I'm new to reloading semiautomatic rounds (I've reloaded only .38 Special in the past) and I want to get it right as I understand that seating 9mm bullets too far in their cases can produce dangerous pressures.

I understand that 1.169" is the maximum length for 9mm rounds without reference to bullet type or weight. Is there a safe minimum length?

I'm loading 147 grain FMJ bullets (with a flat head) from Montana Gold. (If its relevant, I am starting out using 5 grains of HS-6 powder.)

Using a dial calipers, the flat headed 147 grain FACTORY loads I have measure out at 1.062".

My reloading manuals list between 1.100" (Hornady) and 1.130" (Speer) for length of flat headed FMJ rounds using 147 grain bullets. (The Lyman manual is right between these two.)

Is there any reason to seat bullets at anything under the lengths in the manuals? I ask because the bullets in my factory loads are seated more deeply.

Yes 1.169" is the max but a lot of pistols will not function with that long of a loading.
A 95gr FMJ at a OAL of just 1.005" might not work in others due to feeding problems.

Each weapon is different.
A 147 Speer TMJ at 1.165" worked in m C9 but not a members 3" Kahr.
My Radom hated bullets that were smaller than a 115gr Ball ammo.
Some manuals list the long 1.169" in their loading data, while
others start out with the minimum OAL, which I think is best, for loaders.

Just never use more powder that is listed for the "short" OAL in manuals and you will be ok.
Plus if your weapon is new...............
it needs 200 rounds to break it in to where it will smooth out all the metal and working parts. Don't forget oil or grease if needed.

Is 5 grains the starting load listed for a 147-gr jacketed bullet? I ask because I just glanced at Hodgdon's online data (not gonna go two floors down to the basement and back up for my manuals) and they list 5 grains of HS-6 as a maximum.

Bullets over 124/125 grains are generally the ones that are easy to seat so deeply. That's a big ol' bullet to try and squeeze in.

I would use starting data, and load on the long side. Start off with just 10--if they work, great. If not, adjust accordingly.

As for the 147gr FN bullet............

I use the 158gr Speer TMJ that has a very slight FN design.
Speer calls out for a minimum of 1.13" for this bullet, also the Gold Dot, in its manual.

In my 3.5" C9 pistol , I load the 147gr at 1.165" OAL with 5.0grs of HS-6
and get a fps of 805 and it strikes at point of aim for a nice beginning load.
My lowest with this powder hit 777fps but I want a minimum of 800fps to prevent squibs.
Plus several powders did well in the accuracy level with a 800fps or faster, in my pistol.

At the 1.13" length, 975fps is doable but at full strength for my weapon.

Safe loading.

Thank you for the advice! I will start out with the minimum OALs and see how they feed. I imagine that this will not present problems, as my Glock 19 has never had a problem feeding anything!

If you wish to be certain, ask the manufacturer of the bullet you plan to use what their recommended AOL is. Problem solved.

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So many S&W's, so few funds!!

Make some dummy rounds, resize and seat a bullet , no primer , no powder. load them into magazine , rack the slide and let it go feeding the round from magazine into chamber. Do this with 4 or 5 dummies. If they feed , extract and eject...your OK. If they hang up, seat the bullets a little deeper and try again. Once you have determined the length your gun likes keep a few for future die adjustment. Using the dummy is a faster way to set seating die next time.
Gary

Anytime I am trying out a new load this is exactly what I do and it works quite well. Saves time later on and it's safe.

I also do dummy rounds when I'm trying out a new bullet. But, I go mostly on the plunk test to decide on OAL. I do the function test with live rounds, at the range. I've never thought that hand-schucking rounds was a good way to test gun function. Sure, it will tell you some of what you want to know. But, shooting live rounds will tell you all you need to know.

OAL is ALWAYS gun & bullet specific. Unless you are loading nearly identical bullets, the OAL will be diff. Load to the longest OAL your gun will accept, regardless of data.

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NRA Cert. Inst. IDPA CSO

The industry minimum for function of the 9mm Luger is 1" exactly. Don't expect shorter bullets to feed and operate correctly.

However the MINIMUM for a particular bullet and powder combination is derived only by testing and resulting data. The length shown in the table should be considered minimum. You are free to extend the length but not compress it.

As long as the weight, material, construction and the diameter of the bullets are the same, I consider them to be equal or at least of insignificant to the overall length.

In other words, a 125 grain JHP, is about the same as any other , until you get near maximum loads Those should be worked up carefully. Differences such as bullet hardness, type of primer and barrel bore diameter can affect what the max load should be for THAT gun.

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"He was kinda funny lookin'"

Well, I took the dummy round route and found that rounds with an OAL of 1.115 won't feed in any of my guns, but that 1.130 will feed just fine. I'm traveling right now but when I get back home, I'll load some live rounds and see what happens.

9mm is a high pressure handgun round and 147 is the largest bullet with much published reloading data. Starting at the shortest OAL possible is not a good idea. Start at the longest OAL and figure out how short you need to make them so they function.

Re: "I load the Lee 105 grain SWC to 0.75" There is no way .75 is correct. The trim to length of a 9mm case is .751. An OAL of .75 would mean the whole bullet is buried inside the case.

You are so right , I didn't read the calipers correctly , it should be 1.075". What was I thinking !
Thanks for the correction.
Gary

+1 with post ten;

Not only is pressure lower with a long OAL but.........

most pistols will shoot better with the longer OAL due to less
"Bullet jump" to the lands and rifling in the barrel.

My 115 and 124gr plated both do better with a maximum oal in
light target loads as well as my 147gr bullets.