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Best seating depth measuring tool?

DngBat7

Silver $$ Contributor
What’s currently the most precise (accurate), piece if equipment for measuring seating depth of loaded cartridge. I know there is the Redding instant indicator, which seems great in theory to be able to do this with a press. Some may consider not benchest standard I guess. Then I say the Davidson seating depth checker (from benchrite) that attaches to your calipers. Any others? What does everyone use.
 
I use the Sinclair comparator, that attaches to my calipers.
I seat with the L.E. Wilson chamber seater, so there isn't really any difference in seating depth, to start with.
 
Does anybody know if the hornady comparators touch the ogive of the bullet where the lands of the barrel typically touch?
 
X-47B said:
Does anybody know if the hornady comparators touch the ogive of the bullet where the lands of the barrel typically touch?
Click to expand...

No they don't touch the bearing surface of the bullet. They touch on the ogive somewhere before the full diameter of the bullet.
 
I have sinclair and hornady comparators. The measurement is only relative and not absolute. But once you establish your measurement then they are helpful in determining the optimum seating depth. there is another method called the wheeler method that is very useful in some circumstances
 
Maybe not the "best" but an inexpensive and effective tool is the Frankfort Arsenal tool. It's provides a starting point but because of variations in ogives even within the same box (i.e. lot) of bullets seating depths can vary a few thousands.

I guess it depend on how precise you need to be. I understand that competitive bench rest shooters have to eliminate as many variable as possible but for me being a precise varmint and predator hunter my main objective is to keep the bullet from jamming into the lands but also finding a COL that gives me the best groups. The Frankfort tool does that for me.

Depending on the amount of free bore in a given rifle, I seat no closer than .010" to the lands to allow for variations in bullet ogives. On some rifles I've found that they group best with quite a bit of "jump" especially my Remingtion 700's. Sierra wrote an article about this several years ago explaining that some rifle shoot better with more jump.
 
X-47B said:
Does anybody know if the hornady comparators touch the ogive of the bullet where the lands of the barrel typically touch?
Click to expand...

Both I have are .010" smaller than the diameter of the bullet. That's close enough for seating. Once you find the distance to the lands and set up a test round, that gives you the jump you want, then you have a good measurement to use as long as you use the same bullet. Sometimes bullets vary from lot to lot. Just use the came comparator insert because they can vary from one to the other. Your measurements will be specific to yours.
Measure.jpg
 
One thing you have to understand. What they call the ogive of a.bullet is not the point where the curve starts and the bearing surface stops. The entire curve from bearing surface to tip is the ogive. Different bullet comparators are going to hit that curve at different points. The seater stem on your seating die will hit at a different point. As long as you always use the same comparator and seating die this is not a problem. What is a problem is some bullets have inconsistent ogive curves. Hunting bullets.and cheaper bullets not so consistent. Premium target bullets you should find very consistent. If the curve varies from bullet to bullet then you will be scratching your head wondering why base to ogive isn't consistent. Lots of.reasons for.inconsistent seating depth. This is one to keep in mind
 
NOT LIKELY
bores vary
you want precision for your bbl, have a stub from your bbl made in to a Hornady like tool.
it does not matter, it's a reference measurement not a bore specific measurement. it is to be repeatable, that's all
X-47B said:
Does anybody know if the hornady comparators touch the ogive of the bullet where the lands of the barrel typically touch?
Click to expand...
 
Seems like theres a fair amount of variance in bullets, better ones just have less. Ive made a basic type "tool" to measure COL at contact. I use a drill rod thats an easy slide into the barrel. I cut the ends square and break the edge. I cut a piece of 1/2" aluminum rod into 2-, 1/2" lenghts, Drill a slip fit hole for drill rod on center in each. Drill and tap side of aluminum piece for thumb screw.
Bolt goes in the rifle, drill rod in bore to contact with boltface. Slide both aluminum pieces firmly to muzzle, set thumbscrew on most distant piece. Remove bolt, use rod guide to align bullet with throat and hold in contact with lands. Hold it all together and set second aluminum collar on muzzle and tighten set screw. Measure the distance between the aluminum collars to get COL at contact with lands. Repeat with several bullets to get a "good" average COL. Need to do that due to variance in bullet tips and some variance in contact area of ogive.
 
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