Most brass too short. Trim them all?

[cgarb]

I did the same stuff when I first started reloading...nit picked primer pockets, case length, weight sorted brass....eventually I concluded that both the gun and unworthy ammo were still better than me. What dies are you using and who's concentricity gauge? I have a Hornady, it is a nice gauge. Deviation in neck wall thickness will show up on a concentricity gauge also. I have had my best loaded ammo check out off of my Forster BR die set. I consistently get better than .002" with no special procedure. All of my other dies are Lee, they make nice rounds too but usually get run out of .002/.004 area. Since switching from a Lyman turret press to the Forster Coax my bullet run out got better...to the point to where I got tired of checking them, so the gauge just sits. Hard case necks seem to be the culprit of neck run out too...like it bends the case pulling the expander ball through. Annealing and the above changes have helped me out. If I was trying to win a match at Williamsport I could get bushing dies and try to get the best neck run out and perfect tension but there is no need for it in my eyes with what I am doing. I have a 5 year old and my time reloading is getting limited so I quit being so particular...lol. Good luck tinkering.

 

[entoptics]

...What dies are you using and who's concentricity gauge?...Deviation in neck wall thickness will show up on a concentricity gauge also...

Just got an RCBS case master. Seems to be pretty solid. I use an RCBS neck sizing die, and an RCBS competition micrometer seating die.

Using a ball mic, I've spot checked a lot of cases, and even after 2 firings, the neck thickness is holding steady with minimal runout.

I usually only ever seat bullets using my ancient Lyman single stage, but often decap/size them using my Dillon. Not sure I'm willing to invest another $100+ in a new die set if the normal "tips/tricks" can't shave a few thousands off my runout.

Next step is to check my sized brass to see if the runout is from sizing, or is showing up during seating.

 

[cgarb]

Anneal case necks and try to keep the expander ball as far up in the die as possible so the die somewhat still supports the case. That's what's given me the best luck...my neck dies are the Lee collet style. I just did as you will, size a case, measure, inspect for run-out till you can narrow down and find the problem.

 

[J E Custom]

I dealt with case length for years before all Of these nice Reloader tools were available. Originally I used the Cerrosafe method to measure case/neck length in my chambers. It was the best method at the time and most people could use it if they followed the instructions. It gave good results but it was not very precise. Later I tried the commercial case length gauges but they were ground to SAMME specifications and did not represent the actual chamber of the rifle so I had to trim to make sure it was not to long.

Now that I build my own rifles, I have found that If I use the same reamer that was used for the barrel and a piece of the same barrel (Drop off) to cut a partial chamber just long enough to have 1/2 " of the case body. the shoulder and the neck it makes a perfect chamber gauge to trim by because it is an exact copy of my chamber. I simply machine the excess off the end until it is flush with the case neck chamber and this gives me an exact measuring tool based on "My" chamber. I can use a depth micrometer to measure the exact case length using the top of the gauge.

I will try to get a picture posted of the tool to show how it works for a specific chamber.

Knowing what your chamber actually Is more important than any SAMME trim length because it can keep you out of trouble.

Just more information for the post.

J E CUSTOM

 

[LongRange338]

Max SAMME length is 2.620. All brass normally will be less than Max length because not all chambers are that long.

Ideally, brass should be .010 to .020 shorter than the chamber. If you know what your chamber actually it as long as your brass is shorter you are ok. If the brass is not slightly shorter than the chamber, there will/ may be pressure problems.

It is not unusual for cases to be trimmed .040 shorter than the chamber for rapid fire matches where fouling can stop the function of the weapon.

There is an ideal trim length for each chamber and use. Then there a practical trim length and it can be significantly different.

My recommendation would be that you trim all 300 that pieces to the same length and go from there. This will give you the best consistency, and longevity of your brass. Also as you shoot it you can check to see how much growth you are getting with your loading and make adjustments if need be. Remember growth means thinning. the more growth, the more thinning. This is one reason I am an advocate of sizing only as much as necessary so the brass does not have to grow very much to fit the chamber each time it is fired.

J E CUSTOM

I've always done what JE Custom says. It may not produce benchrest groups but always safe loads that shoot better than I can shoot in the field (sub moa). It will give you a baseline of consistency without having to go to neck turning, unless you feel its necessary. As you state you are not going to be shooting this gun more than a couple of times a month, you aren't spending all of your time going to the nth degree. Personally I love to shoot the bigger rifles but the recoil will eventually cause a flinch or anticipation problem. I try to spend more time shooting milder recoiling rifles to improve my skills and then when I'm feeling a little confident grab a longer range rifle and humbling myself all over again.......
If you get to where you can shoot better than the rifle performs you can always put more into the reloading process at that point.

 

[LongRange338]

Not to bash, just informational. The MAI is Norma produced, not Lapua (according to their website). Still great stuff.

 

[entoptics]

Correct on the MAI being Norma. Got mixed up based on some research back when I bought it. From my reading, Lapua never made 300 win. There was some Lapua head stamped, which was also apparently made by Norma. It is good brass. The weight spread was great, the flash holes are drilled and required very little chamfering. Frankly, the only issue is how short they came.