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Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by LR-Shooter, Jul 4, 2011.
What, exactly, does it mean when a rifle is "throated" for a certain bullet?
I am not a gunsmith, so I cant give detailed particulars, but when I ask for a rifle to be throated for a 105 A-Max (as an example); I want the bullet seated so the base of the bearing surface is just ahead of the neck/shoulder junction and the forward part of the bearing surface is just slightly back off the rifling at that same seating depth.
This may have other meanings to other folks, but that's my general interpretation of what "throated" means. Others may want a .020 jam with a VLD and same seating depth.?
SBruce, does that mean that the bullet length (seating depth) cannot be changed ie. made longer? or shorter?
No, I didn't mean that close of tolerances. I would want to be able to seat the bullet out to touch the rifling without it being 1/2 way down the neck, and likewise; I'd want to be able to seat it back a little too and not have it take up too much case capacity. I would want to be able to adjust seating depth a little both ways with that heavy bullet.
I'd rather have it too short than too long, because the throat will wear out as we shoot it. Also, If we throat it short for the heaviest bullets we intend on using, then it's still OK if we decide to try some lighter/shorter bullets. Last thing I personally want is a brand new rifle that I can't get bullets out to the rifling in. Even though I asked for it throated for 105's, I may end up shooting 80's in it too.
Again, this is just me. Others may have other preferences.
It does tend to get a little complicated.
It will depend on how the person orders the reamer or asks the throat to be cut if done by hand.
The reamer mftrs can take a case and a certain bullet and cut the reamer so the bullets ogive just touches the lands with the base of the bullet in a certain point. Some want the base of the boattail at the bottom of the neck etc.
The gunsmith can use a throater to cut a certain depth throat if the reamer is shorter to lenghten it for a longer bullet.
lightbulb Thanks guys for your help. I believe I understand now what it means to throat the rifle for a certain bullet.
Just remember to let the smith know (and he can pass on to the reamer co.) if you want to shoot from the magazine or not also.
Some combinations we can, some we cant. For a hunting rifle, I prefer to be able to use the magazine and still be able to seat bullets out close to the rifling.....another reason for a short throat.
SBruce, I appreciate the input. I begin to understand more and more as I read threads here @ LRH. Thanks.
I hope it's OK to use this thread to post my question. In the A-Square reloading manual I read that there's 2 types of throats, parallel and conical ones. It said that a lot of freebore wouldn't be a problem with light short bullets as long as the throat was of the parallel type just a thousandth bigger than bullet diameter. It went on to say that most cartridge chambers were of the conical type and that this would be why people seat bullets close to the lands for accuracy. Can somebody comment on that?
I cheated. I had my 300WSM built on one of my old Long Action Model-70's I've got ample room in the mag, & I was still able to have er throated for 200gr Accubonds, but I shoot 180's currently with a c.o.a.l. of over 3 inches. I could shoot down to 165's & not be throated too long, but if I wanted to shoot bullets that light, I'd have kept it as an -06'.
Like SBruce said,
Have it throated long enough to accommodate your longest bullet you plan to use, but not so long you can't shoot lighter ones too, if you wish.
This is good advise for a hunting rifle.
I think you did great by cheating with a long action
I probably should've had my 300 WSM done on a long action, instead of a short action with a 3.0" magazine box.
Sure, 180's will run jammed at 2.91+ and still feed in the mag, but the base of the bearing surface is well under the neck/shoulder junction and stealing powder column in the process. Maybe not much with 180's, but I can't imagine how much would be lost with the 200+ pills.
Just my opinion, but the 300WSM probably really needs to be done on a long action. Similarily the 6.5-284 only gets all it gusto by living in a long action, shooting long bullets, and having a long hallway to run down. Even though both cartridges were originally designed to shoot in short actions, we didn't have the High BC extra long bullets in those days.
I'd comment if I knew anything about that, but unfortunately I don't. I've never heard of conical vs parallel throats. Not saying it isn't so, just haven't heard of it. I'd be interested to read about/hear more about this.....