed through. Only two ran at all, both shot in the middle of the chest with the pellet stopping under the skin in the rear. They did not go far.
In March and April this year I worked on retuning the gun to more like 50 fpe. I got a bigger plenum sold by Xtreme airguns which helped a lot. In early April I had it shooting barely over 800 fps. I found it to be challenging since there is no gauge to tell you where you are on the regulator and the hammer spring will not open the valve if you turn the regulator up too far. But it was working fine and I put it in the coffee table and started playing with other guns.
July 17th I pulled it out to shoot expecting it to have a little more power from the warmer weather. It was about 92 F that day. To my dismay the velocity was under 600 fps. Based upon earlier experience I was pretty sure the hammer spring was no longer able to open the valve. Turning it up as far as possible and still cock the gun only got me a little over 600. So I turned the reg down about 1/4 turn and got to about 760 fps. I figured I could get a few more fps but didn't want to get too close to another problem so I left it there.
Yesterday I took it out of the coffee table to fix a slow leak. I guessed it was either the one way valve O-ring or the big O-ring on the gauge end of the airtube. When I got it apart they looked good so I just put a little more silicone grease on them and reassembled. It seemed to be holding air but I let it sit overnight and started shooting it today. The first couple shots were back down under 600 fps but then it jumped back up to about 800 fps. I started shooting when it was about 72 F and shot my last shots near our high of 84 F. I don't know why it went down from where I left it so much and then jumped up like that. I shot it around 25 shots and it stayed in the 795-820 fps range. Mostly over 800. I decided the hammer spring was probably still a little high and turned it down 3/4s of a turn in 1/4 turn increments. That only dropped velocity about 5 fps each 1/4 turn. I decided to leave it at 1/2 turn less than I started the day. It was about 79 F when I did the tuning. I shot three shots at 5:30 when it was about 84 F. Velocity was 807, 804 and 795. Not sure why it fell each shot but I saw swings this big in the longer string earlier in the day. Now my plan is to test next week when the temperature will be in the upper 90s. I'm hoping this tune continues to work.
The JSB Heavies MKII this gun prefers weigh about 35 grains in the tins I have so I am right at my target 50 fpe. If the tune will work in a little hotter weather I think it's set. But I'm still unsure why the velocity jumped up today almost 200 fps with no change to the regulator or hammer spring. Maybe there was something slowing the hammer down that went away? Regardless of why I'm glad it working well now. I also find it curious that I'm getting 800 fps with a lower regulator pressure more easily opened by the hammer. The velocity falls slowly when I come off the reg in this gun and my other P35s so it makes it harder to know exactly what the regulator setting is. I did not go below 790 fps until the tank pressure was about 120 bar. The regulator could be as low as 125. Or could be more like 135 with it just falling very slowly as it comes off. Either way power doesn't go down quickly and I could clearly use it down to 120 bar or even a bit further. I'll need to do a long string to really know shot count but my estimate based upon how it decreases is I will have about 40 good full power shots.
Leak also seems fixed and I also fixed a little issue with cocking. If the velocity stays up around 800 next week in the warmer weather I think I will have my tune for this gun.
In March and April this year I worked on retuning the gun to more like 50 fpe. I got a bigger plenum sold by Xtreme airguns which helped a lot. In early April I had it shooting barely over 800 fps. I found it to be challenging since there is no gauge to tell you where you are on the regulator and the hammer spring will not open the valve if you turn the regulator up too far. But it was working fine and I put it in the coffee table and started playing with other guns.
July 17th I pulled it out to shoot expecting it to have a little more power from the warmer weather. It was about 92 F that day. To my dismay the velocity was under 600 fps. Based upon earlier experience I was pretty sure the hammer spring was no longer able to open the valve. Turning it up as far as possible and still cock the gun only got me a little over 600. So I turned the reg down about 1/4 turn and got to about 760 fps. I figured I could get a few more fps but didn't want to get too close to another problem so I left it there.
Yesterday I took it out of the coffee table to fix a slow leak. I guessed it was either the one way valve O-ring or the big O-ring on the gauge end of the airtube. When I got it apart they looked good so I just put a little more silicone grease on them and reassembled. It seemed to be holding air but I let it sit overnight and started shooting it today. The first couple shots were back down under 600 fps but then it jumped back up to about 800 fps. I started shooting when it was about 72 F and shot my last shots near our high of 84 F. I don't know why it went down from where I left it so much and then jumped up like that. I shot it around 25 shots and it stayed in the 795-820 fps range. Mostly over 800. I decided the hammer spring was probably still a little high and turned it down 3/4s of a turn in 1/4 turn increments. That only dropped velocity about 5 fps each 1/4 turn. I decided to leave it at 1/2 turn less than I started the day. It was about 79 F when I did the tuning. I shot three shots at 5:30 when it was about 84 F. Velocity was 807, 804 and 795. Not sure why it fell each shot but I saw swings this big in the longer string earlier in the day. Now my plan is to test next week when the temperature will be in the upper 90s. I'm hoping this tune continues to work.
The JSB Heavies MKII this gun prefers weigh about 35 grains in the tins I have so I am right at my target 50 fpe. If the tune will work in a little hotter weather I think it's set. But I'm still unsure why the velocity jumped up today almost 200 fps with no change to the regulator or hammer spring. Maybe there was something slowing the hammer down that went away? Regardless of why I'm glad it working well now. I also find it curious that I'm getting 800 fps with a lower regulator pressure more easily opened by the hammer. The velocity falls slowly when I come off the reg in this gun and my other P35s so it makes it harder to know exactly what the regulator setting is. I did not go below 790 fps until the tank pressure was about 120 bar. The regulator could be as low as 125. Or could be more like 135 with it just falling very slowly as it comes off. Either way power doesn't go down quickly and I could clearly use it down to 120 bar or even a bit further. I'll need to do a long string to really know shot count but my estimate based upon how it decreases is I will have about 40 good full power shots.
Leak also seems fixed and I also fixed a little issue with cocking. If the velocity stays up around 800 next week in the warmer weather I think I will have my tune for this gun.
