N/A PCP cold weather shooting

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Sleestak

Sleestak

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Aug 11, 2024
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So the weather was relatively pleasant. Bright sunshine, no wind, but it was coldish. Maybe mid 20's F?

Things started out great, but as I was out there longer it seemed like my shots were more erratic, especially the drop. I decided that I had better quit when I started fiddling w the scope more than is healthy... before I just made it worse.

The extremities were getting pretty numb by then anyways, so I retreated to the nearest beer house.

Gonna warm the guns back up to room temp & see how they perform in the basement today

What do you think, does chilling a gun kind of make sense as a cause of all of this inaccuracy? They were working great to begin w..
 
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Sleestak said:
So the weather was relatively pleasant. Bright sunshine, no wind, but it was coldish. Maybe mid 20's F?

Things started out great, but as I was out there longer it seemed like my shots were more erratic, especially the drop. I decided that I had better quit when I started fiddling w the scope more than is healthy... before I just made it worse.

The extremities were getting pretty numb by then anyways, so I retreated to the nearest beer house.

Gonna warm the guns back up to room temp & see how they perform in the basement today

What do you think, does chilling a gun kind of make sense as a cause of all of this inaccuracy? They were working great to begin w..
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Temp absolutely has an effect. Regged or unregged, the "energy" of the particles is directly related to temps. Thermodynamics!!
 
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That’s crazy, I mean I avoid walking the woods in the teens or 20’s but at just over freezing I’ve dispatched many a rodent. I haven’t spent a lot of time in the chrono at those temps, but hadn’t really noticed much of an impact change out to 35yds with a Kral puncher mega .177. I wonder if a .177 is less affected by temp change due to a lower volume of air used and less contact area on pellets.. 🤔
 
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My recent experience was that, when going out into the cold (low 30's F or lower) from room temperature, the plenum pressure went UP while shooting. Apparently, when my AMP regulator gets cold it doesn't shut off the flow of air to the plenum as easily as when it's warm. The increased plenum pressure causes the muzzle velocity to drop.

stovepipe
 
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stovepipe said:
My recent experience was that, when going out into the cold (low 30's F or lower) from room temperature, the plenum pressure went UP while shooting. Apparently, when my AMP regulator gets cold it doesn't shut off the flow of air to the plenum as easily as when it's warm. The increased plenum pressure causes the muzzle velocity to drop.

stovepipe
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That is very interesting! But, I don’t understand why an increase in plenum pressure would cause decrease in projectile speed. Can you explain?
 
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Patrick1 said:
That is very interesting! But, I don’t understand why an increase in plenum pressure would cause decrease in projectile speed. Can you explain?
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Higher plenum pressure will try to keep the valve closed stronger so that hammer might not be strong enough to open it as much as it does with a little lower pressure. Hence, valve doesn’t open as much and closes faster, dropping speed.
 
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I don't shoot in the 20s or even 30s but I do measure lower velocity in the 40s and 50s than I do at 70 degrees or more. I hope to shoot a target later today when it gets into the 50s. I will put the gun on the bench before putting the pellet trap out at 30 yards. I may let it sit outside for 15 minutes or so before shooting. I want the gun temperature to stabilize so the velocity will be more stabile. I still don't shoot as well when it's colder but I think a big part of that is I am not comfortable.
 
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Patrick1 said:
That is very interesting! But, I don’t understand why an increase in plenum pressure would cause decrease in projectile speed. Can you explain?
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Somewhere on this forum there must be a graph of muzzle velocity vs change in hammer spring preload when the plenum pressure stays the same. There should also be corresponding graph showing muzzle velocity vs change in plenum pressure when the hammer spring preload stays the same. There might be youtube videos that show these graphs and explain them. I'm not going to look for this stuff, but every pcp owner needs to understand these simple relationships. Once understood, it forever changes the way a person looks at a pcp rifle.

stovepipe
 
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Patrick1 said:
I’ve been on here….. forever and watched just under 2.5 million YouTube airgun videos, just never thought of this! Thanks for explaining, really!
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No worries. Just in case: your goal is to reach the speed a barrel/ammo combo shoots best with the lowest possible plenum pressure and the least possible hammer. Ideally, your “fully open” valve (meaning more hammer doesn’t increase speed anymore) is at around 103-104% of target speed. Then you dial the hammer back to reach your target speed. Tuning to the knee of the curve discussed above :)
 
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greenbeans said:
No worries. Just in case: your goal is to reach the speed a barrel/ammo combo shoots best with the lowest possible plenum pressure and the least possible hammer. Ideally, your “fully open” valve (meaning more hammer doesn’t increase speed anymore) is at around 103-104% of target speed. Then you dial the hammer back to reach your target speed. Tuning to the knee of the curve discussed above :)
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Thanks, again!! My Maverick compact .22(500mm barrel shooting 16 gr pellets) with the Shooting with Phil micrometer and knob is pretty easy to dial in a speed. For example, Phil has a “guide” that suggests, for my specific barrel and pellet, that a plenum pressure of 80 bar will get to about
880fps, with hammer spring setting of about 9.10mm.Depending on temperature, it gets pretty close. I usually set the first reg at 35 bar(115 bar) above the 2nd reg(80 bar).
 
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Funday Friday:
20250221_135957.jpg
 
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