No8 trigger adjustment problem

I need some advice regarding the fine tuning of the trigger on one of my two No8 rifles.
Both are set up with two stage trigger; however while one has an excellent second stage release; the other rifle has a very poor second stage. Once the second stage pressure has been reached, it requires about 3-4mm (3/16") extra pull to release.
Having looked at the No8 handbook; I believe the pressure setting screw (item 18) that goes up through the centre of the trigger is the cause. Unfortunately it is seized in the trigger. I have removed the locking grub screw to inject penetrating fluid, but it's still stuck fast.
I don't want to "fubar" the screw or the trigger! (The screw slot is still intact at present)

I need to confirm if this is the correct adjustment for this issue? and if the screw will not move; are trigger parts available for this model to replace it?

Thanks in advance for any info.
30Three.

To make sure that we are all singing from the same hymn sheet, you download the picture that you are referring to and I will cross reference that and the parts that I am referring to, to the parts list identification.

But be warned. I know some of the experts will tell you that it is really simplicity itself, but learning this mechanism too almost a week using large scale adjustable models on which to practice and learn and digest. And never, not ever, NEVER let a screwdriver or spanner get to within 100 yards of the SCREW, stop, trigger and the NUT, trigger stop screw (this is a round nut with opposite locking flats machined across the sides). This is factory set in respect to certain actuating bents of the trigger and must not be adjusted

Thank you for your reply. The picture I was refering to is figure 5 in Section 2 of the No8 Handbook. I found it on the Rifleman forum. Not sure if I can download the image; but I'll look at that htis evening.
When I bought this rifle, it had a bad single pull; because the main springs for the trigger had been wound up tight. It was not done by removing the outer spring. Releasing some of the tenion brought it back to two stage; but God only knows what else has been touched. If there are precise measurements to be checked; it should be within my capabilities if I have the info to work from. (I am an Aston Martin technician so have a good understanding of mechanical stuff).

I would say that being an Aston Martin technician JUST qualifies you to work on a No8 trigger mechanism!!!!! In the meantime, why don't you contact Brian at BDL Ltd in SC; USA He has copies of the No8 user handbook. This is the next best thing to the old EMER.

As a matter of interest to other No8 owners (or UN-interest, depending on your point of view......) the SCREW stop, trigger was set at the factory using a GAUGE, plate, trigger No8 rifle. A few of the big Base workshops might have had this plate but I never saw one outside Carlisle.

This is the diagram with the numbers that correspond to my question in the 1st post. Looking again at the image; I think the lock nut 13 may be missing on this rifle.
The screw 18 being stuck may well be because the rifle has had the metal re-finished; I'm assuming they didn't strip it completely when carrying out this task.


Attachment 71169

Before we go any further, you need to remove the screw 18, the SCREW, setting, trigger. It is locked in place by a small grubscrew at the front, (14?) SCREW, locking pull-off. All the threads are - if my memory is correct - BA. Can you soak these and try to ease them out? You might also set about replacing the PIN, axis trigger (16?) and the PIN axis, cradle (46) with stainless steel.

If you have got the trigger mech out, you might as well clean it all down and polish the cocking piece bent on the rear of the sear (3) too.

On the top, rear of the sear cradle (11) JUST below where the front face of the cocking piece (21) is situated...... that's it, JUST above where the arrow head indicating point 20 is shown, you will see a bright polished and hardened section on either side. These two edges control any undue movement of the cocking piece so polish them while you're there with a forward/rearward polish.

It seems as though a real expert has been into your trigger mechanism so I am seeing whether we can get new items 12 and 13 for you AND clear instructions for re-setting it up again. This is all related to the polished edges I mentioned earlier.

Is anyone else following this stuff............ If so, get in touch with Brian at BDL and get the handbooks............... PLEASE........ Doing all this from memory is doing my head in!

Thanks for your advice Peter; it is much appreciated. I'll try and free off the seized setting screw (18) with some Dexron and Acetone mixed 50/50. I've found this is the best penetrating mix for steel and I've tried loads over the years. Maybe putting the trigger in the ultra sound bath with this mix may get it loose.
I'll get in touch with Brian Dick regarding the handbook and possible parts; probably get a handbook for my L39 while I'm at it (not that it needs any work)
Should get some time over Easter so I'll let you know how it turns out.
cheers, Shaun.