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PostPosted: Fri Apr 24, 2015 8:04 pm 
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Location: Vancouver
I'd done a bunch of modifications to my Industry Brand QB57 a while back, carving down the stock and adding an aluminum block to mount a red dot to the body, etc. Here's the thread about that stuff:
topic66172.html

Well in that configuration it still bothered me a bit, the powerful thunk of the piston slamming home right under my ear, even with the neoprene glued all over the thing. Bothered me enough to stew over how I could get that away from my ear, and also lower the Burris Fastfire III red dot which was really high above the bore and thereby a bit challenging for close range use. Finally I settled on ditching the stock altogether, chopping off the trigger block and connecting rod, and transplanting the trigger to the sear block. Making it a spring piston rifle instead of bullpup. And for a stock I decided to go with 1/4" steel rod running through a couple of 1/4" x 1" 6061 aluminum.

After pulling off the stuff I didn't want and filing down the spot welds on the cylinder, I bent some 3/4" x 1/8" 304 stainless bar stock into a long rectangle to surround the new trigger location. Then I bent another piece into a pistol grip mount bar and rear block mounting tab, drilling and tapping a hole into the rear steel plug from the back face. A second bolt goes through this same bar of stainless up into the already threaded lower rear plug retaining bolt. Two solid anchor points fairly well separated, so the grip frame would be stable. I brazed these two pieces of stainless together, cleaned up the corners, and attached it to the gun.

Then followed a bunch of ideas on how to mount a wire stock. I thought about swivelling a single larger element, but really wanted a sliding function, sort of like a MAT-49:
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or more like an M3:
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So I finally figured out how to use a couple of aluminum plates with holes through them for the rods, then a plastic block with a modified steel bolt, a taper carved on the lathe into the head end, such that it could be spring-released to de-tension a couple of 1/4" ball bearings and release the wire stock from the extended position. After getting everything functioning well I brazed the steel together permanently in the aluminum carriers, a rod in front and behind to give stability against twisting and a locked stop on the front to prevent it coming too far back. It's very solid and locks up so tight you can't budge it even whacking the butt hook on a table hard enough to dent the wood. Lots of metal carving later, here's the result:

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Knocks down pretty small, with my 10" chopped-down shrouded barrel. But I've just ordered a new barrel assembly from Eric at S&A so I can play around some more with barrel length. Probably end up with 12" or a bit longer, this time taking it slow and cutting off a chunk at a time and testing to see if I lose speed, then stop when velocity drops slightly and re-crowning. The shroud I've build from PVC pipe and delrin spacers is nice to hold the front end, provides a bit better stability than holding under the red dot, but it looks bulky. I may end up shrouding this new barrel as well, but it'd be much smaller tubing this time, more like 1" diameter or even perhaps 3/4". A bit less weight up front would be good with this somewhat heavy little rifle.


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PostPosted: Fri Apr 24, 2015 8:17 pm 
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I love it.....uniqueness is my weakness :D

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PostPosted: Fri Apr 24, 2015 8:35 pm 
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Unique is one way of putting it. Fugly might be more apt. My feelings about this airgun are mixed. It's a fun and easy platform for experimentation. I've seen some rather elegant versions of it done by folks in Belgium and Russia. But it's also an incredibly crude mechanism with some parts obviously doomed to fail or wear out in a short time and others very much over-built. I'll be trying to figure out how to reinforce the fast wearing cocking hole in the cylinder liner next as it is stretching and peening. No room inside to add metal, nor outside else it won't fit into the main cylinder. Hardening the steel seems the only possibility but who knows what sort of steel it is, if it can even take heat treatment? So much fun. Anyway... on balance I feel a bit hostile towards this airgun, and making it really echoes that.


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PostPosted: Fri Apr 24, 2015 8:52 pm 
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Wow. That would make a great entry for a "guess what this started as" competition. Doesn't that long bolt thingy in front of the trigger get in the way?


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PostPosted: Fri Apr 24, 2015 9:37 pm 
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the wire stock is much like my Bam B5-10... 8)

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PostPosted: Fri Apr 24, 2015 9:41 pm 
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Ace wrote:
the wire stock is much like my Bam B5-10... 8)

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I love those guns.....always wanted one for my collection

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PostPosted: Fri Apr 24, 2015 9:54 pm 
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notec wrote:
I love those guns.....always wanted one for my collection

that's to bad Jonathan...because TriggerHappy416 sold one that I did a grip mod for him in Feb of this year...you must have missed it.. :(

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PostPosted: Fri Apr 24, 2015 10:05 pm 
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Id have to live on my computer to catch all the deals.....lol

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PostPosted: Fri Apr 24, 2015 10:10 pm 
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true lol....

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PostPosted: Sat Apr 25, 2015 12:08 am 
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EverHopeful wrote:
Wow. That would make a great entry for a "guess what this started as" competition. Doesn't that long bolt thingy in front of the trigger get in the way?


Well considering that a few models of Industry Brand air rifles are made using the same power plant, yeah, it'd be challenging to figure out which one it was. I removed the trigger safety right away, the day it arrived. Can't stand safeties. The cocking safety finally went the other day when it failed on me, releasing the piston and cylinder liner hard and fast, bashing me in the side of the head with the barrel shroud. Could have been a lot worse than a bruised temple if I'd had my finger and thumb in there loading a pellet. The two-click setup with this model is scary and unreliable. Ditched it, so now it's either cocked or it isn't and I know from the single click of the sear engaging and from the way the lever doesn't try to pull forward when I start letting it go. Whoever designs these safety measures doesn't really have a clue about real-world use. So the absence of that lever would serve to confuse one a bit too.

The long bolt thingy is the bearing catch/release push rod, with a spring under the nylon washer. My finger squeaks in between the trigger and that easily enough, and the first 1/2" or so of the trigger pull is extremely light so I just start pulling it right away and there's no contact with the push rod. Put it as far forward as I could. If I'd actually drawn this up before cutting and bending and brazing steel I might have known to leave an extra half inch there, but so it goes when one designs on the fly the way I tend to do.

That BAM is decidedly cool. I didn't know about that pistol/carbine. Seems they're rare, huh? Oh well, maybe I'll stumble upon one some day.


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PostPosted: Mon Apr 27, 2015 3:44 pm 
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Another little update to the QB57 today; a new breech seal, as the original never looked great and with use was getting fairly messed up. An inferior grade of urethane I expect. Though I've got a QB57 repair kid (seals and spring and stuff) coming to me from Scopes & Ammo I had some 1" diameter 90 durometer red urethane in the lathe already, having turned some tiny seals for my pump in the morning. So I decided since that was centre bored already I might take advantage of the setup and make a couple of QB57 breech seals. Pulled the old one and measured it, then re-ground a countersink to match the angle of the conical barrel end and make this:

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It's a bit deeper than the original on the left and the conical bore is slightly tighter, making it slightly harder to close the breech but a great seal. Outside diameter is 13.5mm, depth 8.5mm, bore 5mm, and the angle on the reworked countersink is 74 degrees. Here it is installed:

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Sure is handy having a little TAIG lathe in the workshop. Have to make the cutter very sharp before attempting to carve urethane though as it wants to bend out of the way more than cut, and I used a moderately high speed of 2110RPM to prevent the cutter or countersink from digging in. Parted with a fresh razor blade turning the chuck by hand, as a parting tool tends to heat the urethane excessively and make a royal mess of the part.


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PostPosted: Mon Apr 27, 2015 3:54 pm 
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pretty nifty idea will done...
quick question isn't 90 durometer polyurethane a bit to hard as a breach seal though

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PostPosted: Mon Apr 27, 2015 4:29 pm 
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Two possible answers. No, it's fine for a comically tapered barrel end. Or... maybe I'm not remembering correctly and it's 85 durometer.


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PostPosted: Mon Apr 27, 2015 7:34 pm 
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I had to head out for the afternoon and now the forum won't let me edit that last post, so I'll add one more. I just dug around in my eBay purchase history and found that I ordered the red urethane rod in spring of 2013, and that it was in fact 95 durometer, not 90 nor 85. So fairly firm, but plenty of give for the tapered barrel end on the QB57, perhaps a bit hard for the Foster seal I posted about elsewhere but it works well.


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PostPosted: Fri May 08, 2015 2:59 am 
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Okay, two posts back I wrote 'comically' - thumb typing on my phone, dang it. That's supposed to be 'conically' as there's nothing funny about the back end of the QB57's barrel, I think. Anyway, the seal works just fine.

I got a 'repair and maintenance kit' from Eric at Scopes & Ammo the other day, along with a new .22" barrel for the QB57. Figuring the least I'd want to chop down the new barrel was about 1.8", enough to leave about 1/2" of the 1/2" stepped down diameter of the front end still intact for threading and mounting something to make it look more finished, I went ahead and chopped that 1.8" off and turned a nice new crown on the barrel. After running a few Hobby pellets over the Chrony F1 first of course, and shooting a few targets at 7 metres to see if the stock barrel offered anything tighter than the roughly 1/2" (rested) groups I was getting at that distance with the 10" barrel. Nope. The full-length barrel bumped up velocity about 2 to 3%. Cutting it down 1.8" and measuring again after finishing the new crown showed no drop in velocity, no rise either. So it could probably come down a bit more, but I actually like it this length as it's slightly quieter than the 10" barrel I'd been shooting with. No change in accuracy that I can see, still groups rather poorly owing to the over-sized bore and rather weak rifling grooves. So here's the progress to date, starting with the bits I made for mounting the wire stock around the new trigger position:

This shows the wide end of the tapered head I turned onto a bolt which acts as the bearing tensioning device, to lock 1/4" ball bearings into grooves carved into the 1/4" steel stock rod. The block it's fitted into is UHMW poly, fixed into place with a pin through the stainless steel frame and one of the bolts from the front attaching the aluminum wire stock guide to the frame. A push of the button and the stock can collapse easily.
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Yes, the wire stock is curved. I got the aluminum guide location a bit wrong on the back end, so wound up bending an arc into the steel rod to get it to sit right for my cheek to rest and line up my eye on the red dot.
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Here it is taken down...
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... and then barrel mounted...
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And with stock extended.
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Next up I'll order a 1/2" x 20tpi die to cut threads into the barrel end, as I think an air stripper I'd used on the Atomic might look good on there. Keep it lighter than it was with the huge plastic shroud, but make it look finished. If that doesn't quite suit me I'll make a skinny shroud for it, but I like how compact the thing gets for stuffing into the corner of a pack. Neat size for a hiking plinker. Almost needs a magazine grip up front though... but no, I probably won't go there. Did add a bolt coming in at an angle to adjust trigger pre-travel though. The wire stock release bolt did turn out to bother me too much so this throws the trigger back quite a bit without causing any trouble with sear engagement, and makes trigger travel much shorter before firing, while still acting as a trigger guard.


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