huge powder differences for casting 45 acp cartridges

[Plaz]

I am just starting to cast bullets and use them in reloading 45 acp. In comparing the Lyman, Speer and Sierra manuals I find huge differences in the recommended grains of powder for starting loads.

Can someone explain this to me? I am confused and do not know which load to use. The Lyman manual is by far the lowest recommended starting load.

[darkgael]

Some of the difference can be traced to the "test bed" that each company uses for their testing. Lyman uses a device called a universal receiver to gather their data. Speer and Hornady and Sierra use actual pistols (Colt 1911s and the Sig P220). That is at least part of it. Why those methods result in different published data I'll leave to someone else.
Pete

[Jim Watson]

There are several things going on here.
The usual starting load is 90% of the maximum.
Lyman shows much lighter starting loads with cast bullets. To be super safe? To give you a super light plinking load? I don't know, but they do.
You will also notice that Lyman can have two cast bullets of the same or very close weight and very different powder charges. They are seeing the effect of different bearing surface areas and seating depth on chamber pressure.

Speer does not give load data for cast bullets in any recent edition I have seen. They make soft swaged bullets and give data for them. Loads are usually light because they don't want you to drive them to high enough velocity to lead your bore; not because the pressure is maxed out.

I do not see data for lead bullets in Sierra. Jacketed bullet loads are not necessarily usable as is.

[SL1]

There are two things in previous posts that need some clarification or updating.

The easy one first: The newest Speer manual #14 does include some data for hard cast bullets (from RCBS molds) as well as some data for the Speer swaged soft lead bullets in a few cartridges. Powder charges reflect the need to keep the soft bullets to relatively low pressures (and thus velocities) to avoid leading.

Now for the very common misconception expressed in darkgael's post. ALL pressure testing data is now done in special test barrels mounted in "universal receivers" and it has been that way for decades. It HAS to be that way, because the SAAMI standards for pressure limits are for barrels and chambers with SAAMI MINIMUM dimensions. The special test barrels are made to SAAMI minimum dimensions, while commercial guns typically are not, but a few do turn out that way. So, ALL pressure data NEEDS to be produced in the special test barrels to make sure that it produces the highest pressure that MIGHT be encountered in a commercial gun that was made to the minimum dimensions allowed. The difference in manuals that most of us see it that a few of them just report the velocities that they got from the test barrel (which are usually higer than typical commercial guns would produce) while most reshoot the max and start loads through ONE commercially available gun to give a better indication of what velocities YOU can expect from YOUR gun. The misconception comes from what is usually shown in the manual data formats, PLUS the fact that loading manuals from SEVERAL DECADES ago DID use commercially available guns to "work-up" loads while "looking for pressure signs" like they tell us to do. EXCEPT, the folks producing those old manuals did not have a "max load" to keep them out of trouble. So, some old maunals used guns that were substantially larger than SAAMI minimum standards, and then other folks using the loads produced with those guns got into over-pressure conditions when they applied the data to THEIR guns. This is just one more reasonn to check data in old manuals against current manuals before using it. There are a few REALLY over-mx loads out there in manuals as recent as the 1970s.

One more thing to keep in mind is that some manuals list a "max" load that stays below SAAMI pressure specs and then just add a "start" load that is low enough to keep you out of trouble with your first shot (usually 10% reduction from "max" but some powders, like WW-296, are only reduced by 3%). Other manuals list a "max" load and also a "min" load or a range of loads that starts at some low velocity. These min loads are intended to allow you to produce low-velocity loads without getting "squibs" or leaving a bullet stuck in a barrel. Manuals that feature cast bulelts are more likely to show low charges and "min" loads because many folks cast bullets to make cheap plinking loads, and don't want the higher velocities and pressures, but some still do want to drive them as fast as is safe. The min-to-max format is also used by some of the jacketed bullet manufacturers, too. I actually like that best.

SL1

[darkgael]

SL1: Thanks for the clarification. I did not know that about pressure barrel use by all manufacturers. So....when Hornady (for ex) says, under their .45 ACP data, that the firearm was a Colt 1911 Gold Cup, etc., that is just for velocity data; the pressure work was done in another barrel. Is that correct?
Pete

[SL1]

Pete,

Yes, that is correct. Sorry it took me so long to get back to the computer to answer.

SL1