Umarex NOTOS : SCOPE & FPE QUESTION

[mattboyer30]

Hey everyone -
I've made some progress on my Notos so far, upgrading to FX 380mm barrel & CF shroud from c88, UTG BugBuster scope, polished some internals, etc... - I recently put everything back together after some deep cleaning & attempting to change out the poppet valve with an MCP version, but proved to be a little off - I was advised by a senior that the design can be problematic - stem length, etc - so I went back to the stock. All that aside, I get everything back together and with a chrony on the end I shot off several mags - and started out, I was hitting 400+FPE (?) - and what was weird is that by the time I fired the 30th pellet, it's back up to 790 where it was before cleaning. (I did use correct lubricants on the different components) - so I let it sit a day, came back to it and refilled to 3600 - and same thing. Gradual increases up to the 790 it was set at before. I'd noticed a couple of times even before all the cleaning that my first cold shots were coming out 500-ish FPE, but next couple jumped up to par.
Second, my scope alignment. I was finally zeroed in where windage/elevation were right around their mids left-right / top-bottom adjustments. I put back on and laser boresight, the windage isn't centered without the adjustment maxed out...I took off, loosened & retightened the rear pic mounting screws as I read the POI is sometimes an issue from the Notos' short rear pic rail - then put everything back together super carefully - and same thing. I shot to make sure it wasn't the boresight laser, but it wasnt' the laser.
So in short, Scope alignment must be off somehow, but what would have changed? And what would I focus on first to improve my FPE to shoot what it should on the first cold shot? I appreciate any ideas, I"m learning as much as I can. Thank you -

 

[sb327]

It sounds as though the regulator isn’t regulating. The low fps can be explained by the plenum pressure being too high for hammer strike, then, as the tank pressure drops, your fps climbs. A test for this would be to only fill to approximately 2200 and see what your fps is.

Dave

 

[Firewalker]

400+FPE (?) Do you mean 400fps?

 

[mattboyer30]

Ohhh yes FPS I'd been reading on FPE last few days & stuck in my head lol - thanks for the correction.

That explanation sounds to make a lot of sense...What would the fix for that be then? Less/more hammer spring? Or cut back on the regulator a bit?

 

[sb327]

If that is the problem, the regulator is either SET too high or is malfunctioning and simply bypassing air through.

Have you adjusted the regulator?

Dave

 

[mattboyer30]

Yep I did. Being an amateur, when I took things apart to oil & clean I'd also intended to set the reg & hammer spring back to factory and start working back up now that I have a chrony & find the sweet spot where my FPS maxed out so i wasn't just wasting air opening up too much. - a little more controlled approach to tuning if you will. I'd previously opened up the reg by a 1/4 turn & wondered if it had been too much & was just wasting air. I just assumed the reg screw would bottom out at the factory setting so I turned a lot more than I intended & ended up guessing just by visuals where it was before that & from there kept filling - shoot a few - degas - open up the reg a little, repeat process. Was quite frustrating. So maybe I did open up too much like you said since the first couple shots came out very very low - I'd probably just assumed it needed more & over did it. I do have an airgunarcheryfun drop block w/ the external reg adjustment & 300 cc CF tank coming, but wanted to get this right in the case I don't like the extra bulk & decide to go back to the original setup. Sorry that's a lot of info but thanks for helping me out!

 

[Firewalker]

Yep I did. Being an amateur, when I took things apart to oil & clean I'd also intended to set the reg & hammer spring back to factory and start working back up now that I have a chrony & find the sweet spot where my FPS maxed out so i wasn't just wasting air opening up too much. - a little more controlled approach to tuning if you will. I'd previously opened up the reg by a 1/4 turn & wondered if it had been too much & was just wasting air. I just assumed the reg screw would bottom out at the factory setting so I turned a lot more than I intended & ended up guessing just by visuals where it was before that & from there kept filling - shoot a few - degas - open up the reg a little, repeat process. Was quite frustrating. So maybe I did open up too much like you said since the first couple shots came out very very low - I'd probably just assumed it needed more & over did it. I do have an airgunarcheryfun drop block w/ the external reg adjustment & 300 cc CF tank coming, but wanted to get this right in the case I don't like the extra bulk & decide to go back to the original setup. Sorry that's a lot of info but thanks for helping me out!

OK, lets go over a couple things to get you adjusting and shooting without all the hassle:

1.) Its OK to turn the reg screw CCW under pressure, this increases the PSI on the valve.
2.) NEVER turn the regulator screw CW under pressure, de-gass and turn it to the stop and then turn it back (CCW) 1/2 turn.
3.) Valve lock with a stock hammer spring is about 2400psi. 1900psi is the factory setting on MOST Notos and unless your guns porting is modified, leave it there, you will likely be out of balance.
4.) Turn the regulator screw no more than 1/16th turn at a time and shoot at least one pellet (dry fire at your own risk) to set the reg. Shoot over a chronograph to see if this setting is stable or not.

 

[mattboyer30]

Dang thanks so much for the summary. I'll work with that approach. I'd definitely gotten the reg out of whack. I did read the CW / CCW rule on the site I got the new block from, at the moment I'm still with the stock reg that requires degassing, taking the tank apart, reg pulled out & adjust. I had no idea about the 1/16 turn increment, I'd watched some mod videos and 1/8 turn increment was the suggestion but I did 1/4 because I hadn't learned the "less is more" concept with airguns at that point lol. Learning that one the hard way now. But knowing me, I'll probably still want to degas & reduce the reg a little more before then like was suggested by SB237, just for learning purposes. If 1/16 turn is all that it takes for any kind of change, very good chance it's too wide open due to my guessing where it was at prior to disassembly.
The hammer spring, how would you measure the PSI it's set at? I could locate a tool that measures spring tension somewhere if need be, unless there's a different method to find where that PSI is at currently?
Last question for now...before I took it all apart, it was zeroed right around the middle of the elv/wnd turret adjustments' extents...good bit of leeway for adjusting in either direction. Now, it takes the windage being cranked all the way to the right-end stop before it's centered L/R with where boresight is. I took the back rail back off & re-seated it with no luck. Something got off somehow & not sure what's causing it. As an aside, does the POI change with the angle down that you're shooting? I'd have the zero set just right when level with the target around 40yds, but then go up to the second floor from the window in the house....and with crosshairs at the bull, hits about an inch below. I can't see a powder bullet having that kind of discrepancy, unless pellets are something else? Same distance, same POA, higher shot angle, lower POI. I can't figure it out.
I'm learning a ton from everyone on here and once I"m through the beginner screw-ups I know I'll have a much easier time with the fine-tuning & mods...I just hope to build a good foundation of know-how on the basics before I move forward, I'd really like to stick with this hobby, despite its sometimes budget-unfriendly nature HA! Thank you again.

 

[RatRacer]

@mattboyer30
I would focus on 1 issue at a time.
Get your gun shooting proper for power and consistency 1st and foremost.
The hammer spring has no psi setting. It is used to fine tune your psi output.
Your poi shift may be a byproduct of the inconsistent power output. Revisit this once the gun is shooting properly.

 

[sb327]

Dang thanks so much for the summary. I'll work with that approach. I'd definitely gotten the reg out of whack. I did read the CW / CCW rule on the site I got the new block from, at the moment I'm still with the stock reg that requires degassing, taking the tank apart, reg pulled out & adjust. I had no idea about the 1/16 turn increment, I'd watched some mod videos and 1/8 turn increment was the suggestion but I did 1/4 because I hadn't learned the "less is more" concept with airguns at that point lol. Learning that one the hard way now. But knowing me, I'll probably still want to degas & reduce the reg a little more before then like was suggested by SB237, just for learning purposes. If 1/16 turn is all that it takes for any kind of change, very good chance it's too wide open due to my guessing where it was at prior to disassembly.
The hammer spring, how would you measure the PSI it's set at? I could locate a tool that measures spring tension somewhere if need be, unless there's a different method to find where that PSI is at currently?
Last question for now...before I took it all apart, it was zeroed right around the middle of the elv/wnd turret adjustments' extents...good bit of leeway for adjusting in either direction. Now, it takes the windage being cranked all the way to the right-end stop before it's centered L/R with where boresight is. I took the back rail back off & re-seated it with no luck. Something got off somehow & not sure what's causing it. As an aside, does the POI change with the angle down that you're shooting? I'd have the zero set just right when level with the target around 40yds, but then go up to the second floor from the window in the house....and with crosshairs at the bull, hits about an inch below. I can't see a powder bullet having that kind of discrepancy, unless pellets are something else? Same distance, same POA, higher shot angle, lower POI. I can't figure it out.
I'm learning a ton from everyone on here and once I"m through the beginner screw-ups I know I'll have a much easier time with the fine-tuning & mods...I just hope to build a good foundation of know-how on the basics before I move forward, I'd really like to stick with this hobby, despite its sometimes budget-unfriendly nature HA! Thank you again.

Was the barrel removed/replaced prior to this poi shift?

I’m not certain how the shroud works with your setup but do know if the shroud tensions the barrel, minor unsquareness where the shroud sits (particularly at the receiver) can have a major effect on poi.

Maybe try rotating the shroud 180* to see what effect it has.

Dave

 

[mattboyer30]

Ah funny you ask...I'd went with the 380mm c88 shroud & FX superior liner, and sighted in after getting that all put in. At that point the scope was about mid-way of its adjustments & pretty much zeroed. The shroud had a minor issue from the start - the indent that takes the grub screw was maybe a MM or 2 off, so when I tightened on the moderator, the shroud would pull forward from the breach & leave a short gap where the pellets would get jammed until I figured out what the issue was. I drilled a new indent a tad further down so it sat flush then. What I noticed was that it wasn't necessarily that indent's location, it still pulled forward once I tightened on the moderator. Regardless where the grub screw hit. I took back apart and it looks like the point of the grub screw is now flat which isn't holding the shroud in place like it should. I know the grub screws are cheap steel so been meaning to get the specs of it & see if I can't find something a little more heavy duty grub screw. All that messing around with it makes your point a good one. I had seen an aftermarket pic rail mount from airgunarchery someone mentioned using due to the POI shift - as in maybe the rear rail isnt 100% lined up with the front - so I never considered the shroud being an issue - but interesting to know that's possible so absolutely will try your idea once I find a better grub screw that won't smash flat & lose hold. Thanks a lot Dave -

 

[sb327]

I’m pretty sure the poi shift you have witnessed isn’t quite the same as what may be inherent to the original platform. The inherent ones you have seen mentioned aren’t quite as large as what you are describing.

Good luck and hang in there, you’ll get it all sorted.

Dave

 

[dnye1986]

Hey everyone -
I've made some progress on my Notos so far, upgrading to FX 380mm barrel & CF shroud from c88, UTG BugBuster scope, polished some internals, etc... - I recently put everything back together after some deep cleaning & attempting to change out the poppet valve with an MCP version, but proved to be a little off - I was advised by a senior that the design can be problematic - stem length, etc - so I went back to the stock. All that aside, I get everything back together and with a chrony on the end I shot off several mags - and started out, I was hitting 400+FPE (?) - and what was weird is that by the time I fired the 30th pellet, it's back up to 790 where it was before cleaning. (I did use correct lubricants on the different components) - so I let it sit a day, came back to it and refilled to 3600 - and same thing. Gradual increases up to the 790 it was set at before. I'd noticed a couple of times even before all the cleaning that my first cold shots were coming out 500-ish FPE, but next couple jumped up to par.
Second, my scope alignment. I was finally zeroed in where windage/elevation were right around their mids left-right / top-bottom adjustments. I put back on and laser boresight, the windage isn't centered without the adjustment maxed out...I took off, loosened & retightened the rear pic mounting screws as I read the POI is sometimes an issue from the Notos' short rear pic rail - then put everything back together super carefully - and same thing. I shot to make sure it wasn't the boresight laser, but it wasnt' the laser.
So in short, Scope alignment must be off somehow, but what would have changed? And what would I focus on first to improve my FPE to shoot what it should on the first cold shot? I appreciate any ideas, I"m learning as much as I can. Thank you -

FPS, not FPE, big
difference

 

[Firewalker]

Dang thanks so much for the summary. I'll work with that approach. I'd definitely gotten the reg out of whack. I did read the CW / CCW rule on the site I got the new block from, at the moment I'm still with the stock reg that requires degassing, taking the tank apart, reg pulled out & adjust. I had no idea about the 1/16 turn increment, I'd watched some mod videos and 1/8 turn increment was the suggestion but I did 1/4 because I hadn't learned the "less is more" concept with airguns at that point lol. Learning that one the hard way now. But knowing me, I'll probably still want to degas & reduce the reg a little more before then like was suggested by SB237, just for learning purposes. If 1/16 turn is all that it takes for any kind of change, very good chance it's too wide open due to my guessing where it was at prior to disassembly.
The hammer spring, how would you measure the PSI it's set at? I could locate a tool that measures spring tension somewhere if need be, unless there's a different method to find where that PSI is at currently?
Last question for now...before I took it all apart, it was zeroed right around the middle of the elv/wnd turret adjustments' extents...good bit of leeway for adjusting in either direction. Now, it takes the windage being cranked all the way to the right-end stop before it's centered L/R with where boresight is. I took the back rail back off & re-seated it with no luck. Something got off somehow & not sure what's causing it. As an aside, does the POI change with the angle down that you're shooting? I'd have the zero set just right when level with the target around 40yds, but then go up to the second floor from the window in the house....and with crosshairs at the bull, hits about an inch below. I can't see a powder bullet having that kind of discrepancy, unless pellets are something else? Same distance, same POA, higher shot angle, lower POI. I can't figure it out.
I'm learning a ton from everyone on here and once I"m through the beginner screw-ups I know I'll have a much easier time with the fine-tuning & mods...I just hope to build a good foundation of know-how on the basics before I move forward, I'd really like to stick with this hobby, despite its sometimes budget-unfriendly nature HA! Thank you again.

In full transparency: I did not read your whole reply, I need paragraph breaks and spaces to keep track of all those words!

If you destroyed your regulator, FEAR NOT! I have replacements, just PM me and I'll drop one in the mail for you.

Hammer spring are set at the factory, I dont measure them due to the simplicity of just backing it all the way out to flush, shoot, record the speed, turn 1/4 turn and shoot again, repeat until you hit your top speed and back it off 1/4 turn.

Regretfully, this will be right about flush, maybe a full turn in but the gun comes balanced so no gains may be realized and you may just be wasting time and air.

When I ran into this in the beginning, I started porting and adding barrel length, adding bottles and getting rid of the onboard regulator.