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Gunsmithing headspace/freebore questions...

jeep505090

Private
Full Member
Minuteman
Oct 12, 2009
89
0
New York
Ok bear with me for this one im using really simple terms to try and discribe something very precises, when hand reaming a barrel to cut the final dimensions , is their a relationship that could theoriticaly affect the amount of freebore there actually is compared to how tight you cut the chamber simply put tighter headspace more freebore or headspace Minimum gauge +1,2,3 (looser)ect.., less freebore, the questioning around all this is if 175g smk's are jump sensitive, then a slightly looser chamber could allow the bullets to seat closer in to the lands and grooves and have less freebore to jump? hope im making sense trying not to get to technical, i know if one reloaded it would simply be easier to seat the bullets further out but just talking strictly factory ammo and if there exists a relationship, if there is could one find an in between combination of headspace and the amount of freebore to get the desired results of shooting 175s that are jump sensitive and 168s which are semingly not as sensitive, this could all be a mute point if there is no relationship either, any engineers out there? thanks for reading and the input
 
Re: headspace/freebore questions...

no. the free bore is determined by the reamer. if you ream the chamber deeper or shallower, the distance between the shoulder and the rifling will not change, only the head space will. this could make it unsafe or non-functioning.
 
Re: headspace/freebore questions...

i thought that when reaming you were removing metal all along where the blades on the reamer touched the inside of the chamber including the shoulder and neck of the case where the reamer does have the profile for both with blades ?thanks
 
Re: headspace/freebore questions...

you are. when you ream the shoulder .002" deeper, your lead also goes .002" further into the bore. the distance between the shoulder and rifling will never change unless you use a different reamer.
 
Re: headspace/freebore questions...

If you want to adjust the distance between the shoulder and the rifling you can use a throating reamer to push back just the throat. I did that with my .308 to allow 3" OALs with 208gr A-max.