FX FX Impact M3 vs Temperature Change

[Troy Bakel]

1. Rifles - 30 cal, latest AMP regulators. 177 cal, original AMP regulators. Both rifles are 4 years old.

2. Temperature range 25°F to 65°F

3. Cool down: Rifle placed in case, with bottle pressure ~ 190 bar, stored in unheated barn:
a. Bottle pressure decreases first.
b. 1st stage pressure decreases second.
c. Plenum pressure decreases third.
d. If temperature decrease is great enough to lower the 1st stage and plenum pressures far enough - regulators will try to maintain set pressures.

4 Warmup: Rifle placed on bipod and left to equalize with temperature of the indoor range ~ 65°F.
a. Plenum pressure and 1st stage pressures increase to > set point
b. Bottle pressure filled to 200 bar.
5. First ~3 shots:
a. Adjust (increase) Micro setting to Plenum Pressure DOPE.
b. Monitor plenum pressure after each shot and decrease Micro setting per Plenum Pressure DOPE as required.

NOTE: Outdoors the 30 cal had to warm up from ~38°F to 78°F with the 1st shot plenum pressure 10 bar greater than indoors. Using the maximum Micro setting from indoors, my first shot at 50 yards cut the 13/32" diameter 10 ring of my 2" tip to tip diamond target.

 

[CoyoteGod]

Do you need to do this with you Impacts every time you take in out of your barn to shoot?

I have owned several Impacts and used them in many different environments and elevations and never had to do your DOPE routine. Just recently I hunted in elevation from 3000-8000 feet with temps from 30-85 degrees. Filled bottles in different locations and temps often. Sure bottle settled but not more than 10 bar at most. My regulators and tune were also within acceptable FPS to keep my DOPE for most of my temp/elevation changes. Even when waking early morning with Airgun sitting out in the cold and getting right to hunting for first light Regulators were spot on.

 

[Troy Bakel]

1. Just wanted to see how consistent I could keep the fps of the first shot.
2. I use the DOPE every time now because it took me so long to get good data.
3. The 30 cal is tuned: Air Valve = 3.0, Macro = 16, Micro = 3.5, 1st reg =150 bar, 2nd reg =115 bar. The only time I have to increase the Micro is when temperature drives plenum pressure up 10 bar or greater.
4. The 177 is a stock M3 tuned for < 12 fpe. Air valve =3.0, Macro =1, Micro =2.1, 1st reg = 120 bar, 2nd reg= 70 bar. When I am shooting multiple days in a row I leave the rifle in the van. The hammer strike on this rifle with normal plenum pressure is so lite the wadcutter striking the target at 20 yards indoors is louder than the shot. If plenum pressure increases 10 bar due to increase in temperature the fps drops from 810 to the low 700s. The next issue is the shot/bar on this rifle is very, very high. I have finished two 10 bull cards before the plenum pressure dropped to 70 bar and one more 10 bull card before the 1st reg dropped to 120 bar. In short, if I charge this rifle to 200 bar at 25 to 30 °F and it warms up to the range temp of 65°F I can complete 60 bulls with sighters before bottle pressure drops to 190 bars.