Home Forums Hunting & Shooting Ask The Gunwriters Finding the optimal COAL

I've read several references on this. The recommended interval to load cartridge lengths, range from as small as 10 thousandths to as large as 30 or 40 thousandths Has a consensus been reached as to the proper interval so as to not was ammo on one hand and miss the node on the other?

Huh?

I think what he's asking, is when one is developing a new load and one wishes to experiment with various cartridge overall lengths (seating depth, "jump", however you want to identify the amount the bullet moves from the case before engaging the rifling) to determine what works best in one's own rifle with a particular load, what are the increments in cartridge overall length recommended? His concern seems to be that, loading and testing in too small increments will be a waste of components, and if one uses too great increments, one may pass over the so-called "sweet spot" where the best accuracy is to be obtained.

cra: correct, thanks for helping to clarify. I have read recommendations that one should test loads at .010; .040; .080. etc off the lands. Other recommendations are that one should test .010; .020; .030, etc. Following the second recommendation would require the edxpendature of more primers, powder and bullets.

So my question was: Has a consensus been reached on how small an increment of COAL is sufficient to find the sweet spot.

Hopefully, that is clear enough. thanks

My brain has reached consensus with my tools wrt to cup-n-core and bonded bullets. I've not yet handloaded mono bullets; they may behave differently, but I dunno.

I'll seat bunches of 3 to 5 rounds at .020, .040, & .060. and then sling 'em down range. Invariably, the most consistently tight groups land somewheres between .020 and .040, but occasionally not. But in any case, the groups will indicate what the barrel is liking and I'll tweak from there.

This strategy is supposed to be for VLD Bergers but the idea makes sense for other types of bullets too.

https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

I do this.

I have, traditionally, agonized over optimum seating depth. Recently however, I broke away from it. I dug out my .220 Swift (Ruger 77V w/16X Leupold) which rifle I haven’t done anything with in probably 30 years. I got a box of 55 grain SGK’s and loaded some up with some 4064 I had around. I made no effort to tune seating depth or anything. Data from Loaddata.com indicated 38 grains max with that bullet. It also provided an overall length. I loaded up 5 rounds each with 36, 37, and 38 grains at that length and headed to the range, all the while suppressing my concerns about optimal length, etc. I started shooting the 36 grain loads, ended up shooting all three loads with groups going from just under an inch for the 36 grain loads to just under 1/2” for the 38 grain loads.

I’m not saying that’s the best way to do it. I recognize that it’s a small sample size. I don’t suggest anyone else do it that way. Just saying I did it and ended up loading a bunch of ammo that shoots pretty well in a rifle I don’t know what to do with these days.

Depends on the type of bullets. If I had to generalize; seat cup-n-core bullets .020 off the lands. Seems to me the all copper options benefit more from adjusting seating depth and like more jump. Anymore I just seat the TTSX's so the top band is just above the case neck. Works for me anyway.

Methinks it depends a lot on what style of bullet is being used. Experience tells me that closer is usually better than the other. I like .005" increments for jacketed or monolithic bullets. Kissing the lands or engaged firmly for lead if the action will accommodate it. Sometimes, as some have opined, a nice kiss with J-bullets is the schizzle.

I'm inclined to find the best performing load with about .015" relief when using J-bullets, then start tinkering with COAL.

My experience is that far more rifle bullets than most handloaders suspect will shoot more accurately when seated deeper--including lead-cores.

As any example, in my 6.5 PRC the 129-grain Nosler AccuBond Long Range shoots a LOT better when seated a full .1 inch (that's 1/10th of an inch) from the lands, The 127 Barnes LRX does as well, but that's expected with monolithic bullets.

The safest way to test deeper seating, however, is to start at the typical .02 or so with lead-cores, and if the load doesn't shoot the way you want then start backing off, which reduces the pressure. I generally first try around .05, and if that doesn't make any difference, then .10. Which is a lot less expensive than smaller variations. With monolithics I start at around .05.

But in these days of "shortages," it also helps to be realistic about the level of accuracy actually required to kill deer at 250-300 yards.

Thats a good rule of thumb and has worked very well for me as well. Can't get any more simple than that. Also, I'd add that I let the group dispersion tell me if I need to seat deeper or closer to the lands. Its easy to read when you fire more than 3 shots on target (5-10 works best). As a rule, if you are "double grouping", you need to seat deeper (back off the lands more). Most times you can just seat at .020" off the lands and find your optimal charge weight and excellent accuracy, without even messing with seating depth. Some guys like pharmseller start off with a heavy (almost book max, or book max) load and then adjust seating depth until he finds an accuracy node. Both changing charge weights and adjusting OAL will change the node in which the load resides. Working up a load, by adjusting charge weight is the safer route to take.

I load Barnes TSX and TTSX bullets for my .257 Roberts, .257 Wby, 6.5 PRC, 270 WSM, .280 Rem., .30-06, and .375 Ruger. In every instance, except with the Weatherby, these bullets are seated with the case mouth in the middle of the top band. Accuracy with all of them is MOA or sub-MOA, in the case of the 6.5 PRC, sub .5 MOA. I have no idea of what the 'magic' is with this phenomenon, but these bullets are clearly well off the lands of each particular rifle. For me, this is more than acceptable hunting accuracy.

To get an accurate length measurement you should be measuring from the cartridge base to the ogive on the bullet because the overall length of the bullet can vary quite a bit especially with lead tipped bullets. I load everything with the bullet ogive .010 from the rifling and play with the amount of powder. So far it's been working good on every rifle I load for.

I use a Hornady OAL Gauge and a Hornady Bullet Comparator Kit to determine the base of the case to the bullet ogive length. To use the OAL gauge you'll need a drilled and tapped case that Hornady will sell you but they're very scarce right now. It's better if you send them a fired case (leave the primer in) from your rifle anyway so it will have the same base to shoulder length as your rifle. They'll drill and tap your case of them for $15. I also use one of Hornady's Headspace Comparator Kits so I find the base to shoulder measurement of fired cases and bump the shoulder back .002" when I resize the cases.

I worked up all my loads years ago before everything got so expensive and so unavailable.

I start .010 off lands and go .030 increments out to .130

Take the group with the tightest horizontal string and start dialing in the vertical string by adding powder

I had a sizable response but decided to let it go. Not the time to teach some old dogs new tricks.

Berger suggests increments of .040". Barnes suggests .025" increments. Some as small as .003". YMMV but I do suggest COAL testing as a way to shrink groups. Do this AFTER finding the powder charge you wish to stay with; one that will give low ES/SD.

Alan

Why? Some of use old dogs would like to hear what you have to say

You need to know where the lands are to begin with. Most here do not, they just start at an arbitrary number and then fu ck around with seating depth. Also, you can play with seating depth, but for most shooters (who are not in competition) a simple .020" off will suffice for hunting ammo with cup and core or even lead controlled expansion bullets and .100" off for mono metals, then find your optimum charge weight and accuracy node. I'm willing to listen Alan, wondering how you did in the MOA all day long competition here? If you can teach me that your way is better, I'm all ears.... Also, all this talk about accuracy and I'm wondering how many here use a good concentricity guage or even know how to properly set up their die sets. How many here properly glass bed their rifles? Too much egg before the chicken shidt going on here, if you catch my drift... I'll bring up something that really hit home. I was at the range 2 weekends ago and a new club member was putzing around with his 7mm Christensen arms rifle that was decked out and sitting in a nifty chassis unit. Pretty cool piece of high dollar machinery. He was talking to a member of my club when I pulled up and when I got out, I heard him telling the old member how "you load for precision". My ears perked up and I began to listen. Sounded like some pretty cool chidt for sure. Micrometer adjust die sets, digital scales, neck sizing dies and bushings, redding, Lapua and Forster, along with Extreme spreads and SD's were tossed in to spice up the lingo as well. I told my buddy, the old club member there, "he needs to come to some of our centerfire matches, I'm wondering how badly he's going to beat our azzes". The new member standing right there.. I then ask how long this new member has been hand loading. His response, "5 months".... He was real pizzed when my iron sight Swedish mauser shot better than his fancy Christensen Arms long range precision rifle... Long story short, last weekend, the new member comes up to me and tells me he doesn't know what he did wrong, his ammo won't chamber in his rifle now.... He took all the measurements and by his calculations, he should be a certain distance off the lands, "but the ammo will not chamber". Keep in mind, this guy is an engineer. Moral of story: even all knowing engineers should learn the KISS approach, until they have years of hand loading experience under their belt.

I've been reloading for nearly 50 years and always used the SAAMI specified COAL, never changed. I've always been able to get acceptable groups by changing powder/charge.