Brass problem 6ppc

B

bluechip

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I just neck turned a box of 220 Russian Lapua brass for a .262 tight neck chamber. The wall of the case is .009 resulting in a .261 loaded case. Even though the case has a generous chamfer, after loading a bullet, the case is slightly 'bell mouthed' for maybe .025 at the end, miking out at .262-.263 at the very end, making the case slightly larger than the neck chamber. It only takes about thirty seconds with a small jeweler's file to fix the problem, but I'm hoping someone has a better fix.
 
Did you chamfer after neck turning? If so, I wonder if the chamfering process pushed the neck out at the mouth. Running the case through a neck-sizing bushing should solve the problem. It would be good to measure the thickness of the neck at several points to make sure it is not thicker at the mouth. And reevaluate your chamfering method. Maybe you are using excessive force or using a dull tool. Do the outside deburring after the inside chamfer.

Hope this helps,
Keith
 
mks said:
Did you chamfer after neck turning? If so, I wonder if the chamfering process pushed the neck out at the mouth. Running the case through a neck-sizing bushing should solve the problem. It would be good to measure the thickness of the neck at several points to make sure it is not thicker at the mouth. And reevaluate your chamfering method. Maybe you are using excessive force or using a dull tool. Do the outside deburring after the inside chamfer.

Hope this helps,
Keith
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The cases measure perfectly straight right up to the end before loading a bullet. I tried a heavy chamfer and a light one with the problem not going away. At what point are you suggesting running the case through a neck sizing bushing? If it is before seating a bullet, I did that. Possibly running a loaded case through a .261 neck size bushing may work, but I am reluctant to try it.
 
Silly question, did you deburr INSIDEand OUTSIDE
when you finished turning the necks ??
 
What does the neck look like with a seated bullet? Is the seating die crushing the neck?
 
bluechip said:
I just neck turned a box of 220 Russian Lapua brass for a .262 tight neck chamber. The wall of the case is .009 resulting in a .261 loaded case. Even though the case has a generous chamfer, after loading a bullet, the case is slightly 'bell mouthed' for maybe .025 at the end, miking out at .262-.263 at the very end, making the case slightly larger than the neck chamber. It only takes about thirty seconds with a small jeweler's file to fix the problem, but I'm hoping someone has a better fix.
Click to expand...

I'm not sure if this is a fix, but .009 is too thick. I don't know of any top shooters that use .001 neck clearance and several have posted detailed explanations of how they improved their scores by turning necks just slightly thinner. I wouldn't use more than .0086.

I have seen new cases "bell slightly at the mouth most often after necking down instead of necking up. They usually straighten up after the first firing.
 
What size bushing are you sizing the necks with? What I don't understand at all is that you can fix it with a jeweler's file. Does the file fix it for good or does it happen the next time as well? What I'm asking here is if you file the neck, pull the bullet and do it all over again (do it all)...does the problem remain or is it gone?

Look at your neck tension (sizing bushing) and evaluate if you're sizing too much...try some larger bushings if you have any.
 
Do you have a good 1" mic that reads to .0001? The reason that I ask is that your loaded round diameter is probably larger than you think. All of the custom bullets that I have tried in my 6PPC (all FB) have pressure rings. As an example, I just measured an old production Bart's 66 gr. Ultra that has a shank diameter of .2432 and a pressure ring diameter of .2436. Recently there has been quite a bit said and written to the effect that loaded round clearances (for a typical 6PPC) between .002 and .003 give a more consistent bullet release, and for that reason, better results that become more easily seen at 200 yd. I currently turn my necks to .0081 for my .262 chambers, and as long as the whole batch was the same .0079 would be just fine (IMO).
 
Boyd Allen said:
Do you have a good 1" mic that reads to .0001? The reason that I ask is that your loaded round diameter is probably larger than you think. All of the custom bullets that I have tried in my 6PPC (all FB) have pressure rings. As an example, I just measured an old production Bart's 66 gr. Ultra that has a shank diameter of .2432 and a pressure ring diameter of .2436. Recently there has been quite a bit said and written to the effect that loaded round clearances (for a typical 6PPC) between .002 and .003 give a more consistent bullet release, and for that reason, better results that become more easily seen at 200 yd. I currently turn my necks to .0081 for my .262 chambers, and as long as the whole batch was the same .0079 would be just fine (IMO).
Click to expand...

+1 with Boyd.....
I would like to see if ur brass will chamber with out a bullet...
 
Brass

bluechip said:
The cases measure perfectly straight right up to the end before loading a bullet. I tried a heavy chamfer and a light one with the problem not going away. At what point are you suggesting running the case through a neck sizing bushing? If it is before seating a bullet, I did that. Possibly running a loaded case through a .261 neck size bushing may work, but I am reluctant to try it.
Click to expand...


"The cases measure perfectly straight,right up to the end before loading a bullet"

Makes me wonder if it might be the seater. What kind of seater Die are you using? Could the seater die be causing the brass to bell at the mouth? maybe Change to a different seater. or different style seater. Readjust seater.

It seems Something is occurring during the seating phase to cause the Bell shape.



Glenn
 
I'll take the suggestion to increase the neck clearance a bit and also report back the results on the second firing to see if this is just a first time loading issue. Fwiw, the cases do easily chamber before loading a bullet.
 
flat based bullet, sitting on the flat of the brass neck, just push down and it bells till
the bullet enters.

more chamfer on the inside of the neck.
 
The problem goes away after the first fireforming shot so it looks like a one time problem, but I still find it odd that I alone had this problem. The next time any of you reloads a virgin neck turned brass, load a bullet and mike the very end and I'm thinking you will see a .001-.002 larger diameter on the last .015-.025 of the brass.
 
Brass problems 6ppc

goes away after firing?

Fat bullets at the base?

Try a few boat tail bullets to see whats happening.
 
Brass

One of the benefits of fire forming. If loaded round chambers easily,Stop measuring the end of the necks,prior to fire forming.


Glenn
 
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