DIY COAL tool

[savage M110 BAS]

I have been looking for a good COAL tool for my .308 for quite some time now and it finally dawned on me that I could make for the cost of a piece of .308 brass. I took a full length resized piece of .308 brass and made 3 cuts from the neck to the shoulder. This allowed me to insert a bullet and still retain enough tension where the bullet would not move unless I wanted it too.

I inserted a Hornady 168grain A-MAX bullet and did a quick measure of the overall length of the cartridge.

I inserted the round into the chamber of my rifle and closed the bolt slowly. This caused the bullet to touch the lands of the rifling and get pushed back into the cartridge. After opening my bolt I pulled out the round that measured 2.81’’, which is the Max COAL of that bullet in my particular .308.

I plan to take my favourite loads and test them .005 .010 .015 and .020 off the lands and see if my grouping gets smaller.

I can think of any reason why this method wouldn’t be as accurate as the Hornady OAL gauge you can buy for over $40. if you can think of a reason please let me know.



Cheers guys.

 

[Baribal]

..... I can think of any reason why this method wouldn’t be as accurate as the Hornady OAL gauge you can buy for over $40. if you can think of a reason please let me know.......

Simply because you're only measuring the tip of the bullet, not the point were the ogive meets the rifling.
The tip dimension changes quite a bit from one bullet to the other, even when using match grade bullets.

 

[Porschemann]

That method should work for THAT particular projectile. If you use a different projectile, you should have to repeat this since the rifling will contact the projectile somewhere further down than where you are measuring; and that will vary from projectile brand and style. It will still give a starting point for YOUR rifle.

 

[Dunk]

The thing I would be concerned about is the bullet sticking in the rifling and being pulled out of the case. I was planning to use the slotted case and put locktite on the inside of the case then camber the round,wait til the locktite sets up then back the round out and measure.Something I saw on here.

 

[savage M110 BAS]

That method should work for THAT particular projectile.

Yes I do realize that this method would have to be repeated with every different style bullet used.

 

[savage M110 BAS]

The thing I would be concerned about is the bullet sticking in the rifling and being pulled out of the case. I was planning to use the slotted case and put locktite on the inside of the case then camber the round,wait til the locktite sets up then back the round out and measure.Something I saw on here.

So far I have not had any stuck bullets in the lands. As long as you slowly close your bolt it shouldn’t be a problem. If it does get stuck a cleaning rod and a gentle tap is all it takes to remove it.

 

[Dunk]

I was going to do this with the locktite to find out where the bullet body touched the lands so I could adjust the distance off the lands. The locktite insures the bullet stays at its max position.

 

[358Rooster]

I was going to do this with the locktite to find out where the bullet body touched the lands so I could adjust the distance off the lands. The locktite insures the bullet stays at its max position.

It may also ensure the case stays in the chamber too, if you're not careful!

 

[Magnum_Tom]

OP: Great pictorial review of this phase of the process.

I'll just add a few things that haven't already been mentioned:

1) Get a bullet comparator. Hornady has one and others may as well.

2) 3 cuts on the case may not give you much neck tension. You might want to try 1 or 2 cuts instead. The bullet will be less likely to fall out in the chamber and less likely to seat deeper when measuring.

3) Run through your process, measure and repeat a number of times to ensure you have the right measurement. 10 times is a good number.

4) Once you have your measurement, make dummy rounds for the various distances from the lands that you want. The bullet comparator comes into play here. Crimp those dummy rounds and label them. You can now set your seating die with the dummy rounds.

 

[TedNugent]

I have seen this done with just neck sized brass, using a lit match to blacken the bullet. Insert bullet same way, lands leave
a mark on the bullet so that you can confirm it was touching the lands. Can be done with each bullet type as well.

 

[HIGHRPM]

I use that method for all my rifles and it hasn't let me down once. As long as you repeat the process as mentioned to really confirm what your seeing. It may not be the best way, but for the everyday shooter, it works !

 

[aridan]

+1, I also use a 'slitted' 9mm case as an OAL gauge for pistol reloading, works fine since pistol rounds are spaced on the casemouth. I threaded a small screw into the primer pocket to make fine adjustments.

 

[Kayser Sose]

I think that's a good idea.

 

[horseman2]

Using a case fired in that chamber neck sized or a full length sized case, run the neck in and out over the expander two or three times.
That will lessen the tension and do the same thing to determine the OAL. A split case works as well.
Then the case and seated bullet is kept in the box of bullets it came from for future reference.

 

[UR2X3M4ME]

What I do as well. 10 test cases to which I fit bullets wanted for that batch et voilà: Chamber length for that bullet.
When establishing COAL, I factor in the jump desired and a tolerance for bullet variation.
Thanks for posting, very explicit.

 

[house of beers]

I dont think I would want locktight or any glue in my chamber.Your idea with the three cuts is fine, but check for bullit runout first to get a more precise reading.

 

[mulemania]

I used to do it your way, but found it hard to keep the bullet completely centred and enough neck tension, now for 30 cal I run a 5/16 drill bit in reverse and stretch the case neck while taking off a slight bit of material, once the bit is in one or two turns takes down enough material in the forward setting, I spend about 5 min feathering it until my bullets are in place but can be moved with little effort, I found that this gives me the most consistent results. I also found a brass brush on a drill will smooth any gulling or areas that may catch the brass

 

[nevanevan]

I did a similar method using a lee collet size die on a once fired peice of brass. I set the correct tension for the bullet to be just snug in the case, inserted carefully and pulled it out. Once out, I superglued the base of the bullet to the case so that it is one unit. I use it as a reference to set my die down to by just scewing the die down untill it touches the bullet tightly. After doing that I can measure the total overall length of any seating depth and change the distance off the lands quite easily, and this way there is no locktight in the chamber.

Evan