Help with COAL

[state of shock]

I am new to reloading.
11/111 trophy hunter in .308
Only done a few batches and shot them to determine best powder amount with given bullet. I am confident that this load is safe and not approaching unsafe chamber pressures. Now that I have found what I believe to be my best load, I want to start experimenting with coal for better accuracy.


To this point, I have been seating the bullets at the recommended coal (2.735) for the bullet I am using from the Hornady book. I have also determined the maximum coal (to the lands) on my rifle. (I used the Hornady COAL gage and I have a comparator with the proper .308 fitting for measuring from the o-give).



Here is where the confusion sets in. I have read posts that say to start anywhere from right on the lands to.020 off the lands and back off in small increments looking for best grouping. This sounds dangerous to me as from what I have learned thus far, at or near maximum coal for my gun would produce the highest pressure.

Keep in mind the difference from the recommended coal from the hornady book (2.735), where I have been doing load development, to the maximum coal for my gun is over a .115 increase. This seems like quite a bit of distance.

I have also read an equal number of posts that say to start way back at my Hornady recommended coal (2.735) and work my way forward in .010 incriments watching carefully for excessive pressure signs until I find the best grouping. This seems to me the safer way to go.

Any thoughts or suggestions would be greatly appreciated.

[keith1]

Rick,
If you move the bullet forward [longer COAL] you will tend to lower the chamber pressure. Just don't go to long and jam the bullet into the lands.
Regards, Keith

[Steelhead]

Ease up in .040 or so increments and watch for pressure.
I usually start .010-.030 from the lands and stay there till I figure out the powder charge, then I increase jump to see what happens.
Mostly I end up about where I started.

[bootsmcguire]

I tend to use Steelheads philosophy except I start on the lands and start seating deeper if needed. I have found most of my barrels like the bullet just on the lands or within .030" of the lands. This works well for me because most barrels have accuracy nodes higher in the charge range and lower on the charge range and are not often at a maximum charge, so as long as I am not at or really close to max charge the slight increase in pressure that comes from seating deeper is not enough to be and issue for me.

[foxx]

Also, keep in mind the Max COAL listed in manuals is not intended to be of a safety concern. Those measurements only indicate the max length to function properly thru a magazine.

[DanSavage]

I've ran coal tests over the chrony in 3 .308's and a .223, unless your running a load right now that is on the jagged edge of being max pressure for your gun, I wouldn't be afraid to move bullet out to with in .005 of the lands. Pressure slightly decreases all the way out until you just touch the lands, then pressure will rise when your jamming, but in my experience not a whole lot of extra pressure.

[state of shock]

Thanks everyone for the replies. Good info. I have a couple more questions:

1. Just to make sure I'm understanding things correctly. Increasing coal does or does not increase chamber pressure? Or, considering I am currently over .115 off the lands now, I will not see a significant increase in pressure unitl I get to about .015 - .005 from the lands?

2. Considering I have to increase coal approx .100 just to get close to the lands, at what point will the bullet be seated too far out of the neck? I'm using Hornady 150 gr. interlock sp.

[cranebird]

You could measure the length of your trimmed case and then the length of the bullet and add them together and then subtract that from the Oal of your reloaded cartridge to tell how deep the bullet is seated but I gather you already knew all of that. To determine at what point the bullet is seated out too far is basically a judgment decision by the person doing the reloading. Nothing is written in stone when reloading and there are too many variables to know for certain.

[state of shock]

Crainbird- thanks. Yeah, makes sense about all the variables. I thought I read somewhere about a way to determine minimum seating depth using the diam of the bullet vs. the length of the neck.

I found a really good article about coal on the berger bullets web sight that really made all this alot more clear. It appears I had it backwards about how coal effects pressures. One important fact I learned was that increasing coal apparently can reduce velocity in a specific powder charge. Based on that, I guess I should first establish an optimum coal and then work on powder charges. Which may then again change the optimum coal. A vicious circle!!! But thats the best thing about reloading. Tinker, tweek, test; repeat as necessary.

Thanks again for your input.

[Texas Solo]

Which may then again change the optimum coal. A vicious circle!!! But thats the best thing about reloading. Tinker, tweek, test; repeat as necessary.

Now you're getting it! LOL. I always start my load development at .005 off the lands. No pressure issues as it's not jammed, and pressure is reduced due to more area left in the case.
I start my charges at the "middle of the road" data from the powder manufacturer, then go 1/2 grain increments either way. That finds a node rather quickly. Use that load to play with seating depth next. Pick the best one and refine the powder charge in .2gr increments. It's a process of elimination really, but this method has always given me a great load in the least amount of time and components.

[state of shock]

Thanks Texas Solo - Good info and very clearly explained. Re-affirms what I thought I understood.