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Quackenbush 9mm Pistol velocity report and zeroing issues

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G

Gsyme

Member
Jan 7, 2021
38
17
WA, United States
I've got some velocities to share.

No pics yet because I can't seem to get the photos off this flip phone at the moment.

But you know what it looks like:

https://duckduckgo.com/?q=quackenbush+outlaw+pistol&t=brave&iax=images&ia=images&pn=3 

I've got the Crosman shoulder stock on mine. 14 inch barrel.

It's fun and loud - takes a lot of pumping. About 108 pumps to get to 3000psi. 3 or 4 useable shots. 

81.2 gr JSB Exact .35 cal diablo pellets

01 - 782 fps, 110 fpe

02 - 731

03 - 671

04 - 604



118 gr. round nose Air Venturi Slugs

05 - 702 fps, 129 fpe

06 - 657

07 - 596



127 gr flat nose Air Venturi slugs

08 - 676 fps, 129 fpe

09 - 629

10 - 580

...

Having a heck of a time getting it sighted in. I pumped it to 3400-3600psi a few times because I had seen folks on Youtube go that high but then I kept finding loose screws. The piece that holds the barrel and reservoir together, near the muzzle, came completely loose at one point. After that, I noticed other loose fasteners. So I've only been going to 3000 which is the official pressure.

I've been using loctite and trying to get everything snug, one bit at a time. Every time I think I have it all tight and zeroed in, the next time I get the gun out it has not held zero. I have a SeeAll sight on it. Any tips on this or your favorite zeroing techniques are certainly welcome. I've read a few articles but this one is certainly a challenge.

Part of my problem may be that the velocity changes so much from one shot to the next - but still, seems it should be shooting fairly flat at 25 yards. The gun also has a fair amount of kick. Thinking about rigging up some sort of vise next time I have a zeroing session. But I'm getting tired of sighting it in all the time (it's exhausting, all that pumping). 


 
You need a guppy tank and a friend with a compressor! I tether off an old paintball tank
image.1613669986.jpg

 
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Quackenbushes are set up to achieve maximum power, hence way oversprung (hammer-springs) for consistency. In tuning my .50 Outlaw pistol I ended up cutting over 1.5" length off the hammer-spring in order to get a consistent powerband. Thusly "tuned", you might get 3-4 CONSISTENT shots per charge.

In my opinion you should remove the barrel-band, and get a tank to charge the gun. Pistols are plenty challenging enough without having to pump the thing up to get a few shots at diminishing returns. 

download.png
View attachment DAQ 50 pdf.1613671021.pdf


 
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I like the tank idea. I suppose that even if I have to charge the tank by hand, I can do that in my office a little each day, then when I got out shooting I can just focus on shooting. 

So, remove the barrel band? So that piece is unnecessary? I like that idea too. The barrel can just free float at the muzzle end? I never even considered that. I have been suspecting that when I tightened that band down I didn't get it perfectly straight and the barrel might have a slight bend to it. I much appreciate the feedback. Thank you.

- G
 
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In my opinion barrel bands are a horrible idea on PCPs, and can't believe they still exist.
Click to expand...

I'll second that. Attach the barrel to a pressure vessel that expands, moves, and shrinks depending on PSI.

Also what was stated about the gun being set up for max power is true. The valve basically dumps air. It is not set up to be balanced or efficient. Only powerful.
 
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I just looked at that pdf on your .50 Bandit, AirNGasman. Very impressive. Getting 10 shots into a 2.5" circle from 50 yards with this pistol of mine is pure fantasy for at the moment. I'll be happy if I can get it hitting beer cans from 25 yards consistently.

I am anxious to try these ideas. Very curious to see if sighting in will be smoother without the barrel band. Also, curious to see if it will hold zero better. I'll try that idea first. I've never trimmed a hammer spring before. I suppose I should cut off in small increments and test as I go so as not to cut too much?

Thanks again, all.

- G


 
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"I suppose I should cut off in small increments and test as I go so as not to cut too much?" 

Correct; it's definitely a trial-and-error process, with emphasis on erring on not cutting too much. Of course you chronograph between each cut of the HS, charging as high as 3400 PSI to ascertain when you're approaching valve lock. If you're not familiar with valve-lock, call me at 254-253-1239. and/or read this-

download.png
View attachment PCP Co2 excerpts.1613702781.pdf


 
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I can definitely attest to the challenges presented by a higher power hand cannon tuned for a descending string... Great advice has already been given, I can just reiterate by sharing my experience with a similar, yet more tippy version of your pistol that I made from a Gen 1 Mrod.

I would recommend taking one of these approaches. 1) tether to a larger tank (ideally a tank regulated at 2500-2800psi) and sight it in. or 2) Tune for a bell curve prior to attempting to shoot targets and sight in.

It is very difficult to manage the muzzle blast and descending velocity of the high power, descending velocity tune. it makes interpreting results and sighting in virtually impossible.

In the end you will really enjoy this gun. There aren't many things as satisfying as smacking a 4" gong at 75 yards with a .357 pellet shot from a pistol.
 
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Ok. I am encouraged and have my work cut out. I removed the barrel band as suggested and I am going to look for a larger tank before attempting the more involved hammer spring adjustments, though, it seems that is something I will want to do in the long run either way. After a cursory look at the gun I don't actually see an easy way to remove the hammer spring. Looks like I may have to remove the breech or trigger assembly in order to get to the fasteners?

I like your article in the PDF Airngasman, especially the comment about "heapin' helpins of patience" being necessary. That is certainly proving true here - though it seems true in every sport or discipline, really.

Mackeral5 - thanks for that encouragement at the end especially. I already have felt some satisfaction simply from being able to wow a couple of non-airgun friends by putting a .357 hole through a 2x6 with my "airpistol". Looking forward to being able to smack anything at 75 yards. The fist shot I took with the pistol definitely made me say, "wow!" Still surprising how many people have no idea that airguns exist which can do that at all.

- G
 
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I have a short progress report. First, I removed the barrel band as suggested by airngasman and long gun dalla. I then pumped up to 3400 and chronied. Definitely no valve lock yet. First shot 819 fps, second 784. I want to try trimming the hammer spring but I may try to find a replacement spring just in case before I begin that process.

I have not acquired an external tank yet - but I took Mackerall suggestion and tried sighting in at a constant 2800 psi for each shot (this meant 30 pumps between every shot - not terrible...I actually liked the rhythm better than pumping 120 times every four shots.)

This, combined with the removal of the barrel band seemed to work wonders. I was actually able to sight-in. The three shots on top were consecutive shots from 25 yards after finishing the sight-in. Won't win competitions but I had started to wonder if this gun even could be accurate so I was very happy. The tips worked! 
IMG_0231.1614621084.jpg
 

After that I had some fun and set up a beer can and the 2" center of a clay at 35 yards. Nailed both on first shots. Last time I went out I couldn't get this gun to hit anything at any distance. 
IMG_0233.1614621274.jpg






The question now is whether it will hold zero. I am going to go out again in a week. - G
 
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