Co2/temperture/ tuning

[Ribbonstone]

Summer time co2.

I've tried setting/adjusting these 6 co2 rifles up to be tolerant some temperture change.

But I've never tested a group of them at the same time.

The "lazy man's" test of 20F temp.change.

You'd pretty much have to be body-numb not to notice 20F of temperture change, but it happens when you bring a co2 rifle out from the house (74F) and into the heat (94F).

Can also happen when outside with a sudden thunder shower,or a really nasty cold front passes suddenly while you are out-and-aboutwith a co2 rifle. (can think of that as your fault for not paying attention to the weather news).

"Lazy" 20F change would be just letting them normalize inside the house...then letting them normalize in the heat (in the shade).

DSCN2841 by Robert Dean, on Flickr

OK...even with trying for an even spread, its not as even on the extermans (really slow/really fast) as I hoped.

Basically  the ones tuned to be slow (A/B) were either "even" or 2.5% slower with an increase in temp/pressure. 

The hot-rod modded one (F) gained +4% velocity with the temp/pressure changed.

Am going to call C/D/E as "good" over this 20Fspread as I can't really tell (at 25 yards) the changes on targets.


WHY NOT 4%?  After all,that's a pretty common percentage for non-regulated PCP's velocity change (sweet spot).

At 25 yards, am likely only THINKING that I can tell the little shift in elevation from a 4% change.  Pretty sure I can tell at 5%.

Not really able to see a 2% change.

Am going to call the short range (25-30yard) shift something more like 2-3%..and that only for the ones accurate enough to tell a small shift in group center.

12gr. rifles(out of order)...and one didn't get tested. That one is on the shop-bench getting a little adjustment/figuring out.

DSCN2724 by Robert Dean, on Flickr

CLIMATE:

I like 12gr.becasues they are"lazy simple"and I'm not normally looking for power with a co2 rifle (that's what PCP's are for).

It'sNew Orleans...so it stays between 74-94F for a long long time...I've seated through many a Thanksgiving and Christmasmore times that I've been bungled up in a coat.

JUST because they shoot slower in the cool weather (like "F"),does not mean they aren't consistant and accurate at stable lower temp...they are just slower.

[wolverine]

Very interesting.  Temps here during co2 season range from 75 - 95° so i sighted the 2260 & 2400kt in on an 85° day while shooting in the shade.  I store them in the garage from june to october to help keep them "acclimated".  This morning when i started shooting it was 73°.  Now it's 86°.  so far i havent seen any poi change at the 25 yards im shooting. Temp should reach low 90s so we'll see what happens later.

[rsterne]

Certainly CO2 guns can be tuned for a minimal velocity change over a 20*F range of temperature.... However, very few come from the factory like that.... and if you are tuning for maximum power, then higher temperatures will cause a significant velocity increase....

Bob

[Dave S]

I haven't seen a gun yet that didn't have to be "Scope Tuned" for existing conditions. Especially Co2 guns! dave

[grand-galop]

Rib!!

I see that you are fiddling with a good margin and you succed since you post the results..

I dont mind to be so eloquant with tuning for CO2  since we can get 20* celcious spread variation in one day frequently...

The cost and convience of co2 is enouf reason to get the most of it..

I see a good  use of your setup as a camping  compagnion or a car rifle or on the fly rifle..

[skorec]

I have done automatic heating for CO2 using for my QB78.
http://forum.gunshop.cz/download/file.php?id=34812&mode=view

Aafter that i hav done universal CO2/Air hand valve  cap  with forester  nipple.
Today I filled it at home  only  by using regulated 1500 PSI output from  scuba tank for 3-5 shots . and accuracy is acceptable.
https://www.gatewaytoairguns.org/GTA/index.php?topic=125568.msg1228415#msg1228415

For more shots ( 60 ) I still I may use CO2 cartridges whit simmilar accuracy.

[Hoosier Daddy]

I have often wondered about this with my Co2 guns, because going from 72 indoors to 92 outdoors is common this time of year (June-Aug).

When you did your test, how long did you wait between shots?
I would think with the cooling effect of Co2, that within 2-3 shots in leisurely loading and shooting the internal temp would drop 20 degrees back to the "indoor" temp.
 If I wait 30 seconds between shots the tube / breech at the valve area still eventually cools down enough to get condensation on humid days like we have now.

Or was that even a consideration?

[Ribbonstone]

Lot of past co2 posts.

Yeah,were temp. stable when started...shot slow pace. 

Can't really tell how stable they stayed internally (which is all the gas cares about),but the chronograph readings were even

Likely the ones that showed a decrease in  (A and B) would stand an even cooler start (like maybe 68F)and show less loss if I were to measure something like 65F to 85F.

Likely the ones that gained velocity would have shown a more even spread if I used  something like 80-100F.

Am putting "F" back to it's last setting....will drop a bit of speed, but hopfully come closer to what "D" did.

Strirker hitting a valve stem.....striker force vs.the gas pressure holding the valve closed.

Pretty much like a non regulated PCP....harder the strike to the valve,the higher the pressure it opens.

So like a non-regulated PCP,there is a "sweet spot/plateau"where the shots are pretty even over a widepressure range. 

A jacked up PCP will show the "falling off a cliff" type shot count if it's striker hit is too heavy.

Aadjusted down striker force PCP will show a long "climb" to a pleateau.

Co2 pressure is likned to temp. (usually write "termp/pressure" to remind myself of that) and consider than co2 self-coolsby liquid/gas conversion/expasnion when shot.


So..with co2 you can set one up "cranked up"...but it shows a quicker speed decrease from temp/pressre decrease.  The more gas you use,the faster it self-cools.

Can set one up to run in the middle ground that runs over a wider range of temp/pressure. Will stay in the "sweetspot" the longest as temp/pressure changes.

Can set one with a lite striker that will adctually gain speed as temp/pressure decreases.

-----------------

Co2 is interresting  becasue the relationships are more compex than with air.

Like co2...but if power is you game, it's the 2nd least a power producting airgun power plants (and  an "air gun" that isn't really an "air" gun). SSP'scan manage as much power (earning 1st place in the "slow"catagory).  Normal springers can get 20-30foot pounds....cheap PCP's can manage 30-50foot pounds....MSP's can manage 18-22footpounds (although they need to be modded a bit).

Power is not co2's "thing"...but consistency and accuracy can be.


PERSONAL OPINIONS:

Pre-heating co2 is much like   adjusting a 2K PCP to run on 3K. Can do it,but better think about the whole system.

There is a "wall" with co2.  Co2 will get to the point faster where more gas ejection per shot does not results in a speed increase.

Much better off (if looking for a power increase) just improving the gas flow to the pellet....smoother/larger path helps more than just jacking up the striker spring.

[Dave S]

Lot of past co2 posts.

Yeah,were temp. stable when started...shot slow pace. 

Can't really tell how stable they stayed internally (which is all the gas cares about),but the chronograph readings were even

Likely the ones that showed a decrease in  (A and B) would stand an even cooler start (like maybe 68F)and show less loss if I were to measure something like 65F to 85F.

Likely the ones that gained velocity would have shown a more even spread if I used  something like 80-100F.

Am putting "F" back to it's last setting....will drop a bit of speed, but hopfully come closer to what "D" did.

Strirker hitting a valve stem.....striker force vs.the gas pressure holding the valve closed.

Pretty much like a non regulated PCP....harder the strike to the valve,the higher the pressure it opens.

So like a non-regulated PCP,there is a "sweet spot/plateau"where the shots are pretty even over a widepressure range. 

A jacked up PCP will show the "falling off a cliff" type shot count if it's striker hit is too heavy.

Aadjusted down striker force PCP will show a long "climb" to a pleateau.

Co2 pressure is likned to temp. (usually write "termp/pressure" to remind myself of that) and consider than co2 self-coolsby liquid/gas conversion/expasnion when shot.


So..with co2 you can set one up "cranked up"...but it shows a quicker speed decrease from temp/pressre decrease.  The more gas you use,the faster it self-cools.

Can set one up to run in the middle ground that runs over a wider range of temp/pressure. Will stay in the "sweetspot" the longest as temp/pressure changes.

Can set one with a lite striker that will adctually gain speed as temp/pressure decreases.

-----------------

Co2 is interresting  becasue the relationships are more compex than with air.

Like co2...but if power is you game, it's the 2nd least a power producting airgun power plants (and  an "air gun" that isn't really an "air" gun). SSP'scan manage as much power (earning 1st place in the "slow"catagory).  Normal springers can get 20-30foot pounds....cheap PCP's can manage 30-50foot pounds....MSP's can manage 18-22footpounds (although they need to be modded a bit).

Power is not co2's "thing"...but consistency and accuracy can be.


PERSONAL OPINIONS:

Pre-heating co2 is much like   adjusting a 2K PCP to run on 3K. Can do it,but better think about the whole system.

There is a "wall" with co2.  Co2 will get to the point faster where more gas ejection per shot does not results in a speed increase.

Much better off (if looking for a power increase) just improving the gas flow to the pellet....smoother/larger path helps more than just jacking up the striker spring.

Not much I could add to your usual words of wisdom here. I have found that heating the power source albeit powerlets or bulk- fed tube  to max 105 degrees F. seems to be the best way to achieve max efficiency regardless of the ambient air temperature within a  reasonable range 72- 90 F. Also, I test velocities at 115 feet above sea level (my attic). Next month we are going to be testing at Joshua Tree which is 3000 feet above sea level just to see the variance in air density. Should be interesting. If my theory proves true, I should be able to achieve 12 fpe or better with my Crosman 180. Best I can get here at home is 11.3 fpe . dave

[Ribbonstone]

How well does that work/howmuch work to make one a 5 foot pound(ish) indoor 10meter shooter?

Not a silly question...it's something I do with at least 2 of them....but am balancing the effort/mods needed to make it a short/fast/limited valve cycle...plus the temp requirement....when all I want to do it shoot bullseye.

[Dave S]

How well does that work/howmuch work to make one a 5 foot pound(ish) indoor 10meter shooter?

Not a silly question...it's something I do with at least 2 of them....but am balancing the effort/mods needed to make it a short/fast/limited valve cycle...plus the temp requirement....when all I want to do it shoot bullseye.

Didn't mean to go off on a tangent here. Yes, slower will probably produce better accuracy. dave

[Ribbonstone]

Not really willing to try another artificial heat source (although electric baby-bottle warmers/motor cycle handle warmers have worked out when I was a real co2 winter-nut).

More of a go-with-the-flow kind of guy, not fighting the natural temp.as much as adapting the rifles to deal with a wider  temp. change. Forsaking power for consistency.

[Back_Roads]

 I have one qb that actually valve locks @ 85+, but shot excellent at temps at around 55 - 70, I may just keep it that way for the fall seasons.

[Dave S]

Not really willing to try another artificial heat source (although electric baby-bottle warmers/motor cycle handle warmers have worked out when I was a real co2 winter-nut).

More of a go-with-the-flow kind of guy, not fighting the natural temp.as much as adapting the rifles to deal with a wider  temp. change. Forsaking power for consistency.

Ribbonstone, THE most accurate pellet guns I've ever shot at a 10 meter Qualified Olympic Range would be either a Feinwerkbau side-cocker 8.4 gr. .177 or a  Co2 "Daisy Avanti" same. Both guns clock below 450 fps. The target below proves how accurate the Daisy was at 10 meters. Paid $2.00 for 3 shots, got my money back when it was verified  by 2 other
range masters that the sights were off. High and to the left!  I do have one Co2 gun that can equal this.... and that would be an early '90's QB 77 Mac-1 Chinese C02 Bulk-fed  original .177.  dave
Less can be more when tack-driving.

[Ribbonstone]

Have tired co2 and Air (either PCP or HPA) in a few accurate/sporter type rifles.   5 or 6 rifles more seriously tested than others.

Figured that was a little more even...same trigger/same barrel...than two different rifles.
Of course co2 was always slower than air...power wasn't the point - accuracy was.

co2's average accuracy was always a little bit less from the same platform.

 Could be becasue the rifles were more nicly adjusted for air use....could be the difference in wind effects...could be I never found the perect pellet...lots of "could be's".

Not talking much... averages at 20 or 25 yards were small..... .22" average looks a lot like .19"...so does .31" vs .27"....but it's also about 10%.

Never had the fun of a real "big boy"co2 match rifle (like a FWB C60)....did have a few "starter"co2 rifles (Daisy 887 + 888/Alfa Proj ). The Alfa (bought used) turned out to be esp. accurate  (for a 12gr. rifle, it's freakishly accurate).



Problem being...wife got a look at it....and claimed it. So now I get to keep it running rather than shoot it often.

(LESSON: wife is a lot less likely to claim and ugly/heavy rifle than a stylish/lite rifle....avoid pretty.)

So this is my best 22 yard average (benched) with the apature sighted Alfa....making maybe 4.3 foot pounds.



Of couse (before my wife claimed it) had to try it with a simple 3-9X scope....which explains a couple of extraholes.set screw in the barrelhousing).
But at 20 yards rahter than 22 yards:





So that stands as the most accurate 12gr.running rifle so far (and considering the fate of 12gr. running rifles,likely not going to beat it).

But as you can see from the first post....it's not higher temp. stable....runs it's best in "indoor" temps.

[Dave S]

Nice grouping! Does that Daisy have a lb. adjustable trigger? Looking to get either an 887 or 888. These are bulk fed guns and that is right up my alley. Already set up and feeding over 17 rifles and pistols. The Avanti I shot at the Phoenix Club was Bulk-Fed 2 1/2 oz tube as is the 887, 888.....what gives with yours? No Bulk- Feed? BTW, Beautiful Rifle! dave

[Ribbonstone]

Kind of under the radar,but Daisy has been trying other makers match rifles for a long time. 

Are FWB300'swith Daisy markings, Gamo 126 with Daisy marklings,CZ200T's marked as Avanti Valiants...currently Daisy 599 version of a BSA.  Wasn't keeping score...could be other Daisy marked rifles(and some times the marking is subtle....like a stamping on the accessory rail).

Unless you are handy as heck, better to live with the 887/888 trigger.  Can be modded, but not a whole lot of fun and a high chance of screwing it up.

Those Avanti co2 tubes are quite good...and they made them easier to bulk fill by using common paintball thread sizes. 

http://thecmp.org/wp-content/uploads/DaisySporterTriggerMod.pdf

Alfa Proj attracted me because it ran on a single 12gr.....wife found it too pretty and took it over. Did come with a little bulk fill end cap...tank...and a fitting for the odd threads ,but as the chamber in the grip is only long enough for a 12gr,it wouldn't bulk fill enough co2 to put up with the trouble.

[Dave S]

Thank's for the info and link, Ribbonstone! I think I'm gonna' pass on any more guns right now. A good trigger is a must for precision shooting. I have 3 vintage Crosmans with the fully adjustable trigger blocks and they are really hard to beat . Not being able to easily change the trigger spring tension is really a non-stater for me Thank's again, dave                             

[Ribbonstone]

Not really too trigger dependant....appreciate a really good one,but past a certain point,haven't found a benefit on targets.  A clean break at 1.5-2 pounds works just about as well for me as 2 oz.

OK...technically,in slow fire,they both break at 2oz.....tend to only increase pressure when the sights are "perfect"...hold what I got...apply a bit more....hold what I got...and (if a clean crisp break) the  2pound trigger lets go with 2 oz.

Truthfull...although the 887/888's shoot well....can really tell they are Daisy products when you take them apart.     Work,last,are surprisingly durable....but  the construction somehow bothers me on a rifle at that price point.

Considering some of the ugly guys I shoot...that bit of snobbishness bothers me.

[AndyKunz]

I have done automatic heating for CO2 using for my QB78.
http://forum.gunshop.cz/download/file.php?id=34812&mode=view

What parts were you heating?

I did a 3-zone heater for my old 1077.  I used coils on the cartridge holder, the valve, and the breech end barrel (about 1/3 the barrel length).  The cartridge was set for 90F, the valve didn't make any difference, and the barrel heat was what really made the difference.  That kind of makes sense, too, because that's where the expansion is really happening.  I'll have to dig up some pictures of the mods.

Andy