Accessory Rail Thread Thread

[Rabbitz]

This thread is about a thread.

(Sorry I couldn't resist)

Does anyone know what the thread is on a Sportco accessory 'rail'?

None of the bibs'n'bobs I have laying around seem to fit. As it is from the 1950's I expect it is BSW or BSF but I don't have anything to try it with.

Any ideas?

[Rabbitz]

After some playing around, it looks like it is 1/4".

An M6 runs through the thread but is quite loose. An M6 has a 1mm pitch so 25.4 TPI.

So I guess I am looking at 1/4 UNF at 28 TPI or 1/4 BSF at 26 TPI.

[Camel]

Tec screws.

[Rabbitz]

Tec screws.

I want to knock up a benchrest adapter plate, so liquid nails might yet be involved...

[Old Trev-39]

Could be a BA thread as an old Sportco R/F I had donkey"s years had BA threads. Do not know where you might find screws ect. now.
Cheers,
Trevor.

[Rabbitz]

Hi Trevor,

I'll have a look into that, thanks.

BTW it is a rimfire.

[Rabbitz]

It looks like it might be a 0 BA. Which is close but not the same as a M6.

From a bolt reseller website:
"0BA appears similar to M6x1mm, the male and female surfaces do not mate properly for bearing a load" which is what I am seeing.

Ahh the joys of mucking around with rifles older than myself...

[kickinback]

BSF has a 55* form while metric is 60*.

My money is on 1/4 BSF


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[morerams]

Likely to be 1/4"BSF to match up with common Parker Hale accessories of the time.