How Low is Minimum? Manual Disagreement

[Sapper33]

I'm new to reloading, and thus far I've been working out of my Spear manual with good results. But I wound up with a Sierra manual for Christmas, and some excerpts from the Hornady manual.

I've picked up a bunch of Hornady 30cal FMJ's to load. Figured hornady makes good stuff, I need practice ammo for my M14 and R25, and the stuff is "cheap". I'm not looking to build match ammo yet, the guns still shoot better than I do, so I just want to get some good quality rounds down range, so I'm not overly worried about the exact load yet.

I figured originally that a 30cal FMJ is a 30cal FMJ, how much difference could there really be? Here's where I hit the problem, I'm using Varget and H335 for now:

Spear manual 150gr:
Varget: min 43.0gr max 47.0gr(C)
H335: min 43,0gr max 47.0gr(C)

Sierra:
Varget: min 41.4gr max 44.8gr
H335: min 39.5gr max 44.9gr

Hornady:
Varget: min 35.9gr max 44.9gr

I know Spear gives a slightly longer COL, so I could see that maybe accounting for the higher max load (and the compressed load), but the inconsistency of the minimum loads has me worried.

Thoughts? Seeing that I'm shooting Hornady bullets I was planning on following the Hornady manual, but I'm still curious.

 

['Boo]

I figured originally that a 30cal FMJ is a 30cal FMJ, how much difference could there really be?

There could be plenty of differences.

The cores could be different hardness. The jackets could be different thicknesses and hardness or different alloys. The amount of bearing surface could be different. All of these can affect pressures to one degree or the other.

Use the Hornady manual for the Hornady bullet.

 

[Scar270]

As for the minimum, I don't think that means anything below that is unsafe, they usually just offer a range working up to the max. Sierra and Speer may just not have tested as low of loads, that doesn't mean to say they felt lower was unsafe.

Yes there has been reported issues with low powder charges, but thats usually with very small charges, under half the capacity of the cartridge. Put it this way, I load 28.3 gr of IMR 4895 in my .308 with a 150gr bullet so as to reduce recoil in my handgun. Not many loading manuals will go anywhere near that low on the powder charge. Thousands of rounds later I'm still fine and so is the gun, but 28.3 gr still fills a fair amount of the case capacity.

Basically I wouldn't worry about the minimum loads being different, I'd be more concerned about the maximums.

 

[Boomer]

Nothing to worry about. Both manuals list minimum loads expecting folks to work up safe loads in the specific rifles from there. Where exactly those minimum loads start doesn't make much difference. You will note that the Speer manual works in increments of full grains of powder with the resulting velocity listed while the Sierra book works the loads in increments of 100 fps with the resulting powder charge listed.

 

[bisonhd]

Usually the manuals will advise you when it is unsafe to go below minimum loads, causing hangfires or detonation, the terms I've read.

 

[corney]

I,m also concerned with the maximum. I have five manuals and there is lots of conflicting information in some of them. I don't purposely load to the max sometimes I'm just trying to match factory rounds. Sometimes its the max in some manuals and other times its below.

I'm guessing that a safety factor is included in this info just like engineers over design to cover their butt?

 

[Scar270]

I'm not certain how much safety factor is built in. Probably some, but not much. I think the conflicting data has more to do with the particular test barrel, chamber etc. Every company will have a slightly different barrel, perhaps a different barrel length. So many variables. Thats why they tell you to start at the minimum and work up watching for pressure signs in your particular rifle.

If you want to see the margins of error looking in my lee manual, it lists loads that are up to 51,300 CUP and a .308 is supposed to be good for 52,000 CUP. Not much room for error in my mind.

 

[t-star]

i can tell you that 42 grains of 748 will not cycle any m14 action reliably- i know this from 4 different rifles and LOAD DEVELOPMENT= mine- however, going up to 44 grains gives you a match load but that's the bottom load for a 308 win for 150 grain- i go by what's on the net, my own experiences and a couple of manuals- i have 6 rifles in 308, and each one has a different prefernce - and never ASSUME YOU CAN GO OVER THE MAXIMUM because of the 'SAFETY FACTOR" once you get above a certain pressure , you can get PRESSURE SPIKES that WILL DESTROY YOUR GUN-

 

[rookie wildcat]

33, "UBIQUE" brother. There are many variables involved here when companies produce their load data. Really, the only way to compare them is to have them all the same. In every case, changing only one component can drastically change performance. Did they all use the same case from the same lot and manufacturer when they tested these rounds? Did they all use the same lot # of powder? Did they all use the same primers? Were all the components loaded, chambered, and fired at the same temperatures in each and every case?
You see, every case manufacturer differs in case capacity...heads, webs, or case walls may be thicker resulting in differing pressures.
Whether you use a Winchester, CCI, or Federal primers determines ignition speeds.
Different lots of powder are slightly different chemically.
Temperature changes velocity.
Now I am sure that in all cases temperature was room temperature and really isn't a factor but the others are valid. In the end it really doesn't matter where you start as long as you don't exceed the max and hurt yourself, besides max loads aren't always the best. As you work up the load, your rifle will tell you what it likes as your groups get smaller and then start to expand again. I hardly ever shoot MAXIMUM loads, whether velocity or pressure. But then again, I load for fun and I only hunt, I don't shoot well enough anymore to shoot matches.
Enjoy this journey, the destination is tuning a round for YOUR rifle. Just go slow and be safe.