Velocity Loss ?

[Oldgringo]

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? 

[truck driver]

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.

[DanD]

Were the light conditions the same for your first test?

[Allen Rice]

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

[Airnut]

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.

[BackStop]

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)

[Mark 611]

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! 

[Oldgringo]

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.

[BackStop]

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

[Airnut]

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!!

[Oldgringo]

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.

[BackStop]

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. 
Actually, I did have one tin of pellets that got mixed between the two.  Took me a long time to sort them out...
 

[Airnut]

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.

[Mark 611]

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

[nced]

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..........


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".............

Compare the above with this HW95 piston with "HW lube" straight from the box..............

[Jason_Garvin]

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

[SpiralGroove]

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

[Mark 611]

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

[Airnut]

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

Great thinking and a very distinct possibility with respect to lube migration into the compression chamber on the first test!

[Oldgringo]

I used the tar that came with the JM kit.  Is that a no-no or did I overuse it?