roger (Login bhawanna) from IP address 167.7.16.100
ok, here goes another question about proper pellet weight.....the only reason i'm making this post is because of conflicting opinions which is confusing for a beginner like me......on one airgun forum they say not to shoot anything in .22 cal. heavier than 16gr or it will cause spring fatigue and eventually failure but reading post on here from the "masters", they are talking about using 18gr and higher pellets in a 350mag. i want the most kick-butt ammo i can use but not at the expense of having to rebuild the gun every 2000 rounds for spring failure.....the gun has a cdt tune............please advise.
You say the gun is tuned, therefore should be running at near it's best. With this in mind, a possible loss or gain of 1 ftlb either way is unimportant if you can't place the pellet exactlly in the Kill Zone or Bullseye, right? A heavyweight "Miss" is worthless to the shooter...
You didn't say if the gun was broken-in yet?
That usually takes 800 to 2K shots to bed things in and allow parts to stabiize with eachoter. Just shoot the heck out of a new or newly tuned gun to accomplish this! Without wearing it in, your accuracy will vary and you honestlly can't evaluate pellets for your rifle. Many times a tuned rifle will shoot a light pellet faster thus giving high energy reads and still not abusing the gun's internals. There's a lot of variables and shooying the gun a LOT brings them to the surface.
The Shoot-in serves 2 purposes. it breaks the gun in and it breaks YOU in to the airgun!
Buy about 8 widely varied types and brands of GOOD pellets and spend time and lead determinining your group sizes at 20 to 75 yards. (I assume this is s "Hunting rifle?) The results should indicate which isbetter to use in your rifle. Take the best of the best and re-do the test carefully.
You have your work cut out for you and in the end, you'll be able to answer your own queston!
Hey Roger, Tim here!! What gun are Ya talkin about Bud?? The 54?? The 350?? Did you decide to go back to the 22 Cal. Brl. on the 350????? Did you get the 54 back from CDT already?? What you have not said here that is important is the 350 you have that I/we Chopped & recrowned the brls. on was originally a 22 cal.,, we swapped it to the 177 Brl. From what I have gathered from the research I have done (Advice from Curtis, Hector, & others) that is ok to "downsize"?? Man you were hitting plastic golf balls at 45 yrds. with the 177/350 Mag. at the last fun shoot. Did you re install the 22 Brl.?? Of course it may be better if Ya just call me, we have not talked for quite some time, what has it been now, 3 days??LOL!! Sorry I am of no help to you my Buddy,, what gun?? What cal.?? Im shure the "Big Boys" are asking themselves the same questions before they respond!! Now that I have "ticked" you off,, I shure you will call me monyana!! Your Buddy,, Chopper Tim.!!
ok here's a little more info. i am shooting a 350 mag. .177 chopped to 16 inches by "tim da chopper". i have shot cp 7.9, jsb 8.44, and beeman crow mags 8.8 in it. i can't see any noticeable difference in groupings at 35 yards. i zero my scope at 35 yards. i am holding patterns within 1" at this yardage with all these pellets. my question is; how heavy a pellet can i use before i need to worry about spring fatigue or failure? is it ok to shoot cp heavies 10.5g in this tuned gun without damaging the spring?
Read what ZVP wrote. I used to use cph in my .177 Mod. 48,very accurate but two broken springs later at about 1500 rounds each I started using a lighter pellet.Beeman Ram Jets,almost as good and no spring breaks since. Remember a hit is good,be it paper or vermin,a miss is useless.
Gary
ps: I am always testing pellets new to my guns.
Hector J Medina G (Login HectorMedina) 189.182.30.13
Heavy and Light are relative terms
June 25 2008, 3:48 PM
Roger;
Don't take me wrong, but I've written about this a couple of times and I think that probably a more thorough understanding of the process is important:
Read it in full and see the video that is referenced there.
Now, think about the following:
Metal breaks through fatigue. IE, a piece does a certain job by bending and straightening (work cycle) a number of times till it work hardens and then breaks. If you have ever seen the end of a broken spring with a magnifying glass, you will have noticed the very peculiar crystalline structure of the steel. A very good description of the "phases" of the steel was posted by J in the string about barrels and barrel forging/swageing:
You may need to read more about Austenite temperature and Martensitic lattices and transformations when temperature is not the agent of change, but the main message here is that working hardens the metal and further working breaks it. Much like bending a piece of steel wire backwards and forwards till it breaks. Metal clips, for example, do not generally allow more than 4-5 cycles, just to pose one extreme on the low end...
If you look at the video that I posted above, you see that on a freely distending spring, there are "travelling waves", the oscillations that go back and forth in the spring even when the spring is already fully distended. This means that in a freely distending spring for each shot cycle there are 4 or 5 work cycles, as the spring will oscillate back and forth a few times.
If you can picture in your mind the image of the spring when a VERY heavy pellet is being fired, it should be something like this:
The piston accelerates under spring force till the weight of the pellet stops it, then the spring recoils, but the pellet starts to move, so the spring distends again and moves forward, but the weight of the piston stops it again, this happens again and again till finally the pellet exits the barrel and the piston is finally free to allow the spring to distend fully. In all, due to travelling waves, this ONE SHOT cycle represented TWENTY SPRING cycles. No wonder springs break under that treatment!
THIS is what breaks a spring.
In Uniform Harmonic Movement, there are three conditions: overdamped, underdamped and critically damped. In the underdamped case, the total transfer of energy is not maximum because the little damping makes the spring oscillate back and forth and therefore the energy is delivered to the object, but then taken back from it. In the overdamped case, the spring is prevented from delivering all the energy to the object because the object is already in motion when the spring tries to impart an additional impulse, so only a marginal fraction of the energy is trully transmitted to the object. What we all aim at is a critically damped system, where the spring imparts MAXIMUM energy to the object, therefore making the SYSTEM itself absorb LITTLE energy.
Is that clear? because this is the HEART of the matter, let me repeat it: You want the system to impart to the pellet Maximum energy so that the system itself absorbs little energy and does not destroy itself.
This is critical. You really need to understand this, if it is obscure or unintelligible, ask. It really is paramount, I do not care if I have to explain it a dozen times, it is truly important.
Once we have come to the proper conclusion, we realize that what we need is for the spring to distend and STAY there. We have two ways of doing that:
1.- Make a spring guide that seriously dampens the spring.
2.- Achieve a balance between pellet weight, piston weight, transfer port size, spring guide friction, washers/spacers AND spring. Notice that the ONLY energy producing element in the equation is the spring. All the others are passive elements and most are dampening elements (except for the washers/spacers).
I have often wrote this and it is often the case that simple assertions are hard to digest, so here it goes again:
"Usually, when a spring gun yields maximum energy, you have found the sweet spot of the system, once that is found, you need to look at pellets that are close in weight in order to find the one that shoots the most accurate, THAT is what Chronos are for"
SO, do not get hung up on 7, or 8 or 9 or 10 or even 15 grains pellet weight in 0.177" caliber.
TEST several pellet weights and MEASURE MV, then CALCULATE M.Energy. Look at how the gun behaves, READ your gun, each one is different. Then research some more in the direction the gun TELLS you to go.
The signs are there, we just need to learn how to read them.
As a rule of thumb: Heavy pistons go with heavy pellets. Light pistons go with light pellets.
IF you have a peculiar barrel that for some arcane reason likes heavy pellets (an anomaly, but something that is detectable when the accuracy is phenomenal with abnormally low energy levels) then you need to TUNE the gun to the pellet by weighting up the piston or machining a heavy piston from scratch.
If you find the converse anomaly (Phenomenal accuracy with ultralight pellets but still abnormally low energy levels), then you need to swiss-cheese the piston, or button it, or somehow tune the gun to the pellet the barrel likes.
For FACTORY spec guns, it is generally accepted that 8.5 grains or thereabouts is the logical mid-point. 10 grains is heavy and 7 grains is light. But those are, again, relative terms. For the sake of illustration, think of the JSB line: Express at 7.9 grains, Exacts at 8.44 grains, Heavies at 10.2 gains.
Hope I did not make it even more confusing, really, if you want further clarification in any aspect, post here.
Experiment and post your results here, it's the only way we can all learn.
Tim here! Thanks my Friend for your recent E-Mails,, as a "newbie" with only a couple of years devoted to learning all I can about airguns & a pasion Im shure is second to none, I am truly honered you have chosen me from the "masses" to corespond with. Thank You. Now,, on to buisness!! I just got off the phone with my Buddy Roger,, we both are perplexed by the idea that CPH (10.5) gr. pells. would be detramental to the health of our guns. I know, I have read MANY posts about it in the last 3 years. Just yesterday I was shooting my new Panther, I was almost out of CPHP,s (7.9 gr.) So I decided to try some Kodiaks & CP heavys,,(both around 10.5 gr. I think?) POI shifted slightly low left (about 3/8") But,, my groups were all touching at 25 yrds!!! I guess like my mom said when I was a little boy: If you keep looking at those "naked lady magazines" you are going to go blind! My responce?? Well,, cant I just keep it up untill I need glasses??LOL!! Ok, so I do understand the relavence of a "balanced" piston in relation to a particular pellet weight,, but man in the meantime,, those "Heavys" shure do shoot NICE in my 34 & 350!! Just funnin Hector,, today I went to Wal Mart & got me 2000 rounds of CPHP,s!!! If you get time,, check out "Hunting Gate" at the GTA forum Buddy, there you will see what my "Chopper" (Diana 350 Mag. in 177 shooting 7.9 CPHP,s @ 1040 fps. does to a BIG Raccoon!!) (This Racoon was coming out during Daylight hours,raiding my trash cans,& in an obvious state of serious health issues, including possible rabies) Im gonna stick with CPHP,s @ 7.9 gr. for now,, but,, I was seriously impressed yesterday by the groups I shot with the 10.5 heavys?? I already need reading glasses, I guess I dont need to be shooting "Heavys"!!! LOL!! Hope all is well Hector,, Tim. Big Ole Un Abrazo to you Buddy!!
hector,
thanx for the reply and the illistration. i understand the metallurgical attributes of spring steel and agree totally with your reply. but won't heavier load bearing(heavier pellets) increase martensitic lattices hardening for premature failure? however for argument's sake, the video shows a freely distending spring. at any given time in an airgun is the spring freely distending?....if so, then why is there preload on spring and a compressor is needed to assemble? i am not disputing your reply, only trying to educate myself by asking questions. you're a walking/breathing encyclopedia on the physics of this hobby and i thank you for sharing your masterful knowledge.
Spring temper, finished wire diameter play big parts.
June 25 2008, 9:01 PM
Annealed wire is coil wound and harden prepared with processes unique to the application. Afterwards the temper is imparted so the martensite is stronger and more ductile.
The big problem with 'mass produced' springs is uniformity. The temperature should be high enough to austenize while being low enough to reduce formations of bainite or pearlite which are brittle and can shatter like glass does.
The thicker the wire cross section is, the better likelihood that there is enough ductile material present to reduce the problems associated with brittle wire, but the rub is compressibility decreases as wire diameter increases. At a certain point, the spring wire is to thick and the mechanical advantage fails. {Bent barrel, busted linkage, sear catch, etc}
The 'liquid' properties of solidified metal with the crystal structures formed {like the way ice or glass forms} creates a possibility of fracture along the line of the grain. Using some method of precipitation hardening can help to a certain extent, however this is a rather time consuming and costly type of process. This is why an ARH spring is more costly and durable than a mass produced Mayer & Grammelspacher spring. In over six years, I've never broken an ARH spring. Currently do have several broken, kinked or 'short set' Diana springs, some of which were NIB never used . . .
A thicker, tougher spring as well as the heavier piston and longer stroke properties Mr Medina pointed out, gives higher possibility that a heavy pellet can work well ~ although the specific individual characteristics of the entire system should be given considerations. An example would be a break barrel with a harsh shot cycle causing the barrel to 'flick' off of the lock with a heavy pellet, functions very smoothly with a midweight pellet but smacks forward with a lighter pellet. Transfer port, barrel lead in, seal friction, piston size / weight, spring size / weight, guide size / length, can and do vary any part of the example listed, so when one is altered the exploration process may just begin all over.
Let's say that the heavier pellet "tires" the spring 20% faster, that is nowhere near the 2X, 3X, 4X times a too loose guide will.
Also, the guide cannot be full length , half of the spring is free to recoil and re-recoil and re-re-recoil. So usually, springs break around the mid part, which is the section where the guide stops guiding the spring.
Also, a common trick in dimensioning guides is that springs increase in diameter a little when compressed, so guides can be "tight" when the spring is distended, but will loosen a little when the spring is compressed.
I am nowhere near as well versed as others here but I would like to interject my own observations.
Maybe I can offer something to this subject.
I have found that the acceptable pellet weight is determined by many factors as others have eluded to.
Generally speaking, it seems that the harder the pellet is to move from it's seated position in the breach, the lighter or smaller in diameter the pellet should be. The pellet could be difficult to unseat due to a small transfer port or a tight fit in the breach/barrel to name a few examples. This effects the spring because the air trapped between the piston and pellet is what determines the "bounce" and therefore the spring fatigue. On the other hand, if the resistance is low for whatever reason (oversized transfer port, loose pellet fit, too light a pellet) then the cushion of air is compromised and the piston can slam into the end of the chamber.
This explains why each gun has preferences when it comes to pellet styles and brands but also weight.
This seems to be exagerated in the Chinese guns due to the substandard QC and varying tollerances. An oversized breach or transfer port will favor a larger diameter or heavier pellet due to the added resistance it offers.
Since I can't see the spring's actions, technicly measure port effectiveness, etc. Does all this boil down to the most accuate is the best / right pellet?
Is the fastest the best / right pellet?
Is the most consistant in FPS the best / right pellet?
Off hand, I'm thinking any of the above could be missleading.
So how does the layperson going by the seat of his pants without any sophisticated measuring eguipment determine the best and safest pellet for a particular gun?
I know shape's design, weight, hardness, fit, etc. must be involved, but to what degree? I'm thinking for accuacy, it's kind of a balancing act and may be made to shoot well with pellets not so compatable for spring life. Especially in a tuned (unknown kit installed type?) gun.
Sorry, seems the more I learn,,,, the less I know. (S)
All the by golly & by guess has me thinking if I'm doing damage.
I have 2 "tuned" rifles now. Both appear better, are smoother, sound more solid. One I got a print-out of FPS and such. But I've no clue as to what (if any) changes were made to the strength of the power plant. I'd like to try some heavies but an afraid of the possible damages I may inadvertantly do.
Right now I'm a tad bit on what is considered heavy. Also they both seem to be responding to the heavier pellets with accuacy, hold sensitivity, consistancy of speed (not highest speed), and a solid firing cycle sound.
Should I dare go heavier?
Somehow I missed your response to me on this thread Buddy,, Sorry! Yes, alot of questions from myself & others pertaining to "heavy" pellets! Im really thinking about adding some weight to the piston on my 350 (177 cal.), as it LOVES Kodiaks & CP Heavys. Afterall,, it shoots CP Hollow Points @ 1040-1050 fps. & we know that is acording to most (From my research) way too fast & will most likely "lead" the Brl. in short order, reducing accuracy. Not so shure if that is a good idea on my 35 Panther, Dont know if it has enough "Umph"?? (Although it shure groups well with them) Of course if I break a spring,, thanks to Warren & John in PA I have a nice stash of J.M. springs, guides, & tophats!!LOL!! Thanks Hector,, & to all my Friends here that help us all SO MUCH!! Un Abrazo,, Tim.
