"Offtopic-posts-topic" NSFW

[jackssmirkingrevenge]

The water absorbs heat from the gasses and this and lowers the pressure, making less noise.

Looks something like this:



Not exactly useful for accuracy but I heard it's great if you're testing a mechanism for a rimfire.

edit: speaking of suppressors, here's a look at SilencerCo's "Maxim 9" integrally suppressed 9mm pistol prototype - look at that volume!

[Gippeto]

@Gippeto I have read about that. I currently own a QB78 and I'm not sure what to do with it, the block seemed like a simple way. What you mean by serious use? I mean I can modify the valve to use higher pressure but is the stock chamber any good? It's for co2 after all.
@Jack I suppose the water is to cool the gas? But wouldn't the water vapor add extra noise?

Qb78 is a fun little shooter once smoothed out. Good bang for the buck. Would convert it to pcp...some nice looking kits coming out of Europe if you don't want to do the engineering/work yourself.

http://qb78pcp-fac-tuning.com/

Tube on the QB's is an unknown quantity. Popular theory is that tube and securing arrangements for valve and tube end SHOULD be good to co2 pressure on a hot day (~1800psi). On the QB79 at least, this has not proven to be the case. Some folks using them with regulated hpa bottles @1400 psi are noting stretching of the screw holes in the tube. There have been a couple reports of the bottle block "departing".

Would consider it a 1000psi tube at best, but that's just my opinion.

Working on a QB-ish build actually.... 1"x.083 4130 tube, all custom internals. Mounted a .25 top end for testing...starting on the .30 top end today. Using a QB78 stock and trigger assembly, made/making the rest.





As assembled (not tuned) shot string (3000psi fill, .25 JSB Kings 25.4gr) started at 955fps, peaked at 1020fps and I stopped at shot 17 with 957fps...hammer bounce was getting bad at that point. 12 shots in the middle at 1000fps or more.

Would work on the tune if I wanted a .25, but consider it a good starting point for the .30 cal. Looking for 100-120fpe and 5-6 "good" shots when completed.

[wyz2285]

@Jack I thought about making a suppressor of that style if I end up with a pistol with rail ender barrel.
@Gippeto I got the deluxe version because I needed the open sights (they weren't straight had to correct the rare sight)
Recrowned the barrel but still 3/4 in grouping at 10m. I'm not sure how I'm going to proceed with it yet. Indeed good bang for the buck, full steel receiver etc compared to Crossman. I'm making a pcp atm as well with a piece of seamless ss tube I got, once I finish it I may consider change the barrel on the QB78 and pcp it.
Edit: Probably gonna just buy the pcp kit from that site depending on the postage cost.

[Gippeto]

Have a 78D as well..great when all you want to do is walk around the field ..tin of pellets and a few cartridges in the pocket....like being a kid again. Would suggest checking the breech end of the barrel for burrs....likely around the transfer port.

Pick of the current work in progress with .25 top end.

[wyz2285]

Have a 78D as well..great when all you want to do is walk around the field ..tin of pellets and a few cartridges in the pocket....like being a kid again. Would suggest checking the breech end of the barrel for burrs....likely around the transfer port.

Will do. Two questions: 1, on that site you have linked, does the PCP kit (cylinder only) work for .177? They are all listed for .22. If the only difference is higher fps for .177 I can down grade it easily, but will it fit on mine since the barrel support ring maybe different? Or .177 and .22 has the same OD?
2, what kind of accuracy I can expect after tuning the barrel and the rest? I'm not expecting it to do one hole grouping at 50m but I'm hoping it can match a low end Diana springer I have been using (1/2 in grouping at 10m free standing, the QB78 does 3/4 in at same distance)
It's hard to load with the stock bolt so I'm thinking of making a better bolt and re-do the breech.

[Gippeto]

In stock trim, the only difference between the two (.177 and .22) is the barrel and bolt. Everything "should" fit, but best to ask the manufacturer...have never used one of those kits and don't know anyone who has. LOOKS to be well thought out and made.

In any case...anything can be de-tuned by a fellow with machine tools. Easy to restrict the transfer port or make a smaller one. .070" is a good starting point for a modest power .177....one of my builds uses that...peaks at 725fps with 10.3 JSB on a 2000psi fill.

QB barrels are like Crosman barrels...some are very good, some are very bad...and most are in between somewhere. Most QB barrels I've had through my hands (mostly .22cal) would do ~3/4" @ 25 meters. The .177 barrel I had was pretty good...~1/2" @ 25 meters.

Push a few pellets through the barrel with a cleaning rod (barrel removed) checking for tight/loose spots and snags. Pay close attention to how it feels as the pellet travels the last 1" of the barrel and exits the crown. If it gets loose...might be worth while to shorten the barrel to a spot before it loosens up...or choke it.

[wyz2285]

Emailed the guy, didn't mention the fit or not question, but after some research it should fit. Even it doesn't, with the tools I have now I will make it fit.
Did some reading on barrel chocking. Most "homemade" versions are still out of my reach, so I had an idea of my own: Lathe the nozzle down to 0.5mm wall and press on a brass ring with a cone shape internal that would slightly squeeze the nozzle. I plan to try it on a Crosman barrel. Can't do it to the QB barrel because it's not even drilled in the center.

[Gippeto]

For choking a barrel, I have some dies made from 1" diameter stock. Dies are 1" in length IIRC and bored through to just fit the barrel. Then slit down the middle almost in two.

Place the die over the barrel such that the open end of the slit is at the muzzle end. Place in a 6" vise and give it a little squeeze. Rotate the barrel about 30 degrees and squeeze it again...repeat until you make it all the way back to the starting point. Push a pellet through the barrel to check.

Go slow, and stop when you feel the choke is formed.

[wyz2285]

That's one way I have read, problem is I'd need one hell of a vise to deform a 15mm OD .177 barrel...

[Gippeto]

Haven't done a qb .177 but have done a couple in .22. I have a 6" Record vise and use a two foot piece of pipe on the handle.

A larger arbor press or hydraulic press would make short work of it, buy you would lose the "feel" of how tight you're making it.

[wyz2285]

Heard about using hydraulic press on one of the forums I found while searching barrel chocking, where I also heard about vise breaking while use a pipe to extent the handle. Also heard about use a modified heavy duty pipe cutter, didn't see any example tho.
So typically a high end PCP barrel has chocking and springers don't (based on what I read on these forums) because PCP releases the air more "gently" while the springer fires a strong blast that forces the pellet skirt open against the rifling. I read that L&W barrel comes with chocking, so does it mean if I use a springer barrel on a PCP is a bad choice?

[jackssmirkingrevenge]

Diminutive lady firing the Mauser T-Gewehr. It looks like she came a little.

[wyz2285]

Spent the last few days restoring my first bicycle my parents bought me. Almost done and rest of the parts I need will be delivered tomorrow. All the upgrades are a bit overkill for a steel frame but the initial idea was to keep the bike running for sentimental values.
Had to machine some spacers to install the front suspension and rear disc brake because the original frame does not accept standard mountain bike suspension and disc brakes.

[mobile chernobyl]

Nice work!

Got a close up of that rear disc mount? And I'm guessing you had to get a disc compatible rear wheel (hub)?

I always wanted to build a cool steel framed city beater bike - they're pretty common now but weren't always haha.

[wyz2285]

Got a new pair of wheels, the old ones are bent and since I need disc compatible wheels I just got them all together.
Got lucky with the rear, I thought I would need machine a entire structure but instead I only needed to machine a bar.
The steel frame is a bit heavy for long rides or climbing but a side from that nothing wrong with it.