Close to lands VS Long jump?

[roysclockgun]

Where was I when the theory changed from getting bullets close to the lands, to seating deeper to give some more jump to the lands?
For years I read that the way to get optimum accuracy, was to seat the bullets very close to the lands and work back until the "sweet" spot was discovered. For years, I worked back but not far, before I found that bullets seated close to the lands printed the best groups.
I even had a .270Win. on a Mauser action that shot so well with the bullets way out there, that used it for hunting as a single shot, because the long cartridges would not feed through the mag!
More recently, enter the 7mm-08, for which I began hand loading and was told here, on this forum, to start seating deeper than even my loading manual suggested. Upon experimenting, the suggestion of creating more "jump" to the lands proved to be correct! My best groups have been with a deeper seated 120gr. bullet.
Has this truth always been there and I simply missed it, or has there been a change in the beliefs regarding how far back to seat bullets?
Steven in DeLand, FL

 

[338winmag]

In another post I mentioned that my new 7mm-08 magazine box will only allow 2.800 max C.O.L.. After measuring for my lands I find that I start at .090 off the lands with a 2.800 C.O.L. round. I will be goingout to the range to break in the rifle in a couplde of weeks.

How far off the lands with the 120 gr are you at for your sweet spot?
What 120 gr bullet and what powder are you using?

Thanks
Steve

 

[DrMike]

Steven,

Allowing a long jump to the lands is counter intuitive. Consequently, for years people resisted trying such a thing. With the introduction of monolithic bullets and their acceptance by the shooting public, it was necessary to advise loading with a longer jump to the lands to avoid pressure problems. As people began to load, they discovered that with these bullets there were at least two nodes at which barrel harmonics yielded the greatest accuracy. The light went on for many people. If monolithics benefitted from a long jump to the lands, was it possible that cup and core bullets could also benefit from such a jump. In short, it shortly became evident that there exists multiple nodes for the greatest accuracy. After the fact, many people acknowledge that Weatherby rifles with their exaggerated freebore and many Remington cartridges with similar excessive freebore, provided more than average accuracy. Obviously, there exists a second node at least.

 

[rick smith]

If you load for many short actions, you will find seating to mag length or shorter is very common. I think all the WBY Mags I have loaded for have throats so long that the bullet is out of the case before I reached the lands. Those I seat the bullet so the base is even with the shoulder and load from there. Loading concentric rounds is very important, more so in the long throated chambers. No magic being close to the lands just a place to start with bullet seating.Rick.

 

[BeeTee]

Precision bullet seaters all have a sleeve that precisely aligns the bullet as it enters the case. The freebore used by Wby is sorta like that - the lands simply begin a ways up the bore, but the bullet is fully supported/aligned by the bore. Theoretically, the bullet can't begin its journey out of alignment with the bore (+/- manufacturing tolerance).

Most other commercial rifles employ a simple ramp some distance ahead of where the case ends, where the lands and grooves begin. Seating the bullet out to where it contacts the lands helps to center the bullet in the bore of a commercially manufactured rifle (that probably has more tolerance than a custom barrel or the barrel in a premium rifle). Jim

 

[Ridge_Runner]

your rifle will shoot best at "x" velocity, this will be in the accuracy node. seating to the lands takes more powder and pushes more pressure to hit "x" velocity. take your loads seated to the lands and shoot them over a chrony, then seat one .030" off with the same load, shoot it through the chrony, check the results.
even with a short jump, the bullet will stop on the lands till pressure builds enough to shove it on through, alot of times pressure peaks before it gets into the rifleing, a bullet thats moving as it hits the lands will make the transition with less resistance and use the quickly building pressure to make more velocity.
My 6.5 gibbs will run 3180's with 61 gr of re-22, ruins the cases every shot, seated to the lands, at .030" off will knock on the door of 3350 with the same load, cases will last 5 rounds. and will shoot like this, 3 shots at 752 yards, not an average group by no means but they were .030" off.

RR

 

[Win_94]

I usually seat my bullets to near what the book says, or right on the edge of the cannelure. In special cartridge, like when I use the 168gr A-max in my 30-30, (loaded directly into the chamber,) I'll seat them at the lands for accuracy.

If I load the 168gr A-Max in my 30-06s, I simply seat them near to what the book says. Instead of the 3.24 COL suggested, I'll seat them for a 3.25 COL, just to make it easy. I only use the A-max in my iron sighted 30-06s so sub-moa is all I really can count on anyway, but I've gotten sub .5moa.

 

[roysclockgun]

When began this thread, I did not expect such well informed and educational answers! Thanks to all! I shall continue to experiment with the longer jumps!
Steven in DeLand

 

[roysclockgun]

To answer "338winmag" questions:

Reiterating; I am loading for my wife, who is short. I bought her a Howa 1500 with the Hogue, youth stock, which seems to fit her well. She is not complaining at all, regarding recoil and in fact says that the 7mm-08 is producing less felt recoil than her Handi-Rifle in .243Win.

I wanted a load for deer and antelope, for shots taken no more than 200 yards.

Testing the chamber length using long loaded bullets coated with fiber tipped pen, I found that the cartridge will load without touching the lands, at 2.866".

The OAL that I am using is 2.773" to 2.783"

I am shooting Sierra Pro-Hunter 120gr. SP bullet

I am loading 41.5 grains of IMR4064

Off the bench, I am getting groups in the 1 1/2" range. I am shooting a cool barrel that is light weight and 20" in length. With a 41 gr. load, I was getting 2700fps MV. The extra 1/2 gr. will raise that slightly. I need to recheck, using the Chrony.

I have Nosler 120gr. BT for the fall hunt and will load for that later.

Suggestions?
Steven in DeLand

 

[SJB358]

I could really care less about where I am in the lands. Unless it is the ET, and I still haven't really worked with them a whole lot just yet.

More than often, it seems I am a pretty good jump off the lands due to mag length, and I can't find many reasons to want to get closer. I am sure match kinda rifles and other LR deals benefit alot more from this, but with mine, if I can get .020" to the lands, I will to start, if I can't, I start at the mag length and work backwards. Altering the powder charge a little seems to assist with groups as well.

 

[1Shot]

I found by accident one time that you can get bug hole accuracy by loading way off the lands. I had been loading a 25-06 close to the lands. I was in kind of a hurry when loading up some more ammo for the rifle for my up coming deer hunting trip. I had forgotten that in the summer I had loaded up some 87 gr Sierra bullets to try a varmint load. I did not remember to reset my seating die to the correct length I had been loading my 117 gr Sierra deer bullets. I loaded up and seated 40 rounds of ammo and when I went to put them into my 50 round box that I still had a few rounds loaded to the close to the lands rounds I noticed that the bullet was much shorter. :shock: :x :idea: go to the range and see how the short seated bullets shoot. They were about 30 thousands off the lands and the others were 10 thousands off. Long story short the deeper seated bullets shot the best. From then on I do a ladder test with all my rifles. I start at 10 thousands off the lands and move back 10 thousands at a time until I find the most accurate load then I will load some 5 thousands longer and shorter to see if that improves things. I found that Berger VLD bullets will shoot waaaaaaaaay off the lands even before Berger started recommending it. I have a 30X47 HBR caliber rifle, 300 Savage case shortened by 10 thousand in the shoulder but left the same OAL. I wanted to try some Berger 155 gr VLD bullets and use them for deer hunting. I wanted them to be able to be used through the magazine of this Hunter Bench Rest rifle. I loaded them to the magazine length but with the loooooog sharp nose of that bullet it put the ogive waaaay off the lands. They shot bug holes. You live long enough you will realize that you can learn something new every day if you have an open mind. :mrgreen:

 

[woods]

Here is a seating depth test where I started at .015" off and varied by .015". I'm not posting it to show excellent groups (which I have subsequently gotten with this load) but to draw your attention to:

[*]Progressive decrease in velocity with deeper seating
[*]Progressive decrease in Extreme Spread until .060" and then progressive increase afterwards
[*]Progressive decrease in Standard Deviation until .060" and then progressive increase afterwards
[*]If going by group size only then .030" could have been chosen as easily as .060" off

IMO when you are varying seating depth you are timing bullet exit from muzzle by varying velocity and if you pick a load with the lowest ES and SD then you will have a more consistant load. This will vary from load to load.

IME when you get closer than .010" to the lands then you stand a better chance of getting flyers. The old axiom is "If you are getting flyers move away from the lands and if you have a larger than wanted groups size with no flyers, move towards the lands". But with reloading and rifles there are are always exceptions to the rule so YMMV

 

[bullet]

Does Bullet Seating Dept Increase or Decrease pressure? by Mike Price

This is an important question and here is my take on the question when one considers that seating bullets on the lands will increase pressure and seating them off the lands will decrease pressure up to a certain point then when to far from lands the pressures will start back up again. More often than not the problem most run into is not when seating a bullet too deep where pressures start coming back up, but when seating the bullet on or just off the lands causing increased pressures. This will happen because handloaders sometimes don’t back off their standard or near book max powder charges and work back up making sure there is not an over pressure issue.

Pressures will increase when bullets are seated against the lands as opposed to giving them a small or reasonable jump. What a lot of people don't understand is that when a bullet is given a jump or is seated against the lands and enters the bore it actually PAUSES for a very brief moment. At that point the pressure increases enough to start the bullet moving again and pushes the bullet on down the bore and out the barrel. When you seat a bullet on the lands it also pauses for that brief moment, but without any momentum to start with, it takes more pressure building up to get a bullet moving down the barrel than the bullet that has some jump. You should always reduce any book max or near max powder charge by 2% or 3% and work back up when seating bullets on the lands (which I do not recommend) or barely off the lands.

Also, you can seat a bullet to far off of the lands and the pressure begins to rise again, because of over bullet obturation (obturation is the expansion of a projectile to seal off the breech portion of a firearm and prevent the escape of combustion gases). When chamber pressure “strikes” a bullet's base that is entering the bore, it attempts to shorten and will expand (obdurate) the bullet. When this happens the bullet's expansion is constrained by the barrel and pressures have to increase to push it down and out the barrel. The pressure is being applied to the base only, therefore, obturation begins at the base, overtaking more (not all) of the bullet as chamber pressure increases. The further the bullet has to jump the greater this phenomenon impacts the pressure curve. As pressure in the chamber continues to rise, pressure inside the bullet will also rise, overtaking more of the bullet from the base toward the nose of the bullet. Any part of the bullet which is not in close contact with some part of the chamber or barrel, will begin to expand in an attempt to seal the breach and pressure can become dangerously high with a bullet that is seated to far off the lands as well as one seated on the lands.

One should always begin with recommended seating depths listed in reloading manuals and not start with near max or max loads when beginning to work with a cartridge, especially if you are close to the lands or unknowingly to far off the lands. Don’t take short cuts because a certain powder charge and seating depth worked for a different bullet type than the one you are using at the moment. Don’t assume things will be the same, they won’t be, and you could damage your rifle or injure yourself or worse.