Seating depth vs adding powder

[Goesfaster]

9mm 124g powdercoat
Red dot powder CCI SPP
4.3g COAL 1.15
S&W Shield

Max powder charge is 4.5

Feeding is fine, but last round does not hold open the action. Cases show a little black residue(possible low pressure sign).

Question is, which path is safest to get this load to hold open on last round? Shorter OAL or more powder?

[noylj]

I always go to a bit more powder.
I haven't seen that a small change in COL does much for pressure/velocity and too short a COL can cause feeding problems.
Both can be "safe," but you already have more than enough signs that your pressure is too low.
I want to be in the COL range that feeds and chambers 100% and adjust pressure using powder. Another 0.2-0.3 grains of powder is the way I would go.

[JMP]

For me, 9mm is one of those cartridges for which I have a number of chambers. As I do not like having different loads for each gun, I'll generally set the length to be the longest that fits in my shortest chamber (that's usually a CZ or a Sig for more people). Then, find a load that works for all your guns. With 9mm, most of the data is on the light side for my liking. But, it's a personal judgement. Of course, I am not a good pistol shooter so I don't really notice much difference if I try to make a one size fits all 9mm cartridge.

[HTLP]

I load my 124gn 9mm plated RN to 1.15" OAL. I would say up your powder charge but really I would switch to a different powder, I don't see Red Dot listed for 9mm loads in my books nor in the Alliant load data listed online. Where did you find the load data you are using? "Max powder charge is 4.5"? If you choose to switch powders I suggest TiteGroup if you can find it.

[bsumoba]

red dot is a fairly fast powder for 124s. that fast powder will a heavier bullet will create higher pressures faster as you go up in charge. at some point, you will start seeing pressures, yet the velocities are still on the low side.

that being said, for 124s, go to something like unique, titegroup, W231, HP38, power pistol or something along the same lines in that powder burn rate range.

for the COAL, I am in the same boat as JMP. I find the COAL that fits in the shortest chamber.

I don't shoot much pistol either so me trying to get tight groups is not a big requirement. I just need it to go bang every time and give me reasonable accuracy.

[Goesfaster]

Thanks for the info guys. I will keep you informed on progress.

[Metal God]

Although not the same caliber , I'm having the same issue in 45 using CFE pistol and 200gr XTP . None of the charges burned clean and left soot on the cases all the way thru min to max 6.3gr to 7.2gr . Suggested COAL is 1.210 but I had mine seated to 1.240 . I went ahead and loaded more up through out the min to max charges but this time seated them .020 deeper to 1.220 . I'll be testing them some time this week . I'll let you know how that goes .

[M27]

soot on the exterior of the case can be a sign of low pressure but it is not a "100% of the time" type of thing

I have seen it common that some reloaders under power their ammo sometimes in fear of a kaboom. Being a conservative reloader when it comes to powder is not a bad thing. Along with the powder charge you may want to look at

neck tension
While 9mm often needs no crimp, sometimes a little taper crimp can help. What brass are you using? I have seen that the .FC. brass is really thin and does not provide the best neck tension.

I load 9mm with extreme 124gn rn, because of the rounded base I can get away with out belling the cases. I have not loaded PC bullets yet but I assume the PC is a little on the soft side so you must bell. Are you crimping enough? With a little more crimp the brass will hold the bullet a little longer, and allow case pressure to get higher and blow out to the chamber walls before the bullet starts its way down the barrel.

over sized
I have noticed that some dies under size the brass a bit. While I have not seen this with 9mm, I have seen it with straight wall revolver calibers. Most likely not your problem but thought I couldn't hurt to throw it out there. Have you tried a different manufactures dies?

Magnum primers
you will have to start a whole new load work up but sometimes magnum primers can help the powder get burning quicker and help blow the case out to the chamber walls and get a better pressure spike before the bullet starts moving down the barrel

last round hold open
Does the slide lock open on the last round with factory ammo? If not, it is probably a mag problem or user error. Does your thumb ride the slide stop when shooting? Does it do it with all mags?

Also how many rounds does your pistol have through it, is it broken in or does it need new springs?

as far as your real question "Question is, which path is safest to get this load to hold open on last round? Shorter OAL or more powder?". I would increase powder since you already have an OAL that is reliable. You would not want to go too short and end up with jams. And depending on what you are doing for crimp I might crimp a little more.

I hope my ramble has been helpful and good luck.

[rsrocket1]

I load powder coated Lee 356-120-TC and TL356-124-2R's using all sorts of powder. I have an 8 pound jug of Red Dot so I would like to use it as much as possible although it is about the fastest powder I would want to use in 9mm. 4.3g is a really hot load. I haven't gone above 4.0g and with the bullet seated to 1.17", I was averaging 983 fps out of the Shield and 1068 fps out of the M&P 9 with the 4.25" barrel. Yes, I also got some soot on the cases, but I don't think it's the same cause as it would be from a really low pressure load. Quickload tells me that I am right around 35,000 psi peak pressure with my load so I don't want to go any higher than that. I get strong case ejections and lock back after the last round on both guns.

My M&P is actually an M&P40 and I use a 9mm barrel. The gun shoots great with the barrel, but the slide is heavier and I need full power 9mm loads, otherwise I get cases flying up only about a foot and some end up hitting my face or landing on my head so low recoil 9mm is fun to shoot but sometimes annoying.

As you know, the Shield has a really stiff recoil spring and is "flippier" than a full size gun. If you are experiencing stovepipes and/or failures to lock back, try shooting with only a couple rounds in the magazine with a "death grip" maybe even on a bench. I know that is not good shooting practice, but it will tell you if it's the gun, the load or your grip that is causing the problem.

In any case, I think you are near or at the limit with Red Dot for 9mm. You might be able to seat the bullet longer and increase the charge by 0.1-0.2g but you definitely don't want to seat it deeper. If you really need more speed to help reliable cycling, go with a slower powder like Unique, Power Pistol or BE-86 if you can find any of these nowadays.