how do you determine seating depth

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ungerstruck

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Hi everyone I would like to hear from an accomplished shooter someone that really knows about reloading and how to determine bullet seating depth. I know how to measure the cartridge base to Ogive. I use a hornady length gauge and a bullet comparator on a caliper to measure my chamber then seat bullets 0.01"-0.015" off lands and grooves.

But that 0.01"-0.015" is just what hornady recommends, I'v herd people talk about finding the rifles sweet spot for seating depth.

So is there some tell like a chronograph or something else that can be used to find the proper seating depth since I don't have a chronograph....yet.

Ohh and this is for accuracy not necessarily higher FPS, also I'm not worried about COAL being to long I shoot a rem 700 sendero in a 7mm rem mag it's a top load with more than enough room.
 
I load a lot of 7mm RM, 700 also. As well, I load for multiple other bottle necks, and the way I do it is as follows:

I don't use a comparator, but instead I seat up to the lands, or at zero .000". I shoot that oal, and if it doesn't produce at least 1/2" groups at 100 yds., I drop back .005" or .010", and so on. I load for some rifles that actually like em jammed though. This is a style of seating that requires one to do the powder work up at the closest proximity to the lands, this is to avoid high pressure situations.

Others work it differently, but this has worked for me for about 30 years.

GS
 
You're already adjusting your cartridge length from the base to the ogive to give yourself a "bullet jump" of .01"-.015". Sounds like you're doing that right.

I'm sorry to say that the only way to tell if it is the "right" distance is to shoot - a lot! I went through the same exercise with numerous rifles. I loaded 5 rounds at one setting and then altered the length to give me .005" more or less depending on how I was working with that particular rifle. Eventually you find a seating depth that a particular rifle likes the best.

Everyone told me to try touching the lands with the bullet... I had awful luck with that. Not one of my rifles liked that. My groups improved as I seated the bullets deeper, to give me a "bullet jump" of .030" (thirty thousandths) off the lands and then I didn't get any improvements. Depending on the rifle, I settled on .020" to .030" off the lands. It surprised me, but that's the way it worked out. ( everything from .22-250 up to .30-'06)

Remember though... it's not just the seating depth. There are all the other variables to throw in, that change everything - bullet type, weight, powder type and charge; you name it. That's what makes hand loading part science, part art, part luck and probably part voodoo. :)
 
Everyone has their own way of figuring it out, and pretty much all involves testing, which means shooting A LOT.

My mentor taught me to start around the .02" mark. I've always found a good load being .02" off the lands but it was a matter of testing and testing different powder charges and bullets to find what my rifle likes.
 
Ya, I failed to mention the "shooting a lot" part. With a new to me rig, it has often taken me any where from 20 - 100 rounds to dial the load in. There really isn't any short cuts, per say.

I used to jump around in .020" increments, often starting off the lands .020" - .030", then adjusting either longer, or shorter with no real clue which direction would improve accuracy, and burning through components like crazy. That was what inspired me to,start with the longest oal first, and work down from there.

But one could just as well come up with a shortest number to start with, then close the distance in small increments until the sweet spot is identified. The only issue I have with this approach, is pressure spikes with an already worked up load. This is a concern that doesn't present when the charge is worked up at the lands. Other wise, one is often forced to re-work the charge as they approach the lands to avoid pressure spikes. More time, more components, and possible over pressure issues.

GS
 
What method do you you rifle guys use to determine the distance to the lands?

I know there are gauges and go no go tools and some mark the bullet (smoke it) or what ever and load it long then push it into the lands Another of using a rod and marking it then measure it but I can't remember.

What's the best, no special tool needed way, that you use?
 
I seat a bullet long, mark it with a sharpie, and chamber it. Adjust the die until you just do not see rifling marks on the bullet. This may take ten bullets marked and tested. This will give you a zero to start. I would start at -.020 and adjust after you find a powder charge that it likes. Then adjust the seater in small increments. Shoot a lot of groups, this will do two things for you.
1. You will eliminate shooter error from your testing, and
2. You will become a better shot from all the practice eliminating shooter error.
 
I'm not sure what you mean by accomplished shooter but I like 1/2 MOA's ;)

I do like you and measure distance to the lands. I start at about .20 off and find my powder charge that groups well. Then I bump the ogive this way and that to see if I can tighten it up. When I'm under 1" MOA I'm happy.
If I was all about accuracy after I tweaked the powder then the ogive I might try moving my powder charge +/- .2 grns again. Don't think there's a fast way to do this. Just requires time and shooting.

I've heard about people doing it just the opposite. Take a certain charge and tweak the Ogive anf tighten groups then adjust the powder charge. Never tried this myself.
 
There is no short cut when it comes to this. You just have to find what your gun likes. My old 7mm RM likes ~0.025" off the lands. When I started doing this 4 decades ago I started with published data and worked from there. Find the sweet spot with the charge then start changing the OAL. Since this guns kicks harder than a mule it does take some trigger time to get comfortable with it. You have to do your part before you can determine weather it's the ammo or the gunner. And if you change any components it requires you to retest. Some times just a new lot of bullets will change the sweet spot. Brass changes too as you use it so it comes into play. This is one for the enjoyments of reloading.
 
Rule3 said:
What method do you you rifle guys use to determine the distance to the lands?

I know there are gauges and go no go tools and some mark the bullet (smoke it) or what ever and load it long then push it into the lands Another of using a rod and marking it then measure it but I can't remember.

What's the best, no special tool needed way, that you use?
Click to expand...

I'm by no means an expert reloader or accomplished shooter, but I do get a little OCD about reloading at times, just because I can. Here's what I do with my bolt rifles, for better or worse. My "no special tools" exercise is to seat a bullet in a "dummy" case and push it into the chamber with my finger. If it sticks, that is, if gravity won't make it fall out, I poke it out with a dowel rod through the muzzle and I seat it a little deeper. Rinse and repeat until it doesn't stick in the lands. Then I do it again to make sure it's consistent. If so, that becomes my sample cartridge for Max OAL without touching the lands for that particular brand and model of bullet, minus a couple of thou to allow for variation in bullet length. That's without special tools and relies on consistent head to shoulder dimension to give a consistent OAL to lands.

Now, when I really get OCD bound, I break out the tools. I take my sample cartridge from above and measure the head to shoulder distance with a Hornady headspace comparator, then zero the calipers and measure from head to ogive with a Hornady bullet comparator. That gives me Max shoulder to ogive distance for any cartridge OAL for that bullet in that rifle. So, whether I just bump the shoulder back a couple of thousandths or FL resize the brass, I know how deep to seat the bullet for a specific jump to lands. I just wish I could shoot well enough to justify doing all that. Until I can, I'll keep doing it just because it's fun. ;)
 
Hi guys thanks for the input but now I've got another question for people that develop accurate loads with a chronograph.

So like I said I don't have a chronograph yet but if you either load powder charge then play with depth or vise versa do you guys notice it on your (ES or (SD).

How I understand it if I had a chronograph I would

1. load one depth and go from minimum to maximum powder charge by either 0.5-0.3gr increments till I found the lowest (ES) and/or (SD).

2. Then change seating depth till again hit the lowest (ES) and/or (SD) values.

3. Repeat steps 1 and 2 in smaller increments.
 
Don't get caught up in the numbers. There are plenty of loads out there with large ES <100 that will produce 1 ragged hole. It all depends on the powder/bullet combo. Beside the numbers mean nothing if you are not getting the groups.
 
I could be very wrong but I thought the lower the fps spread the tighter group if we do our part is this wrong?

Like I said I don't have a chronograph so I'm just basing this off of what I've read.
 
Like Blue said... don't get caught up in the numbers. I have a chronograph and it's a lot of fun to play with. I've found some batches of loads to have very low SD that aren't nearly as accurate as other loads that are so varied that it astounds me they group at all! It's all kind of magic... everything has to work right and the stars have to align somehow. I know that sounds weird. There are just so many variables to contend with. Very generally speaking, what you're saying is true - the tighter the numbers, the more consistent the loads, the better the groups SHOULD be. :)

I do use the chronograph to tell me how consistent I am at the loading bench. Lower standard deviations can show you that you're being more careful and consistent with your loading practices.
 
I seem to get best results when I keep the necks loose enough (not finger loose) so that all of the bullets will be pushed back when they're chambered, and load .005" - .008" over or thereabouts. I don't use a lot of neck tension and I don't load any longer than necessary. Bullet length varies from batch to batch and adjusting the seating die is a hassle, so I don't try to load a certain distance into the lands anymore, I just make sure the necks are fairly loose and OAL is a minimum of .005" over on my shortest rounds.
 
I was thinking of getting a chronograph but now I have to ask.

Would it help me get better groups using one to bring my es values down then practicing or is it a waste of time and money getting one?

Maybe I have to high expectations of my stock rifle or I could vary well be a bad shot I sure hope not.
 
It's not a must to get a chronograph, but it is very nice to have one. I take mine to the range each and every time I go. I like to see how that lot will perform.

They're also nice to have to help get your dope for mid-range or long range shooting.
 
ungerstruck said:
Would it help me get better groups using one to bring my es values down then practicing or is it a waste of time and money getting one?
Click to expand...

A chronograph can be had for just over a hundred dollars and in my opinion it is well worth it. In my case I've had instances where higher charges have actually caused a lower velocity as a result of plugging and friction, but because the bullets still landed higher on the target I would never have known what was happening without the chronograph, This is why I so value, and recommend, this piece of equipment.
 
ungerstruck said:
I was thinking of getting a chronograph but now I have to ask.

Would it help me get better groups using one to bring my es values down then practicing or is it a waste of time and money getting one?

Maybe I have to high expectations of my stock rifle or I could vary well be a bad shot I sure hope not.
Click to expand...
I didn't have one for my first 2 yrs and was still getting great groups with my rifle. As others have already said. Not necessary.
 
okay thanks guys so what you guys said is that a chronograph is not needed but helpful especially for watching out for plugging, friction and your dope.

thanks.
 
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