Air Gun Home :: View topic

radar · Silver Status Member

It’s here! A QB78 Deluxe from Archer Airguns.

With the Archer Airguns XP tune kit packed with it.

With the Gold Service add-on, they check it out and tighten any loose screws, fix anything that might be wrong with it, and give it a 10 yard, 10 shot target string with chronograph results. This one showed C-C 0.5” vertical spread, .25” horizontal spread. Velocity with 13.83 grain pellets; max. 535.54 fps, min. 518.65 fps, average 529.83 fps, std. dev. 5.29 fps. Average muzzle energy 8.623 ft. lbs. The ambient temperature was 58ºF.
Trigger pull measured 2 lb. 8 oz. average. The trigger feels pretty good to me. I can feel the first and second stages well.

I’ll scope it, but the iron sights are decent for open sights.

Fit and finish are surprisingly good, and the rifle feels solid and heavy. The wood is pretty.

The crown looks decent.

The bolt pulling action is just slightly rough but not enough to bother with. I’ll be putting in a new bolt with the tune kit and may polish the bolt tube just a bit—clean and wax the wood, too—and a dot of lube here and there on some of the moving parts. I am impressed with this rifle so far for the money—very impressed. I’m glad tomorrow is Sunday!

SMP · Silver Status Member

Hey congrats....Now comes the fun part.

If your feeling really extra brave give the barrel lapping process a try too. I've done 2 QB's so far and they seem to respond well.

Oh one other point of mention is you might find machining marks inside the first 1/4" of the barrel. You can trim the barrel a touch to get rid of them.

radar · Silver Status Member

Big Ern · Veteran Member

Congrats Radar! Now go enjoy it and let us know how you like it.

Ernesto

oddtodd · Silver Status Member

Is this the one that is a close duplicate to the 2260 that crosman discontinued? I wanted a 2260, but they discontinued it before I could get the money together.

lasabre · Member

Nice QB !!! I own both the 78/79 QB's and have tweaked them a little....well, maybe alot. HA !

I have taken alot of game w/ both rifles.

Give the JSB 15.9 grn & CHP a try.

Alstone · Moderator & Site Supporter

Congrats Radar, you made a good choice. Thumb Up!

Al

rsterne · Moderator

It's a copy of the old Crosman 160 from the 1970s I believe.... hailed as one of the best CO2 rifles ever made....

Bob

robert w · Senior Member

do i see shooting ahead??? looks nice

radar · Silver Status Member

Thanks y'all! I am happy with it. Yes, I believe it was the Crosman model 160 that it reproduces.

Today I put the Archer Airguns XP tune kit in, and did a little cleaning and lubing.
As always, this is just what I did to my rifle and maybe some tips, but not a how-to. Use the instructions that come with the rifle and tune kit. The rifle is unloaded and free of all pressure, of course.
The safety has to be in the “safe” position to knock it through and out with a brass drift punch—left to right from the normal rifle holding position. That is, with the muzzle pointing left and the trigger guard toward you, it taps through going away from you.

I cleaned the stock with WD-40, rubbed it dry, and gave it a waxing. A tip learned from Flying Dragon air guns website.

The barrel band screw and its nut have to be completely removed to slide the barrel band forward.

The barrel set screw comes out next with the 2.5mm allen wrench.

Then the barrel pulls straight out, firmly.

This screw in the chamber is visible with the bolt pulled back. It comes out with its lock washer.

This screw and lock washer comes all the way out and then the 2 tube caps it goes through come out, and the receiver tube/chamber assembly lifts up and off.

A 2.5mm hex wrench again to remove the bolt handle set screw.

The bolt handle slides right out, and the bolt can be removed out the back of the receiver tube.
With the receiver tube/chamber assembly off and the bolt removed, I polished the inside a bit, and gave it a thin coat of moly paste lube.

The new and old bolts—Archer XP tune kit bolt is the bottom one. The front is machined to let gas flow more freely.

The factory breech seal is normally crushed due to its length during assembly. This reduces gas flow as well.

The seal just lifts out. The seat looks great so….

So….in with the new tune kit seal. (The kit includes 2 of all the seals and o-rings, which is very nice.)
I put a little silicone grease on it, as well the new barrel o-rings. When the barrel goes in with its 3 new o-rings, it pushes (firmly) straight into the receiver tube/chamber assembly without twisting it.

Putting it all back together now is the reverse of above. The tricky part—sort of—is lining up these things. With the bolt back in the receiver tube/chamber assembly and it ready to go together, the pins in the lower pressure tube part of the gun have to go into these slots in the bolt. They sometimes need some fiddling with but it will go. The bolt has to be able to be operated all the way or they aren’t in right. Then it can be screwed together.

All done and scoped.

Chrony low:

Chrony high:

Ambient was about 65ºF Average MV was 571 fps with 14.3 gr. Crosman Premier HPs. The accuracy was poor with these, however, and I had good results with JSB Exact 14.3 gr. domed. That reminds me, I have to get some more of those ordered. I guess I bought an extra tin of the CPs for no reason. Oh well they won’t spoil, and the other guns like them so they’ll get used.
The average velocity increase was modest, but accuracy with the JSBs is good and this is going to be primarily a plinker and informal target rifle with a little pest control here and there. I am happy!

rsterne · Moderator

One thing I do on any QB the first time apart is deburr the inside of the breech where the barrel fits.... The holes for the transfer port and the setscrew are usually covered with burrs that shred the O-rings on installation.... After deburring the holes, the O-rings last for a very long time, provided you pull the barrel straight out without twisting.... and reinstall it the same way.... You wlll probably find that the port in the barrel is quite a bit smaller than the hole in your new transfer port seal.... drilling that out will buy you some more velocity as well.... Sometimes it does not line up properly as well, so you have to move it over with a dremel instead of drilling it.... Make sure you deburr the inside of the barrel so you don't damage the pellet on loading....

Bob

robert w · Senior Member

i use birchwood caseys stock conditioner then follow up with birchwood caseyd stock wax love the results get mine at academy and basspro

radar · Silver Status Member

Thanks, Bob. I forgot to mention that when I polished the bolt bore, I went all through bothe sides to debur the barrel end, too. And the whole barrel bore was Flitzed as well.
Yes the hole in the receiver side is smaller than the new seal now that you mention it, but I didn't do anything about that. Maybe later I will if the velocity is not so good when it is cold out. Right now, I'm OK with anything more than the factory velocity.
Oh yeah, I got a good 40 shots out of it before refilling. When the power is ready to drop off, you can really tell by the sound and pellet drop. Within a very few shots it suddenly becomes a mortar.

radar · Silver Status Member

SMP · Silver Status Member

What was the pre tune velocity my man?