Seating bullets long and what it does to load data.

[Bayourambler]

I have never seated the my bullets way out and need some info. The throat on my rifle is deep and I will have to seat the bullets pretty far out to reach .020" off the lands. What is the norm here? Can I get where I need to be without having to cross max charges?

 

[Sunray]

"....020" off the lands..." 20 thou may or may not be what your rifle likes. There is no 'norm' for the distance off the lands. Every rifle chamber, in every rifle, is different. Figuring out the distance your rifle prefers is strictly a trial and error thing that isn't really needed. Isn't needed at all until you've work up the load.
Anyway, first you need to figure out the exact max OAL for that chamber, where the bullet touches the lands and work back. Load a test cartridge with no powder or primer with the bullet being long and secure enough to cycle, but not crimped at all. Chamber it gently and the lands should push the bullet into the case. That's your starting point. But not until you have worked up a load. And not if you don't feel like it. The entire thing is a load tweaking technique that really doesn't make a lot of difference one way or the other.

 

[rsrocket1]

By the looks of your Avatar, are you loading for hunting rounds?
If so, you shouldn't be worried about getting the last fraction of MOA out of your load development. You want maximum reliability and ease of feed into the chamber.

If on the other hand, this is for punching paper at long distances, you first develop a load that is insensitive to slight variations in charges (find a node), then adjust the seating depth if there is a noticeable change in accuracy as you get closer to the lands. If the jump distance isn't making a difference in accuracy, you're finished. The good thing is with a rifle cartridge, the percent change in MV is much less sensitive to seating depth than with a small case pistol cartridge so you may not have to go back and forth tweaking the charge weight, then the seat depth and back again to the charge weight.

 

[Andrew Leigh]

I think that hunters often try borrow the reloading practices of bench shooters, chasing the lands is one of those.

The grouping in my avatar is a .375H&H which is over .285" off the lands. Cannot get closer with my chosen bullet.

There are two dynamics at play here. The first is the internal ballistics and the second is inertia.

So yes, while seating further out increases the internal volume of the case and results in a drop in the internal pressure, this is only true when you discount the effect of the inertia the bullet will face when overcoming entry to the lands. In tests I conducted on a .308 it became apparent that there was a gradual drop in pressure until the bullets approached 0.040" from the lands. After this the pressures began to lift dramatically as the full effect of the inertia was experienced.

So the above is the plot of my results. The pressure drops gradually from 0.080" to 0.040" and then as the effects of inertia come into play then the pressure lifts.

 

[Walkalong]

For most applications chasing the lands is a waste of time IMHO.

 

[Bayourambler]

For most applications chasing the lands is a waste of time IMHO.

You are probably right , but I fix wrecked cars for a living and I can tell you that getting new parts to fit and work is ALWAYS a combo of several things!! It's never One magic trick to make it work. A lil here , a lil there is the way my brain works!!

 

[Orcon]

There's a relationship between bullet jump and pressure and, as Andrew illustrated, it is not linear. As a general rule I try to stay at least 0.020" off the lands because of the bullet shapes I use and my goal of seeing 100% powder fill. However...

I have a Rem 700 (308 Win) that has approximately 4 miles of free-bore, in most applications I cannot touch the lands and keep a bullet in the neck. Though, if you are interested in single loading and shooting long for caliber bullets, this can be a boon. I can load a 208gr Hornady A-Max to just under 3" and safely be off of the lands, this allows me to go over book max by a fair margin and get velocities that typically wouldn't be possible with slow burning spherical powders. Do remember though, you have to ask yourself if your face/hands/rifle are worth the risk.

 

[Haxby]

hunters often try borrow the reloading practices of bench shooters

I have to say: Well stated.

I have some accurate loads, for a few rifles. I don't know how far off the lands any of them are. None are close
within a few thousandths.
If you're shooting kneeling, slung, prone, under 1 moa, with hunting bullets, feeding from the magazine, how much better are you going to get?

 

[Walkalong]

You are probably right , but I fix wrecked cars for a living and I can tell you that getting new parts to fit and work is ALWAYS a combo of several things!! It's never One magic trick to make it work. A lil here , a lil there is the way my brain works!!

I did body work for a little over three years many moons ago, and I get it. That said, the gain may be little to nothing in your application, and may even cause other issues. There are better ways to make gains IMHO.

The throat on my rifle is deep and I will have to seat the bullets pretty far out to reach .020" off the lands. What is the norm here? Can I get where I need to be without having to cross max charges?

All reasons not to. Deep throat? Then don't bother. Without having to cross max charges? See Andrew Leigh's post. Some (Many) bullets are designed to jump to the lands. That is how the vast majority of them are shot, making that jump, whether it is factory ammo, or reloads.

 

[spitballer]

Hmm, I see what you mean: the longer throat effectively increases case volume. If it were me I'd be more concerned about distance to the lands than increased case volume though.

 

[ants]

It's fun to try. You learn something new, even if you learn that
it makes no difference in your particular rifle. Go ahead and try it.

Don't forget, your cartridge cannot be longer than magazine length unless you shoot single shot.

Also don't forget, 0.020" off lands will change if you buy different bullets.
The distance we're talking about is from the bullet's curved ogive to the lands.
A different bullet will have a different curve, and change the distance altogether.

Unless your OAL is way, way out there like Orcon was saying,
the difference in case volume is negligible for many cartridges.
Go ahead and try, you'll see if it makes a difference in your particular rifle.

 

[ants]

By the way, following Andrew Leigh's post, which I 'liked':

My Weatherby rifles have really long throats, designed to
control pressure in magnum cartridges just as Andrew's graph shows.
The long throat doesn't hurt accuracy at all.
Weatherby's are very accurate hunting rifles.
Trying to load them close to the lands increases pressure
without increasing accuracy.

 

[Orcon]

To piggyback on ants comment about bullet shapes and lengths, here's a picture of some of the bullets I use. Notice the differences?



30 cal bullets left to right:
125gr Sierra Match King
150gr Remington Corlokt
168gr Hornady A-Max
175gr Sierra Match King
180gr Nosler Partition
180gr Trophy Bonded Tip
180gr Swift Sciroco
180gr Barnes TSX
200gr Hornady ELD-X
210gr Berger VLD

 

[GRIZ22]

For most applications chasing the lands is a waste of time IMHO.

^This.

I have a 308 load I developed years ago to duplicate 7.62 NAT0 loading including OAL. It shoots well in the semiauto I had then. I've got 3 more 308 rifles now. It shoots well in my other semiauto and an inch or a bit less in my bolt guns. I don't shoot benchrest.

Yes, I could probably get group sizes down some. But how much accuracy do I need? I have enough. I'm not going to work up a load for each rifle.

 

[Bayourambler]

It's just to mess around with, after all this is a hobby!! I can shoot up to 1400 yards right here behind my house!!! My new 300 win mag and couriosity has got the best of me!! Did some ladder testing today at 300 yds. with 30-06 and its all starting to make more sense to me.