Overall Cartridge Length versus Ogive to Case End Length

[tpcollins]

I'm somewhat of a newbie to reloading and I try to understand everything possible on something that can go boom in my hands. For all of my .243 loads so far, I measured Overall Cartridge Length on every cartridge and recorded them in my log. I also measured and recorded the distance from the ogive to the case end as well. Being familiar with statistics, I found much more consistency in my measurements in the ogive to case end whereas there was considerable variations with the overall cartridge length. I attributed this variation due to the inconsistencies with the polymer tip lengths.

I'm waiting for my .204 nose piece for my comparitor to arrive but I've estimated the back of a 32gr Nosler BT has about a .040" boat tail/champer so to seat a minumum one bullet length for good contact, I want to insert at least .244" of bullet into the case - as long as the overall length fits my magazine. Does this procedure make sense or do I have things bass-ackwards? All I ever read is COL, OCL, OAL, whatever the term but no reference about the ogive measurement. Thanks.

[ryutzy]

I'm not exactly sure what you are asking, but yes the ogive to case head/end is the most accurate way to measure your loaded rounds. It is this measurement that you use to correspond with the distance to your rifles lands. The bullets tend to vary slightly from base to tip and this tends to be normal, particularly with sharp nosed bullets. This is why it is more important to measure from the ogive to case head/end to make sure that you truly have the length that you want in relationship to the lands. COAL should be used more as a reference as to what will fit in your particular guns magazine. I am shooting an AR in .204 and I cannot load longer than 2.260 and still have my gun cycle properely. My .243 loads with 75 grain Vmax COAL is 2.680 and this is having the ogive of the bullet jammed slightly into the lands. As far as having the bullet seated into the case, most people say one WIDTH of the bullet should be used as a guide for seating depth into the case. One bullet width deep into the case if you know what I'm trying to say.
What loads are you using for your .243? I'm shooting the 75 grain vmax with 46.4 grains of H414 seated into the lands. Speed is 3560 fps. I've been playing with Superperformance and it appears that I'll be getting more speed out of it, but I'm still playing around with it.

[tpcollins]

Thanks ryutzy - I'm on the right track then. It just seems in the "favorite load" thread only the COAL measurement was listed which is secondary to me as long as it fits in the mag - the ogive distance is what I interpreted as more important.

(My .243 Ruger shoots the 70gr Nosler VT the best with 42.0gr of Varget, 62gr Grenades ok, I have some 75gr V-Max loaded but haven't shot them yet. In measuring the 75gr V-Max bullet lengths only, their measurements had the most variance - both tip to base as well as ogive to base . The Noslers are the most consistant with the Grenades somewhere in between).

[ryutzy]

No problem, and hey I know what you meant, but just so you dont get confused. COAL is the overall length of the case only. OAL is the overall length of the entire loaded cartridge. At least this is the way that I understand it and yes some people use them interchangeably.

How fast are you shooting those Noslers? I've stuck with the 75s just because of their higher BC. This bullet is flat wicked on coyotes and flat rocksem. I'm sure the 70 Nosler will be deadly also. My gun has a 1:9 twist and I wish it had a 1:12 as I think I could increase my speed a lil with the slower twist. 1:12 will still stabilize the 75s as long as you boot em out there fast enough. I cant wait to get my .243 AI and really boot em out there fast.

[Joe O]

When working up loads, and shooting groups,I always sort my bullets with a comparator.I have found even match bullets to be as much as .015 difference.I sort them to within .002 +/-,then vary the seating to get the distance I want,off the lands.You're on the right track.