CAS 357 Magnum load underperforms - Crimping issue or ??

[JimGnitecki]

Jim, With the low percent fill of your specific combination the pressure will not go up that much.

Cartridge          : .357 Magnum (SAAMI)
Bullet             : .358, 158, Hornady SWC 10408
Barrel Length      : 6.5 inch = 165.1 mm
Powder             : Hodgdon TiteGroup

Cartridge O.A.L. L6: 1.580 inch = 40.13 mm

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms
+00.0   34     4.00    896     281   16651   2157    100.0    0.890
+25.0   43     5.00   1022     367   24635   2622    100.0    0.744


Cartridge O.A.L. L6: 1.517 inch = 38.53 mm

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

+00.0   38     4.00    917     295   18869   2097    100.0    0.850
+25.0   48     5.00   1046     384   28182   2544    100.0    0.711

Wow, that IS a very modest peak pressure increase, from 16651 psi to 18869 psi (only 13% increase), which is still far short of the psi a REAL 357 Magnum cartridge develops.

This is also something i could try while waiting for my larger diameter powder station expander funnel and the Lee Factory Crimp die.

Another potential advantage is that it will likely raise the muzzle velocity a bit, which gives me a new additional data point to supplement the recent ladder test.

Thank-you, P Flados!

Note that the muzzle velocity in the above Quick Load simulation dony P Flados for my benefit is far higher than my actual. This simulation says that at 4.0g of TiteGroup, with a 6.5" barrel, QL says I would get 896 fps. But with my 4.75" barrel, admittedly sorter, I actually consistently get an average of 770 fps. QL also says that the muzzle velocity will increase only from 896 to 917 fps. So, no danger of driving that swaged bullet too fast and encountering leading.

Jim G

 

[JimGnitecki]

While waiting for my new UniqueTek powder station expander funnel that replaces the Dillon one to arrive, I have been doing more Googling at multiple handloading forums, and have found a very broad consensus at the forums that have a lot unjacketed lead bullet handloaders, that the combination of the Dillon sizing die and the Dillon powder station expander funnel is a bad combo for unjacketed lead bullets. This echoes what some of you have told me on this thread.

Apparently, the Dillon philosophy is to size down the case aggressively (just as i have found via measuring my own sized cases), and then to expand the case mouth, just below the belling (flaring) portion to an ID that will grab and hold a jacketed bullet at the seating station.

Unfortunately, since both bullets loaded these days on progressive Dillon presses are jacketed, the Dillon expander is sized to make case ID ideal for jacketed bullets. But unjacketed lead bullets are normally supposed to be slightly larger in diameter for decent accuracy and minimized leading of the barrel. So, the Dillon expander produces a case ID that swages the unjacketed larger diameter bullet down too much for good accuracy.

Naturally, the first folks to learn this were the Bullseye shooters. For many IPSC shooters, the slightly impaired accuracy apparently wasn't an issue, and many CAS shooters probably would not notice the worse accuracy at all, as the target ranges are so short and the expectations for old west revolver accuracy is so low.

The UniqueTek expander funnel made specifically for the Dillon solves this problem for many folks. It gets a lot opf rave reviews.

We'll see.

Jim G

 

[P Flados]

Jim, The Quickload "barrel length" is muzzle to breech. So for a revolver, it includes barrel + cylinder. The velocities posted also are not adjusted to reflect cylinder gap losses (I typically assume 50 fps).

As previously noted, your measured velocities are less than expected. This could be due to one or more of: measurement error, extra cylinder gap losses, blow-by due to undersized bullet, under-performance of your batch of powder or just something weird about your guns (less likely as are using 2 guns for testing).

 

[JimGnitecki]

Jim, The Quickload "barrel length" is muzzle to breech. So for a revolver, it includes barrel + cylinder. The velocities posted also are not adjusted to reflect cylinder gap losses (I typically assume 50 fps).

As previously noted, your measured velocities are less than expected. This could be due to one or more of: measurement error, extra cylinder gap losses, blow-by due to undersized bullet, under-performance of your batch of powder or just something weird about your guns (less likely as are using 2 guns for testing).

Yes, thanks for the reminder on the Quick Load results including chamber length in the barrel length. For the other points:
- The Labradar is accurate to 0.1% velocity
- My cylinder gaps are .006" on both revolvers

I do think that blow-by may well be the culprit, despite my not getting leading of the barrels. No kidding, a quick bore brushing and 2 or 3 cleaning patches gets the barrels mirror-like.

Jim G

 

[JimGnitecki]

It WAS the Hornady no. 10408 swaged bullet that was the problem:

I had no choice but to do a deep dive after those Hornady no. 10408 158g swaged bullets were such a disappointment and disaster. As fellow reloaders, you might find it interesting that after changing to a 130g bullet, and NOT changing the expander funnel or the seating die, the OD of the top portion of the loaded cases (i.e. the portion that contacts the bullet shank) changed from .375" OD to .378"OD!

The Hornady bullet WAS actually being re-swaged by the case when seated into the case! It started at .3578" OD and ended up at .355" OD (The actual measured case walls are in fact just a tiny bit over .010", so this makes sense). I know this because I pulled a couple of the Hornady bullets from the cases after seating and measured them.

The .378" seated OD with the 130g bullets males sense, since those bullets are .358" OD. 358" plus 2x the case thickness = .378". THOSE bullets are RESISTING as they are pushed into the cases, and it is the CASE brass that is stretching, not the bullet compressing, and this is what we want with an unjacketed lead bullet.

Those swaged Hornady bullets, which apparently have a BHN of 5, are simply not loadable for decent accuracy in a .357 Magnum firearm unless you use an oversized expander funnel like the UniqueTek, that prevents the need for them to be swaged down to fit inside the case. I had already ordered the UniqueTek funnel, and it in fact arrived today. But if I had realized what was happening with the Hornady swaged bullets earlier in the effort to get them to shoot consistently, I should just have abandoned them and gone to the cast bullets sooner.

Live and learn.

Jim G