seating depth

[rick smith]

Using a Redding or Forster competition seater I can keep seating depths within 0.001". At 0.005 I would be either bumping the bullet back out and reseating or bumping the bullet with a slight amount of pressure. I have seen a change in group size with a 0.005 change in seating depth so I don't allow more than 0.001 in either direction. I measure all my loaded rounds with a comparator and don't have as much varation as you are reporting. I also prelube the inside of the case necks with a home made dry lube and then run a nylon brush through the necks to remove any excess. Tried the steel wool on the inside of the necks but saw no improvement in the rounds so abandoned that. Seating part the way and rotating for the remaining is not necessary. I have tried it many times since it is suppose to improve concentricity. I have never seen it make any difference and it has no effect on seating depth. I use Type "S" bushing seaters whenever possible but your method should be just as good. I have played chase the lands with a number of rifles and have never seen the lands move 0.005 in 50 rounds. I use to measure each bullet and sort them before seating but found I could load with more efficiently by seating and measureing the seated bullet then adjusting.
The Berger reasearch, if you are talking about their suggested seating depth, tells you to try their bullets at a certain number of thousants off the lands. All that tells me is that most rifles have more than one sweet spot and they are suggesting what to try. Has nothing to do with trying to maintain a constant measured serating depth.
I am using a Forster Co-Ax for seating and simply don't have a problem maintaining 0.001 variance in seating depth for most rounds, I adjust the individual rounds if necessary.Rick.

 

[hardpan]

For the recommendation of .005" changes in seating depth, is that for the whole range of possible seating depths

e.g., .030"-.100"= 14 different seating depths = 42 rounds of 3-shot groups.

or is that for fine tuning once you have isolated a general range of good seating depths

e.g., .030", 0.60", .090", .120" 3-rnd test groups, Best group at .090",
Then
.080", .085", .095", .100" = 27 rounds in total

x2

Most of the time it is extremely difficult to seat your bullets with less than .005" variance and IME you will not notice a large difference between groups with only .005" change in seating depth. By the time you get to the end of the range you needed to test your throat would have eroded more than you are varying seating depth. Not to mention you would have spend a helluva lot of money and time.

IMO .010" difference and .020" would not be out of the question. Some rifles have long throats and you can't seat closer than .250" and they manage to shoot fine. There is an article about Bergers that I will try to find and the seating depth variances between groups were more like .030".

Found it here http://www.longrangehunting.com/forums/ ... fle-40204/

Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

Solution

The following has been verified by numerous shooters in many rifles using bullets of different calibers and weights. It is consistent for all VLD bullets. What has been discovered is that VLD bullets shoot best when loaded to a COAL that puts the bullet in a “sweet spot”. This sweet spot is a band .030 to .040 wide and is located anywhere between jamming the bullets into the lands and .150 jump off the lands.

Note: When discussing jam and jump I am referring to the distance from the area of the bearing surface that engages the rifling and the rifling itself. There are many products that allow you to measure these critical dimensions. Some are better than others. I won’t be going into the methods of measuring jam and jump. If you are not familiar with this aspect of reloading it is critically important that you understand this concept before you attempt this test.

Many reloaders feel (and I tend to agree) that meaningful COAL adjustments are .002 to .005. Every once in a while I might adjust the COAL by .010 but this seems like I am moving the bullet the length of a football field. The only way a shooter will be able to benefit from this situation is to let go of this opinion that more than .010 change is too much (me included).

Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don’t give up first. Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:
1. .010 into (touching) the lands (jam) 6 rounds
2. .040 off the lands (jump) 6 rounds
3. .080 off the lands (jump) 6 rounds
4. .120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:
1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards).

Regards,
Eric Stecker
Master Bulletsmith

Mr Woods,
Thanks for the post. While not appropriate for Bees due to their very long freebore, the idea does have some merit. If the sweet spot is really 0.030 to 0.040, then I am wasting a time and money moving as little as I do. So, for my next round of loads, I am going to try this one out..

If you use this method, then how do you marry it into finding the right powder and bullet combo? RIght now, I tend to see larger differences with powders and then I try to get to the optimal COAL.

thanks,
Hardpan

 

[woods]

Hey Hardpan

I personally do not use the Berger bullets and posted their method as an illustration of how far some reloaders jump when testing for seating depth. That was as a contrast to the seemingly overwhelming opinion of using .005". However there is no wrong way to do it, just different ways.

My method with a new rifle is to seat at .025" off (.050" for Barnes) and work with the powder charge. IME & IMO if you find an accuracy node with a certain powder charge and vary the seating depth then you stay close to the accuracy, BUT if you vary the seating depth and find accuracy and then vary the powder charge you will have to start all over again with seating depth. So I stay at .025" off and work the hell out of different powders, different charge weights and even different primers. Once I find what I want if it is not good enough (90% of the time it is) then I will vary seating depth by .015" away from the lands for 2 or 3 loads and one step in toward the lands at .015" off.

So I agree with you that work the other factors first and seating depth last.