I NEED A EXPLANATION!!!

The bullet style does make a difference based on bearing surface and seating depth tested. I load 4.8 at 1.090 under a 115 rmr mmw. A round nose with the same seating depth will have more bullet in the case.

Actually, the bullet style makes a big difference. Study your reloading manuals. As stated, the issues are seating depth, bearing surface, and bullet material. Especially in 9mm, the shape of the bullet nose will have a huge impact on seating depth which affects pressure. Please read as much as you can and ask questions. To answer your question directly. There are 2 issues with the different load values posted for similar weight bullets. The first is, as I stated, different bullet shapes require different seating depths. That affects pressure. The second factor is lawyers. Some manufactures hold back on the loads so you don't blow yourself up.

Bullet weight and burn rate .... Both make a difference. Stick to the load data and you'll be fine.

A man with one clock, always knows what time it is. A man with two, is never sure.

Different environmental conditions, different lot of bullets, different lot of powder, different brass, different primers, different guns, different measuring equipment, different interpretation of data…

It’s amazing they are as close as they are.

74man said:

why are the such a difference in load data? ... why the big difference in load data??

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Published load data are developed based on measured chamber pressures to SAAMI max pressures.

And different variables such as bullet type, bullet diameter (.354"/.355"/.3555"/.356"), nose/profile type (ogive), OAL/bullet seating depth, test barrel groove-to-groove diameter, test barrel length, brass/primer used, etc. can affect chamber pressures and muzzle velocities. So depending on testing variables, powder charges used can/will vary to produce the same level of average max pressures. (And if you look close, not all published max pressures are the same)

74man said:

My son wanted to load about half of the max powder load ... with half the Max load we should be fine. Right?

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Not necessarily.

If what you mean by "half" is halfway between published start/max powder charges, depending on bullet weight and powder burn rate, you may not get reliable slide cycling and/or accuracy at mid-range load data as lighter 115 gr bullet with some powders (especially if using longer OAL) may require high+ range load data to reliably cycle the slide and produce accuracy.

If you can provide more details like bullet brand/type (Lead, coated lead, plated, jacketed), pistol models, powders on hand, we can better guide you towards our pet loads that have worked well for our pistols.

74man said:

My son wanted to load about half of the max powder load, in all four bullets. 115 RN, 124 HP, 124 FP, & 147 RN so we should be safe. Hopefully we will go to the range Sunday if the weather holds and he doesn't have to work overtime. Will inspect the cases for things like bulging or cracking but with half the Max load we should be fine. Right?
Also we will see what he likes for a load although this is the first time he has fired his Glock 23.

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If you see pressure signs in a 9mm your waaay hot.

I load only 124 gr. With Unique and CCI 500 primers in various cases 4.8 to a max of 5.2 grains works well with 124 gr. jacketed FMJ bullets. I find Speers max data too hot for my liking.

Don't load under the starting load in the manual for the bullet type/weight you are using. Don't load over the MAX load in the manual for the bullet type/weight you are using. Often, there is a starting load recommendation in the manual for any given powder/bullet/cartridge. Until you learn more about reloading, stick to starting at the recommended starting load. If at all possible, find a friend with experience to help you along the learning curve. There are many good loading manuals out there, and the NRA has published numerous editions of "How to Reload" manuals for decades - these can be found online and in used bookstores.

74man said:

My son wanted to load about half of the max powder load, in all four bullets. 115 RN, 124 HP, 124 FP, & 147 RN so we should be safe...

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Can you please give a definition of what "half of the max powder load" is and exactly how much powder you loaded in each bullet weight as well as the overall length of each.

As greenmtnguy said, never load under the minimum charge. I'm worried that if you actually loaded 50 percent of the maximum charge weight you're likely to experience poor function and possibly even stick a bullet in the barrel.

Check for a new hole in the target after each shot, if you don't see one, DO NOT FIRE ANOTHER SHOT UNTIL YOU'RE SURE THAT THE BORE IS CLEAR!

Firing a round in an obstructed bore can cause a catastrophic failure and may cause death or serious bodily injury.

You better double check your model of Glock and cal. , because you said Glock 23 which is 40 s&w and your talking about 9mm loads , unless I miss understood and the 23 you refer to is another gun

Before you go test fire your loads, have your son bring his gun over, disassemble it. Take his barrel and drop each round into the chamber, this is called plunk test, each should fully chamber and fall out on its own. If they don't investigate why, could be a few different things like, oal too long for bullet in that gun short throat, tight chamber, or not enough flair removed. You don't want to shoot a round with the bullet jammed into the lands, could cause pressure to spike and damage gun or shooter.

I changed bullets recently and had to shorten my oal because of a different rn profile.

While you have noted there are big differences in published load data, they all have “starting” loads and “max” loads.
You need to determine your max COL for your gun(s) and bullets before reloading them.
@Maintenancan8193, welcome to THR! And you’re right, better check to make sure what your son really bought! Good luck.

It's not so much the differences in the bullets "style" that makes a difference. Nor is how much bearing surface 1 bullet has compared to another a huge factor.

The real difference is how much case capacity the bullet being reloaded (reload data) uses. Same bullet weights but a huge difference in the amount of case capacity left for the powder. Less case capacity ='s higher pressure for the same powder/load.


Even using the same bullet and changing the seating depth/oal will change the pressure of a reload.


Powder companies put things like this in their reloading manuals all the time.


Or put warning out like this old "Hercules warning when too many people were scattering (kabooms) their beloved target 38spl revolvers to the four winds.


Anyway for the most part you see conflicting data simply because 1 bullet takes up more case capacity than it's counterpart even though they have the same weight.

So, I've seen a lot of replies here about why different bullet types make a difference and that is true and important to know, however, I don't think anyone has fully answered the generic aspect of OPs questions. I interpret his question around the lines of why does load data from different sources for what would appear to be the same bullet type differ and more importantly which one should you use or how do you approach it?

So while bullet type can impact load data for all the reasons folks have stated, there are a few reasons different load data sources will differ for the same powder and same bullet type. The reasons are different COL used. Most loading sources will list the COL they used, most often they will differ source to source and most importantly you might not be able to or want to use the exact COL they used. Barrel length of the test gun will differ, also impacting their listed data as often they are trying to achieve a specific velocity and the specific bullet used is probably different.

That being said, I will start at the low end of the powder manufacturers data (maybe even 5% lower if I'm using a smaller COL) for the bullet weight and type that is closest to what I'm using and start working up my loads from there. Typically for 9mm that will give velocities around 950 fps and should be very safe low pressure loads as a good starting point.

Listen to what @stillquietvoice posted and check some of your reloads to be sure they will run in your gun.

Glocks have been known to be picky about reloads. Don't be the guy that ruins his gun because he didn't take a minute to check his ammo.

Another thing that was touched on above about a squib, in the military we called it a "pop and no kick". If you get this, don't pull the trigger again! Your gun could blow up in your hands. Unload it, pull the gun apart and check the barrel for an ubstruction.

Be safe, keep to the published data and listen to what guys are telling you.

Mk-211 said:

Listen to what @stillquietvoice posted and check some of your reloads to be sure they will run in your gun.

Glocks have been known to be picky about reloads. Don't be the guy that ruins his gun because he didn't take a minute to check his ammo.

Another thing that was touched on above about a squib, in the military we called it a "pop and no kick". If you get this, don't pull the trigger again! Your gun could blow up in your hands. Unload it, pull the gun apart and check the barrel for an ubstruction.

Be safe, keep to the published data and listen to what guys are telling you.

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Stop at harbor freight and spend 5 dollars on a set of transfer punches. Take the best fitting one with you so a squib is easily cleared. A plastic dead blow hammer is nice because a miss is not damaging your barrel in any way.

AJC1 said:

...transfer punches...so a squib is easily cleared.

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Pound on a piece of carbon steel with no risk of damage to the bbl? I know brass is safely used as a squib rod but carbon steel would give me pause.

74man said:

My son wanted to load about half of the max powder load, in all four bullets. 115 RN, 124 HP, 124 FP, & 147 RN so we should be safe.

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Actually, no it isn't safe. If you wanted to be "safe" you would work up your loads. What you are doing is called "guessing".
.

Please read more and look at what you have loaded. I think some will be out of spec with the load data. May be dangerously out of spec.

Are you saying 1/2 of the MAX load listed,
as in MAX is 3.8gr, so you are loading 1.9gr?

Or, you are choosing a load 1/2 of the way between MIN and MAX?

1. NOT SAFE, DO NOT DO IT
2. YES. Especially using several sources. Do not BEGIN at any load ABOVE a listed MAX or BELOW a listed MIN.

For auto pistol, so many bullet configurations exist. I prefer to use load data FROM THE BULLET MANUFACTURER!

My manuals are Barnes, Sierra, Nosier, and Hornady. Others are available On-line.

Herman B said:

Pound on a piece of carbon steel with no risk of damage to the bbl? I know brass is safely used as a squib rod but carbon steel would give me pause.

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If it's a tight fit there is almost no chance of damage. Loose would be bad. That kit has one with a good fit because I've used it. A squib is not welded in.

74man said:

My son wanted to load about half of the max powder load, in all four bullets. 115 RN, 124 HP, 124 FP, & 147 RN so we should be safe

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No. Read your loading manual. It will tell you what your safe starting load is. Most data gives minimum charge and maximum. Some manuals only give the maximum load, in which case, the manual tells you the minimum charge is 10% below maximum.
In a few powders, very few, there is data that might go as low as 50%, but it will always be printed in the manual.
To repeat, read the manual. don't guess!

To me loading manuals are all over the place, Lee, Hornady, Lyman. I prefer load data from the manufactures. And some of the best info does come from people on these sites that shoot strings and through a chronograph, which I like to use myself.