Seating depth term confusion????

[galold]

I understand when the term,performs best jumped by as much as .025".) is used, the bullet is back from the lands .025". When the term , bullets jammed in the lands .010" or more) is used, does this mean the bullet is actually seated out from the lands into the riflings? Thanks, can you tell I'm a novice?

 

[gambleone]

The phrase, "jammed into the lands" just means that the bullet, in the case you referred to, .010 into the lands, is .010 distance to the lands. Some say the bullet jumps into lands, & some say bullet is jammed into lands, which can be a little misleading if you're not used to the jargon or terminology.
Happy shooting, Greg

 

[skipper]

When I say that my bullets are jammed .010 into the lands, I mean that they touch and then are pushed .010 farther than touching. They are .010 more than just merely touching.

If I chamber a round and then open the bolt and eject the round there are definite land marks on the bullet.

 

[NorCalMikie]

What Skipper said is just that. Jammed into the lands.
Found out something yesterday at the range. 6BR,Savage action,
3 different OAL loads. All the same bullet weight and powder charge. .010 off the lands,flush and .010 into the lands. Hard bolt lift off the lands and flush. .010 into the lands, bolt opens smooth as silk. I'll take .010 into the lands everytime.

 

[Forum Boss]

Mikie,

I had the same experience with my Savage PacNor 6BR, and the chronograph showed that .015 away,jump) from "just touching" pressured up faster than .015" into the lands.

Some of this depends on the cartridge and your freebore. But in a short case, the .030" difference between .015" IN and .015" OUT was enough to create pressure issues.

.010-.015" IN works so well in the 6BR with so many bullet/powder combos, that's where I suggest people start. It's also a good idea to fireform cases with land contact. So, if one starts into the lands, you don't have to adjust your loads and seating depth very much after fire-forming.

 

[gambleone]

I wasn't aware that you could actually push the bullet that far into the riflings without high-pressuring your chamber.
Greg

 

[NorCalMikie]

We're talking about Savage actions. I was wondering if the guys with other actions,Remington etc.) were seeing the same situation. It might have something to do with the "floating bolt head". Anybody else see the same thing or is it just the Savage that acts that way? As long as the bullets are jammed, the problem doesn't show up. I've got 2 different Savage rifles and they both will show the problem.

 

[Mikem]

I currently have a test batch of 6BRs for my Savage/Pac-Nor combo waiting just to test for this problem, and any accuracy improvements. The load is my standard 80g Berger and 30.5g of Varget,3010 fps 26" bbl) normally set at .010 in to the lands, and this batch moves out to a .010 jump in .005 increments.
Ill set up the Crony to see just whats happening with speed, ES & SD, as this is the first time I have tried a jump with this load in this rifle.
I did try a larger jump with 74g SMKs once, as I cant get to the lands with that bullet. I had no problems, except no accuracy. And I consider that a big problem. The solution to the 74g problem is, I give them to N.C.Mikie, he has a barrel that can jam them.
Mike.

 

[Cheechako]

A good thing for any shooter to do is to establish the maximum "into the lands" length for your particular bullet/throat/neck tension. This can be done by seating a bullet,dummy round) to ever increasing OAL, chambering the cartridge, extracting and then measuring from base to ogive. You will find that you will reach a point where the dimension from base to ogive will not get any longer regardless of how far out you seat the bullet. It might surprise you as to how far "into the lands" you can actually load for that particular combination.

Seating length will change as the throat wears so it needs to be checked every so many rounds. I usually check mine every 500 rounds minimum but some hi-intensity cartrtidges,barrel burners) can benefit from a check up after every tournament.

Keep records.

Ray