There was some talk last spring of some lots of Alliant MP-300 being "hotter" than others causing some loads to be over-pressured. Several of us were using a popular load that used this powder. We got to checking to see if the powder we were using was part of the lots that had been identified as being hot or possibly hot. Mike and my powder were both included in the list of powder lots that were considered hot. I sent 3 of Mike's loaded shells and 3 of mine to Precision Reloading to be tested. The results we got back were astonishing. The load was originally built and tested to 12000 psi. The shells I sent in ranged from 12420 psi to 16370 psi. Undoubtably, Mike had one the "hottest" powder lots as his 3 shells AVERAGED 15,920 psi!!!! Any of you that knows Mike(Squeaky), knows that he is meticulous with every thing he does so this is not a case of not following the recipe. We both test our scales multiple times while loading shells so the powder charge was correct, but was way too hot. My 3 shells averaged 13,400 psi which is still way over the original design of the load and above SAMMI specs for a 20 gauge.. If you are loading shells using this powder, please check the lot number to see if it is included in the list below. If so, I would caution against using the shells until you send them to PR to be tested. These lots have been tested as hot or possibly hot. Alliant denied that the powder was hot but some of the lots CLEARLY are which can cause a very dangerous situation with pressures this high. We had actually stopped using this load several years back as it was just overkill as it used 2 1/8 oz of TSS but we both had a bunch of the loaded shells left over and I wanted to have them tested before we cut them open to rob the shot.

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For reference, the SAMMI specs for a 20 gauge with a full choke is 12,000 psi. This brings up another VERY important piece of information when loading TSS. Do NOT modify the recipe without having the load tested first. The guys that develop these loads are very smart and know what they are doing. Even small modifications can have enormous ramifications. Yes, TSS is expensive and having to send 6 shells plus pay $40 to have them tested is rough, but not as rough as having a gun blow up in your face.

Thanks Stony, I’ll check the lot on mine when I get in this evening.

I’ll add to the warning.

300 MP is a slow burning powder from what I am told. If your hull batch is slightly different from someone else’s, you could experience different results. For example, some hull-wad-powder combos don’t always shoot the same as your buddy’s batch he bought a year ago. If you are shooting a gas operated semi auto, you may experience your hull coming back in the chamber prior to full ignition. This will cause the sides of the hull to blow out instead of forcing the shot down the barrel. This is because the explosion from the powder forces the hull in the direction of least resistance.

I’ve experienced a batch of hulls in the past that would not allow the wad to seal and the powder charge leaked around them. This creates a dangerous situation because the wad would stick in the choke. If you fire a shot with a wad stuck in a choke, the back pressure created is going to blow the barrel up in your hand, or cause other components of the gun to fail.

These cases are few, but do occur. It’s not just with 300 MP. Be careful and heed warnings from those who have experience. If something isn’t right when you shoot, don’t just keep going and always make sure there are no obstructions left in your barre after a dud if you experience one.

Well shucks. I like the 2oz load but just checked my bottle. I’m in the unlucky winner club. Thank goodness I got 50 or so 1 5/8 loaded up too. Maybe I’ll just go back to them. Thanks for the warnings

Thanks for the heads up.

Mine’s the hot batch too, must be why it kicks like a mule! Is theire a 2 oz lil gun recipe?

Will Alliant not swap them out? I wouldn't think they would want hot powder in the hands of the public. Seems like a major liability

Even at 15k psi chances are you arent going to hurt anything. There are a couple load developers out there that have never tested their loads and many people are using them. Thing is I know of several people that have had these loads pressure tested and they are upwards of 17k psi.

I'm not saying not to be careful but just know some of the loads many of us have been shooting have never been pressure tested even though the developer claims they have and there hasnt.been any issues yet.

Only thing I could find about it was Alliant said we were using it in a wrong application as it’s primarily a handgun powder or error on the part of the reloader.

There’s plenty of cases showing up on FB pages of breech handles being blown out or as Jstocks mentioned, hulls collapsing in the chamber due to excessive pressures driving the hull back before full ignition occurs. I know most load developers use 14K as the top end of the pressure range but it doesn’t take much with these heavy payload shells to exceed that. The guy at Precision Reloading told me these were dangerous, especially in lower end quality guns. It would be totally irresponsible for a load developer to send out info that hasn’t been verified. Be very careful of who you buy shot from and whose recipes you are using!!!!

A lot of truth there

Reloading shotgun shells can go south quickly. The pressure signs are not necessarily like reloading metallic cartridges.

I've been loading steel shot shells for years now and one thing that has been engrained to me has been having to be careful. A few years ago Steel Powder supply dried up and then the new Lots hit the shelves and they were hot. I blended mine with older Lot numbers and reduced th charge. Some guys had some real problems and it was reported. I'd always been told to with each newLot number to start low and work up just to see.

The problem is that the pressure signs sometimes do not show up until it's too late.

Jansen I blew up a Remington 11-87 Supermag shooting a shell that was untested and I can promise you if it happens to you or someone you know and you see the results you'll never pull the trigger again unless you absolutely 100% know without a doubt that you're shells are safe. You know me, I have no reason to lie, I've never been as close to death as I was the morning I pulled the trigger on a handload a gunsmith loaded and claimed was safe. Thank God that Remington was tough. The receiver swelled up as big around as a baseball when it exploded and all I got was a headache but you can believe I'll never pull the trigger again unless I know what's in my gun has been tested and is under SAAMI specs.

It's been 5 or 6 years back but there was a thread on here about it. I was too embarrassed to post it at first but eventually posted it hoping others wouldn't make the same mistake.

I had a hand loaded dove load blow up a Remington 870 a couple of years ago. That shucks ain’t no fun just ask dw he was right behind me when it happened.

The loads I am.shooting have been tested. All the guys loads I use are under 12k psi. I was just bringing to light a lot of individuals on here have been and still are shooting loads that are over pressured. I'm not condoning doing it at all. Just changing a nitro card can increase pressure and I'd your already shooting a load that is over this could be the tipping point.

Dang. Great PSA post.

Im glad to see yall caught it and let these guys know. Id hate to see a post about an accident on here and one of the guys or their kids getting hurt.

I just check and the bottle I have for .410 is the last lot number listed

think I'm just gonna stick with factory loads with TSS. My longbeard XR's have worked pretty well too. Thanks for the PSA though!

Dr. B

I will check my MP-300 lot numbers, but I am guessing mine are in that group. I cut all my 2oz loads and am going back to lil gun. I stopped using it when i started getting wads that would come out missing petals, and mylar that was in pieces. Figured it couldnt be good for the barrel.

A lot of the issues you see on FB pages of the breach handles blown out and collapsed hulls are from a very well known "Factory Loaded TSS".

which one????