another 30-30 question

[papazip]

I've been loading 30 gr. of IMR 4320 in my 30-30 for years.My new manual lists 28 gr. as max. Any reason (case life) to back off now?

[Brian Pfleuger]

What is the weight of bullet under which you are loading this 30.0gr? Hodgdon doesn't list a single 4320 load in .30-30 with a max under 30.0gr.

[rodfac]

4320 is a pretty slow powder...I've used 3031 for years at 30.0 gr with good success for accuracy and pressure. 4320 should be safe, but why not try 28 grains...I've always found that a charge a cpl grains shy of max performed better for accuracy and the difference in velocity was negligible. Rod

[papazip]

The weight of the bullet is 170 gr. The powder is Dupont. The data is from Lyman's 49th.

[TimSr]

There is a lot of variation between manuals. I'm curious is your old manual was also a Lyman. Sometimes there are changes in powders that lead to updates, but these are rare. Sometimes there are new isolated circumstances or incidents which cause them to change their data (such as Blue Dot). This is more common. If you are shooting the same loads in the same gun, its unlikely you will experience any problems, but you might want to use extra caution for your first loads with the latest powder lots since the data was collected.

[Unclenick]

Papazip,

Something's fishy with the Lyman data. IMR4320 and IMR3031 have about the same energy content. IMR4320 is the slower burning of the two, yet the data is showing the 28 grains of IMR4320 giving more pressure and velocity than 28.5 grains of IMR3031. That's pretty much violating the laws of physics as near as I can tell.

QuickLOAD thinks the pressure number for 28 grains is about 8,000 psi too high, even though QL comes within 12 fps of the same MV just with its default settings. Hodgdon puts the starting load at 30 grains and the maximum load (170 grain Sierra Flat Point seated to 2.550 COL) at 32.5 grains. Both use Winchester cases, though Hodgdon uses only the WLR primer while Lyman used a CCI 200 primer instead for some of their tests (and don't say which ones), that shouldn't make that large a difference. That said, Hodgdon's data gives 30 grains and 32.5 grains 1976 fps and 2068 fps, respectively and a pressure difference as just 900 CUP. I have trouble believing that, too. Lyman's getting about 69 fps/grain of powder, and Hodgdon is getting about 37 fps/grain. Something's amis there that I can't account for. But in any case, you have an example of a published 30 grain load that's working just fine.

I think part of what we are seeing here is an example of the notoriously squirrely nature of copper crushers, as that is what Lyman and Hodgdon are both relying on for their pressure data. Below is the result SAAMI published for one lot of .30 Carbine reference loads sent to 9 different test facilities for copper crusher tests. Note that the average pressures measured vary over 23%. A similar test (357 Magnum reference ammo this time) done with conformal Piezo transducers got agreement within just over 11%. So the old system just isn't very good on absolute accuracy and I think you're seeing that problem in the data from both Lyman and Hodgdon.

Do you know what velocities you are actually getting? Do you know how to watch for pressure signs? If the former are within reason and the latter are not present, you are good to go.

[papazip]

Yes, TimSr, my old manual was also a Lyman. 45th, I believe.The data calls for a maximum charge of 30.5 gr. I think I will try 28 gr. and see how it groups.

[Brian Pfleuger]

Lyman 45th?

That'd be worth some money.

[papazip]

No, Unclenick, I don't know what velocities I am getting but there have been no signs of excess pressure.

[papazip]

Brian,
I sure hope my Lyman 45th is worth some money! I paid $4.75 for it.

[Brian Pfleuger]

No sir... I mean real money.

An article by Terry Wieland titled The Handloader's Historical Library in the Feb. 2013 Handloader magazine, page 45, reads "I've owned Lyman's 45th since 1975 and paid $7.50 for it then. Since it is now worth $200-$300, conservatively, that's not a bad investment"