429421 square vs round lube groove?

[arlon]

I'm guessing the newer molds are round and the older square. Is there any real difference in how they perform? One any better than the other?


Never mind, after some searching I found an old post with the same exact question. I guess the answer is no with a few minor "buts..". (-:}

[nvbirdman]

I believe Elmer Keith designed the 429421 with square grooves to hold more lube, but I think lubes have been improved enough that we don't need that little bit more now.

[Guesser]

I have and use both, today there is no practical difference in my use and application. If I sold, I would sell the round groove mould first.....just cuz!!

[waco]

My 4 cavity Lyman is a square groove. It works well. I have heard some guys complain that a square groove tends to hang up more as opposed to a rounded groove. YMMV.

[Forrest r]

The real difference is in the bullet base compression. An arch is stronger than a right angle. Several years ago a member on this website pm'd this photo to me. We were discussing this very topic.
https://i.imgur.com/M8QJ3DM.jpg

If you look at the recovered bullets in the picture above you can see the compression of the lube groove, round left/square right.

The watered down version:
You hit the loud button and "BANG", the bullet's off to the races. Pressure is exerted on the base of the bullet along with some of the hot gasses get past the base as it expands. The base not only expands, the bullet compresses pushing the lube in the lube groove outward and forward hydraulically. The hot gasses that got by the base of the bullet before it could seal the bore also acted on the lube in the lube groove pressurizing the lube cavity. The outward pressure coated the bore and sealed it for the base/bottom drive band. The forward movement of the lube sealed the bore/front drive band contact points along with getting in front of the lead drive bands coating the bbl.

It used to be that you got the right combo of alloy/bullet fit/pressure (load)/lube and you'd have an accurate load. Why do you think so many people used the same bullseye loads? Heck, accuracy used to go south with the h&g #50 148gr wc's for the 38spl when all 3 lube grooves were filled. Fill the bottom 2 and you got bugholes, fill all 3 you got 9's in the mix.

Personally I used to use square grease groove 429421/422's for light loads/soft alloys and round lube grooved 429421's for hot mag loads.

Enter powder coating:
Pc'd bullets take the right lube/alloy/pressure out of play. The coated bullets have their lube everywhere it needs to be. Pc also tends to be more forgiving when it comes to alloys. With pc I run soft alloys in loads I never would of using traditional lubes.

Anyway the round vs square lube groove has to do with pressures/compression. Cast a bunch of both round/square lube grooved bullets from the same soft alloy. Lube/size them the same and do ladder tests with several different powders. You will clearly see a pattern emerge. Back in the day when I did a lot of high-tech reloading I used range scrap for alloy and either air cooled (9bhn) or water dropped (13bhn). I'd cast square 429421's and air cool them for the 44spl's and water drop the round 429421 for the hot 44mags.

[arlon]

Forrest, thanks for going into that detail. Read a bit of that in the other post I mentioned but not nearly in that much detail. I do appreciate the effort. I had a few 44 mags (629s) and decided I really preferred the .41 and traded all of them off. I had my .44 dies and moulds on the bench to list for sale. Saturday I was at a little LGS and a guy walked in with a S&W 24-3 4". He traded it for a deer rifle and 10 minutes later the store made $200 and I walked out with the S&W. Now, it looks like I might be back into the .44 business. I really like this one... Might try the square one first with some plinking loads in the special (have both).

[Bigslug]

An extra tidbit to throw out in addition to Forrest's post: It's worth noting that Elmer was working primarily with 16/1 lead/tin which might be a bit more "plastic" than our antimony-heavy mixes. I'm not sure how this would play into the lube-pumping equations he mentions.

Also worth noting would be the REST of the dimensions on the mold, as Lyman messing around with grooves, band lengths, and diameters was the reason for Elmer packing up his toys and going to Hensley & Gibbs. An HG-503 IS the Keith .44 design; an Ideal/Lyman 429421 MIGHT be the Keith .44 design.

[Shuz]

I've been casting and shooting for the .44 mag for 55 years now. During that time I've owned many different versions of the "Keith bullet". I've never been able to tell any appreciable difference between any of them on a target or game animal.