Velocity Issues in Cold Weather?

[debruynda]

So I played this past weekend in 40 degree weather and was having velocity issues.

I had to crank the adjuster in so far that it was venting out the back (small leak) to get my velocity up to 265.

I didn't have the time to tech it to see what else could be causing the issue, but was wondering, and this will display my lack of knowledge on the issue, but even with compressed air, in cold weather could the weather be the cause or should I be concerned about the way my valve is set up? It's an RT pro valve (first generation Retro) with level ten, stock spring, no shims, not sure what size carrier. It shot fine with consistent velocity after turning it up, but my sense is I should not have to turn it in that far just to get 260-270. Oh yeah, running 1100 from a ninja HPA reg.

Appreciate any suggestions.

[Cyco-Dude]

i would look at your paint and barrel. cold will shrink your paint, and if you're already overbored it could easily cause your velocity to drop compared to warmer weather. what size is your barrel bore, and what size was your paint in 40 degrees?

[athomas]

The orings will get stiffer in the cold and the ball to barrel match will change in the cold.

[debruynda]

i would look at your paint and barrel. cold will shrink your paint, and if you're already overbored it could easily cause your velocity to drop compared to warmer weather. what size is your barrel bore, and what size was your paint in 40 degrees?

I didn't have a paint sizer, but I started with a .684 freak back and went down to a .682. It was shooting at 170 with the .682 before I cranked up the velocity. I didn't have anything smaller than the .682. It's supposed to be twenty degrees warmer this weekend so hopefully I don't run into the same issue.

[athomas]

You don't need a paint sizer. Drop a ball into the back of the barrel and look at a bright light through the back of the barrel with the ball in place. You will be able to see how well it fits. It should barely touch on just two tiny points on opposite sides of the ball. If it sits against just the bottom side and has a large gap on the top side, then the barrel is too big for the paint. If the ball hits more than two spots or is tight all the way around, then the barrel is too small for the paint.

[Cyco-Dude]

hmm...man, i dunno. that seems awfully low, even if it was overbored and cold out? i wonder what it was shooting at in warmer weather prior to you using it in the cold weather? you weren't short-stroking the trigger were you? i wonder if your sear rod is not adjusted correctly, or if your on/off pin is not an optimal length? or maybe the chrono was low or power and giving false readings? did it look like it was shooting that slow? what valve are you using? what on/off do you have? double-check that your sear trigger rod is the correct length.

[athomas]

Has the valve had the regulator piston assembly changed to the higher pressure level 10 version, or is it still using the original one?

[Cyco-Dude]

Has the valve had the regulator piston assembly changed to the higher pressure level 10 version, or is it still using the original one?

oh, he said it's a retro valve. was that an issue for them?

[blackdeath1k]

oh, he said it's a retro valve. was that an issue for them?

All a retro valve is is an RTPro valve with a different t badge. But yes. Pretty much any valve that was around pre level 10.

[Cyco-Dude]

All a retro valve is is an RTPro valve with a different t badge. But yes. Pretty much any valve that was around pre level 10.
well that could be it then, may just need a new piston.

[Syko89]

Did you try a smaller lvl 10 spring

[debruynda]

Has the valve had the regulator piston assembly changed to the higher pressure level 10 version, or is it still using the original one?

No, same regulator piston. Where can I get an updated one?

The pin length is the stock RT length, I checked it with Calipers.

It shot great the day I played in warm weather.

However, I noticed also that the orings on my fittings (ccm) would leak a little too so my sense is that the cold weather shrank the orings.

[debruynda]

Did you try a smaller lvl 10 spring

Had the stock level ten spring in, I have the other springs but have been using the stock one.

[debruynda]

hmm...man, i dunno. that seems awfully low, even if it was overbored and cold out? i wonder what it was shooting at in warmer weather prior to you using it in the cold weather? you weren't short-stroking the trigger were you? i wonder if your sear rod is not adjusted correctly, or if your on/off pin is not an optimal length? or maybe the chrono was low or power and giving false readings? did it look like it was shooting that slow? what valve are you using? what on/off do you have? double-check that your sear trigger rod is the correct length.

I did notice it would short stroke but I thought that was largely due to the low pressure and once I turned it up it stopped short stroking altogether.

[debruynda]

You don't need a paint sizer. Drop a ball into the back of the barrel and look at a bright light through the back of the barrel with the ball in place. You will be able to see how well it fits. It should barely touch on just two tiny points on opposite sides of the ball. If it sits against just the bottom side and has a large gap on the top side, then the barrel is too big for the paint. If the ball hits more than two spots or is tight all the way around, then the barrel is too small for the paint.

That's what I did, along with the "old blowgun" test:) I just brought up the paint sizer issue because I use it sometimes when someone has one, just did not have access to one the day in question so I went with the old school method you describe. But thanks for the knowledge, I was unaware of some of the things you mention to look for. Muchos grassyass.

[athomas]

Large or small bores will affect the velocity a bit, but they don't usually affect it that much. I personnally use a large overbored barrel for everything. That way I don't have to worry about breaking fragile paint as the bolt pushes it into the back of the barrel.

If your regulator piston has never been updated, you should get a new one. AGD or Tunaman can sell you a new one. I think the higher pressure version is now the standard piston assembly in all mags.

[debruynda]

Large or small bores will affect the velocity a bit, but they don't usually affect it that much. I personnally use a large overbored barrel for everything. That way I don't have to worry about breaking fragile paint as the bolt pushes it into the back of the barrel.

If your regulator piston has never been updated, you should get a new one. AGD or Tunaman can sell you a new one. I think the higher pressure version is now the standard piston assembly in all mags.

Found it on the AGD site. Thanks for the advice fellas! Much appreciated.