Ever since I bought my Tau I have been wanting something with just a hair more power. I have a Career 707 II in .177, but that gun is no fun to tote around and even on low power seems like pounding a thumbtack with a sledge hammer. My B26 is a good mid ranged powered springer, but I wanted a little something that ran on gas. Biggest problem with CO2 in my neck of the country is the large fluctuation in temperature. During the Winter a CO2 gun will spray "snow" out of the barrel and the pellet will arc towards the target, during the Summer the gun will valve lock then fire a few really hard shots then if it sits for a few minutes valve lock again. What happens then is your velocity is all over the place and accuracy suffers. So when I decided on a new mid range gun I didn't want to go with CO2. There is a coversion to convert my Tau to PCP, but then I feel I would have molested a perfectly good match rifle. So I finally decided on another QB78. I have owned 2 of these guns previously, but they were both CO2 powered, this one I wanted to run on air, not CO2. I went and dug through posts on various forums about the PCP QB78's, and the ones running on bottles. The PCP QB's don't appear to have very consistant shot strings just yet. Most I have seen have a good well tuned "bell curve" shot string, which looks real good, but the sweet spot in the strings is usually fairly short, like 10-20 shots with a fairly high FPS spread from start to finish. The QB's running on regulated bottles really caught my attention. The idea is to run a high pressure air bottle on the order of 3000psi, then regulate that pressure down to 850 psi which is pretty close to CO2 pressure on an average day. The 850 output pressure stays constant until the pressure in the bottle drops below 850psi, so it stays really consistant through the better part of the shot string. I dug once again through various posts on various forums, including some paintball websites (paintballers come up with this stuff much sooner than airgun guys, it's just a much larger sport). I found that most people were using either a 13ci tank, a 22ci tank, or running a standard bulked QB on a remote line with various sized bottles. I want a self contained gun, no remoite bottle to lug around with the gun, so the 13ci or 22ci tanks were what I was after. I found these two tank sizes once again by readfing the forums from a company called Wevo paintball (
http://wevopaintball.com). I found the bottle, now I looked around for a regulator, a bottle by itself is just an empty vessel, nothing to connect it to the gun or regulate pressure. I found a regulator for a decent price on Ebay, put it on order, as well as the Wevo tank, and then I started thinking about which QB variant I was gonna work with. I wanted to try out the target stock of an AR2078 a long time ago and never really got over that wish, so I ordered a TF79T from Compasseco, same gun, but with a tank block installed for screwing a tank into and a slightly shortenned stock at the fore end.
Recieved my gun first, Compasseco did a real good job of shipping it out real fast, kudos to Compasseco. The regulator I ordered came in within a few days also, but the bottle took awhile, Wevo is a pretty slow shipper. USPS showed electronic confirmation for a good week before they actually had the package in hand. I wrote Wevo and they said it was shipped, but I still believe that it sat at the back door waiting for pickup for awhile. While I was waiting for the bottle I hooked the gun up on Airsource CO2 so I could shoot it a bit. I really like the target sights on this variant of the QB, they are actually as good as my Tau diopeter sights in quality for the most part. I shot a few dozen shots this way before I realised how small the target stock is. I think the LOP on that stock is somewhere around 13 1/2", too small for an adult. I like a short LOP, but closer to 14 1/2" is more comfy to me. I took the stock off and worked on it in the shop for a couple nights and came up with a pretty comfy setup. I added 1" to the butt, and also added 1" to the fore end to cover a bit of the regulator. I also reshaped the grip area, there is a "bump" that sits right between your middle finger and trigger finger that just rides the heck out of your hand....that was the first thing I sanded off:) The stocks come with a rather thick coat of stain/shellac. It's looks pretty good, a little shiny for my tastes, but there were some obvious runs on it too...so I sanded all of that off in the hopes of refinishing the stock in blonde. Unfortunately the more I sanded, the more I uncovered wood filler, and a dark redish wood filler at that. If I wanted to refinish in blonde I would definately have some growing pains....I honestly didn't think the final product would be worth the effort, so I decided on a bedliner coating.
The TF79T as well as the other target variants of the QB have a pseudo "2 stage" trigger. This trigger is achieved by having a hinged/sprung trigger blade that pulls to its full travel before the actual sear area moves. It's a really simple design, and not all that unpleasant, but it can be made much better. I don't own a trigger force scale, but I would rate trigger pull as better than a Crosman 2240, but alot smoother and not so squishy. With a little work these can be made into really great triggers. I pulled a few Goo Gone cleaning patches through the barrel, a dozen or so came out really dirty, then started to clean up a bit so I ran a few clean ones and stopped there. I used the idea of weedwacker line to pull patches through as explained on Bob's website (might be in the library here also?). The rifle itself wasn't too dirty, just a simple wipe down with a silicone cloth and it was fine. The bolt is very smooth and functions great, I've had other QB's with rougher actions, so this one should be real nice after it's cleaned up.
I never chronied the gun on the CO2 Airsource tanks, but I finally chronied it today under HAP with the Wevo tank and regulator installed. This is a bone stock gun, I haven't even changed the transfer port yet. The only thing I have done to the action was remove it from the stock, removed the barrel to allow the reulator to mount (the fill nipple and gauge will hit the barrel when screwing it on), reassembled, aired up, leak checked, found a leak by the pressure gauge, teflon taped, aired up again, leak checked overnight, then finished the fill to 3000psi. So no internal work has been done, my results should be fairly typical for a QB tanker running on 850psi regulated air.
When I chrony I do strings of 12, then throw out the highest and lowest shots which are probably malformed pellets, so I end up with a good 10 shots per string. I chronied 2 different pellets in the gun for a total of 24 shots, 12 of each pellet. Pellets used were the Crosman Premier Heavies 10.5 grain in the bulk box, and Gamo Match Wadcutters 7.56 grain in the tin. I am really happy with how consistant the numbers are, even the hi/low numbers I threw out were close, like within 2 fps of the others. With a little work this gun should fit well with the rest of my small collection. Here's my chrony strings:
I'd like to get into the low/mid 800 fps range with slightly heavy domed pellets, not sure if I can, but I will try. Nice gun for the money invested. I may do another one of these in .22, but next time I will use a standard QB79 tanker, the extra cost for the stock just wasn't worth it. The accuracy is pretty good, but unlike most people I find mine a little bit pellet picky. I will do a post-tune review and hopefully find just the right pellet by then. The RWS Supermagnum Wadcutters shoot pretty well, as do the Gamo Match Wadcutters, the Crosman Heavies are a close 3rd.
