PDA

View Full Version : Bullet tension.



russell m
01-15-2008, 08:36 PM
I resently spoke with Ron Hoen about purchasing some 6ppc brass. When I found out the cost I decided to continue turning my own. I could use the money in other areas & I already had 200 pieces sorted by weight. He told me he cut his to .0086 per side & told me to use a 259 bushing. So I did. Last night I read an old post by Gene Beggs which stated you should be able to push the bullet in the brass with 1 thumb & maybe a little help with the other thumb. On the brass I have turned the neck tension came out to 1.5 thous. If may calculation are correct, but I can not push the bullet in with my thumb. Am I doing something wrong?

russell m

Dave B
01-15-2008, 08:43 PM
Either turn the brass a bit thinner or try a .260 bushing.
The thumb gauge isn't always true. Maybe Ron's thumb is just a little stronger from pushing all those bullets in the necks.
Dave B

russell m
01-15-2008, 09:03 PM
I gues my real question is should the bullets push in that easily?

russell m

Gene Beggs
01-15-2008, 09:42 PM
Russell, establishing correct neck tension is something you learn from experience and it can only be judged by feel. Based on my experiences with a great number of shooters in the tunnel, I would say that most benchrest shooters use too much neck tension.

I use a small Sinclair arbor press and a simple, L.E. Wilson straight-line seater without the micrometer adjustment. Removing the return spring from the arbor press results in a more sensitive feel. I still say that if you cannot seat a bullet with both thumbs on the stem, you are using too much neck tension.

For a tight-neck chamber, I turn the case so a loaded round measures .002 less than neck diameter. For a .262 neck, the loaded round should measure .260, which would require a .258 bushing. Some feel that .001 clearance is adequate in which case the loaded round diameter should be .261 and the correct bushing, .259.

Gene Beggs

BJS6
01-15-2008, 09:44 PM
Depends what shoots best.

I don't have Gene's credentials but here's my thoughts for what they may be worth.

Seating with thumb pressure is a pretty loose fit, unless you mean thumb pressure on the handle of an arbor press or thumb contact while pressing with the arms ?? Thumb strength only would be pretty soft seating.

I use 2 thou seating tension and that is pretty firm but seems to work well.

If you use a combination like a double radius bullet and N133 that likes a lot of land engagement a light seating force probably won't work the best. It is hard to jam the bullet hard against/into the lands if the bullet will slide back in the case with thumb pressure.

Don't fotget that flat base bullets have a pressure ring so the actual seating tension needs to allow for the fattest part of the bullet.

I'd try the 1.5 thou that you have now and then go a half to one thou either side and see what works best.

Bryce

russell m
01-15-2008, 10:08 PM
Thanks Gene & Bryce. I am learning the feel. I will try removing the return spring from my press. I am going to turn 10 cases to give me .0001 tension which should be a .261 loaded round & try the other 15 cases with 0015 tension. I will see what happens. I am using the Barts ultra 68g. I think they are a double radius. I am not sure what the double radius refers to. I will watch for the bullets pushing back into the case. Thanks for the help. russell m.

abintx
01-15-2008, 10:10 PM
Here is what a group of benchrest notables have to say about 6mm PPC neck clearance and tension: http://benchrest.netfirms.com/Neck%20Clearance.htm. This may help.