280 Ackley SAAMI Head space

[roger8]

I had a 7x57 AI that the cases were getting hard to chamber after alot of firings, I started bumping the shoulders, this resulted in head separations. The real problems was that the necks had grown longer.
My point is check case length first, then if they are hard to chamber FL size next, then measure neck thickness, only then bump the shoulders. Bottom line if it ain't broken don't fix it.

 

[tnek13]

DITTO with leave it alone

 

[Lefty G-gear]

 

[BadgeNJ]

I had another shell holder for my priming tool and switched that one into the press, was able to turn the die down a little further and am getting .001 bump if I run it through twice. Just found all this out now that I have the head space guage and realize that I should have kept track of # of firings on the brass as I now know depending on number of firings they are all not expanded the same. Fired cases chamber but tight with the scotch tape, bumped cases chamber and a hair tight with the tape so looks like I am good. Question on trim length my chamber measures 2.569, SAAMI max case length is 2.525. Should the cases be trimmed to the same length or as long as they are less than 2.525 don't trim? Again thanks to all who responded very helpful and learning!

 

[whatnext]

I had another shell holder for my priming tool and switched that one into the press, was able to turn the die down a little further and am getting .001 bump if I run it through twice. Just found all this out now that I have the head space guage and realize that I should have kept track of # of firings on the brass as I now know depending on number of firings they are all not expanded the same. Fired cases chamber but tight with the scotch tape, bumped cases chamber and a hair tight with the tape so looks like I am good. Question on trim length my chamber measures 2.569, SAAMI max case length is 2.525. Should the cases be trimmed to the same length or as long as they are less than 2.525 don't trim? Again thanks to all who responded very helpful and learning!

You want to trim them all the same. Consider that when you seat the bullet, your COAL will be the same on each round but the spot where the bullet leaves the case will be different on each one unless you trim all the same. Figure out what SAAMI minimum trim length is and either trim to that or to your shortest case but not under minimum. Consistency=Accuracy

Edit: SAAMI shows 2.513" minimum

 

[BadgeNJ]

It all makes perfect sense I was looking at COAL not thinking of the above. Thanks for the help!!

 

[FEENIX]

It all makes perfect sense I was looking at COAL not thinking of the above. Thanks for the help!!

Please take no offense, but I want to reiterate consistency.

Brass trim: As @whatnext noted, you want to be consistent and trim your brass to COAL SAAMI spec - 2.513" min - 2.525" max.

Seating depth: Measure consistency on CBTO, not COAL.

Good luck!

Ed

 

[bgouin]

You don't want to use a dremel or belt sander for that, or the top will be uneven. All you do is get some finer grit sandpaper and lay it down on a flat surface and then hold the shell holder top firmly against the sandpaper and work it over the sandpaper. That gives a much better result.

I put a shell holder in my drill press (a big chuck) and clamped a whetstone on the platen. This allowed me to take off steel in fine increments. The mating surface remained perpendicular to the die. I used an old whetstone.

 

[whatnext]

I put a shell holder in my drill press (a big chuck) and clamped a whetstone on the platen. This allowed me to take off steel in fine increments. The mating surface remained perpendicular to the die. I used an old whetstone.

Brilliant!

 

[BadgeNJ]

My chamber length is 2.569 and I have brass measuring from 2.516 to 2.525, what would be the best length to trim to?

 

[whatnext]

My chamber length is 2.569 and I have brass measuring from 2.516 to 2.525, what would be the best length to trim to?

2.515

 

[MNbogboy]

My chamber length is 2.569 and I have brass measuring from 2.516 to 2.525, what would be the best length to trim to?

My personal preference is to try for the longest majority. Meaning if, in your case for instance;
If there was 42 cases over 2.521, one at 2.520, three at 2.518, 2 at 2.517 and 1 at 2.516 ..i would trim to 2.520 . The 7 culls could be sighter/foulers and most likely would "grow" into the group within 1 or 2 firings. My thought is the longer a spec neck , the less carbon build up near the case mouth end of the chamber.

Of coarse if your cases have no "majority", trimming to the shortest length is all you can do for consistency. However, most reloaders do not trim new cases until they are "fireformed" as uniformity will often change quite a bit on the first & second firings until all the body & shoulder are formed.

My .02

 

[Tulsa Reiner]

I had another shell holder for my priming tool and switched that one into the press, was able to turn the die down a little further and am getting .001 bump if I run it through twice. Just found all this out now that I have the head space guage and realize that I should have kept track of # of firings on the brass as I now know depending on number of firings they are all not expanded the same. Fired cases chamber but tight with the scotch tape, bumped cases chamber and a hair tight with the tape so looks like I am good. Question on trim length my chamber measures 2.569, SAAMI max case length is 2.525. Should the cases be trimmed to the same length or as long as they are less than 2.525 don't trim? Again thanks to all who responded very helpful and learning!

The neck length determines how long the bullet stays in contact with the brass after ignition, which affects MV.
The main point: keep your case necks consistent in length. Consistency = accuracy, as stated above.
It matters only if you are interested in long range accuracy. (one of the many things I've learned on the LR Forum.)

 

[BadgeNJ]

So even if my chamber length is longer than SAAMI 2.525 should I stay at or below 2.525?