Bullet Seating Depth

d2admin

Administrator
I am new to reloading and have started playing with the bullet seating depth a little bit. I dont have a bullet puller yet, and wonder if there is any way to tell at what depth the die is set at (other than trial and error). This has become kind of a pain in the butt for me! I guess i need to get myself a bullet puller. I know this may be a stupid question to you master reloaders but any help is appreciated! Thanks!
 
Actually its a very good question. You need a Stoney Point bullet comparator and a set of good dial calipers. You will probably find that bullets seated just off the rifling will shoot the most accurate. Check this by coloring the bullet with a majic marker and start with it seated long then chamber it and look for the rifling marks. Go in with the bullets seating depth till the rifling quits marking it and this is a good place to try for accuracy. Of course do this with a dummy round when getting the measurement. You will use the comparator to get an accurate cartridge overall length in thousands so you can set up the dies with different bullets once you know the depth. The comparator measures from a datum line {certain diameter circle} on the bullet. Sounds complicated but its simple, good luck.
 
I have some thoughts about seating depth and tools that maybe someone with more knowhow can add to or steer me right. I have the Stoney Point comparator with dummy rounds for .223 and .300 wsm and also an RCBS "precision micrometer" for the .300. Almost all my experience is with the .223 since the .300 is a new gun for me and I've only reloaded a few rounds for it. First, I agree with the posts (here or maybe other forums) saying that the Stoney Point tool gives inconsistent readings when inserting the dummy cartridges. I can get what I think are significantly different measurements even with the exact same bullet no matter how careful I try to be, especially with the .223. Second, you'd think that when you've found, say, .02 off the lands for one bullet the cartride length to that point will be the same for any other bullet with the same type of ogive. That might not always true, however. For example, the Ballistic Silvertip 50 to the lands on my gun measures on average 1.963" and the Ballistic Silvertip 55 1.973". This type of discrepency might be a function of the measuring tool, bullet construction, or both, or other things. I don't know. Third, I don't think there really are hard and fast rules about how far off the lands is optimal for a given caliber, anyway. The concensus seems to be for a .22 caliber that about .02" off the lands is best. I have two favorite accuracy loads for my .223 (at 100 yds). One is the Silvertip 50 with 23.4 grains of xmr2015 at an oal of 2.232" (1.820" -1.823" by the comparator, or .14" or so off the lands), and the other is the Silvertip 55 with 27.5 grains of Varget at 1.952" on the compartor (or about .02" off the lands). As an aside, for some reason the Silvertips consistently outperform Sierra, Speer and A-Max 52s in my rifle. Anyhow, this is a huge "off the lands" difference. Of course, 40 grain bullets have no chance of even coming close to the lands but there are some very accurate loads for those, too. I've also read that some people think the same round can have two (or more?) seating depth "sweet spots" and I have no reason to think they can't. Overall, I'd say that there are so many variables that messing around with different powders, charges, bullet weights, etc is critical to coming up with an accuracy load and the "off the lands" issue is just one of several considerations. By the way, my .223 is a 700 vs which has had absolutely no problems (not to start this war again!)except for the heavy trigger, was accurate out of the box and has no mods except a Jewell trigger. I also put a Weaver v24 scope on it which has got to be one of the best bargains out there. The .300 is a model 70 ss which is a long-range "project" gun. I have an HS Precision stock for it and will eventually rebarrel it and also get a Jewell trigger.
 
Welcome to the board estorm! /ubbthreads/images/graemlins/laugh.gif

I do think that seating distance is about the last thing to worry about when tweaking loads. Unless you are into serious benchrest shooting, you will have a hard time measuring the difference on target.

There is one exception. The VLD bullets normally require that they be jammed into the lands.

Jack
 
I have found that if you seat the bullet to the max overall length for the round used and adjust accuracy by powder charge variations I have had much better luck and less headache. Just my .02 worth.

Kirk
 
Boy Jack, all the things you've posted that I've read I've pretty much agreed on. Except this one. I'm probably wrong since I'm basing my opinion on just the last two cartridges I've shot for accuracy, but.... With the .223 Savage and the 7BR it has made a BIG difference in group size adjusting the seating depth. I would almost go so far as to say it has made more difference than the charge. Maybe It's the way I work a load too. Maybe others would like to laugh at my methods too so here goes.
Generally I peruse the powders to find one that maybe uses the least to FILL the case and try to make it something easy to meter since I don't weigh charges. I then adjust and shoot to get a mear max and with that charge I then adjust seating depth from a long stiff bolt seat down in 1/4 turn increments. The groups will always decrease and then start wandering again. Fine tune in smaller increments at the breakover point gets the nitty-gritty groups. The large to small group changes will generally be in the neighborhood of a better than 50% change. Real significant to me. Loren
 
Dk, good talking to on IM last night.

Anyway, I have to agree with Jack and don't worry too much about OAL, at least starting out. The manuals lists 2.260" & should be fine.

More often than not, you will generally notice no practical difference in accuracy anyway. Especially with a 223, a very forgiving round for sure. Always exceptions however, as someone stated above.

As you probably already know, you have to worry about magazine length too, as it can dictate how long/short your bullets can be anyhow.

ALSO, you can actually L-O-S-E accuracy the closer to the lands you get. It's happened to me more than once. On a previous 22-250 and my current 300 win mag for starters. And they both were/are Extremely accurate.

My current 22-250 "has" to be seated close to the lands and is nowhere near as accurate as my previous 22-250 that was seated a country mile from the lands.

Anyway, hope this helps and

Happy Shooting
 
Loren, your method can and does definitely work. Just a different way of approaching it. And, doing it that way, yes I agree seating depth is going to be a very important variable. The way I suspect Jack is going about it, is to test several powders until the groups get satisfactory. At that point, he's pretty darn near to where you are, and seating depth becomes only a fine tuning variable of not that much importance. Especially if the powder testing was done at or near the lands. The way I normally work up a load, seating depth isn't a biggie. In fact, I rarely even experiment with it anymore. I just start load development at, or very near the lands, and when I find accptable accuracy through bullet, powder and charge selection, I call it good and go kill critters!

About as many different ways to skin this cat as there are cat skinners.

- DAA
 
gotta agree with DOGGITTER. barrel vibration (and thus group size) appears to change with the velocity of the bullet at the time it hits the lands. a bullet seated close to the lands is moving slower when it hits than one seated back a ways, and thus the impact on the barrel is different.
had a 30-06 once with an unusually long throat and while experimenting with those short 110 grain "varmint" bullets, i found that a deeply seated bullet that had to travel a LONG ways before it hit the lands proved most accurate! odd, but that's what happened with that barrel.

keep in mind that the purpose of the browning BOSS adjustable muzzle weight was to fine-tune barrel vibrations to match up with a given lot of ammunition. and, although it was a pain in many ways, it did produce small groups.
 
I have found seating depth to be a large factor in the accuracy of my rifles, but only after finding a powder and charge the barrel favors. I have been experimenting with the ladder method of finding a powder charge, then after shooting the nodes to further refine the charge weight, I vary seating depth from .005 into the lands, to .020 off the lands. Lately I've been doing load development in a Cooper 22-250, and a custom 6-284. The 22-250 has shot reasonably well with every combination I've tried, but with bullets set at .005 off the lands it consistently shoots in the mid .3's. Closer or farther from the lands and groups open. The 6-284 shoots lousy with every load combination I've tried except that I found a mild load that showed promise. Today I shot test groups from touching the lands to .020 off the lands. Touching the lands produces slightly larger than MOA groups. -.020 produced a .412 5 shot. I'm going to the range tomorrow morning to shoot some more groups at -.020 to verify. I start testing at touching to .005 off the lands, and when testing seating depth I change in increments of .005.
 


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