Home Forums Hunting & Shooting Ask The Gunwriters Something I've never heard before.........."seating depth first"

On the Berger websight there is information referring to working up handloads recommending starting at a low to middle charge weight and find the best seating depth first.

Has anyone tried this and does it work with other bullets such as hornady eld's?

I posted this in the gunwriter section because I'm looking for some hard facts about this information that come from what I consider to be a reliable source. If possible please try not to post " Grandpa told me so replies" Bullets have changed over the years and perhaps the way working up loads has a forseable change that is in the making at least with some bullets.

I tried to post the info but was unsuccessful so my apologies for that







Trystan

I've been doing it that way for years....long before the WWW.....;)

Thanks Scenarshooter! Have you used this method with different types and brands of bullets or is it more of a VLD type method?

I use it on all load development from the start.

Seating depth is the most overlooked accuracy enhancer out there IMO. You'll find optimum base to ogive will work with most bullets, regardless of the brand. In other words, Lapua, Berger, Hornady, and Sierra will all shoot well using the the same BTO in the same rifle....once you find it.

Hey Pat, is there an advantage to finding depth first? Or is it more a case of you have to start somewhere?

Pat,

What if the first charge you pick is right on a scatter node? Will that not swamp out the positive changes made by seating depth experimentation?

m

I've found the the same seating depth normally works on bullets of a certain type, but have found the most accurate seating depth can also vary considerably if different styles of bullets are used, say monolithics versus softer target-type bullets.

John (M.D.)

Do you determine seating depth early on per the OP's question or after determining powder charge?

It saves time, components, and barrel wear...I wish I had back all the powder and bullets I wasted trying to find the best loads before I learned about seating depth.

My rifles are used in the field, for either hunting, or shooting comps, so I need function, and reliability first and foremost. I stay away from seating too close to the lands. I don't want problems in the field with rounds that are hard to close the bolt on(I full length resize), or worse, sticking a bullet in the throat while removing a loaded round from the chamber. This happened once a few years back with a .308, while I was out on a coyote damage complaint. When I switched lot numbers on a fresh box of 1000 155gr scenars. The new lot had a little longer bearing surface and were jammed into the lands instead of out a few thousandths...my fault for not checking the length when I ran out of the old lot. The story had a happy ending as I called in a trio of adult coyotes from one location and started in on them at about 150 meters. the first two went down right away, but the third one took a broadside hit to the ribs and took off behind a large gumbo hill. I cycled another round into the chamber expecting him to appear after clearing the hill, but he never showed. It turned out to be a lethal hit. When I removed the live round from the chamber, the case came out, followed by 45.5grs of Varget into the locking ports, chamber, and trigger sear, rendering the rifle completely useless, for the time being anyway.....so in short, I try to stay away from getting too close. Most of my rifles shoot better with a safe jump anyway. Modern bullets and barrels are a lot better than they were 25 or so years ago. I start 5 thousandths off, and work back...and recheck BTO when lot numbers change...;)

MM: good question, but wouldn’t it apply in reverse: what if the first seating depth is right on the scatter node?

Gotta start somewhere...

I'm not following the idea of determining seating depth first. How does this work using a rather generic powder charge?

I normally shot 3 shots of the same powder in 1 grain increments for most big game cartridges. I see where it groups the best, then play with seating depth and incremental powder charges to fine tune. I'm interested in how to determine seating depth first.

My seating depth experimentation, all subsequent to narrowing down the charge, has not shown me as much difference as there was getting the powder charge about right. Can't say about the other way.

This in spades! When you are loading monos, seating depth does tend to be constant across velocity/charge weights. But...monos can and do exhibit considerable sensitvity to velocity and sorting out seating depth at the wrong velocity is entirely capable of teaching you that. I have one 25-06 that I still do not have solved because it is so touchy about velocity. I have/had a .243 that was likewise touchy about velocity. I have seen rifles quite capable of 8 inch groups at the wrong charge weight/velocity and the same rifle also capable of 8 inch groups at the wrong seating depth. In my experience the long barrels, 26 inchers, are more prone to this than shorter barrels and barrel weight does not necessarily mitigate that.

For me, I use fewer bullets trying to find optimum or near optimum charge weight than I do seeking seating depth. The most efficient (in terms of bullets wasted) method is if accuracy needs improvement with a mono is to move up to .005 off and start backing up .010 per iteration. Usually you find accuracy before you get back to .100 off and surprisingly often if I do not have accuracy at .050 off (where I start) it does tend to be very close to .005.

I have no idea in the beginning how to tell if the rifle is velocity sensitive with monos. I assume that all are seating sensitive with monos and find very few are not I have a couple of rifles that like monos right up against the lands or slightly jammed.

It may not be velocity sensitivity as much as barrel time sensitivity.

The faster the bullet the LESS barrel time.

The slower the bullet the MORE barrel time.

Well DUH ! !











Sorry M M, the door was open.........

Still Your Friend

Jerry

Not necessarily. You can have two loads with the same exit velocity but different barrel times. At the drag strip two cars can post the same mph but different elapsed times because their acceleration curves are different. Similarly, two propellants may give the same velocity but different barrel times because their burn characteristics are different.

I was actually lying in wait for a response like yours.

The faster the bullet the LESS barrel time.

The slower the bullet the MORE barrel time.

Well DUH ! !




WELL... I was NOT talking about 2 with the SAME velocity.

Faster ->-> & ->-> Slower

Jerry






I'm NOT arguing.

We used to see that while determining loads for specialized applications. Identical MVs, with the OAL adjusted so that the internal volume is identical.

Barnes 130 gr copper bullet

IMR powder 4895 had an exit velocity of 2750 fps and a barrel time of 1.139 ms. PMax - 40,669 psi
IMR powder 4064 had an exit velocity of 2750 fps and a barrel time of 1.080 ms. PMax - 43,527 psi

Hornady 130 gr cup and core SP

IMR powder 4895 had an exit velocity of 2750 fps and a barrel time of 1.145 ms. PMax - 40,132 psi
IMR powder 4064 had an exit velocity of 2750 fps and a barrel time of 1.109 ms. PMax - 43,086 psi

Check the Pmax for the two powders as they relate to the barrel time.

Another factor in seating depth is the "evenness" of the lands in the front of the chamber. In factory rifles, they're often of different lengths, due to the reamer not being perfectly centered in the bore. Thus a bullet will engrave on the "longest" land before engaging the others. I've often found such chambers shoot best with deeper-seated bullets, probably because the bullet gets more of a run at the lands before engraving, so doesn't get tilted as much by the longer lands on one side. I suspect this is one reason many monolithics shoot better when seated deeper.

At the other extreme, the lands in front of custom-chambered rifles normally have very even lands--and I've often found even monolithics to shoot best when seated pretty close to their lands.

But as an example of how differently even very similar bullet require different seating depths to shoot well, I once had a factory Weatherby Mark V that started shooting 130-grain Ballistic Tips into half-inch groups during the very first range session. All I'd done was seat them so the rounds would just fit in the magazine, since the Weatherby freebore prevented them from being seated anywhere near the lands.

Next I tried 130 Nosler E-Tips, using the same powder charges and seating depth. The E-Tips use a very similar ogive as the same caliberBallistic Tips, and in fact are essentially Ballistic Tips without a lead core. The E-Tips grouped into around an inch and a half, so I started seating them deeper. At a full 10th of an inch deeper than the Ballistic Tips they also shot into around 1/2".

Boy, that sounds familiar, like I've heard that before. (no criticism M D)

Don't tell anyone...shhh it may have been mathman (whisper)

Jerry