Case length trimming consistency

[ron]

Uniform case neck tension is a big factor for accuracy. For my 223 match grade ammo I use Winchester brass. Winchester brass will shrink my groups to about half the size compared to LC brass. With 77 smks my 20-in barrel service rifle will shoot quarter minute groups. I length check my cases and only trim them when they are too long. I think the largest factor for accuracy is bullet selection. Not just the bullet weight but the bullet manufacturer. I am getting my best results with Sierra match Kings.

 

[DizzyJ]

Uniform case neck tension is a big factor for accuracy. For my 223 match grade ammo I use Winchester brass. Winchester brass will shrink my groups to about half the size compared to LC brass. With 77 smks my 20-in barrel service rifle will shoot quarter minute groups. I length check my cases and only trim them when they are too long. I think the largest factor for accuracy is bullet selection. Not just the bullet weight but the bullet manufacturer. I am getting my best results with Sierra match Kings.

Neck tension and the consistency thereof is a huge contributing factor to getting smaller groups. I thought about going back and modifying my post after I'd posted it but was too busy (or lazy) at the time to go back and add to it.

I've had my coffee now so I'm a little more ambitious. But not TOO ambitious.

 

[Spitpatch]

Assuming we speak of a singular lot of cases matched as to brand and times fired/how sized, and preferably having been all fired with the same load (no "hot" portion of the lot of brass along with a portion loaded "cooler"), and to be fired only in the same rifle:

Trimming and chamfering should be performed on a new lot of brass, and should not need another trim until book max case length is approached in the lot.

Random samplings of case length from the lot after firing should show that since the case was treated identically at every stage of its usage, case length remains quite uniform in that lot of brass. (They all "stretch" equally because the stretching forces are equal).

The emphasis is on consistency within the lot, rather than conforming to any book-recommended "trim length".

 

[Koda]

ah ha, this is good its coming out now... I didnt bookmark it, but somewhere recently I read about neck tension being important and while turning necks is way above my experience level right now it made me think of uniform case length.... it seems to me if one case is say .01" longer than another the longer one will have slightly more neck tension (all other things being equal). How critical that is case to case was my question but from what Spitpach is suggesting its more about uniformity in the lot sample which makes sense to me.

 

[Mikej]

ah ha, this is good its coming out now... I didnt bookmark it, but somewhere recently I read about neck tension being important and while turning necks is way above my experience level right now it made me think of uniform case length.... it seems to me if one case is say .01" longer than another the longer one will have slightly more neck tension (all other things being equal). How critical that is case to case was my question but from what Spitpach is suggesting its more about uniformity in the lot sample which makes sense to me.

It's likely the .010" longer you speak of would take you past the "trim too/max length" range of .010".

 

[RVTECH]

It might be different if I was using one of those fancy case trimmers.

I'm not so sure about this. I hear of some using 'those fancy case trimmers' and still report inconsistent (albeit minor) differences in trim length.

I have never used anything but the Lee trimmer and have never had an issue. A thou or less difference in length I doubt is going to have a significant impact on accuracy.

As previously mentioned charge weight, proper seating depth and as I said, consistent and accurate seating of the bullet are some of the major factors.

 

[pharmseller]

I don't full length resize unless the case doesn't fit anymore. No joke. FL resizing is a PITA, time consuming, and it overworks the brass. Heck, most of the time I don't tumble, either.

Ditto on trimming. FL resizing tends to lengthen the neck more than anything else does, so neck sizing only (nso) solves that problem. If the case doesn't chamber it gets trimmed using a Little Crow WFT.

The guys who said neck tension and runout are spot on. Even powder charge variations don't contribute much to changes in accuracy, in my experience.

I keep track of which rifle owns the brass, and separate by times fired. When I run out of a "generation" of brass I process the next generation all at once. Check a bunch of empties to make sure they chamber, tumble (maybe, my brother likes shiny brass), nso (which deprimes as it sizes), re-prime on the upstroke, into the box with a label telling me the date, rifle, and generation (4x, 5x, etc).

Nso creates very consistent neck tension. I use Lee collet neck sizing dies. Fast and easy.

I rarely shoot past 550 at game, out to 950 at steel. I do pretty okay. Load development is key. I'm not happy if I can't get .6" or less, consistently.




P

 

[pharmseller]

I reload for 10 (I think) rifles, too.



P

 

[Spitpatch]

If the case doesn't chamber it gets trimmed using a Little Crow WFT.

Assuming I interpreted this right, I would avoid "doesn't chamber" as my maximum case length indicator. An overly long case may well chamber quite easily even though the case mouth is impacting the leade to a small degree. With a bullet subsequently seated and the complete cartridge chambered, this impact may be exacerbated, resulting in inconsistent neck tension at the least, and an unsafe pressure situation at the worst. Maximum case length book specs are to be respected.

I am likewise a fan of sizing ONLY to the degree the brass operates satisfactorily in its assigned gun. HERE, "doesn't chamber" is indeed a good indicator.

"Firm" chambering can be tolerated (perhaps desired) in a target rifle. Hunting rifles require a more strict sizing regimen for flawless reliability in the field and such ammunition should allow for effortless chambering.

Recently, a big Hub-Bub spread like wildfire in the benchrest circuit, claiming "Full Length Resizing" is what all the champions do. (Complete with on-the spot interviews).

Turns out, what they're really doing is what I call "Partial Sizing". Indeed, they ARE altering the brass wall moderately in the process, but shellholders are not impacting the die to cam-over (my definition of "Full Length Resizing"): something I do only when the ammunition must function in multiple guns, and as @pharmseller relates, needlessly hard on brass.

 

[Caveman Jim]

I'm not so sure about this. I hear of some using 'those fancy case trimmers' and still report inconsistent (albeit minor) differences in trim length.

I have never used anything but the Lee trimmer and have never had an issue. A thou or less difference in length I doubt is going to have a significant impact on accuracy.

As previously mentioned charge weight, proper seating depth and as I said, consistent and accurate seating of the bullet are some of the major factors.

NYET. My Giraud drill press mounted trimmer delivers 1.750" +\- 0.002 every time. I check often trying to thwart this phenomenon but have been unsuccessful at this point in time.

 

[Mikej]

Turns out, what they're really doing is what I call "Partial Sizing". Indeed, they ARE altering the brass wall moderately in the process, but shellholders are not impacting the die to cam-over (my definition of "Full Length Resizing"): something I do only when the ammunition must function in multiple guns, and as @pharmseller relates, needlessly hard on brass.

I realized after my first full length sizing with a shoulder bump to match the factory PPU loaded 6.5 Swede that I didn't need to bump the shoulder. Trimmed, proper length brass, chambered with the slightest hint of resistance on closing of the bolt. Made me feel all warm and cozy that my brass was snuggled up to everything in the chamber. And would be worked very little upon future firings.

 

[ma96782]

Up To You.

I suspect that reloading for Uber Accuracy vs The Plinker......they will each likely follow their own set of rules.

Aloha, Mark

 

[dangerranger60]

I'm not so sure about this. I hear of some using 'those fancy case trimmers' and still report inconsistent (albeit minor) differences in trim length.

I have never used anything but the Lee trimmer and have never had an issue. A thou or less difference in length I doubt is going to have a significant impact on accuracy.

As previously mentioned charge weight, proper seating depth and as I said, consistent and accurate seating of the bullet are some of the major factors.

The difference between your Lee trimmer and most of the others is that Lee trims based on total case length and most others trim based in the mouth of the case to the shoulder that the case head spaces on.
I'm another that believes that for most shooters just having your cases at a consistent length will make consistent ammo. I trim to just less than max length but the exact length is not as important as having them all the same.
Lee trim guides are cut to make cases somewhat under max length. If I were going to use a Lee set, I would buy a dedicated cutter for each guide. That way you are not changing the length each time you change calibers. the length can change based on how tight the guide is screwed in. By having a cutter for each guide once it is tight it never moves.
One other thing about Lees trim guides, you can adjust them for length by putting shim's under the guide to trim longer. or using a file to trim the pin to make them cut shorter. Good Luck DR

 

[DizzyJ]

Assuming I interpreted this right, I would avoid "doesn't chamber" as my maximum case length indicator. An overly long case may well chamber quite easily even though the case mouth is impacting the leade to a small degree. With a bullet subsequently seated and the complete cartridge chambered, this impact may be exacerbated, resulting in inconsistent neck tension at the least, and an unsafe pressure situation at the worst. Maximum case length book specs are to be respected.

I am likewise a fan of sizing ONLY to the degree the brass operates satisfactorily in its assigned gun. HERE, "doesn't chamber" is indeed a good indicator.

"Firm" chambering can be tolerated (perhaps desired) in a target rifle. Hunting rifles require a more strict sizing regimen for flawless reliability in the field and such ammunition should allow for effortless chambering.

Recently, a big Hub-Bub spread like wildfire in the benchrest circuit, claiming "Full Length Resizing" is what all the champions do. (Complete with on-the spot interviews).

Turns out, what they're really doing is what I call "Partial Sizing". Indeed, they ARE altering the brass wall moderately in the process, but shellholders are not impacting the die to cam-over (my definition of "Full Length Resizing"): something I do only when the ammunition must function in multiple guns, and as @pharmseller relates, needlessly hard on brass.

I always considered full length resizing running the case up into the die till the shoulder got bumped just enough to allow for reliable feeding, not cramming over on the shell holder. It seems full length resizing can apparently mean different things to different people.

Camming over on the shell holder will give different results for different people depending on many things including the height of the shell holder (which can vary in and of itself).

 

[Movie Man]

How much does variations in case length affect accuracy? Do you only have to trim it when it approaches max, or should they always be trimmed to all be the same length?

Glad I'm not the only one wondering about case length and how it effects things.

 

[Koda]

Glad I'm not the only one wondering about case length and how it effects things.

ha, at first I thought this was your thread...

yeah, I looked into this a while ago too. Concluded anything inside saami spec is fine just be consistent. Now I trim to the max -.005" to account for my own inconsistencies in trimming.

 

[Movie Man]

ha, at first I thought this was your thread...

yeah, I looked into this a while ago too. Concluded anything inside saami spec is fine just be consistent. Now I trim to the max -.005" to account for my own inconsistencies in trimming.

I've really enjoyed learning from both of these. Think we're both wondering the same thing and on a similar path.

 

[Koda]

I've really enjoyed learning from both of these. Think we're both wondering the same thing and on a similar path.

I think so. All my handloads are for hunting. I strive for the tightest group possible but so far I average around 1.25" moa. good enough to hunt.

 

[Caveman Jim]

All my .223/5.56 get trimmed to 1.750", all of them. It leaves out any doubt that consistency is best for chasing accuracy. I'm not a bench rest shooter but I want all my ammo to be the best that I can make it.

If you think you make the most accurate ammo, put it on a concentric gauge and you will really be surprised as I was.

 

[ma96782]

Next thing you know......the question will be.....

Is it worth it, to measure each powder drop (to the last trickled granule)? Or is straight out of the hopper, "good enough"?

Aloha, Mark