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Brutuz · Senior Member

Well I've allready sold the .177 QB78Deluxe I tuned last month.

I was able to buy a standard .22 SMK XS78 (Copy of the Crosman 160)

You can't keep them all... My favourite cal is .22

Switched the Deluxe triggergroup and Deluxe stock before I sold the .177.

I buy a lot of custom parts @ http://www.gmaccustomparts.com

Gmac has got his RFD recently, I was the first in the Netherlands he shipped an airgun to.

Also ordered a sighted silencer adaptor and a shiny brass bolt handle. Silencers are legal overhere.

Cleaned, tuned and resealed it.

Bought a Weihrauch silencer in the Netherlands because I expected the .22 to be loud.

Take I http://www.youtube.com/watch?v=WJsjj9OXsnc

Shotstring out of the box and after the first part of the tune using 1 powerlet and one dummy

Next using 2 powerlets and lighter pellets

After that loaded 2 new powerlets and tried several pellets. It seems to dislike Gamo's and likes JSB's most.

After that slightly tapered the valve head and matched the piercingpin disc dia.

Next I did 2 10 shot 10 meter groups using a 4x Hawke scope.

Take II http://www.youtube.com/watch?v=Vu10RFopMoM

After that another Chrony string

Take III http://www.youtube.com/watch?v=YWEIqbvhdrs

To do:

some more polishing
re-seal the probe (forgotten)
brass blacken the silencer adaptor
fit a few more brass parts I've ordered (barrelband, end caps)
shorten the silencer base to match the adaptor dia

Nono:

I won't angle the valve port exit hole

Usefull links:

The Charlie da Tuna tune

http://www.charliedatuna.com/CO2TuneByCharlie.htm

The Charlie da Tuna sealkit

http://www.charliedatuna.com/CO2%20Info.htm

Sealkit from Engeland

http://woodfield-gcp.webs.com

UK board dedicated to Chinese airguns

http://ukchineseairgunforum.myfreeforum.org They have got a -12fpe tuning guide available

And this board :-)

packrat · Senior Member

I am truly in awe of your tuning abilities !!!!!!! JUST LAST NIGHT, I sat thinking how neat it would be if the average guy (like me)could find complete instructions with pictures for doing mods to airguns ( specifically the AR 2078A) which is a really cool looking rifle and has the exact same action as the QB78. I sit here this morning, drinking coffee and run across your post and am ELATED..since I was thinking about this just last night, as I said earlier....So I sit here reading slowly and carefully, referring to pix and trying to grasp it all. So I've finished reading and looking at your post, and two things become very apparent to me..ONE-you are at a level of airgun smithing that I can appreciate for the talent that it is, and TWO--as much as I would like to, I know that I would never be able to accomplish the sort of task you've displayed here. I'll gladly pay someone, hopefully as talented as you seem to be, to do any sort of work of this nature on my airguns. MY hat goes off to you sir! To say I'm impressed would be the understatement of the year..AWESOME WORK !!
Thank you for taking the time to post all that..I know that that was a task in itself !!! THIS PLACE ROCKS !!!

Brutuz · Senior Member

Thanks for the kind words, please bear in mind that tweaking like I did just needs a basic technical skil and the basic tools. For polishing and de-burring a Dremel is very handy. Read the tuning guide a couple of times.

I took it apart again today...

Polished the inside of the hollow probe, the inside of the hammer unit, took off the washers and used a piece of Crosman hammerspring to preload the hammerspring, resealed the probe, cleaned and lubed all parts and was amazed by the improved performance...

As before these mods, the fps drops below 490'ish around shot 37.

But the power went up.... Amazing!

Got quite exited so I didn't wait one minute between shots.

Used H&N Hollowpoint 12,65 grain = 12.8 fpe @ 68 Fahrenheit.

First 4 shots

668
675
675
673
then I got a few errors, upto shot 16 all above 650 fps

Switched to 14.35 grain M.S pellets and shot 16 was 634 fps / 12.81 fpe and after that shot the fps gradually dropped, shot 34 was 556 fps.

packrat · Senior Member

From reading your posts and watching your videos, it's plain that you are no novice when it comes to modifying/building airguns. So what to you seems just old run-of-the-mill mods, is to me, a major undertaking! I admire your work very much and I'm sure others here do as well. AT least I got my wish....instructions and pictures for modifying the AR2078A rifle. Very Happy

Alstone · Moderator & Site Supporter

Hey Brutuz what do you think of the SMK compared with the Deluxe 78, also how good do you find the Weihrauch silencer? Question

Anyway the SMK sure looks nice and the sighted silencer mount is new to me, nice job! Thumb Up!

Al

Brutuz · Senior Member

Brutuz · Senior Member

Matched the barrel porthole to the breech porthole and could not resist: angled the valve's exit hole very carefully.

Afterwards wanted to see if I did it wright and check if it still worked. After trying several home made valve-to-breech seals I ended up refurbishing a poly seal which I streched a bit to wide.

Allthough it's leaking a bit at the side of the breech the Chrony reading was 695 fps using the Hollowpionts Mr. Green

Also tried a few H&N Baracuda heavies and was amazed by the penetration Twisted Evil

Hope the new seals will arrive tomorrow.

These QB78's / XS78'es / Techforce 78's / Archer Airgun 78's, basicly all the same and a lot of fun to work on and to shoot Cool

Brutuz · Senior Member

Still waiting for the new seals. Mail between the UK and the Netherlands can drive one crazy.

The barrel seals look poor but can't notice it leaking there. Tried a range of home made seals, they all failed untill I made one that seems to do the job but I'm concerned it's inner dia and shape isn't as desired.

Did record a high of 705 fps using the .22 12.65 H&N Hollowpoints Twisted Evil

Brutuz · Senior Member

It's ready, 709 fps today using 12.65 grain pellets.

http://www.youtube.com/watch?v=q9eCdxIJmp8

A few bling parts from the UK are on their way Cool

Brutuz · Senior Member

Received the brass parts from Gmac today.

What do you think?

brass stock bolt

brass tube and breech end cap

brass barrel band

brass bolthandle

brass sighted silencer adapter with end cap

broommaster2000 · Moderator

I can only express this in dutch, buddy:

Het is een Puik buksjen!

Brutuz · Senior Member

Tnx Broom.

Made a final vid this afternoon:

http://www.youtube.com/watch?v=A_4pmh3duys

Alstone · Moderator & Site Supporter

Very smart and shiny Brutuz I like the brass, a man after my own heart. Mr. Green

Al

broommaster2000 · Moderator

Well, to be honest, IT NEEDS MORE BRASS! Mr. Green

Brutuz · Senior Member

I'd have to send it to All I guess Mr. Green