Once fired brass case prep

[Bart B.]

Donovan asks,

To get this straight, you said in your post #17, test results from 600 & 1000 yards. With that and your last post, I take it your saying 1/4 to 1/3-MOA at 600yds and 1/2 to 2/3-MOA at 1000yds.
Is this correct?

Yes, I included short range tests. 10- to 20-shot test groups. All shot between sunrise and 6 am in stable atmospheres.

Also, expand on what rifle and setup was these case length tests shot with?

26" to 30" Hart, Kreiger or Obermeyer barrels, Winchester 70 or Paramount trued actions, 155 to 200 grain bullets, 308 and 30-338 Winchester unprepped full length sized cases, RWS primers, DuPont powders, wood or synthetic stocks. Rifle on front and rear shot bags full of rice slung up prone, Weaver T20 scope in Tasco rings.

 

[dmoran]

Yes, I included short range tests. 10- to 20-shot test groups. All shot between sunrise and 6 am in stable atmospheres.

26" to 30" Hart, Kreiger or Obermeyer barrels, Winchester 70 or Paramount trued actions, 155 to 200 grain bullets, 308 and 30-338 Winchester unprepped full length sized cases, RWS primers, DuPont powders, wood or synthetic stocks. Rifle on front and rear shot bags full of rice slung up prone, Weaver T20 scope in Tasco rings.

So I take it your input on 0.010" of case neck length variation is based from over the course of several years, rifles, barrels, and setups. Not from actual results or tests specifically conducted for case neck length variation, or like your advising others to conduct in your post #15.

 

[Bart B.]

So I take it your input on 0.010" of case neck length variation is based from over the course of several years, rifles, barrels, and setups. Not from actual results or tests specifically conducted for case neck length variation, or like your advising others to conduct in your post #15.

Cases with different neck lengths perform the same wherever they are fired. It wasn't worth time and material to see if a fixed neck or case length might be more accurate.

Sierra was getting a little better accuracy with unprepped cases with the same spread in neck lengths testing bullets shot from rail guns. My own human variables enlarged my accuracy tests; don't know how much. I didn't have a rail gun or machine rest to eliminate my impact on accuracy.

 

[L W P]

Cases with different neck lengths perform the same wherever they are fired. It wasn't worth time and material to see if a fixed neck or case length might be more accurate.

Sierra was getting a little better accuracy with unprepped cases with the same spread in neck lengths testing bullets shot from rail guns. My own human variables enlarged my accuracy tests; don't know how much. I didn't have a rail gun or machine rest to eliminate my impact on accuracy.

Which worked better, the longer case length or the shorter?

 

[Bart B.]

Which worked better, the longer case length or the shorter?

I could not tell the difference. Neither did Sierra; they trimmed them back every 10 or so firings. They didn't weigh powder, just metered it into resized then primed cases with a 2 to 3 tenths grain spread.

 

[L W P]

I could not tell the difference. Neither did Sierra; they trimmed them back every 10 or so firings. They didn't weigh powder, just metered it into resized then primed cases with a 2 to 3 tenths grain spread.

Too many variables to me for a.010" test to work.

 

[Tony1320]

So would you guys run once fired Palma brass through the Giraud trimmer just to chamfer / deburr the cases or just leave them?

 

[L W P]

I don't trim every time because when I measure, after 2 firings, the brass hasn't grown more than .002"-.004". Usually after the 3rd firing I trim them all even. I just don't think that a person can shoot any different with a .005" case length difference. I should say I know that I can not anyways.

 

[dmoran]

So would you guys run once fired Palma brass through the Giraud trimmer just to chamfer / deburr the cases or just leave them?

Myself if I had a Giraud, I'd likely run my match brass through every couple cycles, to maintain a constant length and square case mouths.

Unlike Bart, my own seating force and targets say that equal neck lengths and square case mouths to be creditable to consistency in accuracy, with less fly'er aspects. Particularly believe square case mouths is vital.

Good Luck

 

[Dos XX]

So would you guys run once fired Palma brass through the Giraud trimmer just to chamfer / deburr the cases or just leave them?

Tony, you are shooting .308 Palma brass, so I am thinking you are a Sling or F/TR shooter?

How are you cleaning your brass? If SS tumbling, I would definitely trim every time you tumble. It takes out the peening on the end of the neck. If not, you can figure out how much your brass grows every resizing and keep it a safe distance from the end.

That said, myself and most of the F/TR shooters I know that have Girauds trim every firing. It is almost too easy to trim with it to not do it.

 

[Tony1320]

Tony, you are shooting .308 Palma brass, so I am thinking you are a Sling or F/TR shooter?

How are you cleaning your brass? If SS tumbling, I would definitely trim every time you tumble. It takes out the peening on the end of the neck. If not, you can figure out how much your brass grows every resizing and keep it a safe distance from the end.

That said, myself and most of the F/TR shooters I know that have Girauds trim every firing. It is almost too easy to trim with it to not do it.

You are correct, I am shooting FTR

I'm tumbling with rice to clean my brass

 

[L W P]

Myself if I had a Giraud, I'd likely run my match brass through every couple cycles, to maintain a constant length and square case mouths.
What part of the brass does the Giraud axis from, the shoulder or the body? A friend of mine has one ,but I've never seen him use it.

 

[L W P]

I'll have to look it up on the U TUBE.

 

[dmoran]

What part of the brass does the Giraud axis from, the shoulder or the body? A friend of mine has one ,but I've never seen him use it.

I don't have one either, but in there video's it appears to me they axis from the case shoulders.

 

[L W P]

I don't have one either, but in there video'd it appears to me they axis from the case shoulders.

Thank you, I'm trying to find more info videos now. If off the shoulder, then the only problem would be consistency of the resizing first. Else every inconsistency in the shoulder angle would result in different lengths being cut. Right? Just like my WFT.

 

[dmoran]

@L W P
I agree.... shoulder set-back consistency would be key for trim length consistency.

 

[HomeSlice]

I hate trimming, and only do it when I must. When I do trim, I trim the whole batch of brass at the same time, for consistency. This is about every 4th firing for me.