Home Forums Reloading Handgun Reloading Reloading 357Mag w/ Power Pro 300-MP

My post was all about SAAMI specs being worthless compared to what can ACTUALLY be done with the cartridge. You are arguing with a scientist, by the way, which is only going to make you look ignorant.

Pressure limits are all about brass dimensions, action steel dimensions, and strength of locking mechanisms. If one understands some basics about all of these, one can handload above "dummy light" specs and be completely safe. In my experience, handloaders used to be a bunch of curious experimenters who wanted to understand the limitations of their equipment. Now it seems like the bulk of them have become nannying bitches who want to be protected by some "official".

The data for all platforms in 357 Mag are all the same. That said, if one compares the steel of the action/chamber of a lever gun in 357 to the weakest revolver chambered in same cartridge, then looks at the back-thrust force on the 357 lever action compared to bigger cartridges based on the same platform, one comes to the conclusion that one can safely step well above SAAMI-spec data and be nowhere near any red line. The same holds true exactly for the Contender platform. Lots of chamber steel, and the locking mechanism is designed to handle back thrust at much higher pressures for same cartridge dimension, or same pressures for much larger cylinder. Thus, Contenders will easily digest scorching loads in 357.

I don't recommend anyone try to step above the reloading data unless they understand all of what I have only named here, but not described in any detail. What I am trying to say, in layman's terms, is that every platform has its limitations, but that some have far fewer than others. In the case of relatively small-bore revolver cartridges, many lever guns and all Contenders are designed to handle pressures far beyond what is safe in the relatively weak mechanisms found on some revolvers. If you understand this, and understand the burn curves of the powers you are using (through much experimentation), you can safely exceed the data for the 357 in strong platforms. The brass will not even be phased.

Again, this isn't a license to fill a case with a high-intensity, fast-burning powder, then stick a big bullet on top, thinking that your gun can handle whatever. And in reality, those of us who don't have access to calibrated testing equipment have no idea what pressures we are running with our ammo. It could be that our "hot" loads are actually within or close to SAAMI spec in our guns, or it could be that book loads that we imagine are safe are well above SAAMI spec in our guns.

Following the "rules" doesn't guarantee that nothing will go wrong, and stepping outside the "rules" does not guarantee that one is actually incurring any additional risk.

Scientist or not and certainly not worried about looking ignorant the thing is SAAMI Specs say one reading for CUP and another in PSI.
We aren't worried about converting the two. Who cares anyway?
We all know anyone can load above SAAMI Specs. That isnt anything new. We are individuals. We can choose to do whatever we want as long as it doesnt hurt anyone else.
I know I do.

Well, for a while I did. I have a wonderful old milsurp Swede, and I have pressure measuring equipment. I needed to know a reasonable limit for loads for it. Turns out it is about 52 KPSI. The conversion came in handy for that and a couple of other special situations. A few years after I came up with my conversion, I was delighted to find that Dr. Floyd Brownell had done the same thing a few decades earlier.



Got a mouse in your pocket?

You are entirely welcome. Glad to be of assistance.

Just for everybody's reference, the conversion holds for rifle cartridges from 35 KPSI to 62 KPSI, and is within plus or minus 1 KPSI in the middle of the range, and plus or minus 2 KPSI at the ends. That's better precision than you'll get out of copper crusher, and about as good as you'll get out of piezo or strain equipment.

Well, my mouse and I appreciated your well thought out and designed answer. The precision of any test is dependant mostly on the tech or doofus that is conducting it.
Still this isnt about your knowledge but about what SAAMI Specs says. Accurate or not. What you, me or anyone else does with it is up to them.
But, what SAAMI Specs says is what SAAMI Spec says. Dont need a conversion theory for that.

I knew there must be a reason I was enjoying your posts so much!

Yes, the gas cannot read the headstamp. All it "knows" is how much brass and steel is between it and the outside world, and what the geometry is. In modern actions, I load my 7x57 and my modern 6.5x55 to about 58-59 KPSI.

SAAMI specs were created so that ammunition made to them will be work and be safe in practically all firearms.

Most of us know SAAMI Specs are designed to accommodate the weakest link in the chain.. This is nothing new. But what SAAMI Specs says is what they say. Regardless what it is based on.
Still the individual is the guiding light of his destination on his load developement. Load data is just a guide. The individual can choose to follow it or not.
Still SAAMI Specs has their rules and ways of doing things.

Now that we're all in agreement...my favorite load in 357 for SERIOUS business is a NOE mould-cast 230 gr WLN designed for rifle rounds that I seat to give about .01" clearance from cylinder face in RBH and crimp with Lee FCD over 12 grains 110/296 in non-Winchester brass using CCI550's. It is just barely subsonic, near 1100, and hits harder than anything I've ever seen from a 357 handgun. It doesn't feed in unaltered lever guns, though.

If I owned a contender in 357(which, due to their horrible chamber reamers, use what amounts to a forcing cone-style throat), I'd load the biggest bullets I desired to the longest length that would still chamber easily, FCD them there, and fill up the empty space in the case with 110/296, or Lil Gun, or 300-MP. I tried this in 44 mag 10" Contender using 300gr cast bullets, and got FAR more velocity and recoil than I wanted to, but it should work pretty slick in a 357. I could get 24 gr 110/296 easily into the 44 mag case, seating at 1.8". They weren't fun to shoot. Consequently, I filed the feed ramp stop back on a 44 Marlin and can shoot 1.78" cartridges, which allows 22gr of 110/296 behind a 300 or 23 behind a 285. Those are good times. I hope the OP has some good times with his project.

Well last night I picked up a pound of 300MP loaded up 3 each at 16.0, 16.5, and 17.0 gr with 158gr Hornady XTP HPs, CCI 550's per Hornady Manual. Shot them this morning. Stout but no obvious pressure signs. 16.0's got around 1425, 16.5 around 1450 and 17 about 1500 fps. Was hard to tell exactly because the damn wind was blowing about 25mph and I don't think I was perfectly aligned with my chronograph. I think if I get aligned better that the velocities will be higher. (I shot a couple of my standard 14.5gr IMR 4227/158gr and was 100fps off of normal.) I was only shooting 25 yards due to wind. All 3 groups were quarter size or less, one group all touching - the others 2 would touch and one stray. Think I'll load a few more in the 16.5gr-17gr range and try them again on a nicer day.

FWIW: I have a box of Fed Am Eagle 158gr FP's - they chrono right at 1600 fps from my contender. Primers flatten out a bit but not excessively. Those are pretty sporty, touch one of those off and the action release pops you pretty good if holding with 2 hands around the grip.

As for the long throat Contender issue, I'm not really sure how much jump this barrel has. I do know that the other day I shot a 3 shot group that fit completely under a quarter at 50 yards with the IMR 4227 load and 158gr XTPs. Typical groups have not been much bigger hanging right around 1". If it will shoot like that I guess I really don't care what the jump is.

More fun than a barrel of monkeys!

Good looking firearm. You dont put the fingers of the support hand behind the trigger guard. If you ever shoot a hard kicker you will find that out quickly.
Good shooting too. Let us know what you find out about the charge you settle on.

Alliant list 18.6 with a 158 gr GDHP and standard primers.

Saw that - went with Hornady Data - they max out at 17.0gr but with a magnum primer and 158gr XTP bullets. Seems like it may be a bit conservative but still plenty stout enough for me. 1500+ fps from a 357 Mag is pretty amazing. I do believe any deer under 100 yards would not last long hit with a XTP FP going that fast.

As for keeping your support hand fingers in front of the trigger guard......well one good smack and I now keep my fingers in front of it. lol.

Been way too long since I messed with a Contender, making up for it now!

I used Alliant data and standard (actually match) fed primers for my load work up. Not mag primers. I think Hornady is lower because of the mag primers, but I'm not sure.

Works good in 30 carbine.

I tried that that powder out of a 4 inch 620. I found that h110 seemed to be a bit more accurate and I don't think that the 300 mp was any faster. That was just with federal primers, 158 xtp's, and starline cases.

158 XTP
16 GRAIns h110
starline case
federal mag primer

1280 fps 4 inch smith 620.

Wind finally died down last night so I shot 3 each at 16.5gr, 16.8gr and 17.0 gr. All shot right about 1500 fps and were 1" accurate at 50 yards. I need to try them again to confirm but going over 16.5 really did not increase the velocity as much as I thought. FWIW 16.5 is a full case, maybe a tad compressed.

I really don't think 300 MP is doing anything that H110 or W296 won't do and I'll probably go with one of those when this powder is used up. Which should be pretty quick because this T/C is ridiculously fun to shoot.

One more note about jump to lands in .357 barrel - it really does not seem to matter. After messing with the 300 MP loads I put 3) 38 special loads with Hornady 158gr LSWC HP's and 4.3gr of Unique through it and printed a pretty little cloverleaf at 50 yards. Accuracy of this handgun is amazing.

And, .22 K-Hornet.

DF

And .22 (Vanilla) Hornet.

Got back out shooting the T/C 357Mag with 300 M-P yesterday. Tried 3 @ 16.5, 3 @ 16.7 and 6 @ 17.0 with 158gr XTP HP's. Was getting about 1525 on the 16.5's and up to 1550 on the 17.0's. Must be about optimal as powder increase really is not making much difference. Accuracy at 50 yards was impressive. All 12 shots were within 1 1/2". A 6 shot group of the 17.0's, 5 of the 6 were in 1" and one just a tad high opened it up to 1.5". (I think I have a bit of parallax in my scope giving a bit of vertical stringing) I believe I have found a good stout hunting load. I would like to find some 158gr XTP FP's and see if they shoot the same as I believe that will be my bullet of choice this fall. Fun stuff.