Optimal 9mm OAL for Reliability?

[37th Mass]

The maximum allowable Cartridge Over-All Length for the 9mm is 1.169". Some reloading manuals list the minimum Over-All Length for different loads, e.g., 1.100" for a 124 grain Jacketed Bullet when using Accurate #2 powder, according to my Lee manual. I would think that you could safely load the cartridge longer than that, up to the 1.169" maximum.

Is there an optimal length of a 9mm cartridge for reliable feeding in semi-autos? Does it vary with brand/type of pistol?

[the_t0ny]

It’ll vary from pistol to pistol but I’ve noticed I get the best reliability loading to 1.150” overall length using 124gr xtreme RN, blue bullet 125gr RN, blue bullet 135gr RN-TC, and RMR bullets 124gr FMJ-FP. Even at 1.150” all these will feed in my CZ pistols as well. The only projectile I loaded shorter were the RMR bullets 135gr FMJ-FP which had to be loaded to 1.100” OAL in order to feed in my CZ’s. I also recall seeing on my chip McCormick magazine packaging for 9mm 1911’s that to facilitate the best feeding, they recommended an overall length of 1.150”.

[37th Mass]

Deleted

[Skinner Precision, LLC]

The throat of the reamer used to chamber the barrel can be one of the biggest variables in OAL, the internal dimensions of a gun's magazine can also be a variable that affects OAL.

There are other variables but those are two of the biggest...

[358156hp]

Bullet design is a huge factor as well. Not all bullets of seemingly identical design are actually identical. The best-known example of this is probably the lowly 9mm round nose bullets. Some are larger, or smaller than others, and the profile is nowhere near the same, or even similar when inspected closely. Some 9mm bullets won't even chamber in some barrels reliably or consistently because of this, and can tie the pistol up pretty good. Sometimes (often) it is caused by the barrel being throated incorrectly, and a trip to a gunsmith with a throating reamer is required. Sometimes you can get away with simply trying a different brand of ammo, but that's not a real solution these days. What if that ammo is all you can get locally?

Lots to think about.

[revchuck38]

IME, most FMJ-RNs work at 1.13-1.15". FPs vary enough that they need to be loaded to suit your barrel. I recently got some "no lube groove" RN cast bullets that need to be seated deeper than the FMJs, though I haven't settled on an OAL yet. I've still got about 3k FMJs to load before I worry about them.

[Artemas2]

Pretty much chamber and magazine dependent. I have heads from the same manufacturer go 1.130 in one gun to 1.080 in another. I don't have a single gun that comes even close to allowing a 1.169

I am not going to suggest deviating from what da book says, however keep in mind many of those numbers are for using specific powder charges and using all new high quality components with near fantasy land requirements in laboratory settings.

[willie]

Within reason OAL's are nominal meaning they are not biblical dictates. CZ's have the shortest throats that I know of. Once you stray from round nose bullets and 115-125 gr bullets, bullet shape and chamber dimensions become factors. Of course, magazine dimensions can be a variable. In high pressure rounds like 9mm seating bullets too deep will raise pressure. This statement is true for any cartridge but becomes a bigger deal with high pressure calibers. Sometimes adjusting .002 either direction will resolve feeding issues.

[ECK]

I load 9mm for a variety of guns ranging from CZ’s to PCC to 1911/2011’s, and recently added a Beretta to the collection. I settled on 1.125” OAL as a length that worked on all the guns, mostly loading 135 gr Hy-teck coated bullets. When I was just loading for my 1911/2011’s I used 1.140”, but several years ago when I got into CZs I had to shorten up the OAL.

Last summer my usual supplier was backordered on 135s so I resorted to getting a case of 125’s with the same Hy-tek coating. I found out that the 125’s must have a slightly fatter ogive than the 135s because I had to shorten them down to 1.090” to chamber in my CZs (Shadow 2 and P10C).

I’m down to the last of the 125s and have since replenished my supply of 135s. Once I make the switch back I’m reverting back to 1.125” OAL.

[Pistol Pete 10]

Different bullets require different overall lengths do the shape. I recently bought some coated bullets and they are more blunt than normal 124/115 bullets, have to seat them deeper, makes OL shorter than normal. Make sure to plunk test in your gun/guns. My Dan Wesson will take longer bullets than my G19 or S&W EZ.