Best method for finding bullet seating depth

micksis86 · July 7, 2009, 04:21 PM

I want to know the way you guys find the best bullet seating depth for your specific rifle.

VaFisher · July 7, 2009, 04:28 PM

Trail and error goes a long way. A good starting point is your published COL length in your reloading maual.

Creeper · July 7, 2009, 04:53 PM

Got a few minutes? Read this. Bullet seating is outlined in part 3.

C

rwilson452 · July 7, 2009, 05:00 PM

Slow but sure method without spending more money:

Seat a bullet long, really long. Coat the bullet with a magic marker.

Assuming your doing a bolt rifle,

Carefully put the cartridge in the chamber and close the bolt. rock the bold a bit.
Carefully remove the cartridge by reaching in and not letting the bullet come in contact with the chamber or action. examine the bullet you should see marks left by the rifling. Seat the bullet a couple thousands shorter and repeat the process. At some point you won't get the marks from the rifling. Seat the bullet and extra .02" Once you have the powder adjusted to the best load. it becomes trial and error to find the sweet spot for COAL. usually it will be between .015 and .03 off the lands rifle. Each rifle will be different. even two with consecutive serial numbers.

With revolvers anything that keeps the bullet inside the cylinder is just fine.

Self loading pistols is an entirely different procedure.

VaFisher · July 8, 2009, 06:19 AM

Quote:

rwilson452 Slow but sure method without spending more money:

Seat a bullet long, really long. Coat the bullet with a magic marker.

Assuming your doing a bolt rifle,

Carefully put the cartridge in the chamber and close the bolt. rock the bold a bit.
Carefully remove the cartridge by reaching in and not letting the bullet come in contact with the chamber or action. examine the bullet you should see marks left by the rifling. Seat the bullet a couple thousands shorter and repeat the process. At some point you won't get the marks from the rifling. Seat the bullet and extra .02" Once you have the powder adjusted to the best load. it becomes trial and error to find the sweet spot for COAL. usually it will be between .015 and .03 off the lands rifle. Each rifle will be different. even two with consecutive serial numbers.

With revolvers anything that keeps the bullet inside the cylinder is just fine.

Self loading pistols is an entirely different procedure.

Be advised that this method will not work on all gun's, Weatherby rifles come to mind, they were made with a longer distance before the rifling starts. This gives extra tolerence when loading stronger loads. Simply put that's how Roy Weather over came wanting more out of a caliper. If you were to try to load to the rifling on a Weatherby you may not have any bullet left in the case plus in a bolt action Weatherby the finished round would not fit in the magizine using this method. With that said in most rifles it may work and is no way going to make a round accurate without doing everything else right. No punn intended just trying to make a point.

ragwd · July 8, 2009, 09:27 AM

Creeper, very nice article !

GeauxTide · July 8, 2009, 11:32 AM

1. Published COL
2. Magazine Length

Alleykat · July 8, 2009, 11:40 AM

Are you asking how we mechanically determine the seating depth, or, are you asking how we decide on a seating depth?

micksis86 · July 8, 2009, 04:44 PM

I'm asking how you mechanically find the point where the bullet meets the lands. I did as you guys suggested and now i have a length considerably longer than factory length. However now when i load a cartridge it's very tight on the downward movement of the bolt. Why would this be i thought maybe they weren't sized properly however i'm pretty sure they where. Although my lee die's only tend to go to about the beginning of the head of the case maybe a bit less. They don't touch the shellholder like my redding die's do.

Creeper · July 8, 2009, 05:05 PM

Quote:

Originally Posted by ragwd

Creeper, very nice article !

Thank you ragwd... I wrote it several years ago when I was more involved in benchrest competition. It's certainly not everything, but it's something to get the beginning precision shooter started.

micksis86...
You've seated the bullet too long. It's very easy to do if you have too much neck tension on your dummy test round. The lands can engrave the soft copper of the jacketed bullet quite easily and deeply.

I suggest you try a similar but alternate method. Take the loaded dummy round length you have (you are measuring from case head to ogive with a comparator right... not the somewhat variable tip of the bullet?) and seat your bullet .015" to .020" deeper.
Mark the bullet with the permanent marker and carefully chamber the round... see any land marks on the bullet? Yes? You are very close.
Play with that in .002" to .005" increments until you just can't see any marks.

If you see no marks of any kind on the bullet, you'll need to seat it out .005" longer and try again.
Once more, when you get to the point where going plus or minus .002" will get you visible marks or no marks, you are for all intent and purpose, "just touching" the lands in the throat lead.
You can back off .005" from this point to insure no possibility of firm chambering or sticking a loaded round in the throat

if you want, or you can play with it at just touching.

Cheers,
C

**Unclenick** · July 8, 2009, 05:38 PM

Miksis86,

You've found your problem. That Lee die is supposed to touch down on the shell holder, as Lee's own help video shows. If you are unable to size a case with it so adjusted, something else is amis (i.e., wrong die, defective die, expander too low and hitting casehead, expander too high and jamming case mouth at neck, etc.).

VaFisher · July 8, 2009, 07:28 PM

micksis86, Be advised that if you are up against the rifling depending on your load it could cause excessive pressure to the point it could be very dangerous. Did not know and felt most other subjects have been covered except these dangers.

Alleykat · July 9, 2009, 09:31 AM

Quote:

'm asking how you mechanically find the point where the bullet meets the lands. I did as you guys suggested and now i have a length considerably longer than factory length. However now when i load a cartridge it's very tight on the downward movement of the bolt. Why would this be i thought maybe they weren't sized properly however i'm pretty sure they where. Although my lee die's only tend to go to about the beginning of the head of the case maybe a bit less. They don't touch the shellholder like my redding die's do.

Per Vafisher's last post, you should be a few thousandths off the lands, not hard into the lands. Buy the Hornady (formerly Stoney Point) tool with the dummy case and measure using that system. Then load a few thousandths off the lands and see how you do. I also use a Wilson case gage for setting up my sizing die for proper shoulder bump.

wncchester · July 9, 2009, 10:16 AM

"Although my lee die's only tend to go to about the beginning of the head of the case maybe a bit less. They don't touch the shellholder like my redding die's do."

Not real sure I understand. By "dies", are you refering to the sizer or seater or both? Either way, that's user adjustable.

There is little benefit to finding where to seat to touch the rifling within less than maybe 5 thou. Few, if any, factory rifles shoot well that close anyway. We have to set back from .025" to as much as .125" for best accuracy, at least in my experience. So all we really need is a fairly close starting point to work back from, and then keep exact track of where the best seating depth is.

Alleykat · July 10, 2009, 09:17 AM

.010" to .020" usually works best for me.

**Unclenick** · July 10, 2009, 10:41 AM

Those numbers go all over the map, IME, and you have to find what works in your particular gun by taking a starting load and just changing seating depth until you find what makes the gun happy? I would say most guns fall into liking something in the 0.015"-0.050" range best, but some folks swear only 0.015" is best, or only 0.020", or only 0.025", or only 0.030". Some guns, especially those with long throats that can't be reached by the desired bullet weight, will often do best with the bullet bearing surface about one caliber into the case neck. I used to have a link (can't find it just now) to a German site in which a contributor described South African powder company Somachem at one time offering a service in which they tuned first the seating depth, then the powder charge to make best loads for a rifle. They had been brought an old Mauser hunting rifle with a badly worn throat that they were sure would not do well. Nonetheless, when they moved the bullets back to the right length (still magazine feed capable) then tuned the charge, it turned out to be the most accurate rifle they'd ever made up a load for. So, you just don't know until you try? You can certainly see a 0.010" difference in depth open groups up when you have a tight sweet spot load, so figure you'll have to narrow it down that closely in the end, whatever depth it turns out to be?

Some still work loads up touching the lands. Middleton Tompkins has more long range gold medals than anyone else in history, AFAIK, and uses a variant of that approach for matches that let him use his own loads. He sizes case necks with light friction so they will hold the bullet in transport, but he is still able to push the bullet in or pull it out with his fingers. He seats them out long at the loading bench and lets rifle bolt finish seating them against the throat when he loads the gun. The bullet against the throat then becomes the sole start pressure determining fit (no worry about uniform neck pull). He loads for himself, his spouse and two step daughters, all of whom have been national and international champions. Obviously this is a single-shot only load.

The main drawback to the Tompkins method is you can't unload without the bullet sticking in the throat. To unload, you have to point the gun muzzle-up and open the bolt slowly to catch the case so you don't end up with an action full of loose powder. A cleaning rod then has to knock the bullet out.

Anyway, that approach apparently produces pretty good consistency in the Gallagher/Tompkins guns, which undoubtedly all have short freebore match chambers. I have no idea how that method would compare to others shooting off the bench? Mid Tompkins probably knows, and still uses it. I just mention this to point out it can be done well enough for match shooting and also that the different start pressure reliance is an interesting thing to consider. It is kind of thinking outside the box to take it away from the case neck.

cdoc42 · July 11, 2009, 08:16 PM

Here's the method I've been using for 25 years. I have a Remington cleaning rod that has a green plastic muzzle protector for those who clean from that end. I use it to aid in measuring because it is a flat surface against which I make a pencil mark - which will be more clear as we proceed.

I drop the bullet I am using into the chamber after removing the bolt. Tap it in lightly with the cleaning rod. That bullet is now against the rifling. Drop the cleaning rod gently into the muzzle of the rifle until it stops against the bullet. Make a mark with a pencil half way around the rod at the muzzle end, using the muzzle protector as a flat surface for the pencil.

Knock the bullet out of the rifle from the muzzle end. Seat the bullet in an empty, resized, UNprimed case to a length that is obviously too long. Chamber that dummy round into the rifle. If it won't chamber at all, seat it slightly deeper until it does.

Once chambered, reinsert the cleaning rod into the muzzle end and once again make a pencil mark, but this time spin the rod so that the pencil mark is completely around the rod.

If you have done this right, there should be one pencil mark - the complete circle should have gone right over the half circle. If there is any difference between the two, repeat the process until you have no difference inthe pencil marks.

Now your dummy round has the bullet touching the rifling for that bullet. I use a Stoney Point comparator kit that allows me to measure that bullet essentially from the point that touches the rifling to the base of the case. I label that as OAL-OG (OverAllLength to the OGive.). I then seat that bullet 0.015" deeper from the original seated position and I expect that means my bullet is 0.015" from the rifling. You can start at 0.01 and move up to 0.02" if you feel like really experimenting to see exactly where your rifle likes THAT bullet seated.

If you load more than one type of bullet for your rifle you will need to do this procedure for every bullet type.

You may also need to reset the seating plug when you buy another box of THE SAME bullets as the ogive may not be in exactly the same place as the last lot number. This has rarely been a problem with Nosler bullets and Hornady's SST bullets don't seem to change either. It is an expected variance with Barnes which is why I suspect they advise not to seat the bullets against the rifling. In any case, always seat the new lot number bullet as you normally do and measure with the comparator to be sure the measurement is what you had before.

amamnn · July 12, 2009, 11:50 AM

People who jam seat bullets, as Nick described, also make sure that they have control over neck tension, since jamming increases start pressure in unpredictable increments, unless there is some relief. Most BR or true match rifles are built to withstand more pressure than the common run of factory rifles, but most shooters will still lessen neck tension in order to lighten, but more importantly, control the pressure. Also remember that once you have found the lands with the ogive of bullet A, that does not mean that bullet B is going into the lands the same way, if at all.

If you experience a really stiff bolt closure, that's telling you you have got into the lands and have too much neck tension. Unless you can ensure that the pressure is the same for each round, you will likely not be happy with the results of jam seating.

If you have a rifle with a chamber cut so as to allow jam seating, you might be interested in acquiring some of the tools match shooters use to control neck tension. Forster sells precision over sized expanders and reamers in addition to the usual neck turning equipment. A lot of people like the K&M expander mandrels. Bushing neck dies are also popular. Forster has come out with one that is also a body bump die. Redding has bushing dies and body dies and also FL/bushing dies for loading semi-auto match ammo. Very few rounds are loaded to jam length for semi-autos, other than rounds to be used in slow fire competition where they can be loaded singly.

arizona98tj · July 12, 2009, 09:53 PM

Here is a method....

http://www.stu-offroad.com/firearms/...yoal/oal-1.htm

July 7, 2009, 04:21 PM	#1
micksis86 Senior Member Join Date: June 16, 2009 Posts: 420	Best method for finding bullet seating depth I want to know the way you guys find the best bullet seating depth for your specific rifle.

July 7, 2009, 04:53 PM	#3
Creeper Senior Member Join Date: September 9, 2008 Location: Woooooshington Posts: 1,797	Got a few minutes? Read this. Bullet seating is outlined in part 3. C __________________ Shoulder Drive Nicholson Club

July 7, 2009, 05:00 PM	#4
rwilson452 Senior Member Join Date: June 10, 2004 Location: Tioga co. PA Posts: 2,647	Slow but sure method without spending more money: Seat a bullet long, really long. Coat the bullet with a magic marker. Assuming your doing a bolt rifle, Carefully put the cartridge in the chamber and close the bolt. rock the bold a bit. Carefully remove the cartridge by reaching in and not letting the bullet come in contact with the chamber or action. examine the bullet you should see marks left by the rifling. Seat the bullet a couple thousands shorter and repeat the process. At some point you won't get the marks from the rifling. Seat the bullet and extra .02" Once you have the powder adjusted to the best load. it becomes trial and error to find the sweet spot for COAL. usually it will be between .015 and .03 off the lands rifle. Each rifle will be different. even two with consecutive serial numbers. With revolvers anything that keeps the bullet inside the cylinder is just fine. Self loading pistols is an entirely different procedure. __________________ USNRET '61-'81

July 8, 2009, 05:38 PM	#11
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Miksis86, You've found your problem. That Lee die is supposed to touch down on the shell holder, as Lee's own help video shows. If you are unable to size a case with it so adjusted, something else is amis (i.e., wrong die, defective die, expander too low and hitting casehead, expander too high and jamming case mouth at neck, etc.). __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; July 8, 2009 at 05:44 PM.

July 10, 2009, 10:41 AM	#16
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Those numbers go all over the map, IME, and you have to find what works in your particular gun by taking a starting load and just changing seating depth until you find what makes the gun happy? I would say most guns fall into liking something in the 0.015"-0.050" range best, but some folks swear only 0.015" is best, or only 0.020", or only 0.025", or only 0.030". Some guns, especially those with long throats that can't be reached by the desired bullet weight, will often do best with the bullet bearing surface about one caliber into the case neck. I used to have a link (can't find it just now) to a German site in which a contributor described South African powder company Somachem at one time offering a service in which they tuned first the seating depth, then the powder charge to make best loads for a rifle. They had been brought an old Mauser hunting rifle with a badly worn throat that they were sure would not do well. Nonetheless, when they moved the bullets back to the right length (still magazine feed capable) then tuned the charge, it turned out to be the most accurate rifle they'd ever made up a load for. So, you just don't know until you try? You can certainly see a 0.010" difference in depth open groups up when you have a tight sweet spot load, so figure you'll have to narrow it down that closely in the end, whatever depth it turns out to be? Some still work loads up touching the lands. Middleton Tompkins has more long range gold medals than anyone else in history, AFAIK, and uses a variant of that approach for matches that let him use his own loads. He sizes case necks with light friction so they will hold the bullet in transport, but he is still able to push the bullet in or pull it out with his fingers. He seats them out long at the loading bench and lets rifle bolt finish seating them against the throat when he loads the gun. The bullet against the throat then becomes the sole start pressure determining fit (no worry about uniform neck pull). He loads for himself, his spouse and two step daughters, all of whom have been national and international champions. Obviously this is a single-shot only load. The main drawback to the Tompkins method is you can't unload without the bullet sticking in the throat. To unload, you have to point the gun muzzle-up and open the bolt slowly to catch the case so you don't end up with an action full of loose powder. A cleaning rod then has to knock the bullet out. Anyway, that approach apparently produces pretty good consistency in the Gallagher/Tompkins guns, which undoubtedly all have short freebore match chambers. I have no idea how that method would compare to others shooting off the bench? Mid Tompkins probably knows, and still uses it. I just mention this to point out it can be done well enough for match shooting and also that the different start pressure reliance is an interesting thing to consider. It is kind of thinking outside the box to take it away from the case neck. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; July 10, 2009 at 10:58 AM.

July 7, 2009, 04:28 PM	#2
VaFisher Senior Member Join Date: January 24, 2006 Posts: 596	Trail and error goes a long way. A good starting point is your published COL length in your reloading maual.

July 8, 2009, 09:27 AM	#6
ragwd Senior Member Join Date: May 20, 2006 Posts: 925	Creeper, very nice article !

July 8, 2009, 11:32 AM	#7
GeauxTide Senior Member Join Date: April 20, 2009 Location: Helena, AL Posts: 4,424	1. Published COL 2. Magazine Length

July 8, 2009, 11:40 AM	#8
Alleykat Junior member Join Date: July 26, 2007 Posts: 3,668	Are you asking how we mechanically determine the seating depth, or, are you asking how we decide on a seating depth?

July 8, 2009, 04:44 PM	#9
micksis86 Senior Member Join Date: June 16, 2009 Posts: 420	I'm asking how you mechanically find the point where the bullet meets the lands. I did as you guys suggested and now i have a length considerably longer than factory length. However now when i load a cartridge it's very tight on the downward movement of the bolt. Why would this be i thought maybe they weren't sized properly however i'm pretty sure they where. Although my lee die's only tend to go to about the beginning of the head of the case maybe a bit less. They don't touch the shellholder like my redding die's do.

July 8, 2009, 07:28 PM	#12
VaFisher Senior Member Join Date: January 24, 2006 Posts: 596	micksis86, Be advised that if you are up against the rifling depending on your load it could cause excessive pressure to the point it could be very dangerous. Did not know and felt most other subjects have been covered except these dangers.

July 9, 2009, 10:16 AM	#14
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"Although my lee die's only tend to go to about the beginning of the head of the case maybe a bit less. They don't touch the shellholder like my redding die's do." Not real sure I understand. By "dies", are you refering to the sizer or seater or both? Either way, that's user adjustable. There is little benefit to finding where to seat to touch the rifling within less than maybe 5 thou. Few, if any, factory rifles shoot well that close anyway. We have to set back from .025" to as much as .125" for best accuracy, at least in my experience. So all we really need is a fairly close starting point to work back from, and then keep exact track of where the best seating depth is.

July 10, 2009, 09:17 AM	#15
Alleykat Junior member Join Date: July 26, 2007 Posts: 3,668	.010" to .020" usually works best for me.

July 11, 2009, 08:16 PM	#17
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Here's the method I've been using for 25 years. I have a Remington cleaning rod that has a green plastic muzzle protector for those who clean from that end. I use it to aid in measuring because it is a flat surface against which I make a pencil mark - which will be more clear as we proceed. I drop the bullet I am using into the chamber after removing the bolt. Tap it in lightly with the cleaning rod. That bullet is now against the rifling. Drop the cleaning rod gently into the muzzle of the rifle until it stops against the bullet. Make a mark with a pencil half way around the rod at the muzzle end, using the muzzle protector as a flat surface for the pencil. Knock the bullet out of the rifle from the muzzle end. Seat the bullet in an empty, resized, UNprimed case to a length that is obviously too long. Chamber that dummy round into the rifle. If it won't chamber at all, seat it slightly deeper until it does. Once chambered, reinsert the cleaning rod into the muzzle end and once again make a pencil mark, but this time spin the rod so that the pencil mark is completely around the rod. If you have done this right, there should be one pencil mark - the complete circle should have gone right over the half circle. If there is any difference between the two, repeat the process until you have no difference inthe pencil marks. Now your dummy round has the bullet touching the rifling for that bullet. I use a Stoney Point comparator kit that allows me to measure that bullet essentially from the point that touches the rifling to the base of the case. I label that as OAL-OG (OverAllLength to the OGive.). I then seat that bullet 0.015" deeper from the original seated position and I expect that means my bullet is 0.015" from the rifling. You can start at 0.01 and move up to 0.02" if you feel like really experimenting to see exactly where your rifle likes THAT bullet seated. If you load more than one type of bullet for your rifle you will need to do this procedure for every bullet type. You may also need to reset the seating plug when you buy another box of THE SAME bullets as the ogive may not be in exactly the same place as the last lot number. This has rarely been a problem with Nosler bullets and Hornady's SST bullets don't seem to change either. It is an expected variance with Barnes which is why I suspect they advise not to seat the bullets against the rifling. In any case, always seat the new lot number bullet as you normally do and measure with the comparator to be sure the measurement is what you had before. Last edited by cdoc42; July 11, 2009 at 08:21 PM. Reason: Additional info added

July 12, 2009, 11:50 AM	#18
amamnn Senior Member Join Date: May 13, 2006 Location: WA, the left armpit of the USA Posts: 1,323	People who jam seat bullets, as Nick described, also make sure that they have control over neck tension, since jamming increases start pressure in unpredictable increments, unless there is some relief. Most BR or true match rifles are built to withstand more pressure than the common run of factory rifles, but most shooters will still lessen neck tension in order to lighten, but more importantly, control the pressure. Also remember that once you have found the lands with the ogive of bullet A, that does not mean that bullet B is going into the lands the same way, if at all. If you experience a really stiff bolt closure, that's telling you you have got into the lands and have too much neck tension. Unless you can ensure that the pressure is the same for each round, you will likely not be happy with the results of jam seating. If you have a rifle with a chamber cut so as to allow jam seating, you might be interested in acquiring some of the tools match shooters use to control neck tension. Forster sells precision over sized expanders and reamers in addition to the usual neck turning equipment. A lot of people like the K&M expander mandrels. Bushing neck dies are also popular. Forster has come out with one that is also a body bump die. Redding has bushing dies and body dies and also FL/bushing dies for loading semi-auto match ammo. Very few rounds are loaded to jam length for semi-autos, other than rounds to be used in slow fire competition where they can be loaded singly. __________________ "If the enemy is in range, so are you." - Infantry Journal

July 12, 2009, 09:53 PM	#19
arizona98tj Senior Member Join Date: December 10, 2007 Location: Arizona Posts: 980	Here is a method.... http://www.stu-offroad.com/firearms/...yoal/oal-1.htm __________________ stu-offroad.com Largest Jeep TJ project site on the web! (now with guns)