Finding "sweet spot" with bullet seating adjustment

[benchracer]

For those of you who have experienced finding a good load by adjusting seating depth what size steps did you take?

My bench rest friends take 0.003" to 0.005" steps. And Berger says you can take 0.040" steps.

The Berger methodology is effective. That was my starting point for seating depth tests. It works especially well with long bullets in chambers with generous freebore.

But, the Berger method doesn't work in every situation. For example, if one is working with a bullet that is too short to reach the lands, the seating depth test will have to be modified. I have approached such a situation by starting at book length and working forward.

In cases where your rifle has a short throat, or case capacity is limited, it may be best to shorten the testing interval. I have done exactly that, testing from .010 to .050 off the lands, and met with success.

It's important to understand that there are multiple seating depth nodes, not just one optimum seating depth. In general, it is best to match your seating depth test method to the application (based on bullet and chamber dimensions).

If you decide to follow the lead of bench rest shooters, understand that the bullet ogives often vary by more than .003 to .005 (yes, even Bergers). If you are going to take that approach, you will need to sort your bullets by ogive length first.

IMO, that is a waste of time in a hunting rifle. For just about anything besides bench rest, your time is better spent behind the rifle than chasing the last .1 MOA at the loading bench. To each his own, however...

 

[Rex Tharp]

The Berger methodology is effective. That was my starting point for seating depth tests. It works especially well with long bullets in chambers with generous freebore.

But, the Berger method doesn't work in every situation. For example, if one is working with a bullet that is too short to reach the lands, the seating depth test will have to be modified. I have approached such a situation by starting at book length and working forward.

In cases where your rifle has a short throat, or case capacity is limited, it may be best to shorten the testing interval. I have done exactly that, testing from .010 to .050 off the lands, and met with success.

It's important to understand that there are multiple seating depth nodes, not just one optimum seating depth. In general, it is best to match your seating depth test method to the application (based on bullet and chamber dimensions).

If you decide to follow the lead of bench rest shooters, understand that the bullet ogives often vary by more than .003 to .005 (yes, even Bergers). If you are going to take that approach, you will need to sort your bullets by ogive length first.

IMO, that is a waste of time in a hunting rifle. For just about anything besides bench rest, your time is better spent behind the rifle than chasing the last .1 MOA at the loading bench. To each his own, however...

I'm working on a load for the Hornady 75 grain V-Max in my 6mm Creedmoor. There is almost as much boat tail as bearing surface in the case neck at Hornady's recommended seating depth. If this doesn't work out where I like it i'll move up to the 87 - 90 grain weights. getting tired of coyotes hanging up outside of the range of my 223

 

[Jeffrey Van Zandt]

For those of you who have experienced finding a good load by adjusting seating depth what size steps did you take?

My bench rest friends take 0.003" to 0.005" steps. And Berger says you can take 0.040" steps.

for hunting I pick the bullet I want to use and barrel for that round it must fit my AI oal mag and I work from there for singl feed bench rest I work from jam back 5 tho at a time when close 2 tho

 

[Mikecr]

We can see with this thread that there is really no reason to assume a mindset starting point as best. That seating should actually be tested with a plan beginning as coarse and working toward fine.
Seating is the coarse adjustment to results, then powder is the finest adjustment.
With a good barrel, no amount of powder change will open and close grouping like seating.

So I suggest full coarse seating testing first, with no assumed setting, BEFORE moving on to powder testing. Then with best coarse seating, and best powder load, tweak seating to best shape your grouping. It's similar to fine neck tension adjustments at that point.

 

[JohnWess]

I mainly load for hunting rifles. So my criteria is that it has to hold under 1 moa out to distance (exact yardage depends on cartridge) and it has to have ES of around 20 or under. If it can do that and it has the velocity, energy, etc. It can go 1000 yards ethically by shooting about a 10" or under group. So I tend to start at a depth and work the powder charge from there. On my 300 WSM I started at .010" off and found the charge and it shoots great. The rifle shoots better than I do and it is consistent. On a 7mm-08 I did I started .070" off and that worked to. I used to think that depth was something the rifle "liked" I am now thinking that it may be a barrel shock timing thing. I don't know and I suppose I won't find out. I am not mathematically savvy enough to figure out all the variables with no constants, nor do I have the time. I just want to hunt, eat the meat, and enjoy practicing shooting to become a more proficient hunter.

 

[Mike 338]

The Berger methodology is effective. That was my starting point for seating depth tests. It works especially well with long bullets in chambers with generous freebore.

But, the Berger method doesn't work in every situation. For example, if one is working with a bullet that is too short to reach the lands, the seating depth test will have to be modified. loading bench.

Quite true. In that case, I just start at maximum magazine length and perform the test as deep as I can reasonably seat the bullet. No method is a guarantee however the Berger method will expose a bullet that performs best with a significant jump in reasonably few shots. I have as many rifles that shoot best with a .070" jump as I do with a .020" jump.

 

[Clay Target Guy]

I am a .010 man myself, and once I get to the smallest group and it starts to open back up, I go back to the setting that gives me the smallest group and then go .005 to either side and see if it gets better or worse

 

[benchracer]

Here are some examples of different seating depth tests I have done, including the Berger Method, working forward from book length with a varmint bullet, and working with a shortened test interval to preserve case capacity. As you can see, they all work. One just has to take some measurements, figure out how much space you have to work with, and decide upon your test intervals.

BTW, I am in complete agreement with Mikecr's take on testing for seating depth.

 

[brettman]

I go with the Berger method. I have a rifle that wouldn't group till it had a .225" jump. Gonn'a have a rough time finding that out in .005" increments.

Glad I'm not the only one who has been there. I've been working on a 30-06 with a kreiger barrel that didn't tighten up till I passed the .100 mark. Had me a bit worried I'd sunk 2k into a rifle that was going to stuck at 1moa accuracy. .110 was just under 1moa, .130 shrunk it below 1/2moa, .150 opened up to about 3/4.

 

[Mikecr]

Think of it this way: powder is for tuning.
Where there is a change huge to results, you're really affecting some issue. Whether bullet change, primer change, new powder, or seating.
Adjusting load, big or down to the kernel, is nothing like these things.

I believe bullet change differences(improvements/failures) are often tied to the lacking of full seating testing in followup.
Primer striking can be adjusted for optimum from a chosen primer. But who does that?
Folks just swap primers, and for no reason one will seem better than the others.
Well no primer is 'better' than the others. Not really.
Powder is magic. There is some predicting to the quality of load, but not of tune.
Might as well accept that you may need a different powder for no known reason.
Just something going on with the timing..
On seating, I believe a free bullet rattles inconsistently into throats, at run distances other than optimum. Smoother & consistent at optimum, clearing the issue.
You won't have this with ITL or jam conditions, but that's an entirely different matter from seating testing for hunting capacity cartridges. It applies well for underbore cartridges which rely on high starting pressures, with way faster powders.
BUT,, where you can test it, you never know.

Isn't this fun?

 

[ShtrRdy]

This is turning out good!

 

[ThrdKllr]

I've done seating depth test and what I presume out of my experience is that depth changes change the exact instant the bullet leaves the barrel by minutely varying the distance and velocities. Getting the bullet to exit at a time when the barrel is between upward and downward oscillation. The width of which is the width of the node. This is the reason several seating depths far apart can be as good as the other. Velocity does change when seating depth changes but very small amount. Seating deeper lowers velocity and pressure. Anyhow, that's my theory and I can't prove a word of it except the velocity drop. Start load development as close as you can or feel comfortable with and move back. I usually start at .020 off if the magazine allows and adjust in .010 and if it improves or degrades, I investigate further. My wooden nickels worth.

 

[bob4]

I've always looked at Bergers method as a rough start. And have always had one group shoot better than others. Because I hunt I start at .10 off and work back from there. Then powder charge then I'll fine tune seating. Not a bench rester but this seems to work for hunting.

 

[Muddyboots]

Since I am dealing with factory rifles or replacement stocks with AICS mags, I usually start with the MAX COAL (not ogive) for reliable magazine feed whether box etc. It makes no sense to find a really accurate round 0.010 off the lands if you can't feed anything than 0.030 off the lands due to COAL limitations UNLESS you shoot single shot. I do load to the ogive measurement to fit the magazines COAL capacity. I do have couple of 700's where the I can reach lands with 0.010 but that is from shooting heavier longer bullets with pretty much "standard" ogives. Sometimes trading the accuracy of getting closer to the lands with a "standard" bullet offsets shooting a high BC bullet that you cannot feed if loaded close to the lands. My 300WM Sendero loves the 200AB 0.010 off the lands and will feed perfectly. I tried farther and shot fine but really shouted "Right here!" when I moved to 0.010!

I have always started 0.020 off the lands since I have found my rifles will shoot pretty well starting there and then moving both directions 0.010. If nothing looks magical, then I go farther off the lands. I just replaced an 50 year old Savage 110C .270 barrel last year. that only shot worth a darn at SAAMI no matter what bullet you tried. Never could figure that one out so just loaded SAAMI specs and took what that old rifle gave me. BTW I bought that rifle new when I was 18 so for those whizbang mathematicians with a smart phone I am now 69.

New ER Shaw barrel on same old Savage loves 0.025 off with the Hornady 145 ELDX but won't load into the old box magazine so I have gone 0.050 off the lands it still shoots fine but not quite as good as 0.025.

The accuracy chase off the lands is a balancing act with feed but might be doable with standard ogive style longer heavier bullets in certain rifles.