I'm using a Stoney Point OAL guage and get a different distance to the lands depending on which bullet I'm using.

When I measure using a 140 Grn Sierra Game King, I get 2.265. When I use a 140 Grn Nosler Accubond, I get 2.300.

Seems to me that since you are measuring from the base of the brass to the point where the side of the bullet makes contact with the lands, the distance to the lands should be the same regardless of which bullet you are using to do the measurement.

Am I wrong on this? Please elplain.

firstshot
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Make your first shot count!

This has all to do with ogives that different brands have, Hornady has the secant ogive, Nosler and Sierra have (help me here) some other type ogive, then again the gameking and accubond have different points on them, which will give you different lengths even with same manufacture. Jay

You aren't doing anything wrong at all. Measure 5 bullets from the same box and you will get 5 different readings. Measure 5 or 10 and use an average. It's not that critical unless you are striving for BR accuracy. It is also a constantly changing dimension as your throat erodes. You will always have different dimensions between manufacturers even if the bullets are the same weight. As Jay points out it's all about the ogive. Jim

quote:

Originally posted by First Shot:

Seems to me that since you are measuring from the base of the brass to the point where the side of the bullet makes contact with the lands, the distance to the lands should be the same regardless of which bullet you are using to do the measurement.

You're right. I don't know this for a fact but I think the hole in the comparator is not as large as the diameter of the bullet. So there is a certain distance between where the ogive actually is and where the smaller diameter hole on the comparator hits the bullet. Different bullets have different slopes between these points A & B, so there is a small difference in the measurements. A 30 caliber comparator hole measure .295 and the bullet measures .308.

It's all used for reference and repeatability anyway so the actual measurements aren't as important as accomplishing the task of seating the bullets with your chosen distance from ogive to lands.


Without guns we are subjects, with guns we are citizens

cae head to ogive should remain constant. If you work from the casehead, that will be in the sam eplace each time. Now, if you change bullet weights/brands/styles etc, and you use the comparator working off the ogive to measure a seated round wich was set to max OAL (at the lands) and you seat the new pill so that the casehead to ogive is the same measurement, then that pill is now equally as far from the lands as the other pill was. This measurement will remain constant until the throat erodes and a new OAL is needed and the new case-head to ogive measurement will increase by the same number of .001"s. That is why you keep the same bullet you used to get your intial measurements in your die box. This bullet will always remain the same length to tip, so your subesuent die settings and throat measurements will be operating off the very same bullet you used intially.

If one type of pill measures lets say 1.500" casehead to ogive, then any substituted pill should measure the same to be the same distance from the lands. No matter the OAL of the loaded round,..that is a function of bearing surface length and nose length as well as the use of a secant ogive.

Now if you really want to drive yourself crazy, get a set of "Head and Shoulders" attachments for your Stoney Point and measure the difference between the modified case and a fired case. That difference for my 300 win mag is .015". Try wrapping your brain around that and allowing for it.

https://forums.accuratereloading.com/eve/forums/a/tpc/f/2511043/m/483105552

Ok guys, I got it.

1. For each type of bullet I'm loading, I can have a different "distance to the lands".

2. Even using different bullets of the same type and lot can result in different "distance to the lands"

3. Measure distance to the lands with 10 different bullets and use the average.

woods
I went an measured the hole in my 7MM comparator and it was slightly smaller than .284

So just to make sure I've got this straight, If I want to seat these bullts 10 thousants off the lands I'll seat the Game Kings to 2.255 and seat the Accubonds to 2.290.

Correct?

firstshot
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Make your first shot count!

The Stoney Point has a hole slighty smaller then the bullet. It is meant to be very close to the bore land measurment not the grove of the bore. The bullet(s) will vary from tip to base in lenght but shouldn`t vary from base to the point on the ogive. This is the critical distance.
When you seat your bullet if you have found the distance off the lands of say .010" is shown as a measurement of 3.20" when useing the tool and bullet "A", the next brand or style "B" of bullet should be the same .010" off if you seat it to the same 3.20" again useing the tool. Don`t worry about base to tip lenght, it means nothing when we use the Stoney Point. Measure the case base to the bullet ogive and shoot for the same lenght in that measurement with all bullet brands and lot#. The only thing COL (case base to tip) lets us know is if our ammo will fit in the magizine of the rifle.

I got it!!!

Thanks to all for your help!!!!!!!!

firstshot
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Make your first shot count!

There are several good measuring toold to find the distance to the lands but for me I have never used nor bought any of them. I seat my bullets against the lands by closing a dummy in the chamber and then measure the full length. then if I want the bullet to be .005 from the land I seat it down another .005. If I want .010 I seat down .010, etc. When I get that certian bullet at its best depth for accruacy then it becomes my pattern. Using another type bullet I do the same thing. Then when I load up say a 174 grain 7.7 .311 diameter match bullet I set my dies firmly to the pattern for that bullet and seat all the rest to it. This has worked well for any kind of bullet that can be loaded close to the lands. For one tha tmust be used in the mag I seat the bullet until it just works well in the mag an dset all to that pattern. Is it as accruate as measuring with a precise insturment? In most cases yes it is because you get 10 different answers from 10 different people using them. Means something is not as solid as it needs to be. The way I do it is good enough to bring the old 7.7 groups down to constant .375 using from the mag which is .085 from the lands. Going to try some match 174 grain hollow point bo tails starting at about .005 from the lands although they can't be used in the mag. Works for me, groups are great and no money spent on expensive tools that most never figure out anyway.

First Shot:

You should also get yourself a bullet comparator; it lets you seat bullets to the correct distance to the lands. You can switch bullets and styles and not have to dick dance with finding the new distance to the lands.

quote:

Originally posted by AnotherAZWriter:
First Shot:

You should also get yourself a bullet comparator; it lets you seat bullets to the correct distance to the lands. You can switch bullets and styles and not have to dick dance with finding the new distance to the lands.

AnotherAZWriter

I am using a bullet comparator to measure the distance to the lands. I first use a Stoney Point AOL guage to seat the bullet touching the lands. Then I use a chronograph with a bullet comparator attached to measure the distance from the base of the cartridge to where the bullet makes contact with the comparator collar.

As I indicated in the first post, this is where I was getting different measurements with two different bullet types.

The problem is, the diameter of the hole in the comparator collar is actually smaller than the ogive diameter. So, I am NOT measuring the distance to the ogive, I'm measuring the distance to where each bullet makes contact with the comparator collar. Because different bullet types have different tapers, you should almost always come up with a different measurement for different bullet types.

At least thats how I curently understand it.

How are you using a bullet comparator so that:
"it lets you seat bullets to the correct distance to the lands. You can switch bullets and styles and not have to dick dance with finding the new distance to the lands."?


firstshot
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Make your first shot count!

You're on the right track. I measure each bullet and remeasure when I have to open a new box. There are 2 fixed points - base of the case, and beginning of lands. What varies is the seating depth of the bullets and the position of the ogive which you set yourself.

There is a lot of confusion on this, mostly terminology. Some reloaders consider the entire curve to be the ogive, Stoney Point defines it as the point where the bullet reaches full diameter. That is the definition I use.

I don't think the Stoney Point is entirely accurate nor the method of using a bullet in a crimped case and chambering against the lands. The Stoney Point uses a modified case which may not have the same dimensions as one of your fire formed cases. When seating a bullet into the lands, they can be pushed in with varying force and cause different measurements.

That's why I don't try to seat too close. Usually I load Barnes Triple Shocks which are recommended to be seated back .05" and haven't had any problems yet.

Hope this helps.


Without guns we are subjects, with guns we are citizens

I use the sinclair comparator because it is made with a "throating reamer" for each caliber it contains (6 calibers in all). This centers exactly on the ogive of each bullet. This will give you a great deal of accuracy once you have used it once or twice. I can set my dies for different bullets in mere minutes using the sinclair comparator.

No matter which bullet you switch to, the ogive will end up at the same distance to the lands as each measurement matches using the comparator.

Instead of using the stoney point modified cases which are undersized factory brass that will fit in any chamber and will give you inaccurate (short) readings for your chamber. I use cases that have been fireformed in my chamber. Deeprime them without resizing, as you want the fired case dimensions to stay the same and match your chamber, drill and tap to accomadate the stony point tool and get a much more accurate measurement for your individual chamber. Much less expensive than buying their cases also.

O M

quote:

Originally posted by Oscar Makonka:

drill and tap to accomadate the stony point tool

I know this was posted not too long ago, but I can't find it. Exactly which tap size do you use to match the Stoney Point?


Without guns we are subjects, with guns we are citizens