Umarex Notos detuning for more shots per fill?

[kopi]

Hey Everyone!

I really like the current form factor (and look) of a stock notos. But I was wondering if anyone has detuned this thing to get more shots per fill. My max distance to shoot in my backyard is about 30 yards, so I don't think I really need much power for that distance. I have the hammer spring turned down about 1.5 turns to the left and get roughly 35 shots till i get down to 2000psi on the gauge.

Just would like advice if it would worth it to possibly lower the regulator and/or put in a lighter hammer spring, or if I should look into getting a c88 plenum thing to get more shots per fill. I do use a hand pump which is why I like the current size and form factor. Thank you in advance!

 

[JaceSpace1369]

Hey Everyone!

I really like the current form factor (and look) of a stock notos. But I was wondering if anyone has detuned this thing to get more shots per fill. My max distance to shoot in my backyard is about 30 yards, so I don't think I really need much power for that distance. I have the hammer spring turned down about 1.5 turns to the left and get roughly 35 shots till i get down to 2000psi on the gauge.

Just would like advice if it would worth it to possibly lower the regulator and/or put in a lighter hammer spring, or if I should look into getting a c88 plenum thing to get more shots per fill. I do use a hand pump which is why I like the current size and form factor. Thank you in advance!

Look into the last two pages of this thread, you should be able to get some help.

Post in thread 'Low powered guns' https://www.airgunnation.com/threads/low-powered-guns.1310052/post-1738639

 

[kopi]

Look into the last two pages of this thread, you should be able to get some help.

Post in thread 'Low powered guns' https://www.airgunnation.com/threads/low-powered-guns.1310052/post-1738639

Dude this is perfect thank you! Kind of bummed I need to remove the factor moderator to fit the plenum, but eh its not too crazy for more shots

 

[JaceSpace1369]

Dude this is perfect thank you! Kind of bummed I need to remove the factor moderator to fit the plenum, but eh its not too crazy for more shots

You are very welcome!

 

[bubbahotep]

Why would a bigger plenum be involved with lowering power? Oversized plenums reduce shot consistency I hear.

 

[kopi]

Why would a bigger plenum be involved with lowering power? Oversized plenums reduce shot consistency I hear.

I’m curious about this as well, I added the crc plenum lowered the reg down to about 800psi and hammer spring all the way down and I’m at about 30 shots and have 1500 psi in the tank

now I have it set to 1600 psi, hammer spring at factory and … 30 shots later and 1500 psi in the tank

I really need to learn and understand how to tune

 

[Florida_Man]

From what I remember @Dairyboy going through, he had to cut his hammer spring to get velocity down. The HS adjustment in stock form doesn’t allow a lot of adjustment

 

[bubbahotep]

Guess I'll try these $5 next day springs. Stock is 9x1.1x60, these are 9x1x50, I couldnt find any 60s on amazon.

Amazon.com

 

[kopi]

Guess I'll try these $5 next day springs. Stock is 6x1.1x60, these are 6x1x50, I couldnt find any 60s on amazon.

Amazon.com

Thanks for the link man, I will give these a shot as well

 

[daddypaddy]

From what I remember @Dairyboy going through, he had to cut his hammer spring to get velocity down. The HS adjustment in stock form doesn’t allow a lot of adjustment

exactly this. i cut mine to get an fps range of 570-740 with 14.3gr cphp using hammer spring tension.

 

[bubbahotep]

50mm spring was too short. Got 250 fps with screw all the way in, screw all the way out was so slow the pellet got stuck in the moderator. A 55mm spring would be good or perhaps putting some shims inside the hammer.

 

[bubbahotep]

M5 socket head cap screw can slip onto the end of the spring and into the hammer and would add 5mm to the 50mm spring length. Spring can also be stretched about 5mm but might need heat-treating so it doesn't revert.

 

[Ratzy]

Why would a bigger plenum be involved with lowering power? Oversized plenums reduce shot consistency I hear.

I did a lot of testing with plenums 25cc, 50cc, 125cc and 250cc. There was zero evidence a larger plenum has any deleterious effect. If it exceeds the volume of air that passes through the poppet valve it becomes just like an unregulated bottle. As long as the pressure remains stable the should not be any lack of consistency.

Where there could be an issue is with the regulator refilling the plenum. I never saw that but have read of issues of delays between shots to fill the plenum.

 

[Ratzy]

I did a lot of testing with plenums 25cc, 50cc, 125cc and 250cc. There was zero evidence a larger plenum has any deleterious effect. If it exceeds the volume of air that passes through the poppet valve it becomes just like an unregulated bottle. As long as the pressure remains stable the should not be any lack of consistency.

Where there could be an issue is with the regulator refilling the plenum. I never saw that but have read of issues of delays between shots to fill the plenum.

Also, the plenum allows you to lower regulated pressure and achieve the same power as the gun without a plenum.

The pellet remains under acceleration in the barrel longer so the same exit velocity can be achieved with lower regulator pressures.

More air volume available when the poppet opens. Without a plenum you are limited to the volume between the regulator and the poppet.

 

[bubbahotep]

Where there could be an issue is with the regulator refilling the plenum. I never saw that but have read of issues of delays between shots to fill the plenum.

Hysteresis, if the plenum is too large the pressure wont drop enough on every shot to open the valve to refill the plenun.

 

[Ratzy]

Hysteresis, if the plenum is too large the pressure wont drop enough on every shot to open the valve to refill the plenun.

I actually put a ~400cc plenum together. My nephew's friend has a .510 Texan and asked if it could be regulated. So I took a Tee and 125cc and 250cc tubes and built it up.

I dont have a Texan so I tested it out on my 24" barrel 25cal Condor. I put probably 40-50 rounds through and it stayed right at 923-927fps. Regulator was the regulator off that Condor set at ~1750psi.

I understand hysteresis quite well and I don't disagree that it could be an issue but the empirical data didn't show that.

 

[bubbahotep]

Cap head screw raised fps to 400, max with washers was 500 fps before sear wouldnt engage. That spring is too small/weak. With the Kryciron moderator it was completely silent at those speeds and I could still get same hole groupings.

9 odx1x60mm spring (reduced wire thickness from oem but same dimensions) would be next step. I guess 3/8od" x?x2.5" might be easier to find at ace hardware but might be too wide. (9.5mm). Still on the prowl for a 500-600 fps spring without hacking the original or using spacers.

Shot 500 rounds and still had 3200 psi in my 1.6l bottle, starting from 4200.

 

[bubbahotep]

Going to try this 9x1x60 mm spring https://www.amazon.com/dp/B09LV363YZ

2-3 week ship time tho. SAE equivalent or cutting down a long spring might be quicker. 60mm is unusually long, most options end at 50mm.

 

[kopi]

Cap head screw raised fps to 400, max with washers was 500 fps before sear wouldnt engage. That spring is too small/weak. With the Kryciron moderator it was completely silent at those speeds and I could still get same hole groupings.

9 odx1x60mm spring (reduced wire thickness from oem but same dimensions) would be next step. I guess 3/8od" x?x2.5" might be easier to find at ace hardware but might be too wide. (9.5mm). Still on the prowl for a 500-600 fps spring without hacking the original or using spacers.

Shot 500 rounds and still had 3200 psi in my 1.6l bottle, starting from 4200.

Holy crap thats wild, thank you so much for all the data

 

[bubbahotep]

If you got that 50mm spring then I would do the shortest m5 cap head at Ace (m5x8mm like I found) and some 1/4" thin washers to stack (i used a too thick rubber grommet)

We use a rubber mulch pellet trap with plywood and an apple tree as backstops and deer came up and napped and snacked 10 yards away from the constant fire without being bothered. We even raced cans along their flanks.