Precision Reloading On The Cheap....
by
MikeG 
There are a number of excellent tools available to reloaders today which not only contribute to the precision of the ammunition we create, but avoid unsafe conditions like excess resizing of brass (which can lead to case head separations, for example). A tool in this class that I'm fond of is the RCBS Precision Mic which can be used to set up resizing dies, measure the 'jump' that a bullet will have to the origin of the rifling, and also check headspace on bottlenecked cartridges that have been fired in a particular gun.
While the Precision Mic is really a bargain considering the functionality, the cost does add up when many different cartridges are reloaded (around $40 each at this writing), and sometimes there is a need for a quick solution which can't wait for the UPS truck, or for a less-common cartridge that the tool may not be available for.
So, the purpose of this article is to show a quick way to create a simple yet effective gage using some rather common tools / materials. The subject of the test was the .35 Rem, chosen for being somewhat less common, yet also having a slight shoulder which can make die setup tricky. The first picture shows a digital caliper, a 13/32" drill bit, a fired .35 Rem case, and an old rusty nut scrounged up from the scrap pile. Folks, it doesn't get much cheaper than that! (Note that a dial caliper would work just as well, or even a vernier; the digital caliper just happened to be handy and all reloaders should have a caliper that measures to 0.001.")
The .35 Remington case measures approximately 0.425" at the shoulder (per cartridge drawings in Hodgdon #26 reloading manual; chamber dimensions may vary slightly) and about 0.384" on the outside of the neck (again per that manual). What we need is a gage that will slip over the neck of a fired case, yet not completely over the shoulder. Midway between these two measurements is 0.406," and by coincidence, a 13/32" drill bit should measure 0.40625." Note, however, that any hole in the range of 0.390" to 0.415" would probably work as well, so it doesn't have to be exactly 0.406" for the purpose of this gage.
However, it DOES have to be drilled straight and true; this means using a drill press with a vise, and (not shown) both marking the center of the intended hole with a center punch, and also using smaller drill bits to gradually increase the hole size rather than trying to drill it with the 13/32" bit from the start. As an example, start with a 1/4" (quarter inch) bit; then move up to 3/8," then finally the 13/32." Drill bits will almost never cut the exact hole desired. They will usually run slightly oversized, but the pilot holes help a great deal in that regard.
Once the hole is drilled, it can be lightly deburred with a twist of a standard case deburring tool, then a few strokes of a file across the face. To use the tool, place it over the mouth of the case, then measure from the top of the nut to the base of the case. The flat face of the nut, and the flat base of the case, should align everything so that we have a measurement that is repeatable every time to 0.001." Note that this measurement gives a relative value which means nothing except to our specific gage, but will be useful in setting up the resizing die. As the die is set lower in the press, we should be able to determine exactly how far back the shoulder is set in increments of 0.001" - plenty of precision for that operation. The shoulder can be set back 0.002" - 0.003" for easy chambering, yet avoid excess sizing which can lead to case head separation.
How critical is this measurement, anyway? SAAMI spec for headspace is normally in a range of about 0.010" between minimum and maximum. Manufacturers of reloading dies must have their products capable of resizing to less than minimum headspace to fit all standard chambers; on the other side of the coin, the rifle manufacturer would probably rather see chambers at the large end of the spec for easy chambering of all ammo. So, if a die is set up for maximum sizing, it might not be uncommon to push the case shoulder back 0.010" - 0.015" more than necessary. Brass life will not be long at these extremes.
Another obvious use for this tool would be to set up a resizing die so that brass will chamber in several different guns without being resized any more than necessary for the tightest chamber. Or, to even determine how close the chambers are cut and whether such a course of action is even feasible.
This particular tool isn't caliber specific, either - it'll work on any cartridge that the neck of a fired case will fit in the hole, and having a shoulder that is larger than the hole. So it also would work on a .30-06, a .338 Win Mag, etc.
I've even make up a bullet-seating gage for a .257 Roberts; the hole needs to be very close to 0.250" for that example, and a quarter-inch drill bit that makes a correct-size hole got the job done. If you have an industrial tool supply nearby, 'decimal' reamers which are normally available in 0.001" increments can be used to bring a hole up to exact size for that purpose and they aren't normally very expensive, $5 - $10 each typically. With some care they can be used in a standard drill press.
Not bad for some rusty scrap.....
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