[Outlaws]

*Please bare with me on this long winded post*

So I finally got a OAL Gauge and the bullet comparator and insert for my .243WIN.

I was curious about bullet seating depth from the lands and how it affects accuracy since I was getting about nickle sized groups at 100 yards. I wanted to see if I can shrink it ya know...who doesn't. :P

So anyways, I have two different bullets. The 65 grain Hornady V-Max, and Speer BTHP....I think they are game king(?) About 85 grain if I recall....I don't have the box its out in the storage shed at the moment.

Now I set up my caliper with the comparator and insert and found it about +.035 from being exactly 1". So I reset calibrated it to read 1.000 (I will be using that extra inch in my measurements here).

So I put the empty cartridge in and it chambers fine. I added teh Hornady 65 Vmax and slowly inserted the plunger thing until I felt the bullet hit the lands very gently.

Measurement on the caliper to the Ogive = 3.249" (so actually 2.249)
I disassembled everything and repeated. New measure was the EXACT same. :P

Now the problem.

The after disassembling and repeating with the Speer, the measurement = 3.268" (2.268)
I disassembled and repeated. New number = 3.268 The same as before.


So I guess the thing is that if this is to measure the Overal length to the lands, how can I get two seperate numbers and they both get repeated? It doesn't seem logical to me at this moment in time. I can see the OAL be different for all bullets, but the length to the Ogive should be the same since its to the lands right????????

[Outlaws]

So I am researching more on the net....every bullet has a different ogive length even in the same rifle? I thought the ogive is one and the same as the distance to the lands?

[Bullet]

Outlaws

If you take a marker and color your bullet and then chamber your dummy rounds you will see the marks from the lands easily. You will also see marks from where your bullet comparator contacts the bullet. These usually will not be the same. Comparators aren’t usually measuring from the part of the bullet that makes contact with the lands, but are used as a reference measurement for setting seating depth and will differ with different shaped bullets (weight / brand).

From SAAMI’s Glossary -

OGIVE
The curved portion of a bullet forward of the bearing surface.

http://www.saami.org/Glossary/index.cfm


Your seating die will probably seat your bullet from another place on the Ogive too. Use your measurement you made with your comparator (on your dummy cartridge) to set your seating die or adjust longer or shorter depending on where you want to be in relation to the lands.

[Outlaws]

I still don't get it all the way....I will post a pic of what I am getting at....

See, the area the bullet at the ogive should be the same diamater across on any bullet since a .243 is gonna have a barrel about .24 right? So if you shove a case and a bullet into the chamber and have the ogive of both TOUCH the lands, should the ogive be the exact same?

http://www.battletone.com/guns/tempstuff/ogive.jpg

[mc223]

I think you are on the right track, however as in "bullet's" post, a marker will show the actual line of contact. then be careful not to push the bullet too far into the comparator. It's easy to do with the sharper pointed bullets.(longer ogive) Also bear in mind that .003 in diameter will trig to up around .014 in length distance, depending on the actual ogive contour of the projectile. The number you get for 2 different style bullets should be within a couple thousandths since you are effectively measuring the distance to the lands, which is not variable.

[mete]

It seems you don't understand the definition of ogive. It is a curve not a diameter. Your drawing #1 -the ring you drew is not the ogive .As the definition says ,it's a curve ! The rear of a bullet has parallel sides then it starts to curve toward the nose .Some curves are more gradual and some are more abrupt.Because of the different curves a specific diameter is going to be at a different distance from the base of the bullet for each different ogive. "Hatcher's Notebook" p 572, shows different ogives [curves of the sihouette of the bullet] for different bullets ranging from an ogive of 0.5 [ a blunt round nosed bullet] to an ogive of 10 which is a very long gradually curved pointed bullet.

[USSR]

Outlaws,

Your 2nd depiction shows it correctly. In the 1st depiction, if the 2.249" base to ogive was correct for that bullet, it would be impossible for you to insert a cartridge loaded with the round nose bullet at the overall length of 2.268" without forcing the bullet down into the case. Forget about the cartridge overall length (except if it's too long to magazine feed).

Don

[Matt-man]

The hole in your comparator is not necessarily the same diameter as the bore where the rifling contacts the bullet. Measurements are going to differ for each bullet design since each design's nose has a different curve, and the comparator and the rifling are contacting the bullet at different places.

What you DO know now is how far out to seat each bullet to touch the lands. Use the 2.249" number for the Hornadys and 2.268" for the Speers, and adjust as you see fit.

[Outlaws]

the comparator and the rifling are contacting the bullet at different places.

Thanks. Thats what I wasn't understanding. I was so hung up on why an area that is supposedly .24 isn't the same distance to the next area that is .24 on the other bullet/lands....not even thinking that the two holes I am craming bullets in are not the same size. :banghead:

:D :D :D

[USSR]

the comparator and the rifling are contacting the bullet at different places.

BS. The comparator will contact the bullet ogive at the same point as the bullet will contact the leade. I use the same setup you have for 1,000 yard competition, and have used it for years to ensure that the bullet's ogive is exactly where it is supposed to be in relation to the leade.

Don

[Matt-man]

The comparator will contact the bullet ogive at the same point as the bullet will contact the leade.

How do you know this is true?

Consider this: The Stoney Point .30 comparator has a different diameter than the Sinclair .30 comparator. If I stick a 175gr SMK in the Stoney Point, I get a distance of .650" from the base to the ogive. If I use the Sinclair, it's .580". Obviously they each touch the bullet at different places along the ogive. Which one touches the bullet at the same point as the leade in my M1A?

It isn't necessary for the comparator to contact the bullet at the same point as the leade in order for the comparator to perform its function. By using the OAL gauge with the comparator, Outlaws now knows the case-head-to-ogive length that gives him 0 jump for each bullet, and that's what matters.

[USSR]

How do you know this is true?

Simple. My .30-06 load consists of a 190SMK loaded so that the bullet ogive is .010" off of the leade. If I load the bullet just over .010" longer, the bullet ogive makes contact with the leade and the bullet is pushed deeper into the case (I only use about .001" neck tension).

Don

[Matt-man]

I'll restate the question: How do you know where the leade touches the bullet, and how do you know that your comparator touches the bullet in the same place?

It doesn't really matter anyway. The number you get out of the comparator doesn't mean anything except as a reference from the case head to the diameter of the comparator's bore. As long as you know what your reference distance means then you can set your seating depth accordingly. In this case 2.249" with the Hornady bullet means it's just touching the lands, so 2.239" on the comparator is .010" off the lands. The comparator does not need to contact the bullet in the same place as the rifling in order for this to work, because moving the bullet back .010" using any point of reference moves the bullet back .010" off the rifling. As long as the point of reference is always the same (meaning, always use the same comparator), it will work.

[Bullet]

Quote:
the comparator and the rifling are contacting the bullet at different places.

USSR Quote – “BS. The comparator will contact the bullet ogive at the same point as the bullet will contact the leade. I use the same setup you have for 1,000 yard competition, and have used it for years to ensure that the bullet's ogive is exactly where it is supposed to be in relation to the leade.”

Don

From SAAMI’s Glossary -
LEADE (LEAD)
That section of the bore of a rifled gun barrel located immediately ahead of the chamber in which the rifling is conically removed to provide clearance for the seated bullet. Also called Throat or Ball Seat.
FREE BORE
A cylindrical length of bore in a firearm just forward of the chamber in which rifling is not present. Associated with bullet jump.
LAND, LANDS
The uncut surface of the bore of a rifled barrel.



USSR
I don’t know what kind of comparator you have. I use the Sinclair. I can guarantee you that my comparator does not touch the bullet in the same place as the lands.


Outlaws Quote – “Thanks. Thats what I wasn't understanding. I was so hung up on why an area that is supposedly .24 isn't the same distance to the next area that is .24 on the other bullet/lands....not even thinking that the two holes I am craming bullets in are not the same size.”

I believe you now understand why you’re getting different measurements for different bullets.

[Outlaws]

I believe you now understand why you’re getting different measurements for different bullets.

Yes I do. :D

[USSR]

USSR
I don’t know what kind of comparator you have. I use the Sinclair. I can guarantee you that my comparator does not touch the bullet in the same place as the lands.


Bullet,

Very same comparator that I use. If yours doesn't work the way it's designed to, send it back. Not sure why you included the SAAMI definitions, but as you can see, the leade is the point at which the bullet ogive contacts the barrel, although many people refer to it as the lands. Technically, the lands runs the full length of the barrel, and contact of the bullet with the lands does not begin until the bullet is pushed past the throat and begins to be engraved by the lands. I would suggest going to http://www.snipershide.com to talk with some knowledgeable people and get a better understanding of determining how to determine just exactly where your throat is.

Don

[Bullet]

USSR Quote – “Not sure why you included the SAAMI definitions, but as you can see, the leade is the point at which the bullet ogive contacts the barrel, although many people refer to it as the lands.”

From SAAMI’s Glossary -
LEADE (LEAD)
That section of the bore of a rifled gun barrel located immediately ahead of the chamber in which the rifling is conically removed to provide clearance for the seated bullet.


I see SAAMI’s got it wrong and the marks left on my bullet aren’t really from the lands they are from the leade and my comparator doesn't work the way it's designed to.

One question – if the comparator is measuring from the exact same place on the bullet that the leade (lands) are then how do you get different measurements with different shaped bullets since your actually measuring the distance from the bolt face to the leade (lands)?

[USSR]

Bullet,

Look at it this way, in a .308 Win, the lands are at .300" while the grooves are .004" deep, resulting in a total of .308". Since the bullet ogive is basically the point at which the bullet is approaching .308" in diameter as you come back from the bullet point, the nearly .308" portion of the bullet HAS to make contact with that portion of the barrel between .308" and .300", hence the leade. Talk to a barrelmaker if you don't believe me.

Don

[steve4102]

Bullet, you are correct! The comparator does not and can not take it's measurements on the bullet in the EXACT same place as were the bullet first touches the barrel. It would be impossible for the makers of these comparators to match the millions of rifle barrels out there. The OAL gauge sets the bullet for your particular rifle, when the comparator is used we now have a "Comparing Point" not the exact point on the bullet that touches first. The only way for for these two points to be the same is if the hole in the comparator is an EXACT match for the rifle, and that is impossible. The comparator is just that, a comparing tool, not a way the get an exact accurate measurement of head to rifling.

[USSR]

Bullet, you are correct! The comparator does not and can not take it's measurements on the bullet in the EXACT same place as were the bullet first touches the barrel. It would be impossible for the makers of these comparators to match the millions of rifle barrels out there. The OAL gauge sets the bullet for your particular rifle, when the comparator is used we now have a "Comparing Point" not the exact point on the bullet that touches first. The only way for for these two points to be the same is if the hole in the comparator is an EXACT match for the rifle, and that is impossible. The comparator is just that, a comparing tool, not a way the get an exact accurate measurement of head to rifling.

This isn't rocket science, folks. Although maybe it is for some of you. Bullet ogive is bullet ogive, and the combination of using the Stoney Point OAL Guage and a comparator DOES allow you to adjust bullet seating depth so that you are whatever distance you want to be off any rifles leade/throat. Long range tactical and precision shooters use these tools all the time. But, rather than continue to argue the point, why don't you go to a site with knowledgeable precision shooters such as the http://www.snipershide.com site that I mentioned and ask people who know.

Don

[Matt-man]

Don, nobody is arguing that the OAL gauge and comparator don't work for setting seating depth. I bet most of the guys posting in this thread have them and use them for that.

But you said that the comparator will contact the bullet at the same point as the rifling does. That's just not true. It doesn't have to be true, and the comparator will work just fine.

[Outlaws]

This isn't rocket science, folks. Although maybe it is for some of you. Bullet ogive is bullet ogive, and the combination of using the Stoney Point OAL Guage and a comparator DOES allow you to adjust bullet seating depth so that you are whatever distance you want to be off any rifles leade/throat. Long range tactical and precision shooters use these tools all the time.

yes it does let you seat the bullet an exact distance from the lands, but it doesn't measure the true distance from the bolt face to the lands. (I wish I had phrased my original question that simply.) Thx :D

[steve4102]

Don, I'm sorry you misunderstood my post. I didn't mean that the use of a bullet comparators DIDN"T allow you to adjust the seating depth to get an exact distance you want off any rifles lead/throat. None of us here are saying that bullet comparators do not work. However, they cannot give an exact measurement from bolt face to leade/throat as you stated. For this to be true the comparator would have to be an exact match to you rifle. That is impossible, as all rifles are cut a tiny bit different.
If your Sinclair Comparator measures the exact distance from bolt face to leade/throat, then you just happen to have a comparator that is an exact match for your rifle. This is extremely rare if not unheard of.
The best way for you to check this out is to select a couple of different bullets for the same rifle. Run through the process and see if the the comparator reads EXACTLY the same with each and every bullet.
By the way, if you read the instructions that come with these comparators they clearly state that you must repeat the process each and every time you select a different bullet. Why? Because they will measure differently.
For the sits and giggles of it, I just called Sinclair and asked the tech if my comparator gives the exact bolt face to throat measurement. He kinda laughed and said "No Way, how could it, it is only a comparison tool. You must repeat the process every time you switch bullets". If you gave Sinclair a call maybe they could clarify this for you.

[Bullet]

USSR

steve4102 Quote – “For the sits and giggles of it, I just called Sinclair and asked the tech if my comparator gives the exact bolt face to throat measurement. He kinda laughed and said "No Way, how could it, it is only a comparison tool. You must repeat the process every time you switch bullets". If you gave Sinclair a call maybe they could clarify this for you.”

Or why don't you go to a site with knowledgeable precision shooters such as the http://www.snipershide.com site and ask people who know because people here just don’t seem to be very knowledgeable (yea right).

Oh, and about the Leade. Below is a quote from Fulton Armory -

“The term throat (synonymous with lede, lead, or bullet seat) refers to an area where the lands of the rifling start at the breech end of the barrel - just in front of the "free bore" area. The lands actually start from the same surface plane as the groves, but quickly taper to full height. A measurement from the surface of one land to the opposing land will provide the bore diameter.”

http://www.fulton-armory.com/TEGauge.htm


Here’s another from Lilja Precision Barrels -

“It seemed as though the "best" throat angle, if there is such a thing, would be one that is tangent to the bullet ogive radius at that point on the bullet which would be engraved by the rifling. Put another way, if we opened a pair of calipers to rifle barrel bore diameter (nominally .237" for a 6mm) and slid it along the nose of the bullet until both jaws of the caliper touched the bullet nose, we would have found that point on the ogive where the lands of the barrel would begin contact with the bullet.”

http://www.riflebarrels.com/articles/bullets_ballastics/throat_angles.htm

I believe that the lands start where the leade ends and since the leade is created by removing metal, the bullet cannot touch the leade, the bullet can only touch the lands.

[USSR]

steve,

I never said that using the Stoney Point OAL Gauge and a comparator gives you a single case base to bullet ogive length that is the same for all bullets. Each manufacturers bullet must be measured to determine the case base to bullet ogive length. You will even find variances in bullets of the same weight and manufacturer (especially Sierra), and I measure my Sierra bullets from bullet ogive to bullet base for my 1k loads. Sorry if there is any misunderstanding regarding this post, as we are probably saying the same thing in different words from a different perspective.

Don

[steve4102]

Quote:
the comparator and the rifling are contacting the bullet at different places.


BS. The comparator will contact the bullet ogive at the same point as the bullet will contact the leade.

Don

For this to be true the "Comparator" and the leade/throat must be of the Exact diameter.

[USSR]

Actually, the leade/throat must be cut to the same angle, no doubt to SAAMI specs. Diameters are a constant for any quality barrel. With a .30 caliber, freebore and grove diameter is .308, while bore is .300. From Sinclair's website:

The holes in Sinclair Bullet Comparators are cut with throating reamers to more accurately duplicate the actual throat of the rifle.

I believe the .30-06 calls for a 3 degree leade. I had Jack Krieger cut mine to 1-1/2 degree target dimensions, so in that case, bullet ogive contact would be different between the comparator and the barrel leade. Are we in agreement?

Don