MFR / TTR2 Probe Stem sealing?

[MartinTTR2]

I have stripped my TTR2 down this week. I found a couple of gremlins and I think I've solved them but I have a question for the forum:

My gun is a .22

What is there to stop blow back along the Probe Stem (Item 9C) that fits inside the Probe (Item 9B).
I have just assembled it and could blow through from the pellet end - n0t a lot just by mouth but there is high pressure behind the pellet.

The other thing, the probe sits against the end of the barrel - is this the only sealing mechanism and what if they are ever so slightly misaligned?

Is it worth lapping the end of the probe : barrel area to create a better metal to metal seal?

[Ca_Varminter]

The sealing between the inner probe and outer probe is accomplished by a thin shim washer 9k

Some have used small O-rings pushed down the inner probe shaft.........
Also if noticed there is a couple of grooves on the inner probe shaft.
These are interference grooves..to slow down the velocity of the air flowing down the shaft.
This helps to limit the amount of air blow-by.

On the barrel and outer probe seal....If you ever change the barrel or probe, you DO need to Lapped them together!! here is one of my tech post on how to do it....
https://rapidforum.co.uk/forum/index.php?topic=935.0

Have Fun!
Stuart

[Squinty]

9k is a Belville washer, needs to be facing ( towards the barrel

Also provides compression to hold the bolt in the gate and prevents a hard metal to meatal lock dowm that can potentially bend the probe.

[MartinTTR2]

Stuart... what a star!

All of that earlier post seems perfectly fine to me. I just so happen to have a lathe and some Delrin rod under the bench.
Somewhere I know I have some super fine lapping compound so I'll give it a spin just to make sure that the faces are mating properly.
The barrel has been cleaned through and some rough spots polished out. I've no doubt that the barrel has moved a smidgen,
KevG gave me some adivice earlier about making sure the ports are aligned - they were out a fraction - everything is seated properly now but I still want to check the probe to barrel seating, so your advice is really good.

Do you know if anyone has put O-ring seals around the barrel end to ensure the barrel to block fitting is air tight?
My barrel feels a bit loose - I did a bit of machining in an earlier career and quite fancy pitting some seals on the barrel.

Regards

Martin

[MartinTTR2]

Squinty - Thanks for that - the probe assembly is currently in bits sitting in a jar of methanol - I must admit, I did not take too much notice when I took it apart and may have easily missed the bit about the direction of the washer.

Regards,

Martin

[Ca_Varminter]

Stuart... what a star!
...............
Do you know if anyone has put O-ring seals around the barrel end to ensure the barrel to block fitting is air tight?
My barrel feels a bit loose - I did a bit of machining in an earlier career and quite fancy pitting some seals on the barrel.

Regards

Martin

Are you looking for something like this???

I did this mod on my Titanium(Ul_Ti_mate) Rapid.
It does 70fpe with 26 grn slugs....So I wanted a little more sealing....

Stuart

[MartinTTR2]

Stuart - yep - that looks like what I have in mind.

[Ca_Varminter]

***Hint****
If you decide to go with the O-ring on the barrel mod.
When you install the O-rings, do this in the Mag slot!!
This is due to the sharp edges created by the barrel pinch bolt hole when it intersects the barrel channel!!
It will slice any tight fitting O-ring like butter.

Stuart

[MartinTTR2]

Stuart... that is a good idea.

I was just wondering about how to take the sharp edges off, that you describe.

I was thinking of polishing the edges with a dremel but you've just saved me probably an hour or so of trial and error and I probably would still have sliced the o-rings.

Cheers - Martin