How does bullet manufacturer determined C.O.L. for a bullet

[338winmag]

I understand manuals are just suggested options and reload starts but 2 questions:

1. How does the bullet maker determine the C.O.L. for their bullet? "Middle of the road" bearing surface when seated or ?

A reloaders manual states the C.O.L. for each bullet and then suggests powder charges for each while often stating "most accurate load with specific powder and charge".

2. Are all these loads including most accurate loads tested at only the C.O.L. listed?

If #2 is "yes, only tested at C.O.L. listed", I would think that for accuracy, this could leave a lot open to any of the powders listed, if not for just modifying the C.O.L\charge.

The more I reload for different rifles using different powders and different bullets with their respective manuals, maybe I should understand these suggested powder charges should be taken with a "grain of salt", or should I say "grain of powder"? :lol:

338winmag

 

[1Shot]

The COAL that is given in a loading manual is usually the SAAMI standard length that should work through any rifle of that caliber. The suggested "accuracy" load would be with the powder listed and components listed and COAL listed in the particular weapon that was used to do the load work up. Yes after over 30 years of hand loading I have learned that a reloading manual is a GUIDE. Nothing is set in stone. That is the reason that they give staring and max loads. Every weapon of even the same caliber is a different critter. Always start low and work your way up with a load. Bullet seating depth does effect accuracy greatly and it will also effect pressure the closer you get to the lands with the bullet. It has been my practice to start with the bullet 10 thousands off the lands or the max COAL that will work through the magazine and work up my most accurate load with my powder of choice. Then I will start moving the bullet away from the lands 10 thousands at a time in a ladder test to see if I can find a more accurate node. If I find a more accurate COAL node I will move 5 thousands each way, shorter and longer, to see if that improves things. Theoretically you could find a very accurate load with any powder in the burn rate that would work in the caliber of your choice by changing amounts, bullet style, primer make, case make, seating depth. But to do so you would probably shoot the barrel out doing it. Ain't reloading fun???? :mrgreen:

 

[338winmag]

That answered it.
Thanks 1Shot..

 

[R Flowers]

I agree completely that the information in reloading manuals are a guide and should be considered as such. But, sometimes they point you in the right direction.

A friend brought over a Browning A-Bolt in 270 Winchester that he needed a non-lead bullet load for. (Being in California and all)

I looked in the Barnes manual and using the 130 grain TSX they suggested that H 4350 was the most accurate powder they tested. I started near the minimum load and worked up to the maximum. I seated the bullets to the suggested OAL shown in the Barnes manual. (Never mind this gave a jump to the lands that was over 0.100 inches.)

I went to the range and shot a group with the Factory Remington 130 grain Core-Lokts he had been shooting, they gave an even two inch group and a whopping 2950 fps.

Then I started with Barnes reloads, going up a grain of powder at a time. I shot no groups over an inch and by the time I got to the max I was getting an even half inch group and 3075 fps. I think my load development is done and I also think using the suggest powder and OAL from the Barnes manual just may have helped.

 

[widgeon]

Reminds me of my first load development for my .270win. I was using 130 grn BT and determined where it hit the lands. Backed it off about .005 and proceeded to load about 10 rounds, to check pressure. All was good until I tried to get one in the magazine :shock: . OOOPs. Back to the drawing board.

Back at the bench, I seated ( on an empty, test case) the bullet deeper and deeper until it fit and operated in the magazine. I don't have my notes handy as to what the OAL ended up being, but I went with it and wound up using a medium charge of H4831 and getting somewhere between 1/2"- 3/4" groups at 100 yards. :mrgreen: I'm sure this load in this gun is far more accurate than I and although I could probably develop a faster load, I'll take the confidence of accuracy any day.

I'm hoping to be in a place where I can set up my bench again soon and work up some of the 140 AB's for this gun.