Firing Pin Springs

[Rabbitz]

Hi All,

I need to replace the firing pin spring in one of my Sportco Clubman rifles. It just doesn't strike hard enough any more. Obviously I am about 50 years too late to get a brand new factory one.

How do you work out the specifications of a spring? I would guess coil diameter, wire thickness are a given, but length and "strength" are not really known factors.

Also where would I buy a spring from, if I work out the specifications?

The spring fits fairly closely into a lengthways hole in the firing pin, could I use a small piece of brass rod placed in after the spring but before the retaining pin to increase the compression on the spring?

[The Raven]

I was looking for a Sportco Model 40 (rim fire) spring some years ago and found a website claiming to stock them. Unfortunately the website was full of products it never stocked.

If you find a source of springs let me know.


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[Seddo]

it might be easier to get a gunsmith to make you one.

[Rabbitz]

it might be easier to get a gunsmith to make you one.

You may well be right.

Any suggestions on such a gunsmith?

[Rabbitz]

I did some more disassembly and diagnosis this afternoon.

I have another Clubman (and all sorts of bits) in the safe, so I disassembled its bolt and compared springs and there's not much difference, so swapped the springs and the pin indent was still marginal. Swapped the spring back into the spare rifle and the indent was good - so it appears it's not the spring.

The rifle in question is rear locking and the headspace is set using shims between the bolt handle assembly and the bolt body. I made up a temporary shim out of paper and the imprint is much better. So it looks like headspace may be the culprit.

I have ordered a handful of 0.1mm shim washers and I'll wrangle them into shape and see what happens...

[LoneRider]

try
https://grenfellarmouringservice.com.au/
or
https://www.tsengineering.com.au/
bothe do sportco/omark gear

[Rabbitz]

try
https://grenfellarmouringservice.com.au/
or
https://www.tsengineering.com.au/
bothe do sportco/omark gear

Cheers, if I have no luck with the shims then I'll give then a call.

Thanks

[The Raven]

I did some more disassembly and diagnosis this afternoon.

I have another Clubman (and all sorts of bits) in the safe, so I disassembled its bolt and compared springs and there's not much difference, so swapped the springs and the pin indent was still marginal. Swapped the spring back into the spare rifle and the indent was good - so it appears it's not the spring.

The rifle in question is rear locking and the headspace is set using shims between the bolt handle assembly and the bolt body. I made up a temporary shim out of paper and the imprint is much better. So it looks like headspace may be the culprit.

I have ordered a handful of 0.1mm shim washers and I'll wrangle them into shape and see what happens...

Hmm, sounds a lot like my issue (despite them being different beasts altogether).

Are you getting failures to fire? That's my problem. Not sure if it's the pin, spring, or wear on the bolt/receiver lock up.

[Old Trev-39]

Some time back I had a Mod.2 Brno bolt that was quite sloppy around the bolt handle and ignition was not the best. I shimmed up the play in front of the handle and problem fixed. I always decock my bolts whenstoring.
Cheers,
Trevor.

[The Raven]

Some time back I had a Mod.2 Brno bolt that was quite sloppy around the bolt handle and ignition was not the best. I shimmed up the play in front of the handle and problem fixed. I always decock my bolts whenstoring.
Cheers,
Trevor.

Not being an expert amateur gunsmith could you explain how and where the shimming is done?

I’d imagine a gunsmith would build up either the bolt or receiver portion that engages with each other.


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[Rabbitz]

Hmm, sounds a lot like my issue (despite them being different beasts altogether).

Are you getting failures to fire? That's my problem. Not sure if it's the pin, spring, or wear on the bolt/receiver lock up.

Yes. Plus the firing pin imprint on the rim was not very deep.

Some time back I had a Mod.2 Brno bolt that was quite sloppy around the bolt handle and ignition was not the best. I shimmed up the play in front of the handle and problem fixed. I always decock my bolts whenstoring.
Cheers,
Trevor.

The Brno bolts are a bit similar, so would probably headspace in a similar way.

I always decock the bolts for storage too.

[Rabbitz]

Some time back I had a Mod.2 Brno bolt that was quite sloppy around the bolt handle and ignition was not the best. I shimmed up the play in front of the handle and problem fixed. I always decock my bolts whenstoring.
Cheers,
Trevor.

Not being an expert amateur gunsmith could you explain how and where the shimming is done?

I’d imagine a gunsmith would build up either the bolt or receiver portion that engages with each other.


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In the case of the Sportco a shim goes between the body of the bolt and the cap with the bolt handle. Think of the shim as a very thin flat washer.

I'll try and get a photo in the next few days.

[Rabbitz]

Ok, I stole some images instead.

The shim:


Where the shim goes:

The locking lug fixes the location of the bolt handle assembly in relation to the breech face. By putting a shim between the handle assembly and the bolt body means that the body is effectively moved closer to the breech face which moves the firing pin further forward, hopefully meaning a deeper indent into the cartridge rim.

[The Raven]

Ok, that looks pretty simple, so where do I get them?

Would love to get the family sportco shooting well again.


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[Rabbitz]

You'll need to disassemble the bolt to measure the outside diameter of the bolt body where it goes inside the bolt handle assembly. That will give you an idea of the inside diameter of the shim.

The outside diameter of the shim will match the outside diameter of the handle assembly - but chances are there will be some filing to get them to match (or dremel work if you prefer ).

I went for 0.1 mm thick shims and will stack them if I need to.

I ordered from:
https://www.minibearings.com.au/