I was looking for a high shot count , lower powered .177 mainly for shooting paper at my property. While browsing through one of our Canadian dealers I found an HPA converted 850 in a custom wood stock. I took a chance and I arrived yesterday.
Right from the unboxing I knew I was going to enjoy working on this one. The stock made by an unknown maker, has the best grain of any of my current stable. The cocking knob was loose in the box and the box has a hole punched through it . Not a big deal as I simply glued the knob back on and used a c clamp to press it back together.
Once that was taken care of I wanted to get a baseline of what it was set at. It came with no air in it and when I tried to fill I immediately had the dreaded hiss. The regulator was leaking between sections. I luckily had spares from a few old bottle conversions I did in the past. Once filled , I loaded up a mag full of JSB 7.87 pellets. 900 fps average. Way too hot for what I wanted.
Now for the fun part. I promptly replaced the bottle with a 22ci /360cc bottle I had on hand . Tested the regulator and it was set at about 1250psi. I removed a few shims ( it’s a spring type regulator) and got the regulator down to about 1000psi. I then shortened the barrel from the 24” length down to 18” . About an inch past the bottle. This brought the overall length to 37 1/2” . Loaded up another magazine , and started tuning by finding the max velocity with the existing hammer spring. Maxing out at 780fps which I think is pretty healthy for the 1000psi. I opened up the action and had a look at what I could do to tame it down to 750 or so. The hammer was removed and it weighed a whopping 62 grams. I knew I could make it a bit lighter by drilling some speed holes in it. I got it down to just shy of 50 grams ( still heavy ) and moved onto my spring assortment. I found a single spring in my stash that I thought might work. Put the rifle back together and now it’s shooting at 730 for average . So just shy of 10 fpe. And just about right for my intended purpose . Mounted a Vector marksman 10 x 44 fixed power scope to keep the weight down. Here are a few pics of the rifle. I have a few more items I’d like to address, like the trigger, somehow fitting a gauge and maybe try my hand at stippling the grip and forend as it’s pretty slippery when shouldered.
Right from the unboxing I knew I was going to enjoy working on this one. The stock made by an unknown maker, has the best grain of any of my current stable. The cocking knob was loose in the box and the box has a hole punched through it . Not a big deal as I simply glued the knob back on and used a c clamp to press it back together.
Once that was taken care of I wanted to get a baseline of what it was set at. It came with no air in it and when I tried to fill I immediately had the dreaded hiss. The regulator was leaking between sections. I luckily had spares from a few old bottle conversions I did in the past. Once filled , I loaded up a mag full of JSB 7.87 pellets. 900 fps average. Way too hot for what I wanted.
Now for the fun part. I promptly replaced the bottle with a 22ci /360cc bottle I had on hand . Tested the regulator and it was set at about 1250psi. I removed a few shims ( it’s a spring type regulator) and got the regulator down to about 1000psi. I then shortened the barrel from the 24” length down to 18” . About an inch past the bottle. This brought the overall length to 37 1/2” . Loaded up another magazine , and started tuning by finding the max velocity with the existing hammer spring. Maxing out at 780fps which I think is pretty healthy for the 1000psi. I opened up the action and had a look at what I could do to tame it down to 750 or so. The hammer was removed and it weighed a whopping 62 grams. I knew I could make it a bit lighter by drilling some speed holes in it. I got it down to just shy of 50 grams ( still heavy ) and moved onto my spring assortment. I found a single spring in my stash that I thought might work. Put the rifle back together and now it’s shooting at 730 for average . So just shy of 10 fpe. And just about right for my intended purpose . Mounted a Vector marksman 10 x 44 fixed power scope to keep the weight down. Here are a few pics of the rifle. I have a few more items I’d like to address, like the trigger, somehow fitting a gauge and maybe try my hand at stippling the grip and forend as it’s pretty slippery when shouldered.
