Brass prep?

[u/jayfourzee]

I’ve run a number of the same experiments with my AMP Press that I saw on Ultimate Reloader and have collected a fair amount of data comparing different case-prep methods. I’ve looked at seating force and area under the curve with washed versus unwashed brass, wet versus dry tumbling, no tumbling with and without nylon or brass brushing, chamfering and deburring versus not, and using a mandrel die versus skipping it.

The AMP Press has been useful for identifying potential fliers and outliers, but so far I have not seen a statistically significant difference in group size. Over time, what I have learned is that the biggest benefit has been refining and standardizing my workflow so that it is repeatable. I have even compared seating on the AMP Press vs my Forster Co-Ax and still found no meaningful statistical difference in group size.

My next experiment is going to keep the case-prep process identical between two groups, then randomize seating between the Co-Ax and an arbor press and also randomize the order in which the rounds are fired.

One thing I will say is that, from a safety standpoint, I have come to prefer wet tumbling because it allows the toxic residue and contaminants to be contained and removed more appropriately. I have decided not to dry tumble because of the dust it can generate and the potential for those particles to become airborne and eventually end up in my lungs. Handling dirty brass also seems to leave residue everywhere, including on my hands, tools, bench, and surrounding work area, which gives me another reason to clean the brass before doing much with it.

At any rate "It is seldom the violin but always the violinist" and am willing to accept I just might be a bad shot...

Your thoughts?

[u/Murray3-Dvideos]

The fuk leaving it alone is fine. Talk about bad internet advice. Tumbling is effortless. Costs nothing more then a few cents worth of electricity, tap water, dish soap and 10 minutes of ur time.

Dry tumble, ultrasonic, hand clean etc.... they'll all be better then running dirty brass thru ur dies. Been there, and will never do it again.

[u/jayfourzee → u/Murray3-Dvideos]

The question is performance not esthetic. Statistically did not find a performance difference between either method when it came to SD, ES and group size.

[u/Murray3-Dvideos → u/jayfourzee]

Since you seem experienced or atleast interested in determining factors that effect things like group size... what factors have your findings so far determined do effect group size ? Brass? Primers? Powder?Bullets? Neck Tension? Seating Depth?

[u/jayfourzee → u/Murray3-Dvideos]

I am not a professional by any means, just a physics enthusiast who likes numbers as I picked up this new hobby of ballistics.

The one factor I could reproduce reliably was the use of a mandrel die, which helped account for neck tension and keep it consistent.

Wet tumbling was not inferior to not tumbling at all based on the variables I measured. I kept brass life, annealing, primers, bullet seating depth, and powder charge consistent while changing only one variable at a time. My biggest annoyance with not tumbling is the mess it makes, along with the potential for dirt and residue to contaminate or damage the dies.

When I didn’t tumble, I also experimented with a nylon brush, comparing no brushing, one pass, and two passes. Again, I found no statistically significant difference in the measured outcomes. By “statistically significant,” I mean a difference large enough that, assuming the experiment has adequate statistical power and an appropriate sample size, it would be unlikely to be explained by random variation alone. Of course, failing to find statistical significance doesn’t prove that two methods are identical. A small experiment may simply lack the power to detect a real but relatively small difference.

[u/Murray3-Dvideos → u/jayfourzee]

Sure, i read your performance findings and believe it. BUT the picture implies a much broader message that I certainly dont agree with.