what is the easy way of determining what depth I should seat a bullet? I know it depends on the ogive of each brand/weight of bullet and it can be done by blackening the bullet and seating it progressively further out until the lands mark the black.

Is this the only way? How do you guys do it?

everyone talks about seating depth and .00x off the lands and I am just wondering the best method to actually determine it.
Thanks

About the best money I ever spent was on a Stoney Point Overall Length gauge. It is now a Hornandy product called the Lock-N-Load O.A.L. Gauge. They cost about $30 and you need a modified case for each cartridge at about $4.50 ea. They are very easy to use, I can't imagine not having one now.

Seating depth gets foggy, especially to new guys. Actually, there are at least three major factors to be handled seperately.

First, forget book the OAL. It's not a law, it's not a SAAMOI specification, it's only what the book makers used when developing their data. Each of should try to find his won best seating depth and that's your question of course.

Step one, find the maximum length that you can chamber without the bullet falling out OR jamming into the lands. The old adage to seat one caliber deep is/was a good one in that it kept the bullets from moving when handled a bit rough but some current case necks are barely a full caliber long so the only rule is sorta moot.

Use any method you wish to find how far out the bullets can be seated to just touch the lands. I have the RCBS Precision Case Mic, some split-necked cases and Stoney Point/Hornady tools. I like them, but I still use the old marked cleaning rod method most often. It's quick, easy, plenty accurate.

Simply close the bolt on an empty chamber, insert the rod until it touches the bolt face and mark it even with the muzzle. Remove the bolt, drop a bullet into the chamber throat, hold it there with a pencil and mark the rod when it contacts the bullet's meplat. Using your dial/dgital caliper, measure between the two marks. That's your MAX OAL for that bullet. Don't sweat over being maybe a couple thousanths off, that isn't where you will be loading to anyway. It's just a reference for what's to follow.

Load up a dummy round according to the OAL marks on the rod. Use it it as a reference "set-up gage" for your seater when using that bullet.

Now, load your charge test cartridges .005" shorter than the dummy. Go to the range and test them to find your best charge at that seating depth.

Using the best charge, seat the next round of test cartriges in steps .005" deeper until you find the best seating depth. It can easily be as far as .125" off the lands, occasionally even more.

Finally, you may want to tweak the charge a few tenths either side of the chosen load to insure it's the best charge for the best depth. (Check that the OAL will feed through your magazine. If not, seat deeper until it does.)

Many will say "best accureacy" comes when touching the rifling. That's not so, not often anyway. It's commonly thought seating in the lands may help align the bullet to the bore but I doubt it has that effect.

Seating in the lands is a BR technique, used to retard bullet movement a moment tohelp obtain good igniton and burn rate from their often loosely seated bullets. We don't normally have that problem in our factory rifles so it's just not very helpful to us. Actually, a bit of bullet jump reduces peak pressure and finding the right jump sure helps accuracy.

Some will also protest that for greatest precision we should seat off the ogive, not the meplat. But, again, that's a BR thing with little application to those of us shooting factory rifles and common bullets.

Of course the various tool makers are happy to sell us various expensive tools to find just what we need to seat off the lands by .00004", +/- .0000001". But we just aren't that sensitive! In my experience fighting such minute factors (often to the point of being trivial), it finally seems provable that a few thousants seating variation doesn't mean a thing in factory rifles IF the load is a good one.

You will normally find a moderate range of seating depths, not a specific spot, in which accuracy is good. The range can easily be as wide as .020". Seat in the middle of that range and you will be fine, your load will be consistant.

This is true for the best powder charge range too, it's frequently several tenths of a grain wide. Just load in the middle of the good range for the fewest flyers.

Seat (or charge) on the ragged edge of the good range/window and your load WILL be quirky, producing "unexplainable fliers" from time to time. Actually, they ARE explainable!

+ 1 on the things mentioned by Jim C. <>< and Nimrod308.

Another thing to mention (not knowing whether it's relevant in your case), is that often times your OAL will be limited by your rifle's magazine (if any).

I have several rifles where I cannot get anywhere near the lands because of the magazine length. In this case I load them as long as I can while still functioning properly. All my rifles are repeaters, and I don't care to turn them into single-shots.

-nosualc

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Usinf your dial caliper, measure between the two marks

Hey Jim and guys. You don't measure between the marks when you use the cleaning rod method. You need to be measuring from the bottom of the first mark (rod on the bolt face) to the bottom of the second mark (rod on the bullet tip).

If you measure between the marks, your Max OAL will be off by the width in thousanths of one of your marks.


I've been using rubber O rings. First I measure the width of one of the rings and record. Then I slip one on the cleaning rod and insert the rod into the muzzle and push it down till it contacts the bolt face. While doing this the O ring contacts the crown first. Then I remove the bolt, drop a bullet in the throat, hold it with a pencil eraser. Slip on the other O ring on to the rod, insert it into the muzzle and push it in till the rod tip contacts the bullet tip.

Measure the outside distance of the O rings and subtract the width of 1 O ring to get your Max OAL.

that is pretty good info but if you wanna change bullets you need to know the measurement to the ogive you can then use the exact same measurement from brand to brand or lot to lot or even weight change of bullets.

Lamar,

If I change bullets in any way, I just re-measure with the bullet I'm trying to shoot. With your method you need what Hot Core calls a "thingy" (Bullet Comparator) to measure where the ogive is, don't you?

A bullet comparator. You get 'em from Sinclair. Used to determine the distance from the base to the ogive. Can also be used to determine cartridge length and for setting dies to seat bullets. Holes are made with throating reamers to duplicate the measurements in the chamber.

How, in detail Homebrewer, do you use that tool?

Thanks Jim, And all
the cleaning rod idea is a great one!
Thats the kind of thing I was looking for- It's so simple and easy even I can't screw it up.

I've read all the manuals but I don't really have anyone to mentor me in reloading- Thanks Guys.



The only method I have found in any of my manuals is by blacking with a sooty candle and progressively seating further out- Too darn much work for me.

Refined with the O-rings should be a patented idea its so good,

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How, in detail, Homebrewer, do you use that tool?

I use it primarily for sorting bullets. I place a bullet into the "30" hole (point in) and measure the distance from the base to the opposite side of the tool. Let's say this gives me a measurement of .750 inches. I set that bullet aside. I measure the next one. If it's +/- .001 inches from the first one, I begin collecting them into one pile. My tolerance for uniformity is that .001 inches. The third one I measure is .756 inches. And so begins a second pile, et cetera. You can measure completed rounds the very same way. This is how you can set the seating depth of your bullets. I use a dummy chamber my gunsmith made for me with the exact same, brand-new reamer he used to cut the chamber of my rifle. I am not sure he cut the chamber first or made the dummy first but with that few cuts on it, it hardly matters.

This is my dummy chamber.
Notice the ridge inside. The bore there is .300 inches-- exactly that of a 30-caliber rifle. I set my seating die so the dummy will freely spin on the loaded round, meaning the ogive is less than a red hair from the riflings. If there is even the slightest drag, I back off in 1/4-turn increments until it spins freely. Assuming the pitch of the thread on my RCBS seater die is 32tpi, 1/4-turn will be 1/128 inches, or .0078125 inches. So, I set my bullets a skosh beyond .008 inches from the riflings.

Very cool!

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Very cool!

I thought so, too, when it was 'splained to me what the thing did. It's a wonderful little thing to have...

So how do you compensate for throat erosion?

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So how do you compensate for throat erosion?

I ain't that good a shot to worry about it...

Actually, my loads are pretty tame. I use H4831SC or RL-22 powders in my 300WSM, limiting my charges to 65 grains under 180-grain MatchKings. I just shot a five-shot, 100-yard group on Sunday that measured .817 (c>c) for all five and .285 for the best three. I estimate I've shot the thing less than 1,000 rounds, and probably less than 750. I don't keep track of how many times it's been fired because I'm not a competitor. I just shoot for fun. I know I can print a small group; my best is .154 for three shots. When the groups grow beyond 1/2 MOA, I'll know something's up...

Sounds like you're a good shot to me!

I haven't worried about throat erosion yet either, but some guys here say you should. They say it is measureable in as little as 100 rounds.

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I haven't worried about throat erosion yet either, but some guys here say you should. They say it is measurable in as little as 100 rounds.

My barrel is a stainless Krieger. Just checked their site; they say they use 416. Is that a hard or soft steel?

I think it may be considered softer.

The Walther barrels are LW-50 and are considered hard I think

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don't measure between the marks when you use the cleaning rod method. You need to be measuring from the bottom of the first mark (rod on the bolt face) to the bottom of the second mark (rod on the bullet tip).

Yes, IF you use a felt tip marker with a broad mark.

I put a strip of plastic tape on my rod and mark it with a knife, thus I measure from one mark to the other. I also put a flat head (brass) screw in the rod so I'm not indexing the point of a bullet in the threaded hole.

One other thing to rember to do on a hunting rifle, is to make sure that the final loaded rounds will fit in the magazine. If your magazine holds 3 or 5 fill it up and make sure.

I have had buddies work at finding the most accurate load and then when it comes time to go hunting their new loads won't fit in the magazine.