Author Topic: .410 bore CO2 powered gas volume (Read 7026 times))

Doug Wall · « **on:** July 28, 2018, 11:51:36 AM »

Hi guys! I've got a little project that I'm thinking about building. I have a .410 shotgun, 24" barrel and I'm thinking about building a CO2 powered big bore. I'm thinking about building a QEV valve that will handle 850ish psi, that will give me a big volume quick blast that should power things nicely. I realize that the QEV valve will waste some gas, but minimizing the volume to the vent, will minimize gas waste. The quick opening blast is worth the waste in my mind, and I should be able to build the valve, using appropriate fittings, with minimal machining. If I read the specs correctly, it appears that 1/8" pipe should be able to handle the pressure. My main question is what reservoir volume on the QEV do you think that I might need to optimize power without using excessive gas? I'm thinking that it might be a fairly small volume.

Rob M · « **Reply #1 on:** July 28, 2018, 11:55:59 AM »

I actually built 2 versions of something similar in 50 caliber

https://www.gatewaytoairguns.org/GTA/index.php?topic=143832.0

I found that 25-80cc was optimal range with the usual diminishing returns.. 40 cc seemed to peak the muzzle velocity with 177 grain round balls and a 36 inch barrel.. Really fun project , the version 2 i have yet to finish so i dont have a post to link,.. Some basic math would suggest a .410 could operate at max close to 25ccs .. ( depending on barrel length )

Also noteworthy , mine was a displacement piston where the gas simply fired the piston rearward exposing the TP.. more efficient that i thought , but the sear load required a springer trigger which lead down a rabbit hole.

rsterne · « **Reply #2 on:** July 28, 2018, 12:51:34 PM »

By QEV valve, I assume you mean a "dump valve" operated by a pilot valve?.... First I suggest you read Rob M's thread, many of your questions will be answered there.... In general terms, reasonable gains in power are achieved with a valve volume up to half the barrel volume, after that, you will get little power for the additional gas used.... Your barrel volume is 3.17 CI = 52 cc.... so I would use a dump chamber of no larger than 26 cc.... JMO....

Bob

Doug Wall · « **Reply #3 on:** July 28, 2018, 04:11:22 PM »

Thanks for your insight! Yes, I was thinking about the QEV being a pilot operated rapid dump valve. There are a couple of neat videos on Youtube of some .50 guns operating this way. All of the commercial valves that I've seen, are rated at somewhere around 150 psi, and some of these builds are running them at 400 psi. No thank you! With a properly rated T, and appropriate other fittings, I should be able to put a safe one together for CO2 pressures.
I have reads Rob's thread, and it provided some useful info. I suspected that the reservoir volume was going to be something like the 26 cc that you estimated. The reason for the .410 build is that after doing some searching, I was able to find a .410 barrel, that will allow me to use .410 shot cups for either a ,380 ball, or shot, with good bore sealing. It also seems like a good size between the smaller .35s and the .50.

rsterne · « **Reply #4 on:** July 28, 2018, 05:26:10 PM »

You can put three x .36 cal balls (OOO Buck) into a .410 shot cup intended for 1/2 oz. of shot....

or just 1 or 2, of course.... I used shortened all brass Magtech shells for my .410 Hayabusa…..

I drilled the primer pocket out to 3/8".... and used a cardboard over-shot wad on the front end....

I was getting in the mid 800s on 3600 psi HPA with the three 68 gr. OOO Buck....

Bob

Doug Wall · « **Reply #5 on:** August 09, 2018, 07:44:30 PM »

I've got the basic mechanism finished and working. It gives a pretty good blast, but I'll have to wait till I get some shot cups and balls in to test it over a chrony, to see where I'm at.

Rob M · « **Reply #6 on:** August 09, 2018, 07:46:13 PM »

Quote from: Doug Wall on August 09, 2018, 07:44:30 PM

I've got the basic mechanism finished and working. It gives a pretty good blast, but I'll have to wait till I get some shot cups and balls in to test it over a chrony, to see where I'm at.

I cannot wait to see this

Doug Wall · « **Reply #7 on:** August 09, 2018, 09:27:19 PM »

Here's an "exploded view", with everything in the correct orientation. After everything gets tested and tuned, I'll add some "furniture" to it.
The reservoir pipe is oversized, and is currently filled with about a 40% spacer. By making the spacer larger or smaller, I can tune the gas volume.

Rob M · « **Reply #8 on:** August 09, 2018, 11:51:55 PM »

awesome.. I had a similar idea for the volume when I started.. I started with 1/4 inch wall tube , and when I needed to increase volume I bored the tube slightly , and when I wanted to decrease, I was going to add Delrin bushings.. ( never needed to add those _)\ the wall ended up being about .100 in the end which worked out to "okay " safety for the gas pressure

Doug Wall · « **Reply #9 on:** August 10, 2018, 01:05:09 AM »

The nominal wall for the 304 ss pipe is 0.109", with a 3500 psi rating. The cap is 3000.

Rob M · « **Reply #10 on:** August 10, 2018, 01:13:52 AM »

should be deafening !

( mine was quite loud when hitting the higher numbers

Rob M · « **Reply #11 on:** August 11, 2018, 06:07:39 PM »

any news Doug ?

Doug Wall · « **Reply #12 on:** August 12, 2018, 09:19:03 AM »

Quote from: Rob M on August 11, 2018, 06:07:39 PM

any news Doug ?

Still waiting for projectiles. They should arrive in a couple of days. When I get them, I'll run a few over the chrony to see where I'm at. I've fired a bunch of blank shots, and everything seems to be working correctly. I've figured out a stock for it. I'm going to have a couple of 3/8" thick slab sides that will go over the "T" valve and pipe reservoir, and sandwich a forearm that will clamp to the barrel, and a shoulder butt stock about 3" behind the capped end of the pipe reservoir.

Doug Wall · « **Reply #13 on:** August 15, 2018, 05:30:07 PM »

Quick update- I'm still waiting for my shot cups and 0.375 mold. I'll cast some balls as soon as I get it. I've been doing some reliability tests on my DIY QEV, and I'm finding that the rubber piston that I made is hanging up occasionally. I took it apart today and polished the inside of the bore, and I'm going to make a Delrin piston that should slide more reliably. Results coming as soon as I can get these done.

Doug Wall · « **Reply #14 on:** August 22, 2018, 10:57:37 AM »

Here's the latest, and close to, final configuration. As you can see, it's compact, at just about 36" long. It's currently shooting a 0.375, 80 grain ball, at about 400 fps, for about 28 FPE. I'll play with the reservoir/plenum volume a bit, as time permits, to see if I can optimize gas usage/velocity. That, and any accuracy testing, will have to wait till after an upcoming vacation.

Rob M · « **Reply #15 on:** August 22, 2018, 12:36:32 PM »

I must say that looks freakin awesome man congrats

a1rgunz · « **Reply #16 on:** August 22, 2018, 01:52:16 PM »

That looks really good! If you have access to a hand pump and a regulated ninja bottle, you'll probably get even better performance. You've got plenty of power as-is though, a 80 grain roundball at 400 fps packs a good punch.

Doug Wall · « **Reply #17 on:** August 22, 2018, 05:31:22 PM »

Quote from: Geo Schoonmaker on August 22, 2018, 01:52:16 PM

That looks really good! If you have access to a hand pump and a regulated ninja bottle, you'll probably get even better performance. You've got plenty of power as-is though, a 80 grain roundball at 400 fps packs a good punch.

I have pondered the HPA option a bit. I might get about 10% higher velocity with air. I'd have to calculate the gas usage, to see how many pumps to fill, and how many shots per fill. This thing seems to be a bit of a gas hog, and I do have a bulk fill set up to fill with.

rsterne · « **Reply #18 on:** August 22, 2018, 06:23:30 PM »

A while back I played around with a modded 22XX CO2 platform in .357 cal with a 28" barrel.... The modifications were fairly extensive, I tried both a twin 12 gr. CO2 setup and a bulk fill of the same tube (inside length equal to two 12 gr. cartridges)... There was not much difference between the power, the bulk fill had an extra shot or two....

The valve was a modified Disco valve, with a 1/4" throat, 1/8" valve stem, and 7/32" porting right through to the barrel.... pretty small for a .357, only 60% of the bore.... The hammer was a stock 22XX hammer, with a Disco hammer spring.... The total valve volume, including the volume for CO2 gas around the outside of the cartridges, was 11 cc.... With a 67.4 gr. roundball I hit 555 fps, and with the 77.8 gr. JSB pellets the gun was capable of 515 fps (46 FPE)…. It was surprisingly efficient, getting 6 full power shots before falling below 500 fps using two 12 gr. cartridges....

I would think that using this setup on a .410, with suitable sized porting, should provide greater velocity with an 80 gr. projectile, because of the much greater bore area available for acceleration (30% increase) compared to the .357.... That should more than make up for the 14% shorter barrel.... The shot count would be less, to be sure, because of the 13% larger barrel volume to be filled with CO2.... but there should be a significant increase in FPE available (calculations would predict 13%)…. I would expect over 50 FPE for sure....

I never tried my .357 with a larger plenum, my 11 cc setup was just under 25% of the barrel volume.... That's a good balance between power and efficiency, but there should be more power lurking there with a 50% valve volume.... but at the cost of double the CO2 use (3 shots instead of 6)....

Bob

a1rgunz · « **Reply #19 on:** August 22, 2018, 08:14:25 PM »

Quote from: Doug Wall on August 22, 2018, 05:31:22 PM

I have pondered the HPA option a bit. I might get about 10% higher velocity with air. I'd have to calculate the gas usage, to see how many pumps to fill, and how many shots per fill. This thing seems to be a bit of a gas hog, and I do have a bulk fill set up to fill with.

Just for a comparison, 10 years ago I built this airgun:

The heart of that airgun was a full port 1/2" ball valve. It was pulled open by a spring when the trigger was pulled. It would shoot patched 85 grain roundballs at 468 fps. I filled it to 400 psi with a shock pump for each shot.

The barrel was a smoothbore .40 caliber and was 32" long. The air chamber had a volume of 1.98 in^3.

I think your airgun has a lot of potential waiting to be unlocked. My gut tells me that some optimization of the QEV is the key.

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.410 bore CO2 powered gas volume

Author Topic: .410 bore CO2 powered gas volume (Read 7026 times))