Proper use of neck expander

[bozo699]

Straight shooter,
If you are repetitive with your process your neck tension will change very little if at all that if you anneal and are repetitive with the rest but I’ll be very interested in your findings on volume, I hope you post that when you have checked it out. Thank you for pointing that out.
Wayne

I agree, the carbon coating works nicely in helping with seating and without any other lube necessary. It has worked great for me in not cleaning the inside of the brass to spic-n-span by just using a vibrator tumbler to clean the outside.

However. . .

As the number of reloads increases so does that carbon layer inside, which changes the interior volume and even the neck tension. I didn't record just what the difference was on my .308 brass after 7 firings (wish I had, and will check it out the next time around). I've been wet tumbling my brass after 7 reloads to get the inside cleaned out so to keep the carbon build up issue to a minimum.

Sharpshooter,
That may be in fact why we see small velocity changes and blame them on temperatures and powder lots!.....if your one of those filthy rl 15 users it would be a awesome test! I love rl15 but WOW!.....
WAYNE

 

[Straightshooter1]

I’ll be very interested in your findings on volume, I hope you post that when you have checked it out. Thank you for pointing that out.
Wayne

I'm going to make it a particular point to experiment and quantify this and see just how much a difference there is. I have a strong feeling the particular powder being used will also be a variable with regards to this. I'll surely post the results once I complete the "experiment".

 

[bozo699]

I'm going to make it a particular point to experiment and quantify this and see just how much a difference there is. I have a strong feeling the particular powder being use will also be a variable with regards to this. I'll surely post the results once I complete the "experiment".

I’ll be looking forward to it.
Wayne

 

[Brians356]

I'm going to make it a particular point to experiment and quantify this and see just how much a difference there is. I have a strong feeling the particular powder being used will also be a variable with regards to this. I'll surely post the results once I complete the "experiment".

My hunch (not observation) is that carbon buildup inside the case body will be difficult to quantify repeatably with case volume measurements, does not continue to build up indefinitely over time, and is minimally significant even at its thickest. Otherwise I have no opinion.
-

 

[Straightshooter1]

My hunch (not observation) is that carbon buildup inside the case body will be difficult to quantify repeatably with case volume measurements, does not continue to build up indefinitely over time, and is minimally significant even at its thickest. Otherwise I have no opinion.
-

I think you're right regarding the difficulty in case volume measurements. So, I wasn't actually thinking of doing that, for that reason. Instead, I'm going to mic the neck thicknesses and even cut a couple cases down near the web to see what the difference might be from bottom to top. I won't be cleaning the inside of necks so as to not remove any build up there, though seating may effect it. After several firings and mic measurements, I'll do a case volume measurement to see if there's any notable volume changes.

 

[Ned Ludd]

I would like to know how you all are using both a full-length bushing sizing die and a neck expander to control neck tension. I tried using them both in the same die and did not have great results. I do anneal every firing, so hopefully the brass will reform to the chamber again without too much loss.

I’d like to set this up in my normal sizing operation on my Dillon. More specifically what would be the best, and most cost effective way to use the expander mandrel in another station on the press? I am using Whidden 6xc dies and expander button kit. Should I just buy another 6xc sizing die and use it to reduce the chance of inducing runout by leaving a few thousandths clearance close to the bushing? Or would I be ok using perhaps a .308 die if the decapping stem and button fit?

My experience is that trying to both size down and open up the necks in a single step is probably not the best approach. I have used a Sinclair Gen II die with a carbide neck-turning mandrel (0.002" under bullet diameter) with Lapua brass to do exactly what you're describing:

https://www.sinclairintl.com/reload...ls/generation-ii-expander-dies-prod38807.aspx

https://www.sinclairintl.com/reload...els/carbide-expander-mandrels-prod119668.aspx

I first sized the necks down using a FL bushing die with the appropriate bushing. The necks were then opened up in a second step using the mandrel. Because of the direction of the spring-back, a mandrel that is exactly .002" under bullet diameter will actually give you a bit more than .002" neck tension (interference fit)...more like .0025" to .0027" in my hands. However, that can be controlled with greater precision by purchasing two or three mandrels in the correct range with successive .0005" diameter increments:

http://www.xxicsi.com/expander-mandrels.html

Ultimately, you have at least a couple points where you can adjust and control the process. First, you have the choice of the bushing used to size down the necks. I have used bushings that were .001" and .002" smaller than would normally give me .002" interference fit for a seated bullet when used in an FL bushing die as the sole means of sizing the necks. In my hands, a bushing that was .001" smaller than I would normally use in an FL bushing die for .002" neck tension sized the necks down sufficiently that a mandrel of .002" under bullet diameter was able to uniformly and reproducibly open the sized necks back up. Using a bushing that was .001" smaller also worked the brass a bit less. Regardless, it is a point in the procedure at which you can experiment a bit to determine what works best in your hands. Second, you can control the final neck tension/interference fit if you have two or three mandrels (or more) in the appropriate range in successive .0005" diameter increments, as I mentioned above.

The neck wall thickness of various different brands of brass and/or neck-turned cases likely warrants some experimentation with a few different bushing sizes and mandrel diameters in order to optimize the process for your specific brass preps. Fortunately, the cost of a few mandrels plus a die (if you don't already have one), as well as a few bushings, isn't insanely expensive in the grand scheme of things.

 

[kvd]

I am using a .268 neck bushing and a .241 button.

Check my math but if you are using a 0.268 inch neck bushing and have say 0.010 inch neck walls on the case then the final inside diameter of the case neck would be 0.248 inch. In this instance, a 0.241 inch button would not touch the neck walls. Looked at another way, the neck walls of your case would need to be at least 0.0135 inch for a 0.241 inch button to make initial contact with the case neck.

Are you turning the case necks and if so, to what thickness?

It all must work in harmony. Calculate so that the neck bushing will close the inside diameter down 1 or 2 thousandths smaller than the expander button or mandrel.

 

[Dave Marshall]

Check my math but if you are using a 0.268 inch neck bushing and have say 0.010 inch neck walls on the case then the final inside diameter of the case neck would be 0.248 inch. In this instance, a 0.241 inch button would not touch the neck walls. Looked at another way, the neck walls of your case would need to be at least 0.0135 inch for a 0.241 inch button to make initial contact with the case neck.

Are you turning the case necks and if so, to what thickness?

It all must work in harmony. Calculate so that the neck bushing will close the inside diameter down 1 or 2 thousandths smaller than the expander button or mandrel.

The case necks measure .013.

.241 + .013 + .013 = .267. .001 of neck tension.

 

[kvd]

The case necks measure .013.

.241 + .013 + .013 = .267. .001 of neck tension.

That should work. To ensure that the expander button has something to push out it might be good to go to a 0.267 or 0.266 neck bushing.

I do not know what your chamber neck is but for my 6mm BR with a 0.268 chamber neck and I use a 0.258 neck bushing and then a 0.241 expander mandrel to arrive at 0.002 neck grip. This is with 0.010 neck walls.

 

[K22]

Carbon is your friend not your enemy it’s a natural lube left behind!......Take a nylon brush and lightly scrub the neck,I call it burnishing the necks. I alway use the exact number of passes on each piece of brass, if your using a arbor press it will tell you when you have brushed them the right amount. Bullets seat like butter.
Wayne

I do use an RCBS nylon brush.

 

[Joe Maisto]

Carbon is your friend not your enemy it’s a natural lube left behind!......Take a nylon brush and lightly scrub the neck,I call it burnishing the necks. I alway use the exact number of passes on each piece of brass, if your using a arbor press it will tell you when you have brushed them the right amount. Bullets seat like butter.
Wayne

On the other hand...some of us BR shooters enjoy carbon in the necks. Makes for a bit more neck tension on the bullet. I prefer that to a degree. I see some using a bronze brush spinning in a drill for inside neck cleaning, and these are people Loading "on the job" ( as we do) shooting BR "group shooting...To each his or her own. You do what ever your target indicates a change somewhere along the way ....is in order.

 

[dgeesaman]

On the other hand...some of us BR shooters enjoy carbon in the necks. Makes for a bit more neck tension on the bullet. I prefer that to a degree. I see some using a bronze brush spinning in a drill for inside neck cleaning, and these are people Loading "on the job" ( as we do) shooting BR "group shooting...To each his or her own. You do what ever your target indicates a change somewhere along the way ....is in order.

I bronze brush my brass neck IDs by hand because the nylon brush doesn't remove anything at all. A few twists with a bronze brush leaves me with darkened brass. No evidence of carbon buildup or wear on the brass. I know most folks do something less aggressive, although I'd argue pin tumbling is far more aggressive.

To make up for the possible issues with freshly brushed brass, I use dry neck lube on my bullets. If I used an expander first, then I put dry neck lube on the brass necks (inside and out) and don't need to re-apply when I seat the bullets.

I agree you should consider sizing the necks a little more in order to have something to expand. I expand the bare minimum to overcome the springback. Conservatively, the brass springs back a full .001". So you'd want to size the brass down to .2405 ID and expand with a .2420 or .2425 mandrel to get a .2415 final neck ID.

I think the .001 springback is a bit conservative but it's not excessive. I expand with a .2415 mandrel and get a .241 ID with .012" neck. I think my springback is closer to .0005" because I anneal frequently.

David

 

[Straightshooter1]

I’ll be looking forward to it.
Wayne

OK. Now that a local range has opened up I was able to compete the little experiment that I started back in February to try and quantify as well as I can with the tools I have the carbon build up inside the case and neck.

So. . .I took 5 .308 Federal cases that I have and marked each one with a center punch so that I could identify which one was which. The necks on the cases had been turned to a setting at .0125, but measured from .0125 - .0127. As per the plan I shot the 5 cases 7 times and took measurements of the neck thickness's after each firing, while only cleaning the outside of the cases (mostly around the neck to remove carbon). I performed 4 measurements on each neck each time with the first measurement at a specific starting point and then rotating 90° for the next measurement. Then I proceeded to neck size the cases with a Lee Collet Die, bumping the shoulders and 3-way trimming to length. After the final firing, the cases were carefully weighed on my GemPro 250 that gives me +/- .002 resolution but just recorded to the .0. Then I wet tumbled the cases and got them about as clean as I feel possible and weighed them again to see what difference there might be.

Results were interesting and even surprising to me. I didn't expect to see the neck thicknesses reduce after each firing. While they started out .0125 - .0127, then progressively reducing to the final measurements on all cases was .0120 - .0121, (yes, that's with the carbon coating still there and barely a difference after cleaning). I really don't think it was my measuring tool as I checked its calibration as I went along. It might have something to do with the neck sizing with a collet and bullet seating???

The weighing at the end apparently support my hypothesis that there's enough carbon build up to reduce case volume to a measurable point. When I weighed the cases with the 7 firings of carbon inside and then weighted them after a thorough cleaning, there was a .3 gr difference in the weight of each case. All cases had .3 gr difference.

Well, I guess the question now is, is .3 gr of case weight (if there's enough correlation with case volume) of any significance to be concerned with?




Below is inside at the case head.

Below is inside the neck

 

[Webster]

I would like to know how you all are using both a full-length bushing sizing die and a neck expander to control neck tension. I tried using them both in the same die and did not have great results. I do anneal every firing, so hopefully the brass will reform to the chamber again without too much loss.

I’d like to set this up in my normal sizing operation on my Dillon. More specifically what would be the best, and most cost effective way to use the expander mandrel in another station on the press? I am using Whidden 6xc dies and expander button kit. Should I just buy another 6xc sizing die and use it to reduce the chance of inducing runout by leaving a few thousandths clearance close to the bushing? Or would I be ok using perhaps a .308 die if the decapping stem and button fit?

Never used an expander. If your using the proper size bushing what purpose does an expander do?

 

[BenPerfected]

It cleans out the donut

 

[Dave Marshall]

The expander would push the donut to the outside where you could remove it by neck turning. Or you could inside ream the neck to remove it (preferred).

The expander mandrel alone does not “remove” the donut. If the brass that makes the dount is pushed to the outside it will act as a false shoulder and cause headspace problems.