Alliant 300MP powder issues in .357

[Schwing]

A couple of years ago, I worked up some loads using 158 Grain JSP bullets from Montana Gold. The original thread is here:

http://www.thehighroad.org/showthread.php?t=736247

As stated in the thread, I had several squibs at the low end of the data (14.7 grains) but I attributed it to low temps. It was around 20 degrees. I hand weighed all of the charges involved so I am 100% certain they were the correct weight. For these rounds, I used Federal primers.

Fast forward to today; I received some 158 Grain JSP bullets from Zero and loaded them up. It was 95 degrees today and, remembering that I had squibs at the bottom of the data, I started at 15 grains which is .3 grains higher than the minimum. I was using CCI primers this time. As before, these were test loads so I hand weighed every charge... I still had squibs.

On the last one, it actually left a wad of unburned powder in the case. It broke into 2 pieces when it dropped out but was definitely unburned. I put a match to it to be certain. Here is a Pic:
http://www.thehighroad.org/attachment.php?attachmentid=212318&stc=1&d=1437528193

I am questioning Alliant's starting load data. I am also questioning whether standard primers really are sufficient for proper ignition as they claim. I am wondering if anyone else has experienced this with this powder. These were ultimately going to be my self defense rounds for camping, etc but I won't use 300MP for this now.

On the plus side, the rounds loaded with 15.5 grains did not have this issue and they were extremely accurate.

 

[243winxb]

357 mag 158 gr 300MP

Your below the starting load. 16.7gr

 

[Schwing]

Your below the starting load. 16.7gr

That does appear to be the case. My Hornady 9th lists 14.7 to 17. I also think Alliant has updated their load data since my last venture since my notes from 2013 list 14-17 grains.

It didn't even occur to me to look to see if it had changed. Thanks.

 

[243winxb]

Different bullets will have different load data

Different components = Different pressures. There are things other than powder to consider. 1. Trying a magnum primer. 2. Adjust neck tension- The expander should measure .356" but going to .355" might be needed if theres bullet movement. Test- fire the first 5 rounds in the cylinder, measure the last remaining rounds OAL. How does it compare to the orginal starting OAL ? 3. Also measure the neck area before and after seating a bullet. It should expand a minimum of .002" for good neck tension. Just some things to check.

 

[joneb]

I have noticed 300 mp likes to clump in the container?
Were you using standard or magnum primers?
I have used 300 mp in 22 hornet with SRP and 44 mag. with WLP with good results.

 

[Schwing]

Thanks for the tips 243winxb. Some of that I was aware of but things like checking oal on the 6th round is a great idea.

I also love that http://castpics.net website in your signature. There is an INCREDIBLE amount of useful info there!

Joneb, I was using standard primers as alliant recommends. I think 243winxb is correct. I checked the load data from 2013 (found on the castpics website) and 14 was never listed so my notes were just plain wrong. 14.7 was definitely listed in the Hornady 9th however.

 

[moxie]

When shooting in very cold temps like 20 F as you were, you might try magnum primers. See the attached flyer from CCI. It's a bit wormy, saying that magnum primers are for conditions below 20F, then saying use only when stated in published data.

http://www.cci-ammunition.com/products/primers/primers.aspx?id=29

On the other hand, consider the fact that in your recent test you validated the very purpose of a workup. You found loads that simply didn't work, and one that not only did, but was "extremely accurate." I'd lock in on that. You're on safe ground, being in the mid-range of published Hornady data.

On the other, other, hand, think about the powder you are using, 300 MP. I strictly use Unique or 2400 in .357 and have never had a "squib." Never heard of one like you describe either. Shouldn't have happened in the warm weather test, even with the possibly slight undercharge you were using. They should have fully functioned and just gone at a lower velocity. As far as cold weather goes, I've shot them around the 20F point and colder and had no problems, but that's from holstered guns. I've never tested with cold-soaked rounds.

 

[gamestalker]

I thought a couple of the big marketing claims by Alliant with this powder is, it doesn't need magnum primers like H110/296 does, and it's not temperature sensitive like H110/296 is?

Thanks for posting your results though. I've been waiting to hear more about actual reloading experiences with it. But it appears your problem is more likely related to sub table start charges.

I almost grabbed some the other day at SWH, but I'm still waiting to hear more feed back from the reloading world. I'm interested to hear what it does for you at the correct published start charge.

Thanks again for sharing the results.

GS

 

[Schwing]

I thought a couple of the big marketing claims by Alliant with this powder is, it doesn't need magnum primers like H110/296 does, and it's not temperature sensitive like H110/296 is?

Thanks for posting your results though. I've been waiting to hear more about actual reloading experiences with it. But it appears your problem is more likely related to sub table start charges.

I almost grabbed some the other day at SWH, but I'm still waiting to hear more feed back from the reloading world. I'm interested to hear what it does for you at the correct published start charge.

Thanks again for sharing the results.

GS

I would not hesitate to buy it as long as you are not loading light. I have also had great luck with it in .44 magnum. In fact, For my 240 grain JSPs I get the best accuracy of any powder I have tried to date. I need to chronograph those rounds but, with 21-22 grains of 300 MP, they are pretty stout and the max is somewhere in the 25s. It also meters better than most powders; I would argue even better than some like Bullseye.

 

[TimSr]

There seem to be an awful lot of problems with Hornady load data being significantly different than other sources. When it comes to powder charges, I would go with the powder mfg data over the bullet mfg data every time. Just anecdotal based on forum observations, but I wouldn't use a Hornady data manual unless it was backed up by somebody else's data.

 

[2ndtimer]

My experience over many years loading slow burning spherical powders is that they tend to function best in a very narrow range, at or near maximum loads. Many years ago, I seem to recall Winchester's data sheet for their 296 powder for 158 gr jacketed bullets stated to load 16.6 gr with a Magnum pistol primer and DO NOT REDUCE. So for many years, that was my .357 Mag load. Later loading manuals have off the data some, but I still load 16 gr with the 158 gr JHP and Magnum primers. I load the 300MP near the top as well, also using Magnum primers, as that seemed to be where it performs best. If you want to load less than max, I suggest trying Alliant 2400 or Accurate No. 9, as both seem more flexible than H110, W296, or 300MP.

 

[Schwing]

I know this is an older thread but I wanted to post my follow up with this powder. My first impressions with squibs at low charges made me a little leery but I have made a complete turn around on my opinions. The data I used from Hornady, as stated earlier in the thread, was far too low anyway and was well below the data published by Alliant.

I have come to the conclusion that it is my new favorite powder for magnum loads in both .357 and .44. It burns much cleaner than 2400 which was my previous go to for magnums. With 2400 I usually saw an extreme spread of about 40-50fps. With 300mp it is in the low 30s.

One thing that is very noticeable is that my perceived recoil is far less on 300mp for loads achieving similar velocities. With my 158 grain JSPs, both 14.9 grains of 2400 and 17 grains of 300mp reach around 1300fps out of my 5" GP100 and both reach about 1700FPS from my 16" lever action but the recoil is significantly lower with the 300mp. Muzzle flash and blast were also noticeably less with 300mp.

My conclusion is that, as long as you are not trying to load light, this is certainly a great option. Below is my last test of 17 grains with 158 grain JSPs from Zero. Those are 1/2 inch grid lines and these were fired at 15 yards. The flyer on the right was all me. As usual, I psyched myself out on the last shot and flinched a bit. My results in .44 were even slightly better with 21.5 grains of 300mp behind a Montana Gold 240 grain jsp.

 

[joneb]

That is sweet, I like this powder to. I am still struggling with Be-86.

 

[Toprudder]

I've tried 300MP with Hornady 158 XTP bullets, also from a 5" GP100.

My starting point was 15.0gn, and I went up to 17.0gn. The interesting thing with my loads, though, is that I reached a velocity plateau of around 1200fps. The velocity did not change, with a charge level between 16.1 to 17.0gn. I did not see any pressure signs in that range, but I was just leery of increasing any more.

I have been meaning to work up some more loads to try out in my carbine. I've been wondering if the powder is just too slow to get a complete burn in the shorter barrel, and with a longer barrel I might see a velocity change from 16.1 to 17.0gn charge range.

 

[TimSr]

Glad you posted a conclusion on this. I've always had the impression that this powder was Alliant's answer to 296/110 and I'd be real interested in hearing about comparison between them. I'll probably be doing one eventually but still have a near full 296 bottle right now.