Case prepping for the .280 AI

[Alibiiv]

I've been reloading and shooting for many years. I did not realize how precise and technical that reloading could get until I started reading this forum. In the past it has always been full-length resize, trim to length, primer, powder, seat the bullet and go to the range! I've addressed the "fire forming" or "hydro-forming" .280 AI brass from .280 Remington brass, now on to the next question. I want my brass to be as precise as I can possibly make it before I seat the bullet. From what I have read, cases are reamed to get rid of the doughnut on the inside of the case neck where the shoulder meets the neck on the inside of the case, "prior to being resized"? I am curious that "after resizing the case", if I can ream the inside neck diameter so that it will have the exact squeeze or tension on the bullet when it is seated "and" remove the doughnut at the same time. And if that is the case, what is the normal amount of squeeze/tension that is recommended on the bullet; I believe that I have read .002-003 thousandths squeeze? From the various suppliers I can get just about any size reamer that I would like While I am at it when/where in the process is recommended to turn the case necks? I have a Forster Classic case trimmer, however have not eliminated picking up a Sinclair or K&M case neck trimmer. With this question another question arises and that is the .280 AI is a SAAMI with the 40 degree shoulder, and all of the trimmers that I have read about have a 30 degree cutting edge on them. Do I have to order a case neck turner with a different angle on the cutting edge to match the 40 degree angle on the case shoulder? Figured that I would throw this question in and save from creating another thread. Hope all of the questions posted here make sense. and that I am on the right track here? Thank you in advance for any replies that anyone shares with me, very much appreciated.

 

[dok7mm]

Good cartridge choice. Let's address the donut first. I have had them show up on the 280 ai, you may or may not have that problem, down the line. The primary cause, in my opinion, is dependent on your chamber size and the internal measurements of your die. A tight die and fat chamber will move the shoulder thickness into the neck after 2-3 resizes. I used a set of pin gauges to find the donut and a K&M reamer to remove it from fired cases. I skim turned necks and went a good bit into the shoulder with a 20* cutter angle. Have had no reoccurrence.

If you turn the neck and into the shoulder, along with a good die, you should avoid the donut ever forming. As for neck tension, my go-to method is resizing with a full length die with no expander ball. It sizes the entire neck down enough that when I run a .002" expander mandrel, to set my neck tension, it gives me a far better and more consistent grip on the bullet with low ES vs setting tension w/bushings.

On several 40* shoulder cartridges, I use only the 20* or 30* angle cutters, as I have noticed it often takes 2-3 firings before, if ever, the 40* cutter will match you actual shoulder.

I wouldn't fret too much over problems you don't have yet. I would take good measurements of your new brass vs fired brass vs resized brass. Particularly diameter at shoulder and web, to see what your chamber size is vs your resized brass. Good luck with your new rifle.

 

[Alibiiv]

Good cartridge choice. Let's address the donut first. I have had them show up on the 280 ai, you may or may not have that problem, down the line. The primary cause, in my opinion, is dependent on your chamber size and the internal measurements of your die. A tight die and fat chamber will move the shoulder thickness into the neck after 2-3 resizes. I used a set of pin gauges to find the donut and a K&M reamer to remove it from fired cases. I skim turned necks and went a good bit into the shoulder with a 20* cutter angle. Have had no reoccurrence.

If you turn the neck and into the shoulder, along with a good die, you should avoid the donut ever forming. As for neck tension, my go-to method is resizing with a full length die with no expander ball. It sizes the entire neck down enough that when I run a .002" expander mandrel, to set my neck tension, it gives me a far better and more consistent grip on the bullet with low ES vs setting tension w/bushings.

On several 40* shoulder cartridges, I use only the 20* or 30* angle cutters, as I have noticed it often takes 2-3 firings before, if ever, the 40* cutter will match you actual shoulder.

I wouldn't fret too much over problems you don't have yet. I would take good measurements of your new brass vs fired brass vs resized brass. Particularly diameter at shoulder and web, to see what your chamber size is vs your resized brass. Good luck with your new rifle.

In reference to, "As for neck tension, my go-to method is resizing with a full length die with no expander ball. It sizes the entire neck down enough that when I run a .002" expander mandrel, to set my neck tension", once you have reached this stage of the process, would it be possible to ream the case neck as this time? My thoughts are that a reamer ought to give a more reliable sizing than relying on a mandrel to get the correct inside diameter. If you do find a doughnut on the inside of the case, using a pin gauge, do you measure and ream the case (if you find one) prior to resizing the case or after? Please remember I am new to all of this. I am new to all of this stuff and do not know the exact process. I feel that once I have the process down the rest will all be easy. Do you know if there is a book out there that I can read. My loading manuals to not have any of this information in them, and.....I have a number of them. I am a firm believer that knowledge is power. Thanks for your help with this.

 

[dok7mm]

The mandrel will push variances to the outside of the neck, then you can turn the outside to a consistent neck thickness. I don't ream inside unless I have a pronounced donut that the mandrel doesn't push outside.

Reaming inside can damage the I.D. surface, causing real tension variance.
I don't understand your wanting to fix problems, that you don't yet have.

 

[Alibiiv]

The mandrel will push variances to the outside of the neck, then you can turn the outside to a consistent neck thickness. I don't ream inside unless I have a pronounced donut that the mandrel doesn't push outside.

Reaming inside can damage the I.D. surface, causing real tension variance.
I don't understand your wanting to fix problems, that you don't yet have.

Yup I got it, I completely understand about the mandrel pushing the inconsistencies to the outside of the case and then the outside of the next gets brought back into tolerances by turning the outside of the next. What is your opinion on neck turners, Sinclair or K&M, I'd like to find one that I can use on a power drill instead of by hand. I "think" that on the K&M that the handle can be removed and whatever is inside of the handle can be attached into the chuck of a drill. Even if it threaded, I can make a threaded part to screw onto that piece so it can be placed into a chuck. Sinclair looks like it is all molded as one piece. I looked at some of the lathes that are made for turning case, but....... $500-700 is a little over budget for me. Do you know of any manuals that might have all of this information consolidated in one place? Thanks again for all of your input.

 

[dok7mm]

I have tried several brands, but I like the K&M units best. Look at their Ergo holder, very comfortable and acts as heat shrink. They have a case driver that fits most drills.

 

[TOM H]

Yup I got it, I completely understand about the mandrel pushing the inconsistencies to the outside of the case and then the outside of the next gets brought back into tolerances by turning the outside of the next. What is your opinion on neck turners, Sinclair or K&M, I'd like to find one that I can use on a power drill instead of by hand. I "think" that on the K&M that the handle can be removed and whatever is inside of the handle can be attached into the chuck of a drill. Even if it threaded, I can make a threaded part to screw onto that piece so it can be placed into a chuck. Sinclair looks like it is all molded as one piece. I looked at some of the lathes that are made for turning case, but....... $500-700 is a little over budget for me. Do you know of any manuals that might have all of this information consolidated in one place? Thanks again for all of your input.

Don't mind me saying this. If you get Sinclair neck turner you need to buy their expander mandrel and that's .001" under bullet dia and their turning mandrel is .002" under bullet dia. If you get K&M you have to buy their expander and turning mandrel.

When I first started messing around doing neck I had Forester trimmer and got outside neck turner and had inside reamers for donut. I got another trimmer for inside reamer so didn't have to take tuner off and used feeler gauge to set neck thickness. I still use it every so often.

I had 280AI build before Spec 280AI and I also have spec 280AI and I use Nosler 280AI for that. I've got Sinclair 1000 & K&M. The Sinclair 1000 has cutter for 40 degree shoulder and I have few other AI's so 1000 is only used for those.

Well good luck

 

[dok7mm]

Alibiiv,
If you Google German Salazar/neck turning there was an excellent article, he wrote. It covers tools, procedures and measurements.

 

[Alibiiv]

Alibiiv,
If you Google German Salazar/neck turning there was an excellent article, he wrote. It covers tools, procedures and measurements.

Thank you very much, I'll look it up and read the article.