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All Springer/NP/PCP Air Gun Discussion General > "Bob and Lloyds Workshop"

My .257 Condor Build

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rsterne:
I got a screaming deal on a good used .22 cal Condor a month ago, c/w a Hawke 6-24 x 50 SF Scope and BiPod…. I have never had one before, so it will be a bit of a learning experience.... As it turns out, I also bought a .257 cal 14" twist TJ's barrel that was 1/2" diameter and 26" long, which I didn't really have a home for, and it hadn't even arrived when I bought the gun.... It was deserving of a good home, so I decided to convert the Condor to .257 cal, it just seems a better fit than a .22 cal in such a powerful platform....

Lloyd Sikes offered me a piece of 14mm ID x 23mm OD carbon fibre tubing for a barrel sleeve, so all I had to do was shim the barrel up to 14mm.... I had a piece of 1/2" ID x 9/16" OD carbon tubing here left over from my Model Yachting days, so I glued that to the barrel and then sanded it down to fit inside the large 14mm ID tube.... I also got a short piece of .45 cal barrel that was 5/8" OD from Lloyd to use as a shim for the part behind the collars that the hammer slides on, and drilled it out to 1/2" ID to slide over the barrel, and Loctite'd it in place.... I made two new collars from 6061-T6 aluminum, turned to fit inside the Condor tube (1.010" OD)…. The front one was drilled out 7/8" ID and the rear one was 1" long, with the rear half drilled to 5/8" like the Condor collar.... but a recess in the front drilled 7/8" ID by 1/2" deep.... I then turned the rear part of the 23mm OD carbon tubing to fit inside the collars, and ended up with these parts....



The back inch of the 23mm CF tube is drilled to 5/8" to slide over the CrMoly tube made from the .45 cal barrel.... In this way, the end of that 5/8" steel tube stops inside the CF tube, and the OD of the tube fits inside the rear collar.... so nothing ends at the same point to spread out any possible bending loads in that area.... The thin front collar is just glued to the CF tube, but it will be screwed to it after the final barrel assembly and all the glue dries.... All gluing is done with Loctite 638, and after it dries overnight, it will get a 3 hour post-cure in my wife's over at 175*F.... I'll have a photo of the assembled .257 cal barrel tomorrow....

Bob

Hobbyman2007:
Really looking forward to what you have in store for this one. I saw that condor for sale and almost hit the button. Glad you bought it before I did . :)

rsterne:
Well, now you know that your barrel will have a good home, Denis....  8)

Bob

Hobbyman2007:
Yep figured that was it. Really want to see what kind of power you’re going to get out of this one.

rsterne:
Initially I will be using the stock valve to give me a baseline.... Once I decided to go .257, I never even fired the gun with the .22 cal barrel....  ::) …. I am quite interested what the performance is with just the caliber change.... I want to experiment with the possibility of an SSG, or an SSS, to see if I can improve the bell-curve and efficiency, as from what I have read, those are the weak points of the Condor design....

I have a LOT of learning to do about the basic design.... I have read about "tank dumps", and other things which we simply don't tolerate on other PCPs, and I have looked at the valve design and have many unanswered questions.... The primary closing force in a conventional PCP valve is the stem area which penetrates the valve body, and hence has high pressure in the throat (while the valve is open) and atmospheric on the outside end.... If you have a 1/8" stem, at 3000 psi that is 37 lbs. of closing force, much more than that provided by the valve spring (typically 5-10 lbs.)…. In the Condor, the valve stem ends inside the sliding breech, which is at full pressure until the pellet exits the muzzle.... In some ways, I am surprised the design works at all  ??? ….

Bob

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