Mr. Archer please chime in, and any of you other experts on power.
I think the QB bug has bitten, as summer is approaching.
I have my eye on one of those nice carbines, but I have a couple questions.
I noticed on Archers site, that they indicate they are getting the same mv's on the carbines that they do with the regular QB.
~ 500 fps is okay for plinking, but is a little on the low side for hunting, and plinking out to 50yds.
My wish list would be
----650 fps out of 14.3
----Not interested in bulking, carts are fine.
With the Archer power kit, and the HDD, what kind of power can be made with the carbines? Will they go up to the mid to high 600's?
Or do I need the barrel length to accomplish these velocites?
I know that these speeds would change with ambient temps, but summer temps are pretty consistant here. I can count on 65-75 as I do this particular hunting right around sundown.
Ultimately, I would like this converted to a .20 cal.....but can deal with .22 until the funds present themselves.
Yes, on all of your wish list questions. I own both 78 & 79 and both are nice for money. I see your leaning towards the carbine because of it's weight, the standard QB series guns are really lightweight and small. The carbine might be a bit to small for you depending on your size...think about it??
Either mod yourself or buy Archer's pre modded parts.
Shortening the barrel for the carbine reduces the muzzle velocity. But replacing the breech seal brings the muzzle velocity back up to about the same as the factory gun with full length barrel (nominally 500fps at 65 degrees F in .22 cal). That's what I do when I make the conversion. Some will be a little faster, some a little slower, but 500fps is a good average for the CAR78a in .22 cal at 65F.
Adding the XP bolt will give the CAR78a a muzzle velocity of about 550 - 560fps at 65 degrees F. This compares to a muzzle velocity of about 600fps for a .22 caliber QB78 with full (factory) length barrel and XP Tune Kit at the same temperature. The HDD makes no difference to the muzzle velocity, just gives better gas mileage.
I find the carbine MUCH better handling than a full-length QB due to the shorter barrel and improved balance, but it's very difficult to convey this in words
Sorry that I can't promise to make your wish list muzzle velocity, but these numbers are typical of results I've found from testing a zillion of these guns.
Of course, there are other muzzle velocity mods that we don't offer to gain more fps - such as opening-up the barrel gas port and "free-flowing" the valve. You could probably push the little carbine up to 600fps with this sort of additional work...
That was done with just a dremel and a hand drill. I do advise a lathe to do the probe, even better purchase the XP tune kit from archers and not have to worry about recking the bolt.
Others are getting much more then I but this is not bad considering no tools but a dremel and a Drill etc. At 85 with 14.3 cps It should do about 740 FPS. at 69 F is already peaked just about 16 ft-lbs (14.3 cps peaking at 710 fps). Once I get the HDD I hope to have more fun with this. Unfortunately is pretty cold so can only shoot inside right now. Without the HDD it is wasting alot of CO2 so it will be nice to recieve the hdd.
The QB is a realy kewl air rifle with lots of potentional for over stock velocities very easily. Goto archers, pick your qb style, add the XP Tune kit and HDD and your almost ot your goal. If not opening up the barrel port will help and you can easily do some valve work if you want.
If you are thinking about bulking the ar's might be a better price point and you get the target stock! But then its a little bit heavier.
This message has been edited by bruce.itterman on Feb 15, 2011 10:05 AM
what are your thoughts on the barrel length of the carbine?
I know very little about co2, I have a couple pcps, but I havent done any mods to them.
I can easily see where Archers kit would make all the difference (and adequate speed) to get to 12ftlbs.
My worry is, buy the carbine, buy the kit. I would think the HDD is a no-brainer, and would certainly include it. Just dont want to get the gun and kit only to find that I cant make the same power. I would go for the regular.
No AR, I do not fancy c02 enough to bulk. Just want to be able to load a couple 12's and get some good plinking, and occasional hunting.
I would be happy with 13ftbs---just don't want to get the carbine and turn it into a gas hog.
Do you know anyone who has the carbine, and the kit?
Yes, the gun just looks comfortable. Not a bad price for a compact gun, if it can hit 12fp easy, then it is very worth it. Great "3 wheeler gun".
-The higher the velocity the more gas per shot will be used. With the current tune I expect about 30 shots from 2 carts. Hopefully the HDD put it back to about 40-45 good shots.
-The HDD will help with co2 milage definitely the way to go in my eyes.
-To decrease gas usage, I believe a lighter striker is needed. I will be going there soon, just need to wait till I can get or use the correct tools. The trick is to lighten the striker such that velocity is not affected, and play with the striker sping at the same time. A ligther sticker will decrease the effectiveness of the HDD as it willl have less bouce. But a lighter striker often needs increased spring preload from everything I have read here. The higher the spring load the less effective the HDD is so everything is a balance between power and effiecency.
-Valve mods are really need to get top velocites, but moderate velocites can be had with the few minor tweaks mentioned above. (XP tune kit, Breach seal and barrel port opened up some, aligning all the ports for perfect smooth flow)
-Go .22 if you need power .177 won't get there as easy and is alimiting factor for effiecncy and power.
-The more effiecent the co2 usage the less the cooling effect and the more consistant the velocity of a co2 gun.
-Now the trick is to put all this together in a system that works together and is balanced. There are many experienced tuners that can do that for you. For example opening up the barrel port does not do also much if you don't probe the gun (drilling the probe out to 5/32 helps but the bold becomes a limiting factorfor constricing flow). If nothing else is done not much sense in valve mods. The idea for a tun to to do everything such that it works as a single unit and balance is needed. Open the barrel port to much and the pellts drop in and block... as real pita and not the easiest fix.
Another option if you want lots of power is HPA, I have no experience there but their are lots of peeople here that can help you.
I don't know what effect the shorter barrel will have but I know most co2 guns can get nice improvments in velocy just going to a longer barrel. Maybe get a 830FPS tune and start cutting an 1" at a time off the barrel till it is as short as you want, or hits the min velocity you want? Don't forget a re crown will be needed etc. Might be more a job for a pro tuner or start with the Archer carbine and live with the max you can get?
I think your list would get you there or close, but the combination of a wide open valve body(possible even on cartridges, I think)and a light striker gets the peak pressure to the pellet fast..which, IMO, is even more important with short barrels.
This message has been edited by classicalgas on Feb 16, 2011 9:33 PM
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