COL length

ok so I'm definitely gonna do CBTO variations with my first batch of reloads once my new caliper, comparators, and case gauge come...:).

I figure I can do without the OAL gauge since I would want to use MY cases anywaysm, not a modified case.

FWIW what's the threading on the OAL gauge so I can possible tap and drill my case?

oh and what's the spacer for in that pic?
 
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Nobody getting best accuracy with center fire rifle ammo crimps bullets in case necks; it adds another variable to the bullets release force needed to push it out of the case and deforms bullets unbalancing them. Properly sized case necks grip seated bullets the most uniformly. Best accuracy often happens with little neck grip at all. Lee's rifle case crimp-and-grip theory's been debunked for decades; some people still think the world is flat.

And they properly full length size their fired cases; the benchrest folks quit neck sizing some years ago. That makes the case neck better centered on the case shoulder; critical for best accuracy.
 
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Mendozer,

You can use the comparator to measure the Overall gauge adapter case and then your cases as sized to find the difference. You can, as you suspect, make your own, and I think Hornady has continued the service Stoney Point offered before they sold the gauge design to to Hornady, of drilling and tapping a case you send to them. It's a 5/16"-36 tap, which is UNS (UNified Superfine) which isn't common to hardware stores. Amazon has the lowest prices I could find without looking too hard. It needs a letter L tap drill. I would drill the hole with a 9/32" drill first, then clean it with the letter L drill to avoid the hole coming out oversize from drill wobble.

I got one of those taps fifteen or twenty years ago, but I've only used it for odd cases. Instead, I set up seating by measurement of the bullet ogive to case shoulder distance. That measurement may be unnecessarily precise from an accuracy standpoint, but it avoids the effect of case length differences, so it makes Hornady's adapter case give you the same result as your own cases would if you drilled and tapped them.
 
Remember that every 10 to 30 shots, the rifling erodes away .001" increasing the bullet's distance it jumps to the rifling. Good ammo will not have any significant accuracy loss over 1/10th inch of rifling erosion and bullet jump amounts. Good reloads with the same OAL will shoot sub 1/2 MOA at 100 yards throughout that much erosion. So, trying to get a precise starting point for a round's OAL is not all that important.
 
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awesome thanks so much for all the valuable information. Just got my caliper in today from Anytime Tools. It's the stainless one on Amazon with the#1 selling status.
It's a solid quality stainless tool. Measured exactly .308" around my bullet several times. Winner!
 
Buy better tools, learn to use them properly.

Buy even better tools, learn to use them properly.

Buy specialized tools that fit your requirements for accuracy, learn to use them properly.

Apply to reloading, think before you do, measure twice cut once, all good rules.

Think thru what you want to accomplish, then research the best path to achieve your desired results, and don't be afraid to ask questions.

And don't believe all you read on the Internet - get several hardcopy sources first for direct comparison.
 
OK so I got an un-sized case, crimped the neck a bit for tension, but a bullet in, and chambered it 7 times, measuring the CBOL using the comparator and got and average of 2.720" (minus the comparator length of course).

So using Berger's recommendations, I would start some loads at .10, .50, .90, and .130 off from 2.720"? Then hone in from the most accurate of THOSE by .005 in either direction a few times for a second round of ammo.

I noticed some grooves on the bullet, so I'm assuming that's RIGHT ON the rifling.
 
The groove marks are right on to slightly into the bore. That's fine. Just keep in mind that, as compared to a bullet jumping 0.030" into the lands, the pressure from the same powder charge will be about 20% higher. So you want to work only with bottom starting loads when you are touching the lands, then sneak up slowly, watching for smallest groups and for pressure signs. Ideally, you get to your smallest groups before you have pressure signs.

The Berger VLD's are very long and their noses taper gradually, so you have to move them quite a distance to change the amount of gas bypass that occurs around the nose before the bullet meets the throat and obturates (seals off) the bore. If you are using the Interlock with its smaller ogive radius, I would be using steps of 0.030" to 0.040". Once you get a clear best result, go half way to the previous and next positions and try those. If one of them is equally good, split the difference between it and the first best position you found and use that. If not, stick with the first best result you got. Then go back to powder charge tuning.

Dan Newberry's OCW method is practical for most folks tuning powder charges.
 
I used to play games with OAL to get the best groups at 100 yards at the local range.

For hunting with 270 or 7mmRM, I now seat everything at 3.34".

Hunting is more like going to war than going to the range.
 
I was planning on using the starting grains for loads then fiddle with seating to find the optimal and later adjust powder to maybe middle of the load data. I'll read through that OCW method
 
That's a good start. Unfortunately it gets complicated fast because you are indirectly changing a second variable. Changing the bullet position affects pressure and velocity, so it also affects barrel time. Thus, if a load was on a barrel time sweet spot it can be thrown off of by changing seating depth, so that a good spot could look worse, or vice versa. Stopping to tune the load at each seating depth is one way to go about it, but it involves a lot of test shooting. I usually shoot five rounds at each seating depth in round robin style, recording the resulting velocities for each seating depth I will test. A trendline plot in Excel then tells me how much to adjust the powder charge to get a matching velocity at each seating depth, and another calculation based on that information and the gun's expansion ratio gives me an adjustment of the charge for constant barrel time that is based on QuickLOAD's model results. In the end I can then change seating depths with adjusted charges and just see the effect seating depth itself actually has.

I'll publish that approach at some point later in the year, when I've further verified the calculation is working as expected, or close enough to it.
 
seems like his OCW method kind of ignores seating depth as long as it's constant. He values powder charges as more important than jump or jam
 
With all the talk of accuracy and different methods of this and that and everyone asking questions all confused and all they want is accuracy STOP thinking to hard and slow down and forget about acurracy most of the guns you have bought will need the actions tried barrels lapped and trued trigger weight reduced action bedded scope mounting systems bedded 0 cant on scope some sort of harmonic distortion arrestor or repeater bolts centered in action tolerances reduced to .0001 of a inch then after all that forget it all the only thing you need for accuracy is the ability to repeat the same shot over and over and over that's it simple just replication of one shot but do it 1000 times then move your scope so the point of impact is where you want it !!!!!!! Repeat the same shot anything you can think of that will give you the replicated result will have one hole with 1000 bullets gone through it putting your bullet .010 off the lands give you accuracy no is the result repeatable yes that is accuracy repeatability when a variable varies you must change something to get you repeatability back so shoot straight remember repeated results will get you a big trophy
 
With all the talk of accuracy and different methods of this and that and everyone asking questions all confused and all they want is accuracy STOP thinking to hard and slow down and forget about acurracy most of the guns you have bought will need the actions tried barrels lapped and trued trigger weight reduced action bedded scope mounting systems bedded 0 cant on scope some sort of harmonic distortion arrestor or repeater bolts centered in action tolerances reduced to .0001 of a inch
Click to expand...

Or you can just buy a SAVAGE :D

Remember that every 10 to 30 shots, the rifling erodes away .001" increasing the bullet's distance it jumps to the rifling.
Click to expand...

Wow , That's crazy you just posted that Bart . I just checked my NEW max COAL after firing 2,300-ish rounds through my 308 . Turns out I gained .063 and using your numbers I should have gained .073 . That sounds pretty close to me . At first my new numbers did not seem right . How ever I did seat some loads out .040 more and the rifle shot like new again :). I'll add that my load in close to minimum charge so I was not concerned about pressure issues .

Do you guys know if 178gr A-Max is a VLD ? The ogive seems different then 175gr smk . maybe they are a hybrid ?
 
Metal god, that formula for leade erosion's an average. It also varies a bit with the powder's heat rating. And of course with pressure and the amount of powder burned per shot. .308's get about 30 shots per .001" of erosion.

My .264 Win Mag long range rifle eroded about .100 inch after only 640 shots; it's formula turned out to be .001" for every 6.4 shots. For my .30-.338 Win Mag, it's about .001" for every 13 shots.
 
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JJ72, what's a harmonic distortion arrestor?

Never heard of it. Does it stop (arrest) all barrel whipping and vibrating?
 
did my preliminary OCW testing today. I stopped at 58.4 grains and that group was the best at .744" grouping.

I'll do another round of smaller increments.
58.4, increments of .1 up to 59 (Hornady lists 59.9 as the max)
 
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