O3A3 action thread

[1smalljohnson]

I've got an O3A3 action coming from Navy Arms. No barrel. I've heard these actions have true "square" threads, not acme. Anybody got any information about these things? If I've got enough meat, I may well chase the threads to standard 60 degree. Thoughts? Anybody know the dimensions for the cutter to cut true square? Seems something fundamentally wrong with square. Either the male or the female MUST have some relief cut in...

1smalljohnson

[OKChipmaker]

If no one comes up with it before, I can get the info you need tomorrow.

I have an old barrel at the shop that I can get the TPI and min.max.from.

For what its worth,the kraig,1903,and m1,all used the same thread.I do not know about the m14.

[rolland]

The barrel shank is .734" long, With a body Dia of .990 A thread Dia of 1.040".

The threads are square with a pitch of 10 threads per inch.

[rws]

Rolland has it right. I ground a tool very similar to a cuttoff tool, .052" wide which gives a bit of clearance. I found it tends to curl a bit on the edges while cutting the threads, so I just used a flat file to keep things smooth as I went.

[Highpower]

Here is the receiver thread should you need it.

1903 receiver drawings

[Euph0ny]

Here is the receiver thread should you need it.

1903 receiver drawings

That is very interesting. Thank you. What is the source book, please?

[38_Cal]

Is this an original receiver? You'll need a drawing of the barrel shank, since there is a cut for the extractor in the barrel as well as a feed cone cut in the breech.

David

[Frank46]

bbl shank in front of receiver 1.145
shank length .734
bbl shank where threads are 1.040
outside diameter cone on breech .990
angle of cone on breech face of barrel 41 degrees
thread ten square threads 10 sq tpi
source of information "bolt action rifles by Frank de Haas revised edition
Hope this helps, Frank