Air Gun Home :: View topic

Alstone · Moderator & Site Supporter

Got my silencer finished today (Sunday ) took it out to give it a good trial after quite a few changes.

1. New valve and seal.

2. Trigger mod.

3. Polished bolt and longer handle plus larger ball.

4. New Hawke 4-12x40 Scope.

5. New Silencer.

The Scope took a while to get sorted out and works very well. The max fps has now gone up to 698fps with a stable fps of around 675fps. the groupings are not very good 25mm at 20m I will have to get this sorted out, but I'm not sure what the cause is
The silencer works very well at the max fps the only sound you can hear at 10m is the click of the hammer and maybe the faint hiss of gas leaving the silencer.

For our European members who may want to quieten there QB here is the design, the overall length of the gun is only increased by 80mm, as most of the silencer is over the barrel of the gun.

To down load the full AutoCAD file use this URL.
http://www.mydatabus.com/public/alstone/QBSilencer.dwg

Al

StevieLaner7777 · Moderator

That looks ace Al

You really are busy! Sounds like you've got it to be pretty quiet now Al if it's only a click of the hammer that can be heard at 10M.

Is the tube made of Alu?

How tight is the fit between the barrel and the rear cone part of the Silencer?

BTW, Quiet as in not quite silent is spelt 'Quiet', not "Quite", I'm no English teacher (Thank God!), Just thought you ought to remember!

Stevie Thumb Up!

AirGunEric · Site Admin

Wow- that's alot of silencer over alot of barrel! Did you put holes in the barrel to allow it to vent into the silencer a bit sooner than it would just from the crown as well?

Also- is there a grub screw or what is holding the silencer to the barrel?

Nice work in any event, it certainly does make for an interesting QB. Very Happy

Alstone · Moderator & Site Supporter

Hi all
The Tube is 25mm x 1mm Aluminium tube.
The fit between the rear cone and the barrel is a sliding fit, one thing I should have shown is a O ring in the cone, also the cone as a grubscrew holding it on to the barrel and there is also an O ring between the cone and the barrel, a single screw is used to hold the tube to the cone.

The front exit section is also fitted with an O ring between the tube and where it joins the front section. I'll redo the drawing to show these extra bits.

There are no holes in the barrel, 80mm of space in front of the muzzel and a tube dia of 25mm or more, is ample volume to quieten a Co2 rifle at less than 700 fps, the extra tube behind the muzzel also helps, the nylon support ring which is 40mm behind the muzzel also makes a diffrence depending how far down the barrel you put it.

If the output of the rifle is more than 700 fps you only need to move the end of the silencer further away from the muzzel, in actual fact this silencer is tuneable.

Cheers with the spelling Stevie, it's the Dyslexia creeping in.

Al

StevieLaner7777 · Moderator

Hi Al

Ah yes! I thought it might have had some O rings within the construction but wasn't too sure as they didn't feature in your schematics.

Yeah I noticed your spelling of that particular word before in a previous post, then again in another, then just now, I just though it was something to do with regional spelling differences, For example 'Mom' as in 'Mother' is spelt 'Mum' as apposed to 'Mom' here in Hereford and probably other places too, I'm not sure how many regions use this spelling of this word.

Anyways! I think I'm drifting off subject again LOL! I'm getting too good at this - Sorry!

Stevie Thumb Up!

broommaster2000 · Moderator

Looks nice. I'll ask a friend to check it out. Maybe he can get it made.

Alstone · Moderator & Site Supporter

The shiny silencer on the QB was a bit to much and needed toning down a bit, so I tried out a method I use for painting live steam models.

I clean the silencer with alcohol warm up a tin of Auto spray primer under a hot tap, so that you can still hold it comfortably and spray silencer, allow to dry then do the same with matt black Auto spray, when dry you should have a fairly durable finish, you can apply oil to the surface the same as you do to the rest of the gun.

Stevie I polished the stock like you recomended and put a piece of "Bling" on the butt. Laughing

Al

AirGunEric · Site Admin

I think your paintjob improved things- after you mentioned it and I looked at the original unpainted silencer- it did look alot like a handle instead of a silencer! Good thinking. You can also definitely see the shine on that stock now.

broommaster2000 · Moderator

It looks very nice. Proficiat! What's next? Mr. Green

StevieLaner7777 · Moderator

Looks Binging Al lol!!

Yeah the silencer looks much better now!
Did you layer a plate of metal between the Butt and the Butt stock to make that effect?

The polish job looks excellent! all you have to do now it just give it a wipe over now and then to keep the maulers off it! lol.

Good job!

Stevie Thumb Up!

Alstone · Moderator & Site Supporter

Hi Broom
I don't know whats next, but I bought some aluminium tube last weekend to make a bipod for it ( I'm a tight git, I don't buy anything if I can make it ), but now I'm not sure I want one.

Stevie
The butt plate is aluminium, the plastic butt came loose and one of the screws fell out, when I took it off I found that someone had put a hole in the wrong place and tried to re-drill it half a hole away, so I screwed an aluminium plate on to the stock and put the plastic butt ontop, I think it looks better anyway.

My grouping is still not right and I am wondering if the barrel band is causing it, it is tight on both the gas tube and the barrel, so I am going to alter it so that the barrel can slide in it, I think the expansion and contraction of the gas tube is flexing the barrel as the shots go of target for a few shots then come back again. any Idea's ?.

BTW how many shots do you get from a full load of gas, I get about 65, with yours being .22 do you get less.

Al

StevieLaner7777 · Moderator

Hi Al!

If you do make a Bi-pod how are you planning to attach it to the QB78?

If the POI is occasional changing It may not be the Rifle but the Scope, If the scope is getting a parallax error, make sure you are looking dead center through the scope before you shoot each shot to minimise it, If that doesn't work it may be to do with the Rifle or even the pellets, I hear that the some QB7x Rifles can be pellet sensitive, Try experimenting with different sights and pellets to see if any affect it more, and then try and see if you can improve it.
Mine doesn't like Bisley Magnums for example.

Also My QB78 .22 will get about 60 full power shots average on a warm day, Though I have been able to get 70 full power shots with it before (last Saturday was very hot), I think when it gets cold it will go down to around 50 full power shots in the winter, probably less.

Stevie Thumb Up!

broommaster2000 · Moderator

Alstone · Moderator & Site Supporter

Sorted out the problem of shots wondering off target, I did the crown when I got the gun by just grinding the orignal crown with a brass round headed screw, coated with grinding paste, it looked allright so I left it at that.

Having a closer look at the crown what with the problems I was having, I noticed some groves in the barrel also the crown was lopsided, so I machined half an inch off the barrel re-crowned it and got rid of most of the groves which seem to have been caused by boreing out the barrel without any lubricant, this was only about half an inch in from the muzzel.

$hit I have just noticed from the photos that there are still some groves in the barrel, I will have to take another half inch off.

BEFORE

AFTER

Al

AirGunEric · Site Admin

What is with Chinese manufacturing machinery these days? Poor tooling quality seems to be a bit too common. I wonder if they just run things until the won't cut anymore, or refuse to stop the line when they run out of something (like lubricants or decent cutting heads, etc)? I've never been able to figure that one out.

Have you shot it yet to see how much of an improvement it's made?