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PostPosted: Mon Jan 12, 2015 9:29 pm 
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Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
I posted a couple of pictures in the bullpup thread, but finally finished work on my QB57 so I'll post a proper thread for it. First off here's the ugly thing as it arrived, with lots of stuff on it I planned to get rid of long before I ordered the beast:

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So I heated the muzzle brake and stuck it in a vise and wiggled it off. Turns out the reduced section of the muzzle end of the barrel has 6 splines swaged into it like long shallow teeth, designed to keep this brake from coming loose or turning. Makes sense, if you like that sort of thing. The wooden thing on the barrel bugged me so off that came. Plastic grip and trigger guard gone. Rear cylinder plastic cap too. Butt plate gone. All I wanted was the main cylinder with guts, the barrel, and to re-work the stock. Started with the stock, carving away the awfulness and leaving something I could stand, adding a simple maple grip:

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I re-crowned the barrel and polished the breech end cone smooth, using my little TAIG lathe for these. Also turned down the barrel retaining flange (which was severely lop-sided - about twice as thick on one side as on the other) until it was actually round and concentric with the barrel. Brazed about a 4mm long piece stainless steel tube into the opening in the barrel retaining nut, building up bronze on the front side, as the hole for the barrel was a very loose fit. Opened out the stainless tube until the barrel could just get though without forcing it.

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The cocking lever jumped out about 3mm from the cylinder when captured by the little catch, a very sloppy fit, so I dismantled that, filed the surfaces to prepare for brazing and brazed the ends of the two stamped arms together then brazed a 3mm thick piece of steel onto the tip, filing it to fit once cooled. The lever now takes a bit of a nudge to get it to lock, and same with opening, just a bit of a squeeze against the cylinder to enable pressing the release catch.

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At the other end of the cocking lever I didn't like the sloppiness of the fit at all. A folded piece of steel with the two flanges not at all parallel to each other, some room for wiggling on the pin, and of course room for distortion in use over time. So I fitted a steel nut into the open space and brazed that into place. Used a sprung shim washer to take up the slack on the outside of the joint. Very acceptable snug fit now, just free to move.

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Inside I didn't do much to the trigger/sear, as it's a bit of a loose jumble of parts and frankly scares me a little. If it ever breaks I'll fix it, until then I'll just give it the odd drop of oil and try not to think about it. I did straighten the connecting rod a little and drilled out the pin hole for the safety (didn't want a safety, especially not such a badly made one) and put in a steel bolt to replace it. This was big enough that it stops the trigger from going nearly so far forward, shortening the initial easy stroke of the trigger dramatically. It's still a long trigger pull but much more comfortable, and the final effort is around 2 pounds or a bit less.

I used a bar clamp for a spring vise, undoing the two bolts on the rear steel cap and gradually releasing tension. Needn't have worried as the factory preload was only about 2 inches, very mellow. The insides were a bit dirty and there were a few burrs so I cleaned that stuff up and re-lubricated lightly with white lithium grease. Actually tried a moly paste first, but it slowed things down too much, dropping JSB Heavy pellets into the mid-400's. With a bare minimum of lithium grease it's around 500fps with the same pellets. From the factory (I bought this one from Scopes & Ammo) it was dieseling quite badly, averaging around 540fps and jumping as high as the mid-600's for a little while. :shock: That's when I decided to clean it out and re-lubricate, as I don't need nor want that sort of power, or NOISE, out of this little carbine. I turned the steel spring guide round and polished it - the swaged sheet steel guide was rather out of round and sharp edged. De-burred a lot of edges on the cylinder and cocking linkages and loading bay. Added about 14mm of shims to preload the mainspring, as there was a very brief but somewhat harsh twang in my ear, and after a couple of assemblies with different shims this seemed to minimize that noise. Still a harsh sound but no twang at all, just something more like a hammer blow on a heavy anvil resting in dirt. No ring, just whack!

I also made a brass trigger guard. Bedded the heavy steel rear cap and the front conical section of the receiver into the stock for about an inch each end with epoxy putty, leaving the cylinder itself free to vibrate as some experts advise. Wrapped the trigger linkage rod with a thin but stiff plastic sheet then soft foam before inserting it into the cut-out in the stock to help absorb some noise, as the thinned beech stock amplifies the piston noise considerably. I used a couple of rubbed-in coats of a linseed oil based varnish with a blue pigment powder mixed in. Absorbed quite differently into the maple grip, but I figure over time that'll darken with handling so I won't try to go further with colour there.

I made a PVC barrel shroud with a locating spacer at the muzzle to allow it to slip about 2cm fore-and-aft when assembling and dismantling the gun. I drilled and tapped through the 1.25" PVC for a 3/8" nylon bolt to capture it, as I didn't want the shroud falling off for transport and taking the muzzle spacer and barrel retaining nut with it. I reamed the rear of the PVC tube until it was a tight fit for the retaining nut, then epoxied that into place. Since Industry has used a twin-lead threading, the barrel nut actually spins on very fast. Oh, before any of this stuff I had to make a new indexing pin to fit the hole in the barrel, as I somehow dropped mine on my workshop floor on a day when I hadn't swept and never did get a proper look at that thing. The new one's a tight hammered fit, then filed until it just barely gets into the slot in the receiver. So the forestock (PVC shroud) is now an extended barrel nut. I just slip the rearmost 3" or barrel into the receiver, with the cocking lever loose so the breech seal isn't resisting the barrel, then spin the shroud into place and tighten it.

Lastly I made an aluminum block to fit onto the receiver and put my Fastfire III red dot sight at the right height for my eye. Fitted the top with 4 hardened pins to index the Burris sight and tapped for the 2 mounting bolts. Drilled through the block into the receiver for a countersunk stainless bolt in 10-32 thread. It's fairly high at 53mm from centre of bore to red dot, but nowhere near as high as the stock scope mount which when combined with the ~500fps velocity makes for some tricky trajectory guessing. 53mm I can cope with, largely thanks to Chairgun Pro and its zero optimization tool. From my initial indoor setup I'm seeing the potential for perhaps loonie sized groups at 20 metres (rested) so factoring in that size with Chairgun I can hold on zero anywhere from 8.4 to 24.3 metres and hit that sized circle. Of course I may re-learn how to shoot a spring-powered air rifle well like I did as a kid, but that'll take time. I'm ruined for springers really, love my PCP stuff too much... but I wanted to have a 'rifle' to go along with my several Webley spring pistols, sort of balancing out the independence from a pump side of the collection as a follow-up to my 2240 build - http://www.airgunforum.ca/forums/topic65612.html.

So here's the finished project. Shroud's painted to more or less match the stock.

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And here are my leftovers. Anyone want some unused QB57 parts?

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Seems the case is a bit bulky with the way I've got it set up now, so I'll be thinking of how to carry the thing. A violin case would work, with the QB assembled, but it breaks down so nicely. I must have something around here to stow it in... or maybe trade a few old fiddle cases for a small trumpet case?

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Finished specifications:

Overall length - 30" or 76cm
broken down - 19" or 48cm
weight - 6.28 pounds or 2.85kg

Shooter's impressions:

Using the cylinder to rest one's face isn't optimal. Hearing protection might be a good idea with this one. Holding it at arm's length and firing the noise is trivial, like any non-PAL springer, but the intensity when pressed close to the ear is bordering on painful. I was thinking of shrouding the cylinder with 1/4" thick neoprene foam. Still might do that. Or I could use leather. Might be easier to glue. I'll be keeping an eye out for a tidy solution to cover the spring and piston area, wrapping the cocking lever as well such that when closed the large void leaving the spring/piston area open to the world is closed. Neoprene or leather would both work if well fitted. Making this little thing quieter on my right ear would bump it up a big step in enjoyment. As it is the noise is too harsh sounding to shoot too many times in a row.

With the action bedded at the ends and using a reasonably heavy pellet the recoil isn't very significant. I find recoil more annoying with the slightly lighter Industry-branded wadcutter pellets supplied with it. Those actually seem quite well made, no visible seams and very even in appearance, with well formed skirts and heads. Maybe I can use the rest of those up in something else. I'll probably try some heavier JSB pellets through this some time. I get the impression something around 20 grains might be better with this length of barrel and power plant.

The synthetic seals on piston and breech are a somewhat hard urethane, perhaps in the 75 to 80 durometer range. Since I polished the breech taper on the barrel I probably won't see much degrading of the breech seal, but it's good to know there's a spares kit available for these and the mainspring from Scopes & Ammo. Archer sells sets of 6 of the breech seals but they're out of stock, and I've read somewhere that they're a bit weird about shipping to Canada, at least for some airgun parts. I get the impression overall that with a bit of oil now and then and maybe an overhaul every 10 tins of pellets this gun ought to last a very long time, provided the trigger holds up. I had considered making a new stock for it from scratch, but frankly the harshness of the firing cycle noise put me off so I used the existing wood, and now that's done I'm happy enough with the result to leave well enough alone. I'll get back to work on fiddles now...


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PostPosted: Tue Jan 13, 2015 8:33 am 
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Nice write-up. I keep coming back to these guns as an interesting project on the 'one-day' list. Detuned for a non-pal 177 it might be less harsh. Is the piston/sear engagement on the side of the piston or does it use a center rod? Side engagement is easier to make a delrin spring guide for.

Funny, I've never been a fan of blue/green wood stains, but that's an entirely personal thing. I guess you get to see so much of the classic red colours on all those instruments that you work on that the change is good :)

That factory fore arm is the weirdest thing isn't it?

Jim


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PostPosted: Tue Jan 13, 2015 4:14 pm 
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Location: Vancouver
There seems a bit of a consensus among Canadians posting online about the QB57 that its 'non-PAL' status is somewhat... flexible. As I said, mine was dieseling quite a bit as shipped, shooting about 10% above that line. Adding a couple of drops of a known oil in an attempt to smooth out the action a little just escalated this, quite dramatically, hence my tear-down and cleaning to get rid of all oil. I'm finding it's running at a stable, sensible velocity with just a thin white lithium grease. With JSB Heavy 15.89gr pellets there's a bit of dieseling, a small puff of smoke, which remains consistent using this lube. With too-light pellets such as those shipped with the airgun or with some RWS Super-H-Point 14.2gr pellets there's zero smoke, the slamming sound is harsher and the gun kicks a bit more. I just tried making a 'fake' 20gr pellet by gluing half an 8gr pellet into the back of a JSB Heavy. Almost exactly 20gr. Dropped the velocity about 50fps and the noise and bump went up just like with the too-light pellets. I'm thinkin' this gun likes the middleweights.

I just took the gun apart again and took out the spring preload spacers, putting about half as much spacing in the piston itself at the other end of the spring, adding about 25 grams there. Seems that's helped to flatten velocity variation a little and perhaps also helped take some of the edge off the noise. Perhaps less rebound, as if anything the noise seems more brief.

And yeah, I am rather sick of Chinese reds. Never was a fan of cheap Chinese lacquer furniture. That whole range of reds and red-browns cries out cheapness to me, especially the thick and glossy way it's usually applied. I just know that the slightest bump in the wrong place and a chunk of hard varnish, probably along with a bit of filler/plaster/cement, is going to come flying off. And yes, I've actually seen cement, complete with small gravel, used as a filler in parts of Chinese instruments. Especially fingerboards. Ruined about 1/8" of a nice plane blade on one of those chunks of gravel, had to spend over an hour re-grinding and honing it. Finished the job by chiselling out the cement which had been concealed under thick black lacquer and re-filled the void in the ebony fingerboard with wood dust and glue. Much easier to sand to shape that way. Anyway, yeah, I found the original finish and shaping of both the main stock and forearm grip just too ugly to tolerate for long. Not that I think I've accomplished something beautiful with what I've done! Far from it. There are some great stock carvers out there and I'm definitely not one of them. But it's lighter and less bulky and I happen to like the various marine blue-greens quite a lot.

As for your question, there is a square-ish slot in the piston for the sear to engage. It's already showing some slight wear at the rear edge, so something to watch. Might be necessary at some time to braze in some more steel to add thickness, give something deeper for the sear to engage. Keeping it greased with a dab of moly should help delay that. There are a few postings about various spring guide solutions. Some have made delrin guides, and that's something I'm considering. There's a Polish web store selling an aluminum guide which is very slim, in a kit which also includes a mainspring and a smaller spring with contrary winding direction fitting between that spring and the aluminum guide rod. Can't see how long it is, but probably full length. Obviously intended to boost power. Not sure I'd want that much stress on the piston sear cutout. Seems likely to cause excessive wear. Can't find the link at the moment, but here's what looks like an identical kit for the BSA Lightning for $49:
http://www.wolfairguns.com/product_info ... ucts_id=57


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PostPosted: Tue Jan 13, 2015 8:30 pm 
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Location: Komoka Ont.
Like what you did to the cocking arm lock and the hinge, I have noticed the wear at those points on mine. As well the slot in the piston where the sear engages. I made a delrin spring guide that was tighter and longer and I sleeved the piston with plastic from a bottle of contact lens cleaner, both these really helped smooth and quiet the cycle. My QB57 was the first air rifle I'd ever bought myself, I had a couple pistols but wanted a little better accuracy and power. I thought it wasn't as accurate as it should be so I cut and choked the barrel which seemed to help and later I shot another Qb57 and I think I made the right call that mine was in need of the work I'd done. Lots of fun to work on these rifles and those triggers are scary, I never touched mine and I added a drop of loctite to the adjusting screw because it seemed to be adjusting itself, I also put loctite on the set screw that secures the bear trap because it worked itself out once.

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PostPosted: Tue Jan 13, 2015 8:45 pm 
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Loc-tited that screw as well, when I pulled out the anti-beartrap lever to file all the edges round (except the little step that actually does the work) and polish it to a comfortable roundness. So many nasty sharp edges on these things! I came across a picture somewhere last month where a guy shows off the several stitches after his loading port slammed shut on his thumb. Think it was actually on the Archer Airguns blog. Archer himself spells out the way to avoid that quite nicely; always, always stick your right arm into the void between cocking arm and stock and support the gun with that hand, while loading with the left hand. That way the worst that can happen is you smash your right arm a little, maybe suffer a scrape and a bruise if the beartrap closes. But I suspect that it can only close if a) the trigger has gone out of adjustment badly or b) the lever hasn't been fully cocked. The latter I notice can be an issue, as there's first the click of the anti-beartrap lever dropping into place, then a very short distance further the sear locks into the piston. Got to go all the way!

Thanks for the sleeving tip, I'll have to give that a try. I'll grab the dimensions next time I'm in there and keep an eye out for something appropriate.

How do you choke a barrel? I'm not interested in shortening mine as the accuracy seems to be quite decent since doing the crown work. Pretty much shoots where I point it. But wow, seems it'd take the right shape of mandrels and a 10 tonne press or something like that, along with some skills relevant to doing it just right. Or is it simpler than that?


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PostPosted: Tue Jan 13, 2015 10:17 pm 
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Location: Calgary, Alberta
Cool build, but I'm wondering why you didn't make the fore stock a little longer...a little something extra to grab onto.

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PostPosted: Tue Jan 13, 2015 10:58 pm 
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funny guy... :D I just wanted to make it look sort of like this one:
Attachment:
QB57mod2a.jpg
QB57mod2a.jpg [ 129.03 KiB | Viewed 1996 times ]

Well, not really as it turned out. I don't really want a scope on this thing, the red dot is plenty accurate for its power level and resulting effective range for plinking. This one seems nice:
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Belgian_QB57.jpg
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... but in extending the stock for a proper forestock he's sacrificed take-down utility for transport. I'm not a driver, so stowing in a more compact case is important when I want to get out of the city for some shooting. As it turned out I ran out of patience building this thing. I'd intended to use a thin walled steel tube for the barrel shroud, but then had this little length of PVC sitting in a corner and decided what the heck, throw that on there and see how it looks. It's not exactly elegant, but it's a non-critical element of a not terribly 'important' airgun in my collection so what the heck. I gave a lot more focus to my 2240 build.

Funny thing about that one; I still haven't picked up a proper scope for the 2240 carbine, but today put on the amazingly cheap plastic scope which came in the QB57 kit and gave it a try.
Image
5 shots to sight it in, and hey now! Danged if the thing isn't half bad for accuracy! It's putting all the pellets in the same hole in my 7 metre indoor range. So I threw a bit of paint on it too. I may just leave it on for a bit, just for giggles. Then when I get some good glass for the Crosman I'll appreciate the lack of hazy plastic in my view.


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PostPosted: Tue Jan 13, 2015 11:35 pm 
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Just got in a quick bit of rested shooting with the QB and Fastfire, fine tuning the zero. Here's 5 shots braced on the bathroom door frame from 7 metres, with the JSB Heavy pellets this thing likes best so far.

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Not exactly world class shooting, but hey, for a casual lean against a doorframe and using a red dot it seems accurate enough to me for such a cheap (not counting my labour) airgun. I'm sure with some months of getting used to a springer I'll improve on that. Right now it seems to hit best for me with a semi-firm grip, not clutching too hard but not an 'artillery hold' either. More or less the same grip I use on my other two carbines, the Atomic and the 2240, both PCPs. Centre to centre for these 5 shots is about 10mm. I can close that up to 5mm or less with either of those other airguns at 10 metres, rested, but with the sloppy trigger and bang in my ear from this one it's surprising the group's not bigger. Mostly posting this as I don't see a lot of accuracy tests online for the QB57, at least not in English. There's a very long discussion on a Belgian site where a couple of guys show groups, and I think that's about it.


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PostPosted: Wed Jan 14, 2015 12:10 am 
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Here are 25 shots at 25yds free standing. with 4x32 scope and a little wind.
Image

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PostPosted: Wed Jan 14, 2015 1:19 am 
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Nice shooting! That looks just fine for un-rested and such a distance. Can't wait to get this thing out to the FT thing in Mission in a couple of weeks, along with a couple of other airguns.


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PostPosted: Wed Jan 14, 2015 7:00 am 
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I have a 57 donated to me by Wayne "watertown" because of the harshness on his cheek. I solved the problem with a green laser. Easily visible outside on a bright day, and very accurate. You can literally shoot from the hip with it.However its not even close to my go to gun. Theres just something about it that I need more than one finger to put on.

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PostPosted: Wed Jan 14, 2015 11:51 pm 
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Last evening I read myself to sleep chasing various search results relating to the comments in this thread about springers:
topic66162.html
The idea of chopping down the barrel appealed to me, considering (as Handyguy pointed out) the lengthy shroud and somewhat heavy nature of the QB57, and considering all the readings which seemed to point in the same direction. Namely that a springer often has a longer barrel than it really needs to have. So today I decided to chop mine. No big risk. It's just a cheap project airgun. So I cut off 6" of barrel and re-worked the shroud to fit the shorter barrel later, after re-crowning and doing a bunch of Chrony and accuracy testing. Here's a couple of pictures of the thing later in the day, when the paint was more or less dry.

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It feels much better balanced, significantly lighter at 5 pounds 15 ounces or 2.7kg. Accuracy seems not to have been changed. Zero needed slight adjustment on the Fastfire. Velocity dropped 30fps with JSB Heavy 15.89gr, but went up about 55fps with RWS Hobby 11.9gr. Both deliver about the same FPE, but the Hobby gives a much flatter trajectory at the higher velocity and my Chrony shows no more than 5 or 6fps total variation from shot to shot, compared to more than 10fps for the JSB Heavy, so it seems my QB57 has a new favourite pellet for plinking.


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PostPosted: Thu Jan 15, 2015 12:29 am 
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I prefer the look of this last change, looks to have better proportions.


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PostPosted: Sun Jan 18, 2015 5:27 pm 
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I've completed the neoprene covering of those parts of my QB57 which seemed most obviously emitting excessive noise. Used wetsuit contact cement and added a single layer to the cylinder behind the loading port and two layers to the cocking arm, the outer layer with extending flaps to press into the stock below and the neoprene above, closing in the whole area where there's line-of-sight to the spring and piston.

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And it worked. The sound is now easily tolerable for extended sessions, not intense at all, and reading about 4dB lower on my SPL meter besides. The meter's placement 1 metre to the right of the airgun isn't hugely important in terms of measuring noise from the spring and piston, as that noise is more of a close proximity sound, not something which propagates through a room so much. As my young boy put it the other day, the overall sound from his perspective was not like a gun shot at all, more like a metal thing hitting another metal thing. But a considerable amount of even that is gone when I now hold the thing at arm's length and fire, and the meter confirms that impression. As for the 'on the face' sound it's now somewhat remote in character. I lined the recess in the stock with bits of 1/8" neoprene on all sides leaving room for the trigger connecting rod, which considerably damped the hollow sound of the stock when tapped. The thin side walls I'd left when re-carving the thing were quite resonant.

I also used a tough and slippery satin-finish plastic from a 3-ring binder cover cut to size to wrap once around the mainspring, damping vibration considerably. It's not a snug fit but close enough. Cost me 15fps but not a big deal in exchange for noise damping, and shot-to-shot velocity changes only 1.3% from lowest to highest. Now I just hope to learn how to shoot this thing with some halfway decent consistency. I've got no springer skills these days.


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PostPosted: Sun Jan 18, 2015 6:03 pm 
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Ah, I was wondering how that would turn out. Glad to hear its a success, and has to be much more comfortable as well.


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