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

There are several things that can affect accuracy. Most shooters are aware of OAL as it relates to the distance from the ogive to the lands. Bullet construction affects it as well. Copper versus cup and core. How thick the jacket and the lead hardness influence cup and core bullets.

The single biggest factor for me however is reliable functioning. Animals fall over whether the rifle groups 1 inch or 3 @ 100 yd. To a point. For deer, my yardstick is an 8.5x11 sheet of paper. If I determine that the maximum range of encounter will be 200 yd., then as long as my handloads hit that piece of paper, it's golden.

If the max range is 400 yd, as long as it hits that paper, I'm happy. That is why I make my own targets using 8.5x11 paper. It's not just convenience of std sized paper.

Dang! I'm impressed. Totally clueless, but impressed.

Always thought of you as that folksy guy from the frozen North in the hat.

Actually, after looking at it again, it 'splains some things. Got some .243s loaded with E-tips that were very diasappointing today at the range. Gonna take the rest back when it's not so dang hot, along with my Lee loader and play with the seating depth.

Jerry,

You mean this post from about a week ago?--

Distance to the lands can change for several reasons other than a new manufacturing batch of bullets:

1) Throat erosion. This doesn't happen significantly in the typical big game rifle owned by average hunters, but you never know. They might try some "fire-lapping" bullets, which can change the lands significantly in just a few shots.

2) "Distance to the lands" is a rather vague measurement, especially with factory rifles. I don't run into many with all the lands lands the SAME distance in front of the chamber, because the reamer's a little off-center in the bore. Have seen plenty through the bore-scope with lands a LOT longer than the others. The typical tool for measuring distance to the lands measures to the LONGEST land, not all of 'em.

Which is why I depend more on my bore-scope and land-impressions on seated/chambered bullets than any tool. Though the tools work great in custom-chambered barrels, where the lands in front of the chamber are typically very even.

Well, maybe so........



Wow, a WEEK sure has gotten longer. I'm now old ENUFF that time MAYBE slippin.


OKAY - mathman, I take it back. You don't get the credit.

Sorry M D, Thnx for reminding me.


Jerry

Seems like a certain Alaska fellow that used to post here mentioned it a time or two as well.

Mike

Something I've wondered, but haven't yet studied, is whether optimum seating depth changes with things like neck tension, primer type, or even powder charge. In other words, if best accuracy in a certain load with CCI 200 primers is at 2.820" for example, will it always be at 2.820" with say CCI 250 or Fed 210M primers, or maybe better accuracy at a different seating depth. Have any of you tested this?

I like a clay pigeon at 300 yards standard.

M M

I had not read that..... You had to quote it . Gee Whiz

I hope we have folks with at least 2 brain cells.

IMO, no commentS are necessary. That speaks volumes of the "author".


Jerry

Good stuff here from both posters. I bet Shrapnel has whacked a crap load of critters as has dogzapper and never gave a thought to printing cloverleafs or chasing rainbows. They just hunt.

I handload for precision because I like to do it in and of itself. I'm not delusional about being able to hold that last quarter MOA in the field.

Don't let that stuff fool ya. I learned long ago that the only way to deal with engineers was to understand why they are the way they are.

I went to university and found out the difference between passin' or failin' an exam was directly proportional to the amount of beer consumed, and inversely proportional to the amount of sleep you got. Them math lessons helped me explain to young engineers why theoretical calculations don't always work in the real world. That, and rough bores, or bullets that ain't round. And that ogives don't always start bendin' at the same spot on yer shank. Different lots of powder. Changin' primers. Changin' firearms. Changin' shooters. Changin' weather, etc. The only constant is change.

And, of course, animals with catcher's mitts. Did you know that most moose are left hooved?

You will probably never know how close to the truth you are. Worrying about things over which you have little or no control takes away from a good hunt.



We all have standards. One of my profs used to say, depending on who you talk to, standards can be different.

Today and yesterday I have been trying to improve on 1.1 inch groups I have been getting in a new Weatherby Vanguard 30-06. I'm using IMR 4895 at 46.0 grains hoping for a velocity between 2600 and 2700 fps. Using two bullets the 150 gr Partition and the Hornady spire point I have seated bullets from .005 to .050 off the rifling. The Partition shoots best almost touching the lands, the Hornady .050 off. But I can't seem to get a five into an inch! Could be the large empty space in the case or I need to raise the pressure a bit by marching up one grain at a time til accuracy improves. Or maybe use a slower powder and get a better case fill. This actually is just an excuse to burn powder as the rifle is giving plenty of accuracy for a treestand load but I want em all touching!

Well not the first time that I have been doing things backwards, like those Hiuka warries that take baths in dirt and ride facing rearward.

This makes sense but my question is will the optimal seating depth work for various powder charges with the same powder or with a different powder? My take was it is a factor in the engraving the lands into the bullet and barrel harmonics which I thought could change with charge weight, a different powder or changes in velocity?

I get the alignment thing like the dragster that shimmy's all over the place won't catch one with a smoother take off but beyond that I am still not clear of what the critical factors are that determine optimal seating depth.

But if it is consistent then it will save powder and make it easier to find the optimal charge weight.

I decided to do the case filling with another powder, WC852. Put 59.5 grains in for a lightly compressed load and it seemed a bit fast for what I wanted so I dropped the charge level to 58.0 grains for just a small amount of airspace. Perfect 3 in 5/8ths of an inch with the Partition. However I only had three loaded and it's 97 degrees out there. If I can duplicate this a few times or break an inch with five shots I will be good.

By "low to middle weight" charge do they mean a grain or two below max?

Then what increments in OAL do you try for seating depth? Slowly start working out in .005 increments with 3 or 5-shot groups or try .005 off then say .050 off and .100 off? Other?

I've loaded single rounds in .3gn increments up to roughly .3gn over book max, then fired them over a chrono to see if I find any pressure signs. Using that info I pick a safe max and then load and shoot groups close to lands, middle and far off. I'll then refine off the best of the three. With Barnes TTSX I just use .050 off and it typically works very well. If necessary I may try .070 or .030. That method does not refine the powder load for accuracy. Alternatively, I have loaded and shot groups at a set OAL but in powder increments up to my max. That leaves out OAL as a variable for accuracy. This begs the question, is powder load or OAL more important to vary when looking for accuracy. What Berger and Scenarshooter are implying is that OAL is a bigger driver.

I'm open to alternative paths to a good load.

With monos, the best seating depth (distance off the lands) is rifle dependent, not load dependent. If a rifle is shooting it's best at a given seating depth with that mono, in my experience it tends to prefer that depth no matter the brass, powder charge, the powder type or primer. The accuracy may increase or decrease as you change THOSE elements, but if you go fooling with the seating depth after you find optimal it always seems to decrease. I have never tested whether neck tension changes a mono's preferred seating depth in a given rifle, but I have seen strong evidence it does not matter. Multiple firings of the same brass over a day's work ups could be expected to change tension some. Different brass requiring the same seating depth is also probably evidence of that as well.

This only with monos however. Because certain rifles can be very sensitive to seating depth with monos I can see merit in the argument to find seating depth first, but because charge weights can also be responsible for very poor accuracy it can be difficult to find the best seating depth first Lots of rifle shoot 3-4 inch groups with monos when either the seating depth is wrong or the charge weight is wrong and when both are right they will drop in under an inch.

Maybe the touchiest I have seen was a 26 inch barreled .223 with 70 grain TSXs. .005 in either direction from optimal and it shot 8 inch groups. Well under an inch though at optimal.

Miles,

What powder did you use in that load?

John,

Do you find that optimal seating depth varies with powder charge, all else being equal? Back to the original question: If you find a seating depth at a moderate charge, can you improve accuracy by tinkering with the seating depth at max charge?

I realize this is in the realm of, "How small are your deer anyway?"

Mostly I find that i'm limited by max magazine length.

Jon

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