Hi all, new guy here. I'm a licensed gunsmith that got hooked on the world of PCP rifles a few months ago. I purchased an Air Venturi Avenger and Umarex Hammer. I quickly became addicted to the big bores. I wanted to try something new and thought I'd have my hand at building my own big bore 50 cal. I wanted to achieve 1150fps with 250 hard casts that a friend made. I started out with raw material, a 500/510 green mountain barrel blank, tank and reg. There's a bit too much to go into but I can fill it to 4500 psi and fire it unregulated which will dump the total air volume or pump it to 4500 with the reg and fire shots at 3000psi. I designed all the parts in my head and just made corrections as I went but putting it on the chronograph surprised the hell out of me the first time I shot it! This was unregulated at 2500psi. I'm trying to decide on whether or not I want to get into maybe producing these at a later date, obviously something better looking than this iteration. It weighs 8lbs without the scope but I plan to put a carbon fiber bottle on it. I currently have it regulated at 3000 with a 4500 max fill and get almost 5 full power shots at just shy of 1200fps with the current plenum volume.
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Homemade bigbore 50.
- Thread starter TheBeardedGunsmith
- Start date
Yeah its temporary until I can come up with something better.I like that High Tech screw clamp!
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That's alot of power! It looks like it may explode at some point but all in the name of science!
A refined model may be a hot seller though.
A refined model may be a hot seller though.
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Hey. I live in Ohio north of you. May have to see about a visit to see that Beast!
I have an Evanix Sniper in .50 myself.
I have an Evanix Sniper in .50 myself.
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I hope not. I used the appropriate materials and oversized the wall thickness of everything pressure bearing. I was sure to research everything that I could.
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Well like they say, looks can be deceiving. I'm sure you're okay, it just looks sketchy in its current setup. I do like that you used a crosman 2240 as a starting point for your hammer tube and trigger frame.
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Yeah its definitely a proof of concept platform more than anything. The clamp is really the only thing mechanically hokey. It's difficult to build pretty guns.
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Wow you are quite the machinest!!!! Looks great!!! Did you get the 34 inch cut rifles blank from green Mountain? That's the fastest fps I ever saw a big bore go. I have lots of molds in .510... With that kind of power I'd be using the 650 grain spire point boat tail I have from accurate molds. It will stabilize in your barrel. The B.C is . 5. My 50 Texan shoots them at 750 fps. Also at those speeds you really want powder coated slugs. They really reduce leading and work at faster fps. At a 1000 fps with the 650 spire PT boat tails you have 1000 foot pounds at 300 yards. Not too shabby for a air gun. Don't let anyone discourage you...I also used to be a hobby gunsmith have a jet 13x40 lathe and used to work at ER Shaw barrel factory in bridgeville. Hand lapping really helps with big bores. I know green Mountain barrels are decent but not lapped. If you want any slugs PM me. Wow you made my day
You the man!!!!!!
You the man!!!!!!Upvote 0
Thank you. Its a 27" 1:28 twist stainless GM barrel blank. So far I'm not getting any leading in the rifling. I should also state that im a licensed gunsmith that's still pretty new to airguns. Regular firearms are what I do for a living. This has been a side project over the past month or so.
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Most guys “build” custom guns based on the 2240. It’s more like they’re putting Lego’s together. You ACTUALLY built a custom gun from a 2240, very cool regardless of the lacking refinement. What kind of valve did you make for it?
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Can't wait to see how many of the 'Big Guys' start knocking on your door!
Keep your secrets to yourself untill you get a gob of cash!
Keep your secrets to yourself untill you get a gob of cash!
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It's a balance valve that I designed to not be able to suffer from valve lock. It will push open easily with finger pressure regardless of air pressure. I ended up using teflon orings in it which weren't cheap or easy to install. I machined everything from scratch, minus the grip assembly. It's actually from a Crosman 1322.
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Admittedly I've been spamming facebook groups with this but mostly because I'm proud of it for a first time build. I designed it in my head, often staring at the ceiling at night due to insomnia. If I design something on paper it never works so I just have to build it in my head and then do it.
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Good move going with the balanced valve for a big bore to avoid needing a heavy hammer spring. Did you get inspired by the Umarex Hammer’s valve design?
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I couldn't find any info on the valve design of my hammer and didn't have the nerve to open up my brand new gun. I just did as much research as I could online of air valves that can dump large volumes of air quickly. The first valve that I designed wasn't a balance valve. It worked well but required way too much force to open it, and that's when I learned about the balance valves. It was the most difficult part to machine of everything.
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