Bushing diameter for 6.5x47 Lapua (Hornady headspace gauge tool)

[jimsr]

I did a search and couldn't find any information. Hope to find the size to bore the Hornady blank bushing to but couldn't find that info, should I use the dimension that is 1/2 way from the diameter at the start of the shoulder to the diameter at the start of the neck? This would be the datum line, correct? Also, I guess where the shoulder of the case hits the inside of the bushing doesn't have to be exactly at a prescribed place if your headspace gauge and the bored bushing are used together, is my idea about right?Thanks for any information. Jim

 

[X-Caveman]

I did exactly what you suggested, (neck dia +dia @ body/ shoulder junction)/2. I don't know if it's correct, but it seems to work just fine. Sorry I don't remember the diameter, but I could measure it when I get home and let you know if you'd like me to.
Travis

 

[jimsr]

Thanks Travis, I think you're right, I measured .383 or 4. That's just a little bigger than the Hornady "C" bushing which is .375. I made a chamber cast and the C bushing made a mark just a little short of 1/2 way down the shoulder angle. I guess I don't understand the formula for finding the datum line as I think I've been told it varies between different cartridges. I will be alright if I do not use measurements with those taken with a different bushing. Thanks for the comment.

 

[Mega]

The Datum Point measurement as specified on numerous reamer prints for 6.5x47 Lapua is 0.375".

 

[Brians356]

The Datum Point measurement as specified on numerous reamer prints for 6.5x47 Lapua is 0.375".

If that's true, then it's the same Hornady bushing size as for many common cases with .473" rims. You can use anything with a 3/8" hole in it, in a pinch.

 

[Mega]

Not quite.

The .243W according to SAAMI spec's datum point is 0.400" and the reamer prints I have of .22BR, 6mmBR and 30BR are 0.350" all of which are 0.473"
rims. I haven't looked at other 0.473" like .308W.

I have not looked into these that may have improved chambers and or modified shoulder angles either to see if that changes the datum point.

As the question was asked, 6.5x47 Lapua just happens to be one I have three rifles chambered in as switch barrel, all different actual chamber reamers used.

 

[jimsr]

Thanks for the comments, .375 is the bore size of Hornady's "C" & I'll use it because I'm not sure how round I could keep the bore without the proper reamer. The 6.5x47L is a little bigger at the end of the shoulder than all the cartridges that Hornady lists on the sheet that comes with the bushings and they don't list the 6.5x47L so maybe it could use a larger bore size but I'm going with the standard. Thanks again. Jim

 

[jcampbellsmith]

The details are here - http://accurateshooter.net/Blog/65x47diagram.pdf in mm as it's a European product.

9.58 millimetres = 0.377165354 inches

I believe one of the Hornady inserts is nominally 0.375 inches in diameter, so this is the one I would use.

Regards JCS

 

[Brians356]

Not quite.

The .243W according to SAAMI spec's datum point is 0.400" and the reamer prints I have of .22BR, 6mmBR and 30BR are 0.350" all of which are 0.473"
rims. I haven't looked at other 0.473" like .308W.

Assuming you are responding to my comment about .473" rims, I said "many", not "all" (or even "most") use the .375" diameter. YMMV.

 

[Brians356]

The details are here - http://accurateshooter.net/Blog/65x47diagram.pdf in mm as it's a European product.

9.58 millimetres = 0.377165354 inches

I believe one of the Hornady inserts is nominally 0.375 inches in diameter, so this is the one I would use.

Regards JCS

It all depends on what you are trying to accomplish. You cannot rely on the Hornady system for actual headspace measurements in any case, you can only use it to log a baseline case length at some point on the the shoulder, and then detect subsequent relative changes of same, at or near the datum line. If the cartridge calls out for .375" then your measurements will be very near the actual datum line. But a slightly smaller or larger bushing will serve just as well for tracking relative changes at the shoulder caused by firing and resizing.

Example: The 6mm Rem drawing specifies .375" diameter at the datum line, but I use a bushing with a .365" opening (actually a Stoney Point "37" bullet comparator bushing) and it reveals shoulder setback after sizing quite well. But I cannot use the actual length it indicates as anything like a headspace indication - with a .010" smaller diameter, it contacts well forward of the datum line intersection.

 

[Patch700]

For what it's worth my whidden comparator for that case is .377