What are the consequences of using less powder than recommended as the "minimum" amount?

Forgot to mention: I'm loading 9.3x74R

Thank you

What's your dilemma?
What are you trying to do?

I'm really trying to understand stuff. I understand how exceeding maximum published loads could cause problems, but don't understand the consequences of using less than mfgr recommended "starting" loads.

Or, for that matter, how do the manufacturers determine the starting loads?

I've never had any problems, but then I have a tendency to consider the maximum as my starting load. That being said I have read of things that can happen.

Squib
Hang fire
Inconsistent powder burn
Primers back out jamming action
Higher chance of an accidental double charge

The big issue with an overly reduced load is what's known as a "flash over" These typically occur when a load is reduced to somewhere around 50% of case volume. As the powder lays in the bottom of the case, the primer charge flashed over the entire length of the charge, essentially igniting all the powder at one. The creates a much faster ignition of the powder, and a possible BOOM in your chamber. That's the major danger I"m aware of. I've never really worried about reducing a load so long as I kept it above 65%+ of case capacity.

quote:

Originally posted by 56hawk:
I've never had any problems, but then I have a tendency to consider the maximum as my starting load.

I guess we all take a different approach to reloading... I wish you all the luck with yours, and hope you'll live to tell your children about all the foolish thing you did when you were still young...

- mike

quote:

Originally posted by mho:

quote:

Originally posted by 56hawk:
I've never had any problems, but then I have a tendency to consider the maximum as my starting load.

I guess we all take a different approach to reloading... I wish you all the luck with yours, and hope you'll live to tell your children about all the follish thing you did when you were still young...

- mike

I've never had any signs of high pressure with any of the maximum loads listed in my reloading manual. Of course I only go above maximum with strong modern firearms.

quote:

Originally posted by Oxon:
I'm really trying to understand stuff. I understand how exceeding maximum published loads could cause problems, but don't understand the consequences of using less than mfgr recommended "starting" loads.

Or, for that matter, how do the manufacturers determine the starting loads?

Certain combinations of cases (most commonly large, "magnum type") and powder are often listed as problematic by reloading manuals when minimum loads are (significantly?) undercut. Hang fires, muzzle flashes and even detonations are cited as possible consequences. I believe a lot of this has to do with (imperfect) ignition of powder charges not backed up against the flash hole.

Sometimes, fillers are recommended as a work around, to ensure that the powder charge is positioned correctly against the flash hole. I have also seen recommendations for tipping the loaded rifle back before firing - again to position the powder. The latter method is hardly practical for anything other than range loads, and even fillers can have their own problems (barrel bulges etc).

I'm not about to issue a recommendation about what to do in your specific case and what not. I merely cite warnings published in reloading manuals (e.g. NRA "Handloading" or RWS manual).

Published minimum loads (just like maximum loads) will differ from manual to manual. As frustrating and as incomprensible as this may seem, this seems to be the uncertainty a reloader has to live with. If possible, get data from multiple sources, compare and establish what seems a reasonable compromise.

- mike

Being one who sometimes starts with powders for which no data is available for a given cartridge and who, in such situations, starts conservatively, I have personal experience with some low load situations:

1. There will always be excess powder residue in the barrel.

2. Accuracy has never been optimal for me.

3. There may be soot down the side of the case and the case may come out REALLY hot because of a poor seal.

4. Primers may be backed out (not from high pressure by the way).

5. I somewhat doubt that "flashover" or "detonation" ever occurs but you can get excessive pressure with low pressure loads. My belief in how this happens is that the powder starts to move the bullet down the barrel where the bullet starts to hang up (i.e., slow or even get briefly stuck). The pressure in the chamber meanwhile is rapidly building up and finally reaches the point where the bullet starts moving down the barrel again. It takes a lot more pressure to start a stuck bullet than to start one with a little jump to the bore. I had this happen once with a low 454 Casull load that almost locked the cylinder. It's my belief that this same mechanism is responsible for hang fires but I've never had one of those.

As far as starting with maximum loads goes, I don't do that but I don't think I've ever had a situation where a maximum published load has been an unsafe one. I think the main "risk," if you can call it that, is missing the load that provides the best accuracy which frequently comes at less than a maximum load.

A "few" powders are NOT conducive to downloading. H110 comes to mind and Hodgdon even warns you not to reduce loads more than 3% of those listed.
My big concern would be a bullet that does not exit the barrel, goes unnoticed, UNTIL the next one is fired. One company that makes a bore-lapping kit even recommends that you shoot a target when fire lapping so you can see holes in the target due to the fact that you are intentionally shooting the fire lapping loads at airgun speeds.
If you want low-speed loads, do the research to use the right powders for these loads. The info is out there.

quote:

Originally posted by aliveincc:
A "few" powders are NOT conducive to downloading. H110 comes to mind and Hodgdon even warns you not to reduce loads more than 3% of those listed.

from experience I found this to be true with the H-110 in a 38 Special "revolver" and lead bullets. Two stuck in the barrel at once! The same load in my 38 Special rifle was great (No cylinder to barrel pressure drop). roger

quote:

Originally posted by Oxon:
What are the consequences of using less powder than recommended as the "minimum" amount?

Forgot to mention: I'm loading 9.3x74R

Thank you

I don't think there is a good answer for this.
There are some powder cartridge combinations that will permit quite a reduction.
Then there are some that will misfire or create gross over pressure conditions. The best you can do is ask questions and read as much as you can.

As a general comment, non-specific to the 9.3, many powders do not burn correctly below a certain designed pressure level peculiar to each one. When they don't burn properly, lots of different things can happen.

I would guess the most common two undesirble things are inaccuracy, and hangfires. A third might be very dirty bores, chambers and/or brass after firing.

quote:

Originally posted by Grumulkin:
...you can get excessive pressure with low pressure loads. My belief in how this happens is that the powder starts to move the bullet down the barrel where the bullet starts to hang up (i.e., slow or even get briefly stuck). The pressure in the chamber meanwhile is rapidly building up and finally reaches the point where the bullet starts moving down the barrel again. It takes a lot more pressure to start a stuck bullet than to start one with a little jump to the bore. ...

Agree with the above portion of Grumulkin's post. Also agree that Flashover can occur.

You can also get a Secondary Explosion Effect or Pressure Excursion which is similar to the above, except they result in a Ka-Boom. So, if you are interested in that, you can get there with some inappropriate loads.
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Starting at MAX Loads is the sign of a very inexperienced Reloader.
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If you just stick with Starting Loads found in the Manuals, work your way up while watching for Pressure Signs, it is seldom you will have any problems.

quote:

Originally posted by Hot Core:
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Starting at MAX Loads is the sign of a very inexperienced Reloader.
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Well, I've been reloading for over twenty years, have loaded hundreds of thousands of rounds, and have never had any problems or any signs of high pressure with a published maximum load.

Exactly why would you consider the book Max as a starting point?? What are you hoping to achieve? Curious minds would like to know.
Often, book maxes are not about pressure nor capacity but rather deal with efficiency.

I remember that some loads from the Speer Manual #8 were reduced in following years because some of them were downright dangerous at the listed "max" level in SOME rifles. That info was widely known soon after the book was published.

I also had a Holland & Holland rifle which would pop primers and freeze the bolt closed with factory loads. To cavalierly start with maximum book loads in that rifle could have been an invitation to witness an injury....MY injury. NO THANKS.

There is a reason EVERY loading manual suggests starting with minimum level listed loads and working one's way up if the handloader wants to shoot hot loads.

Lots of shooters get away with doing unsafe things; some do those things their whole lives. In the old days we used to explain that by saying "God protects drunks and damphools." I AM NOT saying anyone here is either one, but I will say that starting with book maximum loads as a "systematic" approach is not a safe practice to use.

quote:

Originally posted by wasbeeman:
Exactly why would you consider the book Max as a starting point?? What are you hoping to achieve? Curious minds would like to know.
Often, book maxes are not about pressure nor capacity but rather deal with efficiency.

quote:

Originally posted by Alberta Canuck:
Lots of shooters get away with doing unsafe things; some do those things their whole lives. In the old days we used to explain that by saying "God protects drunks and damphools." I AM NOT saying anyone here is either one, but I will say that starting with book maximum loads as a "systematic" approach is not a safe practice to use.

Sorry that this is starting to get off topic. I was just saying in my original post that I've never had any desire to load below the minimum, but with certain guns do load above maximum.

For reference I usually use the 49th addition Lyman reloading handbook, but crosscheck with several other sources. Usually the Lyman maximum load is less than others.

My reloading procedure is as follows for different firearms:

Antique rifles and handguns that are not semiauto - start with minimum load work up slightly if needed.

Antique semiautos - start with minimum load and work up until reliable cycling is achieved.

Modern semiautos - start with midrange load and adjust until reliable cycling is achieved.

Modern strong bolt action rifles and revolvers - start at or near maximum load and work up until pressure signs appear or desired performance in achieved.


With most of the guns I load above maximum it's just because I like shooting powerful guns. I used to load my 44 Magnums well above maximum. Now that I have a 500 S&W, I pretty much just stick to the maximum loads for 44 and 357. I start with maximum loads for my 460 Weatherby for the same reason. The bolt starts to get a little hard to open with a one grain overcharge. Hence why I'm having a 600 Overkill built.

Other reasons include pushing a 243 over 4000fps for a pretty awesome varmint load. Also loading 38 super to make major power factor for USPSA competitions. 1550 fps with a 115 grain bullet. That's a bit over the listed maximum of 1300 fps.

Don't take me wrong. I too load over book max in some of my rifles, with some powders. But I worked up to those loads.

I really don't want to see beginners (or anyone else) thinking that any max load listed in a manual will necessarily be absolutely safe in THEIR rifle, without woking up to it to be certain.

quote:

Lots of shooters get away with doing unsafe things; some do those things their whole lives. In the old days we used to explain that by saying "God protects drunks and damphools." I AM NOT saying anyone here is either one, but I will say that starting with book maximum loads as a "systematic" approach is not a safe practice to use.

This is as wise a thing as has ever been posted on any internet forum.

A new book might keep you from blowing a primer or case starting with a max load. Using the manuals I started with 30+ years ago from Hornady Vol II and spear I've blown a number of primers before ever reaching their max published loads.

To each his own but not something I would do or recommend.

Speer was one of the last companies to get pressure testing eq, etc. Their reasoning was that Joe Reloader didn't have the eq and so it was pointless for them to have it. Their maximum loads were based on the same criteria that home reloaders used: Primeer appearance, bolt lift, head expansion, and so forth.
One can see considerable difference between the old books and the new ones.

quote:

Speer was one of the last companies to get pressure testing eq, etc.

Can't say about speer. I do know that Hornady point blank said they didn't run all the load data. That powders like IMRs had the same energy per grain that the coating slowed the process so that a fast powder and slow would form a set of parallel lines. They would then call max either a full case or .0005" shell expansion.

So I assume somewhere over the years both Hornady and Speer altered their manuals.

As I said to each his own but taking a book max as a lower starting point for load development and suggesting it as a safe method is beyond me.

A few scattered instances of KABOOMS have occured with greatly reduced charges. Experiments to replicate them have failed, as best I can learn. Flashover and interrupted bullet movement are plausable theories that really can't be proven so believe which ever or neither as you want.

What can be proven is that all smokeless powders are designed to operate most consistantly within a fairly narrow pressure range. Get to far below that pressure range and the burn will become too erratic for decent accuracy.

Decent accuracy at very low speeds generally suggests light charges of faster burning powders than normal; they can get the pressure up without staying high for long enough to produce high speeds.