Converting Walther LG300 and LG200 airrifles from 7,5 to 16 Joule(originally posted on the Shooting-the-Breeze forum: http://www.shooting-the-breeze.com/forums/showthread.php?t=19010 )
I have converted two Walther LG300’s and a LG200 from 7,5 Joule/5,5 footpound to 16 Joule/12 fpe field target rifles. All these 3 air rifles already had the new MK2 type regulator (with the ring grooves on the outside).
This new type 7,5 Joule regulator can be set from the original 70 bar setting to a 92-95 bar output pressure. This will allow you to get to 16 Joule / 12 fpe without any other conversion to the rifle. You only need to increase the preload on the hammerspring while shooting it over a chronograph.
The Walther LG300 Dominator is a dedicated field target rifle has a MK2 regulator that is longer than the 7,5J MK2 regulator. The rear part, the secondary/low pressure chamber, is 10mm longer for the 16 Joule/12fpe regs compared to the 7,5J regulator. The number of grooves on the outside is the same however. The 10mm more length means more air to move the pellet. (picture by RobF from Shooting-the-Breeze.com)
But this does NOT mean that you need to buy a 16 Joule regulator to convert a LG300 from 7,5 to a 16 Joule field target rifle. When you set the MK2 short ringed type 7,5J regulator to 92-95 bar you will easily get 12 fpe from an LG300 or LG300 XT. I have done 2 recently with good result.
I even found an advantage in using the short 7,5J MK2 regs: The rifles are less noisy compared to a long 16 joule reg set at 80 bar. I think the long 16 joule regs are using to much air for a shot. The excess air leaving the muzzle and causing the extra blast noise.
The older MK1 type 10 meter 5,5fpe regs have no grooves, are shorter and cannot be used for a field target conversion to get 16J from the LG 300. They need to be changed to the new MK2 type. An 165 euro part which is set to 80 bar for the 16 Joule Walther Dominator field target rifles. This 80 bar reg setting is not high enough to get 12 fpe with the standard hammer and 42 centimeter / 16,5 inch barrel. With the original 80 bar output pressure I got the LG300 up to 220 m/s (722fps) with the JSB Exact 8.3 grainers. Original 16J/12fpe Walther Dominators have a longer barrel (49 cm / 19,3 inch) and a heavier hammer/valve striker. But when the reg is adjusted to 92 bar the LG300 rifle will get to 16J/12 fpe easily.
I made a regulator tester and a special tool to open the reg to adjust the regulator output pressure. But I found that all these 3 regs needed the same three/eights of a clockwise turn on the set screw to get to 92-95 bar. So it can be done without a reg tester.
Opening the reg is not easy. It is screwed together very tight. I clamp the cilinder side of the reg in a big bench vise with aluminum V-grooved jaws and thick leather around the reg to protect it. Then use a special made tool which has bolt holes at 10 degrees angle and use high strenght M5 bolts using the full threaded length in the reg to unscrew the two parts of the regulator.
To get a good working 16J rifle you also need to change the valve seat from the original blue or green type to the harder white PTFE type. This is a 5 euro part. The Walther part number is 2732505.
The only problem that is left by then is the cocking lever. This will interfere with the scope mounts or turret on a field target rifle when cocking the hammer. I shortened the original cocking lever, put in a M4 threaded hole and added a pin so it looked like an original Dominator cocking lever.
The position to which it can be shortened is determined by the pin in the breech block that is the stop of the lever in its down position. It still needs to rest on this pin after shortening it.
The cocking lever is made from hardened steel. To be able saw, drill and thread it I heated the part that needed to come off while keeping the other side in the bench vise to protect it from the heat of the blowtorch so that part would stay hardened.
You can also choose to order an offset cocking lever (Walther part no. 2688638) for about 70 euro. But then you most probably need to adjust the barrel position back and forth in the breech so the tapered loading bolt with o-ring closes nicely in the taper of the breech of the barrel .
This is not difficult (3 screws on top of the breech block) but sometimes the barrel is out of adjustment range because of the new cocking lever. Meaning the transfer port in the barrel does not line up nicely with the transfer port in the breechblock. In that case you need to order a different size loading bolt lever. There are three sizes of this part: 0, 1 and 2. They are called “Spannstuck” in german. Position 8 in the exploded view drawings. The walther parts are 2605864 Spannstück 1, 2605856 Spannstück 2, 2607701 Spannstück 0. The number is stamped on them. I have seen them here: http://www.schiesssport-billharz.de for about 14 euro each.
My own converted LG300 and LG200 field target rifles both shoot very well. I found an nice batch of JSB Exact with die number 80 that shoots 15mm/0,6inch 5-shot groups at 50meters/55 yards from the sitting field target position regularly with the LG300. Just a bit better grouping than I was able to do with my Steyr and EV2.
So in short: A field target conversion of the Walther LG300 and LG200 can be done with good result, but it takes some tools and mechanical handiness.
New Reg Tester made
I made a new regulator tester, (reg tester / reg checker) for Trevor. I used an LG400 valve in the reg tester to simulate the shot and cycle the regulator.