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PostPosted: Mon Jun 11, 2018 8:28 pm 
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Location: Coalmont BC
I think you would have been better off to leave your setpoint alone, and just reduce the hammer strike to bring the velocity down to about 700 fps.... that is what I meant.... You would have a higher shot count and better efficiency (and quieter) than you will get by lowering the pressure to 1100....

Bob

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PostPosted: Mon Jun 11, 2018 10:58 pm 
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Location: Caronport, Saskatchewan
Looking forward to some pictures! if efficiency isn't great Bob's suggestion probably is the ticket. Nice you are getting a really flat string now though.

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PostPosted: Fri Jun 15, 2018 11:34 am 
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I’m getting to know the airgun pretty well.

Rather than constantly tear-down and rebuild, I’m going to try to leave the hammer spring alone and tune via the regulator. At 1400, it shoots just over 700, and sounds really snappy. Unfortunately, I can’t get my current regulator stack to play nicely that high.

It’s currently around 1300 psi shooting 18’s at 730fps for 90 shots on reg. It’s still got too much hammer spring, but the efficiency numbers aren’t bad. I’d like to up my regulator pressure to 1400, seems easier to buy one that’s factory set than fiddle with Belleville washers again.

If anyone’s got suggestions for online regulators, or the correct Belleville washer size that ships to Canada, I’d appreciate it.


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PostPosted: Fri Jun 15, 2018 6:55 pm 
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Not much to look at, but I put it together with vice grips and a (now fried) Dremel tool.

Now living at the cottage for pinecone duty. Clover-leafs at 30 yards. About 100 shots @21fpe

I'd still like to up the regulator when I have a chance, if only to quiet it down. Also looking for a better scope, something 12-16x with at least ten mildots of holdover. Love this leapers 3-9x40, but 9x isn't enough.

Everything is really sturdy, theres a small strip of rubber between the bottle and rail mount. It even balances ok at the hand rest position, a bigger scope will help.

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PostPosted: Fri Jun 15, 2018 9:44 pm 
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Location: Caronport, Saskatchewan
Thanks for sharing, Looks good!
I couldn't read the efficiency page on my phone, I'll have to take a look on the computer to see if it's less blurry. Nice work

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PostPosted: Sat Jun 16, 2018 6:00 am 
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Efficiency of 1.34 at a very consistent 730fps with JSB 18’s.

Velocity peaks around 1350psi (750ish), then down to 700fps by 1450psi. So I should get significantly better efficiency (and sound level) with a bit higher pressure (currently 1300).

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PostPosted: Sat Jun 16, 2018 8:33 am 
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Location: Caronport, Saskatchewan
Nice! As you say if you can get the pressure up and have it stable there it should increase efficiency and shot count quite a bit.
Just a thought on your fill pressure at start. Did you fill your tank while it was attached to the gun with the Asa valve open so the air tube was filled with regulated air when you read the tank starting pressure? This would make your efficiency what you've recorded. But if for some reason you filled the tank recorded your start pressure then opened the Asa to allow air into the gun this would mean the actual efficiency was higher than what Sikes calculator recorded. Probably a dumb question. On a side note, if it was unregulated then you'd count the tube volume of the gun and hose in your formula which would be another 55cc or so maybe, but since that's regulated air you don't count it, so that's correct what you've put in the formula. I'm pretty bad at math so this is probably obvious to you and everyone else, but in case there is someone reading later that has similar struggles like myself, hopefully it might help to think about why you need to record only the cc's of the tank, and have the gun tube reservoir filled at stop and start when recording your fill pressure.
Good work on your gun! You should have well over 100 shots once you get your pressure optimal.

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PostPosted: Sun Jul 01, 2018 9:03 am 
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Added an Aztec Emerald 5.5-25x50 (airgunsource.ca). A lot of scope for a homemade budget gun but it's a lot of fun to shoot long range.

Set a 6" gong out as fas as I could at the cottage, 177 yards according to google satellite. When the wind died down, and with 11.5' of holdover it hit over 50% of the time.

Unfortunately it's still too loud. To up the pressure, I went ahead and ordered a new tank and regulator from AliExpress. 4500psi bottle, 1500psi set regulator, and a 3 pack of 1.8k bust disks. I don't think I'll hand-pump to 4500 very often, but it's nice knowing I can extend my shot-count if I want to. If my math and guesswork is right I should get about 200 regulated shots at 20fpe.

Glad there's so much info out there (thanks Bob!), this has turned into a fun bench gun.


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PostPosted: Mon Jul 09, 2018 7:52 am 
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Location: USA, New Jersey
Good job that's sure a lot better than you started with

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PostPosted: Wed Jul 18, 2018 10:04 pm 
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New bottle and regulator showed up from AliExpress.

200cc, 4500 psi bottle with a regulator apparently set at 1500. I haven’t checked the output yet, I’m waiting on a fill adaptor with a gauge to show up. I removed the 3k burst disk and replaced it with a 1.8k disk. Pumped it up to 4000 psi and started shooting!

First off, my 3 stage FX hand pump had no problem with the higher fill pressure. I only stopped at 4000 psi because it started making me nervous...

Looks like the reg is set right where it’s suppose to be (1500?). Shot cycle is nice and crisp, just taking small sips of air. JSB 18’s are shooting 710fps, perfect for plinking.

Efficiency is at 1.6 now, giving me around 200 shots at 20fpe. Shot to shot consistency is bang-on. The pressure does change slightly from full to set point. At 4000 psi it shoots 700fps, at 2000 psi I’m getting around 720. Close enough not to be an issue.


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PostPosted: Wed Jul 18, 2018 10:10 pm 
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Location: Caronport, Saskatchewan
Great work! Wow that's nice having the carbon fibre bottle, probably nice and light too.

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PostPosted: Wed Jul 18, 2018 10:33 pm 
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It’s actually an aluminum bottle, so it’s a little heavier. Worth it in my case for the shotcount.


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PostPosted: Thu Jul 19, 2018 12:11 am 
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Great efficiency anyway, and as you say, you've got a pile of shots!

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PostPosted: Mon Jul 23, 2018 7:49 pm 
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I knew that I was too light on the hammer spring for the 1500psi set point, I loved the efficiency, but wanted to tighten up my extreme spread.

I don't have an RVA, and only one (clipped) spring, so finding my new plateau at 1500psi was more theory than practice. At around 1350psi, my max fps with 18 grains was 780. So I figure my new plateau at 1500psi should be around 820fps.

I shimmed my clipped spring and managed to hit 775fps on the first try. As far as I can tell it's about perfectly balanced. My regulator creeps to about 1550psi, however it doesn't seem to affect velocity. Similarly, I don't drop below 770fps until 1350 psi.

Shooting from 4300psi - 1350psi, I get approximately 150 shots between 780-770fps, literally zero shots outside a 2% spread.

150 shots at 24fpe makes for a fun plinker. It's been too windy to shoot any groups at a distance, but pinecones at 70 yards are a breeze, even in the wind.

The new bottle and plumbing are all attached and the ergonomics of the rifle are great. It balances perfectly at the grip behind the bottle. Pics to follow.


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PostPosted: Tue Jul 24, 2018 12:27 pm 
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