Savage small-shank go-gauge protrusion

[moxford]

Hi all,

Just got a barrel back which was supposed to be a Savage small-shank tenon. The max spec for the amount of "go gauge stick out" off the barrel is 0.128 - 0.130 from other forums, but I cannot find anything official.

Protrusion on this particular barrel (30 sherman magnum, same case as 300 PRC) is at 0.150, so it will have 0.020 more unsupported case around the web if I just set the barrel forward the same amount.

Does anyone know the "official" spec? Is it actually 0.128-130?
For 30SM/300 PRC, am I just being obnoxious and the 0.020 doesn't matter? Really would like to avoid damaging brass and/or having separations, but maybe 0.150 is technically out of spec for Savage small-shank, but completely fine otherwise.

Thanks!
-mox

 

[gnochi]

Depends on bolt head depth. For 338 LM, factory has like 0.145” protrusion.

If you pull the bolt too, and snap the go gauge in, how much space is between bolt head and barrel breech?

 

[Steel head]

Depends on bolt head depth. For 338 LM, factory has like 0.145” protrusion.

If you pull the bolt too, and snap the go gauge in, how much space is between bolt head and barrel breech?

This.
Case design is also a factor.
Case head/extractor groves vary.

As long as the bolt head isn’t contacting the barrel or much more than just the taper of the extractor grove is exposed your probably ok

My 260 barrels are usually about .130ish.

 

[Wannashootit]

.125-.130
Technically, I believe it is out of "spec".
Really depends on the brass, I posted a thread along the same lines recently where I'm using a special shoulder "go" gauge for a rimmed cartridge that would normally seat tight against the rim. From what I determined, it's not uncommon to go as much as .150- but it's best to section the brass to make sure you're not beyond the casehead.

Savage Shooters - Barrel Chamber Depth Verification

One benefit of the Savage platform, whether it's an Axis or a 110-Series, is how easy it is to change barrels and how readily available pre-fit barrels are these days. Even though pre-fit barrels are intended to be ready to install right out of the box, it is highly recommended that you always...

www.savageshooters.com

 

[MakeSawdust]

I'm not going to search for the thread forever, but if memory serves me correctly, some of the custom actions that take "savage small shank barrels" need slightly more go gauge protrusion to keep from having the bolt head rub on the face of the barrel. I believe the person who stated this also stated that .140" was plenty of clearance for the custom actions in question. I would contact the company that chambered the barrel and have a discussion with them.

 

[Steel head]

I'm not going to search for the thread forever, but if memory serves me correctly, some of the custom actions that take "savage small shank barrels" need slightly more go gauge protrusion to keep from having the bolt head rub on the face of the barrel. I believe the person who stated this also stated that .140" was plenty of clearance for the custom actions in question. I would contact the company that chambered the barrel and have a discussion with them.

Yea, my Nuke is perfectly happy with .130 and that’s what I cut barrels at for it and my savage.

Measuring the extractor cut on a few of my magnum cases(7 Saum and 338 edge) I’d probably not sweat having .150 protrusion as it’s barely past the extractor cut.


It’s a bit beyond narrow cuts like on the 338 Norma but still not terrible.


found this, appears 300 prc has a .139 cut for the extractor

 

[moxford]

Okay, finally had a few minutes to read through and take a look at things. Thank you very much to everyone who has taken the time to respond so far!

So if it's at 0.150 and head-height of the 300 PRC parent is 0.139, that leaves 0.011 of unsupported case right at the web.

With the go-gauge in the chamber, barrel vertical, with bolt resting on top (face down), stacked feeler gauges show 0.030 clearance on the extractor/nose.

Had it been cut to the desired protrusion of 0.130, the body/web would have been fully supported and it would still leave 0.010 extractor clearance.

Crud. Was hoping to use this for an upcoming hunt, but if I have to get it rechambered (and re-rent the reamer, it's not going to be ready in time.)

Thanks all.

Cheers,
-mox

 

[gnochi]

I wouldn’t be too worried; brass in center fire cartridges is usually a solid plug for at least a couple mm in front of the extraction groove, and you would have ~0.25mm unsupported in front of the groove. If you want to double check, sacrifice one cartridge, remove the bullet and powder, remove the primer, and cut the case in half.

 

[Steel head]

I wouldn’t be too worried; brass in center fire cartridges is usually a solid plug for at least a couple mm in front of the extraction groove, and you would have ~0.25mm unsupported in front of the groove. If you want to double check, sacrifice one cartridge, remove the bullet and powder, remove the primer, and cut the case in half.

Same, as long as the chamber chamfer is reasonable I’d probably run it without worrying.
There is probably another .100 forward of the extractor cut that’s basically solid brass especially on a magnum case.

 

[Steel head]

Just swiped these pics of 300 prc brass from @Supersubes
He’s one of my barrel mentors.

 

[moxford]

I'm going to cut one tonight (ADG) for peace of mind before I do anything else. Depth micrometer (calipers) shows ~2mm forward of extractor cut, so around 0.080. Chamfer looks to be another 0.020. Puts it maybe in the ballpark of 0.050 of solid brass before the support starts falling away.