Load Data Varying from Manual to Manual

[Xeon64]

I am just curious to yall thoughts as to why load data is varying so much from one manual to the next. I recently loaded some 308 with IMR 4166 and 150gr soft points.

Lee Manual states:
43gr starting and 48gr as Max

Hodgon states:
41.5gr starting and 45.7gr as Max

So if figured Lee data was in the middle of Hodgons for starting so I went with 43grs.

This is the result on my primers. I stopped shooting. Looks like overpressure load to me.

going to pull bullets on loaded ones and step down the load.

This is not the first time I have seen load data vary so much. My 6.5x55, load data is all over the place depending on the manual.

 

[highstandard40]

That cratering at the firing pin strike could have other causes. The rest of the primer is not flattened which could indicate mild pressure. Did you measure case head expansion as compared to a factory load? Was there increased effort for bolt lift?

 

[Bam Bam]

Did you happen to chrono those loads? That info would definitely help figure out if it's too hot a load. Oneday when I get back into reloading I will have to get a chrono.

 

[Xeon64]

That cratering at the firing pin strike could have other causes. The rest of the primer is not flattened which could indicate mild pressure. Did you measure case head expansion as compared to a factory load? Was there increased effort for bolt lift?

I was using an AR10, noticed this round did not eject far as factory ammo and had light recoil. Maybe I am reading this wrong. I was thinking that the round not ejecting far was due to it being hard to extract. But looking at the round I do not see signs of extraction issues. I never though of it being too light of a load.

Factory Case head measures:
0.466

Reload Measures:
0.466

Will note to thay I am using remington 9.5 magnum primer. Why Magnums? It is all I have/could find.

 

[Xeon64]

Did you happen to chrono those loads? That info would definitely help figure out if it's too hot a load. Oneday when I get back into reloading I will have to get a chrono.

No. I left my chrono home like a dummy. I usually have that. Looks Like I may be making another range trip.

 

[Griz375]

As I've always understood it, the various manuals are reporting observed data. The detail used to ist rifle used, barrel length etc etc - pretty much everything except the tester's preference for boxers vs briefs.

Getting back into reloading myself so digging out my old manuals and notes.
I use Lyman and Powder Mfr data balanced w/ what's available from projectile Mfrs but rarely use any other press Mfr data.

It's tedious to be sure but, working those .xls kept me out of my late wife's way.

The current one strongly suggested I get back into so she could shoot more.

Code around here for "give me some space".

 

[twinin]

I was going to ask if it was an AR 10 or not. An easy sign for AR 10 is an ejector swipe on the brass. I can’t see one in the pics but maybe you can see it. If you see one it may be over pressure.

If you don’t see one I think it looks ok as highstandard said

 

[Xeon64]

Not seeing much. Looks normal to me.

 

[twinin]

Yeah it looks ok to me. AR 10s are very gassy and rough on brass. Heavy buffers strong springs and adjustable gas blocks can help

 

[highstandard40]

I was using an AR10, noticed this round did not eject far as factory ammo and had light recoil. Maybe I am reading this wrong. I was thinking that the round not ejecting far was due to it being hard to extract. But looking at the round I do not see signs of extraction issues. I never though of it being too light of a load.

Factory Case head measures:
0.466

Reload Measures:
0.466

Will note to thay I am using remington 9.5 magnum primer. Why Magnums? It is all I have/could find.

Where on the case did you measure the .466"? Was the factory case you measured a once fired factory case? The case head expansion measurement should be made at the point where the case is unsupported by the chamber. This can be seen as a point just ahead of the extractor groove. You should be able to see a slight step there on a fired case. Measure the expanded part.

 

[Xeon64]

Where on the case did you measure the .466"? Was the factory case you measured a once fired factory case? The case head expansion measurement should be made at the point where the case is unsupported by the chamber. This can be seen as a point just ahead of the extractor groove. You should be able to see a slight step there on a fired case. Measure the expanded part.

Measured from right here. Also measure a little further up toward the neck and both cases where .468.

 

[Xeon64]

Well this looks like exactly what my rifle is doing and seems to be common with DPMS ar10s. Upon further inspection I notice that factory remington ammo has cratering as well. I was looking at 7x62x51 Nato that was mixed in my rounds. I suspect the Nato ammo has harder primers which is why there is no cratering on them.

DPMS Gen 2 LH Cratering primers, excessive headspace? - AR15.COM

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[sksshooter]

looks like a light load to me.

 

[highstandard40]

Measured from right here. Also measure a little further up toward the neck and both cases where .468.

View attachment 142635

SAAMI specs on that case is .473" at that point but I've found very few cases that come close to that spec. Just about all ammo manufacturers turn out brass undersize so it will be assured to chamber in any firearm. Where you indicate the .466" measurement is too close to the rim. That's the thickest part of the case and if you get expansion there you'd have to be far over pressured. Move closer to the neck just a bit, maybe 3/16" and find the largest diameter you can measure and compare it to a factory loaded once fired case. Take several different measurement radially around the case at that point and use the largest measurement. If you're the same or less than the factory load it's a safe bet you're not over pressured.