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[Aggy]

Hi guys I have just rebuilt a Mk1 kevs internals polished and cleaned everything, started with a cut down spring at 54 mm thi spring will run sub 12 but I still tight on the new spring guide , so trimmed the spring supplied by Kev , perfect fit on the guide trimmed down to what I believe it should be at 65 mm polished inside and out 956 fps with 8.44 pellets obviously took it back out again only thing I can think of is the port has been opened ,filled to 200 bar btw .
What should a sub 12 .177 be , I do have my fac but don't want this gun on ticket quite happy at 11.4 .
It does do that with the short spring but sounds slightly off ,a blap valve noice rather than a
Clean blip noise .
I hope this make sense
The gun isn't regged and it seems to be creeping up .I know it will do that but even at the same charge point it has more power than it did .

[Squinty]

55mm is about right.
Old springs tend to be a bit softer too.
Open up the tight spring with a bit of wet and dry on a dowel.. Black n decker job?

Could be hammer bounce making it sound lazy.. does it have a sub-12 pip?

Possible 200 bar is too high and  its still creeping up to the sweet spot.
Start tuning at 150 and increase to find the power curve instead of working down?

177 needs a little extra fast-flow and block porting but if it still has the 2ba location grub it won't be massively over sized.

[Daztilley]

Squinty has pretty much covered it

My mk1 .177 setup uses a kevg sub 12 mk1 .177 ported valve and I have the Theoben mk1 gauge setup Fitted. The type of bottle adaptor used on the mk1 .177 is free flowing to give you better flow in the mk1 block.

The pic below shows the bottle adaptor porting required for .177 sub 12

[Daztilley]

Here's 2 pics of a mk1 bottle adaptor for .177

You can see it has 2 holes next to the push pin and 2 holes in the waist of the threads

Other mk1 adaptors are a choked design to keep the power/flow lower on larger sub 12 calibres

[KevG]

12 ftlbs port should be 4mm stepped down to 3mm were it nears the bore.normaly 60mm spring length on mk1,but each gun can be slightly different
KevG

[Aggy]

Thanks Kev / Daz
The original and when I say original I mean when I got the gun was 54 but the wire gauge was thicker to the point where it didn't really fit the spring guide ,It had been loped off and not refinished , I have now trimmed the spring you sent me Kev to 54.2 refinished it polished inside and out and it's no way bob on its running 11.4  with a very occasional 11.7 maybe an undersized pellet , I have just put three mags through a hole that is just very slightly larger than a .22 pellet . It sounds right too .
The port isn't stepped not sure on size and because it's now ny on perfect I'm leaving as it is .

[Daztilley]

Sounds like it's running nice 👍
I think the .177 mk1 is the most difficult to set up right as its a balance between the hammer spring / valve spring and having the correct porting in the valve and barrel.

I fill mine to 180 bar and run it down to 100 bar - I find that to be the best for power curve and shot count - I do always set the power at the apex of the power curve 150 to 140 bar 👍

[KevG]

if port is fac size be sure to check power curve.normaly you will get more curve with a large port at sub 12ftlbs. to correct this you would just need to fill to a slightly lower pressure
KevG

[Aggy]

This is the point my will power starts to be tested,I really want to keep the gun standard but do see the benefits of quick fill and gauge