.25 CO2 beast
Printed From: Kiwi Airgunners
Category: Technical
Forum Name: Pauly's Technical Area
Forum Description: Technical information, Modifications and DIY projects are all in here
URL: www.kiwiairgunners.co.nz/forum_posts.asp?TID=1341
Printed Date: 09 Jun 2026 at 4:06am
Software Version: Web Wiz Forums 10.14 - http://www.webwizforums.com
Topic: .25 CO2 beast
Posted By: nunga
Subject: .25 CO2 beast
Date Posted: 20 Apr 2026 at 6:35pm
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Just want to say a big thanks to http://kiwiairgunners.co.nz/member_profile.asp?PF=622" rel="nofollow - jwabfrog for sending me the .25 barrel. I will be starting my new project over the weekend. This will be a 30PFE .25 CO2 bolt action rifle Powered by a standard Sodastream 60L bottle. This will take a while as everything will be made by me (apart form the barrel) I have been planing and researching this for the last year and i am finally ready to start. So watch this space! ------------- 2nd place HP springer - WFTF World Championships 2014 |
Replies:
Posted By: -Ec
Date Posted: 20 Apr 2026 at 7:43pm
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30FPE - that'll hit HARD. Any guestimate on how many shots you might get from a soda stream bottle? Going to take some careful engineering to put it together. Looking forward to seeing this project unfold. Good luck with it all. ------------- Regards, -Ec |
Posted By: nunga
Date Posted: 17 May 2026 at 7:39pm
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So ive been super busy lately but i managed to get into the garage today to make a start on this project. I have done the research but now i will test this research to make sue i am on the right track before i even start making the parts for the gun. So i am making an adapter to screw onto the end of the Sodastream bottle. It will have a thread on both ends. One to fit the Sodastream bottle and the other to have a threaded rod that will screw into the valve of the bottle to open it. Then i will tap a thread in the side to install a pressure gauge to make sure the bottle will give me the 800PSI needed for these calculations to get the 30PFE target output.   I will drill and tap the rest tomorrow with a bit of luck and test.
------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: Ashman
Date Posted: 17 May 2026 at 10:16pm
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Holy sh*te there's mad ass engineers on here. When you've finished that, any chance of building me a time machine? Just a basic one. Nothing fancy. Will need a dunny though.
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Posted By: nunga
Date Posted: 17 May 2026 at 10:42pm
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Ha ha, sure thing! ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: nunga
Date Posted: 23 May 2026 at 3:27pm
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So just a quick update. I have made everything and test fitted to make sure all the orings seal and so forth. Went to the shop and swapped the empty bottle that i used as a template to cut the threads in my adapter, Screwed the new full bottle in and the threads bound up halfway screwing it on. I have 3 bottles here as i have a sodestream machine here to make my cola for my whiskey I make. All 3 bottles have slightly different threads by the looks. one screws in just fine, the other is a little tight and the last one only gets half way. This is going to be a problem. Their quality control on their bottles is not the best. Probably because its designed to screw onto a lose fitting plastic nut in the machine with very back low pressure. I need my threads perfect if they are going to hold the full pressure of the CO2. So i will have a little think about who to safely overcome this problem. ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: kruzaroad
Date Posted: 23 May 2026 at 8:27pm
| Could you make a new adaptor that takes a sleeve you can screw in and out and have slightly differnt threads for the bottles. Can you make a adaptor for filling the bottle and get co2 in a bulk bottle and fill the canastas that work yourself? |
Posted By: nunga
Date Posted: 23 May 2026 at 9:04pm
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I do not have the technology to full the bottles myself as they are liquid CO2 when full. I would need some way of freezing the gas then full the bottles in liquid state. (i think) Making a sleeve might work but then the wall thickness of the adapter will need to be bigger to take the different inserts. this might not be practical. ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: kruzaroad
Date Posted: 23 May 2026 at 9:31pm
| Other option might be to get a die and just tidy up threads on the bottles that don't fit when you get them. Assuming they must be pretty close. Would still work in a soda stream when connected and wouldn't be noticed when swapping bottles |
Posted By: nunga
Date Posted: 23 May 2026 at 9:58pm
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Yeah thats probably the best option. For now ill just try to find a full bottle to test that has a good thread. If it all works out ill look at what a die is worth ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: kruzaroad
Date Posted: 23 May 2026 at 10:08pm
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Cut one on the lathe. If your just tiding up thread basically a harden nut would do the job. |
Posted By: nunga
Date Posted: 25 May 2026 at 5:38pm
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So I solved the thread problem. I made a homemade die nut to clean up the threads.
I had to use another pressure gauge because the nice new one had a nipple on the bottom which got in the way of the shaft so I installed my old flat bottom gauge.
900 PSI is more than expected and it is winter as well
with 19 degrees so that’s good pressure.
So now i can move on with the build since the tests have proven very successful. ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: Pauly5
Date Posted: 25 May 2026 at 6:44pm
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That's looking great Nunga. I can't believe I had missed the earlier posts. I was thinking of doing a CO2 bulk fill carbine with a 30 cal barrel I have, so I will enjoy watching this.
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Posted By: kruzaroad
Date Posted: 25 May 2026 at 7:14pm
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What sort of pressure increase would say a 20° day give it. Pish it to a 950psi? How consistent are you expecting the refills to be? I'm guessing that they should be pretty well pressure regulated at refill place. Whats the next step? |
Posted By: nunga
Date Posted: 25 May 2026 at 7:36pm
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Next step is to make the 120cc tank, Hammer and ports on a hot summers day 30.0 °C it would push it up to around 1200 ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: nunga
Date Posted: 25 May 2026 at 8:44pm
To get 30FPE it will take approximately 2.2 grams of CO2 per shot with the 120cc tank i will have screwed to the Sodastream bottle, so the math says 182 of usable shots. So i can safely say 150 shots per tank.
------------- 2nd place HP springer - WFTF World Championships 2014 |
-Ec wrote:Posted By: kruzaroad
Date Posted: 25 May 2026 at 9:52pm
| Plenty for a evenings hunting. Goat/wallaby hunting at that. |
Posted By: BC_Clark
Date Posted: 29 May 2026 at 10:07pm
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I love seeing custom builds. Following this build with interest. CO2 is well capable of 30 ft-lbs in .25 and it may use less gas than expected. e.g. I got 26 ft-lbs in .35 from a 6" barrel and it used 1.1 grams per shot. |