BTO sorting diameter question

[Drewel]

What is the correct diameter of the sorting tool that you use when sorting 6 mm BTO?

I have a Hornady , Fosters, and a Sinclair tool. They all have different diameters. I get completely different results. Because they are measuring different spots on the ogive. I will assume that I want use the largest one, the closest one that matches the bullet?

Hopefully that makes sense…

 

[JFrank]

I use a Hornday comparator with a .24 insert to sort 6 mm by BTO, I also sort from base to seater stem using a .17 insert that closely represents the point of contact of my Wilson inline seater.

 

[Gargoyle]

If you are lucky like me you get different BTOs and same OALs...

 

[JFrank]

If you are lucky like me you get different BTOs and same OALs...

That’s tough to do, congrats….

 

[762plinker]

closest to your bbl measurements
at what dia does the bullet contact the lands.
and then try to find a tool that will allow measuring at that dia.

 

[Bill Norris]

I have both the Hornady L & L and the Sinclair inserts and find the Sinclair to be my favorite. The outer edge of the opening that contacts the bullet on the Sinclair measure .235.

 

[wboggs]

I like the sinclair also. The secret is to use the same one each time.

 

[Jeff Porter]

Reality is it doesn’t matter as long as you are consistent. The value you use is with a bullet profile and your tool. It is not meaningful to anyone but you. The relative difference between the touching the lands value and the final seated value ( jump) is meaningful and compares to others, but your BTO number is only valuable to you and your tool.

 

[Bill Norris]

What he said ^^^ agree.

 

[Richard Jones]

So I do this: Hornady comparator modded to accept .500 bushings. For 6mm I use a .237 bushing. Does it make much difference over "just" a comparator? Probably not (see @Jeff Porter post above). Could measurements be shared? Quite possibly. At least they would be very close.

 

[Straightshooter1]

What is the correct diameter of the sorting tool that you use when sorting 6 mm BTO?

I have a Hornady , Fosters, and a Sinclair tool. They all have different diameters. I get completely different results. Because they are measuring different spots on the ogive. I will assume that I want use the largest one, the closest one that matches the bullet?

Hopefully that makes sense…

As mentioned, it doesn't really matter as long as you use the same comparator for your own measurements and don't try to rely in any way on what other's state as their BTO measurements. You don't want to rely on other's BTO measurements for this reason, that there are different diameters between various comparators, even some differences within the same brand. The best answer is to sort with the comparator that you used to find your lands.

I only use a standard comparator to find my starting point from the lands that I want to be and then to monitor the throat erosion. For sorting my bullets, I will used a comparator with a diameter that's the same (or very very close to) as my seating stem contact point in order to get very consistent seating depths when seating my bullets. Depending on the quality of the bullets, there can be a significant variations between where a normal comparator makes contact and where the seating stem makes contact. Because there can be that difference between those two points on the ogive, I just don't like to sort based on the standard BTO measurement.

 

[Gargoyle]

That’s tough to do, congrats….

congrats is hardly in order. Thankfully its loaded for an AR10 with a magazine limitation of 2.810. So as long as the rounds fit the mag I let fly!

 

[Bill Norris]

So I do this: Hornady comparator modded to accept .500 bushings. For 6mm I use a .237 bushing. Does it make much difference over "just" a comparator? Probably not (see @Jeff Porter post above). Could measurements be shared? Quite possibly. At least they would be very close. View attachment 1395763

That is a cool mod Richard.

 

[Drewel]

As mentioned, it doesn't really matter as long as you use the same comparator for your own measurements and don't try to rely in any way on what other's state as their BTO measurements. You don't want to rely on other's BTO measurements for this reason, that there are different diameters between various comparators, even some differences within the same brand. The best answer is to sort with the comparator that you used to find your lands.

I only use a standard comparator to find my starting point from the lands that I want to be and then to monitor the throat erosion. For sorting my bullets, I will used a comparator with a diameter that's the same (or very very close to) as my seating stem contact point in order to get very consistent seating depths when seating my bullets. Depending on the quality of the bullets, there can be a significant variations between where a normal comparator makes contact and where the seating stem makes contact. Because there can be that difference between those two points on the ogive, I just don't like to sort based on the standard BTO measurement.

View attachment 1395765

Thanks guys!!!! This makes sense!!! I have struggled with this for a long time!!! I appreciate your advice!!!

 

[Ned Ludd]

As mentioned, it doesn't really matter as long as you use the same comparator for your own measurements and don't try to rely in any way on what other's state as their BTO measurements. You don't want to rely on other's BTO measurements for this reason, that there are different diameters between various comparators, even some differences within the same brand. The best answer is to sort with the comparator that you used to find your lands.

I only use a standard comparator to find my starting point from the lands that I want to be and then to monitor the throat erosion. For sorting my bullets, I will used a comparator with a diameter that's the same (or very very close to) as my seating stem contact point in order to get very consistent seating depths when seating my bullets. Depending on the quality of the bullets, there can be a significant variations between where a normal comparator makes contact and where the seating stem makes contact. Because there can be that difference between those two points on the ogive, I just don't like to sort based on the standard BTO measurement.

View attachment 1395765

I really like that illustration.