Updated - Nosler AB and BT size differences – load development and Lee Collet

[RonR]

Updated - Nosler AB and BT size differences – load development and Lee Collet

Have completed load development for two rifles here for hunting season using BT’s and last night was going to load AB’s in place of BT’s for site in this weekend.

It was in my mind that these two would be interchangeable based on the Nosler loading data with the OACL and B.C’s being the same. (I also recall reading some threads on same POI between the two and somehow I translated this as meaning interchangeable.) Not so. The AB’s are a half thou smaller in diameter and .025 longer when measured using a comparator. (Ogive to base of bullet) The AB’s measured were consistent from two separate lots.

Have others measured these differences with these bullets?

This makes me suspicious that the load development completed may not be valid if trying to use AB’s in place of BT’s with these findings. The longer AB's to match the .020 jump we are using would change the internal cartridge volume wouldn’t it? (less volume creating more pressure with same powder charge?)

Have others swapped and continued on? (adjusting for seating depth)

Of note
- Acknowledged that each bullet has its uniqueness and must be fitted to the rifle. In process of determining bullet depth of the AB’s in our rifles but this has really got me really pissed because my Lee collet die just can’t size the neck down sufficiently to grip the AB’s enough to provide consistent results when fitting cartridge with bullet into chamber to determine contact point. I’ve got 70 cartridges sized to fit BT’s with primers ready to go.
- 7mm-08 savage bolt action rifles – Nosler 140 gr BT’s and AB’s
- Sophomore reloader, haven’t had grip issues yet after I figured out the collet die a year ago. Have loaded Sierras and Hornady’s and Nosler BT’s with no issues like this.
- Neck turned cartridges for process repeatability.
- Load development using OCW method
- Even ordered a -.001 diameter from Higginsons that came in at the same diameter as the off the shelf mandrel that came with the die set

I realize a solution is just to use BT’s for hunting and pick this up another time but it was the aim to use Accubonds based on last year’s bullet selection.

Regards
Ron

 

[Ron AKA]

Have completed load development for two rifles here for hunting season using BT’s and last night was going to load AB’s in place of BT’s for site in this weekend.

It was in my mind that these two would be interchangeable based on the Nosler loading data with the OACL and B.C’s being the same. (I also recall reading some threads on same POI between the two and somehow I translated this as meaning interchangeable.) Not so. The AB’s are a half thou smaller in diameter and .025 longer when measured using a comparator. (Ogive to base of bullet) The AB’s measured were consistent from two separate lots.

Have others measured these differences with these bullets?

This makes me suspicious that the load development completed may not be valid if trying to use AB’s in place of BT’s with these findings. The longer AB's to match the .020 jump we are using would change the internal cartridge volume wouldn’t it? (less volume creating more pressure with same powder charge?)

Have others swapped and continued on? (adjusting for seating depth)

Of note
- Acknowledged that each bullet has its uniqueness and must be fitted to the rifle. In process of determining bullet depth of the AB’s in our rifles but this has really got me really pissed because my Lee collet die just can’t size the neck down sufficiently to grip the AB’s enough to provide consistent results when fitting cartridge with bullet into chamber to determine contact point. I’ve got 70 cartridges sized to fit BT’s with primers ready to go.
- 7mm-08 savage bolt action rifles – Nosler 140 gr BT’s and AB’s
- Sophomore reloader, haven’t had grip issues yet after I figured out the collet die a year ago. Have loaded Sierras and Hornady’s and Nosler BT’s with no issues like this.
- Neck turned cartridges for process repeatability.
- Load development using OCW method
- Even ordered a -.001 diameter from Higginsons that came in at the same diameter as the off the shelf mandrel that came with the die set

I realize a solution is just to use BT’s for hunting and pick this up another time but it was the aim to use Accubonds based on last year’s bullet selection.

The unfortunate reality is that there is quite a variation from manufacturer to manufacturer on bullet diameters. I recently measured 7 different types of .264 bullets. Actual measurements varied from 0.2630 (Speer) to 0.2642" (Lapua Scenar). So you kind of have to be prepared for that kind of variation. And on top of that the manufacturer will use sizing dies that wear from new condition until they are finally replaced. The bullets get bigger and bigger from batch to batch. That is why you always load bullets from the same batch if you are going to target shoot. I would think it highly probable that the BT and AB bullets are made in different dies. They may be initially the same when new, but over time...

On your collet die, I think they are a really good idea, but neck turning may be causing some of the reduction in sizing issues. If you have two mandrels you may want to put one in a drill and see if you can bring it down a thou or so with wet/dry sandpaper. One of the reasons some reloaders go to bushing dies is to address these issues.

When Nosler and others do load data, I don't think they even consider distance to the lands. They probably just pick a number based on the SAAMI specifications to ensure it fits the magazine.

 

[savagelh]

Buy a factory crimp die

 

[RonR]

Proper neck tension achieved with taking the mandrel diameter down.

Still would like to know if others have swapped the accubonds for the ballistic tips and kept going with the same load.

Regards
Ron

 

[RonR]

Buy a factory crimp die

Yup, that could be done. For me it would be another step in the process to work out...too much or too little crimp I imagine would have to be figured out. I get the point though, and for hunting it makes sense.

Regards Savagelh
Ron

 

[Ron AKA]

Proper neck tension achieved with taking the mandrel diameter down.

Still would like to know if others have swapped the accubonds for the ballistic tips and kept going with the same load.

Good to hear you solved the neck tension problem. On your bullet dimension interchangeability issue I take each loading as a new batch. Remember over time the distance to the lands in your chamber will change due to neck erosion. I start with a new distance to the lands measurement, but I keep the distance to the lands or jam into the lands constant. I think that is the critical dimension to keep consistent. Yes it will change case volume slightly, but I think that is much less significant. The basic idea of ladder testing is to make your loads tolerant to some velocity variation from shot to shot. However it is also a good idea to check velocity you are getting compared to your target velocity as loads may change over time due to powder batch variation and bullet batch.