Home Forums Hunting & Shooting Ask The Gunwriters How do you determine COL?

I do the same, takes all the guesswork out.

I have never ever done it. No need to do it.
The shape of the group tells you where your bullet needs to be seated.
Large equilateral triangle = seat out further.
2 in and 1 out of the group = seat deeper.

I move the seating die a quarter turn at a time.

John

So your advice to a reloader that doesn't know how to determine max COAL is "screw that, you don't need to determine max COAL, just start adjusting your seating depth based on shot patterning?"

Wow!

I hope he has enough sense to ignore this stupidity.

David

Why would 2 in 1 out mean seat deeper, what's going on to cause that? If the load is inaccurate, how'it igoing to work on 2 out of 3?

I tried everything mentioned or variations and like the consistency of the StoneyPoint tool. Plus I get to buy more chitt that way.

It works. I read AussieGunWriter's advice on this some time ago and it works just fine.

I do start by finding the max OAL to touch the lands and then check that against maximum magazine restrictions. I like to start at .020" off the lands just because I like to leave some clearance. That's not a magic number, folks can start at whatever distance they care to based on their own needs and opinions.

But if you get groups of 2 and 1, or 3 and 2 if you start with 5 shot groups, seat deeper. I generally go about .020" or .030" at a time, depends on my mood that day. The groups will shrink and that lonely bullet hole will move closer to the other two. If you get a nice round group but it's bigger than you think it should be, seat shallower (closer to the lands).

I have seen this work time and time again in the last couple of years since I started trying it. Some rifles shoot best at .050" off the lands, one likes .001" - basically touching.

Now if you get scattered groups or unexplained flyers in 4 and 5 shot groups the trouble could be elsewhere - bedding, barrel needs free floating or whatever, but given that everything else is okay the group pattern gives a clear indication of which way to move the bullet.

Steely got the order correct. Check magazine bridge opening first. I didn't do that with my first Montana 84L and realized the evening before its first hunt that the overall was too long to eject an unfired round. It fit the mag and chamber, bu caught on the bridge at ejection. Not a good thing to find in the field.

I use a black marker instead of a match. covers better and shows the rifling marks just as well. I then measure that with the Stoney Point ogive tool. That is the measurement I prefer, as it appears to be much more consistent than measuring overall length at the bullet tip. I record that measurement for every load and bullet for future reference. Then, depending on the bullet, I back off 0.020"-0.050" for most bullets. Barnes certainly appear to like the deeper seating, usually -.050"-0.080" But those measurements are guidelines and will be rifle specific.

Enjoy!

Excellent post Jim. That's been my experience as well. Sans Ausiegunwriters advice: Haven't read it. Smoke the bullet and use a piece of once fired brass from that rifle. If the brass has already been resized then you'll need to split the case neck. Sounds like the OP is already doing it this way. With a smoked bullet and modified case, there is really no "guess work" involved. Pretty simple and no extra expense with unnecessary equipment like a stoney point or special hornady modified case etc. etc.. Use the money you saved to buy more bullets

It's not his adjustment advice based on grouping I think is stupid, it's the advice to skip determining MAX COAL prior to adjusting seating depth. Plenty of factory rifles that come down the pike with abnormally short throats - I've owned two of 'em. Following his advice is an invitation to a potentially dangerous over load situation.

David

+4

Shod

Not a doubter of the process, just wondering what is going on that would make 2 in 1 out happen. Anyone got an idea?

People love buying more tools, [bleep] that.

The least amount of stuff, the better off I am. Squeeze in a fired neck enough to hold a bullet firmly. Seat bullet long and measure. Insert and close bolt, remove and remeasure (bullet gets pushed into case).

Repeat a few times and you know where you are. If it fits the magazine, you're golden, if it don't, seat deeper till it do.

I don't need cleaning rods, wooden dowels, Hornady comparators, Stoney whateverthephuck. Hell, I don't even need a sharpie.

A fired case, a bullet and a micrometer.

I do like the slip case that I made using a dremmel, by cutting a slit in the neck and a wee bit into the shoulder. Easier for me to pull it back out for multiple measurements than just a squeezed neck. I make one for each cartridge that I have. miles

Plunger type ejector screw with it that way?

I like tools. I even bought the drill and tap to make my own modified cases for my HornadyStoneyPoint tool! I can find the lands without a fired case. Then use a comparator to messure and know with any other bullet without repeating. Simple enough.


Still hoping someone can 'xplain me why the 2 in 1 out happens...

Unless close is good enough,comparators are a pretty useful tool given the nature of bullet tips and even ogive variables lot to lot.

oregontripper,

"2 in 1 out" happens because 3-shot groups aren't sufficient to really reflect the accuracy of a rifle and load. The spread of ALL shots will be larger than the average of 3-shot groups, so the "flier" is simply a shot that's part of the overall picture.

Four-shot groups are superior for testing accuracy, and more shots are even better.

rosco,

Using a bullet in a fired case is "close enough" for determining proper seating depth that a bunch of winning benchrest shooters use it. In my own benchrest rifle it resulted in 5-shot groups averaging around .18" with a minimum of fuss. Which is part of why I use exactly the same "tool-free" method as Steelhead.

I learned this from Benchrest shooters decades ago, and as a writer who specialized in reviewing rifles and developing loads for the reviews, I proved hundreds of times it worked and this advice is being repeated and proved over and again by readers here and other sites where the advice has spilled over.

If you want to know a maximum dimension for OAL, consult you reloading manual.
If you want to know whether that dimension is relevant to your particular rifle, try it in your magazine box to see if it will really fit as a starting point but also confirm there is enough leade to chamber that dimension before running off to the range. Some rifles will house an OAL but not chamber it, Ruger, being an example.

So, how you you "know" I am wrong?

John

JB is perfectly correct here. I buy those 5 target sheets and add spotter bull's in between the printed targets so I have a lot more aiming points on a sheet.

I then record the sequence of targets being used and the loads so I have a series of group shapes to average out. Instead of having single groups with 5 or 10 holes, my method allows me to review each bank of 3 shots compared to the last and the next (I usually shoot 5 targets)so I have not only a range of targets to review, I can clearly see if there are sequences occurring like number 3 being thg flyer "consistently" or whatever, as the targets are cleaner and less destroyed.

The other comparison that can be made is how and when the barrel heat enters the group sequence. Barrel contours differ on each rifle so they need to be reviewed separately, so you have can learn how far you can push a barrel until you are creating erratic information cause by excessive barrel heat.

There is a lot to it but you can't learn a damn thing by starting out thinking you know all the answers. You never do, but after a time, you can start averaging out your results across the board, to see the synergies that occur from the practices you adopt.

I learn from everyone here, and that includes how to conduct myself on a public forum. After owning a bar for a few years, I know exactly how far I can go in the other direction and decency, with explained opinion, is far more constructive.

John

John,

Well said. I can only add that often barrel heat doesn't affect the barrel itself as much as the heat waves coming off the barrel affect aiming through a scope.

A properly stress-relieved and bedded barrel should shoot to the same place even when screaming hot. In fact, this is one of the characteristics common to NULA rifles. A gun-writer friend who had never shot one before finally tried a .30-06. He became so intrigued with how the bullet holes kept landing in the same place he eventually shot three dozen rounds without letting the barrel cool, ending up with a group of an inch.