Chamber length and max case length discussions

[catnthehat]

Talking of late to several shooters about the importance of case trim length and getting several " this is important" answers from all, I was chewing the fat with a gunsmith buddy this morning , musing about different chamber lengths of my various match rifles - three to be exact.
All rifles have been barreled by top shelf gunsmiths, a Remington 600, a Musgrave target, and an RPA Quadlite.
All are very accurate, although all have higher round counts
All have .223 Wylde style chambers ( one being chambered by Bill Wylde himself) , but all vary in the actual chamber case length!
The interesting thing is, that even with a case that is overly long (1.765), none of the chambers is too short to accept it .
The bottom line at the end of the discussion was as long as the cases are consistent length and fit , a rifle can be made to shoot accurately as long as everything else is taken into consideration as far as balance is concerned, for instance , a quality barrel, action, sighting system, and an operator that knows how to shoot to begin with!
I really think we complicate some things when hand loading and shooting for accuracy.
Several accomplished SBR shooters I know only set their dies so the bolt will close with a very slight pressure , that's it- no gauges, no measuring !
That is how I have done it for many years , but many disagree with that system .
Cat

[elkhunter11]

I also adjust my die, so that the bolt just closes easily on a sized case.I don't use special tools or gauges to measure how far the shoulder gets set back.

[waldedw]

Correct me if I'm wrong but setting the die to bump the shoulder so the case chambers snuggly has nothing to do with max case length and / or trim length.

[elkhunter11]

Originally Posted by waldedw

Correct me if I'm wrong but setting the die to bump the shoulder so the case chambers snuggly has nothing to do with max case length and / or trim length.

Totally different topics.

[catnthehat]

Originally Posted by waldedw

Correct me if I'm wrong but setting the die to bump the shoulder so the case chambers snuggly has nothing to do with max case length and / or trim length.

Yes but many get too concerned about case stretch , setting back shoulders, and cases getting too long at the same time, when all are different but tend to get bunched in together. You cam buy a gauge for everything these days when most of the time they are not needed.
Cat

[Pathfinder76]

Case length is measured with a calliper. A tool I can’t imagine reloading without. Most will never have brass that is too long. Most chambers have plenty of length. In fact, this is where the carbon ring is. That space between the case mouth and the end of the chamber. But consistent brass length matters in my opinion.

Shoulder bump can be measured in more than one way. If you want to size by feel, you need to remove plunger ejectors etc. I do both. Brass, more times than not, does not fully form on the first firing so bumping that brass arbitrarily 2 thou will cause more issues than it solves. You can also get variation on that first firing. Gauges can tell you that immediately. Again, I often do both.

Just for reference, the cost of some of these fancy gauges is about the same as three pieces of brass. Others cost a lot more.

[catnthehat]

Originally Posted by Pathfinder76

Case length is measured with a calliper. A tool I can’t imagine reloading without. Most will never have brass that is too long. Most chambers have plenty of length. In fact, this is where the carbon ring is. That space between the case mouth and the end of the chamber. But consistent brass length matters in my opinion.

Shoulder bump can be measured in more than one way. If you want to size by feel, you need to remove plunger ejectors etc. I do both. Brass, more times than not, does not fully form on the first firing so bumping that brass arbitrarily 2 thou will cause more issues than it solves. You can also get variation on that first firing. Gauges can tell you that immediately. Again, I often do both.

Just for reference, the cost of some of these fancy gauges is about the same as three pieces of brass. Others cost a lot more.

And to add to the confusion even more for some, I measured some new Nosler competition brass and the 20 pieces I measured averaged 1.740 +- .001 as opposed to the new Lapua cases I measured which wete 1.750 +-.001
That is not only a pretty big difference between two brands , it is far shorter than SAAMI specs which often get bandied about!
Cat

[Pathfinder76]

I often mourn at how short new brass is.

If you have gauges you can also see brass varies wildly from brand to brand in “headspace” as well.

[32-40win]

Short brass can take 2-3 shots to reach it's final length is what I've found. I've been neck sizing the first couple of shots on new brass just to make sure, then I set the bump on the FLS die on the third sizing by the longest ones. Trim length seems to be somewhat negligible til after the second shot usually, then I'll sometimes find a few that are actually close to needing trimming, and will usually trim the works. Doesn't seem to be uncommon to find new brass that is .015-.020 short of max trim nowadays though, even after second shot.
Buying a set of case gauges like the Hornady ones is getting pricier, but, so is the brass. See a lot of first timers that have troubles that can be solved with a set of those gauges PDQ too, would save them a lot of angst, especially the ones buying bulk "once shot" stuff. If you have the dimensions off a new case unfired, an unfired factory ammo round, a fired case, as resized case, a reloaded but unfired round right off the bat, it can solve many mysteries in a big hurry, as to what direction to go, to fix issues.

[6.5 shooter]

A borescope will save you a lot of grief. Run several new un fired case into the chamber, close the bolt, feed you bore scope through from the muzzle and see how much the neck can grow till it needs trimming. (A base line) Once the case is a thou or two from the end of the "cut" chamber, trim all brass to that length. (trim every firing or two or as needed). This will also help to stop the dreaded carbon ring.

As for "bumping" the shoulder I like to have the bolt close with little to no pressure involved. This can be done by feel or with fancy equipment, but the whole reason to have the bolt close easily is so that you don't disturb the rifle in the bags. Other then that, a bit of pressure means nothing.

Remember two thou. is the thickness of a piece of scotch tape. So a cheap shoulder bump test is to have the bolt close easily without tape on the base of the case and "harder" or not at all with tape on the back of the case.

[catnthehat]

Originally Posted by 6.5 shooter

A borescope will save you a lot of grief. Run several new un fired case into the chamber, close the bolt, feed you bore scope through from the muzzle and see how much the neck can grow till it needs trimming. (A base line) Once the case is a thou or two from the end of the "cut" chamber, trim all brass to that length. (trim every firing or two or as needed). This will also help to stop the dreaded carbon ring.

I discovered the "case in the chamber and scope down the muzzle " thing a few years back when working up paper patch loads for my 40/65 Sharps, a bit by accident , actually!
Frustrated with getting paper jammed and having to clean the chamber with every shot, on castboolits forum I was told you only want no more than .002 clearance to the end of the chamber from the case mouth , and I couldn't find a case that seemed long enough to jam.

Once I stuck the scope down the muzzle to check, I was quite surprised at just how long the chamber was!
I run my cases as long as I can on everything now and disregard the .010 trim recommendation that is the norm in manuals......

Cat