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jaykchan · March 18, 2017, 11:54 AM

I am trying to measure the OAL of the 8mm Mauser cartridge with the bullet touching the land. I am doing this to figure out the suitable OAL of my hand load. The problem is that I have used three different methods and they give me three totally different measurements. One of the method gives me two significantly different measurements depending on how I position the measuring instrument. I am very confused. I would like to hear your opinion to learn what has gone wrong.

Some background info: I find that the extreme spread (ES) of fps from my hand load is very wide (can be as large as 160 fps of ES). I am trying to figure out what causes this large ES. I have ruled out powder weight variation and neck tension variation have anything to do with this problem. Now I am trying to see if OAL has anything to do with this problem.

First method: I started with seating the bullet quite long, and then tried to chamber the round and close the bolt, and kept seating the bullet into the case until I could close the bolt. Unfortunately, this resulted with the bullet seating very long. It was so long that I worried if the bullet might become cock eyed when I chambered the round from the magazine. I don't keep the measurement because it was so long that it was not usable.

Second method: I seated a bullet into the case loosely and long, and chambered the round slowly and closed the bolt. The bullet should be stopped at the land, and it was pushed inside the case. I inserted a long wood dowel through the muzzle slowly until it touched the tip of the bullet, and I made a mark on the wood dowel. Removed the round and closed the bolt. Inserted the long wood dowel until it touched the face of the bolt. Then made another mark on the wood dowel. The distance between those two marks was the OAL measured using this method, and this happened to 3.162". Strangely this measurement is very close to the OAL of factory round. At this point, I was very confused because I expected the result to be longer than the OAL of factory round. Therefore, I bite the bullet and ordered the Hornady Lock-N-Load Overall Length Gauge with a Modified 8mm Mauser Case that fits the Hornady LnL OAL gauge.

Third Method: I used Hornady Lock-N-Load OAL gauge. This time I found two significantly different measurements. If I rotated the gauge in a way that the thumb screw was facing up or facing left, the measurement would be significantly shorter than all other measurement: approximately 2.97". On the other hand, if I rotated the gauge in a way that the thumb screw was facing right, the measurement would be like 3.165" (that is very similar to the result that I got using Method # 2). I had tried multiple times, and the result were the same.

Would you please tell me why the measurement can be vastly different?

Thanks.

March 18, 2017, 11:54 AM	#1
jaykchan Junior Member Join Date: April 7, 2013 Posts: 7	Inconsistent Measurement of OAL I am trying to measure the OAL of the 8mm Mauser cartridge with the bullet touching the land. I am doing this to figure out the suitable OAL of my hand load. The problem is that I have used three different methods and they give me three totally different measurements. One of the method gives me two significantly different measurements depending on how I position the measuring instrument. I am very confused. I would like to hear your opinion to learn what has gone wrong. Some background info: I find that the extreme spread (ES) of fps from my hand load is very wide (can be as large as 160 fps of ES). I am trying to figure out what causes this large ES. I have ruled out powder weight variation and neck tension variation have anything to do with this problem. Now I am trying to see if OAL has anything to do with this problem. First method: I started with seating the bullet quite long, and then tried to chamber the round and close the bolt, and kept seating the bullet into the case until I could close the bolt. Unfortunately, this resulted with the bullet seating very long. It was so long that I worried if the bullet might become cock eyed when I chambered the round from the magazine. I don't keep the measurement because it was so long that it was not usable. Second method: I seated a bullet into the case loosely and long, and chambered the round slowly and closed the bolt. The bullet should be stopped at the land, and it was pushed inside the case. I inserted a long wood dowel through the muzzle slowly until it touched the tip of the bullet, and I made a mark on the wood dowel. Removed the round and closed the bolt. Inserted the long wood dowel until it touched the face of the bolt. Then made another mark on the wood dowel. The distance between those two marks was the OAL measured using this method, and this happened to 3.162". Strangely this measurement is very close to the OAL of factory round. At this point, I was very confused because I expected the result to be longer than the OAL of factory round. Therefore, I bite the bullet and ordered the Hornady Lock-N-Load Overall Length Gauge with a Modified 8mm Mauser Case that fits the Hornady LnL OAL gauge. Third Method: I used Hornady Lock-N-Load OAL gauge. This time I found two significantly different measurements. If I rotated the gauge in a way that the thumb screw was facing up or facing left, the measurement would be significantly shorter than all other measurement: approximately 2.97". On the other hand, if I rotated the gauge in a way that the thumb screw was facing right, the measurement would be like 3.165" (that is very similar to the result that I got using Method # 2). I had tried multiple times, and the result were the same. Would you please tell me why the measurement can be vastly different? Thanks.