COL vs ogive

[Shooter13]

Question? What happens when you load for jump is still longer than your book recommended COL? Several measurements to the ogive from lands is 2.313, I want to run some test loads at .030 off the lands (2.283), the COL at that measurement 2.923, 9th edition of Hornady and others say COL should be 2.810. At that length to ogive they will not fit in the mag (not really worried about that). What to do? Load where I want to or go to the book, yes it has been a long time sense I loaded precision (or what I hope to be). TIA

 

[gotcha]

At that length to ogive they will not fit in the mag (not really worried about that).

Are you O.K. with shooting as a single shot? Is your bullet of choice a Tangent, Secant or Hybrid Ogive?

 

[Webster]

Question? What happens when you load for jump is still longer than your book recommended COL? Several measurements to the ogive from lands is 2.313, I want to run some test loads at .030 off the lands (2.283), the COL at that measurement 2.923, 9th edition of Hornady and others say COL should be 2.810. At that length to ogive they will not fit in the mag (not really worried about that). What to do? Load where I want to or go to the book, yes it has been a long time sense I loaded precision (or what I hope to be). TIA

The reloading manuals don't tell you what the freebore was in the rifle they generated data with or how they determined COAL. I single load and use my measurement to find touch then back off 0.005" for a starting load. My Sierra manual gives AR and bolt action data different COAL for various bullets.

 

[Shooter13]

Are you O.K. with shooting as a single shot? Is your bullet of choice a Tangent, Secant or Hybrid Ogive?

secant ogive and yes single shot is ok, the is the Hornady match 168 gn hpbt

 

[gotcha]

secant ogive and yes single shot is ok, the is the Hornady match 168 gn hpbt

Gotcha If you are confident of your "to the lands" (TTL) measurement and will be feeding as a single shot then proceed by starting at .005" off the lands (OTL) and continue in .005" increments to .030" OTL. ................ When you seat the 1st bullet at .005" OTL chamber that round to be sure of smooth feeding and also that a loaded round will eject! .............. Have you established your optimum charge weight (OCW) yet?

 

[Shooter13]

Gotcha If you are confident of your "to the lands" (TTL) measurement and will be feeding as a single shot then proceed by starting at .005" off the lands (OTL) and continue in .005" increments to .030" OTL. ................ When you seat the 1st bullet at .005" OTL chamber that round to be sure of smooth feeding and also that a loaded round will eject! .............. Have you established your optimum charge weight (OCW) yet?

No sir I have not, that is the reason I'm starting .030 off the lands with 42, 42.5, 43, 43.5, 44, 44.5 and 45, after I get that node I'll work it even closer by .002 and then I'll start working from the lands, whew! I hope I got all that right! Just got a call and I am being deployed to VA for hail damage (I'm an independent insurance adjuster) so all this just got put on hold, I had plans to shoot on Monday. So much for plans..........Thanks for your reply and if you see something I need to change let me know, always willing to learn

 

[JohnKielly]

Doesn't it all relate to SAAMI specs, where loaded round dimensions relate to a "standard" chamber & allow firearm manufacturers to commit to chambering an action of certain dimensions for a particular calibre. Variations bullet to bullet then relate to where the ogive needs to be relative to a standard throat.

Thereforeyou may need to comply with that spec if you're magazine feeding in one action but might be able to load longer in another. An example that comes to mind is the old Sako L461 action where the OAL for a .222 R was generous, but a .222 magnum wouldn't magazine feed unless it complied with SAAMI spec.

 

[Ned Ludd]

Figure out your absolute maximum COAL that will feed reliably in the mag. Seat bullets at ~.015" to .020" shorter than that. Establish your optimal charge weight at that seating depth. Now you will still have about .015" to .020" in either direction for you to adjust and optimize seating depth. The final load will not have the bullet seated within approximately .015" to .030" of the lands like it might if you were developing a load where mag length wasn't a constraint, and you knew the exact COAL at touching the lands. But it can be optimized nonetheless. Some factory rifles have extremely long freebores, but optimized load can still be developed with the bullets jumping a long way. I have always viewed seating depth optimization as cyclic. It's all about timing. In other words, if you keep moving it off the lands, it should continue to tune in and tune out as the distance from the lands increases. We normally don't do this because you reach a point very quickly where you start to cut into usable case volume with the bullet base. We therefore more typically end up with bullets seated within about .015" to .030" or so of the lands when we have the choice, i.e. as in when loading for well-defined chambers and not having to restrict COAL due to mag length considerations.

I'd guess you could even start at .050" less than reliable mag feeding length if you wanted, but you'll eventually start giving up usable case volume at some point, at which reduced velocity will become an issue. The key is to determine minimum reliable mag feeding length with possibly a tiny amount of extra clearance room, then establish some reference point shorter than that to use as your starting point for load development. By doing that, you will still have some seating depth adjustment available when you have optimized the charge weight.

 

[gotcha]

No sir I have not, that is the reason I'm starting .030 off the lands with 42, 42.5, 43, 43.5, 44, 44.5 and 45, after I get that node I'll work it even closer by .002 and then I'll start working from the lands, whew! I hope I got all that right! Just got a call and I am being deployed to VA for hail damage (I'm an independent insurance adjuster) so all this just got put on hold, I had plans to shoot on Monday. So much for plans..........Thanks for your reply and if you see something I need to change let me know, always willing to learn

Sounds like you've got a handle on the situation. Wouldn't it be nice if your optimized load also fed in your magazine