I load one at a time when testing and of course have been bit when finding best coal was longer than magazine length for some rifles. I just don't get to shoot enough to really ring things out as I would like.

So, I tend to find best powder load and adjust fit to magazine as tightly as function allows. I have a feeling I am not alone.

After reaching this point have you tried going shorter OAL and if so, found improved accuracy?

Not alone. I am on a quest to make my 300 Winmag loads magazine length and seat the heavy and long bullets to work out of the mag. I’ll report back. 😎

The common knowledge has it that closer to the lands produces the best accuracy. Thus, I’ve always just seated .03” short of the lands and went with that. However, not everything is “etched in stone”. A couple of years ago I had developed a load for my 7x57 using 145 gr. Speer HC, PRVI brass and RL19 powder - seated .03” short as usual. It produced about 1-1/4” groups which is more than adequate for my purposes. (deer sized critters out to 300 yd. max.).
Last summer I got to thinking that this load just might have better accuracy potential so I started farting around with the OAL. To my surprise, a .07” jump produced sub MOA groups at 100 meters. At first I thought it might be a fluke however more shooting confirmed my findings. Five 3-shot groups averaged .88”.
You just never know for sure until you try.

Not good with math so please bear with me. Your original group was about 1 1/4" seat .003 off the lands. But you improved it to .88 by going to .007 off the lands. ! 1/4 was good for what you do according to you but by experimenting you got it down to .88". So you actually only improved .370"! Was it worth the effort? The best one of my rifles does is 1 1/4" from a rest. Strictly a hunting rifle for big game and I have never bother to improve it. On the other hand I have a couple 243's I don't use on big game that do right at 1/2". Would like to improve them but haven't a clue why! My best guess is simply, "just because".

I like your limiting your shot's to 300 yards, probably because I do the same! Yet I have shot at only one deer at 300yds in my life. I didn't need to, I did it just to say I had, just because! I think we might all be guilty of that.

With a little practice 300 yards isn't a big deal per se.

Actually the “jump” numbers were .03” and .07”. Regardless, I agree with you that the difference between .88” an 1.25” groups isn’t gonna make a whit of difference for putting meat in the freezer. Your stated best guess, “just because” is totally correct. It was in interesting experiment.😁

FWIW, from JB's The Big Book of Gun Gack, pg. 20-21: "One of the oldest myths in handloading is that the best accuracy is always obtained by seating bullets very close to the rifling . . . . In reality many rifles shoot most accurately with bullets seated well off the lands. . . . However, it is a good idea to start by seating bullets out as far as possible, whether very close to the lands or to the the limits of the magazine. After determining which powder charge is most accurate, I load up some new 4-round batches, turning the stem on the seating die one full turn for each batch. . . .(Seating rifle bullets deeper is perfectly safe, because pressure decreases with the bullet further from the lands. You may have heard that pressures increase when bullets are seated deeper, but that's true only with fast-burning handgun powders. It does NOT apply to modern rifle cartridges and slow-burning, progressive powders.)"

I haven't personally gotten around to using this technique, but I intend to give it a try.

Ever read anything on Optimum Charge Weight (OCW) and Optimum Barrel Time (OBT)?

They agree with your observations (from my reading) VG has been looking over and may have a more valuable take on it...

I'll share the test protocol I use to determine seating depth. I learned if from an old bench rest guy, and it works pretty well.

Background info: I and others see evidence that accurate seating depths come in "nodes". For example, if you find that 0.020" off the lands works, there will be a couple more lengths that work in approximately 0.060" increments. So, 0.020", 0.080", 0.140" off the lands might all perform equally.

I start 0.010" off the lands and test in 0.010" increments. Typically, you'll find a depth that works if you try 0.010" - 0.080" off. There may well be other nodes as stated above. This is important because most factory chambers are throated VERY long, so long you commonly can't get within 1/8" of the lands. If that's the case, I'll start with the longest COAL that will fit in the magazine and step back in the same 0.010" increments.

Here's the wrinkle with the test protocol. I load 3 or 4 rounds at each seating depth, but I deliberately screw up the powder charges within those 3 or 4. I'll load one at the normal charge weight and then step back the charge in 0.5g increments. In case that's not clear, I'll load (for example) one round each at say 24.0g, 23.5g, 23.0g and 22.5g. All four are at the same COAL.

Deliberately messing with the charge weights makes it MUCH easier to see which seating depths work best. I just ran this test again a couple days ago. The worst group was 1.5". The best was 0.5". Quite an improvement!

It doesn't always work that well, but typically it's possible to discern a COAL that is detectably better.

Seating depth ladders never ever prove anything. Here’s 5 groups 5-10-20-30-40 off. Interesting how it can work, group 5 was 30 off.

All you are doing is finding an accuracy node. You can do the same thing by adjusting charge weight.

You change a variable like seating depth, you will have to adjust charge weight to land back on an accuracy node. The only time I go shorter on OAL is if my group has an anomaly like 2 groups in one. IE: 2 shots clustered and 3 shots clustered elsewhere. That is the only time I'll increase jump to the lands. 9 times out of 10, I'll find a good load with the bullet backed off the lands by .020", If the mag box will allow that length. If not, I do like you said and load them to mag box length and find the appropriate charge weight. It's pretty easy to see a good load starting to develop. Here's one I found for my AR10. Ridiculously easy to see what's going on with the node when bullets are put on paper:





Here's another example of how you adjust charge weight when you change something critical like OAL:

These 2 loads showed the most promise, so I shot 2 10 shot groups side by side to see which one was ultimately better....

Developing good accurate loads is simple. It doesn't take countless hours/days or multiple boxes of ammo to find a good load. Just one range session and some good trigger time.

Anybody ever check ES velocity spread when tuning seating depth ?

Like Tom K 20k off - check velocity spreads down to 80k off ?

Nope didn’t bother but I did shoot 10 shots across a 35P to see what it was doing. Turned out to be about 100 fps faster than the 117 grain load of 52.5 RL22 with similar results which I have been shooting out of a 25.06 of some flavor for 25-30 years. I don’t think I can improve the numbers much, isn’t a barn burner but damn consistent and accurate.

Yes, and it does change, both velocity and spread. Find the depth that gives best accuracy first though, and then play with velocity and spreads by changing other variables.

Interesting, I like that. I haven't tried that method of deliberately varying the charge weight for a each seating depth, but will. It makes a lot of sense.

I've not noticed depth changing velocity or SD's, but I've not looked for it. I don't typically make large jumps to different nodes, usually just fiddling around in the 0.030" or so where I think they should shoot. I'm a dedicated record keeper, though, so I'll go back in the data and have a look. It makes total sense that a change should affect pressure and thus velocity..

I'm just getting ready to test a load that I'm jumping 0.020" currently to the next node shorter. I'll keep an eye on what happens. The SD's on it are single digit, so I should be able to detect a change if there is one.

!

Great stuff , thanks guys . Hope I can do some serious testing of this. Will toss out that one major example of loading off the lands I got was listening to Weatherby owners and reading about free bore etc...

I had some trouble getting a Berger bullet to shoot acceptably in a 6.5x284 so I went to their site. (never read the instructions)...
On their home page you'll find the Resources tab and Making it Shoot is there.
It's basically the same info that Tim K posted and it was what I needed for the Berger bullets but it works with others of course.

Let us know what you figure out!

Here's that article about Berger bullets.

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

The only condition I would add is that any bullet that is asked to jump a large distance to the rifling better have the chamber as concentric and parallel to the centerline of the bore as is possible.

Just read it- VERY interesting. I remember someone posting here a while back that he discovered seating depth had a greater impact than powder charge. We should have made a sticky out of that post.

I got some new bullets coming this week!!!

Timk - you get to shoot yet?

Ammo is loaded, hoping to get out tomorrow.

So another question regarding this. Real World. What IF.......you have to begin your loads at magazine length rather than "off the lands"?

You can go shorter from there.

I guess I will give it a try until I get to factory spec length. Thanks Mathman.

Lately I've been playing with a rifle that likes them seated shorter. I just had to test it to find out.

Latest test. This is on a .224 Valkyrie. Shortest is 0.010" below mag length (2.250"). Longest is 0.030" longer than mag length. My mags will allow me to go longer if desired, but it sure appears to like a little more jump.

The dimensions on the targets correspond to the direct reading off the caliper using a bullet comparator. Hence the confusion. All shot indoors at 100Y. I got good breaks on all but one shot that went off a touch early.

https://i.imgur.com/gLPsmZo.jpg

In my experience, chasing the lands is overrated, at least in typical hunting and varmint rifles.

A lot of my precision rifle shooting is with the AR15 platform these days, so cartridge length is generally limited to 2.310" or shorter. In several cases with the most accurate setups, I've found best accuracy at much shorter overall length, like 2.235", despite that being .050"-.100" off the lands, or more. Other times close to the lands does work best, but it's definitely not a hard rule or even common enough to bet money on.

For my purposes, I start with the shorter of either mag length or max length to the lands. In many cases, that means going with mag length or shorter, which generally is no handicap if you're willing to experiment. Don't hesitate to go significantly shorter than mag length; I like to test to at least .100" shorter if possible. Jumping in increments of .030" works to get started, then fine tune in smaller increments depending how much care you want to put into loading. With a lot of bullets and applications, it seems to me that it's not worth chasing anything finer than about .010".

You know- I guess this is beginning to explain accurate Weatherby's.

Getting excited to shoot again here !

Tim K - I did the math and your best load is .04 deeper which is the increment suggested in the Berger article. Cool stuff. I had a dozen or so already loaded with a standard load and last night i shrank 3 by .04 and the final 3 by an additional .04. Going to do the same for my 6mm. Wish I had my own range and means to more easily shoot and test.

Once I find sweet spot COAL I can tinker a bit more with the powder charges.

Man- I used a comparator to measure from Ogive on the Sierra's then loaded some Speers and the differences were pronounced. Gonna go blast through what I got but...will probably be scratching my head when I am done. No idea how far off the lands I am because I stated at mag length. Sigh.

Just returned from the range :and the ringing out my initial less than perfect control group testing.

6mm REM: meh
I never had a 'great' load for the 105 grain Speers in my 6mm so I dug up a pet load with same powder from another guy who said it worked in several rifles. His was one grain more than mine and getting close to max so I thought it might be worth a try on these heavy bullets based on comments byu some folks here.

My standard load length worked best and it was the longest COAL. Was rather hoping a shorter length might surprise me. I am thinking I may just stick with 100 Sierra - or maybe some Gamechangers.

On to my 260 REM:
No surprise that my old formula for 120 Sierras shoot well. Like the 6mm this was the longest COAL and I worked down from this length.
Next load .04 shorter - not so great.
going shorter another .04 - worse.

At this point I was thinking conventional practice of loading as long as possible seemed a good rule but I still had my shortest COAL to try
Shot last loads - .04 shorter still
AND......BOOM- awesome. One ragged string.

This is great news as it means more mag space. So, if I want to migrate off the Sierra's and go to the Gold Dots I just bought I have the ogive length and will match that as close as possible and load with same powder weight.,


Should work- right?

Fun stuff- beats Carona-ing around all day !!!

Guys, just got back from a well planned range trip and things begin to make a lot of sense. Like.....accuracy depends mostly on the timing the bullets exit from the muzzle. Crazy or ??/


Today was nice and chilly so off I went to the range. social distancing....Ugh.

Using the .04 step I was very surprised at some of the results. Differences were every bit as much, or more, of an impact than ladder stepping powder charges.

Made Identical loads for 3 different seating depths for my 260 and my 6mm.

POI was noticeably different between depths. In both cases the #2 seating depth produced much better groups than deeper or shorter.

Longest loads produced close to 2 inch groups. Amazingly, .04 shorter gave my 260 a great clover leaf and tight slight string in my 6mm.

I did a load of other bullets but am finally committed to over simplifying, de-mystifying, and idiot proofing against myself.

From now on (or at least until l I re-stupid myself listening to others) I will be : sticking with Sierras, one powder for all three deer cartridges , using light powder loads because A) I am using Sierras and B) no need for long range shots.
One more bonus. I got a new prescription for contacts and was told my eyes had change and prior prescrip was over correcting. Man, took out the 1911 and could clearly see the sights this time ( not a fuzzy wad) and shot like I would love to always shoot! So happy.

All in all, A great day for me fellas !!!