Hello. I've added a new hobby by jumping into the PCP world. I've had a few airguns in the past, but this is the first PCP. I chose the bullpup in .22, and added a DonnyFL FX.
I'm one of those strange analytical type people, and for me experimenting and fiddling is a huge part of the fun. I'm new to PCP, but not to firearms, and I already had a chronograph so I started immediately. I don't expect much of what I am doing is novel, but since I am doing it and analyzing the results, I figured I would share. I appologize now for my tendency to be longwinded.
While I do have a science background, I am in no way an expert on this, so some of my ideas/conclusions may be way off. They are just how my thoughts are going with what I am seeing. Please chime in if you have a more accurate understanding.
I should also explain that I am frugal by nature. Being frugal, I don't shoot my firearms as much as I would like because of the cost, hence some of my interest in PCP's. Being frugal, I am also interested in what I can do with readily available and cheap 14.3gr Crosman Premier pellets (I like that I can get them at any Walmart). This at least will be my starting point. I may end up trying nicer and heavier pellets or slugs later, but all that I show here is with 14.3gr Crosman Premier (and shot indoor). I will probably also do much of my shooting in my yard, so not much longer than 25 yards typically.
Out of the box, the regulator appears to be set to 2900-3000 (hard to tell exactly). This seemed a bit higher than I expected, but that's where it was. Later checking found the hammer spring to be ~1.75 turns clockwise from the lowest setting. After shooting a few strings, I filled it to ~4200 psi and recorded a string down to ~800 psi. These were done in 10 shot strings and I checked the fill pressure after each.
The pressure estimation is an extrapolation from the reading after each 10 shot string. I found it interesting that it was a very consistent pressure drop per shot (25-30 PSI per). The other ting I found that surprised me was the how consistent the shots were even after the pressure was below the regulator setting. The first 45 or 46 shots should have been on the regulator (~2950 PSI). After the fill pressure dropped below that there were another 30 shots before the FPS started dropping. My assumption from this was that "overgassed" (not sure what the proper term is), by which I mean that a good bit of the air released for each shot is not actually being used to accelerate the pellet (perhaps being expended after the pellet has left the barrel). Assuming that this is true, I am potentially loosing efficiency (and shots). Over that string of 75 shots, I averaged 1004 FPS and 32 FT-LBS, which is more than I think I would want to shoot for. I'm thinking upper 800's and around 25 FT-LBS with 14.3 gr pellets would be a good area to aim for.
Before messing with the regulator, I wanted to see what I could do with the hammer spring adjustment. Maybe it would be possible to get back the inefficiency by dropping the hammer spring tension (and not releasing more air than is used to accelerate the pellet). Checking what it was set to out of the box, it was ~1.75 turns (from all the way counter-clockwise). Here is what I got (10 shot groups at each setting).
It looks like dropping the hammer tension, isn't gaining me back the wasted air pressure (at least not entirely), since we are dropping in FPS with any adjustment down. Adjusting the FPS downward is good, my guess is that even if I went down to 0.5 turns (920 average FPS). I would still find that the shot string may stay level even after the pressure dropped below the regulator setting (wasting air pressure presumably at higher pressures). Next step - adjusting the regulator!
I figured I would start out with AEAC's "eco tune" (1400 PSI, 1.5 turns on the hammer spring). AEAC's video is awesome by the way. This is where things started to be a little strange.
I followed the instructions on adjusting the regulator down (degassed and turned clockwise to the limit and back 1/4 turn. When I pumped up the gun again, this gave me a regulator pressure of ~1900 PSI. Not knowing exactly how the regulator adjustment works, I don't want to try to back up that 1/4 turn more, so I started me experiments with the regulator at 1900. Does anyone know how I would actually go lower?
I decided to try different hammer spring settings at this new regulator pressure, and got the opposite of what I expected (10 shot groups at each HS setting).
This was opposite of what I expected, and I will admit I checked the manual multiple time to make sure I was not getting my hammer adjustment backwards (I wasn't). I stopped for the day and looked at the data a bit. It seems to drift down steadily, with the hammer spring having no effect at all. Here is another view of all the shots.
In this graph, I just show the data from all the shots, instead of binning them by hammer spring setting. It looks to me like the hammer spring setting has absolutely no effect, and the shot string is just decreasing downward at a steady rate. The vertical lines on the graph show where each 10 shot string ended (and the hammer was adjusted). This also showed what assume is the regulator creep. The first shot in every magazine is the highest FPS, sometimes with a very noticeable jump. I assume that this is a creep up in pressure in the time I take to save my chronograph data, reload magazines, check pressures, etc. Is this worse creep that people normally see? I noticed that when the out-of-the-box regulator setting was used (~2950), I could check the gun after it sat overnight and the regulator pressure could be as high as 3200 (but drop back to the ~2950) after dry-fire).
To make sure this was not all some sort of mistake, repeated the experiment the next day, but used 5 shot groups and changed the hammer spring between 1 and 5 turns. (the last two shot strings were 10 shots at 0 and 1 turn on the hammer spring).
Effectively the same result. Hammer spring adjustment seems to have no effect, I see as steady decrease in FPS, with an even more notable spike in the first shot of a string (after pause in shooting).
So, what are peoples thoughts?
- How would I get a regulator pressure below what I got (~1900) since I only turned out the adjustment the 1/4 turn indicated in the instructions?
- Is there some sort of regulator issue here? More creep than normal?
- Is my Avenger just very unhappy at the lower regulator setting?
For what its worth (not much), all of this was done shooting inside and at 10 yards. No matter what the velocity of the pellet (1040 FPS or in the 600's when at low pressure), there was almost no POI shift (again though, this was only at 10 yards).
Thanks if you got this far, and hopefully someone found this interesting besides me.
TheQuietMan
I'm one of those strange analytical type people, and for me experimenting and fiddling is a huge part of the fun. I'm new to PCP, but not to firearms, and I already had a chronograph so I started immediately. I don't expect much of what I am doing is novel, but since I am doing it and analyzing the results, I figured I would share. I appologize now for my tendency to be longwinded.
While I do have a science background, I am in no way an expert on this, so some of my ideas/conclusions may be way off. They are just how my thoughts are going with what I am seeing. Please chime in if you have a more accurate understanding.
I should also explain that I am frugal by nature. Being frugal, I don't shoot my firearms as much as I would like because of the cost, hence some of my interest in PCP's. Being frugal, I am also interested in what I can do with readily available and cheap 14.3gr Crosman Premier pellets (I like that I can get them at any Walmart). This at least will be my starting point. I may end up trying nicer and heavier pellets or slugs later, but all that I show here is with 14.3gr Crosman Premier (and shot indoor). I will probably also do much of my shooting in my yard, so not much longer than 25 yards typically.
Out of the box, the regulator appears to be set to 2900-3000 (hard to tell exactly). This seemed a bit higher than I expected, but that's where it was. Later checking found the hammer spring to be ~1.75 turns clockwise from the lowest setting. After shooting a few strings, I filled it to ~4200 psi and recorded a string down to ~800 psi. These were done in 10 shot strings and I checked the fill pressure after each.
The pressure estimation is an extrapolation from the reading after each 10 shot string. I found it interesting that it was a very consistent pressure drop per shot (25-30 PSI per). The other ting I found that surprised me was the how consistent the shots were even after the pressure was below the regulator setting. The first 45 or 46 shots should have been on the regulator (~2950 PSI). After the fill pressure dropped below that there were another 30 shots before the FPS started dropping. My assumption from this was that "overgassed" (not sure what the proper term is), by which I mean that a good bit of the air released for each shot is not actually being used to accelerate the pellet (perhaps being expended after the pellet has left the barrel). Assuming that this is true, I am potentially loosing efficiency (and shots). Over that string of 75 shots, I averaged 1004 FPS and 32 FT-LBS, which is more than I think I would want to shoot for. I'm thinking upper 800's and around 25 FT-LBS with 14.3 gr pellets would be a good area to aim for.
Before messing with the regulator, I wanted to see what I could do with the hammer spring adjustment. Maybe it would be possible to get back the inefficiency by dropping the hammer spring tension (and not releasing more air than is used to accelerate the pellet). Checking what it was set to out of the box, it was ~1.75 turns (from all the way counter-clockwise). Here is what I got (10 shot groups at each setting).
It looks like dropping the hammer tension, isn't gaining me back the wasted air pressure (at least not entirely), since we are dropping in FPS with any adjustment down. Adjusting the FPS downward is good, my guess is that even if I went down to 0.5 turns (920 average FPS). I would still find that the shot string may stay level even after the pressure dropped below the regulator setting (wasting air pressure presumably at higher pressures). Next step - adjusting the regulator!
I figured I would start out with AEAC's "eco tune" (1400 PSI, 1.5 turns on the hammer spring). AEAC's video is awesome by the way. This is where things started to be a little strange.
I followed the instructions on adjusting the regulator down (degassed and turned clockwise to the limit and back 1/4 turn. When I pumped up the gun again, this gave me a regulator pressure of ~1900 PSI. Not knowing exactly how the regulator adjustment works, I don't want to try to back up that 1/4 turn more, so I started me experiments with the regulator at 1900. Does anyone know how I would actually go lower?
I decided to try different hammer spring settings at this new regulator pressure, and got the opposite of what I expected (10 shot groups at each HS setting).
This was opposite of what I expected, and I will admit I checked the manual multiple time to make sure I was not getting my hammer adjustment backwards (I wasn't). I stopped for the day and looked at the data a bit. It seems to drift down steadily, with the hammer spring having no effect at all. Here is another view of all the shots.
In this graph, I just show the data from all the shots, instead of binning them by hammer spring setting. It looks to me like the hammer spring setting has absolutely no effect, and the shot string is just decreasing downward at a steady rate. The vertical lines on the graph show where each 10 shot string ended (and the hammer was adjusted). This also showed what assume is the regulator creep. The first shot in every magazine is the highest FPS, sometimes with a very noticeable jump. I assume that this is a creep up in pressure in the time I take to save my chronograph data, reload magazines, check pressures, etc. Is this worse creep that people normally see? I noticed that when the out-of-the-box regulator setting was used (~2950), I could check the gun after it sat overnight and the regulator pressure could be as high as 3200 (but drop back to the ~2950) after dry-fire).
To make sure this was not all some sort of mistake, repeated the experiment the next day, but used 5 shot groups and changed the hammer spring between 1 and 5 turns. (the last two shot strings were 10 shots at 0 and 1 turn on the hammer spring).
Effectively the same result. Hammer spring adjustment seems to have no effect, I see as steady decrease in FPS, with an even more notable spike in the first shot of a string (after pause in shooting).
So, what are peoples thoughts?
- How would I get a regulator pressure below what I got (~1900) since I only turned out the adjustment the 1/4 turn indicated in the instructions?
- Is there some sort of regulator issue here? More creep than normal?
- Is my Avenger just very unhappy at the lower regulator setting?
For what its worth (not much), all of this was done shooting inside and at 10 yards. No matter what the velocity of the pellet (1040 FPS or in the 600's when at low pressure), there was almost no POI shift (again though, this was only at 10 yards).
Thanks if you got this far, and hopefully someone found this interesting besides me.
TheQuietMan
