GTA
PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : ribbonstone February 24, 2007, 03:55:15 PM
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Decided to order a base QB .22 to modify just one more time. Not going to get too wild...just the basic mods. looking for a good 620-640fps shooter. Have a new spare valve assembly, so will start work on the simple stuff there and just swap out the new gun's valve when it arrives.
But am giving serious consideration to making that keyway exaust opening as I've found that useful.
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I've got a few of the tubes, on rifles I use but can give you the dims. if you want them, any other help is available, what to look out for and dead ends etc. shoot me mail I'll help. Mike
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Thanks for the help. Have a .177 2078 (Archer's numbers) that I can take measments from; may as well make the keyway the same for both. Will have to do the keyway first rather than have to do the tube smooth/deburr twice.
Guess it's the warm weather here...had the co2 guns out yesterday.
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Will test it tomorrow.
Sure is easy when you have some spare parts on hand and time to order the scope/rings and collect all the tools.
Did a careful job with the spare valve during the +week wait for the rifle and just substituted that tuned valve for the issue one. Lots of time polishing, smoothing, buffing, degreasing, etc. Bolt probe enlarged, transfer port alingned, all seals changed, and bolt polished. Might need a little spring tune to get to the 630fps goal, might be there already as it sounds healthy (no obvious leaks, but am giving it an over-night test). Set the trigger to "resonable", figure I'll tune it a little more after several hundred shots....like to set up a wear pattern so I don't waste time smoothing areas that don't rub.
Put on a short (cheap) 2-6X that I'd set to be paralax free at 30yards...simple and the short little scope looks good on the rifle.
Lathed a short LDC that's a simple design and has worked well on other rifles.
Crown looked good...will leave that alone and deal with it only if targets tell me it needs it.
While I was at it, lathed and hardened a couple of extra piercing rods of slightly different designs.
Going to be a super simple rifle....but maybe this time it will look so simple/stock, will be able to hold onto.
Not sure about the stock...looks pretty good when it's wet (had to get that damned sticker off)...good enough that it may just need a little work and not a refinish.
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The basic bottom-of-the-line QB78 has better quaility now than it did just a few years ago...this gun is miles ahead of the last one that crossed my bench.
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Did the stock work today. Inletted a slot for the safey to pass when staning straight down...filed a new flat so the safety would detent at that straight down spot...pinned the safety so it is either straight down (off safe...it lies along the front bow of the trigger guard) or against the stock (but lifted enough to let a trigger finger just flick it off). Nice to be able to take the stock on easily.
Remounted (drill, tap, and epoxy) the front sight to the LDC...it's thin enough that the sight stands low enough to still be zeroed with the issue rear (it 's near the top of the elevator, but it's zeroed at 20 yards).
Finished the stock. Just solvent washed it, 40 steel wool, a bit of stain, buffed, then true oil....stock looks good, but it has lots of filled areas so it won't get stripped and fully refinished.
While the stock was OFF, did the chrono testing.
All test were at 15 feet/70degrees/13.9gr. GAMO match pellets
Almost Stock: (just degreased, internal metal parts polished, and fully cleaned):
578fps
Simple valve mods:
626fps
Top (brass) moded valve and AL standard:
612fps
Bottom modded and top standard:
602fps
Considering that pellet shape, the 5 yards to the chronograph probably cost 15-20fps. from muzzle-muzzle velocity, so I'm pretty much where I wanted the rifle to be (able to deliver 7fpe+ at 50yards).
Looks pretty darned close to stock...finsih is nicer, the safety stands at "hjalf mast", and the muzzle attachment (but adding the front sight to that does help to make it loook more innocent).
Happy.