Big throat '06

[JDL]

I have a .30'06 that has a throat which runs .3135". I hesitate to call it a throat because the rifling starts at the end of the mouth and tapers for .6" to the nominal .308/.300" but, at the end of the chamber the grooves are 03135". I have a 314299 mold that casts .314" and will seat normally in an unsized case. The unsized case neck measures .340" but, after seating the boolit the neck is .341".

I started to load up some test rounds but, there's a nagging feeling that the case won't have enough room to expand and release the boolit. This might cause permenate dissassembly of my rifle, not to mention certain parts of my body. Your thoughts please? -JDL

[Bass Ackward]

The unsized case neck measures .340" but, after seating the boolit the neck is .341".

JDL,

IMO you will just have to get the neck dimension in the chamber to know for sure. And this is something that you don't want to trust my guestimate.

Options are: You can turn your necks or ream. This will cut the loaded measurement so that you are sure if you don't want to risk an incorrect measurement.

Or you can go to another bullet design where you can size smaller (say .311) and reach out until you touch something.

[JDL]

JDL,



Or you can go to another bullet design where you can size smaller (say .311) and reach out until you touch something.

Bass, That's what I've been doing with the 31141 and average accuracy for 9 groups is only 1.9" at 100, which I may have to live with. I was attempting to fill up the throat to see if accuracy would improve but, didn't want to do anything I might regret. Thanks -JDL

[45 2.1]

Test your larger boolit in a fired case neck. Remove any vestige of crimp by flaring the end of the neck slightly. Hold the larger boolit in your fingers. If you can slide it in to proper seating depth with your fingers alone, you should be fine. When fired, the case neck will expand and shrink back about 0.001" which is the minimum clearance amount you need for the case to release the loaded boolit. Any tighter than the above test would involve using a smaller boolit or neck turning.

[Bass Ackward]

Bass, That's what I've been doing with the 31141 and average accuracy for 9 groups is only 1.9" at 100, which I may have to live with. I was attempting to fill up the throat to see if accuracy would improve but, didn't want to do anything I might regret. Thanks -JDL



JD,

Remember, that a large part of accuracy can come down to bullet fit too. With a long screaming taper like you have, I would say that a Loverin design of any number would be a classic in that at .311 diameter. Just seat one forward until it stops.

I and my guns always like the 311467/07. in situations like this. But it could still be load. I checked my records and found some pretty nasty remarks about the 31141 in 06s. Best load was 31 grains 4198 sized to .309 just in case this helps.

[slughammer]

Do a pound slug and measure the chamber neck.

Trim some fired cases to a nominal dimension and measure them. Fill fired cases with lead up to about 1/2 of the neck. Cast a couple of slugs out of soft lead. Wrap a 1/4 drill rod with tape about every 5". Insert slug in lead filled case and chamber. Insert drill rod and pound on it until the soft lead boolit expands to fill the chamber neck, the throat and the lead. Repeat as necessary until you get consistent results. (you may need to unlock the action and then hit the rod to get the round and bolt to retract.) This is a great way to gain a permanent record of what your chamber looks like, pound slugs tell you a bunch. I recommended the brass trimming and measureing so you can get an idea of chamber length.

If you only want the chamber neck diameter and its a bolt action, you can use some swaged 38's. Drive them in from the back with a wooden dowel. Mark the dowel, and then use the rod to knock the slug out. If you didn't go deep enough, do another and go past the mark. This method may require a little less "feel" to get a good diameter than the pound slug.

[9.3X62AL]

JDL et al--

I've now had 2 Winchester M-70/670' s in a row that had .311" throats, one a pre-64 and the other a post 64. Like you, I was concerned about neck clearance on firing, and did the test that 45-2.1 recommended. In both rifles, I had loose slip-fit. I further confirmed this bit by slugging the case neck portion of the chamber with soft/unalloyed lead Lyman #358430's and comparing that finding with that of boolits of .311" diameter loaded in cases. In both instances, I had clearances of .0025" to almost .004" depending on case make. Safe, in other words--no need to ream or turn.

Just another thing that cast booliteers have to mind that shooters of the red-coated boring bullets never worry about--unless they have tight-throated benchrest chambers.