Backing off the bullet seating depth

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Morrey

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I used a Hornady bullet OAL gauge to find the ogive distance to the rifling in a new Bergara .308 bolt gun. If I have consistent readings of OAL 2.2525 ogive to the rifling, what would be an acceptable distance to back that off? How much jump would I want to start with for a few test loads? This is a Sierra Pro-Hunter 150 gr bullet.
 
Sierra work well at 0.030" off lands. I normally start at 0.020" if not restricted by magazine length.

Good information...thanks! If I back off 30 thousandths, that will put me at 2.222 which is an easy number to remember and deal with. Since this is an all purpose hunting round, I'll be glad for 1.5 MOA groups and not stress too much over things.
 
Agree that .020" is a good starting point.

If I have consistent readings of OAL 2.2525 ogive to the rifling...
To clarify for everyone's benefit, I suspect you meant 'base-to-ogive is 2.2525.' The OAL is base-to-tip.
 
This procedure has nothing to do with accuracy, but is important for function. Seat the bullet to your preferred depth, load a round, close the bolt as fast as you can, and extract the round. If the bullet stays in the throat, you need to seat it deeper.

A stuck bullet is difficult to remove without a cleaning rod, and sometimes, the cleaning rod is miles away from the gun.
 
Every gun likes something different. You have to experiment. For hunting don't sweat .5 inch.

For sure @Jack B. , if I was shooting for groups, I'd be much more critical and do multiple sessions of load workups and testing. In my area, shots on wild hogs and whitetails are usually less than 150 yards. We hunt from tree stands and tower stands, and often setup bait piles at 100 yards.

I just made a dummy round (2.222 base to ogive) for sizing and chamber tests... fits in the magazine and chambers/extracts slick as butter. I'll drop in 46.1 gr of IMR 4064 which should push a 150 gr Sierra Pro-Hunter at 2800 fps. I don't know many game animals in my area that can stand the heat of that round.
 
I used a Hornady bullet OAL gauge to find the ogive distance to the rifling in a new Bergara .308 bolt gun. If I have consistent readings of OAL 2.2525 ogive to the rifling, what would be an acceptable distance to back that off? How much jump would I want to start with for a few test loads? This is a Sierra Pro-Hunter 150 gr bullet.
Please define your mission also are you restricted to magazine length
 
Good information...thanks! If I back off 30 thousandths, that will put me at 2.222 which is an easy number to remember and deal with. Since this is an all purpose hunting round, I'll be glad for 1.5 MOA groups and not stress too much over things.
Excuse me please,
Picking an arbitrary number to seat from because it sounds good is not a very good idea. You might as well just buy ammunition if that’s how your going to roll.
I also know for sure that not one person on this thread can tell you the ideal seating depth for your rifle.

Sure you have a punchers chance of tripping across a good load but the odds are long.
 
Excuse me please,
Picking an arbitrary number to seat from because it sounds good is not a very good idea. You might as well just buy ammunition if that’s how your going to roll.
I also know for sure that not one person on this thread can tell you the ideal seating depth for your rifle.

Sure you have a punchers chance of tripping across a good load but the odds are long.

I see your point, but isn't store bought shelf ammo just a likely to offer the same longshot odds of tripping across a good store bought load? A bullet maker would have much less information on my particular rifle than I do after measuring my particular projectile til it touches the rifling. I frankly don't get what is so confusing about asking what is a proper starting distance to back the bullet off the rifling? 20 thousandths is a starting point many folks suggest backing off the seat depth.

I have all of the components to build a round without any additional costs of buying expensive ammo. If I load safely and carefully not to load unsafe ammo, I think that is not too hard to understand. I'm not trying to create match grade ammo - just some rounds that are hunting quality that get the job done.
 
From the Hornady instruction manual for their O.A.L. Gauges and what they recommend.

USE COMMON SENSE WHEN SELECTING A BULLET SEATING DEPTH. We recommend a free-travel (clearance) of .020" to .040" between the bullet and rifling lands for hunting rounds. In our experience, excessive bullet free-travel (over .040") will most often result in a loss of accuracy. However, each gun will have its own preference, and it is up to the handloader to determine the optimum bullet free-travel by range testing the
loads. There are no short cuts in this area. However, once the optimum free-travel is determined with one brand of bullets, this same free-travel dimension will most often be preferred with other bullet brands or weights. Remember, if other bullet models or weights are chosen, they will have differently shaped ogives, which will require that you repeat the O.A.L. Gauge process with the new bullet. While not absolute, there are several reasons for our free-travel recommendation: (1) A more uniform chamber pressure is produced to start the bullet down the bore. This reduces pressure “spikes” resulting from an interference fit. The result is a more uniform velocity which produces accuracy. (2) As the bullet is aligned in close proximity to the rifling, it will stabilize quickly as it exits the bore. (3) Safety and reliability; a .020" to .040" free-travel produces reliable feeding and extraction.
 
In general, for a hunting rifle, I want 5 thousandths or a touch more off of the lands, just to ensure any fouling, stray partially burned kernel, what have you, which finds its way to my leade doesn’t end up sticking me in the lands. Some bullets prefer more jump than 5thou, and only a rare few would ever need less - not typically hunting/field bullets. Just have to know what your bullet likes before you start, or figure it out.

isn't store bought shelf ammo just a likely to offer the same longshot odds of tripping across a good store bought load?

Therein lies the reason most folks who want extreme precision aren’t doing it with factory loads.
 
A lot of time I use the mfg recommendation on OAL. I have found that Sierra recommendation are pretty close unless you have a non SAAMI spec chamber. That is why I said Sierra like 0.030", its what you have if everything is in spec. I have on a few occasions had to reduce the OAL due to min spec chambers.
 
Excuse me please,
Picking an arbitrary number to seat from because it sounds good is not a very good idea. You might as well just buy ammunition if that’s how your going to roll.
I also know for sure that not one person on this thread can tell you the ideal seating depth for your rifle.

Sure you have a punchers chance of tripping across a good load but the odds are long.
That's not terribly arbitrary. He's in the middle of where good accuracy is usually found. Finding the optimum powder charge has more to do with hunting accuracy than seating depth within reason.
Look at the rifles that use a tremendous amount of freebore but still shoot well inside hunting requirements.
 
That's not terribly arbitrary. He's in the middle of where good accuracy is usually found. Finding the optimum powder charge has more to do with hunting accuracy than seating depth within reason.
Look at the rifles that use a tremendous amount of freebore but still shoot well inside hunting requirements.

This is exactly my reasoning @Bfh_auto. If 20 - 40 thousandths is a typical safe range, I simply split the middle to back the depth off 30 thousandths. I don't feel this number is arbitrary at all, in fact, I think I made a darn good decision with this number.

(3) Safety and reliability; a .020" to .040" free-travel produces reliable feeding and extraction.

As @Jack B. quotes directly from Hornady, I feel I went directly in the middle of the most safe zone possible. I'm not chasing accuracy...I simply want a hunting load. "That's how I roll".
 
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