How to set cartridge overall length for rifles -how I do it anyway

F

freebullet

Guest
Right or wrong I use 3 methods to get the info needed for determining col.
I'll share them here in hopes to help newbies that want to learn. The process is easy and helps get you in the neighborhood of what a specific rifle wants with one specific bullet or boolit design.

The first process works with most any rifle & is especially useful for autoloaders.
It requires the rifle your trying to load for, a dowel a few inches longer than the barrel, the bullet you want to load, a caliper, a toothpick skewer or similar & a fine tip pen or pencil.
1. Close the bolt/action on the empty gun. Insert the dowel till it touches the breach face & mark the dowel at the end of the barrel.
2. Open the bolt insert the boolit design you want to use. Make sure it's centered up in the throat and wedge it in place. I use a toothpick, popsicle stick, skewer, or whatever is handy to wedge the bullet in position.
3. Reinsert the dowel in the barrel. Make sure it's sitting on the bullet tip. Mark the dowel again again at the bore. Now remove the dowel, bullet, & make sure the bore is unobstructed.
4. Use the caliper to measure between the marks. You want to measure specifically between the bottom of the first mark (where it was marked without the bullet in the empty chamber) & the top of the second mark (from when the bullet was wedged in the throat). That is the very close approximate length it takes to put that boolit on the throat in that gun not, the col.

The second method works for most all rifles. It requires a bit more work than the first method. It uses a case gauge that you can make very easily.
rps20160123_231605.jpg
As you can see I simply made 4 slits in a full length sized case. I used a dremel cutoff wheel then a stone wheel to clean up the burrs/ sharpness. Once that's made you have an easy to use gauge that will work for any bullet in any rifle chambered for it.
1. Place the bullet in the mouth & gently slide it in the chamber. Very gently close the bolt all the way.
2. Very carefully extract the round. As soon as you can see the round through the opening in the action you must put slight pressure against the round to prevent the extractor/ejector from messing up the bullets seated position during removal.
3. Use your caliper to find out how long that catridge is when the bullet is touching the throat in that rifle. I do this about 3 times to make sure my numbers are consistent.

The third method I use pretty much exclusively for bolt action rifles. It requires an unsized fire formed case & follows the same process for method 2.

It's important to realize what the #'s we've learned mean. It is the length for that bullet only in that rifle only for the bullet to touch the throat. We need to know that # to determine where to put our col.

I hear frequently people saying- it took 25 dummy rounds to find out how long to make them. That's pure sillyness. I've never had to make more than 5 and that many is just to test feeding in autos, levers, & pumps.

Now that you have the # from the test we can figure out a col. Here are some guidelines not set in stone that I've learn through doing it.

1. For jacketed I find the best accuracy and feeding to be when the col is set fifteen to thirty thousandths of an inch shorter than the number revealed in the above tests. Seating jacketed bullets on or in the throat is not ideal and can be dangerous in some cases.
2. For cast boolits I find the best accuracy with the boolit being forced into the throat ten to thirty thousandths of an inch beyond the # from the above tests. This usually works even in autoloaders with 2r or greater boolits. With fat nose or 1r type boolits feeding usually requires the boolit be set back ten to twenty thousandths below the # revealed by the above test.

You can color the bullet with a magic marker for any of the above tests to glean a bit more insight.

You can make very accurate ammo for 1 gun this way. You can also do this test to multiple guns to make custom universal ammo by figuring out which has the shortest throat and loading for it. It will most times still give better than factory performance in the longer throated gun too.

Those parameters usually get me right where I'd like to be without a bunch of guessing or nonsense. I hope this helps someone not break their chit or have unacceptable accuracy.
 
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