Was thinking about seat depth and pondering over the affects of it as a whole. Without getting too scientific if possible, should we look beyond the fact that it has an affect on exit timing which will affect the load tune. Is this dependent on time of travel down the bore or the amount of bullet (length) actually held by the case neck (neck tension) or both ? How about case capacity and pressure relations ? Are we also tuning these parameters as a side affect and are those more a part of the total tune than most of us think about ? Or maybe not thinking about it ? Looking forward to your thoughts.
Howdy, Bill !
You posited some pretty good questions. That does not mean however, that I have pretty good answers !!
Many shooters here don’t have a method or computer program to tell them things like bullet exit timing. Just as… many don’t have a chronograph, or borescope; et al.
For these shooters, the discussion will take place w/o inputs from some or all of those devices.
Jam or no jam aside, “ neck tension “ is important to varying degrees for differing rifles. Neck tension has to work well with the chosen neck wall thickness…. and also the chamber clearance for the neck area & OD of the loaded cartridges. Not too thick neck walls, and….not too thin. Get the neck wall thickness you want figured out, and then find which amount of neck “ squeeze “ shoots the best ( using neck size bushings as example ). Once while doing range work, I was unable to get the bullets to put holes in paper 100yd. My friend noticed a splash in his pond to the Rt of the sight line; right after I took shot. Come to find out, I had failed to size the necks on the loads I took to his range that day. * I had my range reloading gear with me… pulled the bullets…. sized the necks for .001” of squeeze…and reseated the bullets. Immediately thereafter, the gun not only shot groups….. it happened to shoot good groups ! And all with just .001” of applied neck sizing. Aberration or not, the experience was not lost on me !
For me and my loads… my guns, I have always remembered what NBRSA Hall of Fame’r, world record setter; and world-class riflesmith Fred Sinclair told me back around
1976: start load development w/ the bullets seated to be .002” off the lands, and proceed from there. I will admit that I am predominently a groundhog shooter, and some-times accuracy contest participant….
I have only had 5 custom stainless barrels ( all from Tier 1 manufacturers ) chambered for my use; all of those for wildcats I designed. I have invested in a couple of state of the art actions, stocks; and proven benchrest triggers. I shoot Weaver T-36 scopes that have been 2X or 2.5X “ boosted “…. scopes proven in benchrest contests of the past.
I use good dies, and consistent powder “ measures “ / meters. And like many others,
I endeavor to do my best during reloading, try to stay vigilant in my bench manners; and shoot safely. I mention all this because, after 50years reloading for and shooting accuracy rifles….. .002” off the lands has given me the best results in 3 different calibers.
*** Probably near meaningless to most others here ***, but that was still the result that range work showed me…. after playing with the load variables in-ernest, looking for THE best combinations. As a result, I have not and don’t now shoot w/ bullets jammed
( other than when I experimented w/ my “ .35 Remington Rimless “ wildcat ). See pic…
I have shot cartridges that had their shoulders “ bumped “ .001”, while at-the-same-time not also having touched the powder charge, neck tension; or distance from the ogive to the lands at all…. and the loads still shot great ! Hmmm….
Not a whole lot was said here about barrel length, in regards to your questions.
For things like short range 6PPC style benchrest, barrels are mandated to be a certain length and taper; to make allowed rifle weight per class. For a shooter not limited in that fashion on chosen barrel length, a long ( longer ) barrel can allow a shift in the powder burn rate range to use of a “ slower burning “ powder. That might also drive an associated change in the primers that help loads group best. THIS is perhaps more of a contributor to achieving accurate loads than the other contriibutors you cited ( IMHO ) .
More of a contributing factor on a gross scale, than seating depth say.
In my load development work, I try to make an informed powder choice; for the barrel length and bullet wt I have chosen for any given caliber. I first carefully find the safe max charge wt for the select powder, THEN incrementally reduce charge weight until best grouping is demonstrated. As I intimated above ( so far ) I have not had to do a whole bunch of seating depth adjustments over the years. I also have not “ chased the lands “ ( but hey….. that’s just me ).
I also have had to do precious little neck size bushing change outs. And again over the years, I have settled on .010” neck walls as my preferred thickness; for all calibers I shot
( .358” caliber being the largest ).
I DK if any of that was insightful ?!
With regards,
357Mag
