Loosing FPS

[jn316]

Recently did a chrono on my 3 month old Beeman R9 .22 Cal with around 1500 rds threw it and found that the rifle has lost an aveage of 61 FPS (15 rd. strings) ,Using the same RWS 11.9 gr. pellets as was used when new.
Question that I have ; is this a normal thing or should I be concerned ? Accuracy is okay @ 15yds nickel sized groups when I'm doing good .
Thanks in advance for your help
Sal

[Motorhead]

Those guns SADLY are very prone to having a piston seal getting damaged during assembly. While I'm not crying WOLF ... past experience ( being a lot actually ) has this more than just hearsay.

Bummer, there really nice shooting guns too.

[DanD]

Recently did a chrono on my 3 month old Beeman R9 .22 Cal with around 1500 rds threw it and found that the rifle has lost an aveage of 61 FPS (15 rd. strings) ,Using the same RWS 11.9 gr. pellets as was used when new.
...

I'm curious. What are the before and after numbers?

[jn316]

Just checking my notes on my chronograph and noticed the ES =31.8 and SD=9.1 . Would that also indicate posbaly nicked seal ?
Oh by the I have cleaned the barrel, and only used a loose 22 cal bore snake.

[jn316]

Here are the original numbers
Beeman R9
RWS Hobby 11.9 grains

1. 738.7
2. 736.7
3. 740.7
4. 735.2
5. 729.1
6. 740.9
7. 730.4
8. 733.3
9. 733.7
10. 733.7
11. 745.4
12. 738.9
13. 735.0
14. 729.1
15. 734.9
16. 730.8
17. 736.6
18. 730.4
19. 731.8
20. 725.3

HI. 745.4
Lo. 725.3
Av 734.5
Es 20.1
Sd 4.9
Ad 3.8

[nced]

Recently did a chrono on my 3 month old Beeman R9 .22 Cal with around 1500 rds threw it and found that the rifle has lost an aveage of 61 FPS (15 rd. strings) ,Using the same RWS 11.9 gr. pellets as was used when new.
Question that I have ; is this a normal thing or should I be concerned ? Accuracy is okay @ 15yds nickel sized groups when I'm doing good .
Thanks in advance for your help
Sal

Is there a possibility that the gun was "burning off" factory lubes 1500 shots ago so the velocities were inflated? You didn't mention the before and after VELOCITies so there isn't a way to judge if the gun was/is shooting normal.

According to the Straight Shooters site the "Our Take" report for the muzzle velocity of a new .22 cal R9 shooting advertised 11.9 grain RWS Hobbies was 693fps.........
http://www.straightshooters.com/beeman-r9-.22-beech.html

Velocities can vary considerably from gun to gun, even the same make and model so take printed velocities with a grain of salt.

[jn316]

 Umm

[jn316]

Very possible Just thought 60-70 FPS is alot
RWS 11.9 grain 22 cal.
These are the most recent numbers
Av.   671.3
Hi.    675.8
Lo.    667.3
Es.     8.5
Sd.     3.5
Ad.     3.1

[Bladebum]

So, I just recently purchased an R9 in 22 about 2 months ago now(I think) and had similar issues. EXCEPT mine didn't lose just that much, it dropped around 100 fps or more and even worse was the spreads were, well everywhere. Knowing something was up I took the gun apart and found the face of the piston seal was cracked like a China doll.

So ordered the vortek kit and seal since I planned on doing it anyways and after everything settled in I'm shooting about 660 with CPUM 14.3s

So I would say yes to a number of things mentioned here already that you MAY have an issue like kinked/broken spring, nicked/cracked seal or possible breach seal issue....or you could have had some inflated numbers off the bat from some extra dieseling...I hate not knowing so I take guns apart and disect

Either way, there are three major power components to these guns, piston seal,  breech seal and mainspring. If one is off in some way things get whacky. If your not afraid of voiding warranties and have mechanical ability to do so I'd rip that baby apart and check things out. If nothing else you'll get familiar with the gun and parts and be able to clean it up a bit. JMO hope this helps

[mikeyb]

Very possible Just thought 60-70 FPS is alot
RWS 11.9 grain 22 cal.
These are the most recent numbers
Av.   671.3
Hi.    675.8
Lo.    667.3
Es.     8.5
Sd.     3.5
Ad.     3.1

I would expect to see a little drop in velocity due to "spring set" (look up spring scragging) and the burn-off of factory lubricants.

You newest average velocity seems a little low. NOT bad seal or broken spring low. Maybe just rifle-2-rifle variation low?
The ES and SD numbers look excellent (to me) and I would think the rifle has settled in to its normal performance range. With ES and SD numbers like that you should be getting nice tight target groups.

From my experience bad piston seals provide multiple signs. Harsh shot cycle, very low average velocity numbers,  high ES and SD numbers, and wide spread target groups. If you experience all of those conditions a bad piston seal is the most likely cause.

I'll take accuracy over power any day. If that was my rifle and it was shooting tight groups I'd stop there. Obviously if you want or need more fpe, then you'll have to dig deeper.

Either way, best wishes!

[jn316]

Thanks again for all the great advise and sorry for the wonkey delivery of infomation. 
Going to try a couple more strings today with the chrono a bit closer to the muzzel say around 1-2 feet and see how that goes.

[nced]

So, I just recently purchased an R9 in 22 about 2 months ago now(I think) and had similar issues. EXCEPT mine didn't lose just that much, it dropped around 100 fps or more and even worse was the spreads were, well everywhere. Knowing something was up I took the gun apart and found the face of the piston seal was cracked like a China doll.

So ordered the vortek kit and seal since I planned on doing it anyways and after everything settled in I'm shooting about 660 with CPUM 14.3s

So I would say yes to a number of things mentioned here already that you MAY have an issue like kinked/broken spring, nicked/cracked seal or possible breach seal issue....or you could have had some inflated numbers off the bat from some extra dieseling...I hate not knowing so I take guns apart and disect

Either way, there are three major power components to these guns, piston seal,  breech seal and mainspring. If one is off in some way things get whacky. If your not afraid of voiding warranties and have mechanical ability to do so I'd rip that baby apart and check things out. If nothing else you'll get familiar with the gun and parts and be able to clean it up a bit. JMO hope this helps

"face of the piston seal was cracked like a China doll"
Interesting because I received a HW springer for some work with a similar "cracked face seal", plus a found a similar pic on line..........

If you look at the pics you'll see that the seal face was deformed at the transfer port as well as cracked.

I've been using a home turned oring sealed piston cap for years because "way back when" I was shooting about 1000 shots per month I had the "rubber" piston seals erode at the transfer port and that happened with both HW factory seals and a couple aftermarket seals I used but never had any "face cracking".........


I really don't know why the recent HW piston seals are failing (perhaps "bad rubber") but I do know that new HW95 piston seals aren't very consistent in size with some seals fitting the receiver "properly snug" and others rather loose. A friend of mine bought a new HW95 and gave it to me to strip of factory lubes replacing with Krytox and installing a new "home rolled" spring kit based on a Maccari E3650 spring with tight fitting guide and top hat. When I disassembled the gun I noticed that the brand new factory piston seal was very "loose fitting" in the receiver. I removed that seal from the piston replacing it with another new seal from my parts bin and it fit the receiver PERFECTLY.

I really don't know the reason for the cracking of current HW piston seals, however I got no "transfer port" damage or cracking after the test of a "proper fitting" HW95 piston seal. I'm wondering if the HW piston seal face damage is/was due to "loose fitting seals" that is allowing the piston to slam against the end of the receiver, judging by the impression of the transfer port on the seal faces in the pics.     

Anywhoo.......last year "just for grins" I temporarely replaced my oring sealed piston cap with a new "proper fitting" HW95 factory seal using Krytox GPL205 lube (was testing the Krytox lube on the piston seal). After 1200 CPLs the inspected the piston seal looked like this (no face cracking)............

[mr007s]

Thanks again for all the great advise and sorry for the wonkey delivery of infomation. 
Going to try a couple more strings today with the chrono a bit closer to the muzzel say around 1-2 feet and see how that goes.

For lower powered guns I set mine up 4-6 inches from muzzle.

[Artie]

I had a Norica with a flattened breech seal that dropped fps by 40-50 psi. It was a 14-16 fpe gun (.177). Swapped seals and all was good.

[Bladebum]

Ed, that is very interesting, I think your on to something with the loose fitting seals. That is the only thing that makes sense, other than some bad detonations, which I never had.

I have about 1500 rounds on the new kit and seal and all seems to be great. Nice tight consistent spreads and shooting one hole groups at 20 yards. I did put the new seal in fairly tight as I like to shoot them in, and recently it feels like it has loosened up nicely. 

[Motorhead]

Check this out from @ 2 years ago ... SAME model rifle.   https://www.gatewaytoairguns.org/GTA/index.php?topic=140939.msg1422263#msg1422263

[jn316]

WOW 
Not sure what to say paid alot of money for the R9 .I HOPE its not whats wrong with mine.
So many good reviews out there as well.

[Bladebum]

Check this out from @ 2 years ago ... SAME model rifle.   https://www.gatewaytoairguns.org/GTA/index.php?topic=140939.msg1422263#msg1422263

man that kind of &^^& ticks me off, it doesnt matter if it was a vendor or manufacturer problem, THAT SHOULD NEVER BE THE PROBLEM ON A NEW GUN! I think most would agree that it seems this stuff is common in the airgun world? Imagine going to buy a brand new chevy truck with "zero miles" and you get down the road, pull over to have a burger then notice your leaking oil and the truck is running rough. NOBODY in thier right mind would do anything different than call the dealership and say give me another truck...

Now, i buy a gun that has the potential for lots of tuning like HWs and Diana...but niether the manufacturer nor the distributor knows who these guns are going to and if it was someone who just saved for months to get a top of the line german gun, imagine the dissapointment.

To the OP, im not sure what your intentions were(to tune or to shoot the way it came) but theres plenty of very experienced guys on here that know every nook and crany of these guns who can help you get the gun you were expecting. Maybe try an assortment of different pellets first to really get a good look...if velocities are inconsistant and groups are wonky, id say its time to look inside.

[jn316]

Just  crazy thinking  but has anyone ever come up with a seal or piston that would rotate kinda like the intake or exhaust valves in a small engine ?  Would possibly not burn the same spot  ever time . Just thinking out loud

[nced]

Just  crazy thinking  but has anyone ever come up with a seal or piston that would rotate kinda like the intake or exhaust valves in a small engine ?  Would possibly not burn the same spot  ever time . Just thinking out loud

I personally believe that the old HW95 piston seals were deliberately molded to fit the "piston seal mounting button" a bit loose so they would rotate a bit with each shot due to the twist imparted while the spring expanded with the shot and even some "newer design" HW piston seals can show a "rotary transfer port pattern"...........


As a side note..........
As long as I've owned HW springers, in the owners manuals there were always a few items considered as "consumables" and these were main springs, piston seals & breech seals to be periodically replaced when needed (like tires on a car).

While the metallic piston seals of the FWB300 match rifles are reported to last 100s of thousands of shots, other spring guns are prone to damage, even some expensive ones.........
FWB300


Theoben Elliminator


Webley Hatsan Patriot Piston


Beeman R9


Old FWB124, they have upgraded seals ?


Gamo Piston Seal


SLR98 Piston Seal


Anywhoo......piston seals do go bad with enough shooting. When living in West Virginia I would shoot about 10,000 shots per year and when testing out a couple aftermarket piston seals I found that velocity would drop in about 6 months due to seal erosion at the transfer port. At that time I had my .177 R9 tuned to shoot 7.9 grain CPLs at 910ish fps (about 14.5fpe) and piston seals were replaced once a year shooting a 1250 count box of CPLs per month.