SpudFiles

i need help on the lp/hp pressures for the piston and any knowledge in this area. thanks

Well the operating pressure of a 30.06 semi-auto rifle is about 53,000 psi if i remember correctly. People here manage to get an auto working with about 100-200 psi. If you were much more specific about what exactly you are trying to work out we could probably help a little more.

Have a good read through this thread

i am building a semi auto 15.5 mm co2/ air rfle. the design peramiters are built with hand tools, purely mechanical operation, variable pressure, reliable and field strippable. ( i am well skilled at hand making very complex parts) i have been looking at the blow forward design but i am having trouble with activating the valve. i would much rather go with a design similar to the m16 with a gas piston recoil because i am wanted to use cartridges so i am able to have a wide varity of munitions. take in mind i live in a small rural town in alaska so i have limited supply of materials. i have many designs for military simulation paintball gear. thanks!

Your construction is going to have to be figured out extremely well. If you are making paintball guns then you'll struggle to get a decent recoil kick out of it without a really high blow back piston surface area to barrel bore ratio.

If you are modelling on the gas impingement system of the m16 then you will have to figure out how to

A. Reduce dead space
B. Reduce the negative impact on the paintball's velocity
C. Figure out how you will fuel the thing because it's going to suck a lot of pre compressed air. You might need a large tank to avoid not getting many shots off one fill.

I really look forward to seeing what you come up with because from what you've said and your name it appears you could show us some really nice aluminium milled gunnage. Yummy.

i am open to more efficient designs. the rifle it self isnt designed to normally fire paintballs. its more that if i want to do so, all i have to do is load the magazine with that particular ammunition. i would like to do something similar to the DBB system ( double barrel blowback) used in tradition paintball markers.....but that wouldnt be any fun. im currenty working on a illustration of a prototype blow forward system that just popped into my head. i shoud have it posted within a few hours. thanks for the input much abliged

This is a design I hard drawn up for a gas piston operated cartridge fed design, never built it though.

i was thinking about a low pressure valve at the end of the piston rod and using it similar to a relay to then activate a high pressure valve to then cycle the bolt and cock the the striker for firing

her is my concept design of a blow forward catridge firing air/co2 rifle that i finished last night. this particular design will allow to have 70% of the length of the rifle to be barrel. it comes in handy if your buiding a carbine and/or rifle that has high accuracy. feel free to post any comments, thoughts, ideas and improvments to my design

heres a better image

That's a fairly complex ejector/extractor mechanism you've got there, but if you can make it, it can work. My one gripe is that flow restriction in the bolt that will certainly hurt performance.

the air flow restriction in the bolt is one of my main concerns. i have limited access to materials do to the fact i live in rural alaska. i do not like to use any other materials than brass, aluminum, steel, copper, and that teflon stuff ( the name excapes me) i obtain my materials by recycling. the frame of my rifle is built out of 1"x1 1/2" aluminum channel.
any help is much welcomed so i can further refine and finalize my design.