Figuring out my seating depth


September 13, 2011, 11:02 PM
So tonight I have been playing with the Hornady OAL tool, the problem is, unless you have supreme control on the amount of pressure you use to push out the bullet, results vary. By far the majority of my results were in the .74 - .75 range, here are those results. So the mean is 748.9, the median is 748. So if I seat my bullet 30 hundredths shorter, I should seat to 718 on the ogive. However if I do that, my OAL to the tip of the bullet measures 3.243 and the OAL listed in my Hornady manual is 3.210 if you look at the picture that doesnít bring the rim to the cannelure. So my question is, is this right, or was I putting too much pressure on the OAL tool and pushing the bullet too far into the lands? Before this I was just seating to the bottom of the cannelure. I did check and I can chamber the round.

Bullet was a .270 130gr Interlock, gun was a browning a-bolt.


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September 14, 2011, 08:03 AM
The OAL listed in the manual is only a reference as to what they used. It means little to nothing as far as YOUR rifle is concerned.
Some manuals don't even list an OAL (Nosler). You are on the right track, find the Max OAL in your rifle and work back from there. If you want to crimp to the cannelure seat to that depth and crimp, if not ignore the cannelure.

September 14, 2011, 09:18 AM
Thanks, thats what I figured, I was just a little suprised how much lower the rim was.

September 14, 2011, 04:25 PM
The main thing that is accomplished when using the Hornady OAL tool is finding out how close to the lands you can seat a bullet to reduce the amount of unsupported jump when the cartridge is fired. You need to know that this maximum OAL MAY be too long to go into your magazine. Again, this is mostly used for wringing that last few hundredths of an inch in the diameter of your group sizes. A lot of us High Power shooters load at least 2 different bullets for one match. We shoot at 200, 300, and 600 yards. We load the 200 and 300 yard loads at MAGAZINE length because they are all fired from the magazine. Now, the 600 yard loads are loaded one at a time, and NOT from the magazine. This extra effort and tme may result in a few more points at that distance. Now, you stated that you have to pay attention when pressing the bullet into the lands. That is exactly correct. You have entered an area that requires more care in your loading. It takes extra care to make any significant gains in accuracy from that particular activity. And, the other real reason to seat the bullets long is that some bullets, like the Hornady 75 grain A-Max, in .224 caliber, cannot be loaded safely to SAAMI length, meaning magazine length. They are far longer than an HPBT 75 grain bullet. The 80 grain A-Max bullets are even longer. I hope that this is helpful. DennyMac

September 15, 2011, 09:12 AM
Yes all this info is helpfull, thanks

September 15, 2011, 10:58 AM
As previously stated, the OAL listed in reloading manuals is only what they used during load development. Two things I have learned thru years of load development: Have at least 1 caliber of your bullet (excluding the boattail) seated in the neck, and seat your bullets so the ogive is at least .010" off the leade (even Sierra's MatchKing bullets will vary up to .010" in ogive location). Also, in your case, ignore the cannelure and seat your bullet closer to the leade if it doesn't interfere with the previous statement.


September 15, 2011, 02:05 PM
So I took a case, cut slits down the neck into the shoulder, sanded the outside of the cuts down to 320 grit to remove any burs, then I sacrificed a bullet to lap the inside of the case neck. I then took a different bullet, seated it long, and pushed it into the chamber as far as I could with my bolt. The results where +/- .003 of .750, I think I did it 3-4 times. So that makes me feel better since I figured 748 with the Hornady tool. All the cartridges I loaded I seated to 715, so .035 short instead of .02 since I wasnít confident in my results before and wanted to error on the side of safety, but really for a hunting rifle, that should be sufficient. Thanks for all your help everybody, now itís time to go throw some lead downrange after work!

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