Backstory
I received a “new to me” rifle recently. I was finally able to get out last evening and shoot it after taking a while to decide on a riser and scope and the right sized rings. It was getting late, so I only shot just over 60 rounds (30 with AA and 30 with HN 10gr pellets). The thing I noticed was how quickly the speed was dropping over the chrony. I was surprised that after every 10 shots, the speed was dropping by about 10 FPS. Went from 926 down to 884 over around 35 shots. Oddly enough, the pellets were doing pretty well with the huge spread. Just checking rifle out for first time and sighting in scope, so not looking for groups yet.
I remember the owner saying he would fill up after about 30 shots in a match but it could go more. So I shot him a message to confirm I heard correctly, and he confirmed the 200bar fill pressure and shots. Something still seems off. Most of my rifles have come from the dealers set up like I wanted and I never had to deal with this. I did have to tinker with a used Impact, but it never did this. I learned how to tune from my first Leishy, man that thing was easy! I understood the need for balance of the reg and hammer, but never did long strings to see what I am seeing.
Purpose of the story:
So I decided to study up on what could cause this particular trend. First couple results were directly from our friends at HAM from 2018 and 2019. Found what I needed. Having read many of the forums and watched setup videos and done minor tinkering over the years, the theory and the tuning methodology is exactly what I expected around finding the knee and backing down 5%. The really cool part were the graphs and the explanations of exactly why we take those steps. Seeing the graphs show you what happens when you don’t get the tune right is exactly what I needed!! Thanks HAM!! It looks like my shot string, and being a visual person, this is super helpful! I think this will help me tremendously when I go back out, as now I have an idea of what might be off and why. I like to know “why”, not just “what”.This will get me to the end much faster.
hardairmagazine.com
hardairmagazine.com
More Details if curious
The rifle is a RAW TM1000. I didn’t even know where the hammer spring adjuster was, because I wasn’t going into this planning to tinker at all! I had to look it up. Looks like this is going to be really easy to fix the spread issue with just hammer spring adjustments. It appears that the hammer spring might just be too high. I will still have to figure out what speed the pellets like in this barrel, so there is still a little work to do, and I have different pellets to try out. I will shoot it a little more and document what I find. I’m hoping this gets me some more shots too, because 30 didn’t seem like a lot.
The AA’s started at 926 and finished at 884 after about 36 or so shots. Each 10 shot average dropped about 10 FPS as it went.
The HN’s were tighter at load and shot much better (both brands were labeled 4.52). They started at 919 and had a very similar drop pattern of 10FPS per 10 shots down to 886 around 30 shots.
I couldn’t find conclusive evidence on speeds that the 10gr pellets prefer, but most seem to say 880-900, so that is right in the wheelhouse of dropping the hammer spring back 3-5%. I sure hope that is the ticket!! I will go ahead and shoot some groups first, and see how this current tune is grouping, but I have to think that spread is going to have some impact at the longer 50 yard FT targets.
Thanks HAM for all the good work you do for us!
I received a “new to me” rifle recently. I was finally able to get out last evening and shoot it after taking a while to decide on a riser and scope and the right sized rings. It was getting late, so I only shot just over 60 rounds (30 with AA and 30 with HN 10gr pellets). The thing I noticed was how quickly the speed was dropping over the chrony. I was surprised that after every 10 shots, the speed was dropping by about 10 FPS. Went from 926 down to 884 over around 35 shots. Oddly enough, the pellets were doing pretty well with the huge spread. Just checking rifle out for first time and sighting in scope, so not looking for groups yet.
I remember the owner saying he would fill up after about 30 shots in a match but it could go more. So I shot him a message to confirm I heard correctly, and he confirmed the 200bar fill pressure and shots. Something still seems off. Most of my rifles have come from the dealers set up like I wanted and I never had to deal with this. I did have to tinker with a used Impact, but it never did this. I learned how to tune from my first Leishy, man that thing was easy! I understood the need for balance of the reg and hammer, but never did long strings to see what I am seeing.
Purpose of the story:
So I decided to study up on what could cause this particular trend. First couple results were directly from our friends at HAM from 2018 and 2019. Found what I needed. Having read many of the forums and watched setup videos and done minor tinkering over the years, the theory and the tuning methodology is exactly what I expected around finding the knee and backing down 5%. The really cool part were the graphs and the explanations of exactly why we take those steps. Seeing the graphs show you what happens when you don’t get the tune right is exactly what I needed!! Thanks HAM!! It looks like my shot string, and being a visual person, this is super helpful! I think this will help me tremendously when I go back out, as now I have an idea of what might be off and why. I like to know “why”, not just “what”.This will get me to the end much faster.
Tuning Regulated PCP Airguns - Hard Air Magazine
The first thing you need to understand when tuning regulated PCP airguns is that for any PCP there is a maximum velocity for a given pellet,
hardairmagazine.com
Using Hammer Strike to Control PCP Power - Hard Air Magazine
Actually, with a regulated PCP, your job to control PCP power is simpler, because the pressure is fixed (until it drops below the regulator setpoint).
hardairmagazine.com
More Details if curious
The rifle is a RAW TM1000. I didn’t even know where the hammer spring adjuster was, because I wasn’t going into this planning to tinker at all! I had to look it up. Looks like this is going to be really easy to fix the spread issue with just hammer spring adjustments. It appears that the hammer spring might just be too high. I will still have to figure out what speed the pellets like in this barrel, so there is still a little work to do, and I have different pellets to try out. I will shoot it a little more and document what I find. I’m hoping this gets me some more shots too, because 30 didn’t seem like a lot.
The AA’s started at 926 and finished at 884 after about 36 or so shots. Each 10 shot average dropped about 10 FPS as it went.
The HN’s were tighter at load and shot much better (both brands were labeled 4.52). They started at 919 and had a very similar drop pattern of 10FPS per 10 shots down to 886 around 30 shots.
I couldn’t find conclusive evidence on speeds that the 10gr pellets prefer, but most seem to say 880-900, so that is right in the wheelhouse of dropping the hammer spring back 3-5%. I sure hope that is the ticket!! I will go ahead and shoot some groups first, and see how this current tune is grouping, but I have to think that spread is going to have some impact at the longer 50 yard FT targets.
Thanks HAM for all the good work you do for us!
