Walther PDP reloading observation...Seems to be an odd chamber size

[chutestrate]

I have cast a bunch of TLC-356-124-TC bullets. I have loaded a lot of these for my various 9's with good results, beretta, sigs, hk's... I got a strange result when I did a plunk test. I'm using hodgdon data for Titegroup which is 4 gr with a COAL of 1.125. The cartridge sat well above the hood of the barrel dropping in a test cartridge. I then sized case, and it dropped in correctly and sat flush with the hood as expected. I started pushing in the bullet little by little. The bullet finally seated correctly, but I don't think I want to use these bullets even backing down the powder charge to the minimum. I also took loaded a 1.125 cartridge, closed the slide, and then measured. It had pushed the bullet into the case a little ways. I had some 124 gr round nose I had reloaded to the same 1.125 coal, and they dropped in just fine, but the coal was 1.115. I don't like that.

I think I'm going to need to cast some round nose bullets for this pistola. The TC shaped bullets definitely don't seem to fit well.

The Walther PDP is a really nice piece by the way.

[Recycled bullet]

IF the slide closing is telescoping your ammunition shorter, THEN your pressures will rise unpredictably as the internal cartridge case volume becomes smaller.

Why not just make a small batch of ammunition specific for that handgun test it see if the reward is worth the work, maybe it is, test that ammo and other pistols maybe you have a new accuracy load?

I cast load and shoot MP molds 124 grain hollow points at 1.08 overall length in all of my 9mm handguns because that is the length requirement for the ammunition to fit in my czpo9 which has a very short throat.

I'm getting ready to start loading some subsonic 145 grain hollow points and I will adjust the powder charge and overall length as needed to fit and cycle the po9 then I will test it in all the other pistols and see if it works and if it does not require any further adjustment that's great!

[rsrocket1]

The Walther PDP uses what's called a stepped chamber. That's where the first few 10ths of an inch are within SAAMI limits but does not follow a straight line from the case head to the case rim and is narrower than your usual fired 9mm brass. This keeps the case mouth from expanding the same way most other 9mm cases expand. It keeps pressures slightly higher and gives bullets a slightly higher velocity by sealing providing a better gas seal. It was invented by Luger. himself When you shoot a cartridge in a stepped chamber, you'll see a ring indented at the front of the case.

0.355 jacketed and plated bullets will have no problem chambering in the gun. Fat cast bullets could have problems with the plunk test. While I don't usually recommend the use, the Lee Factory Crimp Die will iron out bulges caused by loading 0.356" bullets for the PDP. Even though Walther does not recommend lead bullets with their polygonal barrel just like Glock, I've found no problems with my powder coated Lee 356-120-TC and TL356-124-R bullets in my 4" PDP Compact as well as Extreme 124g and 147g plated bullets.

You must definitely not allow a flared case without at least a taper crimp to close the flare and use calipers to see how much bulge your bullets put onto the case versus a newly sized case that easily passes the plunk tes.t

[chutestrate]

Thank you nothing is flared. I used the Lee Taper crimp die on these. If the chamber is stepped then that could explain it. I forgot to mention that I size my bullets to 358 as well. That may contribute to what is happening as well.

[Handloader109]

I have a bad problem, I have cast about 6 different boolits for my 9mm guns. And I had issues that I seemed not to totally resolve with feeding. About 2 odd years ago, I bought an Armanov 9mm ammo checker. It will hold and allow you to check 100 rounds at a time for proper crimp and length. It totally has solved my issues as I check the first round and then every hundred I load. And they fit and load in all my guns. It It fits and is smooth across the top It loads

Sent from my SM-S908U using Tapatalk

[rsrocket1]

Thank you nothing is flared. I used the Lee Taper crimp die on these. If the chamber is stepped then that could explain it. I forgot to mention that I size my bullets to 358 as well. That may contribute to what is happening as well.

Measure the diameter of the case mouth with a bullet loaded vs. a sized but unloaded case and you’ll see how much the bullet bulges the brass. I usually size my pc bullets to .358” also in order to give me the option to use them in my .357 Mag revolver but I also have a Lee 0.356” push through sizer die that I use when I know they will be used exclusively in 9mm guns.

[charlie b]

Do you have a picture of fired cases? I think my HK VP9 may be like this as well.

PS after some research in the Luger forums I do have a stepped chamber. Seems Walther, HK and some others have started cutting this chamber again. Seems it was the original chamber design by Luger. The reason for the step is not clear. Better sealing, accuracy, delayed extraction, easier to make reamers, etc, etc. The end result is those guns may not chamber some ammunition. Mine does fine with reloads from Lee dies as well as cheap Rem and Win ammo.

[ioon44]

Thank you nothing is flared. I used the Lee Taper crimp die on these. If the chamber is stepped then that could explain it. I forgot to mention that I size my bullets to 358 as well. That may contribute to what is happening as well.

Have you pulled any of your .358" bullets after using the Lee Taper crimp die to see what they measure?

I have a PDP and use .358" TC bullets coated with Hi-Tek, my 140gr from an Accurate 140z mold has to be seated to 1.025" with reduced powder charge and my alloy is around 11BHN.

I use Hornady dies with Hornady taper crimp die set to just straighten out the bell of the case mouth, the stepped chamber does not have any problems feeding my loads, the PDP is very accurate and fun to shoot.

[reddog81]

OAL in the 1.08 to 1.1” range are common with TC bullets. RN and TC bullets will not and should not have the same OAL.

[chutestrate]

OAL in the 1.08 to 1.1” range are common with TC bullets. RN and TC bullets will not and should not have the same OAL.

Since tc bullets are longer I would think they would have a longer coal instead of being shorter.