7.5x55 Swiss - A study in brass

[Culpeper]

7.5x55 Swiss - A study in brass

I figure I should do some hunt and pecking on the key board not having much of any thing to do at the moment. Plus I was looking at the chickens doing their thing. If you can't eat them, join them is what I say. This is my journey to being a better steward of my brass, whether 7.5 Swiss or any others in the tunnel complex.

I used a .400 Hornady case comparator and my Mitutoyo caliper as my measurement tools. I am going on faith that RUAG Ammotec knows how to make uniform brass and all of the dimensions are close to being the same. The fun part, not, is setting up my testing equipment. I made sure the surfaces of the comparator and base were flat to each other by holding them up to the light and looked for any light that would show them as being canted in the calliper.

I grabbed one of my bags of 7.5x55 Swiss brass made by RUAG and measured a new case. The base to the datum line on the shoulder of a new un-fired case is 1.797 inches. The case length is 2.183 inches. So far, so good as they tell us up at the Home on sponge bath night.

Next I took my multiple times fired (Beats me how many times, some two, some three, question mark others) brass in my blue box and fired up the ol' spreadsheet. I will adjust my sizing die based on what the numbers tell me. Anyone who has reloaded ammo will already know this so this little exercise is for the rookies and casual readers of these words.

The spreadsheet revealed three cases were, 1.792, 1.794 and 1.803 at the shoulders. I don't have a guess for those. None of the brass had been annealed at the last shooting. The rest measured 1.808 to 1.813 inches. The majority is around 1.810-1.811

1.792 1
1.794 1
1.803 1
1.808 3
1.809 8
1.810 20
1.811 16
1.812 2
1.813 5
total 57

Here is what I found for case length. The trim length in several places says to cut them to 2.179 for the K31 platform. However, I am a founding member of BA, Brass Anonymous. "Hi, my name is Culpeper and I abuse brass." "Hi, Culpeper." I've never trimmed this brass. With the exception of a few pieces of .30-06 brass I neglected that part of the process. The numbers are all over the place.

2.162 1
2.166 1
2.167 2
2.168 1
2.171 1
2.172 5
2.173 3
2.174 4
2.175 2
2.176 3
2.177 1
2.178 3
2.179 8
2.180 1
2.181 1
2.182 1
2.183 2
2.186 1
2.187 2
2.190 3
2.191 1
2.192 2
2.195 2
2.199 2
2.202 1
2.206 1
2.207 1
2.230 1
57

Here ends the sad tale of my brass. The next chapter will deal with getting annealing and trimming to see if I can bring most of it back from the edge.


.

[scottz63]

Cool. Waiting for it.

[Culpeper]

The brass has been annealed and sized. I figured I would knock .002 off the shoulders based on 1.810 inches. The bottom two outliers will just have to fire formed on the next round of shooting. This seems like it may work out for me. Now to set up the Giraud trimmer. Hornady and RCBS trimmers has certain advantages over the Giraud namely the brass is held at the rims and the cutter moves towards the case mouth. So it does not matter where your shoulders are the case length will be constant. However Giraud references from the shoulder. That means your case length will be different if your shoulder length is different. I bought the Giraud for future bench rest shooting so I will have to adapt and overcome.

1.792 1
1.794 1
1.805 7
1.806 9
1.807 15
1.808 23
1.809 1
Total 57

[waterman]

If you trim a case to a desired length with the RCBS trimmer and then use the same case in the Giraud trimmer, will more brass be removed?

[Culpeper]

From what I can figure it is all dependent on how the case holder is set. Everything rides on the shoulder to mouth length data point since that becomes the fixed measurement when the trimmer is set up. It will cut until the case holder and the shoulder touch.

My problem is variance in the base to shoulder data point across the fifty-seven cases. Again, getting my processes down for future success.

[Culpeper]

Oh, the weather outside is frightful. But the fire is so delightful. Since we've got no place to go. Let it snow, let it snow, let it snow.

I just came up with that. Came up with a new word, too. Plagiarism.

I've been sitting on the Giraud trimmer for a couple of months and I decided to conquer my fear of sharp cutting things like logging saws, milling tools, butter knives and bitter cold hearted women. You get the picture I am sure.

So I set the trimmer and had a go at it. It took a few pieces to set the depth of the case plunge but I got close to what I wanted. I looked at the CIP drawing and figured I could handle length up 2.183 inches. The trimmer did a good job of trimming the brass though there was a lot of chatter while it was hacking down the brass of the longer pieces. There was almost no noise when it was taking off small amounts.. Note to all. It is tough on the thumb. Wear a light glove.

As stated it references off the shoulder. The pic shows what the trim length in the left column and the pre-trim info in the next. Overall I think this went well even though I do not have F Class or Precision Rifle grade skills.

I changed out the lock ring that came with the set with a Hornady lock ring. Set it once and forget it until I need to change it.

Column L, P, Q, and R is the related data.


.

[Culpeper]

Alrighty. I completed this phase of the process. The final part is destructive testing and data acquisition. Aw, who am I kiddin'. I'm going to shoot the heck out of this stuff and take pictures of the targets.

It'll have to wait until next week when the weather guys say we'll have a couple days of fifty degree weather.

It is almost too purty to shoot.

[Culpeper]

I was able to get to the range today. We are in a period of global warming at the moment which comes on the heels of some global cooling three weeks ago. We have 70-72 degrees today.

The distance was one hundred yards with my standard loading. I had fifty-seven cartridges so I used the seven as sighters. Then I shot five round groups and took pics except for target 2. I don't have the break of for that target. I did have a diopter adjustment on target 3. Memo to self. The W + F is not linear when adjusting windage and elevation. It is more like a zig-zag. I made a two right and one down on my final adjustment.
Now it is back to the calipers and spreadsheet for me.

[Culpeper]

More

[Culpeper]

I was firing this batch and stuffing them back in the box without an individual lookie see.

I found one that was a frog hair away from case failure, a second one starting down that road, and a dozen more with faint rings lining up on deck.

This brass is now safely in the scrap bucket and one hundred more will be prepped this weekend for fun and games. One thing is certain. I am going to track how many loads and reloads this batch will have through my rifle.

Here ends the story of 7.5 Swiss - A study in brass.

... or does it? (Cue spooky music)

Thanks for watching
.