DYI tool to determine oal of a pistol cartridge
Posted: 10 Sep 2020 12:40
First I have to say we are all responsible for the safety and function of our ammo that we load and this is more a learning Discovery exercise but it does provide some data that may be be useful to some. Secondly the photos you will see or how I did it today and I am sourcing a threaded nylon rod to create a dedicated tool for this purpose.
Lastly before I go on there will be a photo missing of the first measurement which is taken from a cleared and safe pistol with the Barrel in place. It will be pretty much self-explanatory but your first measurement it's taken from the muzzle end with a rod safe for your rifling to the breech face and the rod is Marked as closely as possible at the end of the muzzle. When inserting the rod to the breech face be careful it doesn't get hung up on ejector and remains as parallel as you can hold it. There will be a pic of the final mark for this first measurement and you will understand.
Next remove the Barrel from the firearm. Drop the bullet you were loading into the chamber and support it with something like eraser end of a pencil. Place the rod back through the muzzle until it contacts the tip of the bullet and again carefully make that Mark on your rod.
Using a pair of calipers measure the distance between the two marks on the rod. That will give you a measurement specific to the bullet you are loading which places the bullet in the lands and grooves of the barrel. This is not your overall cartridge length but it gives you a good starting point from which a little simple math gives you maximum overall cartridge length taking your magazine into account of course.
A little more simple math and you get a figure I consider a Target figure for reloading.
From the research I've done the offset for your bullet From the lands and grooves is between 10 and 15 thousands. . Subtract 10 thousands from the measurement you took with your calipers and that gives you a maximum oal very specific to your Barrel and Pistol. Subtract 15 thousands and you have a Target oal that will make you around a little more generic and more likely to work in other pistols you may own of the same caliber.
You should still do the plunk test in your Barrel and function test in your gun before you load thousands of rounds. Pics below and I may have to put a secondary post to get them all in.
Lastly before I go on there will be a photo missing of the first measurement which is taken from a cleared and safe pistol with the Barrel in place. It will be pretty much self-explanatory but your first measurement it's taken from the muzzle end with a rod safe for your rifling to the breech face and the rod is Marked as closely as possible at the end of the muzzle. When inserting the rod to the breech face be careful it doesn't get hung up on ejector and remains as parallel as you can hold it. There will be a pic of the final mark for this first measurement and you will understand.
Next remove the Barrel from the firearm. Drop the bullet you were loading into the chamber and support it with something like eraser end of a pencil. Place the rod back through the muzzle until it contacts the tip of the bullet and again carefully make that Mark on your rod.
Using a pair of calipers measure the distance between the two marks on the rod. That will give you a measurement specific to the bullet you are loading which places the bullet in the lands and grooves of the barrel. This is not your overall cartridge length but it gives you a good starting point from which a little simple math gives you maximum overall cartridge length taking your magazine into account of course.
A little more simple math and you get a figure I consider a Target figure for reloading.
From the research I've done the offset for your bullet From the lands and grooves is between 10 and 15 thousands. . Subtract 10 thousands from the measurement you took with your calipers and that gives you a maximum oal very specific to your Barrel and Pistol. Subtract 15 thousands and you have a Target oal that will make you around a little more generic and more likely to work in other pistols you may own of the same caliber.
You should still do the plunk test in your Barrel and function test in your gun before you load thousands of rounds. Pics below and I may have to put a secondary post to get them all in.