I followed some of the directions today making mods to my .22 cal 850. I did the barrel port and loading breach mods. Opening the transfer port to 5/32". I also replaced the hammerspring with a suitable spring from the local hardware stoore. The selected spring was approximately 3/16 short than factory. I used a small hex head screw as a spacer at the hammer side of the spring to get a nice fit.

When finished I charged the gun with an 88 gram cylinder and set it out on my shooting bench for about 15 minutes before shooting over the chrony. Below is the chrony results.

14.3 grain JSB express. Temperature = 85 today.

742.1
739.9
741.7
743.6
744.3
743
741.5
744.6
742.3
745

Avg:742.5 fps Ft.lbf: 17.5

This is much, much better than I xpected or hoped for. I would have been happy with 680 fps!!

Now for the questions.

1.) I received my B&A AS to PB adapter today. Monday I will Drill out the AS end of it to Roalds suggestion in my other thread under information (Beleive he said 13/64). Question is, once you install a 9 oz. tank, do you leave it installed until empty or is it best to uninstall while not in use?

2.) I have the .PDF download of the hammer spring modification. And while working on the gun I noticed a discrepency between the picture in the .PDF and what my gun looked like internally. The following picture is as the gun looked with stock hammer spring installed.


In my gun the hammer and valve stem do not make contact when the gun is unstressed. In the gun in the .pdf these parts are makeing contact. Seems to work ok, but was just wondering if I am missing something here?

Matt H.

I say great job on the .22. As far as the PB tank goes just leave it on there until you are ready to refill. Its just a big ol airsource can ya know? and you leave those on there until they are out of gas so same applies for the PB tank. As far as the pics go it kind of looks like your hammer spring is a little short. I cant remember for the life of me what length the spring is that Roald is using these days he would be able to answer you this. But I would say if it aint broke dont fix it.....or use a bigger hammer(just kidding). Seriously I think you did a good job with good numbers to prove this.

John

The 850 Resource

Thanks for the info and kind remarks. I enjoyed working on this gun. And like you I figure if it ain't broke don't fix it.

".....or use a bigger hammer(just kidding)" LOL. Sounds like percussive maintenance to me!!

Matt H.

Great tune Matt thanks for the numbers and info.
The two pins only touch once the hammer spring in pre-loaded.
You did good!

The 850 Store