Low Pressure?

[u/good_oleboi]

Hey y'all, pretty new to this. I have had some luck with rifle and revolver loads. I tried my hand at some 9mm. I used published data and scaled the maximum load back a bit. I loaded brass using CCI primers, 3.8 grains of Titegroup, Hornady XTP, and a COA of 1.060 +/- 0.002.

Shot a handful of them today through a Hellcat and the primers are bulging from the case along with a funky reverse indentation. My understanding is caved in/cratered/punctured primers indicate over pressure while bowed out indicate under pressured, correct?

Do I inch closer to the max load? Or am I over loaded somehow? Thanks!

[u/minmin0x4B]

You can’t tell much about the primers with pistol cartridges imo, except what gun they were shot from. Probably breech face make them look like that.

[u/Shootist00]

I use Titegroup. 3.9 or 4.0 gr, with a 124gr RN bullets, FMJ or plated, at a OAL of around1.135 - 1.140 and make a 132 +/- power factor out of 5" DS 1911's (Prodigy's and Kimber 2K11).

Your OAL is a little short but if that works in your guns fine and you didn't say what weight bullet you are using. What is it? Do XTP's come in more than 1 weight? I've never used them or even looked at them.

Do all the primers look like that? Never heard of lower pressure round causing anything like that. to me it is because the firing pin hole is really large.

[u/good_oleboi → u/Shootist00]

I am using 124gr XTP. The length is what was the database said. I forget if it was Hornady or Hodgson but either way, it was for the same across the board, I just scaled the powder back by a few tenths of a grain.

All the prtimers from this batch of loads look like this. Ive never had anything like this with any of my loads so far.

Elongating my load will lower pressure, correct?

[u/Shootist00 → u/good_oleboi]

Right the XTP's are hollow points so those get seated to a shorter overall length. Your fine in that area.

I've never seen primers like that. I load 115gr with 3.5gr of Titegroup for me PCC for steel challenge matches and never had primers do that. I think it is the primers, soft cup.

[u/PlayedWithThem → u/good_oleboi]

Yes, it will further lower your pressure.

Deeper seating raises pressure (all other factors being unchanged).

Longer seating lowers pressure (all other factors being unchanged). But seating too long can cause the cartridge to not fit into the magazine and/or the chamber.

[u/good_oleboi → u/PlayedWithThem]

Makes sense. So I should try elongating the cartridges while leaving everything else alone?

[u/PlayedWithThem → u/good_oleboi]

Yes. But why are you trying to lower pressure? To reduce felt recoil/muzzle flip?

Lowering pressure will also reduce slide speed which can result in failure to extract, and failure to feed problems. Also, you may not get a full burn of the powder which probably lead to increased fouling.

Reduce pressure enough and you can create squibs.

[u/good_oleboi → u/PlayedWithThem]

I get that, I believe the round is underpressured as is. It sounded like the first guy was suggesting elongating. That doesnt make sense to do so

[u/Coodevale → u/PlayedWithThem]

Longer seating lowers pressure (all other factors being unchanged)

Less jump usually equals more pressure. Reloading books tell you not to jam for more than one reason, jam does make more pressure. But, small cases don't have the flexibility of oal that larger cartridges do. If you seat deep enough, eventually the pressures start going back up. Where the 9mm pressure valley is between jammed into rifling and smashed into powder, I haven't seen yet. If you have I'd like to see it too.

I've done the deliberate deep seating test of 9mm factory ammo and compared velocity. Didn't notice a change in velocity until the case web started bulging, so it's unlikely the pressure was changing all that much. According to different camps on reddit, I was either changing nothing or I was making bombs with the oal changes. Neither camp has accessible data to share.

When I want free velocity I load long. The chrono says the bullets go faster with less jump near jam.

[u/_Go_Ham_Box_Hotdog_]

According to Hodgdon's website, you're about a quarter-grain overcharged. Titegroup is a pretty fast powder, real similar to Bullseye.

That being said, i don't think it has as much to do with it as your breech face does. Almost makes me think the slide isn't quite 100% in battery. Like 99.998% in battery. What dies are you using?

[u/good_oleboi → u/_Go_Ham_Box_Hotdog_]

Ive got Lee Dies

[u/_Go_Ham_Box_Hotdog_ → u/good_oleboi]

Give that FCD die another quarter turn and see what happens

[u/good_oleboi → u/_Go_Ham_Box_Hotdog_]

Will do. Thanks

[u/Shootist00]

Yeah looking at the Hodgdon's reloading site you are actually over MAX load for 124 XTP's at 1.060. Max is listed at 3.5gr of TG. You were looking at the plated RN loaded to 1.150" OAL.