How much of a difference can changing the seating depth of the bullet make in a group size?

Thanks

Honestly you never know. It may make a huge difference or none.
In my experience, it makes more of a difference on an inherently inaccurate rifle than an inherently accurate rifle. In other words an accurate rifle will shoot most loads well, tweaked or not, where as an inaccurate rifle will respond more to tweaking of your loads.

For the few rifles I load for, it totally depends on the amount of free bore. On a 30-06 I have, a bullet seated to approximately the same depth as a factory load is as far out as I can seat it without the bullet touching the lands. On a 7 mag I have the bullet is nearly 1/8" out passed the cannelure on the bullet. The accuracy is much better on the 7 mag with the more shallow seating depth.

Thanks guys!
I'm still working on a 7mm-08 load.

Something to consider is you can only load the projectile as far out as your magazine will allow unless you want to shoot it as a single shot.

All good points. If you have a factory chamber chances are you are not going to be able to touch the lans unless you single shot the rounds. Also, the heavier the bullet the longer the bullet gets. If you have a sami spec chamber then I would suggest trying bullets that like to be jumped such as a Sierra Game King. If you have a custom chamber then you need to find out what the reamer used to chamber your rifle was intended for. PTG produces that lions share of all reamers on the market today. I think you are a custom gun owner if I remember from earlier posts. I would ask the smith that built the rifle what the reamer was built for and usually you can play with several bullets by various manufactures in an around that weight range. Just remember that the twist in your barrel also plays a large roll in determining how the chamber was reamed. If you can reach out at touch your lans play with Bergers and Nosler accubonds. Berger has just released their first edition reloading manual and they have published data on how to efficiently find your rifles sweet spot by altering seating depths in a systematic way. Good luck. The fun of reloading is to fool with the gun until you can't ring anymore out of it. At that point you will loose interest in that rifle and you will move on to a differet rifle that needs fine tuning. Its fun, frustrating at times and can get expensive.

never seat the bullet on the lans, just back off a few thousandths, like Wiley mentioned, better check your magazine for fit, my 300WSM won't allow much runout, plenty accurate as is

my 257 Wthby in Ruger No1 has an inch of freebore, it likes the factory spec seating for overall length, it took LOTS of rounds to find the right depth for consistent day to day consistent accuracy

cartervj, seating the bullet on the lans is completely acceptable and exactly where many shooters chose to run their round. Bench rest shooters often jam the bullet into the lans. For hunting application i would not do this due to the posibilty of the bullet pulling out of the case when the shell is extracted if unfired. As long as you understand what hapens with the presure when you kiss or jam into the lans your fine. No, you dont jump out there and load to the max but starting on the low end and work up slowly. As for the weatherby the freebore is how roy achived his speed and most weatherbys need that freebore to perform. Weatherbys are a different animal and those new reloading should sick with wby specs and not alter the seating depth until they understand what happens when they do so. A low pressure ignition due to slow loads is much worse that getting a little hot and sticking a bolt. To each his own comfort level. I don't seat all my stuff on the lans but my custom guns that have reamers built for a spacific load which I work up a dummy round and send to the reamer builder all like to have bergers which I usually shoot set against the lans.

lands.......just sayin

THANKS FOR BEING A TURD WILEY. On can always count on smart a$$es on this site to chime in and coment without adding anything of value to a post.

seating against the lands is new news to me, always been taught otherwise,

my 257 Wthby with the freebore likes the factory spec, trust me I shot enough ammo to prove it, the guy I bought the gun from told me up front and I set out to prove him wrong, he won

each gun is different

my 7mm STW in Wthby AccuMark doesn't have free bore and I load it to fit in the magazine, it likes any normal depth anyways, she'll shoot half inch all day with several variables

the Ruger No1 257 Wthby as you increase length you increase group size, she'll shoot 1 inch easily til you start seating the bullet further out

Panties in a wad?

Let's air the whole thing shall we.......your PM to me

"Just saying... Did that add anything to the post? Did you know what I was talking about? Why try to start shucks guy. Last I checked this was not a learning institution and just so you know I have two degrees and am an educated person with a high paying job. I often wonder why people like you make comments like that. I doubt you are without fault."




Now, my turn.....

Sometimes correct terminology is a very good thing and I believe adds value to the post. Handloading can be very rewarding or very dangerous. ANY correct terminology on the subject adds value. cartervj also called them 'lans'. So far no I have PMs from him though. Handloading can be very rewarding or very dangerous.

Now, I have a suggestion for you.....you can go on thinking I'm an asshole and post with your feelings hurt. Or you can calm down just a bit, get a kleenex and wipe your eyes and it'll all be OK. Or you can hit the fuckkin road. I really don't give a schitt either way.

For something as serious as loading explosive ammunition, getting the terminology correct is kind of important.

We are talking about leavind the "d" off of lands. A miss spelled word that everyone on here that has commented new exactly what was being discribed. I in no way attacked anyone on here until poked at with a sharp stick for no reason. If you tight knit bucked of spilled fu*&s dont want others to comment on this site then make it your own exclussive little fraternity and pay all the bills with your own advertising to each other about who know more about jack squat. Other wise get off folks using the site.

I hope I didnt hurt anyones feelings. Here, I'll share my Kleenex.

If this -- "lands.......just sayin" -- is what you call "poked at with a sharp stick" then you should grow some thicker skin.

Reloading ammunition is serious. Whether you like it or not, getting the terminology correct is serious, or should be, and whether you like it or not, Wiley is 100 PERCENT FINE in making sure it was correctly stated.

This ain't a cooking forum where you screw up a teaspoon or tablespoon of salt and the biscuits go bad.

There might be someone new watching this forum as a guest who doesn't know something but hasn't logged in. Could be someone just getting started and, honestly, still is learning the terminology and looking for information. YOURS is not the only post(s) on here with "lans" either, so again, making the correct distinction is fine.

BTW, I counted at least 12 mistakes in your short but eloquent retort.

That is a tight-knit bucket of fu*k-ups!

I am glad I "new" what he was talking about.

I am new to reloading and I am meticulous, especially with rifle rounds. One of the first articles I ever read regarding 308 ammunition was seating depth. In the article the writer used this analogy. You can drive most any car over a curb with little difficulty if you have a running start but take that same car and place the tires against the curb and then try to drive over, you will find a lot more energy is required to do so. Same with seating depth of ammunition. If you seat the bullet so that it touches the lands you are going to create more chamber pressure it is a given, now the question is how much do you reduce a load to do this, I do not know. I have read a lot of bench rest shooters will place the bullet against the lands and one could safely do it but remember one of the most critical elements of reloading, pressure, the chamber is rated for so much pressure, exceed it and you might regret it in more ways than one.

Loading to touch the lands is perfectly acceptable. I find that most of my rifles will shoot more accurately when loaded to touch or just off the lands (.002 to .010). There are a few precautions you need to take. Start by reducing the powder charge by 5% percent from the listed maximum load in the manual and load the bullet to touch the lands. Also check to see if a round loaded to touch the lands will fit in the magazine and feed reliably to the chamber.

Finding the right recepe for a rifle is a process of eliminating the variables - bullet, type of powder, powder weight, seating depth, etc.. When trying to determine the proper adjustment for each variable, you need to keep all other variables constant. Load 3-4 rounds to touch the lands and load an additional 3-4 rounds by backing the bullet depth away from the lands by .003. Keep trying different depths to see if the accuracy is better touching or by backing off the lands. Once you have determined which seating depth is most accurate, you can then start increasing your powder charges, always checking the cases for excessive pressure signs as you increase the charge.

Also, the same bullet may have different seating depths if they are from a different manufacturing lot. This means that a 150g Hornady from lot number 12345 may not measure the same as a Hornady 150g bullet from lot 54321. This is due to wearing on the bullet dies at the plant. Each time you buy bullets from a new lot, recheck your seating depth. A good tool for this is Hornady's OAL guage which you can find at Bass Pro or order from any reloading supply retailer.