Setting neck tension with expander mandrel and bushing die questions

[Justice1327]

In the competition world of benchrest, F-Class and PRS a large percentage of the top 100 shooters use an arbor press with strain gauge to ensure consistent seating pressure. They have found that it DOES directly correlate to consistency of bullet release and greatly reduces ES and SD. ES is the killer for F-Class and PRS and all steps that can help control it are worth it for some competitors. Looking at my dope for my atmospherics, an ES of 30 fps is a difference of 25.35" at 1,000 yards. They are looking for chamberings, loads, loading techniques and equipment that makes single digit ES possible. So, for the right circumstances and the right shooter, an arbor press with a strain gauge for seating is a good choice.

Bob

ETA - Not attacking your post at all. Just adding a different perspective.

Serious question, and maybe I have missed something, but exactly how does measuring the seating force improve the consistency? And, Do the remove the bullets and start over for those rds that fall outside their parameter? Do they then set those aside and use as sighters or blowoff rds?

 

[L.Sherm]

Its about consistent release of the bullet, gripe on the bullet i call it. Some call it interference fit, flyers can result from it

 

[Bobcape]

Serious question, and maybe I have missed something, but exactly how does measuring the seating force improve the consistency? And, Do the remove the bullets and start over for those rds that fall outside their parameter? Do they then set those aside and use as sighters or blowoff rds?

Good question. Essentially, it's a verification of the overall loading process and allows the "out of spec" rounds to be culled. If a guy seats 300 bullets and 5 of them are noticeably out of the average for the other 295 rounds, those would be culled and used for fouling shots. Similar to measuring bullet runout on finished rounds. Most competitors will not try to remove the runout, instead they will cull the bad ones. It's all a game. Some folks really get into the weeds and for them, the minutiae is important.

Bob

 

[dwent1811]

To those using a mandrel and graphite, how are you guys applying the graphite inside the necks with round to round consistency? On a mop, or are you putting it on the mandrel?

Great thread by the way. Just learned a lot.

 

[Justice1327]

If I understand you correctly, I have a small black cup filled with graphite balls. I simply insert the case mouth into the cup two times, wipe off the excess on the outside, and insert the brass into the mandrel die. Attached is what I use.

 

[Justice1327]

Both types must be inserted and removed. There are 3 types of expander buttons. The normal one with a rim, a tapered type and a football shaped one. The advantage of the Sinclair mandrel is that it provides 100% contact of neck and mandrel whereas the other 3 aren't even close to that. The extra step if needed is probably well worth it.

Here are a few different expanders I found when looking through my die sets which are mostly Redding and a couple RCBS.

From Left to right. Typical ball style expander. Football or egg shaped expander which is free to float and hopefully stay centered as needed. 3rd is ball type with a long contact surface and last a tapered type. Also pictured is a Sinclair mandrel. The advantage of the Sinclair is that it is always in contact with the neck whereas the other 4 are pushed completely through the case neck and then pulled up back through it

I use Lee dies to some extent. Theirs is essentially a mandrel, but too small and gives ~.007 th neck tension. I use it for lever guns mostly, but I have a few that Lee custom cut that leaves about .003th neck tension.