GENERAL DISCUSSION
 


  << Previous Topic | Next Topic >>Return to Forum  

Hot Rod QB78

September 23 2016 at 9:48 PM
No score for this post
bReTt  (Login CBPeter)
from IP address 173.14.241.209

 
Hey airgunning brothers!

I have been working on a little project over the past few weeks and it's close enough to done to be able to share it with you all.

Let me start by saying that I wanted something a little "different" than the traditional airgun/gun look meaning, the color brown! Ha ha ha!

This rifle is .22 caliber and started out as a stock QB78 using two 12 gram CO2 cartridges to propel the pellet. I'm not a very good note taker so I can't recall what it shot in stock form but that doesn't matter because it wasn't long after first receiving it, I opened it up and started to get more from it. Not huge power but a moderate increase with simple modifications to increase performance.

I had it in this modified stock state for a while and enjoyed it but I really enjoy spring guns so it didn't see much action especially having to use the CO2 carts all the time. I recently decided to convert it over to HPA with a bottle. After some internet research and questions asked and answered, I started into the project.

Converting to air required some modifications to the action and the stock and after some internet inspiration, this is what came out of the fire. I still have tuning to do to it to get the most out of it but I can go,out and enjoy shooting it and having something unique of my own creating!

It shoots 15.9 gr JSB at 745 fps average for about 19.5 fpe. I'm only getting about 40 shots per fill so I need to work on the efficiency but it's still fun.

photo 20160919_153724_zpsoohkirqn.jpg

photo 20160919_153416_zps1vubt94n.jpg
Brett

 
Scoring disabled. You must be logged in to score posts.Respond to this message   
AuthorReply
Bryan E.
(Login BEnoch)
99.30.74.121

Pretty Cool looking rifle

No score for this post
September 24 2016, 10:56 AM 

Sure not your typical looking rifle now Brett. Great job. I'm guessing you'll be getting more requests from the kids to help pretty up their gun now.

That's a good bit of power too! Almost 20 fpe.

I liked the pics on the yellow showing the stock mods. I'm sure it would be of interest to many here.

Thanks for posting the pics!



    
This message has been edited by BEnoch from IP address 99.30.74.121 on Sep 24, 2016 10:56 AM


 
Scoring disabled. You must be logged in to score posts.

Fangster
(Login LOBOWHITEFANG)
Owner
75.66.12.181

Nice

No score for this post
September 24 2016, 1:58 PM 

Got to say that stock is different. Looks very good.
I'm sure that conversion from the cartage to HPA took some work.

Many are enjoying the QB modded to real air.

Check out my latest on the PCP page if you get the chance.

Another great Job and great share.
FANG
JUNKYARD AIRGUN'S

 
Scoring disabled. You must be logged in to score posts.

TMurray
(Login bustachip)
45.36.116.171

Fantastic job on your QB78....

No score for this post
September 24 2016, 3:54 PM 

great details on the stock...looks like a custom benchrest stock (which it is
custom since you made it). Shooting pretty strong too, what do you use to fill the
bottle with?

You do good work Brett.

Regards, Thomas M.

 
Scoring disabled. You must be logged in to score posts.

Mike Ellingsworth
(Login 4888blues)
184.166.244.115

That looks really cool lol nt

No score for this post
September 25 2016, 9:03 PM 


 
Scoring disabled. You must be logged in to score posts.
bReTt
(Login CBPeter)
174.21.145.40

Thanks All!

No score for this post
September 26 2016, 8:34 PM 

I am still playing with spring and hammer settings to dial it in. I'm thinking 750 fps is max for the 850 psi regulator pressure. I really need to figure how to get rid of hammer bounce! That is the wasting of air, I am pretty sure of that. Maybe a higher reg setting will help some with that or possibly more spring in the valve? Just thinking here. I know that the higher reg pressure will increase the fps output so maybe that might be a good thing to try soon.

Thanks for the kind words!
Brett

 
Scoring disabled. You must be logged in to score posts.
bReTt
(Login CBPeter)
174.21.145.40

Here is some pics of the stock mod process should anyone be interested.

No score for this post
September 26 2016, 8:36 PM 

That I modified. Here are some progress pics to see kinda how it went. I was inspired by benchrest rifles for this look.

photo IMG_7230_zpsks66okgu.jpg

photo image_zpslg4enrvx.jpeg

photo image_zpsrc4xbiam.jpeg

photo image_zps8uegkhrb.jpeg

photo image_zpskyzjj34a.jpeg

photo image_zpsu5ki8rx8.jpeg

photo image_zpsveu878rq.jpeg

photo image_zpswoktf5ur.jpeg
Brett

 
Scoring disabled. You must be logged in to score posts.

TMurray
(Login bustachip)
45.36.116.171

I know not of the inner workings of PCP's.....

No score for this post
September 26 2016, 9:15 PM 

good luck on that Brett...LOL, but how about a heavier hammer and spring?

Regards, Thomas M.

 
Scoring disabled. You must be logged in to score posts.

Fangster
(Login LOBOWHITEFANG)
Owner
75.66.12.181

Striker

No score for this post
September 26 2016, 9:23 PM 

How much striker do you have adjusted in the gun. 120 bar might be where you want the regulator set at. 1750 psi may be much for your set up.

Most if my regulated are set at 120 bar. That is .20 up to .357. Marauder .177 is set up around 130 bar.

Then there is always transfer port sizes and hammer weight to concider?

Pcp is fun and pcp has many adjustments that can be done.
FANG
JUNKYARD AIRGUN'S

 
Scoring disabled. You must be logged in to score posts.
bReTt
(Login CBPeter)
65.102.181.176

Thanks Thomas!

No score for this post
October 3 2016, 1:05 AM 

I use a PCP pump to fill the tank. I fill it to 3000 psi and now that I have tweaked on the rifle some, I am getting about 80 shots! Huge improvement over the initial set up. Pumping isn't that bad, don't let'em fool ya!
Brett

 
Scoring disabled. You must be logged in to score posts.
bReTt
(Login CBPeter)
65.102.181.176

Hey Fang

No score for this post
October 3 2016, 1:23 AM 

The regulator on the tank is set to the stock 850 psi. I can't really verify that it is accurate since I don't have a way to check it. I just trust that is where it is from the manufacturers listing on it.

The hammer spring tension was stock, whatever that is. I did modify the valve and I believe that the tension on the spring was less than stock because of the modification that I did changed the spacing between the spring ends. I added a spacer to increase the spring tension in the valve hopefully resisting the bounce back of the hammer after striking the valve shaft initially.

I also cut some of the hammer spring but added spacing back since it wasn't enough to get the air needed to propel the pellet. There was nothing scientific about what I did, just trial and error until I found something that worked. I must have found a good spot for everything since I doubled the shot count and only gave up about 10 fps average for power.

I may increase the regulator pressure to 1000-1100 psi someday to get the fps increase but that will be the upper limit of what I will be comfortable with in this particular rifle. When I do that I may have to play with spring tension again to get the most out of it, we'll see.

Next issue is the accuracy......
Brett

 
Scoring disabled. You must be logged in to score posts.

Fangster
(Login LOBOWHITEFANG)
Owner
75.66.12.181

Conversion

No score for this post
October 3 2016, 2:43 PM 

Looks like you are on the right track with you conversion. Trail and error is the game on getting the correct perticulars for the best use of your air and fps. Regulators are different in set ups for psi. They even have a brake in time to do a final setting of psi. Having a gauge between the valve and the reg helps or a reg testing device prior to install. But that some times can not truly be your setting once installed.

Should be plenty of info on the net to aid you on the QB. Many have done as you on conversions of that gun.

Good job!
FANG
JUNKYARD AIRGUN'S

 
Scoring disabled. You must be logged in to score posts.
 
  Respond to this message   
  << Previous Topic | Next Topic >>Return to Forum  
Find more forums on SportsCreate your own forum at Network54
 Copyright © 1999-2017 Network54. All rights reserved.   Terms of Use   Privacy Statement