Gunsmithing ARC Nucleus Savage prefit question

[Maddy]

I'm looking at getting a Savage prefit barrel ordered to go with the American Rifle Company Nucleus action that I've got ordered. On ARC's website they says: "The barrel thread specification for Nucleus is 1.063 – 20 UN 2B making it compatible with many off-the-shelf barrels such as Savage small-shank pre-fits"

A barrel maker is informing me that Savage standard thread pitch is 1.055-20, so a standard prefit would be .008 smaller and wouldn't work well. What gives? Not sure what to think. Thanks

 

[sgtsmmiii]

I'm looking at getting a Savage prefit barrel ordered to go with the American Rifle Company Nucleus action that I've got ordered. On ARC's website they says: "The barrel thread specification for Nucleus is 1.063 – 20 UN 2B making it compatible with many off-the-shelf barrels such as Savage small-shank pre-fits"

A barrel maker is informing me that Savage standard thread pitch is 1.055-20, so a standard prefit would be .008 smaller and wouldn't work well. What gives? Not sure what to think. Thanks

Remington 700's are 1.062 X 16, if I recall correctly. Maybe a typo from ARC? I'd email Ted to be sure.

 

[Sierra770]

I see some savage small shank threads represented as 1 1/16" -20. 1 1/16 = 1.0625.

 

[whatsupdoc]

Savage OEM is 1.055-20

 

[Sierra770]

http://www.bugholes.com/product-p/bug-nut-1.06-20tpi-1.20b.htm

http://www.criterionbarrels.com/savagecontours.pdf

I see where it is spec'd at 1.055-20. The two above have it at 1.0625. Not sure what that's about.

 

[Mordamer]

1.0625 is just the name of the thread spec. It is just a different way of writing 1-1/16". A 1-1/16x20 2A thread on a barrel tennon should fall within the range of 1.061-1.053" for a major diameter. So your 1.055" major diameter is well within the correct thread range for 1-1/16x20 2A threads.

This is a simple case of some people listing the actual major diameter as measured and some listing the Unified National thread spec naming convention.

Also realize that all the jibber jabber in this thread is discussing MAJOR DIAMETER. Major diameter is only one dimension in the thread specifications. A gunsmith could cut a barrel tennon with a 1.053" major diameter on the threads and as long as the pitch diameter was also within spec there would be no issue.

Long story short, a Savage small shank is going to work perfect in the ARC Nucleus just as they say it will.

 

[Sierra770]

Highly informative. Thank you.

 

[bohem]

We make several forms of barrels for the Nucleus currently. Here they are:

http://patriotvalleyarms.com/savage-pre-fit-barrel/
http://patriotvalleyarms.com/replacement-match-barrel-bighorn-mausingfield-nucleus/

 

[Maddy]

Thanks for clearing that up. I was hoping it was something like that.

 

[sgtsmmiii]

1.0625 is just the name of the thread spec. It is just a different way of writing 1-1/16". A 1-1/16x20 2A thread on a barrel tennon should fall within the range of 1.061-1.053" for a major diameter. So your 1.055" major diameter is well within the correct thread range for 1-1/16x20 2A threads.

This is a simple case of some people listing the actual major diameter as measured and some listing the Unified National thread spec naming convention.

Long story short, a Savage small shank is going to work perfect in the ARC Nucleus just as they say it will.

Your avatar handle is well deserved. Great info. Thanks.

 

[Maddy]

Just an update. Ted from ARC emailed me yesterday and said:

Your gunsmith doesn't know what he's talking about. The Savage small shank thread is properly specified as 1.0625-20 UN 2A which can have a major thread diameter between 1.053 and 1.057 inches. Threads are controlled by pitch diameters, not by the major or the minor diameters.

 

[Sierra770]

Thanks for posting.

 

[ptm121]

Just an update. Ted from ARC emailed me yesterday and said:

Your gunsmith doesn't know what he's talking about. The Savage small shank thread is properly specified as 1.0625-20 UN 2A which can have a major thread diameter between 1.053 and 1.057 inches. Threads are controlled by pitch diameters, not by the major or the minor diameters.

Bingo. Obviously Ted knows his stuff, but to make this a little clearer for the non-gunsmith/engineer/machinist: take a Savage barrel with a 3A interference fit OD of 1.0625” (the spec is 2A as defined above, but a good gunsmith with your action in hand would shoot for just under that number. A pre-fit will be smaller (2A) to guarantee compatibility). Chuck it up and use a file to knock the tops off the threads until it mics 1.055”. Did the fit change? Of course not. The only change was that the threads went from being very pointy to pretty dull. The pitch diameter, the size of the threads as they actually mate, is unaffected.