Mid winter co2 break

[Ribbonstone]

As was once common on late-nite TV, "this is not a competition...just a demonstration...no wagering."

Just one guy...bored after taking care of the lawn...having time on his hands.

Warm spell in the middle of January....one of the things I both like/hate about living down here. Like the warm spells in winter....hate having to get out and cut the grass in the mniddle of January.

But as long as it was resoanbly warm (like 76-80f) tought I'd take a break from other formats and grab a "beater" co2 rifle.

DSCN2426 by Robert Dean, on Flickr

Only one thing "fancy"about this one.  Rebarreled to 5mm (HW blank),it still runs on the same "guts"as any other 12gr. QB ,uses 2X12gr., an aquarium thermometer stuck to the tube, and only very mildly adjusted to about 11-12 foot pounds.

Running in and out,using the thermometer, only shot when it wass between 71F snd 76F. 

Dug though the ammo locker,found 7 types of 5mm pellets.  Are more,but partial tinsand I wanted to test what I had enough of to use incase a "freak" orpahn pellet stood out (didn't).


YEs...those are desert sized paper plates and hand drawn "dime"circles...and 10-shot attempts rather than 5-shot...with a $40 4X scope.

DSCN2423 by Robert Dean, on Flickr

DSCN2429 by Robert Dean, on Flickr


Only #3/4/5/6 are in production...which works out well as they were mostly (3 out of 4) "winners" (although out of production #2 is about the same).




So bottom line(s):

#1. Original Sheridan Bantam slugs. This version (there were others) came in at 16.4gr./ 542fps./10.7 foot pounds.

#2. 14.3gr Crosman brown-box CP's.  589fps/14.3gr./11 foot pounds.

#3. JSB 13.7gr.   601fps/13.7gr./11foot pounds.

#4. 14.3gr.Benjamin (Black Tin) Cylindrical.  578fps/14.3gr./ 10.6 foot pounds.

#5. 15.9gr.JSB.   565fps/15.9gr./11.3 foot pounds.

#6. H&N Field TArget Triphy 11.4gr.644fps/11.4gr//10.4foot pounds.

#7. 23gr.EunJin.453fps. 23gr./10.5 foot pounds.



 It is a mess as far as weight vs.energy....low speed/low energy...and really no conclusiion to be made other than shoot what it likes.

It likes #3,5,and 6....only reason to mess with anything else would be beacause they have beenm hanging around the ammo locker for years; orpahns with no place to call home.

Those 3  in production pellets do see the weight/energy increase vs.the velocity/weight decrease(althoug not nearly so drastic at low power).

NOPE...can't be sure:

1.HAve no idea why the Shridan Original slugs shot well off to the right when everything else stayed reasonably close to vertical changes.

2. Do have an idea why the EunJins shot slower than expected.  Have 4 vcontact points to the barrel rather than just the 2 contact points of the others.

[Kevinbear]

Sorry about this being off topic but it seems like you might be pretty knowledgeable about the QB-78 22 cal., I have that I've put a ton of money into {Archer parts}and it has one simple problem that drives me crazy. I follow the procedure when replacing the co2 cartridges of lubricating the ends, cocking the bolt, putting them in back to back, screwing the cap on until I hear the first one puncture and the cap sticks then firing the gun several times to puncture the second cartridge.
The problem is the second one often will not puncture until maybe 20 shots, no way to tell which one is slow to puncture but the piercing pin in the cap doesn't seem very sharp.
The second problem is that I bought a second barrel for it in .177 and it refuses to feed pellets, they tip up and jam, I've polished the heck out of it and it still does it, it also ruins the O-rings on the bolt very quickly. Steven Archer has the O-rings but they're very poor quality and he wants a fortune for them, got any idea's.

[Ribbonstone]

Do think one 12gr. opening and not the other on filling happens more often than most owners think.

 Design has the top 12gr.  always popping first (as the end cap get screwed down), and your description has that happening as it is supose to. ONce that top one pops, the tube gets pressurized.

Cocking/shooting should pop the bottom 12gr. as the piecing pin is driven forward by the valve stem.

That sometimes doesn't happen.  Once the top 12gr. pops open,  ther gas tube is pressurized, and that pressure  resists the valve stem'smovement.  That pressure can be great enough to keep the piercing pin (which connects to the valve stem) from jumping out far enough to fully open the bottom 12gr. for a few shots.

(The hot-rodded ones usually don't have this issue....the extra striker spring strengh is normally enough to get the bottom 12gr. popped open on the first hit. LIKELY not popped open with as large a hole as you see when taking out the empty 12gr.)

NOw the neat thing is that is shouldn't make any difference.   Co2 is partly liquid and partly gas.   We run the gun on the gas.  Liquid co2 converts to gas after every shot (until we run out of liquid to convert).   With a QB, ONE 12gr. is enough to pressurize the tube and still have liquid co2  in reserve.   The 2nd 12gr. just adds to the reserve, doesn't increase the pressure.

 One thing to try if you really want both to pop open at the same time (although it make not make too much difference) would be to cock the open/empty rifle BEFORE you put in the 2  12gr. As soon as you hear the first "phiffffff"of co2 entering the rifle,quickly back the end cap off that fraction of a turn, and fire the rifle.

Depressurinzing co2 (top 12gr.)is cold ..cold equals lower pressure...low pressure equals a longer valve travel...valve movement equals a longer/stronger piercing pin movement.



As for the barrel issues.  If I read you right, have one(22) barrel that works/feeds fine.  Another (177) than doesn't.

Just so we are on the same page here.....you have a .177 bolt to go along with that .177 barrel?

[Kevinbear]

Thanks for the quick reply with good information, yes I have a standard .177 bolt I got from Steven Archer. Also have the high performance .22 bolt.
Also wondering that now I have a pcp gun and pump could I replace the end cap on the QB-78 with a fitting and pressurize the cylinder like it's a pcp gun?

[Ribbonstone]

You could...but would have to keep it to CO2 type pressures to be safe. Pressure is pressure...air, co2, or aardvark farts.  So something like a 1500psi fill, which with a typical QB  co2 temp in the summer....but likely would get something like 6 to 1o shots in a reasconable  velocity change.  FEWER for a rifle adjusted to be a hot-rod CO2, maybe more for a left closer to factory specs.

Basically, it's a recommendation not to... although in the spirit of  wanting to know, have done it (FOR A TEST).

[Kevinbear]

You could...but would have to keep it to CO2 type pressures to be safe. Pressure is pressure...air, co2, or aardvark farts.  So something like a 1500psi fill, which with a typical QB  co2 temp in the summer....but likely would get something like 6 to 1o shots in a reasconable  velocity change.  FEWER for a rifle adjusted to be a hot-rod CO2, maybe more for a left closer to factory specs.

Basically, it's a recommendation not to... although in the spirit of  wanting to know, have done it (FOR A TEST).

No I have not, is there a cap with a fitting available? Wondering why you would only get 6-10 shots if you filled the chamber to the same pressure as the CO2 cartridges provide? I normally get about 40 good shots from the dual CO2 cartridges.

[Ribbonstone]

It's that liquid to gas conversion with co2.   


Co2 is partly liquid (which is why it is sold by weight and not pressure).   At any given airgun temp, when contained in a  tube, co2 is part liquid and part gas.

We run airguns from the gas.

When a bit of gas is used during a shot, part of the liquid  transforms into gasto get back to "even".   This keeps happening so long as there is liquid co2.

 Air is all gas....no "reserve" liquid to be transformed. 

So if we fill a QBwith air, each shot decreases that pressure with nothing to be transformed into gas to take the used pressure's place.



Because I included "winter" in the first post...will mention some thiongs.

Co2 wis a liquid/gas combo that wants to be "even".

To get "even" it will automatically transform liquid into gas to get back in balance.

How much liquid and gas in a given container( like a QB tube) depends on temperature (and other factors we can't change).

Cooler equals more liquid... less gas...less pressure.   Hotter equals less liquid...more gas...more pressure.

[Kevinbear]

It's that liquid to gas conversion with co2.   


Co2 is partly liquid (which is why it is sold by weight and not pressure).   At any given airgun temp, when contained in a  tube, co2 is part liquid and part gas.

We run airguns from the gas.

When a bit of gas is used during a shot, part of the liquid  transforms into gasto get back to "even".   This keeps happening so long as there is liquid co2.

 Air is all gas....no "reserve" liquid to be transformed. 

So if we fill a QBwith air, each shot decreases that pressure with nothing to be transformed into gas to take the used pressure's place.



Because I included "winter" in the first post...will mention some thiongs.

Co2 wis a liquid/gas combo that wants to be "even".

To get "even" it will automatically transform liquid into gas to get back in balance.

How much liquid and gas in a given container( like a QB tube) depends on temperature (and other factors we can't change).

Cooler equals more liquid... less gas...less pressure.   Hotter equals less liquid...more gas...more pressure.

Thanks for having the patience to educate me on such things, my garage is attached but not heated, it's very cold in the winter, it was in the low 40's today. Even though the QB-78 sits in my office where it's warm, how many shots at full power can I expect from it once taken to the garage?

[Ribbonstone]

No real way of knowing.

Can use one of the published co2/temp/ graphs to get an idea about pressure to be expected at a given temperture....which gets kind of coplicated/clutters as that is also dependent on the liquid to gas relationship.

Won't predict gas use per shot.

Colder it gets, the less pressure.  In most co2 airguns,that would equal both less speed and more gas use per shot. You'll get lower speeds and fewer shots.

Starts to get seriously slow at some temperture/pressure.

Co2 also tends to self-cool.  That liquid to gas conversion cools the remaining co2 a little.  Shoot fast, and that "little"adds up quickly, and in coolweathere it takes awhile for the rifle/co2 to get to ambinat temp.

Not just the outside of the gun.....ambinat temp. has to basically soak through to the co2.

Which winds me back to why the 80F temps in the middle of January and the peel-n-stock thermometer on the air rifle.  I'd not bother with co2 if it weren't warm enough.


OK...lets find that pimped-up (all colorized and stuff)  graph:

Co2_pressure_vs_fill_phases by Robert Dean, on Flickr

Lets cut everything to the right that is past 100% fill.  With a 12gr.rifle,can't somehow inject more than a fill the 12gr. come with,and going past 100% safe fill with any co2 rifle would be foolish.

Cut everything off to the left  from 20-25%rated fill. It's about that fill precentage when the co2 starts to  shoot down(and we think of recharging the rifle with new co2 cartridges).

LEts strip off all the temp. lines above 105-110F  and those below something like 55-60F (where co2 seriously starts to get slow).

Which leaves the center of the graph....where most actually use a co2 rifle: between 100%and 25% fill,from 55F to 105F.

Co2_pressure_vs_fill_phases by Robert Dean, on Flickr

Still shows a rise and fall of pressure vs.tempeture, just doesn't look near as drastic as the larger graph (which is accurate, just includes sections we'd not normally use for airgunning).

Still a pretty large pressure change in thecut-down graph....like 700psi to about 1200psi even when we avoid all the extreams of the big graph.

[Kevinbear]

Ribbonstone , thanks for the great information, sheds light on a lifetime of problems with CO2 guns!
One thing I have to point out that is amusing you said "Which leaves the center of the graph....where most actually use a co2 rifle: between 100%and 25% fill,from 55F to 105F."
 It's been 55F here in the last 4 months but only for an hour or two midday. It was 50F earlier in the week one afternoon and I saw people wearing shorts! The news people like to play up warm weather here in the winter because of tourism but the truth is it's cold here from November 1st until April sometimes May. Unless you have a heated garage your better off to shoot spring guns in the winter.

[Ribbonstone]

Co2 just isn't all that cold friendly....not even real "cool" friendly.

1. Prefer 12gr.  or "tankers"that actually have the tank attached(assume there is a decent place near by to get paintball tanks filled correctly).
Bulk filling is actually more of a problem than tank filling a PCP....if I'd dealing with big tanks and fill hoses, may as well be a PCP.
88gr. AirSourse types just cost a bit too much per ounce of co2.

2.  Co2 is temp. sensitive....I just don't fight the world....or go out in the cool/cold with it.
Lot of people have tired various ways to beat that with  various types of warmers. Somehow it just feels like wasted effort when there are other types of airguns that work fine in the cold.  JUst feels like  working out a way to eat potato chips while scuba diving...enough effort you likely could, just don't stop and ask youself "why?"

3. I don't try to hot rod co2. MAy tune it up or down a little bit, but co2 is just not a good candidate for PCP type power.
Kind of like the folks that spend hours making  racing belt sanders (yeah...that acutally is a "thing").  In the end, you get a fast belt sander that isn't real great at sanding.


HAd a 2nd warm day yesterday and broke out two more 12gr. rifles for the same 25 yard pellet testing.

.177 Umerex/RWS  850. Due to the mag size, 8 shot groups.

DSCN2430 by Robert Dean, on Flickr

DSCN2433 by Robert Dean, on Flickr

1. JSB 10.3gr.
2. AA 10.3gr.
3. Crosman 10.5gr.
4. Crosman 7.9gr.
5. AA 7.3gr.
6. RWS SuperDomes 8.3gr.

None were horrible, the barrel isn't real picky.

.177 Spa "Plinkster". Don't know how well the  Diana  TrailScout's 3 12gr. popping system actually works,this old version pops only one 12gr.....but the "guts" are pretty much the same.

Also 8 shot groups.

DSCN2434 by Robert Dean, on Flickr

DSCN2435 by Robert Dean, on Flickr

1. Crosman 10.5gr.
2.AA 10.3gr.
3. AA 7.3 gr.
(#4 was too bad to number or count).

Basically 2 out of 4..going to have to count the "oops". Would have to count this one as picky, but shoots well with what it likes.

HAd one more co2 repeater to try....Beeman 1085...but the weather makes it kind of unfair. Not just colder, also a lot more windy.  If it calms down/warms up a bit later, will give it a go.