throat freebore diameter at what point is it to tight.

[Julien]

Over the past few weeks I have been scratching my head wondering what the optimum throat diameter should be.
I cut a chamber in a 223 then throated it for 90's and found the bullets going in to throat having resistance, this was a new throater that was .2245 but I believe it didn't cut that size.It took 2 more passes with the throater at a higher rpm to clean it out for the bullet to slip in without resistance.

Match reamers and throaters have tight tolerances and I cant help but wonder if a little bit more clearance wouldn't benefit those finicky harder to tune rifles.
Some of my reamers produce easy to tune every time rifles and some don't , my feeling is that it has to do with the throat being to tight .

Any thoughts or past experiences ?

 

[riflewoman]

Re: throat diameter at what point is it to tight.

Bullet diameter +.0005 to bullet dia +.0025.

 

[Scott Harris]

Re: throat diameter at what point is it to tight.

Freebore that is the same diameter as the bullet or a smidge bigger(+.0005) is considered by some to be a key ingredient to an accurate chamber because it helps ensure consistent, straight alignment of the bullet into the rifling. I think it is a very good thing.

 

[Alex Wheeler]

Re: throat diameter at what point is it to tight.

,0002 over actual bullet shank. What diameter do your good reamers cut vs your picky ones? I believe your right about the fb diam being the key.

 

[JRS]

Re: throat diameter at what point is it to tight.

It's possible the throater dimensions are not correct

 

[Julien]

Re: throat diameter at what point is it to tight.

,0002 over actual bullet shank. What diameter do your good reamers cut vs your picky ones? I believe your right about the fb diam being the key.

As of yet I haven't measured what size holes they cut but most of my match reamers have a throat between 3 to 5 tenths over what bullet diameter should be at least that what the print states.
One of my 308 reamers seems to make a more consistent gun if my throater is used while my 22 throater cuts way to tight imo.

Some of my reamers have cut super accurate rifles every time while some never do other than when throated and the reason for this thread.

Over the years I have accumulated quite a few reamers and I'm finding the larger throats seem to be easier to tune not to large but between .001" .002" , a lot of my match reamers are to tight I think but they came that way.

accurately measuring a hole needs good tooling that most of us are not equipped with , I suppose I could grind some gauge pins in my tool and cutter grinder and get a pretty good idea what sizes are being cut though.

 

[Alex Wheeler]

Re: throat diameter at what point is it to tight.

Starrett small hole gauges work well. The print means nothing and the bullets need to be measred as well.

 

[Canadian bushman]

You can buy tenth pins. Whichever one goes +.0001/.0002 is your size.

I imagine, optimally, the freebore should at least be whatever the average deviation of your bullets are over nominal?

I would think a few .000x bigger is better than smaller?

 

[billlarson]

Re: throat diameter at what point is it to tight.

It's possible the throater dimensions are not correct

ESP. IF IT`S A PTG.........

 

[carlsbad]

If the barrel is stainless, it is hard to take a .001" cut. Stainless work hardens and the tool doesn't grab. If your throater was at all dull, that makes it worse. Your new throater may have dulled on the work hardened stainless, especially if the high speed passes got hot. It is possible your throater is cutting an undersized hole.

--Jerry

 

[jsthntn247]

Over the past few weeks I have been scratching my head wondering what the optimum throat diameter should be.
I cut a chamber in a 223 then throated it for 90's and found the bullets going in to throat having resistance, this was a new throater that was .2245 but I believe it didn't cut that size.It took 2 more passes with the throater at a higher rpm to clean it out for the bullet to slip in without resistance.

Match reamers and throaters have tight tolerances and I cant help but wonder if a little bit more clearance wouldn't benefit those finicky harder to tune rifles.
Some of my reamers produce easy to tune every time rifles and some don't , my feeling is that it has to do with the throat being to tight .

Any thoughts or past experiences ?

For the 90's, you should have left it alone when it was tight.