6br case protrusion from barrel face

[1953greg]

for savage lrpv 6br, what is the preferred case protrusion from the barrel breech face? bolt face depth is .112. thanks greg

 

[KRP]

.115-.120 go-gauge protrusion with that bolt head, giving .005-.010 space between the bolt and breech after installation using the nut. A factory or pre-fit barrel will likely have more than that ~.135 protrusion.

 

[Ggmac]

.117 no sense in having more case exposed . Generally I have .005 bolt nose to barrel clearance and cut my barrels at something less then 90 deg . It depends onthe type of extractor used .

 

[RWO]

The Savage spec for the target action is 0.130" max. from bolt face to barrel face. I think it would also apply to any similar modern Savage
action. IMHO, 0.117" would be a minimum.

RWO

 

[hoz53]

The Savage spec for the target action is 0.130" max. from bolt face to barrel face. I think it would also apply to any similar modern Savage
action. IMHO, 0.117" would be a minimum.

RWO

So if the the bolt face depth is .112 and the protrusion is .130 that means there is .018 breech face to lug clearance right? Good info to have as many people set that clearance much closer. .005 to .010--and it's good to know it would be alright if it would be a bit more.

 

[GrocMax]

I've personally seen more prefits with chambers cut too deep rather than too shallow.

 

[Ggmac]

If you can go to the min , like I said there's no good reason to have more of the case sticking out unsupported . Even though you could . This .117 allows you a slightly more generous bevel on the chamber mouth .

 

[hoz53]

If you can go to the min , like I said there's no good reason to have more of the case sticking out unsupported . Even though you could . This .117 allows you a slightly more generous bevel on the chamber mouth .

I agree I think the less unsupported case the better but As you say you could. I just wonder as long as only the solid head of the case is what's sticking out what it would hurt to have more unsupported case. Evidently not much.

 

[GrocMax]

There's the gas escape clearance in case of a rupture to consider.
Those vent holes in pretty much every bolt action receiver serve no purpose if the bolt nose is very close to the barrel. I'm not saying something bad is bound to happen with tight clearance but that safety factor was built in and there's really no reason not to use it.

 

[jfseaman]

OK, forgive me if this is a question easily answered...

How do you measure bolt nose to breech face clearance?

 

[GrocMax]

Most of us don't measure that directly, its the difference between a go gauge protrusion and bolt face to bolt nose. In the case of a flat barrel like a Savage if the go gauge height from barrel is .125" and the bolt face to bolt nose is .115" its inferred there is .010" clearance.

 

[hoz53]

There's the gas escape clearance in case of a rupture to consider.
Those vent holes in pretty much every bolt action receiver serve no purpose if the bolt nose is very close to the barrel. I'm not saying something bad is bound to happen with tight clearance but that safety factor was built in and there's really no reason not to use it.

That is a good point to. So you think there is no more chance of weakening the case if a little extra clearance is there as long as only the solid head of the case is sticking out of the barrel?

 

[KRP]

So if the the bolt face depth is .112 and the protrusion is .130 that means there is .018 breech face to lug clearance right?

If headspace is held to the go-gage length exactly during installation it would be. It's likely slightly more, tightening the nut increases headspace and thus bolt to breech clearance.

Poor mans method to measure bolt to breech, squish a piece of solder in there then measure it. A slightly more expensive option would be Plastigauge.

 

[hoz53]

OK, forgive me if this is a question easily answered...

How do you measure bolt nose to breech face clearance?

yeah like Groc said its usually subtracting measurements but if you really want to measure it on a savage flat breech face you could stick a go gauge in the barrel before installed on action and hold the bolt up to it. Then you could measure the clearance with a feeler gauge. On a remington with counterbore you could actually make washers out of different thicknesses of shim stock and get a pretty good idea if you really wanted to get the measurement. I heard somewhere McMaster Carr sells these.

 

[hoz53]

If headspace is held to the go-gage length exactly during installation it would be. It's likely slightly more, tightening the nut increases headspace and thus bolt to breech clearance.

Poor mans method to measure bolt to breech, squish a piece of solder in there then measure it. A slightly more expensive option would be Plastigauge.

I thought about the plastigauge and the solder is a good idea. That makes sense about the headspace as its probably a few thou more. Thanks

 

[GrocMax]

That is a good point to. So you think there is no more chance of weakening the case if a little extra clearance is there as long as only the solid head of the case is sticking out of the barrel?

That's a debatable subject. Probably depends on the case itself as to how much is too much, that's the thickest part of the case by far right there at the base/extraction groove area.

6XC II chamber (308 base diameter) and 22-250 cases the last .150" or so is totally unsupported by the chamber wall and it doesn't seem to hurt anything other than an ugly line where the two finally meet.

 

[hoz53]

That's a debatable subject. Probably depends on the case itself as to how much is too much, that's the thickest part of the case by far right there at the base/extraction groove area.

6XC II chamber (308 base diameter) and 22-250 cases the last .150" or so is totally unsupported by the chamber wall and it doesn't seem to hurt anything other than an ugly line where the two finally meet.

Ok that's what I wondered about Thanks

 

[1953greg]

.117 no sense in having more case exposed . Generally I have .005 bolt nose to barrel clearance and cut my barrels at something less then 90 deg . It depends onthe type of extractor used .

care to elaborate on diff extractor angle and
how much less angle and why? thanks greg

 

[Ggmac]

care to elaborate on diff extractor angle and
how much less angle and why? thanks greg

PM sent , still drinking coffee !

 

[gunsandgunsmithing]

FWIW, a Remington has about .150" of unsupported case. Whatever style or brand of action, I prefer about .005" of bolt nose to barrel clearance. The Savage has leaves less unsupported case than most actions do.