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My QB79 .25

Printed From: Kiwi Airgunners
Category: Technical
Forum Name: Pauly's Technical Area
Forum Description: Technical information, Modifications and DIY projects are all in here
URL: www.kiwiairgunners.co.nz/forum_posts.asp?TID=30
Printed Date: 29 Apr 2024 at 8:03am
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Topic: My QB79 .25

Posted By: Raizer
Subject: My QB79 .25
Date Posted: 13 Apr 2013 at 6:28pm

Cross posting from another forum, but here is my QB79 project

03/04/2013

Raizer:340354 wrote:

I brought a Mike Melick "power tuned" .22 QB79 back in August last year which I was rather excited about at the time lol

Was doing 15+fpe out of the box

Before doing to much shooting I had the barrel threaded and added a Porky style silencer

And when I was really lucky I would get groups like this

But only with JSB pellets

And most of the time they were more like this Unhappy

Also had some 10m groups that were over 12" ctc at 15m with superdomes!

After working my way through multiple possible causes with advice from members of this and other forums I soon found that the stock barrel was bigger than .22 and pellets pretty much weren't engaging the rifling, the only reason I can see that the JSB's were doing ok for the most part is there very soft skirts.

The marking looks a lot deeper in the photos than in person!
Also the probe/bolt seal and transfer port seal were both leaking a bit.

I decided I didn't want to spend $60+ on getting another stock barrel sent to me only to risk getting another dud so after talking to an excellent machinist on other forum we decided .25 was in this guns future!
So I now have a BSA blank winging its way from John knibbs Big smile

While waiting for that to get here I've opened up the "piercing body" of my valve (badly), lined the valves port up with the hole in the tube, found a 5mm id tube to use for the transfer port and replaced much of the stock screws for strength.

Aiming for 40fpe still on co2 at this point, next step will be a 17ci hpa tank shimmed to 1100psi.

04/04/2013

Raizer wrote:

As said, my first attempt at opening out the front of the valve didn't go too well Embarrassed

Jonballs is checking if he has one for me, so hopefully my 2nd attempt will go a lot smoother!

Trying to figure out how to do my transfer port and still have the valve seal to the tube

04/04/2013

Raizer:340538 wrote:

Take 2 should look more like this

The spring is currently still held in with the factory washer, Mike Melick ground it into a triangle when he did the original tune, he also cut a seat for the spring into the valve stem

09/04/2013

Raizer:341873 wrote:

Customs Declaration
1x rubber oring
1x grease
1x steel tube for machining

declared value: £15

;D

So my barrel arrived this arvo, haven't taken it out of the bag yet, but just looking through the plastic the blueing and rifling looks really nice!
Kinda disappointed it doesn't have the BSA logo stamped in it haha

(the "oring" is a new breech seal for my Hatsan)

11/04/2013

Raizer:341873 wrote:

Take 2 went a lot smoother, I had one slip with the grinder but thankfully didn't manage to destroy the piece!

Brought a longer spring for the valve too.

11/04/2013

Raizer:341911 wrote:

I just got an update on the machine work

Here's a quick progress report for ya.. I have turned up a new .25 cal bolt probe and turned the barrels breach down to a very snug polished fit which requires a soft face hammer to send home..

This will be a far better means of attachment than the factory undersized breach floating on those 3 soft O rings and one retaining grub screw allowing it to slop all over the show with the slightest knock. The new fit is so snug that it wont in fact require any O rings to seal it. I will put it in the mill tomorrow and open up the feed tray section of the breach.

I will turn the bolt probe down a bit thinner and shape the tip of the probe to fit the rear end of a JSB King perfectly aiding bore to pellet alignment further.
The Kings are a perfect candidate pellet for this project as they are light, short and tend to out shoot any other pellet in all .25 cal rifles. The challenge you now face is blasting enough CO2/air up its skirt to get them moving..
The bolt will have a tapered touch fit to a shoulder just inside the breach like a Theoben Rapid with an additional breach O ring just behind that.

I gave the bore a good scrub to rid it of the factory crud and have pushed a few pellets through the new 1/4" bore and there is plenty of bite in this bad boy.. the choke is nice and tight and the pellets exit showing good strong rifling grooves in the head and skirt.

12/04/2013

Raizer:342140 wrote:

Latest update Big smile

[color=teal][size=10pt]Well Raizer, Your Qb79 is officially a .25cal! The barrel is fitted and I have cut the sweetest JSB chamber in it sized perfectly for the Kings.
I also shaped the bolt probe tip to suit the internal skirt angle... tomorrow I will machine a groove in the bolt to add a breach O ring and a mod to the transfer port sealing surfaces to fit a decent O ring.

http://s1057.photobucket.com/user/wingman102/media/IMG_3366Small_zps87d63da5.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3370Small_zps349689a4.jpg.html" rel="nofollow">

That will only leave the crown and 1/2x20tpi muzzle thread to complete before hopefully some testing on paper tomorrow..[/color]

http://s1057.photobucket.com/user/wingman102/media/IMG_3373Small_zps44dc0ca5.jpg.html" rel="nofollow">

Replies:

Posted By: nunga
Date Posted: 13 Apr 2013 at 6:58pm

It is coming on nicely :) look forward to your test results!

Posted By: Raizer
Date Posted: 13 Apr 2013 at 9:59pm

I'm really looking forward to them too!!

Posted By: Raizer
Date Posted: 14 Apr 2013 at 9:09pm

[color=teal][size=10pt]Ive cut the breach seal groove and fitted an O ring.. Ive tested it under pressure and it shows no leaks at all..

http://s1057.photobucket.com/user/wingman102/media/IMG_3381Small_zps064ad43f.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3380Small_zpseba3f87c.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3384Small_zps5d22e414.jpg.html" rel="nofollow">

I have reassembled the rifle and put a few shots through it but it got too dark to chrony.. judging by the hole in my fence it will be quite the possum slayer now.. Will do some velocity and group tests tomorrow and get it back to you. Its just screaming out for a Hpa conversion now..

http://s1057.photobucket.com/user/wingman102/media/IMG_3382Small_zpsd774532a.jpg.html" rel="nofollow">

[/color]

Posted By: Raizer
Date Posted: 15 Apr 2013 at 4:41pm

My 9 ball bolt handle rolled off his bench and the ball shattered soo...

Tacticoooool Cool

http://s1057.photobucket.com/user/wingman102/media/IMG_3388Small_zpsb5932042.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3389Small_zpsa0d409e1.jpg.html" rel="nofollow">

Tested the 5 different species of .25 pellets that I had on hand this morning on paper at 30m, No prizes for guessing which ones shot the best ::)

JSB Exact Kings. 25.4gr
Benjamin Premiers 27.8gr
Predator Polymags 26.0gr
Daystate Rangemasters 36.2gr
H&N Barracudas 31.0gr

http://s1057.photobucket.com/user/wingman102/media/IMG_3393Small_zpsb9b09533.jpg.html" rel="nofollow">

I don't have the strings, but the JSB kings are doing about 600fps on CO2.
"Its screaming out for an HPA kit now!"
"You are guna love it.. the pests are not.."

Also he sent me these pics

:D I think my accuracy problems might be solved now :D

Posted By: nunga
Date Posted: 15 Apr 2013 at 5:11pm

Beautiful is all i can say to that :)

Posted By: Raizer
Date Posted: 16 Apr 2013 at 11:19pm

It just got even better!

Suppressors were the hot topic of the day today..

http://s1057.photobucket.com/user/wingman102/media/IMG_3394Small_zps3bf48fe6.jpg.html" rel="nofollow">

I shot the new .25cal barrel fitted with your old suppressor and the groups opened up to about an inch at 20m.. this wasn't helping your .22 barrel at all.
I fired a bunch of 3 shot groups through various other suppressors off my other rifles and found it favoured the cheapest one of the lot.. a $30 Chinese .22lr muzzle can..

http://s1057.photobucket.com/user/wingman102/media/IMG_3400Small_zps2d97a3a7.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3399copySmall_zpsfaf35430.jpg.html" rel="nofollow">

As you cant shoot your rifle without a suppressor where you are I thought Id better make one that does work.. its an over barrel ported shroud with the same baffle system as the crappy Chinese .22lr can it seemed to like... It is super light at 100 grams and is much quieter than your old one..

http://s1057.photobucket.com/user/wingman102/media/IMG_3407Small_zpsd9c5c92a.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3414Small_zps240bfdb3.jpg.html" rel="nofollow">

And the best part is it really shoots with this lightweight on!..

http://s1057.photobucket.com/user/wingman102/media/IMG_3402copySmall_zps96494d32.jpg.html" rel="nofollow">

http://s1057.photobucket.com/user/wingman102/media/IMG_3405copySmall_zps4a7e5776.jpg.html" rel="nofollow">

It is just a bit shorter in overall length than your .22 barrel with suppressor even though the new .25 BSA barrel is actually 2 inches longer than the original .22 barrel.

http://s1057.photobucket.com/user/wingman102/media/IMG_3415Small_zps542832df.jpg.html" rel="nofollow">

Its boxed up and on its way back to you.. Enjoy!!! Wink

Posted By: Raizer
Date Posted: 18 Apr 2013 at 6:36pm

Got it back today, chucked a full 9oz on and sighted it in.
Didn't get to shoot anywhere near as long as I wanted to, but well I'M IN LOVE!!
Super quiet, super accurate and a real punch to it!!

It almost feels strange hitting what I'm aiming at! haha

Posted By: Raizer
Date Posted: 18 Jul 2013 at 11:13pm

Things have progressed a little since I last posted!

Ran it on CO2 for a while after getting it back, but soon got sick of paying $10-13 for 9oz of gas!
Then this happened

1400psi regulated output JDS Airman HPA tank Big smile

Before fitting that I bored out the gas block a bit to give more volume of regulated air, forgot to take a pic of mine but it looks like this now

Just with a slightly bigger and deeper bore.

Haven't Chrony'd it as yet, but is sure sounds like the pellets are hitting a LOT harder than they were on gas!

Posted By: Raizer
Date Posted: 19 Jul 2013 at 6:28pm

741fps / 30.98fpe Big smile

Posted By: nunga
Date Posted: 20 Jul 2013 at 12:10am

Raizer wrote:

741fps / 30.98fpe Big smile

Pellet type and weight?

Posted By: Raizer
Date Posted: 21 Jul 2013 at 1:01am

Oops, knew I was forgetting something! I use JSB Kings 25.4gr

Posted By: Raizer
Date Posted: 07 Sep 2013 at 8:23pm

I keep forgetting to update this thread Embarrassed

But it's now got a new Airborne Arms valve in it, cock on open mod and puts out just over 37fpe Big smile

It's got the lower valve in it

Breech modded for cock on open, so I don't have to try to hold the bolt open against the hammer spring while loading a pellet

Now to find some possums, or better yet goats!

Posted By: Raizer
Date Posted: 14 Dec 2013 at 8:34pm

Soo lets bring this back up to date then Tongue

At the end of October I had a full length QB78 gas tube arrive from Welsh Willy in the UK/Wales, which I promptly had cut down to 13.75", I also had a breach riser come from Porky on the UK boards who makes all kinds of bits for the QB guns

Ooh and I'd just fitted my new Hawke.

So I quickly got down to putting the pieces together!

Ignore the blue bits, it wasn't until after I assembled it all that I realized I hadn't cut the slots for the cocking handle before painting the riser Angry

Just changing to the longer tube gave a close to 15% power gain, it last chronied at 39fpe with leaking transfer port and bolt seals!

And after a long wait my new QB78 stock finally arrived from the UK :D

I've only done a rough job with the dremal on the inletting for the gas block so far, which is why the tube sits higher at the front of the stock than the rear.
Will tidy it up nicely when I've got a good sharp chisel!

It's soo much more comfortable for free standing shots!!
I always used to have the air fill fitting digging into my forward hand with the short tube.

I'm also thinking about making the cheek rest height adjustable, and possibly painting the stock black? (or coating in bed liner?)
I was originally going to ebonize the stock, but this one was not a winning ticket in the Chinese stock lottery, can see a big patch of filler under the finish and there's no telling how deep it goes

Just waiting on a meter of alloy tube I've ordered to arrive, then I'm going to attempt making a 30mm full length over barrel suppressor :)

Posted By: nunga
Date Posted: 16 Dec 2013 at 11:07am

Nice :)

Posted By: patcheye
Date Posted: 20 Dec 2013 at 5:56pm

I thought about buying a QB79 just a while back, but couldn't find any in all the usual airgun shops etc. Typical isn't it? You finally decide to get one after all the good things you hear about them and ther's none around...

Whether they're all sold out or nobody is bringing them in anymore, I don't know, but I just cannot find one...

I certainly like what yours has become.

Posted By: Raizer
Date Posted: 20 Dec 2013 at 7:25pm

Yeah they do seem hard to find at the moment I'm sort of looking for one as a base for a gun for the misses and can't find any either!
The other "problem" is they only ever seem to be in .177 too.
I'm thinking I might have to buy another .22 from the States or even the parts to put all my spares together Smile

Posted By: patcheye
Date Posted: 21 Dec 2013 at 5:09pm

Hey, if you do decide to get one in, give us a yell. If you ever want to beef another one up to those above specs, give us an even bigger yell. That energy level really caught my eye...

I haven't been haunting to many airgun forums of late because of other things happening but I will keep a better eye on this one from now...

Posted By: Raizer
Date Posted: 21 Dec 2013 at 6:09pm

Will do mate, should be able to get a price break on 2 or more.
Always happy to mod a QB, I can't do valves like mine as it was made for me, but I know a few ways to get good flow through the stock valve.
I tunned up Seppo's .177 from around 5fpe to over 15 with 10.?gr JSB heavies :-)

Posted By: patcheye
Date Posted: 21 Dec 2013 at 6:52pm

Hey, still good though - 15 compared to 5 ft-lbs...

I'll keep a little purse aside incase I get the chance to get ahold of one. I've been reading too many good things about the QB's to turn my head yet another time. I like the idea of the moderator on them too.

If you get a good price just PM or email me and I'm sure I can get some money to you asap... If you want to play with and tickle it up a bit, I am in no particular hurry. I'd rather wait and get a nice one and cross your palm with some coin for your troubles...

Cheers...

Oh if you want my email address just say so and I'll PM you...

Posted By: patcheye
Date Posted: 01 Jan 2014 at 12:04pm

Update...

I might have to wait a while on this. I guess I just overpsent a little and the pockets are now a bit in the stretched side. Sorry for inconvenience...

Posted By: ghce
Date Posted: 26 May 2014 at 12:01pm

How long is the Knibbs BSA .25 barrel?

Graeme

Posted By: Raizer
Date Posted: 27 May 2014 at 3:36pm

It was 24", but BSA no longer sell blanks Unhappy

Posted By: ghce
Date Posted: 27 May 2014 at 5:27pm

Thats a complete bummer, I wanted a 24 inch QB .25 barrel.

What was the Knibbs cost? perhaps they still have some.

Graeme

Posted By: Raizer
Date Posted: 27 May 2014 at 6:35pm

It was under $200nz delivered, that was including a couple of Hatsan breach seals.
http://www.airgunspares.com/store/product/8676/BSA-Barrel-Blank-.25-Blued/" rel="nofollow - http://www.airgunspares.com/store/product/8676/BSA-Barrel-Blank-.25-Blued/

Posted By: ghce
Date Posted: 27 May 2014 at 10:55pm

Thanks for that link, I see Knibbs have finally updated their old website Smile

I did notice however they have Lowther Walther blanks in .25 that are 26 inches in length for reasonable cost however unchoked and I do love BSA swaged barrels

http://www.airgunspares.com/store/product/6099/Barrel-Blank-.25-Cal-26/" rel="nofollow - http://www.airgunspares.com/store/product/6099/Barrel-Blank-.25-Cal-26%22/

Those extra 6 inches over a standard 20 inch QB 78-79 at .25 Cal would make a significant difference to the FPE using CO2.

Graeme