Umarex Porting the Notos Breech

[Pantanni]

Am i correct in assuming that in order to port my breech to 4.5 mm I will need to re-drill and thread this upper threaded section?

My 4.5mm bit hits the threads and doesn't freely pass them down to the air transfer port in the breech. I've removed the o-ring before testing the drill bit.

 

[RobM123]

NEED MORE pics.. the real restiction in the tube adapter at the back of the tube thats retaineed by 4 m4 bolts..

 

[Pantanni]

NEED MORE pics.. the real restiction in the tube adapter at the back of the tube thats retaineed by 4 m4 bolts..

The picture is of the hole in the bottom of the breech.

This picture does not show it completely disassembled, obviously. With everything removed my 4.5 mm drill bit touches the threads. The hole i need to get to is through this threaded hole.

 

[Pantanni]

NEED MORE pics.. the real restiction in the tube adapter at the back of the tube thats retaineed by 4 m4 bolts..

I successfully ported that to 4.5mm

 

[RobM123]

ok cool, you must be getting some serious numbers already.. Doing the transfer port on the notos is hard, very limited access for boring the block itself.. I attempted to bore the block also , but gave up at some point

 

[BABz58]

I successfully ported that to 4.5mm

Did you have to rethread?

 

[Firewalker]

Am i correct in assuming that in order to port my breech to 4.5 mm I will need to re-drill and thread this upper threaded section?

My 4.5mm bit hits the threads and doesn't freely pass them down to the air transfer port in the breech. I've removed the o-ring before testing the drill bit.

View attachment 520569

OK, you need to remove the valve first then use a 4mm drill bit to open the Transfer Port then use a hand reamer to open it to 4.5mm.

You DO NOT drill the threads!

You DO NOT retap the hole with the same threads or it will just strip out.

 

[Pantanni]

OK, you need to remove the valve first then use a 4mm drill bit to open the Transfer Port then use a hand reamer to open it to 4.5mm.

You DO NOT drill the threads!

You DO NOT retap the hole with the same threads or it will just strip out.

Thank you for once again sharing your knowledge!

 

[Pantanni]

Did you have to rethread?

I have not rethreaded anything. I haven't attempted anything others than trying to slide the drill bit into that hole, with all valve parts removed, to reach the hole I need to port in the breech. The bit will hit the threads first.

I will use a smaller bit and ream to final per firewalkers recommendations.

 

[HogKiller]

I have not rethreaded anything. I haven't attempted anything others than trying to slide the drill bit into that hole, with all valve parts removed, to reach the hole I need to port in the breech. The bit will hit the threads first.

I will use a smaller bit and ream to final per firewalkers recommendations.

Are you doing this by hand or with a mill/drill press? By hand, good luck, start the drill IN the hold just touching the bottom, use the threads as a drill bushing. Make sure the drill bit is running true and is nice and sharp.

 

[Pantanni]

Are you doing this by hand or with a mill/drill press? By hand, good luck, start the drill IN the hold just touching the bottom, use the threads as a drill bushing. Make sure the drill bit is running true and is nice and sharp.

I have a drill press but I also have friends that have machining capability that i could bum a few minutes off of maybe.

 

[RabbitofCaerbannog]

I have a drill press but I also have friends that have machining capability that i could bum a few minutes off of maybe.

Post complete porting. 2200 psi w 17gr Griffin .218 LDC

DO NOT forget to open up the tp hole in the barrel breech

 

[Pantanni]

DO NOT forget to open up the tp hole in the barrel breech

I should know what you're saying here but just for fun, say it again? I want to make sure I don't ruin my gun.

 

[RabbitofCaerbannog]

I should know what you're saying here but just for fun, say it again? I want to make sure I don't ruin my gun.

When you pull the barrel out the hole in the barrel end which lines up with the transfer port in the receiver. Drill them both the same. I countersunk slightly and polished. I used a high grit cone polishing bit and mirror polished. That's just what I did.

 

[Ltomlin]

Dumb NOTOS question, but is the “transfer port” the same thing as the “breech” when talking about drilling the hole out? I see in the pics above but still not clear on where it would be opened up to be larger. I have opened up the port in the block to 4.5 mm so far, getting about 870 fps/22 fpe right now, 13.43 pellets, using huben valve and .42 liter bottle, reg is around 2100. I already have the upgraded 500mm barrel kit from C-88 Air installed so I believe there would be no need to drill out that port. Going to get new poppet from Maple Custom, So what’s left to drill out / open up now? I believe there were 4 places that have been mentioned as it relates to drilling out larger? I have a drill press and vise now to work with. Thanks for all the great info.

 

[RabbitofCaerbannog]

The exhaust port on the valve housing, the transfer port between the valve exhaust and the breech tp and the breech tp. Get them all to 4.5mm. all of those. transfer port is the hole from the valve to the projectile. The air pathway.

 

[Ltomlin]

Hi RabbitofCaerbannog - got this taken apart now, just trying to confirm where the hole needs to be drilled out. Attached pic is of the hole (2.5mm+ currently) inside on the brass piece, assuming this doesn’t come out? Or am I looking at the wrong place to enlarge the hole? Doesn’t look like the pic of the second hole with the oring would be able to be drilled. Thanks for your help!

 

[Ltomlin]

Update - I got everything drilled out to 4mm and cleaned up and reassembled. Have to say, the results I got were awesome. Here’s my 15 shot string using 13.43 grain pellets. Not sure how this stacks up to others results but I’ll take it! Thanks to everyone who helped me do this. This forum is the best.

 

[RabbitofCaerbannog]

Very nice. I guess you got the valve housing figured out. Sorry I just got back on here.

 

[Ltomlin]

Very nice. I guess you got the valve housing figured out. Sorry I just got back on here.

Yes it was a little scary but I took my time. Messed with the hammer spring a little but honestly not sure I need any more power for any reason, but I’ll try anything if there’s anything else to do. Thanks for your help!