Minimum Loads? Is there a rule of thumb?

[johnfred1965]

I did not want to hijack a thread asking another question but do you know what is considered below minimum for loading information? Other than book listed loads I mean. I know H4895 can be reduced 40% per Hodgdon's website, but is there a percentage to not go under with other powders as a general rule? I have always heard reduce max book loads by 10% to start, or used starting loads listed. I have really only worry about light loads when shooting my straight wall revolver cartridges.
Just wondering if there is a rule of thumb to avoid Detonation or low pressure signs?

 

[RonAKA]

I did not want to hijack a thread asking another question but do you know what is considered below minimum for loading information? Other than book listed loads I mean. I know H4895 can be reduced 40% per Hodgdon's website, but is there a percentage to not go under with other powders as a general rule? I have always heard reduce max book loads by 10% to start, or used starting loads listed. I have really only worry about light loads when shooting my straight wall revolver cartridges.
Just wondering if there is a rule of thumb to avoid Detonation or low pressure signs?

I can only relate my experience with a 264WM loaded with H4831. I was doing a ladder test and started with the minimum recommended load from the on line Hodgdon site for 140 grain bullets. I did not realize it at the time, but Hodgdon has interchanged the loading for 140 grain with 160 grain. Hodgdon listed and still does the following loading:

Bullet - Starting - Maximum
140 - 51.7 - 55
160 - 58.1 - 61.8

I recall it was the 51.7 grain load that caused my cases to collapse, and perhaps the one above that. That is 6.4 grains under loaded, or about 11%. This was the result:

I believe H4895 is much more forgiving because it is faster burning and develops more pressure early to expand and seal the neck.

The interesting thing is that I informed Hodgdon of their error, and they have never bothered to fix it. I don't shoot 160 grains, but I know that 62 grains of 4831 under a 140 is a stout load. I wouldn't want to pull the trigger on that much powder behind a 160 grain.

 

[johnfred1965]

I saw your same post the other day, that is what got me wondering. Sounds like Hodgdon is being irrisponsible with those charges. Guess that is why you have to agree to the disclaimer before entering

 

[SheepDog]

When I start loading for a new gun, powder or bullet I always start at the listed beginning load. I work up to the accuracy point never exceeding the maximum listed load. When loading with a new powder in a semi-auto I also work from the listed starting load down to find the point where the load no longer functions reliably. That tells me how reliable the load will cycle the action. I was told by Hodgdon that they use a percentage of the maximum load to get their listed starting load. I was told that they could not recommend loads below that starting point but that the powder I was working with was not sensitive to position in the case. I was using TiteGroup and got well below the starting point with no signs of failure to function. I stopped at 2.8 grains with a 115 grain bullet and was amazed that the load functioned flawlessly and the accuracy stayed very good as well. The standing rule is to use fast burning powders for reduced loads and slow burning powders for high velocity loads. When ever you go above or below the listed loads you are on your own. Be careful and work in small increments. At the first sign of trouble STOP!

 

[Lapua40X]

... use starting loads listed (in published manuals)

That's the way to go. Hodgdon data relates to Hodgdon powders. On the range, just as in the lab, careless experiments tend to blow up on you (or the guy shooting next to you). I've been beside a revolver that self destructed - it ain't pretty.

 

[ireload2]

A pretty good rule of thumb is to buy 5 to 7 completely different manuals. Review the data. Throw out the high and low data for your proposed load. The remaining 3 manuals should have data that is close. Use that data.
You really cannot trust any other rule of thumb because reduced loads of ball powders are not predictable. Depending on the position of the reduced powder charge, it may fire normally or it may partially ignite causing a start/stop bullet and lock up your bolt. You may find a rule of thumb for 4895 but you will find all kinds of warnings for ball powders to use exactly as specified in the manuals. Heed the manuals.

I did not want to hijack a thread asking another question but do you know what is considered below minimum for loading information? Other than book listed loads I mean. I know H4895 can be reduced 40% per Hodgdon's website, but is there a percentage to not go under with other powders as a general rule? I have always heard reduce max book loads by 10% to start, or used starting loads listed. I have really only worry about light loads when shooting my straight wall revolver cartridges.
Just wondering if there is a rule of thumb to avoid Detonation or low pressure signs?

 

[RonAKA]

I have to retract what I said earlier. I did a search and found my original post on this issue with the dented cases. I really can't blame this on the Hodgdon interchanging the data of the 140 and 160 grain loads, because it happened with a 107 grain Sierra MatchKing. Here is the correct load information. I was right in that it was H4831 powder. The loads I tested varied from 64 grains to 67 grains. Two of the 64 grain loads dented and one from the 65 grain load. Now when I look at the various data sources, I believe 69 grains is probably the correct max load. 64 grains is a reduction of 7% was an issue. And even 65 grains, which is 5.8% was an issue in some cases too. Would suggest with this bullet and powder combination a reduction of only 5% is tolerable...

In any case here is the link to the original thread from 9 years ago, which has the correct data. I was all wet when I was recalling it was the 140 grain load that gave me a problem!

http://forum.accurateshooter.com/threads/new-barrel-puzzling-developments.3749153/#post-35869104

Also, I see I took some measurements that do suggest a higher pressure in the lowest load which was obviously too light.

 

[Bart B.]

10% below max is my standard for what's listed for load data.

With 308 Winchester loads, I've seen fired case shoulders end up .001" or more less after firing loads about 10% less than listed maximum. Firing pins drive them hard enough into chamber shoulders to do set shoulders back that much. About 15% or more less than maximum charge weights and shoulders got set back .007" to .008" with Federal nickel plated brass cases, .005" or so with Federal all brass cases.

There's not enough pressure to push the back half of the case back until its head stops against the bolt face.

As all load lists are based on a wide range of component lots and assembly ways, as well as barrel bore, groove bore and length, plus how fixed or loose the rifle's held. a listed load will easily have a wide range of average muzzle velocity and pressure indicators. There are no conditions and standards everyone and everything meets in load development, testing and assessment.

 

[johnfred1965]

Thanks for the update Ron. Your new info shows that even the 10% rule can go too far. Thanks for everyones input, I do use several loading books and websites for my starting loads, except when my 6.5lapua was new and info was not available. I used starting loads from reliable shooters and writers on here. Almost seems like finding a min load is as hard or harder than finding max. I will be going backwards like that when I work up my 300blk loads.

 

[Tommie]

My rule of thumb:
The slower the powder burn rate, the scarier reduced loads become.

 

[MagnumManiac]

I will tell you my own take on this.
I worked for ADI here in Australia, they make powder and ammunition.
Their reloading data is taken from a computer model, not actual testing, although their ammunition is thoroughly tested.

I do not reduce my loads 10% as per ADI's testing structure for their own ammunition.
I reduce my loads from the listed max by no more than 5% and round DOWN to the nearest whole or half grain.

This is ample in reduction to stay safe with a known rifle, although a wildcat may be safer using published data and sticking with starting loads.

I have a formula for working out start loads in wildcats that has never given me problems, but am reluctant to post it online as it may not be safe in all rifle designs.

Cheers.

 

[ireload2]

I once loaded some ammo for the 7.65 Mauser round using Accurate 2495 which is supposed to be the Accurate facsimile for 4895. At the time 2495 was a new powder and most of the data came on a flier stuffed into and sealed inside the powder cannister. The closest data was for the .303 British for approximate case capacity and pressure. The Mauser round has a little more capacity and I cut the .303 loads 2 grains to start. I thought that would be safe enough. The 3rd round blew a primer. I had 2 rifles of the same caliber. The one that blew the primer was new to me that day. The older rifle shot the same ammo without any issue. So I switched back to the newer rifle and it blew another primer on the second shot.
Then I sat down and went through everything. All I could find was the new rifle had a firing pin that went plop when I pulled the trigger on an empty chamber. It sounded nothing like the firing pin fall of the second rifle. I stripped the bolt and found it jammed full of cosmoline. I cleaned all of that out.
Next I pulled the bolt out of the old rifle and used it in the new rifle and all rounds fired ok. Then I put the original bolt back into the new rifle and it also worked.
Apparently the gummed up firing pin combined with the reduced load caused one of those bullet start/stop/start conditions that blew the primers. The pressure was so low in most of the rounds that the entire case was covered with soot. Since the majority of the rounds had that soot I guessed that the pressure was too low.
The next time I took those rifles to the range I sort of rolled the dice and boosted the loads. I only needed a mild load for informal target and group shooting. However the load that I settled on was 4 grains higher than the primer blowing loads. The next manual from Accurate had a maximum load listed very close to what I was using.

 

[mikegaiz]

I can only relate my experience with a 264WM loaded with H4831. I was doing a ladder test and started with the minimum recommended load from the on line Hodgdon site for 140 grain bullets. I did not realize it at the time, but Hodgdon has interchanged the loading for 140 grain with 160 grain. Hodgdon listed and still does the following loading:

Bullet - Starting - Maximum
140 - 51.7 - 55
160 - 58.1 - 61.8

I recall it was the 51.7 grain load that caused my cases to collapse, and perhaps the one above that. That is 6.4 grains under loaded, or about 11%. This was the result:

I believe H4895 is much more forgiving because it is faster burning and develops more pressure early to expand and seal the neck.

The interesting thing is that I informed Hodgdon of their error, and they have never bothered to fix it. I don't shoot 160 grains, but I know that 62 grains of 4831 under a 140 is a stout load. I wouldn't want to pull the trigger on that much powder behind a 160 grain.

This case dimpling can also be caused by not enough bearing surface between the bullet and case, Bullet seated out too far and not sealing upon discharge,