BSA Martini Firing Pin Spring

There was a thread about Eley cartridge headspace or rim thickness being different to nearly all other 22lr manufacturers, for some accuracy or consistency reasons I think. I can't find it on this forum so it must have been on one of the others

ETA: Found it, It was on here.
Eley misfires

I've looked it up in Rimfire Revolution (an excellent book BTW) and it too mentions the size difference but not issues related to it that I can see yet.
 
Hi bill57 very sorry, I have looked all over today and cant find the box with old numbered parts from destroyed guns.
When it does turn up I ll have a look.
 
I must say - they don't look particularly light strike to me, although the pin profile looks rather wide (So spreading available inertia over a wider area).
Any misfire tends to look like a light strike when compared to a fired case because the high pressure caused by firing pushes the case back against the pin.
Looking at the photos, it looks like the head of the case is a bit concave - you wouldn't see that if it was a fired case.
I believe the FP protrusion should be .055" on the MK3.

Has the rifle been trouble free in the past and now having problems?
 
1066 said:
I must say - they don't look particularly light strike to me, although the pin profile looks rather wide (So spreading available inertia over a wider area).
Any misfire tends to look like a light strike when compared to a fired case because the high pressure caused by firing pushes the case back against the pin.
Looking at the photos, it looks like the head of the case is a bit concave - you wouldn't see that if it was a fired case.
I believe the FP protrusion should be .055" on the MK3.

Has the rifle been trouble free in the past and now having problems?
Click to expand...

Whoops. I lifted the picture below from rifleman.org.uk, apologies to them. I had read this (too quickly) as a striker protrusion for a Mk2 of 29 thou, now I see that's the striker travel of .29". what a twat. Can I ask where you got the figure of 55 thou from?

I only got the gun recently, so the problem came with the gun. But it is in good order, it doesn't look heavily abused.
 
Firing pin protrusion with a .22lr is fairly standard at between .040-055" and headspace around .043".
When the pin strikes the case it can't make it's full travel because it's crushing brass so an indentation of 10-15 thou is usually about right. Aiming for harder strikes risks piercing the case. Normally the Internationals have quite tight headspace but I'm wondering it yours is a little slack, maybe because the barrel has been removed and replaced for some reason. If you have excessive headspace you will get light strike misfires. The barrel is held in by a couple of cross bolts - have a look to see if it looks like they have been removed.
Does the action match the rifle, same serial numbers. Is the action take down bolt a good sliding fit in the action wall and also in the action it's self?
These are my .22lr headspace gauges they range from .0405 - 0465"
Screenshot 2026-03-06 192359.png

Ignition system question and thoughts

Generally speaking factory firing pin protrusion has been more or less standardized at about .055", but when actually igniting a primer the pin only goes as far as the prime lets it, which has been reported to be under .030. From this we can conclude the actual in use firing pin fall is reduced...
forum.accurateshooter.com
 
One thing I have noticed on the rifle is that the front sight stool sits slightly to the right, not much but a couple of degrees maybe? When zeroed the rear PH25 is a good bit off centre. Since the barrel is screwed in, could a small amount like that affect headspace?
 
That does sound suspect. However, on the MK3 the barrel is not screwed in the receiver like the MK2, it's pushed in and then clamped by the two cross screws. So, sounds to me as if the barrel has been off for some reason, I'm sure it never left the factory with the foresight block (barrel) on the skew.
 
Thing is the other three sight stools do appear to be correctly aligned anyway, it really does look like a manufacturing fault, however unlikely? Hard to tell if the barrel has been out, though if pushed I might say that the two Allen Bolts have slight signs of the wrong sized Allen Key being used - perhaps the closest metric? I would expect that, if the barrel was removed, I would see close-fit channels for the bolts to go into - am I wrong here? If that was the case I don't see how it would affect headspace anyway (though I think you know a lot better than me).

I compared the fired cases with some from fired in my CZ 452, and the CZ ones are considerably deeper - perhaps what I referred to as "light strikes" should have been "shallow strikes"?
 
I believe the channel in the barrel for the cross bolts is slightly elongated to allow a little fore/aft movement to set headspace.
The "redneck" way to set the headspace, if no headspace gauges are available would be to just slacken the cross bolts, pull a bullet from a round of the type you intend to use. Chamber your blank round, rap the butt on the ground to set the barrel back, tighten up your cross bolts.

Ashampoo_Snap_06 March 2026_23h39m41s_002_.png
 
Thanks for that, it all makes sense now. Put in the headspace guage, tap to set the barrel back and tighten the bolts, and the headspace is set perfectly to spec. I'm guessing don't be shy about tightening the bolts either!

I appreciate your time and help very much, and thank you all for contributing.
 
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