Trying to put it all together

[Pirate69]

I understand that a bullet must fill the bore and it should be 0.002" to 0.003" larger than the rifle bore. I am assuming that running a fat boolit through a sizing die, 0.003" greater than the rifle bore, with a GC, will produce a boolit with the bands and the GC diameter 0.003" greater than the bore.

Question One: How does a neck sized case handle the sized boolit? Does the GC pave the way in the sized case neck and prevent the boolit from being resized to the case neck ID?

Question Two: If it does not, how do you correct this problem? Should an oversized expander plug be purchased and polished down to the correct diameter?

Question Three: How much less that the diameter of the sized boolit should the expanded plug be polished in order to maintain correct neck tension?

Question Four: Is this a valid concern and actions needed to maintain lead-free accuracy?

Question Five: I am assuming that a partial neck sizing of a case will result in the lower part of the neck being larger than the diameter of the boolit since it is not be resized and a GC being seated in the unsized area has no lateral support to keep the GC on the boolit. If homemade (FreeChex) GC are used, is there any history of these homemade GCs coming off a boolit in which the GC was sized on the bullet when unsupported?

The more I learn, the more I learn that I have a lot more to learn.

[Bret4207]

I understand that a bullet must fill the bore and it should be 0.002" to 0.003" larger than the rifle bore. .002-.003 over GROOVE size. But, not always. It depends on what the gun wants. In many case what you say is true but different guns/loads/designs/weather/rifling and other things can play a part in what will work best. IMO there is no "one rule" that works in all guns other than Fit is King. Determining what fits your gun BEST is a long drawn out series of experiments. But a "fat" boolit will usually fit better than a skinny one if those are the choices you have. .003 over groove size is about as fat as I'd normally go. I am assuming that running a fat boolit through a sizing die, 0.003" greater than the rifle bore, with a GC, will produce a boolit with the bands and the GC diameter 0.003" greater than the bore. As long as the boolit is fat enouh to start with.

Question One: How does a neck sized case handle the sized boolit? Does the GC pave the way in the sized case neck and prevent the boolit from being resized to the case neck ID? You're thinking, good! By using M-dies and annealing and watching your seating die, maybe changing dies or lapping a die, you can control that. IMO any damage done to your carefully crafted and fitted boolit, including using obturation to ensure fit, can be detrimental to accuracy.

Question Two: If it does not, how do you correct this problem? Should an oversized expander plug be purchased and polished down to the correct diameter? See above. Different alloys can also alter the risk of "squishing" the boolit in the seater.

Question Three: How much less that the diameter of the sized boolit should the expanded plug be polished in order to maintain correct neck tension? That depends. There are others here that are far more familiar with the terms and theories behind neck tension than I am, hopefully they'll chime in. In an ideal situation I would prefer that the boolit be over neck ID a slight amount, maybe .0003-.0005, but I'm not sure that's practical. And if we're crimping that brings another element into play. My suggestion is do no harm to the boolit, but what constitutes harm differs among the loader.

Question Four: Is this a valid concern and actions needed to maintain lead-free accuracy? As some of the posters here whoa re far more advanced than I have pointed out- accurate shooting doesn't necessarily mean your bore will be spotless or lead free. You may never get a certain gun to be "lead free", but it may shoot incredible groups for 50 shots despite that. It's another case of shoot and see, your gun will determine what it needs/wants to do it's best work with that particular boolit/load/alloy/lube/etc.

Question Five: I am assuming that a partial neck sizing of a case will result in the lower part of the neck being larger than the diameter of the boolit since it is not be resized and a GC being seated in the unsized area has no lateral support to keep the GC on the boolit. If homemade (FreeChex) GC are used, is there any history of these homemade GCs coming off a boolit in which the GC was sized on the bullet when unsupported? Sorry, I'm no help there.

The more I learn, the more I learn that I have a lot more to learn.


You keep thinking and discussing and asking questions. Those are good questions a lot of people never even consider. Good on you.:drinks:

[Doc Highwall]

For an example on expander plug size I size the bullets for my 308 Winchester .310" and I made the expander plug .309". For a gas check bullet I would suggest the expander plug be .0005"minimum to a maximum of .002" smaller then your sized bullet, remember the case neck will spring back slightly smaller then your expander plug. Take a case that you just expanded and try to put the expander plug in by hand you will see that you have resistance.

[MtGun44]

You should have either an M die from Lyman ( I have none) or the Lee Universal Expander
die set will substitute for the flariing function of the M die. If I understand M dies correctly,
and I may not, they also have the expander set more for cast diameters and lower interference fit than you would want or get away with when using a jacketed bullet.

Bill

[Pirate69]

MtGun44,
I do have the the Lee Universal Expander and use it to flare the case mouth.

[Bret4207]

An M die is much more of a parallel sided affair than the flaring dies. Different tool.

[Bass Ackward]

There is a difference if you need or even want case neck tension. Depends on the gun situation.

If you are talking straight sided case in a lever, yes. But you will add bullet diameter that will increase tension too. Calculate from final bullet diameter after you have tested and made a decision on what the gun wants.

If you are talking a long or large throat in a rifle, yes. But again calculate from final bullet diameter.

But if you have a bullet long enough to reach to the lands as most of mine do, then I neck ream my cases so that I don't have to use an M-die which is one more chance to cause another variable (chance for something to go wrong) and I seat out to the lands. Maybe .002 just to hold the bullet from turning, seating deep, or pulling upon extraction. If it turns with that much, then I anneal.

Bottom line is that you may have to do nothing. Or this may be the least of your worries. Cross this bridge when you come to it.

[mroliver77]

I worry about fitting the boolit to the throat. The first part of the barrel the bullet hits. As long as throat is larger than bore(I have never seen one that was not) you are good to go. I fit boolit between .0005 under to .001 over throat diameter when all is working my way. Like has been said depending on how much boolit pull you want M die can be from boolit size to -.004 for me. I like .002 -.003 tension on a hunting boolit. It is claimed by many that anything over .002 fit and brass will stretch to where you will have approx .002 anyways. I have not tested this theory yet but pretending it is gospel as using as a guideline it works for me. That puts me at using a .309 (or .310)M die spud for a .310 boolit. A little tighter has never seemed to hurt unless very soft boolits are used.
Mtgun44, the M die has a spud with parallel sides to open the neck to the desired size and also has a step to flair the case mouth when inserted fully.
Jay

[Bret4207]

I worry about fitting the boolit to the throat. The first part of the barrel the bullet hits. As long as throat is larger than bore(I have never seen one that was not) you are good to go. I fit boolit between .0005 under to .001 over throat diameter when all is working my way. Like has been said depending on how much boolit pull you want M die can be from boolit size to -.004 for me. I like .002 -.003 tension on a hunting boolit. It is claimed by many that anything over .002 fit and brass will stretch to where you will have approx .002 anyways. I have not tested this theory yet but pretending it is gospel as using as a guideline it works for me. That puts me at using a .309 (or .310)M die spud for a .310 boolit. A little tighter has never seemed to hurt unless very soft boolits are used.
Mtgun44, the M die has a spud with parallel sides to open the neck to the desired size and also has a step to flair the case mouth when inserted fully.
Jay

Or your alloy gives a bit and you wind up with a skinny boolit...

[MtGun44]

. . . . . which is NOT a good thing.

Bill