Hornady Reloading Guide - how are C.O.L. values to be used?

B

BearClan

CGN Regular
Rating - 100%
4   0   0
Location
Iqaluit, Nunavut
Hello,
I recently got my 300WSM rebarrelled. Yesterday, I was excited to test Hornady Outfitter 180 CX factory ammo with this newish barrel, only to be disappointed to learn that I cannot close the bolt. It seems my throat was cut too short to use this ammo, as is. No problem, I thought - I could simply seat the bullet deeper.

However, in looking at my Hornady 11 guide, I noticed that each bullet listed has its own C.O.L. Value. For the 180 CX bullet, this value is 2.235”. The maximum C.O.L. That my rifle can accommodate us 2.219”. Given that the Hornady guide also provides a “maximum C.O.L. Value (I.e., 2.860” for the 300 WSM”), I bullet- specific C.O.L. Value can either be the minimum value or perhaps a nominal value.

Can anyone tell me the purpose of this 2nd, bullet-specific value? Alternatively, and more importantly, would I be risking my health if I seat the CX bullets deeper (a shorter COL than the 2.235” value listed for the 180 CX value in the Hornady guide). I was thinking of seating to a COL of 2.189”, which would place this bullet 0.030” off the lands I my rifle and 0.046” shorter than the 2.235” COL from the Hornady manual.

Looking at the factory ammo as is, it seems like their is plenty enough shank left to allow deeper bullet seating.
 
The problem with seating bullet deeper, is that it will increase pressure and that is ok in stuff you load your self since you would start at 10% of max load, but doing this with factory ammo there is no way to know if that extra pressure will be problematic….
I might be out to lunch here but others will confirm this or they will tell me I’m wrong!
 
I am sure it has been suggested on other CGN posts that the COAL given in most books is likely correct for their rifle and those bullets, but does not mean much for your specific rifle, or the level of wear / lands erosion that it has or does not have. I recently received the Woodleigh Manual - as per stuff seen in other manuals - it describes how to establish when the bullet of your interest is "hard" on your lands. Then measure where is your closed bolt face - difference is the COAL with that bullet HARD on the lands - Woodleigh suggest to back off 0.020" to 0.040" from that to do your pressure test series - work up to whatever is "maximum" in your rifle, with your components - then can adjust that "jump" plus or minus to maybe improve accuracy, or maybe you see no difference. I read that solid copper bullets often want more jump than that - like circa 0.075", and I know that some bench rest guys want their bullet hard into their lands - is sort of up to you to find out what you and your outfit can show on targets. If you use factory ammo, you rely that the ammo maker and the firearm maker were in synch enough that the two products work together. If you decide to "hand load", then what a ammo factory does or does not do kind of gets irrelevant to you - for starters, most makers these days use pressure test machines to work up their loads - I do not know any home hand-loader who has that machine.

I have done many loadings for rifles that end up with the cannelure on the bullet way ahead of the case mouth rim, or down inside the case neck - and with a 0.030" bullet jump in my rifle. COAL will vary from bullet to bullet - even within the same box of bullets - but, for sure, among different brands, likely among different weights, etc. As I hoped I passed on to to a local young fellow who wanted to learn to reload - knowing where YOUR lands are, in YOUR rifle, should be a fairly basic step in working up loads for YOUR unit.

Or, just use the numbers given in the book and be happy with the results that you get from that - if you are not happy, perhaps take that up with them?
 
Last edited:
I was thinking the same thing (seating deeper = potential increase in pressure). I'm also considering disassembling the factory ammo, discarding the powder and replacing with the H100V I have on hand, and doing a round of load testing. However, my concern is what the 2.835" COL given in the Hornady 11 guide for the 180 CX means. If this is a minimum recommended COL for this bullet, and seating deeper/shorter than this COL may lead me to potential danger, I will simply disassemble and resell the 180 CXs to a fellow handloader. The cases are pretty much what I'm after, anyways.
 
BearClan said:
I was thinking the same thing (seating deeper = potential increase in pressure). I'm also considering disassembling the factory ammo, discarding the powder and replacing with the H100V I have on hand, and doing a round of load testing. However, my concern is what the 2.835" COL given in the Hornady 11 guide for the 180 CX means. If this is a minimum recommended COL for this bullet, and seating deeper/shorter than this COL may lead me to potential danger, I will simply disassemble and resell the 180 CXs to a fellow handloader. The cases are pretty much what I'm after, anyways.
Click to expand...

What I wold do; I would pull one bullet, weigh the poudre charge. Then I would pull all the bullets and save all that powder! The I would take the number of that weighted charge and reduce it by 8-10% then start reloading with the right coal for your rifle(COAL can be two things, the max length that your magazine with accept or the maximum length you need to be where you want the bullet to be in relation to the land of your barrel, usually the magazine dictates the COAL)! So let’s say there is 46gn of powder in the charge you pulled out, I would start with 42gn then go up to 46gn by one grain increments! So you will end up with 5 rounds of five different charges with the bullet seated where you want it and then you go to the range and start shooting the first round, 42gn, look for pressure signs, then the 43gn, look for pressure signs… you keep at it until you reach your 46gn load or you witness any pressure signes! If you have pressure signes at 44gn, that is where you stop and don’t shoot the last two rounds!
That way you will be able to use the components/powder that was loaded it those ammo and learn a few things!
 
You might want to weigh more than one cartridge if you’re going to use the factory powder. Just pulled almost 2 boxes of factory 6.5CM because of lousy accuracy and there was a .6gr variation from low to high in 10 rounds. Would give you a better starting point.
 
Well - 2.860 is likely the maximum SAMMI value for the cartridge, and is used as a basis for manufacture of the magazine and feed system. The CX number is the number used for testing is based on universal fit in rifle chambers. Since your chamber is cut short (why?), you have an interference problem.
Yes, reducing COAL will lead to an increase in chamber pressure slightly, but I would think that Hornady likely has some "margin" in their pressure numbers. I would shorten one round to the desired length, fire it, and check for the usual pressure signs. Alternatively, pull the bullets and reduce the powder charge by, say, 3 grains and away you go. It you want to get fancy, you can develop a "tuned" load by testing loads a various powder increments - Which is what i would do.
 
You must log in or register to reply here.
Back
Top Bottom