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Giraud Pro Trimmer and RCBS Precision Mic Question

This is a discussion on Giraud Pro Trimmer and RCBS Precision Mic Question within the Ammunition forums, part of the M14 M1A Forum category; Thanks to nf1e and a couple others, I just had to acquire the Pro Trimmer. My favorite LGS knew a guy locally who had one ...


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Old April 9th, 2016, 01:10 PM   #1
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Question Giraud Pro Trimmer and RCBS Precision Mic Question

Thanks to nf1e and a couple others, I just had to acquire the Pro Trimmer. My favorite LGS knew a guy locally who had one and wasn't into the detail required (only bought it back Jan 2016 and swears only 100 rounds of .223 run through it). Anyway, he must have messed with the .223 case holder because it was way off. In the process of getting it back into shape, I noticed a problem.

I've got the Precision Mic/Forester FL Sizing Die setup for -2 with LC 5.56 brass and got the trimmer to where I'm 1.750 +/- .005. My Wilson Case gauge says I'm good to go on shoulder. If it matters in this instance, my shooter is a Sig 556 SWAT.

The problem is that when I switch brass (by headstamp and back and forth between .223 and 5.56 brass ((not LC))), I don't get repeated trim length, actually ends up quite a bit shorter (1.745 vs 1.750).

Am I missing something or is this just a characteristic of the setup of the trimmer? My other trimmers work on base to mouth trim length while this concept of shoulder to mouth is new to me.

If this is, I probably need to look at additional case holders for the caliber and thin out my stock level of various headstamps.

Guess I'm lucky that the range I work (RO on the weekends. I try to keep the shooters from shooting at each other) at has training bays for many Law Enforcement agencies and they love to shoot LC but hate to pickup after themselves.

Heads up on the responses: Keep it simple as I'm just beginning to learn the skills and language of this hobby. Only been at it about 4 years as something to do in my retirement years (yay!!)

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Old April 9th, 2016, 01:18 PM   #2
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If you have lubed the case mouth and sized your brass before trimming using the same die set up all your trimmed brass should end up the same. Might I suggest a Wilson case guage so you can see the trim and headspace in one quick check.

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Old April 9th, 2016, 01:23 PM   #3
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nf1e, beat me to it.

IMHO, great trimmer, have all the cases been FL sized in the same die at the same time (die remained in press without adjustment)?

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Old April 9th, 2016, 02:24 PM   #4
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Hello, congrates on your purchase of the newer model with the exchangeable heads. I hope you got it at a good deal. And, you have a Wilson case gauge, I see, good....
I think the difference in oal of the case is two part. One being the characteristics of the machine (shoulder to neck design) and the fact you are using different types of brass nato and commercial in the same run. Even though you use the same die, it will work the brass different. nf1e is on, too were I'm going with this.
Even if lube is used on the inside of the neck, the case mouth walls are slightly different in thickness. This giving more or less pull tension as the neck sizing plug/button resizes/exspands the neck back out as it passes through. Pulling the shoulder out more on some of the brass and not as much on others..
So, do your trimming (in like batches) of brass, you may get better results. Do you see what I'm trying to say??? Work with the machine's design in your favor.... The +/- of .005 may get closer/smaller for you.. or I may, just be full of it.....

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Old April 9th, 2016, 02:36 PM   #5
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Going to get the Giraurd Trimmer, and then annealer next month. Dang this is an expensive hobby.

My hand trimmer isn't "cutting" it.

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Old April 9th, 2016, 03:42 PM   #6
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NWdave, which Giraud trimmer are you discussing? The Power or the Tri?

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Old April 9th, 2016, 03:57 PM   #7
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I think Bolt Action is on to the "difference". I just spent a couple of hours working some LC then decided to do some experimenting.

I lube with Imperial Sizing Wax both inside and out. NO adjustment to sizing die once it's set up to LC requirements. Went through some of the other headstamps to see what's what. Interesting. I have brand new, never been fired Winchester 223, so I started with it. Ran it through the sizing die (Precision Mic indicated it wasn't necessary). Trimmed came out to 1.7535, consistently. Using this as #2 trim standard (#1 is LC 5.56, of course). Now going through my buckets of sorted .223/5.56 to see which fall within the trimming of #1 and #2 and possibly others if it's worthwhile. Once I get the headstamps sorted out to the "standards", then I'll get additional case holders and set them up to the correct depth for each group.

Does this make any sense? To me, it works. Once the system is setup, it'll be a piece of cake. I come from an electrical/instrumentation background so getting into the "anal" side of the game is a normal thing to me. I'm not to machinists standards but I'm way beyond, close enough.

Hey, the case holders are reasonably cheap enough to get extras and set them up for each standard.

All this is prep training, got several thousand rounds of .223/5.56 to learn with, because there's a bunch of .308/7.62 (M1A) and 30-06 (Garand and several 1903s) waiting in the wings for me to get this all sorted out.

High Voltage, I don't even want to think about Annealing yet. One mountain at a time.

~Dave

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Old April 10th, 2016, 06:30 AM   #8
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Annealing is my last step really. I am going to start annealing my brass that needs it thogh.

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