QB79 HPA build for GTA member

[Buldawg76]

Jason
That's what I was wanting to see as I thought it had to be off the side of the retaining hole like it shows and yea if spring is binding on the guide at all is occurring it does not show in the shot string on UCChris's rifle you built him.

By the way very nice work and has given me a lot of clear direction for my build to proceed with much more certainty.  I am not going for a power house just yet but rather a FT gun to shoot JSB 10.34s at 900 fps for 60 plus shot to shoot an entire match plus sight in on one fill.

I have a FDPCP 60C in 22 that I am looking at installing a ninja bottle on it to max it out for the power you got from UCChris's gun as it shoots 15.89s at 900 fps now but has a spread of 860 up to 900 and back to 860 for 30 shots at a 2000 psi fill so while not bad it can be improved considerably with a tank and some more modding IMO.

Thanks for the pic of the RVA.

Mike

Mike

[UCChris]

As some of you may know, I had to sell this rifle in order to pay for college. However, it is back on its way to me! I'm planning to update the look of this gun, so stay tuned.

[Buldawg76]

Chris
Well hate you had to sell it but then glad you got it on its way back as well so it apparently all worked out for the best.

Mike

[UCChris]

Chris
Well hate you had to sell it but then glad you got it on its way back as well so it apparently all worked out for the best.

Mike

Agreed. I owned several guns in the interim between selling it and getting it back, some of them quite nice. But I compared them all to the QB, and they all lost.

[Buldawg76]

Chris
Yea I am just on my first QB build and hoping it will turn out as good as all the reports I have read here about them. Got my bolt probe and valve all done modding and working on the cock on open, RVA and tank block mods to be completed and ready for tuning.

I started with a QB 78 and am going for a 177 caliber FT gun shooting 10.34s JSBs at 900 fps so I  can shoot an entire match plus sight in on one fill.

Then I will go after the power house mods if this one turn out as expected. I have a Flying dragon PCP in 22 just begging for the 30 fpe mod with a tank installed to up her shot count over the 30 I get now filling to 2000 psi and shooting JSB 15,89 at 860 up to 900 and back to 860 for 30 shots at 28.89 fpe now but only for about 5 shots on the knee of the curve so only needs a little valve work and the regulated bottle to get the 30 fpe with double the shot count for a nice hunting gun as it is a tack driver now as is just to big a ES for consistent POIs.

Mike

[UCChris]

Chris
Yea I am just on my first QB build and hoping it will turn out as good as all the reports I have read here about them. Got my bolt probe and valve all done modding and working on the cock on open, RVA and tank block mods to be completed and ready for tuning.

I started with a QB 78 and am going for a 177 caliber FT gun shooting 10.34s JSBs at 900 fps so I  can shoot an entire match plus sight in on one fill.

Then I will go after the power house mods if this one turn out as expected. I have a Flying dragon PCP in 22 just begging for the 30 fpe mod with a tank installed to up her shot count over the 30 I get now filling to 2000 psi and shooting JSB 15,89 at 860 up to 900 and back to 860 for 30 shots at 28.89 fpe now but only for about 5 shots on the knee of the curve so only needs a little valve work and the regulated bottle to get the 30 fpe with double the shot count for a nice hunting gun as it is a tack driver now as is just to big a ES for consistent POIs.

Mike

The good news is that you are using a 78 tube, which means you can use a lower psi setpoint to achieve the 19 fpe you are after since you have a giant plenum compared to the 79. I would start at a psi setpoint of 1100 fps. Also, if you can get a half decent efficiency out of the gun, you should get 100 shots or so.

[Buldawg76]

Chris
That sounds good as I have a pro SHP reg already set at 1100 psi output. I have opened up the probe to .140" for the port hole and .125" for the probe passage hole and cut away the valve nose with two 3/8" slots down the sides and a 3/8" center hole where the piercing pin was, also replaced the poppet head with and older crosman 2240 brass head that is stepped and uses a delrin seat on the valve seal area and opened up the throat to 9/64' with the valve port angled and rounded.

Next is the cock on open mod and installing the tank block and RVA screw hole but may go with a crosman end cap so I can keep the adjustment screw centered instead of off set. since I have several end caps on hand.

Mike

[UCChris]

Chris
That sounds good as I have a pro SHP reg already set at 1100 psi output. I have opened up the probe to .140" for the port hole and .125" for the probe passage hole and cut away the valve nose with two 3/8" slots down the sides and a 3/8" center hole where the piercing pin was, also replaced the poppet head with and older crosman 2240 brass head that is stepped and uses a delrin seat on the valve seal area and opened up the throat to 9/64' with the valve port angled and rounded.

Next is the cock on open mod and installing the tank block and RVA screw hole but may go with a crosman end cap so I can keep the adjustment screw centered instead of off set. since I have several end caps on hand.

Mike

The more porting the better and it looks like you're on the right track. The better the rifle can "breathe", the less air you are going to have to use to make your velocity goals.

[Buldawg76]

That's my goal is to get the power level I want on the least amount of air per shot as I need 60 shots for the match plus 20 or so for sight in before the match. Can always top up before actual match so at least 60 shot on a fill is a requirement for the build.

Mike

[Buldawg76]

Oh and opened barrel port to .140". Also and will be using 3/16" ice maker tubing as a TP port seal. So now I am just trying to decide on the actual length I want to cut the tube down to for the tank block or if I want to use the factory CO2 fitting drilled out to accept a 1/8" pipe thread elbow and turn the tank around backwards and mold into the stock for a shorter more compact look and feel.

I eventually want to get an AR 2078 stock to put the action in for a better FT platform target style stocked gun so still deciding on some more options at this point as well.

Mike

[UCChris]

She's back in my hands and boy, how I've missed her!

[Monkeydad1969]

Looks good, Chris.

Joe

[mackeral5]

Very nice.  I can name a couple of guns that got away and I wish I could get them back.  Congrats!

[Buldawg76]

Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike

[UCChris]

Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike

It's just Krylon camo paint. Two coats of primer, two coats of paint, and I'm still working on the satin polyurethane coats. I just threw it in the stock for a pic.

I'm assuming the 79 is regulated? If it has a power adjuster on the back, I'd screw it in all the way and see what type of speed you can get. If it doesn't and is running the Ninja SHP tank @ 1100 psi, bumping it to 1450-1500 should get you the fps you're looking for. Playing with the hammer spring is ideal though. You want the lowest regulator set point possible for the fps you want. That way you are getting the most shots possible. Ideally, you want the gun to max out at 15-20 fps higher than you want with the power adjuster screwed in all the way. That way, the fps you are going for is on the knee.

[Buldawg76]

Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike

It's just Krylon camo paint. Two coats of primer, two coats of paint, and I'm still working on the satin polyurethane coats. I just threw it in the stock for a pic.

I'm assuming the 79 is regulated? If it has a power adjuster on the back, I'd screw it in all the way and see what type of speed you can get. If it doesn't and is running the Ninja SHP tank @ 1100 psi, bumping it to 1450-1500 should get you the fps you're looking for. Playing with the hammer spring is ideal though. You want the lowest regulator set point possible for the fps you want. That way you are getting the most shots possible. Ideally, you want the gun to max out at 15-20 fps higher than you want with the power adjuster screwed in all the way. That way, the fps you are going for is on the knee.

Chris
Yes it does have the pro SHP reg on it and as far as I know is still set at the 1100 psi factory set point but I am going to test it and see just what the output of the reg is right now. It has the cock on open mod but no RVA screw in the end cap so the spring would need shimmed for more tension if its not already at max preload. getting ready to check that as well. I have some 2240 end caps that I am thinking of drilling and threading for a RVA screw so it will be in the center of the spring guide block and would rather increase hammer spring preload than up reg pressure to keep the shot count as high as possible. Time to play with settings and see what I can get out of it since I am wanting 890 to 900 fps max from it.

That stock is looking good and should be nice once you get the urethane coats on it to seal it from the elements.

Thanks for the info and will let you know how it turns out.

Mike

[UCChris]

I'm looking forward to seeing how your build turns out. Keep us updated.

As for my QB79, I am working on making an adjustable comb kit to drop into it in addition to having a half shroud made for it. This thing is going to be stunningly gorgeous when I'm done. The half shroud should arrive sometime next week and I'm hoping to have the adjustable comb kit made up by then so I can unveil it next weekend at a group hunt I'm going to.

[Buldawg76]

Well the hammer spring was at almost full preload and was able to add one 1/16" shim under spring and it still cock so it will either be what I need or another spring will be required to add more tension or cut the guide rod off about 1/4" to allow more preload. Going to test the reg output pressure tomorrow and if its at 1100 psi and if it is will up it to 1200 to 1300 psi and see what it does for increasing the fps of the 10.34s to get close to 890 or 900 fps.

Not sure why you stated to shoot for 15 to 20 fps above desired fps since with reg it will stay constant to the set fps until it falls off the reg  is that not correct since you really don't have a knee in the curve with a reg until it falls off of it or am I mistaken in my thought process on how the reg should work.

The adjustable comb will be a nice addition to the target stock and as far as the half shroud I have found this one on ebay for 20 bucks that is 3d printed and is a perfect snug slide on fit for the QBs barrel and work very well to quiet it down considerably and adds little to no weight to the gun at all.

http://www.ebay.com/itm/331815546678?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It shows as sold out but it also shows to be relisted so check it out in a day or so and it should be relisted for sale, I am very pleased with it for the price.

Mike

[UCChris]

Even with a regulator, there is a sweet spot in the tuning process. This is called the knee. You see, if you crank the hammer spring as much as possible, there will be a point where, no matter the force you hit the valve with, there will be a maximum velocity that is limited by the PSI and volume of air allowed into the plenum by the regulator. Other things play into this such as valve/transfer port diameters, medium used in the rifle (CO2 vs HPA vs Nitrogen), etc. But those factors are over my head. Anyway, this maximum velocity is called the plateau.

The only way to get it to go faster is with either a) more air volume (more plenum or longer barrel) or b) more pressure (higher reg setpoint). Furthermore, at some point, the only practical way to increase speed will be with more pressure, since none of use are going to put a 40" barrel on our rifles, nor are we going to put a 500cc plenum in our guns. However, that's not what we're worried about. We're worried about what lies below the plateau.

What you want to do is find the plateau (fastest speed possible with the pressure/volume of air in the plenum) and then back off that about 10-15 fps. That is called the knee in the regulated tuning process. This is where, according to Bob aka rsterne, the regulated gun will be most efficient.

Good find on that LDC by the way. That's a very affordable option for those who are doing these HPA conversions for the money to performance value. I wanted something a little more flashy so I got a 10.5" long half-shroud done with a carbon fiber exterior. That along with the comb adjustment is going to make this gun look much higher dollar than it really is. Though, it deserves to look like a $1500 gun since it performs like a $1500 gun, after Jason worked his wizardry on it.

[Buldawg76]

Chris
Ok I see what you mean as its the same as tuning without a reg only the fps variation will be far less since the volume and pressure are more constant in the regulated gun. So I am at max spring preload now without heavier spring or cutting guide rod to allow more preload on current spring. so still need to see what my reg is set at now and shoot some test shots to see how much over the string of 770 to 777 fps for 20 shots I got today from it as received.

If I gains some in fps with the spring set at max preload then I will go up in reg pressure to get it at 15 or so fps above my 890 to 900 goal and then remove one shim from spring to put it on the knee and at the 890 to 900 fps goal. If it all goes as planned and if not then I will add a RVA in the end cap to be able to fine tune to the knee of the curve.

Yea I am like you and want to build my gun to look like a much more expensive gun than it really is and I have a FWB 300s stock that is broke at the knee that I am going to get fixed and inlet it to fit the 79 in so it will look like a 300s from a distance but will be HPA instead of a spring 10 meter gun. I do have two 300s that I use in my FT matches that do indeed make it out to 55 yards quite well since they are tuned up to shoot 10.34s at 590 fps and 8.44s at 675 fps. They are just to heavy for me for the off hand and kneeling lanes and is why I am building the QBs to be able to do better in those lanes.

Thanks Mike