Umarex Notos Bottle Conversion Cautions:

I have completed just over a dozen Notos bottle conversions using an Amazon purchased drop-block and wish to bring some of the challenges to light and discuss the issues I have found with the parts and fit-up.

First off is thread pitch, thread angle and such:

The thread pitch of the air block on your Notos to the drop block is M16X1MM. The air block needs a bottoming tap, this means that the tap has to have a flat end, no point.

The tap has to cut clean threads, you need to use cutting fluid and do short cuts, clear the threads often.

Thread pitch of the block gauge and foster fill fitting are both M10X1MM tapered threads. Please dont use non-HPA hardware and ALWAYS hand-thread the fitting all the way to the bottom of the hole before wrenching on them. Both holes also require that the fitting contacts the white teflon/nylon washer before tightening. The angle and thread tip are also specific to HPA

Second is the drop-block:

Every drop-block is threaded a little differently from the factory. Be aware that your drop-block may not clock with the air-block or it may be a perfect fit! PLEASE try to hand fit your air-block to your drop-block first before you send it off to be converted.

Third is the regulator:

When purchasing a regulator, make sure you purchase one with the pressure you want for the speed you are looking for. My Notos was set to 2200 psi on the regulator, I purchased the same and I still get around 750 fps.

You have two options when it comes to the plunger where the reg attaches to the drop-block. The first is to make a pin that fits inside the drop-block that will depress the plunger inn the reg, allowing air to pass from the regulator to the gun. This is a safety device and "allows" the bottle to be removed from the drop-block without the bottle emptying catastrophically.

The second option is to simply remove the end of the regulator and pull out the plunger, reattach the end and attach it to the drop-block. The safety is missing but is it actually needed?

I do provide a service to convert your Notos but you can do the conversion yourself as well with some tools. Good luck and good shootin!
 
You got any pics to show what you are putting together or is it something I’ve seen in a different thread already? I recall I saw one where the bottle was a little too big and was rubbing the moderator. I’m interested if you’ve gotten a set up going that fits well and is machined to not be rubbing.
 
You got any pics to show what you are putting together or is it something I’ve seen in a different thread already? I recall I saw one where the bottle was a little too big and was rubbing the moderator. I’m interested if you’ve gotten a set up going that fits well and is machined to not be rubbing.

Yes, I am doing a full conversion starting tonight and am taking pictures of the parts, the work and the results. I will also be doing a baseline with the gun before its touched as well.

Rubbing is a matter of initial setup with the bottle conversion. I sanded off some of my moderator housing to accommodate the bottle but found that all I had to do was air it all down, add a shim to establish the gap and reassemble the conversion and i have a nice gap that has stayed solid for 2 months with no change.

I will be switching to a .22L bottle (smaller OD) this winter for weight savings and to shorten it up some. I have also found another adjustable regulator that is shorter I will be doing trials on when it arrives so that we have more options in the future.
 
Found this on AliExpress, also with a smaller OD

Screenshot_20230715_072232_AliExpress.jpg
 
Another drop block is done, took 0.0012" off the face to clock it tightly to the air block. Ill pull my bottle and regulator off my gun and pressure test the conversion tonight. Bottle is going to be supplied by the customer so i will ship it complete sans bottle.

Barrel was lapped using a medium grit compound then followed up with a good metal polish using a pull/pull line with a TIGHT patch.

Interestingly, there was no way to run any tight patch from the crown, the broach/button was pushing a lot of burrs flat that hooked on the patch and would not allow a back pull. A soaked patch with compound was able to smooth the worst of these off and the pull/pull line with a patch was finally able to run back and forth with a few good "grabs" along the barrel.

It took about 2 hours of slow and methodical hand lapping to smooth the entire length of the bore to a consistent feel with almost 20 full minutes spent on an ugly looking ramp. A tight pellet pushed through the bore gave me a smile as it pushed along with equal friction all along the bore. This means that I got the "ramp" right as the lead gets pushed into the pellet and as the pellet decreases in size, the felt friction remained the same.

A good polishing followed by a deep cleaning was followed by a crown polishing.

The depth of the moderator housing is about 5 inches deep and the crown is somewhat hidden within the moderator housing, making measurements a guessing game at best. I settle on .256" OD for the brass rod and found that to be a little large. I turned it down to .250 and that seemed to contact the crown well.

More compound applied to the tip and a lot of spinning took off an estimated .5mm and extended the crown into the barrel lands and grooves. Proof of this work will show up in two ways if it was performed successfully: 1. The bore lapping/polishing will allow the bore to be cleaned with one wet patch and one dry patch. Any lead that sloughs off will come out with the wet patch and the dry patch will come out clean sans any extra fluid. 2. The crown will help keep a more precise grouping, less fliers and perhaps tighter groups.

I also took the cocking mechanism apart, deburred it all, got some good oil on the pivot points, tested the trigger break and got it to around #2.

I have a few regulators coming soon in a couple weeks, a couple more drop blocks too and I will continue to offer Notos conversion services until you all are satisfied with your guns. If anybody is interested in CF bottles, I can get Tuxing bottles.
 
Firewalker tuned up my Notos.
It’s now very smooth, quieter, and with an under 2 lb trigger.

Do not hesitate to send him your Notos.

Thanks Perle!

It's nice to get feedback. :)

Im glad its doing what you want, I do pour myself into these guns and pay close attention to the details.
 
An update to the above: When getting the conversion drop block, make sure to assemble the air block to the drop block to the regulator to the bottle FIRST! The barrel assembly is second and if your bottle is too big or too long and it hits the moderator housing*, you will need to remove some plastic off your housing so that there is a gap between the bottle and housing.

*Factory housing

2 more out the door tomorrow, I have both regulators and drop blocks in stock, super fast turnarounds if you send me your air block.
 
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