Neck Tension Issue

[fvalmostthere]

So I have been reloading 6gt for about 3 years. The first 2 years I was running Hornady brass with 105 Bergers. I would run them through my Rcbs fl sizer with the bushing and then what I believed to be a .241 mandrel. No issues.

Recently built a new gun and switched to alpha ocd and Berger 109s using the same die set up. Most cases are fine but every once in awhile I will have a bullet that just a little pressure from the calipers will push the bullet into the case. I noticed some brass being left behind on the old mandrel and thought maybe that is pushing the cases out to far so I bought a new .241 mandrel. The mandrel is definitely pushing out the case so I believe the bushing die is sizing it down enough so why is this happening? When I put the bullet in the calipers to measure I do apply a slight amount of pressure but not a lot. My base to ogive for the 109s is 1.9820. Any help would be appreciated.

 

[iceng]

Measure neck thickness on hornady and alpha, report back.

Your proj should be .243", and wall thickness is usually 0.014", plus or minus a bit.

Say your walls are 0.013, and you have to double it, so 0.026", add on the 0.243 bullet and you get 0.269". You want to size about 0.265" which is 0.002" per side, you can do less than this.

Measure your brass, report back.

 

[fvalmostthere]

Right but that is all measured for the bushing and the mandrel pulls it back out to .241. A .241 mandrel should leave .002 neck tension correct? As long as the bushing is going down past that? I will measure to make sure the bushing is working but the mandrel doesn’t just slide in so I feel like it is. I will check just the same.

 

[iceng]

If the bushing is not squeezing it enough to begin with, you are gonna have a bad time mkay.

Measure the neck diameter on fired, unsized brass. Measure brass neck thickness. Tell us bushing size.

I the words of the late and great johnny 5....

 

[Haney]

Try a smaller bushing .It could be as simple as thinner brass .

 

[High Desert duck]

Do you anneal? is this virgin brass? What is the diameter of the neck when sized, when mandrelled, and when loaded. Whose mandrel is it, hwat material is it, what size bushing and what does the actual OD of the mandrel measure?

 

[918v]

If you’re bushing and mandreling then maybe it’s time to jump into hand dies and an arbor press. That way you’ll have a better feel of the seating pressure. Even with a big press you should have been able to feel the bullet pushing down the neck.