 |  | | | |  | |  |  | 8.2-8.5 .177 grain pellets okay for a 1000 FPS rated break ? |  | |  |  | |
 Posted: Thu Jan 07, 2010 9:43 pm |
 |
|
| redroush00 |
| Member |
|
|
| Joined: 31 Dec 2009 |
| Posts: 78 |
|
|
|
|
| My Ruger seems to shoot 7.0 to 8.5 just fine. Is there any long term issues using 8.5 grains in this gun? I know i shhouldnt shoot the 9-10 grains but what about the 8's? No harm done? |
|
|
|
|
|
|
| |  |  | | | |  |  |
| | | | | | | | | Re: 8.2-8.5 .177 grain pellets okay for a 1000 FPS rated bre | | | | | |
| Posted: Thu Jan 07, 2010 10:08 pm |
|
|
| donec |
| Senior Member |
|
|
| Joined: 19 Dec 2009 |
| Posts: 836 |
| Location: central Texas Pflugerville area |
|
|
|
| redroush00 wrote: |
| My Ruger seems to shoot 7.0 to 8.5 just fine. Is there any long term issues using 8.5 grains in this gun? I know i shhouldnt shoot the 9-10 grains but what about the 8's? No harm done? |
I'm new to all this and would like to know why we should not use 9-10 grain pellets and just what range pellet grain is acceptable for a 1000 fps break barrel springer like Ruger, Crosman etc. |
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Thu Jan 07, 2010 10:39 pm |
|
|
| Lipoly |
| Veteran Member |
|
|
| Joined: 06 Dec 2009 |
| Posts: 241 |
| Location: St. Louis, MO, USA |
|
|
|
| Why do you think a 9-10 gr would hurt it? It'll be slower, but I can't imagine it hurting the spring...too light yes, but toO heavy? Don't see any intuitive reason why it would. The slower the projectile, the more arc in the trajectory of course. |
|
_________________
Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 1:01 am |
|
|
| Amigo |
| Veteran Member |
|
|
| Joined: 18 Sep 2008 |
| Posts: 263 |
| Location: U.S. MidWest |
|
|
|
High school physics - objects in movement tend to stay in movement, while objects at rest tend to stay at rest. The greater the object mass, the greater those tendencies.
| Quote: |
redroush00 wrote:
My Ruger seems to shoot 7.0 to 8.5 just fine. Is there any long term issues using 8.5 grains in this gun? I know i shhouldnt shoot the 9-10 grains but what about the 8's? No harm done? |
| Quote: |
Lipoly wrote:Why do you think a 9-10 gr would hurt it? It'll be slower, but I can't imagine it hurting the spring...too light yes, but toO heavy? Don't see any intuitive reason why it would. The slower the projectile, the more arc in the trajectory of course.
|
I have yet to see or hear of a .177 cal. 1000fps air rifle that should not shoot a 9 grain pellet.
However, beyond about 10.0 to 10.5 grains a pellet mass can begin to be adversely subject to the physics laws previously mentioned. This will vary from gun to gun based on the energy absorption ability of the spring, hardness & pitch of the spring, spring to guide fit, total piston assy. weight, transfer port cross-sectional area, gun caliber, pellet-to-breech fit, and the list goes on....
How does any of this apply - heavy pellets hurt spring??
It has to do with piston rebound & hardened steel. Steel springs are hardened and drawn in order to become viable energy storing springs.
As a general rule, Hardened Steel becomes more brittle than Soft Steel.
A second general rule, Hardened Steel Impacting Hardened Steel can cause Fracturing of said Brittle Steel.
When the sear releases the piston, the spring quickly drives the piston to compress the air ahead of it in the compression chamber. Due to inertial friction and static friction, air pressure and flow are slower to build in the transfer port. The heavier the pellet the greater tendency to stay at rest in the breech. The air cushion psi ahead of the piston builds.
Just as we don't dry-fire a spring piston airgun to avoid piston slam, we also try to avoid excessive piston rebound off the said air cushion.
An excessively heavy pellet with a reasonable fit in the barrel breech will require greater pressure to break free and start down the barrel than a pellet of less mass. This means the psi of the air cushion can reach a point that is able to overcome the mass of the piston assy. and strength of the decompressed spring and drive the spring/piston assy. rearward with enough force to violently coil bind the spring, ie. hard steel coils slamming hard steel coils.
Hard Steel violently slamming/impacting Hard Steel - If the spring did not break, it is likely micro fractures were produced. If this is repeated often enough those micro fractures may eventually result in a broken spring - often in multiple pieces. Reading the evidence, is how the professional tuner can determine if airgun failure was due to an excessively heavy pellet for that particular gun or detonation.
If when trying heavier pellets, the airgun recocks it self... the pellet used was either excessively tight or too heavy.
Airgun manufacturers have spent a lot of time and treasure on R & D to develop a product that is likely to perform reliably under a fairly wide range of conditions. However, the consumer can push that range too far.
BTW, detonation/dieseling in the compression chamber can be even worse on the spring than an excessively heavy pellet. The detonation has the potential to cause more violent piston rebound and premature action failure and a burnt seal than a mere heavy pellet. Please note, there is a big difference between detonation/dieseling and combustion.
Slavia:
If I've missed anything please jump in.
Amigo |
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 5:34 am |
|
|
| redroush00 |
| Member |
|
|
| Joined: 31 Dec 2009 |
| Posts: 78 |
|
|
|
|
| Some good info! Thank you!! |
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 11:49 am |
|
|
| rsterne |
| Moderator |
 |
|
| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
|
|
|
| Quote: |
| drive the spring/piston assy. rearward |
This I can see happening, it makes a great deal of sense.... 
| Quote: |
| with enough force to violently coil bind the spring |
I would state that this is impossible, even if the spring was coil bound to start with.... it would imply that energy has been created in the system.... This could only occur through dieseling.... I will admit that it is theoretically possible for a gun to diesel with a heavier pellet when it didn't with a lighter one.... 
This would be equivalent to a pendulum swinging further on the second swing than the first.... or to a ball bouncing to a higher height than it was dropped from.... Without more energy being put into the system, it is IMPOSSIBLE.... Like you said, High School Physics.... 
| Quote: |
| the airgun recocks it self |
You're kidding me, right?.... have you ever seen this happen?....
While there MAY be some reason not to use a heavy pellet in a Springer, this isn't it.... Show me a Springer that recocks itself WITHOUT DIESELING and I'll retract that statement.... 
Bob |
|
_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 12:13 pm |
|
|
| redroush00 |
| Member |
|
|
| Joined: 31 Dec 2009 |
| Posts: 78 |
|
|
|
|
| Quote: |
Show me a Springer that recocks itself WITHOUT DIESELING and I'll retract that statement....
LOL !! Im going to try this! It beats cocking it myself  |
|
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 12:27 pm |
|
|
| Lipoly |
| Veteran Member |
|
|
| Joined: 06 Dec 2009 |
| Posts: 241 |
| Location: St. Louis, MO, USA |
|
|
|
Well, I think rsterne said it better than I could've. The only reason I could think of against heavy pellets is if you used one so incredibly heavy that the effect approached that of piston slam. I just can't imagine that point being anywhere in the range of pellets being made today.
| Quote: |
| Amigo wrote: However, beyond about 10.0 to 10.5 grains a pellet mass can begin to be adversely subject to the physics laws previously mentioned. |
Where did you get this info? |
|
_________________
Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 12:45 pm |
|
|
| rsterne |
| Moderator |
|
|
| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
|
|
|
| Quote: |
| if you used one so incredibly heavy that the effect approached that of piston slam |
I still don't see how the piston could rebound far enough to cock even if you welded the barrel shut.... UNLESS it dieseled, of course....
Bob |
|
_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 1:08 pm |
|
|
| Lipoly |
| Veteran Member |
|
|
| Joined: 06 Dec 2009 |
| Posts: 241 |
| Location: St. Louis, MO, USA |
|
|
|
| rsterne wrote: |
| Quote: |
| if you used one so incredibly heavy that the effect approached that of piston slam |
I still don't see how the piston could rebound far enough to cock even if you welded the barrel shut.... UNLESS it dieseled, of course....
Bob |
I agree, I was just speaking from the standpoint of damaging the rifle, not self-cocking. |
|
_________________
Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 1:56 pm |
|
|
| Amigo |
| Veteran Member |
|
|
| Joined: 18 Sep 2008 |
| Posts: 263 |
| Location: U.S. MidWest |
|
|
|
| Quote: |
Quote:
with enough force to violently coil bind the spring
|
| Quote: |
| I would state that this is impossible, even if the spring was coil bound to start with.... it would imply that energy has been created in the system.... This could only occur through dieseling.... I will admit that it is theoretically possible for a gun to diesel with a heavier pellet when it didn't with a lighter one.... Shocked |
| Quote: |
This would be equivalent to a pendulum swinging further on the second swing than the first.... or to a ball bouncing to a higher height than it was dropped from.... Without more energy being put into the system, it is IMPOSSIBLE.... Like you said, High School Physics.... Rolling Eyes
|
| Quote: |
Quote:
the airgun recocks it self
|
| Quote: |
You're kidding me, right?.... have you ever seen this happen?.... Shocked
While there MAY be some reason not to use a heavy pellet in a Springer, this isn't it.... Show me a Springer that recocks itself WITHOUT DIESELING and I'll retract that statement.... Mr. Green
Bob |
Guys, unless an airgun is operating entirely in is what is known as the "pop-gun" phase some combustion takes place (check Cardew's research). Without the added energy created by combustion, the pendulum analogy would be correct. Even without combustion, some heat is created by compressing the air which also increases the pressure of the air trying to unseat the pellet in the breech.
A heavy pellet can cause a rise in compression chamber pressure above normal. As the pressure increases, the likelihood of detonation, rather than combustion, also increases.
Also, lets remember we are discussing strong sprung, 1000fpm, normally capable, air rifles. As is normally accepted, a weakly sprung air rifle does not produce as high compression chamber pressures thereby reducing the chance of detonation or amount of combustion - all other conditions being equal.
A number of years ago I was researching some aspects of pneumatics as applied to industrial applications and by chance ran across some information published by the Cardews. I found the results of their experiments with airguns fascinating. This is what initially peeked my interest in airguns which lead to it becoming one of my hobbies.
I eventually obtained a copy of their latest book, The Airgun from Trigger to Target and would highly recommend anyone who takes this hobby seriously to get a copy - the information it contains is a real eye opener.
As a tinkerer, I could help but try some of the stuff they did. From the results I got, I can't dispute any of their findings. There is a whole lot more going on in an airgun then one would realize, without studying the engineering aspects.
Lovin this hobby!
Amigo |
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 2:28 pm |
|
|
| Lipoly |
| Veteran Member |
|
|
| Joined: 06 Dec 2009 |
| Posts: 241 |
| Location: St. Louis, MO, USA |
|
|
|
| Amigo wrote: |
...
Guys, unless an airgun is operating entirely in is what is known as the "pop-gun" phase some combustion takes place (check Cardew's research). Without the added energy created by combustion, the pendulum analogy would be correct.
|
Interesting Amigo. I guess it just comes down to how much energy is actually created by the combustion. I'm assuming (key word) it would be minimal or else it would run out of what little fuel is in there after a few shots? After all, you need more than air to produce combustion.
| Amigo wrote: |
Even without combustion, some heat is created by compressing the air which also increases the pressure of the air trying to unseat the pellet in the breech.
|
Well, heat and pressure have a direct relationship. In the case of airguns the heat is produced because pressure increases; heat doesn't then in turn increase pressure or the cycle would continue infinitely.
| Amigo wrote: |
A heavy pellet can cause a rise in compression chamber pressure above normal. As the pressure increases, the likelihood of detonation, rather than combustion, also increases.
|
This makes sense, but I wonder if this comes into play unless you already have some petroleum based lube in the breach.
This also brings up another point...after looking up detonation it appears a difference between combustion and detonation is the fact that a supersonic shock wave is produced by detonation. I wonder if all those people intentionally causing detonation to get their pellet supersonic were just hearing the detonation whilst their pellet traveled subsonic? |
|
_________________
Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 5:18 pm |
|
|
| Amigo |
| Veteran Member |
|
|
| Joined: 18 Sep 2008 |
| Posts: 263 |
| Location: U.S. MidWest |
|
|
|
| Quote: |
Lipoly wrote:
Well, heat and pressure have a direct relationship. In the case of airguns the heat is produced because pressure increases; heat doesn't then in turn increase pressure or the cycle would continue infinitely. |
Two things happen simultaneously, the spring drives the piston to compress the air in a confining chamber. Thus some of the spring energy is converted to heat. As the air temperature rises the heating also serves to increase pressure.
The reason this does not continue infinitely is because of a number of reasons.
First this all happens in a fraction of a second until the pellet becomes dislodged from the breech and starts down the barrel. As the pellet travels down the barrel, the air is allowed to expand dissipating both pressure and temperature.
Second, as the piston rebounds off of the air cushion, further decompression takes place, also reducing temperature.
Third, as more time elapses, some of the heat is absorbed, dissipated and lost by and thru the metal compression chamber, the piston, seal and their surrounding components. If the compression and rebound were to continue, even in an obstructed breech the heat loss would continue. The extent of each rebound would decrease until the cycling eventually played itself out and not continue indefinitely. Even a diesel engine can run out of fuel eventually.
BTW, I don't want to discourage experimentation, but I wouldn't be much of an "amigo" if a guy wanted to try "heavy" pellets and I didn't mention the possibility of a down side.
As Red Green used to say: Were all in this together.
Amigo |
|
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 5:50 pm |
|
|
| Lipoly |
| Veteran Member |
|
|
| Joined: 06 Dec 2009 |
| Posts: 241 |
| Location: St. Louis, MO, USA |
|
|
|
I agree, and appreciate everyone looking out for one another, I just want to make sure I understand this. I'm obviously talking as an armchair physicist, so take all with a dose of salt...
| Amigo wrote: |
Two things happen simultaneously, the spring drives the piston to compress the air in a confining chamber. Thus some of the spring energy is converted to heat. As the air temperature rises the heating also serves to increase pressure.
|
So, you're saying that the heat from the metal spring, which is behind the piston, is able to significantly heat the compressed air in front of the piston? Think of the thermal conductivity required to transfer heat through the spring, past the piston, and then onto air, which a terrible thermal conductor in the amount of time it takes to fire the rifle. In addition, would the spring getting any hotter than 200F? This would be much cooler than the combustion chamber so if anything would serve to cool the compressed air down.
| Amigo wrote: |
The reason this does not continue infinitely is because of a number of reasons.
First this all happens in a fraction of a second...
|
I read your previous post to say that the heat created by the compressed air itself further acted upon the air to increase pressure. If this were the case, then we'd all spontaneously combust since even at 1 Bar (or anything else above a vacuum) the two elements would feed each other infinitely. If that was not what you were saying (as it seems you were referring to heat from the spring making its way up to the compression chamber), then I'd say we agree.
| Amigo wrote: |
Even a diesel engine can run out of fuel eventually.
|
Can't say I'd argue w/that  |
|
_________________
Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
|
|
|
|
|
| | | | | | | | |
| | | | | | | | | | | | | | |
| Posted: Fri Jan 08, 2010 7:02 pm |
|
|
| Amigo |
| Veteran Member |
|
|
| Joined: 18 Sep 2008 |
| Posts: 263 |
| Location: U.S. MidWest |
|
|
|
| Quote: |
Likkpoly wrote:
So, you're saying that the heat from the metal spring, which is behind the piston, is able to significantly heat the compressed air in front of the piston? Think of the thermal conductivity required to transfer heat through the spring, past the piston, and then onto air, which a terrible thermal conductor in the amount of time it takes to fire the rifle. In addition, would the spring getting any hotter than 200F? This would be much cooler than the combustion chamber so if anything would serve to cool the compressed air down. |
Amigo wrote:
Two things happen simultaneously, the spring drives the piston to compress the air in a confining chamber. Thus some of the spring energy is converted to heat. As the air temperature rises the heating also serves to increase pressure.
Lipoly:
That portion of your quote, in bold, above specifically, is entirely incorrect. Please carefully reread my quote immediately above and please note that nothing was said about heat in the spring. The cocked spring serves as a reservior of stored energy derived from the shooter when he or she compresses it to the "cocked" position.
I'll rearrange the sentence above to, hopefully make it more clear:
The spring drives the piston to compress the air, thus some of the spring energy is converted to heat. (As represent by the rise in temperature of the compressed air).
BTW, the last two sentences of your quote re: thermal conductivity, 200F etc., are BS, designed to cloud the issue, and I think you know it.
Adios,
Amigo |
|
|
|
|
|
|
| | | | | | | | |
Note: If you are seeing "Please enter your username and password to log in." Your browser cookies have been reset
or you need to register to access the topic in question. Use the 'Register' button near the top left of this page.
|
