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Here is the closeup of the 1/16th Allen Wrench Grub Screw Adjustment access shown - End photo by LAMAR shows ERB/TDR mod.

We have Surpassed 750 Pomona Power Mod installations for Air Arms 400/410/TDR Series!!!

Power Mods can be added to .177 or .22 calibers and they do increase the number of shots per charge.

(Note: This modification does not void the warranty!!)

Locate the Power Mod Adjusting screw from left and center photo
Use a 1/16" Allen wrench to adjust the power as shown in right photo
Gently turn the Allen Wrench clockwise until it stops. DO NOT USE FORCE ONCE THE SCREW STOPS. That is your closed position and the rifle will shoot its minimum velocity on this setting. Use this as your zero reference. Measure the muzzle velocity at each setting using a chronograph and record your average velocity of 5-10 shots.
Use the zero reference to measure the number of turns open (counter clockwise) based on the position the allen wrench is pointing. Record the average velocity at intervals of 1/2 or 1 turns depending on the resolution you desire. 3 1/2 - 4 turns open (counter clockwise) is usually full power. This will give you a reference to quickly adjust the power in the field and know where your gun will be shooting. You should do this for each different pellet style/brand/weight that you use. Each gun will be individual but these velocity settings are quite repeatable and stable. This mod is very popular on S400 models for FT shooters allowing them to power down and fine tune their guns to meet ft.lb. limitations on the FT classes and ranges. Many hunters like to maximize their shots by turning down to shoot Crosman Premier Lights or JSB Exacts to 850-900 fps and get ~ 60 shots in .177 or 45 in .22.
EXAMPLE of recorded pellet/adjustment setting and velocity: (Note: Muzzle Velocities given below will vary from gun to gun)

Pellet	Closed	1 Turn (360)	2 Turns	3 Turns	4 Turns
.22 Premier	700	800	900	950	975
.22 JSB EXACTS	650	700	800	850	900

TDR Power Mod Testamonials

"Man, I am so pleased with the way Steve over at Pomona Air tweaked the power mod on my Air Arms TDR. I mentioned before how I was getting 20 shots at 20fpe with JSB exacts. So I thought I post a shot string so you guys could see the numbers. I'm filling to 200bar and I have the power adjustment screw open 3 turns."
So here is the string:
1) 750   11) 752
2) 752   12) 752
3) 755   13) 755
4) 756   14) 753
5) 748   15) 746
6) 754   16) 742
7) 756   17) 749
8) 757   18) 731
9) 764   19) 740
10) 756   20) 723

Standard deviation = 9.5 fps
Extreme Spread = 41 fps

I shot another group to confirm this one and actually got better numbers. For the second group I had an SD of 8.64 and ES of 33.

So according to ChairGun with a 35yrd zero I'll be just over 2 inches low at 50 yards and my JSB Exact will still have 13.5fpe when it hits the target. Pretty, Pretty good!

LAMAR