Free bore question 6 mill.

[sdeering]

The 6MBR reamer I have seems to be cutting a longer free bore than is printed on the reamer. .080 is what is stamped on it. I am getting more like .220. I just re cut the chamber.

If I drop a bullet down the chamber (barrel off) measure and do some math I get about the same.

At what point on the reamer, dimension wise, would you call the end of the free bore?

The bullets I am using are .343 maybe .2432 at the largest.

I am guessing .2425 should be close.

There is no way I can even get close to the lands with 60g sierras. A used 1-14 barrel I am trying this out on.

Thanks for any advice.

Stephen

 

[Leeper]

In spite of having been around this stuff for some time, I'm still not entirely clear on the perfect definition of "freebore". In general, it refers to the "jump of the bullet as it leaves the case before it contacts the rifling. With this in mind, I consider "freebore" to be that portion of the throat which is bullet diameter or greater. On the other hand, I consider "throat length" to refer to the length of the whole throat down to bore diameter. So, when I refer to a .135 throat, I'm speaking of the whole thing.
Ream a short piece of barrel just to where the neck starts to cut. The you will be able to easily see and measure your freebore/throat length. Turn a gauge which is .243 in diameter to gauge the length of the parallel section. Regards, Bill.

 

[guntech]

I think of free bore the same way as Bill...

You can also take a barrel stub and insert the reamer to where the throat starts to cut and observe how far out the neck still is and measure that distance...

 

[sdeering]

They say a pick is worth a thousand words.

Measured hear I get .245 not too much of a concern or is it?

This is aprox. .080 from where the brass ends. My brass is 1.550.
measures .2445 no .243 bullet is going to touch hear, unless a reamer will cut a smaller dimension. Maybe a worn out one?

This is where I measure .243 on the reamer it gives aprox. .210" from the end of the brass to this point.

Ya think the reamer is marked wrong? I read on 6MBR .080 free bore is about middle of the road as far as bullet length. But the .210 measurement has me stumped.
Thanks for the help guys.
Stephen