I've always been a fan of the MP5 and they are a great gun to run and I always believed they were the cat's meow. That was until I had the chance to run a full auto MPX with our local LE rep. So a few years ago I purchased a first gen 8" pistol version with the intention to SBR it at some point in the future. I've always been a fan of sub-guns and PPC's but have always wanted or hopped for something with a little more ass behind it without having to go to a rifle caliber and Sig promised other calibers for the MPX to come.
A few months ago I purchased an STI Stuccato P and with speaking with STI, was turned onto the 9mm Major. I had never heard of it before and I liked the idea of a 9mm pushing .45 energy, so naturally I began to do some research. I wasn't able to find much information other than it being a load developed for competition shooting for major power factor. It's obviously not SAAMI spec and pressures are off the chart making +P+ look tame. So what exactly was the draw with this cartridge?
I started looking for anything I could find or manufacturers that were producing this ammo but all leads came up dry. I found a few threads here and there but still very little information but the sound of a 124g projectile hitting 1300+ feet per second in a 4" barrel got me salivating especially when the thought of sending that down the pipe of my MPX popped into my head. After several weeks of computer searches, I finally found a place that was currently producing a factory 9 Major load so I called them up. A place called Black Dot Ammunition out of Alabama I think. I'd never heard of them or tried any of their ammo, but I needed more info on this cartridge.
I spoke to what I think was one of the owners and he was very pleasant and eager to hear what I wanted to do. I told him my plans of trying to shoot 9 Major out of the MPX and at first he just chuckled. I asked if that was a bad idea and if the gun could even handle it and he said "You might want to call Sig and ask because I've never tested it, but that would be a freaking hot rod load." I asked what the specs were on his ammo and he said his development was tested on 4" barrels that were purpose made for the cartridge and loaded to 1.160" and firing out at 1385fps and must be fired from a supported chamber to handle the pressure. I must note that he strongly advised against attempting to shoot this out of a blow back type AR but he did say that with the MPX having a locking BCG and gaspiston, as long as the barrel was up to par, it might handle it.
So my next call was to our LE rep. Remembering that he stated the MCX was tested to around 70,000psi and saying the MPX was a similar operating system and materials, I was hopeful it would be up to the task. After speaking with him, he stated they never tested the MPX for Major loads but they had tested with great results with +P+ and there were no issues or pressure signs. I asked if he thought there would be any issues or catastrophic failures and to my surprise, he said the gun was built to run and run hard. He would not specifically say if it would handle the pressure or not, but did say it might reduce the life of some of the parts. So, me being full of amazing ideas I took that as a green light to try it out. After all, Sig originally said they designed this thing to run the 357 Sig which fires out at roughly 1350fps and 40,000psi. So it should be good right? So I ordered up a case of Black Dot 9mm Major with a 124g hallow point and impatiently waited for it to arrive.
Now the story begins.
Monday my ammo arrived and I had a little time to play. I purchased a new Magneeto Speed V3 since my last chrono quit working and I had some rifle data to work on. I figured this was perfect, got my new chrono and Major ammo the same day. I pulled out the MPX from its sleeping spot, next to my bed, and emptied a magazine. I opened the box of 9 Major and looked it over and was impressed. It was very clean and loose packed in boxes of 200 with a quality control card in the box. First time I've ever seen that. I quickly tossed that to the side and loaded 10 rounds in the magazine and topped them with 3 rounds of Federal 115 FMJ's just to get a base line.
I headed out to give this thing a shot. I strapped the V3 to my SRD45 suppressor mounted on the MPX and adjusted it for proper fit and function. I plugged in the bayonet and readout and adjusted the sensitivity to 3 and was ready to fire. Knowing I had 3 rounds of factory Federal 115 FMJ I wasn't concerned about safety from over pressure so I pressed the trigger. No issues, cycled the action and fired again and again. When that third round fired and cycled and chambered the 9 Major, I swear I heard a voice from deep within the MPX say "Thank you."
I was all excited and ready to press the trigger when I remembered, Very Hot Load and massive pressure...so safety first. I lifted my head, moved the stock up slightly on my shoulder so...you know, if the bolt decided to exit the rear of the receiver, it would miss my shoulder, and moved my head off to the side just a bit and I pressed the trigger. Now this thing fired with authority and that little voice inside the MPX bellowed "FEED ME MORE." I noted there was no bolt slap or back blast or over gassing in the slightest, just an authoritative cycle with a purpose. I looked at the chrono and it registered 1510fps. I fired the second round and no issues, just the same purposeful cycle and no bolt slap or gassing with a reading of 1508fps. I fired the remaining 8 rounds with a low reading of 1498 on one round with the rest ranging from 1505 to a high of 1512 fps and no signs of over pressure on the bolt, the carrier, or the brass. There was no signs of pressure on the primer and no flowback. I was amazed.
So a 124g hollow point 9mm firing at an average of 1505fps generating 623 foot pounds of energy out of an 8" suppressed sub-gun with no signs of over pressure was the end result of the day. All in all, I am very impressed with this MPX and I intend to run it to the ragged edge of what it will do and just a little bit farther.
Since Monday, I did find another thing that will be part of my next test. I was informed of some extremely high pressure casings made by Shell Shock Technologies for the 9mm. They are a two piece design apparently rated to over 60,000psi and claimed to be able to do so in an unsupported chamber. If that is true along with the supposed possibility the MPX bcg can handle pressure and it being more than 10,000psi over the 9 Major load, I'm interested to see what velocity can be achieved. My thought is maybe another 100-150fps?
Thanks for taking the time to read and I hope you enjoyed. Have a safe day.
A few months ago I purchased an STI Stuccato P and with speaking with STI, was turned onto the 9mm Major. I had never heard of it before and I liked the idea of a 9mm pushing .45 energy, so naturally I began to do some research. I wasn't able to find much information other than it being a load developed for competition shooting for major power factor. It's obviously not SAAMI spec and pressures are off the chart making +P+ look tame. So what exactly was the draw with this cartridge?
I started looking for anything I could find or manufacturers that were producing this ammo but all leads came up dry. I found a few threads here and there but still very little information but the sound of a 124g projectile hitting 1300+ feet per second in a 4" barrel got me salivating especially when the thought of sending that down the pipe of my MPX popped into my head. After several weeks of computer searches, I finally found a place that was currently producing a factory 9 Major load so I called them up. A place called Black Dot Ammunition out of Alabama I think. I'd never heard of them or tried any of their ammo, but I needed more info on this cartridge.
I spoke to what I think was one of the owners and he was very pleasant and eager to hear what I wanted to do. I told him my plans of trying to shoot 9 Major out of the MPX and at first he just chuckled. I asked if that was a bad idea and if the gun could even handle it and he said "You might want to call Sig and ask because I've never tested it, but that would be a freaking hot rod load." I asked what the specs were on his ammo and he said his development was tested on 4" barrels that were purpose made for the cartridge and loaded to 1.160" and firing out at 1385fps and must be fired from a supported chamber to handle the pressure. I must note that he strongly advised against attempting to shoot this out of a blow back type AR but he did say that with the MPX having a locking BCG and gaspiston, as long as the barrel was up to par, it might handle it.
So my next call was to our LE rep. Remembering that he stated the MCX was tested to around 70,000psi and saying the MPX was a similar operating system and materials, I was hopeful it would be up to the task. After speaking with him, he stated they never tested the MPX for Major loads but they had tested with great results with +P+ and there were no issues or pressure signs. I asked if he thought there would be any issues or catastrophic failures and to my surprise, he said the gun was built to run and run hard. He would not specifically say if it would handle the pressure or not, but did say it might reduce the life of some of the parts. So, me being full of amazing ideas I took that as a green light to try it out. After all, Sig originally said they designed this thing to run the 357 Sig which fires out at roughly 1350fps and 40,000psi. So it should be good right? So I ordered up a case of Black Dot 9mm Major with a 124g hallow point and impatiently waited for it to arrive.
Now the story begins.
Monday my ammo arrived and I had a little time to play. I purchased a new Magneeto Speed V3 since my last chrono quit working and I had some rifle data to work on. I figured this was perfect, got my new chrono and Major ammo the same day. I pulled out the MPX from its sleeping spot, next to my bed, and emptied a magazine. I opened the box of 9 Major and looked it over and was impressed. It was very clean and loose packed in boxes of 200 with a quality control card in the box. First time I've ever seen that. I quickly tossed that to the side and loaded 10 rounds in the magazine and topped them with 3 rounds of Federal 115 FMJ's just to get a base line.
I headed out to give this thing a shot. I strapped the V3 to my SRD45 suppressor mounted on the MPX and adjusted it for proper fit and function. I plugged in the bayonet and readout and adjusted the sensitivity to 3 and was ready to fire. Knowing I had 3 rounds of factory Federal 115 FMJ I wasn't concerned about safety from over pressure so I pressed the trigger. No issues, cycled the action and fired again and again. When that third round fired and cycled and chambered the 9 Major, I swear I heard a voice from deep within the MPX say "Thank you."
I was all excited and ready to press the trigger when I remembered, Very Hot Load and massive pressure...so safety first. I lifted my head, moved the stock up slightly on my shoulder so...you know, if the bolt decided to exit the rear of the receiver, it would miss my shoulder, and moved my head off to the side just a bit and I pressed the trigger. Now this thing fired with authority and that little voice inside the MPX bellowed "FEED ME MORE." I noted there was no bolt slap or back blast or over gassing in the slightest, just an authoritative cycle with a purpose. I looked at the chrono and it registered 1510fps. I fired the second round and no issues, just the same purposeful cycle and no bolt slap or gassing with a reading of 1508fps. I fired the remaining 8 rounds with a low reading of 1498 on one round with the rest ranging from 1505 to a high of 1512 fps and no signs of over pressure on the bolt, the carrier, or the brass. There was no signs of pressure on the primer and no flowback. I was amazed.
So a 124g hollow point 9mm firing at an average of 1505fps generating 623 foot pounds of energy out of an 8" suppressed sub-gun with no signs of over pressure was the end result of the day. All in all, I am very impressed with this MPX and I intend to run it to the ragged edge of what it will do and just a little bit farther.
Since Monday, I did find another thing that will be part of my next test. I was informed of some extremely high pressure casings made by Shell Shock Technologies for the 9mm. They are a two piece design apparently rated to over 60,000psi and claimed to be able to do so in an unsupported chamber. If that is true along with the supposed possibility the MPX bcg can handle pressure and it being more than 10,000psi over the 9 Major load, I'm interested to see what velocity can be achieved. My thought is maybe another 100-150fps?
Thanks for taking the time to read and I hope you enjoyed. Have a safe day.
