Neck Tension Issue

[rotciv4]

Need some help. I tried looking through the forums but I can't seem to find this issue I am having.

I am reloading some of my once fired 243 Winchester brass (Peterson Brass 3rd Firing) that was annealed using the AMP annealer. After annealing I bump the shoulder back .002 with a full length sizer die (Hornady) that I have taken the stem out of. I then trim them all to the same length, chamfer and debur. Wet tumble/dry. Then I have the porters precision die which allows me to use a .2425 gage pin. My issue and I have noticed this with my reloads is the neck tensions seem to be inconsistent. I seat the bullets using a Hydropress and LE Wilson Arbor Die. Sometimes there will be barely any reading on the gage and then sometimes it will require me to put 60 lbs of pressure to get the bullet seated. I tried also brushing the insides of the necks out with a nylon brush, maybe I need to use a bronze brush? The inconsistencies in the neck tension cause the seating depths to be different anywhere from .001-.005 CBTO variances. If I use a gage pin that is smaller for example .242 or .2415 I start to be unable to seat the bullet with the hydropress because the force to seat the bullet is too great. I don't know what I am doing wrong but my SDs are usually in 10-20 range and I can not get them into the single digits. I also have similar issues with my 308 reloads Lapua or Peterson brass, only difference with that is I am using the LE Wilson Full length sizer with .330 SAC bushing and then expanding with porters precision mandrel (.3075/.307) Sorry I know this is a kind of a loaded question but I was just looking for some direction. Thanks!

 

[Hoot]

While I can't advise you on problems that I also experience, I can say that I don't trim until after running the mandrel through the necks. Right or wrong, I believe that the necks shorten a little after the mandrel job, so I wait until that is behind me before trimming. I do know that adding some form of lube to the inside of the necks has improved the seating force discrepancy.

I'll leave better advice to those who are more experienced.

Hoot

 

[PopCharlie]

Have you checked the thickness of your case neck walls? Inconsistent thickness could cause seating force to vary.

PopCharlie

 

[rwj]

I’m thinking that wet tumbling after chamfering the case mouth is not a good idea, especially if you’re using pins. They will peen the previously chamfered surfaces and the displaced material may interfere with bullet seating creating inconsistent forces and/or CBTO.

Two easy tests; 1) chamfer the case mouths again immediately prior to seating, and 2) use a smaller gauge pin (.2420/.2415) by hand to check for interference prior to seating.

 

[Straightshooter1]

Need some help. I tried looking through the forums but I can't seem to find this issue I am having.

I am reloading some of my once fired 243 Winchester brass (Peterson Brass 3rd Firing) that was annealed using the AMP annealer. After annealing I bump the shoulder back .002 with a full length sizer die (Hornady) that I have taken the stem out of. I then trim them all to the same length, chamfer and debur. Wet tumble/dry. Then I have the porters precision die which allows me to use a .2425 gage pin. My issue and I have noticed this with my reloads is the neck tensions seem to be inconsistent. I seat the bullets using a Hydropress and LE Wilson Arbor Die. Sometimes there will be barely any reading on the gage and then sometimes it will require me to put 60 lbs of pressure to get the bullet seated. I tried also brushing the insides of the necks out with a nylon brush, maybe I need to use a bronze brush? The inconsistencies in the neck tension cause the seating depths to be different anywhere from .001-.005 CBTO variances. If I use a gage pin that is smaller for example .242 or .2415 I start to be unable to seat the bullet with the hydropress because the force to seat the bullet is too great. I don't know what I am doing wrong but my SDs are usually in 10-20 range and I can not get them into the single digits. I also have similar issues with my 308 reloads Lapua or Peterson brass, only difference with that is I am using the LE Wilson Full length sizer with .330 SAC bushing and then expanding with porters precision mandrel (.3075/.307) Sorry I know this is a kind of a loaded question but I was just looking for some direction. Thanks!

When you anneal your brass the your AMP, it leaves an oxidation layer on both the inside and outside of the necks. That you wet tumble (without pins, if I understand correctly) will take care of that oxidation layer on the outside, but not on the inside. The nylon bush won't do the job and a bronze brush may not help much as it can remove too much of the carbon leaving you with a similar problem with the inside of the neck. The necks need some lubrication. Rather then use a brush on the necks, try putting a little lube on the inside (like applying a light coat of Imperial Sizing Wax with a Q-Tip) or whatever lube you might have available. You might test it first on just a few of your cases to see what kind of result you get. But, I'm pretty sure it's a lubrication issue for you.

Any inconsistency for the OD of the neck (often referred to as "neck tension"), is simply variance in neck thickness. Though you should find that Peterson brass tends to be way more consistent than Winchester brass.

 

[Ccrider]

1. Measure the diameter of your necks. If it is not consistent nothing else will be. If it is,
2. Recheck your Aztec setting on your Amp. You may need to move it up some.

If all else fails, separate the bras that seats with the same pressure and shot them together. See if the case that seat more difficult group differently.

Treat/prep each piece of brass exactly the same and you should get consistent es.

 

[Ned Ludd]

When you use a mandrel to expand case necks from the inside as the final neck-sizing step, it is important that the mandrel do some work on every neck, or inconsistency in neck tension (interference fit) may result. You did not mention the diameter of the bushing in your full length sizing die, but it will be critical to select the correct diameter bushing. I typically use a bushing that is ~.001" smaller than I would use if the bushing die were to be the sole neck sizing step.

As an example, if I would use a 0.336" bushing as the sole sizing step for .308 Win [Lapua] cases, I would start with a 0.335" bushing if I planned to do a final sizing step with a mandrel. From years of prepping Lapua .308 Win brass solely with a bushing die, I know that the neck diameter after sizing came out to be exactly 0.336" (average). Seating a bullet would then give me an outside neck diameter of 0.338", or ~.002" neck tension. Currently, I use a 0.335" bushing, followed by a 0.3065" mandrel, which also yields very close to .002" neck tension. It is important to note that bushings marked as having a certain I.D. may not yield neck with that specific O.D.. They can easily vary by .0005" or so in either direction from the stated I.D., sometimes by as much as .001". You need to know what the tools you're working with generate. For example, one of the 0.335" bushings I'm using in a .308 Win sizing die actually yields necks that are consistently 0.3345" O.D. That is ok, it still works just fine in conjunction with the 0.3065" mandrel, but that would not be the case with a bushing labeled 0.335" that produced a neck diameter of 0.336". In that event, the mandrel would be doing little or no work on the necks and the whole process would be undermined.

When you use a mandrel as the final sizing step, spring-back of the brass works in the opposite direction than it does when a bushing squeezes the neck down from the outside. In other words, the neck opens back up ever so slightly after it is withdrawn from a bushing die, whereas it closes back up ever so slightly when a mandrel is withdrawn. For that reason, you need to size the necks down just a bit more with the bushing die prior to using a mandrel to ensure the mandrel will actually do some work on every case neck. In my hands, a mandrel that is .0015" under bullet diameter will yield very close to .002" neck tension.

You mentioned using a 0.2425" mandrel (pin gauge) to open up the necks at the end of your process. That is only .0005" under bullet diameter, which may be part of your problem. I would make a guess that a 0.2415" pin gauge is the one you should be using if you're aiming for about .002" neck tension. I do not know the diameter of your necks after sizing with the bushing die (i.e. I don't know the neck wall thickness of Winchester .243 brass), but for the best results using a mandrel that is ~.0015" under bullet diameter, you want to use a bushing that will generate a neck diameter of about .001" less than it will be after the mandrel step. I cannot say why you are experiencing such extreme seating force and are unable to seat bullets after using a 0.242" or 0.2415" mandrel. That should not be the case and the cause may be at the very heart if the issue you're having. To re-iterate, the bushing selected should leave the neck at somewhere around .003" under bullet diameter prior to the mandrel step. Then, a mandrel that is ~.0015" under bullet diameter will yield ~.002" neck tension. I can imagine if you used a bushing that was much tighter than that, it might cause issues with the mandrel step and subsequent bullet seating.

Finally, this was mentioned above but is worth repeating. It is generally considered good practice to trim/chamfer case necks as the final step in the process. That way, no subsequent action is likely to undo the work that you have already done to trim/chamfer the cases. Anything that causes the cases to bump into one another or get banged around increases the risk of peening or other damage around the case mouth, exactly where you least want it to happen prior to seating bullets.

In your situation, I would suggest carefully measuring everything you can, including bullet diameter, mandrel diameter, and bushing inside diameter. Make sure the dimensions of the tools you're using actually are what they're supposed to be. Then select the appropriate bushing and mandrel for the desired neck tension. Finally, I'd also check carefully that your chamfering tool is actually doing a good job on the case mouths in addition to moving that step to the end of the process. Poor/no chamfer can also cause extreme seating force to be necessary.

 

[JMayo]

Sounds like you have a Neck lube problem to me.

 

[rotciv4]

You all rock! Thank you for all the tips. I’m going to mess around with it this weekend I’ll let you know how I fare. Sorry I was not clear but I am only using Peterson brass for the .243 winchester cartridge. Have you all expirenced lapua like quality with Peterson or is there really no substitute to the blue box ? Maybe I need to replace my Peterson brass with Lapua brass too. After I try the tips I’m going to see.

 

[KMart]

You all rock! Thank you for all the tips. I’m going to mess around with it this weekend I’ll let you know how I fare. Sorry I was not clear but I am only using Peterson brass for the .243 winchester cartridge. Have you all expirenced lapua like quality with Peterson or is there really no substitute to the blue box ? Maybe I need to replace my Peterson brass with Lapua brass too. After I try the tips I’m going to see.

If you get the velocity and accuracy you desire with the Peterson brass, hang with it. In my case, Peterson didn't work for me in 243 or 6 Dasher.
Give your brass a chance before you give up on it. Your rifle is different than mine.

 

[Dave M.]

When you anneal your brass the your AMP, it leaves an oxidation layer on both the inside and outside of the necks. That you wet tumble (without pins, if I understand correctly) will take care of that oxidation layer on the outside, but not on the inside. The nylon bush won't do the job and a bronze brush may not help much as it can remove too much of the carbon leaving you with a similar problem with the inside of the neck. The necks need some lubrication. Rather then use a brush on the necks, try putting a little lube on the inside (like applying a light coat of Imperial Sizing Wax with a Q-Tip) or whatever lube you might have available. You might test it first on just a few of your cases to see what kind of result you get. But, I'm pretty sure it's a lubrication issue for you.

Any inconsistency for the OD of the neck (often referred to as "neck tension"), is simply variance in neck thickness. Though you should find that Peterson brass tends to be way more consistent than Winchester brass.

Peterson brass is extremely soft and tends to mark from extractor or ejector hole much easier than any brass I’ve ever used

 

[Dusty Stevens]

Chamfer the case mouths and size them down one more step before you run the mandrel in. That new bushing die from 21st century that has the different bushings in it would probably fix this and not iron out your inside neck carbon. You would have to have turned necks if you wanted to be dead nutz exactly the same tension