Seating depth, does it make this much difference?

[lazyeiger]

I tested out some different seating depths today with 2 different neck tensions (0.001" and 0.002") I shot five rounds of each setup.
1/ bullet long and being seated by the bolt closing
2/ just touching lands
3/ 0.005" jump
4/ 0.010" jump
5/ 0.020" jump

All at 200 yards .308 168g Berger Hybrids at ~ 2850 ft/sec

Everything was about 1 MOA except the 0.002" neck tension soft seated which was almost 5 shots in one hole (0.22 MOA with "on target")

Does seating depth and neck tension really make this much difference or was this just a fluke? Of course I will load up some more with the same specifications but I will not be able to test for at least another week!

Thanks Jon.

 

[GerryM]

Each barrel and chamber is different. That said you have to find the load that works best for your particular rifle. Some barrels like different bullet weights others arent as fussey. Some people jump some seat into the lands. Powder bullet primer combinations are the key. Your smallest group told you the story for your rifle . Load quite a few more round and ring that load Out.
I bet the score will be far better.

 

[Preacher]

You can bet it will make a difference, but as the twin mentioned they are all different in there particular wants. These were from my 6mm SLR while working up loads...
Regular depth is with the thickest base of the bullet at the base of the neck, and I work out from there.
The 105 A-max needs a bit more work, but it's coming around..
The 105 Bergers are doing good, but will keep on checking..
All are about .0015 neck tension...

 

[K22]

It depends on the rifle and bullet and load. My 308 shows a definite preference for a 2.810 overall length with Sierra 150's. If I go shorter say to 2.750, my groups open up.

I have a 223 Rem Model 7 that likes the seating dept shorter (2.260) than all my other 223's (2.285).

You just have to experiment with each rifle / load combination to find what works best. Generally however, with most rifles / loads I've found that the longer overall lengths yield the best accuracy.

 

[lynn]

Lazyeiger
I haven't found neck tension to play that much of a role in how a gun shoots unless it is the determining factor in your seating depth.That means if the gun shoots a quarter inch with 0.001 neck tension it will do it with 0.003 as well.You might need some small adjustments but it will still shoot well.

On the other hand seating depth in my opinion is the single biggest part of accuracy.
Lynn

 

[artbosco]

You can bet it will make a difference, but as the twin mentioned they are all different in there particular wants. These were from my 6mm SLR while working up loads...
Regular depth is with the thickest base of the bullet at the base of the neck, and I work out from there.
The 105 A-max needs a bit more work, but it's coming around..
The 105 Bergers are doing good, but will keep on checking..
All are about .0015 neck tension...

I see a lot of vertical in those groups. Try changing your load in .2 of a grain increments. Going from in, to out of tune, can usually be resolved within a .6 of a grain range.

Shooting over Wind Flags? If not, different conditions can easily interfere with evaluations because different changes in wind conditions can play havoc with group sizes and their resulting images on paper [even with the best of loads]. Good luck.

 

[Flouncer]

Was your shooting conducted under laboratory conditions?
Are your shooting skills at a level to tell the difference?
Are the results repeatable?
Did you fire a statistically significant number of groups?
Were the groups of similar size or were there significant outliers?



LE Hanson

Lawrence I would appreciate any comments you have regarding my thread on the 8x57 load development. Thanks
http://forum.accurateshooter.com/index.php/topic,3769264.0.html

 

[lpreddick]

seating depth...meaning the distance the bullet will travel before engaging the lands is probably the quickest way to affect the group size and location. .005 thous will often make a big difference. one big problem with these small measurements is just that...measuring. all calipers can be strongarmed a few thous and if done eratically, you can get 5 rounds with 5 different seating depths and you can't figure out why todays group is different from yesterdays. an aside, the target used by preacher...a circle. i have tried about every target made and ones i made using the sources for such. a 3 or 4 mm thick black circle with an 8 to 10 mm white center on white paper is for me the easiest to see in all conditions and certainly the easiest to see bullet holes even when they hit the circle. i've colored the center with about every color only to find that white is easiest to see. large scope reticles may require larger circles as may lower power scopes. [/quote] if i can see you, i can touch you. BANG!

 

[SShooterZ]

Let me ask this question.

Do you determine a good load via laddering them and then start playing with seating depth? Or vice versa?

I typically go .020 off the lands and have had some nice shooters. (Nothing benchrest quality) and was wondering if I should start tinkering with depth. Also, do you ladder in .050 increments to find the honey load?

 

[bozo699]

Let me ask this question.

Do you determine a good load via laddering them and then start playing with seating depth? Or vice versa?

I typically go .020 off the lands and have had some nice shooters. (Nothing benchrest quality) and was wondering if I should start tinkering with depth. Also, do you ladder in .050 increments to find the honey load?

SShooterZ,
I would go .005 at the most, I usually go .002-.003 at a whack, .050 is a lot.
Wayne.

 

[lpreddick]

the quickest way for me to find an accurate load is to pick a powder suited for the cartridge and bullet weight. load a charge that is safe and gives an optimal velocity. load three cases 5 thous off lands, three cases 10 thous off lands, three more 15 thous off, and continue loading out to 30 to 45 thous off. shoot the ones closest to the lands first. at some point you will find a tight group and often see the group open up as you continue...this is really neat to see. i repeat the tighest group at least twice more to be sure its real. if i can't find something i like, i will change powders and charge and often find what i was looking for. [/quote] if i can see you, i can touch you. BANG!

 

[GrocMax]

If you get a much larger statistical sample of each you'll be able to see the trends a bit better, say 10 rds of each in round robin. 3 or 5 shot consecutively shot stats can lead to tail-chasing in some cases.

One thing I discovered recently is barrel heat vs seating depth = group consistency. I shoot PD's, not bench or low round count disciplines, as barrel heat climbs and velocity climbs with it, the optimal seating depth for a cold 5 shot group is NOT the same as one for say 20-30 rds in 10 minutes with a finish avg velocity of the last 3 shots 100+ FPS over starting avg velocity of the first three.

I guess its best to test things under the same conditions as your particular shooting discipline requires.

 

[BoydAllen]

Going back to the original question....yes it can. IMO once a reasonable powder charge has been determined, by test, there is much more to be gained by working with seating depth than by fiddling with small changes in powder charge. Knowing this, I am sometimes amused by the common preoccupation on very small increments of charge weight, particularly when testing at 100 yd.