MPX 8” barrel loading data

[brytec]

Wanted to know what’s your loading data for MPX 8”  barrel with 8.5”sleeve/shroud and PF ?  TIA

[Aircooled6racer]

Hello: 115 Acme, 3.8gr Tite Group 1.125"OAL 133-136PF, 121 Montana Gold 4.2gr Tite Group 1.160" OAL 142-147PF, 124 Acme 4.1gr Tite Group 1.150"OAL 145-150PF, 145 Acme 2.8gr Tite Group 1.140" OAL 132-134PF.  Freedom 124 reman  134-143PF,  Freedom 135 reman 132-145PF. Thanks, Eric

[SergioSF]

4 hours ago, Aircooled6racer said:

Hello: 115 Acme, 3.8gr Tite Group 1.125"OAL 133-136PF, 121 Montana Gold 4.2gr Tite Group 1.160" OAL 142-147PF, 124 Acme 4.1gr Tite Group 1.150"OAL 145-150PF, 145 Acme 2.8gr Tite Group 1.140" OAL 132-134PF.  Freedom 124 reman  134-143PF,  Freedom 135 reman 132-145PF. Thanks, Eric

 

Hi Eric - is your MPX a Gen2? Have you had the gas port opened up?

 

Thanks,

Sergio

[Aircooled6racer]

Sergio: It is a Gen 2 and has the standard port size. The weakest load it will cycle reliably is 122gr Acme 3.1gr Tite Group 1.140"OAL with a power factor of 116-124. It feels a little sluggish down there but I just wanted to see how low I could go. Thanks, Eric

[SergioSF]

18 minutes ago, Aircooled6racer said:

Sergio: It is a Gen 2 and has the standard port size. The weakest load it will cycle reliably is 122gr Acme 3.1gr Tite Group 1.140"OAL with a power factor of 116-124. It feels a little sluggish down there but I just wanted to see how low I could go. Thanks, Eric

 

My Gen2 OEM barrel would only reliably run factory 115gr. 

My new ILWT barrel runs 147gr but won't lock the bolt on empty. It'll run 124gr just fine. 

(these are all Freedom reman) 

[Aircooled6racer]

Sergio: I would check the gas rings to see if they are setup correctly. Reman Freedom gets launched into the next century with my MPX's. Also I run my bolt pretty wet. Thanks, Eric

[sdrr72]

Anyone have any additional suggestions for 8" MPX barrels (Gen 2 with opened up gas port if it matters)?  I have a recent SBR build that I just started using, and I am looking for suggestions with 124g/147g bullets (Xtreme plated or Bayou coated) that ring in around 130-135 PF.  Titegroup, N320, WST preferred.  It seems around 3.0 of TG with 147 should get me there.  What about the other combo's?  Any help appreciated!

Edited July 3, 2018 by sdrr72

[Underwood]

I tried some 115 blue bullets with 3.0 titegroup and 1.15 OAL.. and they all cycled perfect out of my MPX. But the MPX shoots so soft already i just use blazer 115's out of the box.

 

 i did not chrono , i was just testing to see if it would cycle these sub minor rounds. 

Edited July 3, 2018 by Underwood

[brytec]

I found with what I’ve already got:

prima v 2.8g

SNS 147g

1.15 OAL

PF 136

[Smithcity]

Wasted a bunch of time using VVN320, powder burns to quick for the MPX. My MPX's seem to like slower burning powder. Found the following is working really well for me:

4.5gr of VVN340

124gr Montana Gold JHP

1.13 OAL

132 PF

 

The N320 had a real tight powder range where the gun would cycle reliably. With the N340 I've found I can go as low as ~3.8gr with the 124gr bullet and still cycle the gun (albeit subsonic) and run up to 5gr without being over pressure. I couldn't load subsonic 147gr bullets with N320 and reliably cycle the MPX.

Edited July 12, 2018 by Smithcity

[sdrr72]

Well, I have some new data as of this past weekend at the LA Gator match for the 8" barrel:

 

124g XTreme plated

4.1g N320

1.120 OAL

Fed primers

134PF

[brytec]

That’s nice PF!  Must be pretty soft!  Any reliability issues with that load?

[sdrr72]

Shot close to 300 rounds over 10 stages with absolutely not a single issue the whole match (not a single issue with the gun or ammo, that is...).  I am still not sure if I like 124g or 147g better, but these ran fine.

 

As noted above, the gun is a Gen2 with an opened up gas port.  Ejects minor loads like they were major.

[George16]

2 hours ago, sdrr72 said:

Shot close to 300 rounds over 10 stages with absolutely not a single issue the whole match (not a single issue with the gun or ammo, that is...).  I am still not sure if I like 124g or 147g better, but these ran fine.

 

As noted above, the gun is a Gen2 with an opened up gas port.  Ejects minor loads like they were major.

 

What size did you opened up your gas port to?

[sdrr72]

21 hours ago, George16 said:

 

What size did you opened up your gas port to?

0.625.  ZRTactical did the work.  Shipped on a Friday; had it back in the mail the next Saturday.  Excellent service.

[jlo86cj]

ILWT 10.5” barrel

Berry’s 124 HBRN-TP
4.0 gr Alliant Sport Pistol
1.140” oal
132 pf

The barrel has a .062” port and I run a .054” gas plug and +20 recoil springs. Shoots like a dream.

[Acer2428]

Slightly off-topic, but did you notice an impulse or function difference going to the +20% springs? Seems odd to open the port up, then narrow it via the plug, then add more resistance via springs. 

[jlo86cj]

Slightly off-topic, but did you notice an impulse or function difference going to the +20% springs? Seems odd to open the port up, then narrow it via the plug, then add more resistance via springs. 

 

That's how the barrel came. I've ran 147's at 128 pf that ran better with an open plug and the +20 springs. I noticed better accuracy with the stiffer springs so I tune the gas to get the ejection pattern I like. Robert Otte sees the same accuracy improvement and attributes it to a slightly increased time in battery. Especially running aftermarket triggers that change the overall resistance that the bolt sees.

[sguenther]

I have the ILWT 6" barrel with opened up port, mid comp, and 9 inch shroud. I'm shooting CCI Blazer 115's at 129 PF. I have not developed a load for it yet. Gun is very clean, just put in new gas rings, Lucas extreme duty oil. Ejection is at 2 o'clock. I had 2 FTE's out of 300 rounds this weekend. It was working fine till I put in new gas rings. I thought it was under gassed and needed a higher PF.  Sounds like I'm over gassed. Do you recommend the adjustable gas block or just the .052 plug? And the 20% more power springs? I shoot Steel Challenge and regularly have .2 second split times, so 5 rounds per second. I had a 7.25 second total time for Smoke and Hope at my monthly match. JP modular drop-in trigger helps. I'm trying to figure out what bullet weight and PF to use. Any help will be much appreciated, thanks

[jlo86cj]

I have the ILWT 6" barrel with opened up port, mid comp, and 9 inch shroud. I'm shooting CCI Blazer 115's at 129 PF. I have not developed a load for it yet. Gun is very clean, just put in new gas rings, Lucas extreme duty oil. Ejection is at 2 o'clock. I had 2 FTE's out of 300 rounds this weekend. It was working fine till I put in new gas rings. I thought it was under gassed and needed a higher PF.  Sounds like I'm over gassed. Do you recommend the adjustable gas block or just the .052 plug? And the 20% more power springs? I shoot Steel Challenge and regularly have .2 second split times, so 5 rounds per second. I had a 7.25 second total time for Smoke and Hope at my monthly match. JP modular drop-in trigger helps. I'm trying to figure out what bullet weight and PF to use. Any help will be much appreciated, thanks

Every combo is different, but my experience would say you’re way over gassed. With Blaser Brass 115’s I would think a .052 and +20 springs would be the ticket. It’s starting to look like everyone wanting .062 ports was a bit overzealous. I just ordered a new 8” and Rob is leaving it at .052 for me. That way I can run an open plug.

Replacing the rings on the piston can be a bit picky. I have replaced them in the past and introduced short stroke failures. Replacing with a new piston instantly fixed the problem. I found you REALLY have to make sure every bit of carbon is out of the groove (especially the corners) before installing new rings. If it takes to much force to insert the piston you end up deforming the new gas rings.

[sguenther]

Thanks for the reply, I'm going to try. I clean the plug and piston in the ultrasonic all the time. When I was rotating the rings around I noticed one gap bigger than the others, the tip was broke off. I really spent a lot of time scraping carbon out of the groove before installing new rings. The new rings are just making it more over gassed now. So what ejection angle are you trying for, 3 o'clock?

[jlo86cj]

The new rings aren’t over gassing it. The full port, stock springs and open plug are doing it. The ejection angle doesn’t change as much as the distance. With that setup my 10.5 would probably eject 20 feet. Also, over gassing shouldn’t be the cause of your failure. It’s just hard on the hammer, bolt, etc.

The problem started after you changed the rings, so it’s a good chance that’s your problem. If the outer rings have a larger gap you probably have more carbon in the corner of the groove. This doesn’t let it compress and causes issues.

[sguenther]

The larger gap was due to the carbon build-up under the rings, you are right. When I clean plug/piston I scrub the outside and throw them in the ultrasonic. So am I supposed to take rings off and clean groove every time? If I'm careful with the rings can they be reused? I have extra of both types of rings. Do you have to use the Mcfarland style ring on the plug? It's harder to remove it for cleaning without bending it. Groove is clean as new now, new rings can compress. I'm going to take your advise about the gas and your load data. Thank You again very much!

Edited November 25, 2018 by sguenther

[jlo86cj]

No. Normal maintenance I just run the pistons and plugs in the ultrasonic and brush any residual carbon off the outside. As long as the original rings spin freely they seem to work good. Then I coat them in gun oil and keep them in a bag. Before installing the next time I clean them off with Brakeclean or carb cleaner. I have about five sets I cycle thru and just recently put new rings on them for the first time in about a year.

[sguenther]

I have an extra piston but 5 sets is serious. Hopefully there will be less carbon with the new restricted plug.

Edited November 26, 2018 by sguenther