This keeps nagging me. When i measure coal i seat the bullet in the cartridge than measure with my calipers. i put the caliper on the tip of the bullet and of course the base. for example i use 2.800 for .308 sierra 168 gr hpbt. so i get it close lets say 2.794. so every few i check and i keep getting different lengths so i keep playing with it. now i relize it is the ogive that really matters as the tip really never touches the lands right?? i never have any problems doing it the way i am doing it but how do you get a consistant reading with your caliplers. i guess the reason my lengths change is the tips are not consistant. am i ok to go the way i am going or is there a better way to do it? so the coal is the tip of the bullet to the base. just does not make sense unless i am missing something. if the tip does not touch why does it matter. the widest part the ogive is what really starts touching at some point right?
Measuring COAL
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gamestalker
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Since the seating die seats off the olgive, all your bullets are only going to be as consistent as what the olgive location is. And most bullets unless they are expensive match grade will be +/- .010" off at the ogive anyway. The measurement you take off the tip of the bullet is only going to be a ball park number as well.
I used to drive myself crazy years ago when I first started reloading until I realized how inconsistent OAL measurements are when measuring off the tip, and, that olgives are also inconsistently located too. That is when I learned how to using the lands as my OAL guide, as follows. Soot a round (no powder or primer) bullet with a candle and seat it so it touches the lands. begin setaing deeper until it just clears the lands. Then just seat it .010"-.020" deeper, lock the die down, and begin loading. This is where finding the sweet spot for your rifle begins, as well, the fun of custom hand loading for a particular action.
GS
I used to drive myself crazy years ago when I first started reloading until I realized how inconsistent OAL measurements are when measuring off the tip, and, that olgives are also inconsistently located too. That is when I learned how to using the lands as my OAL guide, as follows. Soot a round (no powder or primer) bullet with a candle and seat it so it touches the lands. begin setaing deeper until it just clears the lands. Then just seat it .010"-.020" deeper, lock the die down, and begin loading. This is where finding the sweet spot for your rifle begins, as well, the fun of custom hand loading for a particular action.
GS
You purchase what is called a comparator. Several different types out there, just depends on what you want to spend.
The idea is that you seat to the lands, and use the tool to measure cartridge base to ogive...that's max length (unless you're jamming into the lands). Then seat back however far you need for accuracy or reliability.
One model, available from Sinclair, looks like a nut with different diameter holes in the flats. You put it over the tip of the bullet and measure from the cartridge base to the flat opposite the bullet. See the image below.
Another version is made by Hornady and has caliber diameter inserts that you can swap depending on what diameter bullet you're loading. It clamps onto your calipers so you don't have to hold it while using it. Looking at the image below, the comparator is the red item clamped on the calipers on the right. The red stem on the left is another tool, an OAL tool. That tool uses a threaded case in the same caliber as your gun and you can insert it in your gun and push a stem inside the case forward to push a bullet into you lands, then using a set screw, lock it down to measure your max length. As an example, numerous companies manufacture 165 grain 30 cal bullets...all have different dimensions. IME, Nosler is long for weight....so if you need to know max loading length using a Nosler 165, you install your threaded case on the OAL tool, drop a 165 in the mouth and insert the tool into your chamber. Then you push the stem forward, pushing the bullet into the lands. Lock the set screw and use your comparator to measure your max length off the ogive. When you change bullets, you need to re-measure max OAL...because all bullet profiles are different.
Both tools are cheap and allow you to accurately measure OAL off the ogive rather than the bullet tip.
SEE THIS VIDEO
The idea is that you seat to the lands, and use the tool to measure cartridge base to ogive...that's max length (unless you're jamming into the lands). Then seat back however far you need for accuracy or reliability.
One model, available from Sinclair, looks like a nut with different diameter holes in the flats. You put it over the tip of the bullet and measure from the cartridge base to the flat opposite the bullet. See the image below.
Another version is made by Hornady and has caliber diameter inserts that you can swap depending on what diameter bullet you're loading. It clamps onto your calipers so you don't have to hold it while using it. Looking at the image below, the comparator is the red item clamped on the calipers on the right. The red stem on the left is another tool, an OAL tool. That tool uses a threaded case in the same caliber as your gun and you can insert it in your gun and push a stem inside the case forward to push a bullet into you lands, then using a set screw, lock it down to measure your max length. As an example, numerous companies manufacture 165 grain 30 cal bullets...all have different dimensions. IME, Nosler is long for weight....so if you need to know max loading length using a Nosler 165, you install your threaded case on the OAL tool, drop a 165 in the mouth and insert the tool into your chamber. Then you push the stem forward, pushing the bullet into the lands. Lock the set screw and use your comparator to measure your max length off the ogive. When you change bullets, you need to re-measure max OAL...because all bullet profiles are different.
Both tools are cheap and allow you to accurately measure OAL off the ogive rather than the bullet tip.
SEE THIS VIDEO
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The one use for calipers without a comparator is to ensure your rounds fit in the mag ... other than that the bullet tips are so variable that the measurements are ballpark at best.
I haven't found measurements to the ogive to be as variable as indicated above but, I only use match bullets (Nosler, Sierra, Hornady, Berger) ... perhaps common plinking/hunting bullets are that variable even at the ogive.
/Bryan
I haven't found measurements to the ogive to be as variable as indicated above but, I only use match bullets (Nosler, Sierra, Hornady, Berger) ... perhaps common plinking/hunting bullets are that variable even at the ogive.
/Bryan
jwrowland77
Member
Definitely need a comparator. I use to drive myself crazy trying to get consistent OALs when I first started reloading and I couldn't. The bullet tips vary hence the reason for inconsistent OAL measurements. Once I bought my Hornady comparator, I was finally able to get sleep. 
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