Savage tenon thread LENGTH (small shank)

[supressyourself]

I've done some research, and while large vs small shank / thread pitch specs are everywhere, I'm not finding much for what the LENGTH of those threads up the shank should be. I've seen both 1.600 and 1.550. This (https://en.wikipedia.org/wiki/Barrel_threads) says 42.06 mm, which would be 1.655.


I'm having a problem headspacing a new custom barrel for a Savage Impulse. I have the barrel nut back as far as it will go (ran out of threads), and when the barrel is threaded into the receiver to where the nut hits, I still have about .020 headspace, which is clearly no good. I got to measuring the length of the threads (from breech to last thread), and the custom barrels are shorter.
2 Savage factory barrels: ~1.600
3 Custom (same manufacturer): ~ 1.550



Are my custom barrels just not threaded to spec, or is something else off?

[shoots100]

I measured two factory small shank .308 barrel tenon threads and all of them are around 1.650" long.
I had no issue trying to head space the barrels in an extension while I have my predator apart for a severe cleaning.
I had a couple of short shanked thread barrels that wouldn't headspace correctly.
They were threaded to fit a zermatt receiver.
I put the barrel in a barrel vise, used a lot of cutting fluid and chased the threads with a 1-1/16"- 20 hex die like this till I was able to headspace.
https://metalcities.top/product/1-1-16-20-right-hand-thread-die-1-1-16-20-tpi-sn-3/


SJC

[supressyourself]

Thank you. I figured they were short. It seems odd that while the thread pitch and diameter specs are everywhere, no one mentions the length. Seems like something every gunsmith would have, considering how many places do Savage style barrels.
I'm going to see what the custom barrel company says. I have another barrel from them that head spaced fine on Savage model 10 receiver, but it's a few years old. Not sure if they changed their threading, or if the model 10 design accommodates the shorter threads whereas the Impulse does not...

[shoots100]

Here's a pic showing the difference between my Impulse barrel nut and the standard small shank factory savage barrel nut.
The threads are a lot shorter and a lot less shroud on the Impulse nut I make, which is the same dimensions as the factory Impulse barrel nut, just with flat sides.
There's almost 3/8" less thread on the Impulse nut compared to the factory nut, so in theory, you should have more play to headspace.
If I get some time, I'll compare receivers dimensions.

SJC
9660

[supressyourself]

I made the same comparison. I had originally bought a standard Savage nut for the Impulse barrel swap, but I'm not sure that would work even with the longer threaded factory barrel.

[shoots100]

The standard length savage barrel nut won't work with the Impulse extension.
Been there done that some time ago and that's when I started the process of making my own QC barrel kit.
The only thin type of barrel nut savage sells is for the large shank barrel, as the tenon threads on the large shank barrel are short too.

SJC

[supressyourself]

I contacted Savage about what the proper spec is supposed to be. They say they don't give out that information, so that's really helpful...