FD-PCP Hammer n Valve mod test

[avator]

I anticipate some feedback from this one but I am merely trying things from my understanding of the things that more experienced and better equipped modders are doing. My FD-PCP is in .22 and CPHP 14.3 pellets were used. I have it on good authority that back in the day a felt tab with a hole cut in the center for the valve stem was stuck to the 1/2" spacer between the valve and the hammer giving similar results as the bstaley o-ring mod. This spacer is held in place by the first of the 2 screws in the bottom of the receiver. (closest to the trigger group) I started out with the felt about 1/4" thickness and shot a string of 23 shots in the mid to low 700's. I am after a string of about 20 shots within the high 800 to mid 700 where my POI drops at 25 to 30 yds. Adjusting the power setting from 2 turns in from all the way out to flush with the locking nut didn't improve those results significantly. FPE is not much of a factor to me because my main use is target shooting.
   My gun originally shot from upper 800, belled to 915ish down to mid 700 before POI drop and yielding 17 shots.
 Next I thinned the felt to 1/8". Filling the gun to 1600psi and the power adjuster 1 1/2 turns in from all the way out gave my best results yet which are shown below with my string.
 In conclusion, I was happier before the mod and will return the gun to it's previous state.

[Donny]

good info here, thanks. ive been thinking of the o-ring mod myself but been waiting for more forum feed back

[avator]

I'm almost positive the o-ring mod will produce much better results than a piece of felt, the felt's durability is extremely uncontrollable until maximum compression is reached.

[Donny]

so its as simple a sticking an oring between the valve and hammer? you know which oring size?

[rsterne]

You can try three #113 O-rings and see how it works.... Without an adjustable striker length like in the MRod or PRod if you don't like the results and want to experiment, you will have to either use shims to add thickness to the O-ring stack and/or use a "backer ring" which is half thickness to make the stack thinner.... or possibly sand one down....

Bob

[avator]

Thank you Bob, I half expected you to get in on this one.

[mikeiniowa]

adjustable striker...hmmmm...it could be done with a little work...1/4 inch grade 8 bolt with head cut off...drill and tap striker...set screw to hold in place...much like the striker in the B-50....wonder how much length of change would be needed???   

[avator]

Oh Lord, now look what you've done Bob... lol

[BrewCityMusic]

I thought of a similar design, Mike, when I was chasing the demons in my FDPCP last week - my thought was that it could give a little more valve time without having to start interfering with cocking, etc like adjusting, shimming, etc can do on the other end of the equasion - the issue I kept coming up with though is how to adjust it, if it was a hex set screw the hole for the wrench would undermine the whole concept, a slot would likely get deformed or mess up the valve stem over time. What about using a hex head that was smaller than the overall striker diameter, but leaving the head intact and cutting the same thickness off the striker and proceeding as above from there? Net result would be that at full "in" the striker length would be the same as stock, turning from there would increase the length?

[rsterne]

If I were going to make an adjustable striker, I would go from the stock length SHORTER to increase the hammer travel, but then I'm a power hog.... *LOL*.... Realistically, to allow tuning with the bstaley O-ring buffer, you only need 1/8" of travel as the O-rings are 0.102" thick and you can either remove or add an O-ring if you run out of travel.... Unfortunately, with the cocking pin in the way you would have to pull the hammer out to make the adjustment, you can't work through the center with a small allen-key like on an MRod.... I thought about modding my hammer but decided it was just as easy to shim the O-ring stack, since you need to pull the hammer anyway....

Bob

[mikeiniowa]

I looked at it and came to about the same thoughts as Bob, it can be done but would be such a pain to adjust it wouldn't be worth the trouble unless you wanted to do it for yourself...

[avator]

Picked up some 113 Buna O-rings yesterday. I stuck 3 of them in the gun but I don't know if I'll get a chance to play with it til tomorrow afternoon. Going thru a major model change in the auto industry and work is a bit hectic. One thing that baffles me is the difference in these guns. For example, my gun takes 1600 psi before valve lock begins, Betty Lou's barely gets to 1400. This is based on my old eyes and a small 3000psi guage. It's pretty close tho. I'm definitely going to get another one of these things before they are gone.

[avator]

Took a minute to fill the gun a run a string this morning. I don't really have time to chrony so this will be just an observation. With the power screw at 2 turns in from all the way out and 3 #113 Buna O-rings unmodified. If felt like the bell smoothed out a lot but no shot count increase. Shot 16 just dropped off POI at 23yds. I know this is not very useful information without physical data and I will be posting as I continue. My gun is LOUD without these O-rings but this string seemed somewhat quieter.

[avator]

Got out of work early this afternoon so I couldn't resist pulling the chrony out. To make a long story short, I made a few adjustments and settled on the setup that serves my purpose. My main objective is target shooting at 25yds with 20 shots in the 800 fps range. I've read every post on the FD-PCP that has been posted. I've followed Mr. Sterne's and Mr. Stalwart's mods and results with earnest. I think I have achieved exactly what I set out to do and the guy behind the keyboard before you now is a happy dude. This little $100 airgun is to me what the Red Ryder must have been to the kid that never shot his eye out. Guys, buy the gun in .22. Clean the barrel. Drop in 3 #113 buna O-rings. set the power screw at 1 1/2 turn in from all the way out. Mount a scope on it. Fill it to 1600psi (sorry Bob) if it will go. Feed it 14.3 CPUM tinned and enjoy this gun. Every shot in this string hit where I sent it except the last one which is where I stopped and refilled at 900 psi. I blame the up and down fps throughout the string on tinned pellets or the fact that the tune really hasn't settled in yet. Opinions are welcome.

[rsterne]

That looks like a solid 20 shots (except #2 and #4) at 21 FPE within about a 4% ES.... Congratulations !!!

I would think the first 20 shots are from 1600 down to about 1100?....

Bob

[Donny]

i feel stupid for asking but is there a simple diagram or pic of were these o rings are installed

[avator]

Thank you. Imagine my delight. I'm not going to do anything else to this one other than keep it clean, lubed and fed. Tomorrow I'm going to order another one in .22 + a .22 barrel to make Betty Lou's swappable (is that a word?) I'm going to stretch this one out in .177. I already have the .177 barrel. I'm going for 30 shots in the 800's with a custom stock finish and an "on the fly" power adjustment. This might prove to be better for me than Lincoln Logs, Erector Sets and Rock em Sock em Robots.

[crosman999]

John B +1 

[avator]

Thanks John, I was hoping someone would jump in with some pics for Donny. I've been so excited about this thing that I forget to take pics. I ordered another one this morning and I plan to take my time because we already have 2 nice shooters. Altho I ordered it in .22, I plan to set it up in .177 with a nice long flat string.