Tuning Adjusting The Reg Pressure On An HW100?

[MP44]

Can the regulator pressure be turned down while under pressure? The rifle I have is fitted with an aftermarket aluminum tube and doesn't have a check valve so I would have to drain all the air if it is required.



ETA: I want to lower the power to 12-13 fpe



TIA!! 

 

[Poopshoot55]

Yes you would have to drain the air, for the simple reason you have to install a pressure gauge in the bottom of the breech block to tell you what the pressure is. I unscrewed mine because I have the original air tube. There is an English gentleman on YouTube who does a complete reseal and regulator adjustment in a 3 part series, a bit of a slog, but very informative. I believe the 3rd part deals with the regulator adjustment. Rick 

 

[elh0102]

No necessity to install the gauge. Granted, it makes things easier, but if you're tuning to a certain power level, there will be some trial and error anyway to get it right. I wanted my .177 at the 11-12 fpe level, with the HST between 95-97% of max, and I got it balanced there with the second reg adjustment. Mine has the OE cylinder, so I removed it.

 

[KatoKevin454]

are you wanting more or Less power?

you can adjust the regulator without removing the air and not installing a gauge, just back out the adjustment screw, you will have to take the gun apart and separate the block to access the regulator adjuster screw (the big Hex screw), turn counter clock wise to lower pressure and turn clockwise to increase pressure, Dry fire the gun Safely too allow the regulator to reset, it is best to use a Gauge to set the regulator at the pressure you want more accurately, if you use the Gauge you will need to relieve the air pressure from the gun. the Allen Grub screw in the middle of the bottom block is the gauge port, there is a ball bearing and a plastic seal in it, so be careful not to lose them, I like to set mine at 90 bar for about 780fps, 

you can also adjust the Hammer spring for power adjustment without so much disassembly, just remove the stock and back plate

the Hammer spring is located behind the back bolt plate held by 2 small hex screws, remove the back plate, pull the side lever back enough to access the locking Grub screws, not too much or the bolt return spring and its keeper will come out, and it's difficult to put back in....., typically there is one locking grub screw on the side of the Hammer, some times more than one, make sure you check before turning the Hammer spring adjuster in the middle of the Hammer, clockwise is more power, counterclockwise is less power, make small adjustments till you get the power you want, make sure to snug down the locking Grub screws, not to tight, just a good snug, if you can't get to the power level you want, then you can make regulator adjustments. 

 

[inverted]

I also have an aftermarket aluminium tube but I opted to take cylinder ends from the original air tube so there is a check valve, quick fill port and original pressure gauge (Weihrauch uses WIKA gauges on their rifles.

If you still have the original cylinder, maybe you could swap those out and be good in a long run.

I got mine from UK, they ship world wide and sell cylinder end with check valve separately if you need one.

I don't know where did you get your tube from and if it will fit. My tube is a replacement part so size and threads are the same as original

And to your question, as it has been answered already, yes, you can go lower with the reg while pressurized but go slowly and dry fire to reset the reg. 

 

[elh0102]

Just FYI for those making adjustments without a test gauge, this might offer a point of reference. My rifle was shooting the 10.3 at around 890 fps, and it is now shooting at 700 fps. I turned down the reg a half turn, did some testing, then turned it down another quarter turn. I could achieve my power goal at the first reg adjustment, but I wasn't using as much HST as I wanted. I'm no tech, but I understand that a tune using 95-97% of maximum spring tension is usually air efficient, and it has worked well for me. And my shot count is way up, well above the proportional decrease in power. 

 

[MP44]

Thanks again for all the info.

I adjusted the regulator and hammer spring.

The rifle started out at 920fps with a 10.4 gr AA. I turned the reg adjuster screw out a little over a half turn. this put the 8.4gr AA, the weight range I want to use, at 880fps. Turned the screw out just a tad more and I was in the 850s with the 8.4gr. From there I started turning the hammer spring tension screw out about 1/4 turn at a time.

The first 4 adjustments of the tension screw made no difference in velocity but I did notice a slight decrease in noise with each adjustment. When I made it to 1 1/4 turn out the velocity dropped to the 840s and that is where I left it.

I mounted a scope and sighted it in. It stacks the 8.4gr AA. The next day I am off with nice weather, I will start experimenting with other pellets in the 7.9-8.6gr range.

 

[KatoKevin454]