Rohm Twinmaster standard power?

[mrgeoff]

Hi, my Rohm Twinmaster is only running about 2.5ftlbs. It had the assister spring kit, and was still only running a tiny bit over 3, but I took out the assister spring to make the trigger nicer for 10m target shooting.

Is 2.5ftlbs about right as standard?

Also, I have read that adding shims to the regulator will up the power, but it really needs to have the assister spring behind the hammer to work together.
In the same tuning guide, it was saying some minor adjustment can be made by the inner grub srcrew in the regulator, is this worth a play? I had a nose, and the brass cross headed screw in the reg was loose, is it supposed to be locked down against the adjuster grub screw?


Thanks.

[Benelli B76]

mrgeoff, you are quite right about the power output, mine is very underwhelming compared to my other target pistols such as the IZH 46M and FWB 2 which knock out pellets at 450 to 500 fps, and even my old Airmatch 600 beats it. I have decided to have a look and do something about it, so I will let you know what I accomplish.

Baz

[mrgeoff]

Cool, thanks.

I decided to tweek mine a bit, but keep the standard hammer. Wont get to test till Friday though.

[Benelli B76]

Glad you started me off on this, been meaning to do something. The regulator has 8 Belleville washers 12.4mm x 6.2mm x 0.7mm. They are stacked in normal series configuration - ()()()(), you can change the pressure by changing the configuration slightly (see link). Should be easy to get a steady 5ft lb, but be careful not to exceed legal limit. I will pm you more info after I have been to the range to chrono different settings.

Regards, Baz

http://springipedia.com/belleville-washers-stacking.asp

[mrgeoff]

Hi, there is good info from magic9 on changing the regulator pressure, its not on the normal site, but can still be found via google.

Shows the washers, stacked with optional shims. One thing noted, that was if the regulator pressure went up too much, you needed to compensate with a harder hitting hammer, which I am trying to avoid, I'm trying to leave my trigger a bit lighter.


Let me know how it goes


Cheers.

[airgunnut]

the twin master was designed for 10m indoor target shooting, so why do you need 5 foot pounds? 2.5 ft pounds will kill a paper target just as well as 5 ft pounds but with less turbulence behind the pellet, more shots per charge, less noise and possibly better accuracy

[Benelli B76]

airgunnut, with the forum name that you are using, you should know why us boys need to experiment. I never use my air pistols for 10 metre target shooting, after 50 years of shooting (I am 68), I find it boring and not challenging. I used to do long range pistol shooting when I lived overseas (usually up to 200 metres) with calibres from .22 rimfire to .357 Automag (Lee Jurras special), and now I have only air pistols, I like to shoot them at 25 to 50 metres. I like to get the trajectory as flat as possible within legal constraints.(By the way the forum name I use, Benelli B76, is the most accurate 9mm pistol I ever owned for long range pistol in that calibre, Google it.)

Baz

[mrgeoff]

My rohm was running 3ftlbs, and I dropped it. 2.5 seems a bit weak from these pistols, and sounds weak.

Im only after 3 again, but with the soft trigger. Will be happy if I can achieve this.

[Benelli B76]

Two extra Belleville washers in regulator I am getting 4.48 ft lb and not draining cylinder too quickly. Shooting accurately at the 25 metre range this morning, and I am much happier with this pistol now.

Baz

[mrgeoff]

Still no further on with mine, once the regulator gets to a certain pressure, the firing valve needs to be hit harder, otherwise the actual power goes down with more regulator pressure

Seems 440fps is about the max for me on the standard hammer spring. I will stick there as the trigger is more important to me than outright power. Well, it will have to be


Cheers.

[airgunnut]

you should know why us boys need to experiment.

Baz

Years ago as a machincal enginering apprentice it drilled in to us not to mess around with compressed air, (this was only 10bar) the twinmaster has 200 bar in the air cylinder (and the reg) if the safety features in the cylinder don't do there job you effectively have a hand granade! If you want to experiment with the reg then make sure no one is around when you pressurise the thing (my lp300 has a leak in the wall of the cylinder and its funny that no engineer wants to "experiment" with methods to fix it!) if you want a pistol that's aproching 6 foot pounds then buy a pistol thats designed to run at 6 foot pounds, I have seen the aftermath of air guns that have been experimented with, not prity, the man in question was questioned by the police while he was still in hospital!





Rant over

[paul4be]

I used one of magicniner's tuning kits to run my Rohm at around 5.2fpe. The kit used an additional hammer spring to up hammer weight without adding too much more to the preload. The reg also required reshimming, I can't remember now quite what configuration of shims I used, but it was nowhere near the equivalent of another belville washer in the reg. Reshimming the reg needs to be done carefully and in small steps to see what is going on in terms of power.

[airgunnut]

I used one of magicniner's tuning kits to run my Rohm at around 5.2fpe. The kit used an additional hammer spring to up hammer weight without adding too much more to the preload. The reg also required reshimming, I can't remember now quite what configuration of shims I used, but it was nowhere near the equivalent of another belville washer in the reg. Reshimming the reg needs to be done carefully and in small steps to see what is going on in terms of power.

The diffrence is magicniner is a airgunsmith, it's his job, he uses his extensive airgun experiance, established enginering techniques and verious formulas to determin how much a gun can be tweaked

[Benelli B76]

Still no further on with mine, once the regulator gets to a certain pressure, the firing valve needs to be hit harder, otherwise the actual power goes down with more regulator pressure

Seems 440fps is about the max for me on the standard hammer spring. I will stick there as the trigger is more important to me than outright power. Well, it will have to be


Cheers.

Geoff, mine is performing really well now, up in performance with my Feinwerkbau Model 2 and surpassing my Baikal IZH-46M in power (though not in accuracy). Very happy with it now, was on the point of selling it.

Baz

[wwwdot]

As I've just acquired a twinmaster top I read this thread with interest. I have seen the magicnine assister kits online and wondered if they were worth fitting. The other thought I had is why not just fit a stiffer spring, why bother with the assister spring ?. fitted in addition to a spacer or two to increase reg pressure.

Oh and by the way I'm looking for a scope rail to fit a red dot sight .Does anyone know where I might get one ?

tia

wwwdot