Seating Depth Frustration

U

USAF Ret

New member
So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting. So, objective is
2.8
2.797
2.794
2.791

However, I will get one cartridge measured and will get a couple that will be anywhere from .002 to .003 off. I took this that there might be a little tip deformation. So, I broke out the comparator to double check measurement from the ogive and I am also getting some cartridges with up to .003 difference with the seating die not moving. With a difference of up to .003 and me trying to seat a .003 difference, makes me wonder if I just wasted a bunch of time.

Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped. Maybe the quality of the bullets?
 
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I could be wrong, but 0.003” could be too high a precision for normal handloader's setup. At least I don't trust myself to do that. A few data points for consideration.

The cartridge probably has 3” in total length. 0.003” out of 3” is 0.1%. Even carefully designed electronic circuits would have difficulty meeting that tolerance.

A caliper easily has tolerance of +/-0.001" even in trained hands. +/-0.002" is not unheard of.

In CNC machining, tolerance of 0.005" comes with no extra cost. We have to pay more if we need 0.002" or tighter.

Thickness of printer paper is 0.004".

What do I do in search for best seating depth? I do step of 0.012" or 0.025" and accept tolerance of +/-0.005". One turn on the seating stem is 0.05".

-TL



Sent from my SM-N960U using Tapatalk
 
tangolima said:
I could be wrong, but 0.003” could be too high a precision for normal handloader's setup. At least I don't trust myself to do that. A few data points for consideration.

The cartridge probably has 3” in total length. 0.003” out of 3” is 0.1%. Even carefully designed electronic circuits would have difficulty meeting that tolerance.

A caliper easily has tolerance of +/-0.001" even in trained hands. +/-0.002" is not unheard of.

In CNC machining, tolerance of 0.005" comes with no extra cost. We have to pay more if we need 0.002" or tighter.

Thickness of printer paper is 0.004".

What do I do in search for best seating depth? I do step of 0.012" or 0.025" and accept tolerance of +/-0.005". One turn on the seating stem is 0.05".

-TL



Sent from my SM-N960U using Tapatalk
Click to expand...
With that input should I open the gaps in seating depth from .003 to maybe .010 or .0015?

Also, I am not a precision shooter looking for 1/3" MOA. I am a hunter. If I a, getting 1" I am happy.
 
And there is my answer. I hate wasting components, but I reckon that is the cost of learning.

bergerbullets.com

Load 24 rounds at the following Cartridge Base to Ogive lengths.

.015″ off the lands (jump) 6 rounds
.030″ off the lands (jump) 6 rounds
.045″ off the lands (jump) 6 rounds
.060″ off the lands (jump) 6 rounds
 
Consider your die seating stem rests somewhere on the ogive. your calipers are measuring over the bullet tip.
You are working with variables expecting no variation.

I know the benchrest folks find steps of accuracy improvement by tuning seating depth to the lands.

I'll never forget the time I saw one of these guys seating bullets at the range,firing 3 or five rounds,measuring spread on the target with calipers,turning colors like red and purple,and screaming at his wife.

It did not look like anyone was having any fun.

What is the "Mission Statement"? Have you tried measuring the base to tip length of the bullets? Have you looked at Sinclair's "Meplat Uniformer"? I do not have one.

I had a Douglas Barreled 36 cal muzzle loader I built that frustrated me! With iron sights ,and round balls I cast, some striped pillow ticking and 3fg, I only hit the target once at 50 yds for 3 shots fired. Till I noticed the balls left one egg shaped hole. Black powder,lead,and a rag.

With all due respect to the benchresters and all they have done for us,the OCD stuff can be a disease.

When making a change and observing results, beware expectations. Anger,frustration are often sourced from unmet expectations. There is a lesson there someplace.

You can use .003 increments. What if you try 1/4 turn on the stem? Don't even measure them. Go max to min in 3 or 4 steps. OK. Maybe two quarter turns shows promise. Fine. Try + and - 1/8 turn. Its like bracketing artillery fire. Correct by 1/2 each time. When the results are as good as they are going to get on target,THEN get your calipers out and record the number to repeat.

Keep it fun.
 
USAF,

Your Variation is exactly what I get when I measure my 168 SMKs using a comparator. Remember your measurements are only going to be as precise as your measuring device.

The only way I got about 90% of all the bullets was sorting them by base to ogive

so if one measured .622 the other .623, I would sort each one by the the lenght I measured . But after awhile It got extremely tedious because I would go back and remeasure them amd some would still be off .001 because the error was me and the comparator.

So I started sorting by .001 difference and it was alot easier to sort. I also got to the conclusion that my skill as a handloader needed to be trumped by being a better shooter.

I needed to learn to shoot better, not reload better.


You wont notice that .001

Another trick you can try is to back off your competition seating die .005 then seat bullet, measure, then adjust to your seating dept using the comparator and not the tip. you will see more consistent seating depts because your seating stem is machined way better than the comparator.

Some may argue this may affect neck tension because some projectiles are seated alittle bit deeper than others but again its around .001 diff so its marginal
 
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HiBC said:
Consider your die seating stem rests somewhere on the ogive. your calipers are measuring over the bullet tip.
You are working with variables expecting no variation.

I know the benchrest folks find steps of accuracy improvement by tuning seating depth to the lands.

I'll never forget the time I saw one of these guys seating bullets at the range,firing 3 or five rounds,measuring spread on the target with calipers,turning colors like red and purple,and screaming at his wife.

It did not look like anyone was having any fun.

What is the "Mission Statement"? Have you tried measuring the base to tip length of the bullets? Have you looked at Sinclair's "Meplat Uniformer"? I do not have one.

I had a Douglas Barreled 36 cal muzzle loader I built that frustrated me! With iron sights ,and round balls I cast, some striped pillow ticking and 3fg, I only hit the target once at 50 yds for 3 shots fired. Till I noticed the balls left one egg shaped hole. Black powder,lead,and a rag.

With all due respect to the benchresters and all they have done for us,the OCD stuff can be a disease.

When making a change and observing results, beware expectations. Anger,frustration are often sourced from unmet expectations. There is a lesson there someplace.

You can use .003 increments. What if you try 1/4 turn on the stem? Don't even measure them. Go max to min in 3 or 4 steps. OK. Maybe two quarter turns shows promise. Fine. Try + and - 1/8 turn. Its like bracketing artillery fire. Correct by 1/2 each time. When the results are as good as they are going to get on target,THEN get your calipers out and record the number to repeat.

Keep it fun.
Click to expand...
I like your approach. Measure what I am backing out vs. getting anal about length.

I am not OCD about this stuff. I have other things that keep me up at night. This is my therapy, so I don't get too worked up. I just don't want to be wasting expensive components and get a good hunting load worked up and just build out several boxes and move to the next rifle.

These target bullets are for a buddy shooting an AR-10. He shoots for fun and had heard good results out of these bullets. So, I got some samples and loaded some with the same weight charge and different depths. He is not a precision shooter and just said he would like to find an accurate load and have me build out some ammo for him.
 
akinswi said:
USAF,

Your Variation is exactly what I get when I measure my 168 SMKs using a comparator. Remember your measurements are only going to be as precise as your measuring device.

The only way I got about 90% of all the bullets was sorting them by base to ogive

so if one measured .622 the other .623, I would sort each one by the the lenght I measured . But after awhile It got extremely tedious because I would go back and remeasure them amd some would still be off .001 because the error was me and the comparator.

So I started sorting by .001 difference and it was alot easier to sort. I also got to the conclusion that my skill as a handloader needed to be trumped by being a better shooter.

I needed to learn to shoot better, not reload better.


You wont notice that .001

Another trick you can try is to back off your competition seating die .005 then seat bullet, measure, then adjust to your seating dept using the comparator and not the tip. you will see more consistent seating depts because your seating stem is machined way better than the comparator.

Some may argue this may affect neck tension because some projectiles are seated alittle bit deeper than others but again its around .001 diff so its marginal
Click to expand...
I started doing exactly that on the 175s. On the 165s I was measuring tip. On the 175s I used the comparator to measure ogive. I noted the ogive measurements for all the loads, so if we find one for my buddy that works, I can reload a little more accurately.

I am learning as I go. Will use this knowledge on the next round.
 
In an AR-10 T we have had very good results with 168 gr MKs and Varget. Charge weight a bit under max.

I'm pretty sure if you load to magazine length you won't jam into the rifling.
 
HiBC said:
In an AR-10 T we have had very good results with 168 gr MKs and Varget. Charge weight a bit under max.

I'm pretty sure if you load to magazine length you won't jam into the rifling.
Click to expand...
Appreciate it. These loads are with Benchmark. If they don;t pan out for my buddy, we will go with Varget next. I am going to have to have him get me a couple of pounds of powder here soon, though.
 
USAF Ret said:
Am I doing something wrong? Bullets are 168 and 175 Match King. Non-tipped. Maybe the quality of the bullets?
Click to expand...

akinswi has your answer, but

one of the issues here could be related to where the seating plug touches the bullet.
Bullets tend to be somewhat less consistent near the tip, although I would not think Match Kings would suffer from this so much, I don't use them so I can't say.

One way to check for the seating consistency would be to remove the seating plug from the die and measure the OAL variance with the plug, versus at the ogive.

In other words, if you measure a bunch of rounds at the ogive and you get a variance of 0.003 but the OAL with the plug varies by 0.001, you'd know that the plug/die was being consistent, but the bullet tips were not.

The solution would be to drill out the seater plug so it touches closer to the ogive, or get a die that does that by design.

However, 002 or 3 is pretty damn precise and not something I would worry about. As others have mentioned, I'm not sure it gets much better without some serious equipment (and for no discernible benefit). For hunting ammo, you could probably have 5 (I might even venture 10) times that spread and never know the difference.
 
Hey Brian!



The best general tool for this kind of measurement is a granite surface plate and a height gauge. You can set the bullet on the plate and the seater ram on the bullet and measure the hight of the seater ram with good consistency.

Powder: Most 308 match loads use Varget, IMR4064, or IMR4895 traditionally. Benchmark loads hitting the same peak pressure are charged about 10% lighter and produce about 100 fps less velocity, so Benchmark is on the fast side for the application. Closer to IMR3031 in charge weight but produces even less velocity, as 3031 loads are between Benchmark and the others on velocity.
 
Here's an off the wall thought, take those rounds you loaded and carefully shoot them and see what they do, and IF there is any significant difference.

IF you're loading for hunting, shoot from FIELD POSITIONS. All the tiny match winning tricks don't put venison in your freezer, YOU DO, or you don't.

If your game is smallest groups possible, use the tricks, tips and everything possible to get there. If the point is shooting game in the field, few, if any of those same things will matter. Not to the game, and probably not to a hunting rifle.
 
44 AMP said:
Here's an off the wall thought, take those rounds you loaded and carefully shoot them and see what they do, and IF there is any significant difference.

IF you're loading for hunting, shoot from FIELD POSITIONS. All the tiny match winning tricks don't put venison in your freezer, YOU DO, or you don't.

If your game is smallest groups possible, use the tricks, tips and everything possible to get there. If the point is shooting game in the field, few, if any of those same things will matter. Not to the game, and probably not to a hunting rifle.
Click to expand...
These are for a buddies AR-10. He is coming down tomorrow and we are taking a long weekend. He will be group testing them so I have the data. I think id groups are sluggish, I may switch to Varget. He just shoots for fun and had heard the 168 and 175 Matchkings are good. I ordered some samples and told him I would roll him a few. We shall see.
 
Cant go wrong with Varget it so versatile across the 30 cal board.

44amp is correct practice as much as you can not using a rest. Took me years to realize in a real world situation you cant setup your Bench rest at moments notice :D:D

Happy shooting
 
akinswi said:
Cant go wrong with Varget it so versatile across the 30 cal board.

44amp is correct practice as much as you can not using a rest. Took me years to realize in a real world situation you cant setup your Bench rest at moments notice :D:D

Happy shooting
Click to expand...
I think that is a good idea for practicing. Definitely.
 
USAF, clarify your initial sentence: "So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting."

If you are starting with a manual recommendation of a cartridge overall length from the bullet tip to the base of the case, and then seating deeper by any increment, I would think you are really wasting supplies. As AMP44 so often has said, the recommendation in the manual does not apply to your rifle. It is a safe COAL for ANY rifle and has nothing to do with accuracy in any rifle other than the one the manufacturer is testing. And you certainly can't take a tip-to-base round and seat the bullet several thousands or so deeper then measure the base-to-ogive. You first must establish where THAT bullet touches your rifling in your rifle.

As an aside, for example, if I am seating a 160gr Sierra bullet in my 7mm Rem Mag so it is exactly 0.0150 " off the rifling, and the first round that I seat hits that mark, I cannot be certain that every round that follows will be as exact. There may be some resistance to seating based on neck thickness caused by extensive reloading of a particular case, or even worse if you are using mixed brass. But very often, as an example, I have found differences when using the comparator (which I always do) will give me a round that is the desired 2.215" and the next one is 2.217 or 2.218. I have learned to put that round on the flat surface of the table to see if it rock-and-rolls. If so, the primer was not seated deeply enough, and I gently run it through the seating process to give it just a nudge, then measure, and, sure enough - the round is 2.215. Now maybe the primer pocket should have been cleaned.
 
Brother loaded up some 5.56 varmint loads. We wanted an expanding bullet. There is a Nosler Varmint Ballistic Tip of approx 60+ grains.
Benchmark (being a step faster than Varget) gave excellent accuracy and velocity.
FWIW, For 5.56 ,with 1 on 9 twist 16 in bbl, Varget is my go-to for 69 gr bullets.

Point,you have good,useful powder in Benchmark. IMO, its a step "quick" for the 308 168 gr.

---------------------------------------------------------------------------------

a thought just occured to me,and it piggy backs on what cdoc said above

You are wanting to not waste time and components .

I get it you are trying to do a good,meticulous job for your buddy. And you are learning.

This seating depth thing ordinarily begins by establishing the LOA where the bullet contacts the rifling. That is the start point. Then our handloader might incrementally seat deeper to find as ideal distance off the lands for that rifle.
The "Jump"

We (maybe) skipped the step of finding the lands. Thats OK. With the AR-10, you have a magazine length. 2.800 is book max loa because it works through the magazine. Its got nothing to do with contacting the rifling.

I'd bet,at 2.800, the ogive of the 168 gr MK is already an appropriate distance off the lands. Thats an assumption on my part,it won't hurt to verify. But I'm pretty confident.

If you want to save components, I suggest you just load to 2.800 and go shooting.
 
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cdoc42 said:
USAF, clarify your initial sentence: "So, I am setting up some loads for a 308. I am starting with recommended COL of 2.8 and seating .003 back for 4 different loads for accuracy resting."

If you are starting with a manual recommendation of a cartridge overall length from the bullet tip to the base of the case, and then seating deeper by any increment, I would think you are really wasting supplies. As AMP44 so often has said, the recommendation in the manual does not apply to your rifle. It is a safe COAL for ANY rifle and has nothing to do with accuracy in any rifle other than the one the manufacturer is testing. And you certainly can't take a tip-to-base round and seat the bullet several thousands or so deeper then measure the base-to-ogive. You first must establish where THAT bullet touches your rifling in your rifle.

As an aside, for example, if I am seating a 160gr Sierra bullet in my 7mm Rem Mag so it is exactly 0.0150 " off the rifling, and the first round that I seat hits that mark, I cannot be certain that every round that follows will be as exact. There may be some resistance to seating based on neck thickness caused by extensive reloading of a particular case, or even worse if you are using mixed brass. But very often, as an example, I have found differences when using the comparator (which I always do) will give me a round that is the desired 2.215" and the next one is 2.217 or 2.218. I have learned to put that round on the flat surface of the table to see if it rock-and-rolls. If so, the primer was not seated deeply enough, and I gently run it through the seating process to give it just a nudge, then measure, and, sure enough - the round is 2.215. Now maybe the primer pocket should have been cleaned.
Click to expand...
I have a chamber gauge I use on my rifles. Unfortunately this is a buddy I am loading for his AR-10 and I don't know his chamber length nor magazine length.

The one thing I am finding out is the reason I am getting the variance is the SMKs ogive is not exactly consistent.

Results today will tell the tale. I am learning a lot to do with my own rifles, though.
 
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