Hornady oal gauge

[mikecr]

I don't know what you're really doing or locking in on.
With the Hornady you push the case in until it stops at the shoulder(that's one datum), then you extend the bullet seated in that case till the lands stop it (that's a second datum) with it's center rod.
That's one datum too many IMO.
Then, many end up 'averaging' their results, because of all the inconsistency in measure with this approach.

I use an R-P tool myself, which amounts to the old cleaning rod method. Basically I set a collar (at the muzzle) with a cleaning rod end against the boltface. Then I set a second collar with the cleaning rod end against the meplat of a bullet touching lands. The distance between collars is COAL with that bullet.
I seat that bullet to that COAL, measure it for CBTO, and log it as touching.
Works great, very consistent.
But it's been a long time since I felt compelled to do it, as it flat out doesn't matter to me anymore. I'll do a version of Berger's seating testing, find best seating, and log & make ammo to that CBTO. There is really no reason for me to consider actual DTL. It's only real use has been in describing my seated relationship -in discussion.
I guess that's my contention here; Don't chase your tail with a hornady tool unless there is a real & compelling reason to do so.

 

['Freak]

Except for probing at ‘em and/or reading from the opposite end of everybody, you’ve described somewhat how folk would go about it using the Sinclair tool, though the Sinclair is capable of a good bit more fineness. If your methods help to keep you with that warm and fuzzy feeling then that’s all that matters.

 

[Tokimini]

There is another method to determine COAL that only requires a dial caliper and a flat spot on the back of the receiver to serve as a reference point. After a bit of practice it works fairly well. Take five or so of the bullets you want to use and measure their length. Take an average of those and this is your bullet length. Take one of those bullets, insert it in the chamber and drop it down the bore till it's stopped by contact with the lands. Measure from your receiver reference point to the base of the bullet in the bore. This is your base depth. GENTLY dislodge the bullet (tapping the rifle butt on the floor usually does it.) Finally insert an empty case in the chamber, making sure it's completely seated, and measure from your reference point to the base of the case. This is your head depth. Add the bullet length to the base depth, which gives you the measurement of the forward end of the bullet when it's touching the lands. Subtract the head depth measurement, which is the rear end of the bullet and that gives you the COAL of that round contacting the lands. It that seems a bit too complicated, just soft seat a bullet really long then chamber it. You should be able to see a faint ring where the bullet contacted the lands. To find the CBTO I disassembled my Forster micrometer seater die and measured from the base of the cartridge to where the seater contacted the bullet ogive. Since the seater die is what actually determines the COAL of the bullet I thought it would be more logical to use it's contact point with the ogive as a reference point as opposed to the lands. From there it's easy to precisely tune what kind of jam or jump your rifle prefers.

 

[mikecr]

Tokimini that's the same method as the Hornady & still relys on averages over two datums, which is still one too many.

 

[Tokimini]

Tokimini that's the same method as the Hornady & still relys on averages over two datums, which is still one too many.

It's not perfect, few things are, but it works for me as a starting point.

 

[lpreddick]

i once felt the frustration with the hornady device for all the above reasons. i now do as Dave Berg describes (tony boyer also.). seating a bullet in a fully prepped case .030 longer than the hornady device "suggest" as the lands touching point and chambering will engrave the ogive and will be fairly easy to see IF you rotate the bullet in 4-0 steel wool prior to chambering. this leaves a slightly dull circumferentially oriented pattern. over head fluorescent light will cause the engravings to appear black or shiney depending on rotation of the bullet. i measure to be sure the bullets hasn't been seated a bit...this will happen if neck tension is inadequate or bullet seated WAY into the lands or lands slope is sharp. if no bullet movement, seat .005-.010 deeper, polish and chamber. you can see the gradual (if lands are the common 1 degree 30 slope) shortening of the engravings until the become small. in guns shot a lot you will see rectangular engravings turn into narrow lines and then dots, showing you what lands' errosions is occuring. you can also watch 4 lands getting shorter and then there are THREE...the forth having been burned/eroded more than the other three. the process is a bit slow but may be the most accurate as you are using the prepped case and bullet you plan on shooting.

 

[michaelnel]

I have had much better results with the tool on my .308 since I started following the advice in the instruction sheet packaged with the unit. I have a 36" long 1/4" diameter hardwood dowel (69 cents at the hardware store). I run the dowel in from the muzzle end and I "sandwich" the bullet between the tool and the dowel.

I have my right hand on the dowel at the muzzle and my left holding the case in the chamber and operating the little grey plastic pushrod. I push it in, then move it back with the dowel, back and forth until I am seating it with a consistent pressure.

Then while still holding the tool body, I tighten the setscrew on the grey plunger. I push the whole shebang out with the dowel and do the measurement with the comparator on my calipers.

I usually take 5 measurements and often get exactly the same measurement for 3 of the 5, and the other two are very close. I then average them and use the average for my measured value.

 

[jsthntn247]

I have had much better results with the tool on my .308 since I started following the advice in the instruction sheet packaged with the unit. I have a 36" long 1/4" diameter hardwood dowel (69 cents at the hardware store). I run the dowel in from the muzzle end and I "sandwich" the bullet between the tool and the dowel.

I have my right hand on the dowel at the muzzle and my left holding the case in the chamber and operating the little grey plastic pushrod. I push it in, then move it back with the dowel, back and forth until I am seating it with a consistent pressure.

Then while still holding the tool body, I tighten the setscrew on the grey plunger. I push the whole shebang out with the dowel and do the measurement with the comparator on my calipers.

I usually take 5 measurements and often get exactly the same measurement for 3 of the 5, and the other two are very close. I then average them and use the average for my measured value.

I do it the same way and also get measurments within .002 of each other over the 5 time trial. The key is pushing the bullet very slowly toward the lands with the grey plunger and stopping as soon as you feel the slightess resistance.