COAL Question/Advice Needed

[Cdixon1]

Hello. i am loading for a pva 6 dasher. I am trying to figure the oal to the lands. the method i am using to find this measurement is i took a case and put 3 slits in the neck. enough tension to hand seat the bullet, but once chambered, it is difficult to remove the bullet, so i am assuming the bullet was pushed back to the oal of the lands. i am then using the hornady comparator to measure to the ogive. i have tried 2 different bullets (105 hybrid and 75 vmax) and get 2 different results to the lands. Each bullet i did 4 measurements and there were slight variations each time.

my questions are:

1. with the variations, is this an accurate measurement? ie when measureing oal with your favorite method, is it the same everytime?
2. is it not odd to get 2 different measurements using different bullets? since i am measuring off the ogive, i would assume this measurement should be the same for any bullet?
a. if i seat the 75 gr vmax to the measurement i get for the 105 hybrid, the bolt is very stiff to close.
3. would you trust these avg's looking at the measurements below?

105 hybrid

1.7965
1.7910
1.7955
1.7930
AVG 1.794

75 vmax

1.7510
1.7460
1.7470
1.7470
AVG 1.7475

 

[winniedonkey]

Those are two totally different bullet designs. You most certainly should get a different set of results. You should treat them as totally different and not try and flip flop the results to seek one seating distance. I personally remove the ejector and firing pin and seat them long, check for bolt handle drop and slowly seat the bullet deeper. I am not good at tech explaining, others should help clarify. Good luck.

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[spife7980]

What he's describing ^^ is the "wheeler accuracy finding your lands" video. It's on you tube if you search that phrasing. My issue with the slit bullet deal is that you still push the bullet back a bit and it's a jam length and not the actual length to just the beginning of the lands. With the wheeler method in addition to the feel of the bolt dropping free I sharpie the bullet and actually also visually verify that the bullet is touching at this measurement and another .001-2 in you don't have the lands show up.

So so two different measurements are entirely possible and sometime it's big swings too when you don't think it would be. My 223 old 69 custom comp load setting places the new 70 rdf about .1 deep into the lands by the math.

The comparator is also not at at the exact diameter of the bullet where it touches the lands and has a chamfer to boot so that's really not an exact number. It's good for comparing your exact set of tools and supplies in your exact set up. Your bushing compared to your neighbors has the potential to provide wildly different readings. So each particular bullet load discovery etc has the be measured for its individual needs.

Im not familiar enough with the actual bullets your using to provide any insight into comparing where ones ogive is to the other and whether your set up is reasonable.

 

[Cdixon1]

thanks for the feedback. i just watched Wheeler's video on this method and that does make sense. i will give that a try and report back. thanks again.