Help with "S400 MPR precision" power loss

[TenMetrePeter]

Just re-reading an earlier post on removing the power adjuster anti-tamper as I am about to do the same to my 10m S400 MPR.
Unfortunately it is one of those old posts that will not take any more replies!

So to recap - its drill 2mm hole and tap in a 2mm hex key? Lefty loosey.
The allen key for the m3 grub is 1.5 mm?

I was thinking the bang from the barrel extension was getting quiet - or I was getting more cloth-eared.
Nope, not my ears. Power down from factory 5 ft lbs to 2.5 ft lbs (520 fps down to 370 fps)
Still accurate at 10 m but the long time in the barrel is not going to help my scores.

If its not fixed with the adjuster (or I cant get the a/t screw out) I'll be back.

However this is a shout-out for anyone who has taken apart the firing valve body bearing in mind this is a different design from the standard "fixed" cylinder S400.
Guessing it has loctite.
I am thinking that as I have a 32mm wood drill bit from making the bed for my alloy stock I could make wooden cylinder clamp blocks the same way.

[Blackbaronfish]

You may find its just gunk on the hammer rail.

BBF

[TenMetrePeter]

You may find its just gunk on the hammer rail.

BBF

Yes thanks that's my next step. This model seems to have just one a/t screw cover underneath but I was hoping to keep her a virgin as long as possible.
If I take the trigger plate off and peek up there the rail looks OK so I may try some DriSlide before I do anything. It has been nowhere more challenging than an indoor range in its 2 year life.
It used to go "phtang". Now it goes "phut-tang" if you know what I mean.

[TenMetrePeter]

You may find its just gunk on the hammer rail.

BBF

Spot on Ray. Thanks. The drislide put the fps up to 470 which is near enough for the moment.
I think it followed my trying to bed in the new stock. The timing is right. I rubbed candlewax over the action to stop it sticking to the bedding compound (which I didnt use in the end). I reckon a sliver of wax fell onto the rail.

[Blackbaronfish]

Brilliant. Glad your sorted

BBF

[TenMetrePeter]

So to recap - its drill 2mm hole and tap in a 2mm hex key? Lefty loosey.

OK successfully removed my first A/T power screw plug.
I wasn't expecting sodding stainless steel!
Tentatively used my one remaining cobalt 2mm drill creaking and crunching, and took quite a few minutes to drill a 2mm deep hole!
Anyway it worked. Thanks
https://youtu.be/3Cc_2iq7ueA
By the way the adjuster is there (1.5mm key) as with full power versions and had a fairly light friction setting but I will see if it needs a locking grub screw when I adjust it to the full 6 ft lbs!

[TenMetrePeter]

Follow up.
The velocity settled to 410 fps which is around 3 ft lbs. I wanted nearer 5 ft lb.
So I turned the adjuster out one quarter turn.
Velocity went up to 530! That's a more sensitive adjuster than I expected and no wonder they can go out of setting.
I tried a m3x3 grub screw to lock the adjuster but I could feel it turning under the grub.
Velocity went down to 480 as a result. Need to consider purple loctite if it moves in future.
So I reset the adjuster. Got the following fps strings on my Combro.
135 bar
533
534
532
534
532
533
Then refill to 180 bar
562
560
564
562
560
558
Quite a difference but at 10m with my aim probably not a huge effect. There is no reg fitted to these as AA claims "self regulating"
I normally refill at 150 anyway.