Please explain freebore when talking about chambers/reamers

[ogre6br]

HI
Can you guys please explain free bore in chambers and on reamers.

Was talking to a G-smith and his 30 BR reamer is a "No freebore" reamer.

What does no freebore mean?
Does the chamber finish in a sharp angle and the rifling start straight away or is there still a blending of chamber and rifling?
Is free bore and leade the same thing??

I am trying to work out a beginning seating depth and have got 2 projectiles,
one a FBHP and one a HPBT that are similar weight.
I am trying to seat everything a minimum of 50 thou above the neck shoulder join area to avoid the doughnut formed when expanding the necks up with a tapered expander from 6mm to .30 cal. I am doing this as I dont have anyway of removing the doughnut inside the necks and I dont want the pressure problems associated with projectiles in the doughnut area.

THanks

later
p

[AlanF]

P,

Looking at this reamer drawing, free-bore is basically the bore without the lands, then the leade is where the free-bore tapers from the free-bore area to full lands height.



Usually, the reamer maker will know what is the optimum free-bore for a given projectile.

Alan

[XCALIBRE]

P.
Doughnut and internal wrinkles can be
removed from the neck base after forming by carefully inserting a Wilson internal neck reamer of the appropiate diameter (normally four thou smaller than bullet dia.) which is available from Sinclair in the States. Cost is about $25 U.S. A couple of turns by hand will cut out any lumps or bumps restricting gas flow. This should be done a second time after three or four firings to clear any re growth of the brass flow. It settles down quite dramaticaly after that but should be checked periodicaly down the track. This system also assists insertion of neck turning mandrels for accurate parallel machining on a powered neck turner. Hope this helps.