.338-06 Bump Gage Insert

[duurmeehr]

I bought a #17 Sinclair bump gage insert hoping to use it on my .338-06 since the parent cartridge is a .30-06. It listed the .25, .270 but not the .338-06. I should have realized the hole in the insert wasn't to accommodate the neck size of the .338-06!

The hole in it is .350" which is about .015" over what a sized .30-06 is. This thing indexes off the entire sloped shoulder so if i bore it out to fit the .338-06 will it still give me a reference from before and after sizing? I figure the actual point it is sitting is immaterial since there is a 17.5* shoulder cut in it as long as it is consistent?

If so, the next question is how big to bore it. The OD of my fired neck is .370" so I was figuring about .385" to keep it consistent from what the original was?

I don't have a lathe and that would be a small boring bar so I am going to have to try and drill it. I was thinking about a 9.8 mm bit.

I'm going to wind up with more in this dang insert than I paid to bore the barrel!

Does anyone sell an insert that will work for this caliber?

Any ideas greatly appreciated.

 

[338 dude]

Drill it if it gauges off the shoulder it should be just fine you’re not changing that part

 

[Big Mc]

I bought a #17 Sinclair bump gage insert hoping to use it on my .338-06 since the parent cartridge is a .30-06. It listed the .25, .270 but not the .338-06. I should have realized the hole in the insert wasn't to accommodate the neck size of the .338-06!

The hole in it is .350" which is about .015" over what a sized .30-06 is. This thing indexes off the entire sloped shoulder so if i bore it out to fit the .338-06 will it still give me a reference from before and after sizing? I figure the actual point it is sitting is immaterial since there is a 17.5* shoulder cut in it as long as it is consistent?

If so, the next question is how big to bore it. The OD of my fired neck is .370" so I was figuring about .385" to keep it consistent from what the original was?

I don't have a lathe and that would be a small boring bar so I am going to have to try and drill it. I was thinking about a 9.8 mm bit.

I'm going to wind up with more in this dang insert than I paid to bore the barrel!

Does anyone sell an insert that will work for this caliber?

Any ideas greatly appreciated.

Drill ti. Just my two cents Tommy Mc

 

[RegionRat]

I would split the remaining shoulder width in half. That keeps you on the straight part of the shoulder without risk of riding on a radius.

Drill bits often make holes bigger than expected by a few thousandths. That may be good enough for you but, I would suggest drilling about 0.002 - 0.003" undersize, and finish the hole with a reamer. This will usually give you your desired hole diameter within tenths. This can all be done without a lathe, but does require access to a reamer library. Maybe a nearby machine shop will take pity on you so you don't have to buy one? If not, they can be mail ordered.