Bullet Seating Depth
- Thread starter shinny
- Start date
A
abintx
Guest
The easiest method for "me," with my 6PPC and 30 BR [I use Krieger barrels exclusively], is to start at "just touching the lands" and then "working inward", .003" at a time.
Once I think I've found my barrel's preferred seating depth [bullets are going through the same hole], I seat .001" on either side of that setting, as a final refining test.
If I were to change one of the components, including powder lot, for example, I restart the tuning process.
abintx,
Since you stated you use Kreiger barrels excuslively I was wondering if your method applies to both CUT & BUTTONED barrels?
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abintx
Guest
Regardless of which type of barrel I was using, cut or buttoned, this is the method I apply for seating depth tuning, because for me, it's simple. I start at one end of the rifling, and work inward. I'm only concerned with the results that show up on the target, and what they tell me about my rifle's accuracy and how well I've done working up and fine tuning my load and cartridge. I could care less about how the barrel was manufactured.
From your reply seems like my question ruffeled you feathers a bit.....................I apologize if I offended you; I was only trying to confirm your method applied to both types of rifling, as everything in this sport is so precise thought my question was valid. A simple yes would have suficed. I don't know much about this sport and am only trying to learn. Thank you for your reply...
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abintx
Guest
Not at all. Nothing ruffled here. Just tried to convey that the method I use has nothing to do with a specific manufacturing process. My method is only one of many that I'm sure are out there. Too bad others haven't replied with theirs.
M
mks
Guest
Still trying to think of why it would make a difference. The chamber is CUT regardless of how the hole is rifled. The bullet engages a CUT lead in either type of barrel. By the time the bullet travels forward to fully engage the CUT or BUTTONED rifling, I am guessing that the effect of the seating depth is finished, then the effect of the rifling begins, i.e., they are two independent effects. Seating depth effects the first few tenths of a millisecond of burn, during which there is no difference between cut and buttoned. Then the rifling effects the rest of the burn. Strictly an opinion.
There is a lot of "what some guy said" information out there. Most of it is worth what you paid for it, or less.
Just my opinion...
Here's one from column B: Far too many people fail to test from .005 to .020 off the lands. Esp. as an aid to combat horizontal dispersion.
You didn't pay for that, either, but backing it up isn't "some guy," but Gene Beggs, from testing in his tunnel.
SGJennings
New member
Don't know how relevant it is, but Tony B in his book says he sets up the 6PPC different for cut and button rifled. I think I paid about $35 for the book. I'm not claiming anything, just passing along information.
Tony does what he does because after hundreds of barrels, he has noticed a pattern. Very few keep as detailed records on barrels as he does. Does it mean its the only way to skin a cat...NO and he'll be the first to tell you that, it's just what works for him.
I like keeping things consistant and simple so I always start at jam and work out, no matter what barrel bullet combination.
MKS...If I understand what you are saying, then bullet seating depth would make very little difference, however, bullet seating depth is the most important part of a loads tune. Why, I have no idea but you can see it on paper.
Hovis
I like keeping things consistant and simple so I always start at jam and work out, no matter what barrel bullet combination.
MKS...If I understand what you are saying, then bullet seating depth would make very little difference, however, bullet seating depth is the most important part of a loads tune. Why, I have no idea but you can see it on paper.
Hovis
Everyone's opinion is right....
Everyone that gives an opinion here is right...for them. The best way to find the answer to seating depth for your barrel/rifle combination is to find it yourself; by experimenting with powder charge, seating depth, and neck tension. Yep; it will take awhile, but gradually you will develop a technique that works for you and will only take a short time to accommodate a new barrel or powder/bullet change.
No one here can give a definitive answer to load development for every rifle combination. This area is one that defines the top shooters in the winner circle (load development, condition reading, and rifle handling.)
Some shooters catch on fast...and others never do; because they keep chasing equipment changes, other cleaning techniques, and the ultimate bench setup, thinking that if only they can get the right combination in these areas, they will shoot those teen groups every time.
So...get out there with your rifle and reloading equipment and find that right combo for YOU.
Good luck...virg
Everyone that gives an opinion here is right...for them. The best way to find the answer to seating depth for your barrel/rifle combination is to find it yourself; by experimenting with powder charge, seating depth, and neck tension. Yep; it will take awhile, but gradually you will develop a technique that works for you and will only take a short time to accommodate a new barrel or powder/bullet change.
No one here can give a definitive answer to load development for every rifle combination. This area is one that defines the top shooters in the winner circle (load development, condition reading, and rifle handling.)
Some shooters catch on fast...and others never do; because they keep chasing equipment changes, other cleaning techniques, and the ultimate bench setup, thinking that if only they can get the right combination in these areas, they will shoot those teen groups every time.
So...get out there with your rifle and reloading equipment and find that right combo for YOU.
Good luck...virg
M
mks
Guest
I'm not saying that seating depth doesn't make a difference. Just that cut versus buttoned in the CHAMBER doesn't make a difference. It seems likely that Tony is using different seating depths to compensate for differences between cut versus buttoned in the REST OF THE BARREL.
There is a big piece of the initial question that was asked that might as well be brought up now.
Rule of thumb:
1. FB bullets shoot better in Button rifled barrels than BT bullets. This is thought to be because a button barrel (due to the pressing of the rifling in the metal) has microscopic waves (for lack of a better term coming to mind) in the barrel and bullets with power/driving bands seal against the bore better.
2. BT & FB bullets of the same quality will shoot equally well in cut Rifled Barrels. This is where I have heard different opinions on why BTs have became popular in recent years. A few bullet makers have mentioned to me that if the jackets are not of very high quality, that a BT made on that jacket will generally outshoot a FB made on the same jacket. The explanation by some was that the radius of the jacket that forms the power/driving band on a FB bullet is where the biggest variance in the jacket will be and that riding on the barrel causes a larger problem with the bullet traveling straight as it goes down the bore and a larger CG variance, whereby, a BT bullet, does not ride on this area and will travel down the bore straighter and pushes the variance more toward the centerline of the bullet thus less CG variance. I have spoken to other Bullet makers that disagree with this example.
3. FB bullets...start at jam and work out. This is with either Button or Cut Rifled Barrels. BT bullets...should be used in cut rifled barrels and should start at a light kiss and go in (I don't do this).
Like I said, these are kind of rules of thumb and don't always pan out. I do subscribe the the thought of not jumping bullets in short range BR but there is always variables that can throw a monkey wrench in the process.
Hovis
Rule of thumb:
1. FB bullets shoot better in Button rifled barrels than BT bullets. This is thought to be because a button barrel (due to the pressing of the rifling in the metal) has microscopic waves (for lack of a better term coming to mind) in the barrel and bullets with power/driving bands seal against the bore better.
2. BT & FB bullets of the same quality will shoot equally well in cut Rifled Barrels. This is where I have heard different opinions on why BTs have became popular in recent years. A few bullet makers have mentioned to me that if the jackets are not of very high quality, that a BT made on that jacket will generally outshoot a FB made on the same jacket. The explanation by some was that the radius of the jacket that forms the power/driving band on a FB bullet is where the biggest variance in the jacket will be and that riding on the barrel causes a larger problem with the bullet traveling straight as it goes down the bore and a larger CG variance, whereby, a BT bullet, does not ride on this area and will travel down the bore straighter and pushes the variance more toward the centerline of the bullet thus less CG variance. I have spoken to other Bullet makers that disagree with this example.
3. FB bullets...start at jam and work out. This is with either Button or Cut Rifled Barrels. BT bullets...should be used in cut rifled barrels and should start at a light kiss and go in (I don't do this).
Like I said, these are kind of rules of thumb and don't always pan out. I do subscribe the the thought of not jumping bullets in short range BR but there is always variables that can throw a monkey wrench in the process.
Hovis
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abintx
Guest
Hovis,
You might want to explain to Shinny what you mean by your use of the term JAM, and why "working out" may not mean "jumping." I didn't want to get into that earlier because it can be confusing for some.
You might want to explain to Shinny what you mean by your use of the term JAM, and why "working out" may not mean "jumping." I didn't want to get into that earlier because it can be confusing for some.
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abintx
Guest
On the very top of page 254 of Mr. B's book he mentions tuning differently beginning in 2008 when using "cut-rifled" barrels in conjunction with "boat tail" bullets, by saying that he begins the tuning process from the "touch point" and not from (the) "jam"(point). This seem to be the only exception since he doesn't mention another barrel type.
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abintx
Guest
Pushing it further into the lands/rifling.
From a thread on horizontal stringing:
* * *
From HovisKM
How do we test this? Only way I can thing of is to use the bottom off a Sabot, use it as a wad, & see if velocity goes up. The microscopic waves would have to be less than .0001, or they'd show up in an air gauge, right?
Most of my shooting during the past several years has been in the wind free environment of the tunnel. One thing that continues to repeat with every gun, barrel and bullet combination I have worked with is that horizontal dispersion results from the bullets being seated too far into the lands and vertical dispersion is the result of the powder charge being either too hot or too light.
Daryl Loker told me years ago that you tune out the horizontal with neck tension and bullet seating depth, then tune the vertical out with the load. (Or in recent years since the advent of tuners, with the tuner.)
I assure you, if I put my standard load of powder in and seat the bullets on hard jam, I'll have two bullet holes of built in horozontal, and that's in a tunnel with no wind! Start pushing the bullets back into the case .005 at a time and the horizontal will disappear just when the bullets come off the lands or just kissing. You might as well keep this to yourself after you see it with your own eyes because no one will believe you if you try to tell them; it goes completely against conventional wisdom.
Gene Beggs
* * *
From HovisKM
How do we test this? Only way I can thing of is to use the bottom off a Sabot, use it as a wad, & see if velocity goes up. The microscopic waves would have to be less than .0001, or they'd show up in an air gauge, right?
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Bob Brushingham
Member
I have always started at just touching and went into the rifling with both type of rifling, My reasoning is jam varies with neck tension and neck tension varies with number of firings on the case. It has worked for me.
Bob
Bob
Charles wrote - "The microscopic waves would have to be less than .0001, or they'd show up in an air gauge, right? "
Probably would, but I don't have an air guage....just sayin'...catch my drift...etc...
Likely, folks believe stuff based on a particularly successful outing. They use those beliefs and continue along the path and every subsequent success reinforces the belief regardless of how many unsuccessful instances they encounter.
Probably would, but I don't have an air guage....just sayin'...catch my drift...etc...
Likely, folks believe stuff based on a particularly successful outing. They use those beliefs and continue along the path and every subsequent success reinforces the belief regardless of how many unsuccessful instances they encounter.