I AM CONFUSED!!

[74man]

I have about 250 each RMR 9mm 124 Gr .JHP bullets and I want to load some 9mm with them. I have looked in my Speer #14 book and it shows 124 gr GDHP using Unique powder, I also looked in my Lyman 50th and it shows 124 Gr. JHP using Unique powder & my Hodgdon 2022 shows 125 Gr. Sei (Sierra) JHP. Can I use any of these loads and why do they all have different Coals?. Speer shows a coal of 1.120, Lyman shows a coal of 1.075 and Hodgdon shows a coal of 1.090?????? Now you can see why I am confused!! Does it matter who makes the bullet as long as it is a Hollow Point bullet with the same grain weight? Would one grain weight, like 124 gr &125 gr make that much difference?? Thanks for unconfusing me.

 

[WrongHanded]

For a given bullet, the cartridge OAL will determine how much case capacity is available. The shorter the OAL, the deeper the bullet is seat. A bullet that is seated deeper reduces the case capacity remaining for the powder.

For a given charge weight of a given powder: the more the case volume, the lower the pressure. Conversely, the lower the case volume, the greater the pressure.

To make things more complicated, for a given OAL, a longer bullet will seat deeper and so reduce case capacity further. But you need an OAL that will both fit into your magazines, and also reliably chamber.

The first step would be to establish the OAL you want to use. To do this make a dummy cartridge (no primer or powder) and see if it plunks down into the barrel. To do this, remove the barrel from the gun and drop the dummy into it. It should make a "plunk" sound, and the case head should be flush with the breach end of the barrel. Them check to see if it fits in your magazine, and try cycling it into the chamber from the magazine. If this works, the OAL is not too long.

Then you can start working out the powder charge issue.

 

[Zahn]

OP, you are looking for the One True Answer. In reloading this doesn't exist. There are just too many variables to have a single reload recipe for a given caliber and bullet. There are differences large and small that affect all the variables that you are responsible for, and that's COAL and powder charge. This is exactly why you will hear over and over, start with an initial load and work up.

 

[Bfh_auto]

I have about 250 each RMR 9mm 124 Gr .JHP bullets and I want to load some 9mm with them. I have looked in my Speer #14 book and it shows 124 gr GDHP using Unique powder, I also looked in my Lyman 50th and it shows 124 Gr. JHP using Unique powder & my Hodgdon 2022 shows 125 Gr. Sei (Sierra) JHP. Can I use any of these loads and why do they all have different Coals?. Speer shows a coal of 1.120, Lyman shows a coal of 1.075 and Hodgdon shows a coal of 1.090?????? Now you can see why I am confused!! Does it matter who makes the bullet as long as it is a Hollow Point bullet with the same grain weight? Would one grain weight, like 124 gr &125 gr make that much difference?? Thanks for unconfusing me.

One thing to note is. The GDHP (gold dot hollow point) is a plated bullet. Not a jacketed one. This makes the charge weight different.
I generally use XTP data for XTPs. On others. I try to match profiles as closely as I can.
@WrongHanded explained the rest.

 

[nettlle]

Different COAL's are a nice option on auto loaders. If one COAL doesn't feed there are other options.

 

[WrongHanded]

One thing to note is. The GDHP (gold dot hollow point) is a plated bullet. Not a jacketed one. This makes the charge weight different.
I generally use XTP data for XTPs. On others. I try to match profiles as closely as I can.
@WrongHanded explained the rest.

I just learned something new. I didn't realize the Gold Dots were plated. I thought they were "bonded" somehow, but never considered the difference the construction would make to internal pressures.

 

[nettlle]

I shoot both reloaded 124 grn Gold Dots and 124 grn RMR MPR's. Same powder, primer, and CAOL. More reloading drama here than needed.

 

[Hugger-4641]

I find that RMR 124 jhp and 124 XTP are almost identical, Sierra jhp has a much different ogive and I have to load them shorter. I use 1.09 for the XTP/RMR only because my G3c is a little tight, Sierra Jhp has to be 1.06 or less. My Glock, Stoeger, and M9A3 will all take the XTP/RMR at 1.12

 

[GeoDudeFlorida]

It’s kind of funny - strange, not ha-ha - but I had a similar conversation with my father in law this evening about some Alberts swaged LSWC .45 200gr I gave him. I included the booklet that came with the bullets but their recommendation for seating and oal doesn’t work for his M&P. Works fine for his Colts Gold Cup, just not in the M&P. He’s going to try a slightly more aggressive crimp - right now he’s just closing the flare - and try that instead of seating deeper.
Sometimes you just have to stop and study the situation. Helps to have another brain to bounce ideas off of, too.

 

[AJC1]

Lead, plated. Coated and jacketed all have different load data. After you sort the functional oal then find a bullet of the same material. In small cases like 9 little changes make a big difference.

 

[Muddydogs]

Book COAL is just a guide and what the test barrel liked the best. Learn how to figure out your own COAL and work up your loads. The reason we work up our powder charge is we're not shooting the same firearm or test barrel that was used to create the load data and it's the same for COAL.

 

[GeoDudeFlorida]

Lead, plated. Coated and jacketed all have different load data. After you sort the functional oal then find a bullet of the same material. In small cases like 9 little changes make a big difference.

I think when you build experience it’s almost second nature to ignore the manufacturer recommended oal and just work it out on your own. But that takes a few years of trial and error and just a little more care than following a recipe. He’ll get there. Just takes time (and Hershey bars).
Edit: doh! Sorry, this was meant to be in response to @Muddydogs I agree with Muddydogs, just pointing out the OP is still new to all this.

 

[N555]

Manufacturer COAL is a good starting point.
I say always go longer if you can.
The main round you won't be able to go much longer on 380acp.

 

[chamokaneman]

You find the COAL that works in your weapon and start at the starting charge for your data. Just know that if your COAL is shorter that your data you may run into your max sooner than they did. On the other hand if you're longer you may get further/heavier. My shooting is mediocre enough that for everyday range blasters I can generally just stop at whatever cycles the gun OK, usually not much more than the starting load.

 

[lordpaxman]

Does it matter who makes the bullet as long as it is a Hollow Point bullet with the same grain weight? Would one grain weight, like 124 gr &125 gr make that much difference??

The bullet’s overall length combined with the cartridge overall length will determine the seating depth of the base of the bullet in the cartridge. That’s what’s really important, especially in a high pressure round like 9mm. While there may be many different COLs in published data for a given powder, there are an equal number of different min/max. Once you do your plunk test and determine your working COL, choose the published data that’s closest. If the published data COL is longer than what you can load, you’ll need to adjust the min charge down, how much will be a guess based on how much shorter your working COL is.
For my 9mm loading, I don’t consider the difference between 124 and 125 gr bullets to be significant. Good luck.

 

[mdi]

Determining OAL for an unlisted bullet can be frustrating, but K.I.S.S.! Overthinking about case capacity, bullet length, design, etc. will just drive you nuts. An example of my method; I found a bullet very close to my RMR JHPs, a Nosler was almost identical, so I used Nosler data with a workup starting from starting load data, and watching for high pressures. Using book OAL and the plunk test (if beginning OAL plunked OK sometimes I'd lengthen the cartridge a little and try that. I tested the OAL in my tightest chamber, Masada, and the round chambers easily in my 4 other 9mm pistols)

Way too much talk and speculation about "dangerous" short OAL, but not counting bullet setback from feeding, I don't remember any Kabooms from deeper seated bullets. Some of my experiments with some OALs up to .015" deeper than book data showed no difference in performance...

 

[jmorris]

Does it matter who makes the bullet as long as it is a Hollow Point bullet with the same grain weight?

Yes it can. A long/skinny JHP shape vs a short/fat one would have two different seating depths, despite identical weights, to have the same remaining internal case volume.

 

[.308 Norma]

^^^^ +1 Everything that mdi wrote.

Hollow Point bullet with the same grain weight? Would one grain weight, like 124 gr &125 gr make that much difference??

Naw, 1 grain difference in bullet weight isn't going to matter much if you, as others have said - start low and work up. And it's just grains, not "grain weight." I weigh a little over 200 pounds - not "a little over" 200 pound weight.
Edited to add: what jmorris wrote is also true. It can make a difference if the two bullets are different shapes. A JHP is typically longer than a bullet without a hollow point - it has to be if the two are the same diameter.

 

[jmorris]

Obviously incomplete information as we don’t know what combination they used and it’s likely worst case scenario but Speer did record a 34,000 cup INCREASE, from seating a bullet .030” deeper.



That could make for a bad day. Makes me cautious enough to generally find a number of sources for data.

 

[Hugger-4641]

Determining OAL for an unlisted bullet can be frustrating, but K.I.S.S.! Overthinking about case capacity, bullet length, design, etc. will just drive you nuts. An example of my method; I found a bullet very close to my RMR JHPs, a Nosler was almost identical, so I used Nosler data with a workup starting from starting load data, and watching for high pressures. Using book OAL and the plunk test (if beginning OAL plunked OK sometimes I'd lengthen the cartridge a little and try that. I tested the OAL in my tightest chamber, Masada, and the round chambers easily in my 4 other 9mm pistols)

Way too much talk and speculation about "dangerous" short OAL, but not counting bullet setback from feeding, I don't remember any Kabooms from deeper seated bullets. Some of my experiments with some OALs up to .015" deeper than book data showed no difference in performance...

I'm actually in the middle of a seating test with 9mm just for my own understanding . I'm not finished but I'm definitely seeing increased velocity as I shorten the OAL.
I'm using 6.4gr of HS-6 , 124 fmj , starting at 1.15 and I'm down to 1.045 using my 4" barreled STR9. I haven't crunched all the numbers yet, but it looks like every 0.030" shorter is increasing velocity about 15 to 30fps.
Started at 1160fps avg at 1.15 and I'm up to 1230fps avg at 1. 045, probably not going much further, I'm stopping at 1300 fps or 1.01, whichever comes first, if I don't see any other danger signs. Then I'm going to repeat the test in reverse order to confirm.

 

[.308 Norma]

it looks like every 0.030" shorter is increasing velocity about 15 to 30fps.
Started at 1160fps avg at 1.15 and I'm up to 1230fps avg at 1. 045, probably not going much further, I'm stopping at 1300 fps or 1.01, whichever comes first, if I don't see any other danger signs. Then I'm going to repeat the test in reverse order to confirm.

Interesting! Please post the results after you "repeat the test in reverse order."
Curious - are you seeing signs of increasing pressures? I'm not talking dangerous pressures - just "increasing" pressures as you shorten the OALs.

 

[lordpaxman]

I haven't crunched all the numbers yet, but it looks like every 0.030" shorter is increasing velocity about 15 to 30fps.

Keep in mind pressure signs in pistol, especially 9mm are often not seen until it’s too late. And you may be seeing a somewhat Linear V increase, but not all powders are well behaved. I have first hand experience with Titegroup, do not expect it to be linear especially with shorter COLs. It’s a good powder but in my book, not well behaved.

 

[Hugger-4641]

Keep in mind pressure signs in pistol, especially 9mm are often not seen until it’s too late. And you may be seeing a somewhat Linear V increase, but not all powders are well behaved. I have first hand experience with Titegroup, do not expect it to be linear especially with shorter COLs. It’s a good powder but in my book, not well behaved.

I haven't seen any primer flow or black around the cups yet, but I'm examining brass very closely with a 10x magnifier. That's one reason I'm using HS-6.
I've loaded it to 6.9gr before in a shorter barrel and I've previously loaded it to 1.045 with 6.4gr, so I'm fairly familiar with it's velocity curve in my guns. So far the velocity increase has been fairly linear, but now that I'm at 1.045, any shorter tests will be in 0.005 increments until I reach my previously mentioned limits. I will be looking closely at my graph for any change in the rate of increase and if I see it slope up or down any before I reach those limits, full stop. I'm also watching the sd and es for any swing.