what is the purpose of starting at 10% off of max

[southernshooter]

ok i havent been on here in a while but i need some answers and this is the place to find them. i can not for the life of me figure what is the purpose of starting out at 10 % below max pressure as listed in a book. ?? i have read alot of articles and saw alot of people talking about pressures ...well im not convenced that these people a chamber pressure lab in there home or shop so what is all the talk about pressure and max loads ? it seems just do as the manual says with the right powder and see if it groups well or not ,maybe thats the rookie reloader talking in me but i dont understand and i feel like i need to in order to become a talented reloader for paper targets and live targets ...any replies will be greatly appreciated thanks

[PA-Joe]

Safety! That max load worked in their gun with their components. Some of this data is based on very old information and powders. You start low and work up.

[mapsjanhere]

The 10 % rule is giving you the safety margin when making a load for your specific gun and component selection. You might be using extra thick brass in a really tight cut competition chamber, and the 90% load might already give you max pressure (indicated by overpressure signs like popped or pierced primers or really sticky bolt). Ditto your 115 year old Chile Mauser might not appreciate full loads anymore due to that field gauge eating head space.

[southernshooter]

starting low for what ? thats what i am asking i guess ..what am i supposed to see or not see by starting low ? it seems like they wouldnt print the max load it seems like they would say dont put any more than X amount in there and go with that im so lost on this pressure thing it is smoking my brain im losing sleep at nite reading article after article and still nothing

and how would i know if i had max pressure ? unless the barrel blew off or my face exploded i wouldnt know i reached or achieved anything . thats why all these people talking about pressures like they work for hornandy or nosler in the lab blowing up casings everyday are making this very complicated for me i enjoy reloading but im not feeling like i am achieving anything other than making the same bullets i can buy at the store ...plz help me

[mapsjanhere]

overpressure signs like popped or pierced primers or really sticky bolt, in most cases you will notice if you went over max (your max, not the printed number) before the gun blows up into your face.

oh, and you want to make the same bullets that you can buy in the store - just you want to make the specific to your gun, and very consistent.
It really depends what you want, the hottest load, the best bullet for a specific application, the most accurate load, the cheapest round.
If you really want the max power you're usually better off to upgrade your gun than to max a given caliber, like switch from 30-06 to 300 WM, or 22-250 instead of 223 Rem.

[southernshooter]

ok here is the deal ...i own fifty or so rifles , handguns ,and shotguns so reloading some of them just for cheap bullets is a great idea but the ones i pride myself at shooting i am really trying to get the most out of that gun not so much velocity ...group size is the key for me not velocity with that said how do i know what i am looking for in the gun chamber or the casing or on the target ...?? i have several loads made up of 30-06 ,for what i call a beat around deer rifle ,with a couple of differernt powders they all have the same projectile berger 175 match VLD in them ..ok i have loaded them starting at 10% less i have a strings of five up to the max load so ...now what am i looking for when i start shooting the strings of five? i only have five bullets for each powder grain increment and only five loads to reach the max so basically i have 25 bullets of one particular powder and 25 bullets of another powder what am i supposed to look for if i feel like a dummy or is this a game of splitting hairs on paper ??

[spacemanspiff]

I am not a reloader, I made an honest attempt at becoming one. Bought the books, all the gear, components, and it collected dust. However, my research and the advice I recieved from many friends who reload, all indicated that the loads are worked up gradually, because even though you have two rifles, same manufacturer, same caliber, etc, that doesn't mean both will give the exact same results with one particular load.

Velocity is one part of the puzzle, as is inspecting your cases, and paying attention to every detail of what the fired cases look like. Some guns will shoot better at higher velocitys, which is an easy way of saying 'hotter load'.

I wish I did take the jump and start reloading, but alas, I work 60 hours a week, and my shooting escapades are far/few between anymore.

[dahermit]

...group size is the key for me not velocity

Then do not start with 10% under maximum. Start with the beginning load listed. Mild loads are more likely to produce the smaller groups over the highest pressure/velocity loads.

[Shane Tuttle]

Have you purchased/read any reloading books?

[olddav]

Not sure if this helps, but I loaded 7 lots of bullets (begining at 55 grains) to get started. Once I found that my rifle liked bullets between 58 and 59 grains of IMR 4350 I loaded an additional 3 lots to pinpoint the exact load. I shot each lot to see how they grouped. None were very good untill I hit the 58.5 grain bullets, (1.75"). My final lot grouped at just over 1" (1.045") and that became my hunting round for my Savage 110 in 30.06.

My limited experience tells me that one should go slow, take your time and pay attention to every detail. The penalty for error my be catastrophic!

[cdoc42]

Your chamber size, the seating depth, bullet shape and length, type of primer, type of case, all play a part. I suspect the -10% recommendation was made by someone along the line who writes for the mags and had a really bad experience and it just got carried along.

After 34 years of reloading I just adopt the position that I can start a grain below max and work up in half-grain increments, but I still "chicken-out" and don't use the max until I'm sure the lower charges are ok. So I start a half-grain below max as my top load and make 2 others at 0.5gr below each. If I don't get a good group I'm more likely to play with seating depth because, as pointed out here, velocity is not always synonymous with accuracy. I had one load that was obviously an overload in a 7mm Rem Mag with a 110 grain HP. The bolt just could not be lifted without a rubber mallet. No other problems, but that was using my system of increasing charges as described.

[Edward Horton]

We have more than one person here who needs to pick up the reloading manuals and start reading from page one.

Not knowing is one thing but not understanding starting 10% below maximum and having to beat your bolt open goes beyond reason.

All the information in the world is written in books and all you have to do is read.

Ed Horton
Quality Control Inspector for 25 years.
Reloader for 40 years.
Reloading is like playing Black Jack, stay light and beat the dealer. (Don't overload and don't go bust)
And I never had to beat a bolt open on any of my reloads or firearms in my life.

[44 AMP]

Is what they found to be the max safe load in their gun, with their bullet, their cases, their primers, and their powder. You can duplicate their load exactly, and still be significantly under or OVER safe max in YOUR gun.

While general rules and conditions apply, every gun, and ammo component combination is an individual, and can have vastly differing pressures.

Starting 10% below listed load is just a safe way to begin. Starting 10% below listed max is grabbing th bull by the horns and jumping in with both feet. Sometimes it works fine, other times, you might get gored.

Sure, it costs more to work up a load, but I always start out at, (or even the magic 10%) below the starting load, until I'm sure its safe in my gun.

Note that ther are some cases and powders where you are specifically told NOT to reduce the charges, but these are special cases.


Some guns will show pressure signs at the listed starting loads. Others won't show signs until you get beyond listed max. Since the publishers can't have any ideas what you will shooting the load in, the tell you to start 10% down, and work up. Its just the smart thing to do.

[southernshooter]

thankyou for all your replies to my problem like i have said and you all can tell i am new to this and just want to be good at making my rifles sing like a canary . thanks again for all your replies

[mehavey]

A simple +/- 10% change in burning rate between powder lots can take a nominal 46,000 psi load as high as 54,000 or as low as 38,000. If you are sitting on max to start, .... you can see the problem.

Add the effects of a "tight" barrel, a smaller-than-advertised case volume, a bullet seated deeper than recommended....

(...and someone earlier asked why a chronograph combined with an internal ballistics program might be useful for safety.....)


Consider reloading to not be a science. Rather, it is somewhere between an engineering problem with all the variables and safety factors -- and an art.

[Uncle Buck]

Like 44 Amp stated. Look at the information provided for each cartridge in your reloading manual, you will see information about what primer they used, what cartridge case they used, what firearm they used, etc.

Your gun may not be the exact gun they used to test their data with, your components may not be the same. You may find a load that works for you which is 7% under maximum recommended max load.

I am glad you asked the question, it means you are thinking.

[BDS-THR]

southernshooter:
starting low for what? thats what i am asking i guess ..what am i supposed to see or not see by starting low ? it seems like they wouldnt print the max load it seems like they would say dont put any more than X amount in there and go with that im so lost on this pressure thing it is smoking my brain im losing sleep at nite reading article after article and still nothing

southernshooter, join the club, I did the same thing when I started reloading. It's been 15 years since and this is what I have so far ...

starting low for what?

Safe chamber pressure that produces consistent powder burn for accurate shot groups.

Powder manufacturers usually test chamber pressure/shot groups using a specific barrel length "fixtures" and not pistols (most published load data will include the length of barrel). As they test various powder charges using specified bullet type/weight/OAL/primer up to the SAAMI max chamber pressure for that particular cartridge, their objective is to determine the starting powder charge that "starts" producing decent acceptable accuracy/shot groups. Usually, consistent chamber pressure go hand-in-hand with accurate shot groups.

Burn rate and characteristics of powder differ in how they perform in particular caliber and bullet type. The primary concern for us reloaders is the "pressure spikes" that may occur near the max load data. To avoid the danger of pressure spikes depending on the pistol/barrel lengths (3"-5"+), we work up our loads from the start load or 10% below max to be on the "safe" side of the chamber pressure max. You may have noticed that some powders have very narrow load range (start/max) and some very broad. I consider powders with narrow load range to be "spikey" and prefer to use powders with more broader load range like W231/HP38 as I have more margin of safety.

I reload to produce accurate loads for match shooting and practice. Working up your test loads is a time-honored practice to identify the most accurate loads that will reliably feed/chamber/cycle the slide of your pistol. Since accuracy usually increases with increase in chamber pressure due to more consistent powder burn, many reloaders often start their work up at mid-range instead of starting charge.

When I work up a new pistol powder/bullet type combination (jacketed/plated/lead/Moly), I usually start my test loads at just below starting charge and work up from there as I have identified some very accurate light loads like 180 gr 40S&W with 3.8-4.3 gr W231/HP38 (recoils less than 9mm and deadly accurate). Keep in mind to not go too far below starting charge as some powder will also develop inconsistent powder burn pattern and pressure spikes.

I hope this helps.

[PA-Joe]

Southernshooter:

I think you are making more out of this then necessary. Stop thinking max charges!

1. Never exceed the listed maxium load. Under normal hunting conditions you don't need that much power.
2. Start at the minium load and work up or reduce the max load by 10% and then work up.

As noted, when you shoot the 5 shot groups you will find one that produces better groups. You can stop there.

The reason why they don't want you to go below 10% is to avoid the possiblity of double charges. They want a nearly full case of powder.

[GeauxTide]

If the subject is keeping you up at night, then buy 3 or 4 loading manuals and read them cover to cover. Before I bought my first rifle or loading gear over 40 years ago, I bought three loading manuals. In the ensuing years, I've loaded for only one rifle cartridge out of 13 that was most accurate at the maximum.

One way to look at it - if your vehicle has a tachometer, do you try to run at the red line as much as possible?

[Edward429451]

The reason you hear of people starting 10% below max is usually because they do not like reloading and want to hurry and get to the magic load, and we all know thats the bear stomping loads right?

When I switch brands of primers or open a fresh pound of powder, I reduce the load by 10% to account for variations in manufacture. This is widely recommended to do.. Perhaps some guys read that as reduce any load by 10% and your gold. Laziness?

One should make a practice of using starting loads. I load a lot of starting loads. They are not starting loads on the range though, just ammo that goes bang.

[Tim R]

I normally stop before reaching the "Max" load. I've found for the most part, the rifles I want to punch holes in paper with punch bullets through same hole at about midway between the starting load and the max load. If I'm hunting, I figure the deer or elk will never know I could have shot that bullet 200 FPS faster.

[Clark]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
I converted an 80 year old VZ24 Mauser from 8x57 to 7mmRemMag by opening up the bolt face, extractor, magazine, feed lips, and changing barrels. 4 days ago I put in 20% over maximum powder. The bolt handle was badly jammed. It took a long time to pound the bolt handle open. The primer fell out of the case. The bolt and receiver did not fit any more. Headspace was set back .005".
I lapped out the interference with #60 grit.
I cleaned out the receiver to get out the grit.
Now the gun is shooting again.

What does it all mean?
You don't want this to happen to you.

[medalguy]

May I suggest a good book to start with? The ABC's of Reloading. It's one of the best books for information I've seen around. It's available from Amazon.com for about fifteen bucks as I recall. It will tell you everything you need to know about reloading and safety. I tell new reloaders to read it twice before even starting to reload.

I've been reloading since 1965 and there are still things I don't totally understand about ballistics and pressure. Juast be careful, start low, and take your time with reloading.

[p5200]

Every gun is different the striations on the bullets of two alike, rifles are going to be different. I assume, that's why two or more rifles just alike prefer different brands/weights of ammo to get the tightest groups. Be safe, and have fun!