free bore

[Link]

I searched free bore and it came up with what I call jump ?
If you have 0 free bore does the case mouth just touch the leade of the lands ?

thanks, Link

 

[SmokinJoe]

Not exactly, but that is the theoretical idea.

 

[JohnHenry]

Link, Attached FYI.

http://bisonballistics.com/articles/an-introduction-to-rifle-chambers

 

[lpreddick]

A reamer can be made "with no freebore" and you assume what is stated, but there is "hidden freebore" and if the slope of the lands is gentle(1°30) there is more distance a bullet can be seated out without significant lands engraving. A chamber length is always longer than the case length...010-.020+. Cases need trimming to leave a little space between case mouth and chamber end. The reamer cuts a 45°(I have one with a 30°) angle at the end of the chamber as it goes to the bore, adding .012-.015 more to this "hidden freebore". A 1° 30 slope is immediately cut from the lands and a non vmax bullet will seat a few thou into the bore before significant engraving. I seat .020 into lands with .002 neck tension and bullets do not self seat. I was unaware of this " hidden freebore" when ordering reamers yrs ago, so now I order them with less or none and find I can seat bullets with more in the case neck, .020 into lands and as the lands wear, I seat further out while still having good neck contact. NOTE...I shoot light weight .22 and 6 mm bullets. Long heavy bullets need some freebore to keep the bullet's base in the neck.

 

[Martin52]

I searched free bore and it came up with what I call jump ?
If you have 0 free bore does the case mouth just touch the leade of the lands ?

thanks, Link

I have a .308 target barrel (12T 0.298 x 0.3075) with zero freebore. Using the Sinclair plug, my chamber length is 2.018 and I trim cases to 2.005. I have asked myself the same question in the past (maybe I should have asked my 'smith !) so I am interested in the replies too. I only shoot 155 grain projectiles, Berger full bores and Sieraa 2156's.

Martin

Martin

 

[pahoghunter]

This is interesting, I just started a thread on another site in regards to a SAMMI spec. for freebore, I have a Savage .223 1-7 twist in which I shoot Berger 80.5gr bullets. And I was wondering if there is an ideal freebore for a given bullet weight? So I started looking for the SAMMI spec. for the .223 I don't think I saw any two that were the same. Mine is approx. .151 the fellow on the Savage forum said he has seen them as much as .225. I might call Berger today and ask some questions.