Cannot get a seal at the probe.

[angrybear]

HELP
I just cannot get a seal at the probe, there's a huge air blow back on firing,
I've tried everything I can think of including trying to lap the probe to the breach, are there super strong springs available ??

I shot it with my face next to the magazine, it was like getting slapped the air hit me so hard.

This is my newish build .22 MFR

[Ca_Varminter]

If is a Real MFR not a converted Rapid....
It should have an adjustable probe bolt-body..
See my post on how take a part your bolt.. it also has the
procedure to adjust the probe!!
https://rapidforum.co.uk/forum/index.php?topic=238.0
Hope this helps..
Good Luck,
Stuart

[KevG]

you sure its not coming from between barrel and block
KevG

[Dave74]

Have you had the barrel out,is this just happened without touching anything,barrel port round wrong way wrong probe for calibre,does a magazine slip nicely into magazine well with barrel protrusion ,barrel blocked to name a few

[Ca_Varminter]

Well if the the Barrel was removed...
Here is my Tech post on how to Remove/Install your Barrel on a MKII/MFR/S-Type....
https://rapidforum.co.uk/forum/index.php?topic=408.0

Good Luck,
Stuart

[Squinty]

shouldn't need a stiffer prole spring unless its too loose and causing feed issues.
tell-tale is with the magazine out the probe drops below the bore centre

Original probe & barrel?
Should be able to adjust the probe, I've done a bit of fast barrel swapping and to be honest I've seated the barrels flush with the block every time apart from my earlier R7 with the old type bolt.

Maybe...if the bolt has been taken apart...

possible that the bolt handle has been over-tightened, just gone 1/2 turn  too far in and is touching the adjustment link pin.
Can lock up creating a false set and give the impression of a weak spring because the inner and outer dont telescope properly.

Same with a replacement dog...had one where the M3 screw was longer and touching the pin.

[angrybear]

Ok well,
Stuart, this is a new build from parts, yes it has the adjustable bolt, screwed in to the point that the inner is protruding from the outer before fitting, but the bolt locks fwd with ease.

Kev, How can I tell ? I suppose it could be from around the barrel, all I know is it's a huge blast of air coming out of the right hand side of the mag.

Dave, the port is lined up, it's actually shooting really well, & when I stop the leak it's going to need turning way down, I reckon about 2/3rds are going down the barrel & 1/3 is blowing out the side.

It's a brand new .22 probe from Dr Bob & the 19" barrel I got off eblag, there is no obvious damage to the barrel, & the barrel is fitted using the magazine & paper method.

Squinty, Both bolt handle & dog are new so I'll check those thread lengths.

Thanks for the ideas chaps, I'll play with it again this afternoon, I just noticed the time.

[Ca_Varminter]

Ok well,
Stuart, this is a new build from parts, yes it has the adjustable bolt, screwed in to the point that the inner is protruding from the outer before fitting, but the bolt locks fwd with ease.

It's a brand new .22 probe from Dr Bob & the 19" barrel I got off eblag, there is no obvious damage to the barrel, & the barrel is fitted using the magazine & paper method.


Thanks for the ideas chaps, I'll play with it again this afternoon, I just noticed the time.

Hi angrybear,

Well with your description of your build... All new Parts..
With the barrel installed correctly, the probe adjusted all the way out...
But you still don't have a stiff lock up....
The likely culprit is the Barrel.... The breach machining!
If you know someone close by, I would try a know Good barrel!!!!

Here is my barrel and probe after lapping...



Good Luck,
Stuart

[angrybear]

 And the points go to...

Squinty 

At least I think they do 

I'd stripped it down last night, so reassembled it this morning exactly the same way as usual,
except I did it in a slightly different order by adjusting the bolt before I fitted the cocking dog or tightened the bolt handle,
doing that, has indeed allowed me to get the bolt lockdown a bit tighter   

low & behold it appears to be cured  so I can only assume it was either the bolt handle or dog screw stopping the last few thou of bolt/probe adjustment.

Now with the blowback gone, I just need to lose the extra 168fps that have appeared   

[KevG]

normally the adjuster type bolts and probe should have a slightly shorter run of the threads on the cocking handle and dog screw, only problem with building from various parts
KevG

[Squinty]

congrats, just shows how the tolerances vary from gun to gun.

[Dave74]

Thanks for the update,glad you got it sorted

[Dr Bob]

Just a footnote.  The coil probe spring is nothing to do with sealing the at the barrel it is only to separate the inner and outer probes after the inner has pushed the pellet past the port. The actual sealing effort is done by the wavy spring washer.
This spring washer is fitted in between the probes on the adjustable bolt and at the back of the inner probe and adjusted by shims on the none adjustable bolts. The guy on eBay selling FAC probe springs is a tosser.

[angrybear]

Just a footnote.  The coil probe spring is nothing to do with sealing the at the barrel it is only to separate the inner and outer probes after the inner has pushed the pellet past the port. The actual sealing effort is done by the wavy spring washer.
This spring washer is fitted in between the probes on the adjustable bolt and at the back of the inner probe and adjusted by shims on the none adjustable bolts. The guy on eBay selling FAC probe springs is a tosser.

That's interesting because I have no wavy spring washer 

[Squinty]

there should be a disc spring (Belville)  part # 9k  between inner and outer probes.
I tried a couple of thicknesses and found that a  0.35mm disc gives a nice progressive lock without blowback.

The early non-adj had a  crinkle washer/wave spring and Belville plus whatever shims (M6 washer) behind the inner.

Can use a hard o-ring which gives a very soft lock, I tried that and hmmm ...50/50, gotta sit right on the bottom of the spring.
Bucketboy converted some by turning an o-ring seat in base of the outer

my idea?......shorten & open up the base of the outer probe and fit a delrin/peek flanged bush....example image