Why such a difference in loading manuals?

**mikepro8** · February 3rd, 2010, 10:26 PM

Okay, I am thoroughly confused.

My speer manual lists load data for .30-06 150 gr. FMJ BT using IMR 4895 as minimum load of 45.5 gr. and a maximum load of 49.5 gr.

Hodgdon's (who owns IMR) reloading data website notes that for the same type of bullet, the same type of powder minimum load of 49 gr. and maximum of 53 gr.

What gives??? I am fairly new to reloading... does this sort of thing happen often between loading manuals?

**Philadelphia** · February 4th, 2010, 09:55 PM

Originally Posted by mikepro8

Okay, I am thoroughly confused.

My speer manual lists load data for .30-06 150 gr. FMJ BT using IMR 4895 as minimum load of 45.5 gr. and a maximum load of 49.5 gr.

Hodgdon's (who owns IMR) reloading data website notes that for the same type of bullet, the same type of powder minimum load of 49 gr. and maximum of 53 gr.

What gives??? I am fairly new to reloading... does this sort of thing happen often between loading manuals?

Yes, it happens often. That's why you start low and work up.

My preference is to go with data from the bullet manufacturer if possible but also always look at several other sources and be mindful if the start load you plan to use is on the high end of data from any other source.

Data is different for a number of reasons from the components used, test barrel and action used, method of measuring pressure, powder lot, etc., etc. As unsettling as it seems, when you fire that first round in your particular gun with your particular components, regardless of the data used, it is pretty much an experiment. So, start low and work up . . .

**max384** · February 5th, 2010, 01:39 AM

Philadelphia didn't really leave much for me to say. Excellent reply.

It can be really frustrating sometimes when you run into a situation like this. I also tend to side with the manufacturer's recommendations and start low.

If you don't already have a chronograph, that's definitely a great tool for any handloader. It can tell you right away whether you've got a real hot load or one that is too mild. Also, consistent velocities translate into better accuracy (assuming all else equal).

**762xIan** · February 5th, 2010, 01:41 AM

It is a bit aggravating, I find they mostly err on the side of caution. Especially the Lee manual, of all the loading manuals Lee is usually the lowest for starting loads.

Either way it gets you safely in the ballpark and you work your load from there, I do anyway.

My speer manual lists load data for .30-06 150 gr. FMJ BT using IMR 4895 as minimum load of 45.5 gr. and a maximum load of 49.5 gr.

Hodgdon's (who owns IMR) reloading data website notes that for the same type of bullet, the same type of powder minimum load of 49 gr. and maximum of 53 gr.

Make sure the load data is for IMR-4895 not H-4895....the powders are close but they are different. I have caught myself looking at the 2 powders load data and mixing them up myself. I wish Hodgdon would change the number on or something on one of them.

**max384** · February 5th, 2010, 01:44 AM

Originally Posted by 762xIan

Make sure the load data is for IMR-4895 not H-4895....the powders are close but they are different. I have caught myself looking at the 2 powders load data and mixing them up myself. I wish Hodgdon would change the number on or something on one of them.

Excellent point. I overlooked that thought myself. I'll rep ya once I can. The button says I gotta spread it around first.

**mauser** · February 5th, 2010, 02:22 AM

How old is your Speer manual?
Hodgdon acquired IMR in or around 2003, (if my source of information is correct).
If your Speer manual is that old or older the difference may be in the test procedures, powder formulation, opinion of the engineers doing the testing for the companies or any number of other reasons.
I thought I was going to check my Speer manual for date and data but then I remembered that I lent it out.

**Pizza Bob** · February 5th, 2010, 09:41 AM

I recently participated in a thread, on another forum that tallked about a particular load of Blue Dot powder in the .44 mag with 240 gr. bullets. Another poster pointed out that the current max load for that configuration is 13.7 grs. I stated that I used to use 16.5 grs. and that was within recommendations AT THE TIME IT WAS LOADED.

So after confirming that 16.5 grs (behind a 240 gr Speer JSP) was indeed tha load I used, I started to dig for old loading manuals. What I found was a terrific example of why only CURRENT loading data should be used.

The other poster found a 1983 Hercules manual that stated 16.0 grs was the max load.

I found a 1978 Hercules manual that states 18.5 grs - that's 2.5 gr. difference in only 5 years. I went further and found two old Speer reloading manuals (yeah, yeah, I never throw anything away). A Speer #9 from 1974 that states a max of 15.5 grs. and a Speer #10 from 1979 (my reference for putting together the loads I used) that states a max of 17.2 grs. (I have these three sources saved as .pdf files, if anybody wants to see them just PM me with your e-mail address and I'll send them along.)

Chronologically:
1974 - 15.5 grs (Speer)
1978 - 18.5 grs. (Hercules)
1979 - 17.2 grs. (Speer)
1983 - 16.0 grs (Hercules)
2009 - 13.7 grs. (Unknown)

What's the difference? It could be changes in the powder formulation. There was a change in manufacturers from Hercules to Alliant that may have been a contributing factor. But more likely a difference in testing methods and equipment and our own litigious society. Clear up to Speer #8 the only methods Speer used for determing excessive pressure were: 1) Primer appearance; 2) Ease of extraction; 3) Case head expansion. After that period the use of copper crushers and piezo electric transducers were used. Today, we measure cartridge pressure in PSI (pounds per square inch) as opposed to the earlier measure of CUP (copper units of pressure). And, as stated, probably the largest factor: Lawyers and society's propensity to sue at the drop of a hat. I would bet that the data in Speer #9 was just copied from previous dada with no empirical testing. Speer #10 probably reflects data that was arrived at by their new testing methods. At the time, powder manufacturer's loads, which only stated a generic bullet weight, generally were hotter than the bullet manufacturer's, that were bullet specific.

Just found all this interesting. I'm sure that you can find parallels with other loads, but all of this just points up the fact: USE THE MOST CURRENT LOAD DATA AVAILABLE.

Adios,

Pizza Bob

**sutehk** · February 5th, 2010, 09:50 PM

Two other explanations that I have run into as a fairly new reloader are these as well.

1. I use the Hornady manual and the Hodgdon's online manual. Quite frequently, the Hodgdon's manual will state data specific to the Sierra brand bullets. I've found that some of the bullets between manufacturers differ in physical dimensions while maintaining the same weight and design. This can vary seating depth if bullets are seated by OAL (over-all-length) and cause pressure differences.

2. The Hodgdon's manual usually shows data for a maximum seating depth, in my experience. Other load manuals may show data for lesser seating depths. Here is an example:

Hodgdon's data for the 168 gr. Sierra HPBT .308 Win.
IMR 3031 COL 2.800" 39.0 gr. - 42.0 gr.

Lyman 49th Ed. data for 168 gr. Jacketed HPBT .308 Win.
IMR 3031 COL 2.775" 37.0 gr. - 42.0 gr.

Varying the seating depth can also change pressures hence a variation in the load data.

Chris