.357 Magnum Load Help

A little about me:


I've been reloading for a little over four years for the .308, 223/556, 6.8 SPC II, .277 Wolverine, 20 & 12 gauge along with pistol calibers in 22 TCM, 9mm, 40, and 10mm.


My wife and son bought me a Ruger GP100, Model 1707-6" for my birthday.
I'll start casting my first boolits this weekend.


My goal at this point before moving on to CB loads:


I'm trying to match the 1467 fps velocities (out my barrel) of 158 grain Buffalo Bore ammo using the Hornady 158 grain XTP.


What I've read:


.357 magnum loads need a heavy roll crimp which I do as a separate operation.


All cases should be trimmed to the same length for crimp consistency.


Note:


All brass is new starline brass that was trimmed to the same length.


I started with a Lee carbide factory roll crimp die and switched to a Redding profile die. I cannot tell the difference in crimp between either dies. I even compared my crimps to factory loads.


I had to back off my crimp (maybe .002-.005, if that) because I was flattening out the roll crimp against the bullet.


I use check weights (1-400 grains) to calibrate my scales and I use a balance beam for load development.


Issue or I believe to be an issue:


Not reaching the velocities that (I think) I should (I know that the load data is probably for a longer barrel).


Finding unburnt powder on the bench after firing with Blue Dot and 300-MP


Yes, I know not to use Blue Dot with 125 grain bullets, etc


Data from this mornings range trip:

No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: 300-MP 16.5 grains
O.A.L: 1.575"
Velocities:


High: 1267
Lo: 1166
10 shot Average 1195 fps
ES: 101
SD: 33
.................................................. ..........
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: 300-MP 17 grains
O.A.L: 1.575"
Velocities:


High: 1272
Lo: 1194
10 shot Average 1235 fps
ES: 78
SD: 27


.................................................. .......................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: 300-MP 17.5 grains
O.A.L: 1.575"
Velocities:


High: 1308
Lo: 1218
10 shot Average 1261 fps
ES: 90
SD: 33


.................................................. .......................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: 300-MP 18 grains
O.A.L: 1.575"
Velocities:


High: 1380
Lo: 1214
10 shot Average 1315 fps
ES: 166
SD: 50


.................................................. ................



Any thoughts or comments ?

#1 You probably can't buy the powder BB is using. #2 BB may be going with the older hotter sammi pressure data for the .357 (approx 40K psi as opposed to today's standards of 35K). Alliant's data may be pretty optimistic as far as velocity numbers but they are also looking at that 32-35K psi sammi ceiling for load data. Not real impressed with the ES and SD numbers for 300mp. Have you tried any H110/296?? Not sure why you need or want 1467 fps but there are a lot of very good accurate loads for the .357 in the 1300 fps range.

You may find that the BB load may not be reaching 1467 fps in your gun. Would be best to buy a box of the BB loads and check them for velocity in your gun and try to load for the velocity given by the BB load if it does not exceed safety limits. Fecmech may be right that BB is using a powder that is not available to us reloaders. He is also right on trying H110/296 for higher velocity.

My main concern is the unburnt powder and fixes, if any.

I'm aware that I might not reach the velocities without trying other powders or exceeding recommended safe load data.

As stated in my original post, those velocities (BB ammo) are out of my barrel.

Thanks for the feedback all.

You might be impressed with how much a little more barrel will bump your velocity but powder selection is key, some powders give very very little gain (faster powers). I did some velocity tests with .38's and .357's across several barrel lengths, wish I had a working 10" contender barrel at the time for the frame I had when I did the tests that would have added more data anyways take a look and see.

http://wonderwolfs.blogspot.com/2014...m-carbine.html

http://wonderwolfs.blogspot.com/2015...7-carbine.html


I've not tried any super bear busting loads in .357 yet....also note the GP100 in my tests are a 5" barrel not the 6"

I've tried some non book loads with success and they have been very safe. It seems to me these days the data has been really toned down in some books for one reason or another. I'm not suggesting you throw the book out but just remember the company that came out with the data wants a certain margin of safety built into the data. If 8gr of a powder will for sure blow the lowest quality gun up and 7gr is what they know is max than you'll see the max as 5.5gr in some loads.

:confused:
I would be in search of accuracy first.
I have a pound of 300mp waiting on me to try it in something.
A simple search should give you an idea if the 300mp will get you there.
IMHO 158 is a mid range weight for the 357. I have come to prefer a 180 across the board, jacketed or cast.
From my findings on 357 magnum in strong guns is the harder you push them the better they seem to shoot. The GP will stand a lot more than any SW, but one has to know his limits.
My 357 loads for my FA and TC would be a bit stiff even for a Ruger, but it is hard to argue with the accuracy.

Quickload shows several powders that should reach 1450 from a 6" barrel when loading the 357 Magnum with the 125gr XTP but only 2 with the 158gr without going over SAAMI standard pressure. I think this pretty well backs up the earlier statement that you probably cannot get powder that BB is using in that load. The only two powders that could break 1450 with the 158gr were Norma R123 and Lil'gun and to get 1450 with either of those is right at the limits. You certainly aren't going to exceed 1450 by much if any without being way over pressure so approach this goal very carefully.

The 357 has been downloaded from its original 158 grain cast bullet load a few times now.

I've found that for the highest velocity within current pressure limits, Lil'Gun does the best job with the heavier bullets. I use it up through 180 grain projectiles (lead and jacketed) with good success and velocities above what I can safely get with 296 or 2400. It really rocks in rifle length barrels, but still gives good performance in 6" revolvers. I've never noted any unburned powder on the bench after bench resting revolvers for chronograph testing with Lil'Gun.

Check the Hodgdon web reloading site for data. They used a 10" barrel to get 1,577 fps with Lil'Gun and a 158 grain jacketed bullet. Not sure how that will hold up in your barrel, but it's a start.

I was going to use LIL'GUN (lower pressures) originally but reports were that it will erode the forcing cone.

I could not find H110 or W296 locally so I ended up buying 300-MP.

I agree with the above, Lil'Gun is THE powder for maximum velocities in .357 magnum.

Quote:

---

Originally Posted by wiljen

Quickload shows several powders that should reach 1450 from a 6" barrel when loading the 357 Magnum with the 125gr XTP but only 2 with the 158gr without going over SAAMI standard pressure. I think this pretty well backs up the earlier statement that you probably cannot get powder that BB is using in that load. The only two powders that could break 1450 with the 158gr were Norma R123 and Lil'gun and to get 1450 with either of those is right at the limits. You certainly aren't going to exceed 1450 by much if any without being way over pressure so approach this goal very carefully.

---

I appreciate you taking the time to run the data and replying.

Just a thought , I know it doesn't seem logical, but have you tried standard primers. I believe that MP300 was made for use with std.primers. The mag primers could be starting the bullet out of the crimp before the powder ignites causing the unburnt powder left behind.Just a thought.

^^^ I have never use Power Pro 300-MP. And I am surprised to learn that it calls for standard primers. Not sure how much is to be gained by trying to duplicate Buffalo Bore or Underwood ballistics. I have no use for Lil'Gun which, is what makes sense here. 2400 is a "hot" as I want to go.

Quote:

---

Originally Posted by marshall623

Just a thought , I know it doesn't seem logical, but have you tried standard primers. I believe that MP300 was made for use with std.primers. The mag primers could be starting the bullet out of the crimp before the powder ignites causing the unburnt powder left behind.Just a thought.

---

yes, no difference except I'm getting better accuracy with the magnum primers at higher velocities.

I just use 2400 in my trapper 190 gr GC boolit = 1250 fps with 11.5 gr .158gr GC boolit =1550 fps. Both loads very accurate don't worry about speed worry about accuracy.

Quote:

---

Originally Posted by TXCOONDOG

yes, no difference except I'm getting better accuracy with the magnum primers at higher velocities.

---

I'm curious.
What velocities did you get with Blue Dot?

It is filthy to shoot but I'm getting 1258fps from a 3" S&W with the 158gr #35750 XTP, 11.5gr of Blue Dot and CCI550 primers.
In my old data notebook I've got 1350fps logged for this same load but can't remember which firearm was used.

I failed to mention that as I work up my loads, I also note accuracy. I analyze my data (using various powder/primer combinations) and make nessary adjustments to fit my shooting needs.

I take the time to shoot my loads in all four seasons and note my findings such as velocity changes, etc. I also perform penetration tests at various distance too as I like to know my and each loads limitations.

To ensure the best accuracy possible, I have a pistol scope mounted and use a solid rest for load development. I plan to shoot each load freehand too.

My issue at the moment is the unburnt powders and reducing the extreme spread. I know it would be easier to move on to something else, like trying different powders, etc......I want to learn and not take the path of the least resistance

Quote:

---

Originally Posted by tsubaki

I'm curious.
What velocities did you get with Blue Dot?.

---

No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 9.0 grains
O.A.L: 1.590"
Velocities: Average 977 fps
Five shot Group size at 25yards: 1.25"
.................................................. .......................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 9.5 grains
O.A.L: 1.590"
Velocities: Average 1057 fps
Five shot group size at 25yards: 1.25"
.................................................. ........
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 10 grains
O.A.L: 1.590"
Velocities: N/A
Five shot group size at 25yards: 1.35"
.................................................. ........................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 10.5 grains
O.A.L: 1.590"
Velocities: Average 1185 fps
Five shot group size at 25yards: 4 @ 3/4" & 1 flier 1.50"


Note: When I started seeing unburnt powder and extreme velocity spread of 110 FPS

I've found with gas checked cast bullets, I am unable to get 300-mp to generate enough pressure quick enough to seal the brass to the cylinder wall and prevent blow by. I've run over 20gr with a 166gr pill. I've run over 14gr with a 200gr pill. I'm not getting pressure signs, the case head expansion is around .003". I haven't had time to run the loads up any higher to see if I can get the blow by to stop but I intend to do so this winter.

Quote:

---

Originally Posted by TXCOONDOG

No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 9.0 grains
O.A.L: 1.590"
Velocities: Average 977 fps
Five shot Group size at 25yards: 1.25"
.................................................. .......................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 9.5 grains
O.A.L: 1.590"
Velocities: Average 1057 fps
Five shot group size at 25yards: 1.25"
.................................................. ........
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 10 grains
O.A.L: 1.590"
Velocities: N/A
Five shot group size at 25yards: 1.35"
.................................................. ........................
No signs of pressure


Bullet: Hornady 158 gr XTP HP
Case: Starline 1.285"
Primer: WSPM
Powder: Blue Dot 10.5 grains
O.A.L: 1.590"
Velocities: Average 1185 fps
Five shot group size at 25yards: 4 @ 3/4" & 1 flier 1.50"


Note: When I started seeing unburnt powder and extreme velocity spread of 110 FPS

---

Thank you!
This will be helpful when I get back to the 357 jacketed and maybe with some of the cast.

Quote:

---

Originally Posted by TXCOONDOG

I was going to use LIL'GUN (lower pressures) originally but reports were that it will erode the forcing cone.

I could not find H110 or W296 locally so I ended up buying 300-MP.

---

Any slow burning powder that offers the highest velocities is going to cause forcing cone erosion.