Brass Prep Tests

You read about it...things like "if you think it makes a difference, then it probably does" Does prepping brass do anything? Why does it do something? Why do people do it. Here is a simple explanation:

The theory behind brass prepping is that it will make the numerous variables involved in the reloading process more consistently similar, thus making things more predictable. This makes sense, but what part of prepping matters the most? First, you have to ask yourself what application you are looking to use it for. Here is some applications and what is perhaps important:

Long Range: SD/ES are critical. So Neck turning is good idea
100 Yards or closer: SD/ES don't matter much. But Chamfer is a good idea at minimum

We got some brass that came from SIG's production line, that has their primer in it, so we don't know the original manufacturer of it. The bullet component was pulled, and the powder dumped out, and then the brass is bagged and sold. This is what we have. It has pull marks from the machine that holds the brass so the bullet can be pulled, as you can see from pics. But that doesn't really matter much, as all the brass was full length sized in RCBS Group A FL Sizer with an expander ball of .222. So neck tension was light. at between .001 and .002.

Here are some pics of some different stages of brass prep

Arbor Press seating Gauge

That reads about 44 PSI seating pressure

Unprepped Brass

You can see marks from machine that holds brass to pull and you can see inside of case mouth is not brushed and as it came after the pulling process

Fully Prepped Brass

this is SCBN, or Sized, chamfered, Brass Brushed neck, and Neck Turned. Look how clean inside of neck is compared to unprepped

10 Shot groups: 100 yards

Needless to say, if you frequent this web site, you know we like Benchmark powder. Its a top tier powder for shooting 100 yards with. It doesn't offer the best SD's but its nuts accurate for benchrest shooting.

Here is the KEY:

S = Sized/Trimmed to same length

C = Chamfered case mouth (inside and outside)

B = Brass brush inside of case neck

N = Neck turned (Shave neck to have consistent brass thickness)

One Shot Lube = Hornady One Shot Case Lube: Bullets soaked before loading

No prep (nothing) = These are SIG brass that come pre-primed from SIG's factory. They are from pulled bullets that are sold by a company called "American Reloading". Here: https://americanreloading.com/

** All Brass was Full Length sized using a RCBS Group A Full Length Sizer, using a .222 ball expander

***This SIG brass is very light and has huge case capacity. With primer in it, they weigh ~93 grains. That is super light, compared to Lapua which is over 100 grains with primer in it. Starline 223 Brass will give you ~100 FPS more same load, because its thicker/heavier, less capacity. ****This SIG Brass was pulled straight out of the bag from the company that sells pulled components, directly from factory.

*****In regards to SIZING/Trimming brass to length. All this brass was pretty consistent 1.751-1.754. Sized/Trimmed was 1.744-1.745

First thing we can see, is that all the groups that were Chamfered and Brass Brushed, were very similar in result.

What is conclusion?

Conclusion is....Prepping matters!

Notice the pressure (PSI) required to seat the bullet with the cases with no chamfer? More than anything else, and no prep at all, was over 100 PSI on some. It does not look like SD/ES correlate to seating pressure, but accuracy does correlate. Chamfered together with Brushed seems to be consistently good across the board. When both are present, good things happen at 100 yards.

So we can say, confidently, that if you want to:

Shoot long range? Neck turn, Chamfer, Brass Brush will be good idea. Or at least Chamfer and Brass Brush.

100 yards? Neck turning doesn't seem to matter, because SD and ES don't really matter much (within reason)

Also, coating the bullets with a lubricant or etc, DOES matter. Consistently, 20-30 FPS less when the bullet was soaked in One Shot Case Lube. But putting the case lube didn't really make a difference in the accuracy compared to not, its just lower FPS.

Seating Pressure

Take a look at the pressure (PSI) required to seat each bullet based on all the different prepping stages.

No chamfer caused some dramatic spikes in pressure to move the bullet downward. The gauge only went up to 100 PSI, but we can estimate it would be around 120 PSI range on about half of these loads.

The One Shot made it "smoother" to seat the bullets, like a more consistent pressure, noticeably. However, that didn't translate into a very big gap in seating pressure required.

Chamfer is largest factor here.

CHAMFER

transitive verb

To cut off the edge or corner of; bevel.