Sized and GC Bullets are Wobbly

[Fire_stick]

Okay, I'm not sure how to search for this. I've been searching and can't find an answer. I must be missing something.

I recenting picked up a used RCBS Luber Sizer. The sizer had a .357 RCBS sizer die in it, and I played around with it and got a feel for how the machine works. But I needed some other sizing dies, so I went shopping. I needed a .358 die. RCBS dies were not in stock, so I ordered the Lyman sizer die. And since I was on the Lyman page, I order several other sizes as well (all Lyman).

Today, I get my new dies. I'm all excited. Ready to size some bullets and seat gas checks. I start with the .358 die. I put the gas check on the bullet, size the bullet; the gas check is seated in the process. Wow! Nice looking bullet! When I place it on the table, I notice something. It's not sitting straight. Actually, it wobbles because the gas check base is rounded. I try another bullet. Same thing. Then I look at the end of the plunger in the Lyman sizer die. The end is concave. No wonder the bases are rounded. I check the RCBS plunger in the original die that came with my machine. It is flat, not concave on the end. Now I'm looking at the other Lyman dies, and all of those plungers are concave! So, I expect the GC's will also be rounded on the bullets I size using the Lyman sizing dies.

I did swap plungers between the RCBS and Lyman sizer die, and now all my CG bases are flat. But what about the other Lyman dies and GC's?

Am I being hypercritical of a rounded GC base? Would this be an issue in actual use? Do all plungers in the Lyman product have concave ends? The new RCBS?

What am I missing?

[bhn22]

Pics please. I'm trying to visualize a rounded bullet base with a gascheck still on it.

[Bullshop]

The ejector pin in the die will have a flat end and a concave end. I use the flat end for gas checks and the concave end for PB boolits.
The concave end gives a better sharper outer edge to the base of a PB boolit.

[phaessler]

The ejector pin in the die will have a flat end and a concave end. I use the flat end for gas checks and the concave end for PB boolits.
The concave end gives a better sharper outer edge to the base of a PB boolit.

This isn't set in stone, as I have and have seen several H&I dies where there is one end concave and the other is fully chamfered about its circumference.
I often consider contacting Buckshot to get new plungers machined, or some of mine modified.

Only time I have had "wobbly", is with Gator Checks. They are formed with a rounded corner and being a stiffer material they round out the bottoms when they are sized to grip the base of the boolit. Hornady or Sierra checks function fine and are square/flat once installed.

No, I haven't tried to anneal the Gator's yet, as this is a condition I do not feel is related to spring back.

The photos show the differences I have been experiencing using the same sizing die, with different checks.
96152 96153

My observations.
Pete

[Dusty Bannister]

Is it possible that the base of the bullet is not flat? Sometimes the sprue nub in the center of the bullet prevents the gas check from being pressed flat on the bullet base. I am also wondering if you are seating the check fully, and then inserting it into the lube/size die and cycling the handle. Some push out rods intentionally are cut concave, or even have a hole drilled to allow for the base defect so that the check is pressed firmly and squarely on the bullet base. A perfectly square bullet base at the muzzle is more important than a lump in the middle of the bullet base.

http://lbtmoulds.com/aboutsizelube.shtml

When you visit this link, you will see the modification to the push out punch is made for a specific purpose as described in the fourth paragraph.

[Fire_stick]

phaessler,

That is exactly what I'm seeing! And I am using Gator gas checks, too! I'm going to try some Hornady's, if I have some.

Also going to reverse the plunger.

Thanks guys! Good info.

[Fire_stick]

Dusty Bannister,

The bullet bases are flat. I do think it is as phaessler pointed out, because that is exactly what I am seeing.

[Fire_stick]

Dusty Bannister,

That was a good read. Thanks for the link!

[phaessler]

Dusty Bannister, good article, definently, however the bullet bases in my case are irrelevant as they all came from the same Ideal mold. Sprues are flush . Have also had it with an NOE boolit, again using the same diameter check.
Big question is the accuracy effect, as the pressure is applied to a uniform square base. And while humped creating the wobbly-base, it can be flattened, with a reliative light hit from a jewelers hammer (dare I say that), therefore what happens at ignition? Are we to assume that the gas checks deforms again to take the base shape of the bullet? I know first hand this happens in larger calibers, as recovered checks show boolit base imprints.
Again just my observations.

[btroj]

Does it matter? If the outside edge is square to the shank the bullet will shoot well.

[Dusty Bannister]

Does it matter? If the outside edge is square to the shank the bullet will shoot well.

And this might be reason enough to have the push out rod machined to have a relief in the center of the rod, and full square contact around the perimeter of the bullet base. If the check slides on easily, it might not be much of an issue. However, if the check is a tight fit, it might not go on square, one edge will be square, the other rounded and tipping at the muzzle could result.

Most would never really notice unless they are shooting paper seriously. I think that this might have been a modification that Robert Stillwell did as an option, when he was enlarging sizer dies some years back.

I always thought that the push out rods in many dies were cut square and flush on one end to form a nice square bullet base. The other end was usually more rounded to fit the lubesizer and center in the bracket on the RCBS or the metal loop on the Lyman 450-4500. I have never intentionally reversed the rod in a sizer die. Damage to the square end could likely score the sizer. Those things are too expensive to be doing that. Dusty

[Fire_stick]

Okay, I'm reading the LBT article again this morning. What I gather is this. The most critical fit is the perimeter of the gas check. If there is a lump in the center of the gas check (either from a "nub" of sprue or the gas check just being rounded after going through the sizer) all is okay as long as we have "perfect concentricity to the bullet body, and perfect squareness around the critical perimeter of the heel."

So one of my questions was, am I being hypercritical? My only experience with sizers has been with Lee sizers. They have a flat face plunger, so I never encountered "wobbly" bullets. But, I might not have been getting an optimum perimeter fit/squareness around the perimeter of the heel. So with this additional knowledge, I'm thinking I was a little too critical. I may actually see better groups from these bullets. Only thing left to do is go shoot some and see.

I appreciate the info and discussion guys.

[btroj]

Always pay attention to what the target says

[Char-Gar]

I am thinking that with about a 99% certainty, this thread is about a non-issue.

[Fire_stick]

I am thinking that with about a 99% certainty, this thread is about a non-issue.

Lol! I hope so. That's part of why I asked.

[Char-Gar]

Always pay attention to what the target says

Yep..what he said.

[phaessler]

Never know though without trying, luckily I have boolit groups which are 99% identical before gas check install to test, when I get time of course.

[Wayne Smith]

Think about what happens when that little light bulb goes off in the other end of the cartridge. I will guarantee you that gc will be flat when that boolit exits the barrel!

[Lead]

Mine do the same thing but accuracy is still good but the center punch is to blame I think.