? on bullet seating depth

I get those stub gauges with all my barrels. Great for determining initial seating depth, and great for measuring shoulder bump/headspace for adjusting dies. Once the barrel gets a few rounds down it, the stub doesn't work all that great as a comparator anymore, since the leade angle (and position of course) in the barrel changes with erosion - but the stub throat stays new.

- DAA
 
Just for grins, I went downstairs and got some real data to illustrate what I was talking about in regards to the comparator measurements not being transferable from one bullet to another.

For each of these bullets, the seating depth at which they are just touching the lands was determmined to the best of my ability (by polishing the bullet and observing for engraving with a lighted 10x loupe). Then, the dummy was measured with a Sinclair comparator. The rifle was a new Rem. Model Seven in .223. The measurements are relative, with the 50 gr. Vmax being "0" (a "+" measurement means that bullet needed to be seated that much longer according to comparator measurement than the 50 Vmax, a "-" measurement that much shorter).

50 Vmax = 0
40 B-King = +.024
40 B-tip = -.020
50 TNT = +.058

As you can see, the comparator measurement, for the SAME ogive to lands relationship, varied with this group of components by as much as .078. You absolutely can't transfer that measurement.

- DAA
 
Hey DAA, some rifles have taller lands and tighter bores than others. some bullets taper off faster from the ogive than others. yes the shape of the tip of the bullet could make a difference in some cases. i have compared some and never had a .078 difference. i am not saying it didnt happen to you. i am not trying to argue with you. i understand what you are saying. i transfer the rim to ogive measurements with my bullets. i take an ogive to rim measurement when i start with a new rifle and want to get close to or on the rifling. i have compared some to others and i have never had a .078 difference. i am not saying it doesnt happen.
 
In theory then if all the bullets of a particular weight and style were the same, the OAL should be able to be used then. Right?

I dont have a bullet comparitor yet, but until then, if a group of bullets are pulled from a box. Selected because they have the same measurement in legnth. One of those bullets is used in determining the distance to the lands. A second or third used to set the seating depth of the die, a couple more through to verify. OAL of all those cartridges should be the same, in theory.
Or is the next problem with this going to be that the taper on the bullets out of the same box varies too? I have no way of measuring that.

Michael I got your email checked out the site, read reread and reread, it all makes perfect sense.
Thank you.
 
davepa: I am happy to see you have got the information you needed.One point I would like to make is this. You can do all the detailed case preparation,segregation of cases by weight,neck turning,bullet seating,all the other techniques used that potentialy make your handloads capable of better accuracy.In the end you as a individual have to have the capability to shoot with a high degree of accuracy to see if any of your reloading techniques are applicable to the overall approach you have taken with your reloads.You have to have the capability to prove out your techniques.In theory Speedy Gonzalez may have the best reloading techniques ever seen and preformed at a loading bench.If he can not shoot with a high degree of accuracy how will Speedy know weather .005 or .010 is the best seating depth off the lands.Speedy may be the best neck turner ever seen at a loading bench and a great little primer pocket uniformer,however speedy has to prove out any reloading technique used with load testing.Speedy has to know his capability and his rifles capability in regard to accuracy.wish you the best.
 


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