Question on brass prep, please help

[Bassnbow]

A few weeks back I had a question regarding new Petersen brass compared to the Nosler brass I had been using. Just for background, I am loading for a 280 AI, fairly new rifle and not yet settled on a load (or bullet). I finally was able to get 100 new pieces of Peterson brass and loaded them about 3 grains lower than I had been using with the Nosler. I immediately had signs of pressure and had to stop and pull bullets to lower my charge.

Prior to loading the new brass and knowing I needed to get it fire formed, I only used a Sinclair neck sizing mandrel and cleaned up the necks. I didn't trim the brass yet because it was fairly consistent and I knew it would change with fire forming. I have now fired all cases one time. I have 3 cases I know are completely sized (I'm assuming) because they had signs of pressure with heavy bolt lift and extractor marks. The other cases were all fire formed with lowest powder charge for bullet being fired.

I have seen on this forum that many people recommend measuring case length to the shoulder (instead of overall case length) which is what I normally do. With the brass as it is now, shoulder measurement varies from 2.135 - 2.139 (2.139 are the cases that had signs of pressure). However the overall length of these same pieces is a much larger variable, 2.505 - 2.522. I think I need to trim the brass now for consistency, but which measurement should I work from, overall to shoulder? I do have a Forester trimmer that allows me to trim length consistently from the shoulder, but many times when brass is inconsistent (different stages of fire forming) the outcome is also inconsistent. I know most of this brass may not settle in (as far as fire forming) for a while, but with lack of components I'm trying to minimize waist.

I guess I should have said this is a hunting rifle, but I do strive to get the best accuracy possible from my loading. This gun has shown signs that it will likely shoot .5 MOA. What would you more experienced reloaders do?

Please help, I don't want to shorten life of my new brass, or waist components.

Thx Pat

 

[BoomFlop]

I would suggest checking the longer pieces in your rifle with the firing pin and ejector removed to see if they chamber. If they do not chamber, size them until they chamber without resistance and then size all the other pieces with the same die setting to minimumally size the necks.

I am not a fan of trimming based on the shoulder measurement for the same reasons you are questioning your process for. I prefer to trim with a Wilson Trimmer with micrometer. Is the case length getting close to maximum that you are wanting to trim them?

Good luck,
Steve

 

[Bassnbow]

Max is 2.525, so a few are getting near that, but most are much lower

 

[WapitiBob]

In my 7stw I have to fire twice to get full elongation of the case, both the shoulder and the oal. I trim for oal because the trimmer, Sinclair bump gage, bullet seater, and crimp die use the case head as the datum. Basically everything I do to my brass datums off the case head.

 

[Bassnbow]

Should I not trim any until shot a second or third time, even though I have .017 oal difference from shortest to longest? How much will not trimming affect my load development?

 

[ButterBean]

You need 3X firings on Peterson brass before you will see and consistency, don't trim and don't do any serious load development until then

 

[SealT5]

Should I not trim any until shot a second or third time, even though I have .017 oal difference from shortest to longest? How much will not trimming affect my load development?

@ButterBean is correct.

How many rounds are through this barrel?

 

[eshorebwhntr]

If you're not crimping as part of your process I would not worry with trimming right now. Shoot them another time or 2 until they get formed more uniformly. Once they are formed consistently to the shoulder then decide how much you wish to set the shoulder back each time.

For hunting most guys only trim once every 5 firings or so. Like I said if you decide to crimp then trimming becomes a little more important.

 

[Mikecr]

Max is 2.525, so a few are getting near that, but most are much lower

Have you measured chamber end length to know what YOUR max is?
Are you getting shiny spots on ejected case mouths?

 

[QuietTexan]

No way the brass is stable after a single firing, don't bother trimming until it is.

What die are you sizing the cases with? I'd be much more concerned with making sure you don't oversize the not fully formed cases than trim length.

Run a borescope down from the crown on an empty case closed in the chamber and look at what you've got, $5 you're still short, will be short even after the brass stabilizes, and will only need to trim to uniform the length once you really start bumping shoulders consistently. The 40* shoulder comes with a significant benefit over the old 17.5* degree shoulder.

 

[Bassnbow]

@ButterBean is correct.

How many rounds are through this barrel?

About 350

 

[nwmnbowhunter]

What were your signs of pressure?

What was your speed and what was your load?

With ADG brass I was 4 grains less then hornady brass and was getting equal speed.

 

[Bassnbow]

If you're not crimping as part of your process I would not worry with trimming right now. Shoot them another time or 2 until they get formed more uniformly. Once they are formed consistently to the shoulder then decide how much you wish to set the shoulder back each time.

For hunting most guys only trim once every 5 firings or so. Like I said if you decide to crimp then trimming becomes a little more important.

I have started crimping recently. Have seen improvement on a couple of loads not much on others. I do think it helps with consistency. Thanks for input I will hold off on trimming.

 

[Bassnbow]

What were your signs of pressure?

What was your speed and what was your load?

With ADG brass I was 4 grains less then hornady brass and was getting equal speed.

On two powders (rl23 and h4831) very heavy bolt lift and deep extractor pocket. On one the speed was very high, 3250fps, on other about 3050. Only fired one each be cause of pressure signs. Other load was about right with h4350, no pressure signs and 3000.