CBTO question

[Deleted member 107666]

Also, You might want to get a reloading book for explanations and loading data. Not saying guys have wrong explanations but each weapon is different even though they have the same chamberings they are like people and will be different. Unless I know the person I will never take another persons word for reloading data but start low and work up on your loads. Just because it's safe in another guys rifle means it is in yours. Get a good reloading book and read and learn the basic steps then progress slowly.

I've read and own the lyman and berger books...this is not explained in those, nor are any of the questions I have asked on this forum. Nor does hornady list a starting weight for 225 eld-m and H1000...i would be thoroughly surprised if anyone would start reloading without at least reading a few of the big books on it. Hate to sound like a jerk, but this post seemed to infer that I know nothing and need to start over. I worked up a .5 moa load with a ES of 9 and SD of 3.5 in my first reloading attempt, but nothing I learned from those books helped with that...this forum and the participants are what helped. Those books are about as novice as it gets and honestly, I'd consider them both a waste of $$.

 

[Lone Hunter]

I've read and own the lyman and berger books...this is not explained in those, nor are any of the questions I have asked on this forum. Nor does hornady list a starting weight for 225 eld-m and H1000...i would be thoroughly surprised if anyone would start reloading without at least reading a few of the big books on it. Hate to sound like a jerk, but this post seemed to infer that I know nothing and need to start over. I worked up a .5 moa load with a ES of 9 and SD of 3.5 in my first reloading attempt, but nothing I learned from those books helped with that...this forum and the participants are what helped. Those books are about as novice as it gets and honestly, I'd consider them both a waste of $$.

Vandy, my post was not meant to sound like you don't know anything about reloading. I'm by far an expert. I do know my way around in reloading. Been reloading since 1970 but that doesn't mean I know everything or anything. As far as the Berger book not explaining this I disagree with you on that. I have seen guys ask for load data(have done this myself and not checked the book)and the INTERNET load was too hot for my rifle. It sounded to me as you wanted someone to throw you a charge out there and you were going to go with it that's why I said work low and start up. As far as a reloading book that is a starting place and not the gospel. Just a good starting point. I've seen guys start right in with max loads but hey it's none of my business. Good Luck to You and Your Loads.

 

[Jeffrey Van Zandt]

https://www.accurateshooter.com/ballistics/tangent-vs-secant-vs-hybrid-ogive-bullets/

 

[338 dude]

I've read and own the lyman and berger books...this is not explained in those, nor are any of the questions I have asked on this forum. Nor does hornady list a starting weight for 225 eld-m and H1000...i would be thoroughly surprised if anyone would start reloading without at least reading a few of the big books on it. Hate to sound like a jerk, but this post seemed to infer that I know nothing and need to start over. I worked up a .5 moa load with a ES of 9 and SD of 3.5 in my first reloading attempt, but nothing I learned from those books helped with that...this forum and the participants are what helped. Those books are about as novice as it gets and honestly, I'd consider them both a waste of $$.

Go to the powder manufacturers website in this case H 1000 and look up bullets of similar design and weight that would be the best place to start

 

[misterc01]

Example: I am using 168 Gr Hornady A-Max, ELD and Sierra Tipped Match Kings.
All three have a different CBTO due to variations is where the Ogive is in relation to rest of the bullet. They each have different measurement from the base to the Ogive, and due to their different shapes, the TMK extends further into the throat than the other two, when ALL are seated at .020 off the lands. You can see the difference when each of the competed rounds is standing on end next to each other. Also illustrates why you DO NOT use COAL for seating. To "prove" it to yourself, use a comparator and simply measure each of the bullets and you will see the differences.

 

[Deleted member 107666]

FWIW fellas...

My CBTO w/Berger 215s was 2.801
My CBTO w/ELD-M 225s was 2.803

Almost not worth the time measuring with the weaver method (using weaver with a marker to visually find the lands)

 

[philipbrousseau]

bolt face to bore diameter of the lands remains the same except for erosion of the lands from shooting. bullet tip in the seating die to bore diameter on the bullet is not the same on different bullets or even bullets in the same box at times. seating depth has to be adjusted to match desired position of bullet in relationship to bore diameter of lands.

 

[dxlbaile]

Just go ahead and line up three different bullets side by side and look at them.. 215 Berger, Nosler , etc... I think if you look closely it will answer your question.. No they are not built the same and wont have the same CBTO.. For example that is the reason I use a 210 Berger in a shorter Savage chamber, because it will fit in the mag box and shoot well vs.. the 215 it is too long.. OGIVE will be different on every bullet. You need to measure on each new one you shoot . Good Luck.

 

[Deleted member 107666]

I understand that the COAL will be longer, but for my purposes of simply seating a bullet .020 off the lands...its the same measurement. Weaver method to find the lands and then a comparator to read CBTO...withing .002 of eachother with 2 dif bullet designs.

Sure the bullets have slightly different ogive shapes and lengths, but that seems irrelevant if not worried about COAL.

back to the original question...would it have been more correct to ask if the distance from the base of cartiage to the lands would be the same given 2 different bullet designs?

The purpose of the question was to see if I could use the same comparator length i had with the berger 215s to set a 225 eld-m bullet the same distance off the lands (.020)...and I guess the answer is yes, at least in the case of these two bullets?

 

[LongBomber]

The issue is that your comparator is not cut the same as your throat/lead in the chamber. It is not the same dia as your land or grove dia. So bullet shape will give a different measurement to be the same distance off the lands.
If you have a smith cut a comparator insert exactly to match your rifles throat/lead then you could do it once.