GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => German AirGun Gate => Topic started by: Oldgringo on June 18, 2019, 10:31:04 PM
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Average velocities recorded on 10/11/17:
HW30S-1 670 fps
HW30S-2 629fps
R7 648 fps
Average velocities recorded on 6/18/19:
HW30S-1 ~562 fps
HW30S-2 ~590 fps
R7 ~625 fps
Today's temp was 90° and AA 7.33 gr. Field Diabolos are always used in these, DIY lube tuned with JM kits, rifles. Other than temperature, what could cause these somewhat uniform drops in the velocities of three separate rifles? BTW, Today, I used two different chronographs, with new batteries, and both reported pretty much the same readings. The chronographs were placed in full sunlight some 6 feet from the muzzles. They may have been three feet closer in the original readings???
My backyard shooting is limited to 30 yards and the 1/2" group accuracy is still there but where did the velocity go?
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The first time I chronied my 430L I did it at ten feet and the velocities were way low and I thought I had a broken spring in a new gun.
Some one on here told me to move with in one foot of the muzzle and try again. Velocities did increase and I did get close to what AoA did when they checked it out before shipping.
You may want to try it again with the chrony set up closer to the rifle muzzle.
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Were the light conditions the same for your first test?
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Greg,
Were the earlier/higher velocities recorded with fresh, new springs? New springs tend to take a set and weaken somewhat over time. Have you noticed a decrease in the amount of spring pre-load?
AR
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I use 12” from chrony as a standard setup for all velocity testing. The distance from chrony will definitely effect the readings. I would run the test again using the same distance that you used for the first test ( three feet). My guess is that you will come close to duplicating the first readings.
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Average velocities recorded on 10/11/17:
HW30S-1 670 fps
HW30S-2 629fps
R7 648 fps
Average velocities recorded on 6/18/19:
HW30S-1 ~562 fps
HW30S-2 ~590 fps
R7 ~625 fps
Today's temp was 90° and AA 7.33 gr. Field Diabolos are always used in these, DIY lube tuned with JM kits, rifles. Other than temperature, what could cause these somewhat uniform drops in the velocities of three separate rifles? BTW, Today, I used two different chronographs, with new batteries, and both reported pretty much the same readings. The chronographs were placed in full sunlight some 6 feet from the muzzles. They may have been three feet closer in the original readings???
My backyard shooting is limited to 30 yards and the 1/2" group accuracy is still there but where did the velocity go?
Although most of the posts in reply to your question are regarding the distance from the chronograph for your tests. I would think you are using the same distances for all your tests.
Although you said not to take temperature into account, I think you must. Warmer air is less dense, as all air plane pilots know. Also, do you have any idea what the barometric pressure was during both of these tests? That can also affect the density of the air.
I am probably wrong, and I am no expert on any of this, but it is something to think about. Other than that, do you leave your springers cocked for long periods of time? It doesn't affect a gas piston rifle, but does affect steel springers.
In any case, good luck finding out the cause and I will just slink back into the shadows now... (grin)
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IMO, I think this, that's a lot of velocity loss!!! I'm to throw this out there, 1 it could be the lighting on the chrony or distance, if not check ur extreme spread? if its big? u may have a seal issue, it could be the spring? if its broken you'd probably feel it in the cocking stroke! I would also check ur pellet fit! I'm sure ur using a different tin by now LOL!!! but all in all if its not the lighting on the chrony u got something going on! ???
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IMO, I think this, that's a lot of velocity loss!!! I'm to throw this out there, 1 it could be the lighting on the chrony or distance, if not check ur extreme spread? if its big? u may have a seal issue, it could be the spring? if its broken you'd probably feel it in the cocking stroke! I would also check ur pellet fit! I'm sure ur using a different tin by now LOL!!! but all in all if its not the lighting on the chrony u got something going on! ???
My first thought was broken spring but how likely are three broken springs or bad seals at the same time? No, the guns do not stay cocked for any longer than it takes to shoot them. It is indeed a mystery. Oh well, tomorrow is another day. Scarlett O'Hara said that.
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IMO, I think this, that's a lot of velocity loss!!! I'm to throw this out there, 1 it could be the lighting on the chrony or distance, if not check ur extreme spread? if its big? u may have a seal issue, it could be the spring? if its broken you'd probably feel it in the cocking stroke! I would also check ur pellet fit! I'm sure ur using a different tin by now LOL!!! but all in all if its not the lighting on the chrony u got something going on! ???
My first thought was broken spring but how likely are three broken springs or bad seals at the same time? No, the guns do not stay cocked for any longer than it takes to shoot them. It is indeed a mystery. Oh well, tomorrow is another day. Scarlett O'Hara said that.
That is why I thought the temperature/barometric pressure variant may be the answer. Anyway, I hope you figure it out and I will be interested in what you find out when you do figure it out.
Sorry I was not of more help to you.
Kerry
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IMO, I think this, that's a lot of velocity loss!!! I'm to throw this out there, 1 it could be the lighting on the chrony or distance, if not check ur extreme spread? if its big? u may have a seal issue, it could be the spring? if its broken you'd probably feel it in the cocking stroke! I would also check ur pellet fit! I'm sure ur using a different tin by now LOL!!! but all in all if its not the lighting on the chrony u got something going on! ???
I agree something going on!
The FPS on the HW30s-1 is over 100 FPS less than the original test. While the other two guns are less than 50 FPS. I can see a 50fps spread due to setup but not 100!
But I would still setup the chrony to the original parameters and see what I got before I did anything more. It will be interesting to see the results!!
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Thanks for the comments, guys. I went back out this morning between 0715 and 0745 with consistent light, 70° temp and the Caldwell Chrony ~1 foot from the muzzle.
HW30S-1: 597 fps, S = 2, SD = 0.89
HW30S-2: 617 fps, S = 28, SD = 9.15
R7: 638 fps, S = 19, SD = 6.51
I think I'll find something else to worry about; after all, these are not Anshutz target rifles.
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Thanks for the comments, guys. I went back out this morning between 0715 and 0745 with consistent light, 70° temp and the Caldwell Chrony ~1 foot from the muzzle.
HW30S-1: 597 fps, S = 2, SD = 0.89
HW30S-2: 617 fps, S = 28, SD = 9.15
R7: 638 fps, S = 19, SD = 6.51
I think I'll find something else to worry about; after all, these are not Anshutz target rifles.
Are you absolutely certain you were using the pellets in each test that you think you were using?
I only ask, because I have accidentally put 7.9 grain pellets in my Nova Freedom when I thought I was putting in 10.5 grain pellets.
It can happen... I know, because I have done it. :o ;D
Actually, I did have one tin of pellets that got mixed between the two. Took me a long time to sort them out... ??? ::)
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Thanks for the comments, guys. I went back out this morning between 0715 and 0745 with consistent light, 70° temp and the Caldwell Chrony ~1 foot from the muzzle.
HW30S-1: 597 fps, S = 2, SD = 0.89
HW30S-2: 617 fps, S = 28, SD = 9.15
R7: 638 fps, S = 19, SD = 6.51
I think I'll find something else to worry about; after all, these are not Anshutz target rifles.
The HW30S-1 is still 70+ FPS lower than the first test. May be a weak spring? The other two are very close.
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Sometimes this happens when u tune, if u haven't done it a lot and know from trial and error? sometimes we get to much lube on the piston seal, or the tube wasn't completely cleaned out before we started putting it all back together, and if any excess lube get past or in front of the piston seal or was already there to begin with? it will give u a false reading on ur chrony results, and as the lube burns off ur numbers drop off, this may or not be the case, springs after breakin some times lose as much as 20fps, this where piston seal fit is critical! if its just a tic tight it will lose power in most cases, but as the seal breaks in some velocity will return, remember HW30's R7's are not cannons and most spring kits are built for OEM power! which is where ur guns are shooting at! their are other factors that could be at play, like and out of round compression tube! things like this will rob u of power! not saying this is the case but always a thought in my mind! just some food for thought ;D
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Average velocities recorded on 10/11/17:
HW30S-1 670 fps
HW30S-2 629fps
R7 648 fps
Average velocities recorded on 6/18/19:
HW30S-1 ~562 fps
HW30S-2 ~590 fps
R7 ~625 fps
Today's temp was 90° and AA 7.33 gr. Field Diabolos are always used in these, DIY lube tuned with JM kits, rifles. Other than temperature, what could cause these somewhat uniform drops in the velocities of three separate rifles? BTW, Today, I used two different chronographs, with new batteries, and both reported pretty much the same readings. The chronographs were placed in full sunlight some 6 feet from the muzzles. They may have been three feet closer in the original readings???
My backyard shooting is limited to 30 yards and the 1/2" group accuracy is still there but where did the velocity go?
Were you using "dinosaur oil based grease" in the gun (factory or otherwise) for the initial chrony test? If so, perhaps there was some initial dieseling which boosted the velocity or the lube thickened with (become gummy) due to "out gassing".
When I first moved to NC I was using "molly tar" for spring lubing and the stuff in a sealed tub thickened enough over the years to support a socket head cap screw on the edge of the tub with only 1/2 of six threads embedded like this..........
(https://i.imgur.com/Q2gK841l.jpg)(https://i.imgur.com/49r76NWl.jpg)
Also, here is a pic of the factory lubing of a Beeman R9 I worked on after use so perhaps the lube has become "gummy".............
(https://i.imgur.com/FiUT3hjl.jpg)
Compare the above with this HW95 piston with "HW lube" straight from the box..............
(https://i.imgur.com/9QHYK4il.jpg)
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The experience I had with the heavy tar in my first R9, the velocity never dropped, but sounded more twangy when the stuff started to dry up. This was with the hornet kit. If your using the same tin of pellets, I would try a different tin. When the 7.3's went from the red tape to the white tape holding the lids, I noticed a difference with the pellets. Head sizes can do velocity changes also,
Jason
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Average velocities recorded on 10/11/17:
HW30S-1 670 fps
HW30S-2 629fps
R7 648 fps
Average velocities recorded on 6/18/19:
HW30S-1 ~562 fps
HW30S-2 ~590 fps
R7 ~625 fps
Greg, your experiencing the "Beauty" of Springer's. There's ALWAYS adjustments to be made ;)
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I'm going to also add this, I purchased an R7 many many yrs ago, out of the box with all the factory goop still in the gun and un touched, I ran it across the chrony, with 7.9gn cphp's, it aved 550fps, I can assure after the lube from the factory once it burned off the velocity would have dropped off probably to around 525fps or more! I don't know because I sent the rifle back because some one had opened the shipping box before I got it from UPS and the stock had a nice scratch on it! A new gun $350 bucks with a scratch MMM! not me!!! but if I had kept that rifle and added A JM spring kit and it had pushed up the power to 600fps or more I would have been happy with that! I noticed 2 of ur rifles have ES that IMO are a tic high? which tells me something not quite right, most decent home tunes if done correctly ur ES is capable of 10fps or less after breakin, my rifles usually run around 5fps or less, SD's of 1 to 2fps or less, MY HW50 in .22cal for example it shoots 14.66gn H&N FTT's @ 600 to 605fps ave with those pellets, I recently decided to try another pellet in this rifle, I tried some RWS Super H Points, 14.2gn, it shoots them @ 625fps ave, my ES did not change still 5fps, these pellets do not fit the bore as tight as the FTT's which are 5.53mm and their just as accurate from my rifle! My 50 has probably less then 2 tins down the pipe! just giving u some examples ;)
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Sometimes this happens when u tune, if u haven't done it a lot and know from trial and error? sometimes we get to much lube on the piston seal, or the tube wasn't completely cleaned out before we started putting it all back together, and if any excess lube get past or in front of the piston seal or was already there to begin with? it will give u a false reading on ur chrony results, and as the lube burns off ur numbers drop off, this may or not be the case, springs after breakin some times lose as much as 20fps, this where piston seal fit is critical! if its just a tic tight it will lose power in most cases, but as the seal breaks in some velocity will return, remember HW30's R7's are not cannons and most spring kits are built for OEM power! which is where ur guns are shooting at! their are other factors that could be at play, like and out of round compression tube! things like this will rob u of power! not saying this is the case but always a thought in my mind! just some food for thought ;D
Great thinking and a very distinct possibility with respect to lube migration into the compression chamber on the first test!
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I used the tar that came with the JM kit. Is that a no-no or did I overuse it?
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SOP: check both the breech seal and piston seal. Possibly a nick in the seals?
Otherwise send them to MotorHead to figure out! ;)
-Y
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When I apply tar on a spring its usually in the center 5 to 6 coils where the spring is at its weak point or unsupported state, after the piston and guide have separated, this is usually where vibration or buzz will occur, properly fitted guides usually do not require heavy amounts of tar or other lubes of choice, any other lubing on the spring beyond the center should be a film state of lube, its just there to help with friction from metal to metal contact, if to much lube is used on ur spring u risk the lube to migrate to places u don't want it to go! to much lube on ur spring in certain states of air temperature can cause the velocity to slow down, usually colder weather, if lube has gotten past ur piston seal in hotter temps u can usually smell something or have detonation or dieseling, applying lubes properly is trial and error, each gun is also different, but once u have done it enough u know how and where the proper lubes need to be applied ;D
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I used the tar that came with the JM kit. Is that a no-no or did I overuse it?
Opinions will very on what the best lube is but I don’t think that is the issue. My thinking is that did you chrony the HW30S-1 to soon after you tuned it and maybe had to much lube on the seal causing a little dieseling on the first test giving you a higher velocity reading? I myself will not chrony a newly tuned gun until I have at least 50-100 shots thru it with no signs of dieseling. This way I can get an accurate base line.
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agreed, this why I test fire them for function and accuracy then tear them down to clean them out so I can properly fix them!!!! ;)
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Do the guns normally stay inside the house or at school? Had they had a chance to alcomate to the outside temperature? I've got one rifle that will give me lower velocity as soon as I take it outside ... outside temperatures about 90, inside temperature 68 to 72
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Actually 90deg temps should help with higher velocities in a spring gun! but I agree with acclimation before shooting! ;D
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Actually 90deg temps should help with higher velocities in a spring gun! but I agree with acclimation before shooting! ;D
That would seem to be the case.
In the past I had issues with "temp related poi shifting", At a spring field target match in Virginia both my brother and I had a 1" poi shift at only 20 yards with our .177 R9s after zeroing during snow flurries and the temp rising to upper 50s by match end. We were was using traditional molly paste and tar for lubing so I started messing with oring sealed piston caps at that time to minimize the amount of lube and "rubber" sliding against the receiver. I thought that perhaps the lube viscosity and the "rubber" durometer was changing. The change to an oring seal and minimal lubes definitely gave improved poi stability so I've been using oring sealed piston caps ever since.
After moving to NC about 12 years ago I "discovered" non-dieseling Dupont Krytox "space station lube" and have been using the stuff ever since. After the move from West Virginia to North Carolina I tested "temperature related velocity changes" years ago (during a NC winter month) with oring piston seal plus Krytox lube. The velocity was tested at mid 20s and mid 70s and the velocity for the "mid 20s" was 10ish fps HIGHER than "mid 70s". My only unscientific reasoning was that cold air is denser than warm air so there was "heavier air" being compressed at the "mid 20s". Anywhoo.....10ish fps variation is insignificant for my shooting (I don't shoot my springers at mid 20s :o) so there have been no other low/high temp velocity tests of oring seals and Krytox lubes since.
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I found my notes from 9/4/16 and I did not transpose numbers. Those original readings were with the JM kit AND seal. So I reckon I'll take her down and see whats to see. I wonder if the R7 and HW30 use the same piston seal, anybody know? I have the OEM springs for both 30S' and the R7 and they are three different lengths by just a little.
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Yes Greg their the same piston and breech seal! ;D I have been using Air seals Australia piston seals in my HW's and really like them! ;)
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I've taken her down and cleaned up her innards. There's nothing wrong with the mainspring or either seal that I could see and/or feel. That may have been the first one I DIY tuned. It was gummy with JM's heavy tar but - it's not anymore.
Now I have another problem. The little bitty screw that holds in her innards broke during reassembly.. It's part no. 541 on PA's schematic. I wonder where one might find a replacement?
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I've taken her down and cleaned up her innards. There's nothing wrong with the mainspring or either seal that I could see and/or feel. That may have been the first one I DIY tuned. It was gummy with JM's heavy tar but - it's not anymore.
Now I have another problem. The little bitty screw that holds in her innards broke during reassembly.. It's part no. 541 on PA's schematic. I wonder where one might find a replacement?
Wonder of all beholders, our local Tru Value had the screw! The gun is back together all degreased and clean. I reckon the spring is just tired, she's still shooting 7.33 gr. AA Field Diabolos at 600 fps. So, I'm not gonna' fret about it no more.
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I would say ull probably find 1 at some hard ware store or a place that sell fasteners, I would use a grub screw with a allen head ;)
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I tried a couple of shots yesterday and she's still at ~600 fps with the 7.33 gr. AA. If I pull the JM spring and see what she does with an OEM spring and the velocity comes back up, that confirms that the JM spring is tired. I reckon I can then take the top hat and guide from the JM spring and insert them into the OEM spring, can't I?
OTOH, the rifle has peep sights and I don't shoot her any further than 30 yards, just don't worry about it.
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well u know u can probably space up the JM spring with some Delrin washers and get more power out on it! just my thinking! ;D
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I tried a couple of shots yesterday and she's still at ~600 fps with the 7.33 gr. AA. If I pull the JM spring and see what she does with an OEM spring and the velocity comes back up, that confirms that the JM spring is tired. I reckon I can then take the top hat and guide from the JM spring and insert them into the OEM spring, can't I?
OTOH, the rifle has peep sights and I don't shoot her any further than 30 yards, just don't worry about it.
"JM spring is tired"
I guess it's possible (especially if "heavies are shot") but my experience over the years is that the JM springs I've used hold their temper till the spring breaks after 10s of thousands of shots. Decades ago I bought a Maccari "soft spring kit" for my Beeman R10 after the factory spring broke and kept track of the shot count and velocity. The R10 started with a 7.9 grain pellets 910fps mv. After a couple years and 20,000 shots, determined by counting empty Beeman Trophy tins, the pellets were still clocking 905fps (more variation can come with atmospheric changes). Because of that spring I've been only using Maccari springs for my kits except for the two Vortex springs I tried after moving to North Carolina which sagged with less than a case of CPLs. LOL....the early Vortek PG2 kit (didn't have closed spring ends) lost 80fps mv shooting less than a case of CPLs (roughly 4500 shots). A few years later I bought a bare Vortex spring for my R9 and it also sagged after 2500 shots losing 30fps in less than two months.
As was mentioned by Mark, perhaps there is enough "free space" to add a couple washers to increase the spring preload and restore some of the velocity.
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Thanks, Mark and NCED. Washers are certainly a thought. The plot thickens, what is the real cause of velocity loss and does it matter? This is a nice little open sighted air rifle that is used for plinking in our 30-yard deep backyard....and taking an occasional Brown-Headed Cowbird off of the bird feeder.
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Thanks, Mark and NCED. Washers are certainly a thought. The plot thickens, what is the real cause of velocity loss and does it matter? This is a nice little open sighted air rifle that is used for plinking in our 30-yard deep backyard....and taking an occasional Brown-Headed Cowbird off of the bird feeder.
I think I agree with you. As long as the velocity doesn't keep dropping off and it is doing the job you need it to do... why worry or fuss with it? ;)
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Thanks, Mark and NCED. Washers are certainly a thought. The plot thickens, what is the real cause of velocity loss and does it matter? This is a nice little open sighted air rifle that is used for plinking in our 30-yard deep backyard....and taking an occasional Brown-Headed Cowbird off of the bird feeder.
Hummm.......I also take out cow birds on my bird feeder!
Velocity degradation can come from multiple sources such as a sagged/broken spring, thickened lubes (especially with low powered springers), bad piston seals so on and so forth. IMHO, only a teardown and inspection can determine the cause.
Does the velocity reduction matter you ask. Only if it negatively affects your shooting. LOL, when I received my .177 HW95 I deliberately detuned the gun straight from the box to reduce the CPL velocity from 880fps to 850ishfps. This velocity reduction makes the HW95 easier to control, yet out to 50 yards the trajectory remains almost the same.
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Did all get new springs and seals just before your previous test? If yes and this new test is many months later after the new springs have taken a preload "set", isn't this a case of "spring scragging"?
https://www.pyramydair.com/blog/2006/04/spring-talk-some-facts-about-mainsprings/ (https://www.pyramydair.com/blog/2006/04/spring-talk-some-facts-about-mainsprings/)
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Did all get new springs and seals just before your previous test? If yes and this new test is many months later after the new springs have taken a preload "set", isn't this a case of "spring scragging"?
https://www.pyramydair.com/blog/2006/04/spring-talk-some-facts-about-mainsprings/ (https://www.pyramydair.com/blog/2006/04/spring-talk-some-facts-about-mainsprings/)
I dunno'? When I took her down this second time, there seemed to be plenty of spring pre-load as I slowly backed out the spring compressor.
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Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem :(
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The piston seal is very tight in the chamber. The breech seal passed the "tissue" test. Neither would snag a tissue when softly swiped across/around them. I dunno', it's beyond my level of understanding. I'm gonna' look for some delrin washers and see if they'll help. ITMT, I can hit my spoons and spent shotgun shells at 25 yards with regularity using CPHP'S at the slower velocity. So, why fret? If I didn't have a chronograph, I wouldn't even know she had slowed down.
Happy Independence Day, y'all!
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The piston seal is very tight in the chamber. The breech seal passed the "tissue" test. Neither would snag a tissue when softly swiped across/around them. I dunno', it's beyond my level of understanding. I'm gonna' look for some delrin washers and see if they'll help. ITMT, I can hit my spoons and spent shotgun shells at 25 yards with regularity using CPHP'S at the slower velocity. So, why fret? If I didn't have a chronograph, I wouldn't even know she had slowed down.
Happy Independence Day, y'all!
That may be your issue! As Mark has stated. The piston may be to tight in the bore. If it is a new seal it should loosen up after a few hundred shots. I have found that 3 to 5 lbs.of force to move piston in the bore works best for me. If the gun is doing what you want don't worry about it and have fun if not then resize the piston seal.
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Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem :(
That's the piston seal that was in the gu when it was shooting 670 fps in 2016. I think it might be the original and it is very tight. Why would it grow fatter? I'll tear her down again and change out the piston seal. Where do you get the Australian seals?
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Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem :(
That's the piston seal that was in the gu when it was shooting 670 fps in 2016. I think it might be the original and it is very tight. Why would it grow fatter? I'll tear her down again and change out the piston seal. Where do you get the Australian seals?
Huum! The only thing that I can think of that may swell the seal is maybe the lube used?? I guess it's possible if someone used some weird chamber Lube?? I would look really hard at the compression tube for any possible issues.(out of round etc.)
You can get the seals at custonairseals.com
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Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30! ;D
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Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30! ;D
I understand that they tend to run large or XL. Did you have to size them down?
-Y
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No!!!! mine fit perfectly in my 30! but I bought the green eco seal! just to try them out, these are very good seals, ;D
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Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30! ;D
Amazon has them also.