Determining Precision COALs

[Brasshole]

I have been reloading for many years but always stuck to max COAL in my reloading books. Now that I am retired from the Marine Corps, I have more time to hunt which is driving me to precision loads for long range hunting. I am shooting a Tikka T3x in .300 WM. What is an easy way to determine the optimum overall length and bullet seat depth to reduce jump and run your tip to the lans? Hope the question makes sense. Thanks.

 

[thatguyshm]

Before you go to far down the rabbit hole and spend money you may not need too, why don't you check your magazine and see how much room you have. A hunting buddy has a Tikka 300 WM and the magazine doesn't let you get very close at all to the lands.

 

[FEENIX]

Before you go to far down the rabbit hole and spend money you may not need too, why don't you check your magazine and see how much room you have. A hunting buddy has a Tikka 300 WM and the magazine doesn't let you get very close at all to the lands.

Agreed! Find the best compromise on COAL/CBTO for the bullet you are trying to load on your specific set-up, not on others.

 

[Brasshole]

Yep....already hit that roadblock. Wish I knew when I bought the gun. Regardless, I ordered new bottom metal from RedSnake which allows me to use AICS mags that will take a 3.757" COAL. Factory Tikka mags will only take a 3.34".

 

[Brasshole]

Hey folks, per my first question, anyone have some tricks for determining the optimum length of your precision loads to get your rounds up against the lands?

 

[Quintus]

You can make a dummy round seated long. Use a sharpie to color the ogive and chamber it. keep seating a little deeper until you can close the bolt with marks from the lands just starting to take the marker off and you will have your length. I got that from the load manual I got with my RCBS kit in 1991 and it has worked ever since. There may be easier ways. Welcome to the site and thanks for your career of service. Semper Fi.

 

[FEENIX]

Hey folks, per my first question, anyone have some tricks for determining the optimum length of your precision loads to get your rounds up against the lands?

How do you currently do yours per your original post?

 

[thatguyshm]

Have you heard of the Hornady modified case gauge? That's what I've used for years. Mono's and bonded usually about 0.050", and I'll do the berger method on cup and core.

I've never done the Alex Wheeler method but I know a lot of people swear by it. Just Google it.

 

[Brasshole]

You can make a dummy round seated long. Use a sharpie to color the ogive and chamber it. keep seating a little deeper until you can close the bolt with marks from the lands just starting to take the marker off and you will have your length. I got that from the load manual I got with my RCBS kit in 1991 and it has worked ever since. There may be easier ways. Welcome to the site and thanks for your career of service. Semper Fi.

Thank you Sir.

 

[Brasshole]

How do you currently do yours per your original post?

I grew up reloading under my grandfather who was born in 1918 and reloaded to book specs. He never played with precision loads to get bullets to ITL. If the Lyman book said to seat bullet to overall case length of 3.34", then thats what he did.

 

[FEENIX]

I grew up reloading under my grandfather who was born in 1918 and reloaded to book specs. He never played with precision loads to get bullets to ITL. If the Lyman book said to seat bullet to overall case length of 3.34", then that's what he did.

OK, now we have a better understanding of your experience. There are plenty of tools out there that can help you with this process. The Hornady-N-Load OAL and headspace gauges are what I use. Go to YouTube to see how it is done. There are plenty of information there.

 

[Brasshole]

OK, now we have a better understanding of your experience. There are plenty of tools out there that can help you with this process. The Hornady-N-Load OAL and headspace gauges are what I use. Go to YouTube to see how it is done. There are plenty of information there.

Thanks Feenix. Very helpful. It appears finding .300 WM cases for the tool are difficult but I will keep looking.

 

[FEENIX]

Thanks Feenix. Very helpful. It appears finding .300 WM cases for the tool are difficult but I will keep looking.

It is best to use a fired brass off your rifle. You can send 3 of them to Hornady to have it drilled and tapped or you can buy the drill and tap set from Amazon (IIRC, it's $20) and do it yourself.

 

[cdherman]

It is best to use a fired brass off your rifle. You can send 3 of them to Hornady to have it drilled and tapped or you can buy the drill and tap set from Amazon (IIRC, it's $20) and do it yourself.

This can be very important, or not so much. Why? Because the dummy rounds that you get from Hornady (or other sources that make them too) are usually unfired brass. When you fire brass in your gun, you get some stretch. In a belted magnum, after firing, you can (many say should) start resizing the brass only by dropping the shoulder back 1-2 thou. This then results in your brass headspacing off the shoulder, just like a non-belted case. Better accuracy. But if you do that, you may find that your brass and dummy brass are not the same length. And the Hornady tool measures "Cartridge base to ogive" or CBTO. If you measure to the lands with a "short" case, you will think they are closer than they are.

All of this matters mostly if you are really trying to get close to the rifling. It also means that practically, most reloaders try to stay away from real close to the rifling. For instance, if you are trying for 10 thou off the rifling, and you mess up by .003" you have a 30% variance. If you aim for 30 thou off the rifling (a common number used) then that same .003" error is only a 10% variance. Less likely to mess your groups up.

If your fired cases and the dummy are the same length to the shoulder (as measured by another tool from Hornady, the Headspace tool), you are a little better off. But another Caveat: The Hornady Headspace measurement tool measures only at one standardized point on the shoulder. If your chamber is cut a little different, you could be mislead in assuming that the dummy case and your fired cases are identical.

All this being said, I have never invested in the drill and tap set to make my own dummy cases. I don't have a lathe or milling machine, and while it sounds easy in theory (just drill out the primer pocket and thread the hole) it strikes me that you would have an innacurate tool if the threaded hole was not perfectly in line with the axis of the bore. But if you are handy or have the right tools, it is indeed very easy to make a dummy case....