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All Springer/NP/PCP Air Gun Discussion General > Show Off Your Air Guns With Mods (SHOW and TELL)

Cheap, beatup, sad, forlorn B2+ too much time = sniper rifle?

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Paul68:
Earlier I posted in the general AG gate about a B2 I needed identified, and the knowledgeable folks here were stumped for all of about .3 milliseconds. Well, this poor little spitter is getting a second chance at life.

I'm giving this thing the works. "dang" the torpedos, wing and a prayer, if it looks like a good idea do it, and all that. Since its value is about zilch, and just about anything will be an improvement, let's see what happens eh?

I've already done quite a bit, but as the pictures show, this is only the beginning.

I've honed and yes, POLISHED, the compression tube. While I fully understand the idea behind crosshatching, having over twenty years of experience in automotive rebuilding and restoration (Mopar nut whose vehicles have placed well in competition), I also understand the pluses and minus's of machining and how certain parts, materials, metals and chemicals react with one another. I feel that crosshatching is indeed a good practice, but that it is not taken far enough, and the process is not actually completed when it comes to tuning AG's. While most metal to metal crosshatching applications take into account the different properties of the metals comprising the cylinder and seal, and thus are intended to produce a "wear to fit" seal between metal seals and metal cylinders, the extreme differences in properties between the metal cylinders and synthetic seals in AG's demands a little more attention to finish.

I feel that in order for crosshatching to produce the intended result in AG's, ie, hold lubricant, the grooves do need to be substantial in relative terms, but I also know what happens when you take a synthetic rubber and rub it tightly against what amounts to a very fine file. That metal aint going to wear very much very quickly, and that synthetic is going to take a beating in comparison. In other words, I think the usual crosshatching procedure used in AG's is far less effective than it could be, and taking a lot of life out of seals and reducing potential power despite obvious gains.

To that end, I crosshatched the cylinder, then used a dowel with 800 grit sandpaper folder over enough times to produce a strong interference fit in the cylinder to smooth the crosshatching. The 800 grit is not enough to remove the cuts produced by crosshatching, but IS enough to smooth the edges while leaving the grooves, thus providing a smooth surface for the seal that wont' reduce the life of the seal prematurely or require an extended break in period.

Ahem, now then onwards and upwards, we hope.

Aside from the obvious outlined in the pics, I have even more changes in store. While I have figured out how to convert to a synthetic seal, and in the process gain a significant bit of swept volume, I can't reconcile what I see as a very inefficient piston design. It's heavy, has a lot of contacts points which in turn means increased friction and thus inefficiency, and is just all around poorly manufactured. I mean c'mon, I know it's a cheap rifle, but is sheet steel rolled into a tube really cheaper? To that end, I am considering just building a whole new piston that will have half the weight and half the friction points. We'll see how froggy I get about that one.

I have found some interesting sources for seals, http://www.theoringstore.com/index.php?main_page=index&cPath=172 and am looking at a teflon cup that will further reduce seal thickness and thus further increase stroke, and thus (whew) increase swept volume. All without making a new piston. Just getting rid of the leather seal and replacing with a synthetic gains almost half an inch, and for those of you thinking the cocking linkage will be a problem, you'd normally be right. However, this particular sad little B2 has a ton of slop in the linkage and has to travel over 1/2" before it even engages the piston slot, with a matching 1/2" at the compression area. In other words, the piston can move back almost a full 1/2" before being exposed to the slot. I can take it right to the limit, and maybe not have much room for breaking the barrel loose, but since it's such a light gun and will not require a lot of cocking force, it should not be a problem.

Getting long winded here, so I'll wrap up.

The stock will be lengthened, trigger guard customized with aluminum and flush fitted, a rubber butt pad added after lengthening, finished in a thick satin black coat after being heavily modded, and I'll use rubberized undercoat to produce a striped grip pattern on contact areas. This gun will be scoped obviously, hopefully produce high 600's if not 700 fps, and look like an evil little pellet flinger to boot.

Either that or it will end up part of a new pickup bumper once crushed and melted down at the junkyard for scrap;)
 

supertech77:
you got some good idea's keep us posted with the out come;; ;D

Paul68:
Thanks. We'll see if they'e good or just half baked eh?

Guy down the road from me here runs a machine shop. Brought a couple things to him to look over, and I think I've found my go to for parts that have to be precision made to be safe. I'll be bringing some trigger diagrams for this B2 to him and see how he does.

Paul68:
Been busy with my Storm, so the B2 has been neglected. Went out this morning and fabbed a seal until a decent one arrives in the mail. Posted this in the general forum, figured it belongs here really.

The leather seal is junk, so I made one out of garage stuff. Found a polyurethane sway bar bushing kit I had left over from a front end rebuild. These bushings are cylindrical and have a perfect diam hole through the center. I simply cut it down to a flat washer shape and sanded it flat, chucked it in a drill and ground the edge down to a slight angle and sized it to the breech, then lightly smoothed it with 800 grit. To get the "parachute" shape, I just found a socket of a diameter that would give the lip I wanted, heated it up with a torch, and pressed it in for a second. Then I just cleaned up the melted channel with a round dremel bit. Not precise machining, but it fits the chamber well and these particular polyurethane bushings are supposed to be self lubricating although they are probably too soft to expect anything more than maybe a thousand shots if that. To fit it to the piston I just used a new countersink bolt, the original seal washers, and a few small washers for spacers that fit inside the new seal to keep from overloading the seal and expanding it. The best part is that this homemade seal is 1/4 inch shorter than the original leather seal assembly, giving a slight increase in stroke and volume. By no means a professional job, but fun and cheap all the same. The seal is shiny because I have it soaking in Teflon lube to give it some time to absorb and maybe increase its longevity. It'll be wiped clean at assembly.

Paul68:
Did a little more this afternoon.

Cut a strip of aluminum and bent it to shape using the workbench and clamps. Shaped the ends, sanded for what seemed like forerver, and put an inital polish on it. Voila, trigger gaurd takes shape. Still needs a final polish and mounting holes drilled. The mounting area on the stock will be recut and recessed in the rear so the whole gaurd sits in flush. First two pics are after rough cut and shaping. Last two are before final polish.

I've also included a pic of the stock which has been sitting for awhile in this configuration. Filled in the side grooves with wood putty, filled in all the gouges and nicks, ground down a huge hump along the top edge where the receiver rests, taped out the areas that make hand contact and sprayed em with three coats of rubberized undercoat, then put a coat of flat black enamel over it. I'm doing away with the gray pinstriping and going to give it a final coat of flat black. The whole thing will get sealed with semi-satin clearcoat. I have also cut out and formed a stock extension which will add 4 inches to the butt and which will be attached with two bolts fed through 1/2" aluminum pipe.

Gun is pretty much ready to assemble, just have to fab a couple small pieces.

 

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