I ran into something today that I've never experienced in over 30 years reloading rifles of all calibers. I was loading some 100% load dense 375 H&H loads with some newer Hornady New Dimension dies. These dies, unlike my older Hornady dies use a rubber ring lock between the seating die body and the metal lock ring for the seating stem. I guess this ring is to keep the metal lock ring from being over or under tightened. I am a stickler for exact case lengths, meplat trued, etc. This comes from years of target shooting. So all by brass is cutt right to the thousandth and all my bullets (in this case Barnes 270gr TSX's) have been run through a meplat uniforming tool. So they always measure right to the exact thousanth of an inch. Well, i was checking each comppleted load for length and was getting up to .010 variation in COL. After checking everything and still getting this variation, I got to thinking about that rubber ring. Since these loads are full-case charges and in fact have a very light powder compression, I hypothosized that that ring was causing the seating stem to "float" somwhat under this light powder compression so I removed the rubber ring and tightened the locking ring down on top of the dies like the older design. Wholla---they seated right to the exact setting without any variation at all. Problem solved. I loaded the next 50 rounds without as much as .001 variation. Interesting---maybe this should be over on the reloading forum but have any of you guys seen anything like this on diaes with rubber lock ring seals?

Yes, I have seen it. Loading large capacity black powder cases mandates mechanical compression of the powder with a compression die before the bullet is seated. Compression in some loads runs as much as .460 inch, sometimes a bit more. Lee dies use the rubber O ring set up, and have proven to be un reliable in producing ammunition with consistent COAL in these applications. I use dies with the hard mechanical lock, and check every round for bullet run out with a "V" block and dial indicator.

That's what I was wondering. That make sense--Thanks Sharpsguy. These are the first dies I've used with this type of "soft lock" system and in my smokeless loads don't compress loads very often if at all. I too will stay with a mechanical lock in the dies from now on. When I got these dies I kind of thought this was a solution to a non-existing problem.

I see this same problem using my "Forester Ultra Seater" micrometer head seating die.

I am loading 375H&H compressed charges.

I dial in the exact seating depth and the die will not seat the bullet to that depth, it will be off a few thou.

What I have been doing to compensate is to back off the seating depth about .015" seat a bullet in stages. Measure COL, dial in half the needed amount to correctly seat the bullet and re seat again, measure again do the math again dial in more seating depth seat again.....
In the end I am adjusting the die .001"to get the last exact seating depth.

I don't know why the die won't seat to exactly the depth I initially dial in or at least get the exact depth on the second try when you have measured, an now know the exact amount you need to dial in. I suspect it is the coil spring in the die fighting the springiness of the compressed powder charge like the O ring in the Hornady New Dimension dies.

The Forester die was expensive. I bought it to get around bullet seating depth problems I encountered using the LEE 375H&H bullet seater.
That die had a die body that was too short. I had to back the seating stem out so far that it only had a few threads holding the stem in the die. That along with the rubber O ring on the seating stem made it very difficult to set up for exact seating depths.
The seating stem would slowing move after each bullet was seated. I had to duck tape the seating stem to the die body to keep it from moving during the seating operations.

I thought the micrometer adjustment head of the Forester Ultra Seater die would solve the problem but it has it's own quirks I have to deal with.
At least with the graduation marks on the micrometer head I have reference marks to guide me.
The bullet seating operation is slow and tedious but in the end I do get exact seating depth I want.

Sharpsguy:
What brand of seating dies have "the hard mechanical lock"?

I think my Forster die would work perfectly if I was not working with compressed powder charges.

I was thinking of having a machine shop make up a long version of the LEE aluminum seater stem and use it with out the O ring and install a locking ring system like what is used on the die body to press connection. This would form a hard mechanical lock.

I am not certain, but I suspect that it is the trapped air that is between the individual grains of powder that is pushing back. When I compress my powder .385--which is normal for most of my load/bullet combinations--checking the depth of the compressed powder with a depth guage reveals that the height of the powder column stays constant. However, when compression goes above about .425, the column will usually grow, sometimes as much as .020. My solution is to double compress the powder by simply using the compression stroke twice. You can feel the powder give slightly on the second stroke of the handle. It stays put the second time.

greenjoy--My Lyman and RCBS dies both have a hard lock. I prefer the Lyman dies with cast bullets because they have a nose punch with a better internal profile for the softer bullets. They also come with two nose punches, one for a flat nosed bullet, and another that will handle about any round nosed bullet without damage.