Sig MPX?

[JCN]

I have been running the gas system really dry. Like bone dry.

Will try anti-seize on the gas piston of the Upper #2.



I have some left over from brakes.

It does get everywhere.

1600 degree temp resistance.

Will see if that improves function of loading cartridges.

If the bolt comes back with more force it’ll allow more time for subsequent rounds to feed…

Experimentation!

[DMCutter]

I haven't taken mine apart to clean it yet but now that I have my FAT wrench I will. Are you seeing wear on the gas system parts that warrant the anti sieze?

[JCN]

I haven't taken mine apart to clean it yet but now that I have my FAT wrench I will. Are you seeing wear on the gas system parts that warrant the anti sieze?

It’s not wear that’s motivating me to do it, it’s retaining smooth function.

It’s not going to be an issue for hot ammo, but for weak gamer ammo you need all the piston oomph that you get.

I could drill the gas port to drive more gas but I’m going for minimum recoil.

So I want to use minimum gas but not have that amount of gas rendered ineffective by gumming and friction.

That’s mainly the reason for it. Pistons are cheap and readily available so wear isn’t a concern.

[HeavyDuty]

Of *course* the MPX barrel retaining screws are a different Torx than the MCX. I need to order T25 bits for the Fatwrench.

[JCN]

Of *course* the MPX barrel retaining screws are a different Torx than the MCX. I need to order T25 bits for the Fatwrench.

FYI leading of the barrel affected my zero much more than the clamps so I pay a lot of attention to that now.
ILWT has a barrel tool with a T25 already mated to a torque wrench for handy use too.



Going to change practice and competition ammo.

I had 30k+ rounds of the Syntech 150 lying around from Carry Optics days and pre-pandemic.

I was shooting that up. But I bought 30k rounds of 130gr PCC recently for my wife.

Realistically she’s not going to notice or care if it’s 150 or 130.

So I think I’m going to start using the 130gr. It gives a sharper recoil impulse but the extra gas might help reliability in the MPX.

It makes about the same power factor ~150 out of my 8”.



I also circled around to try the Eley PCC again.

Milder than the Syntech 130.



About 130 power factor.

Even though the impulse seems sharper than the 150 Federal, the dot doesn’t move off target as much with recoil so that’s probably more important than how it feels.

I zeroed upper #1 at 25 yards with the Eley
Upper #2 at 25 yards with the Syntech 130.



Upper 1:
11350 of Syntech 150
50 of Eley PCC 124

Rounds since cleaned: gas 1400, bolt 1400
Parts broken: 0

Items replaced due to wear:
Tappet gas ring 5500 rounds, $2.50 replacement.
Extractor spring and donut at 5750 rounds ~$5.00
Tappet #2 gas ring 5000 rounds
Gas plug #1, 2 gas rings 5000 rounds ~$12
Firing pin and spring 10000 rounds ~$42
Hammer pins and springs 10000 rounds ~$12
Extractor spring and donut at 10000 rounds


Malfunctions after the initial tuning: 6
1. Second to last round jam in new 20 round plus extension, subsequently no issues.
2. Trigger didn’t reset once during a session, DUE TO MY ERROR INSTALLING hammer spring legs under the pin and the pin walked.
3. FTE replaced the extractor spring and donut at 5750
4. FTE at 2600 on gas system without cleaning and 2500 on extractor spring
5. FTL at 10000 rounds early in practice mag 2. Will try and tune mag.
6. Double feed with lube on cases at 11000 rounds, mag follower was binding.



———-
Upper 2: 3200 of Syntech 150
300 of Syntech 130


Rounds since cleaned: ~1550 bolt, 300 gas system.

Malfunctions: initial tuning phase
1. Single FTL with 20 round mag in 30 degree weather with full magazine attributable to a caulked charging handle not allowing bolt closure. Resolved with stock charging handle and tested in cold.
2. Had another FTL with a new 30 round mag and extension that I had not ever used before. I had a FTL about 5 rounds in.
3. FTL with Syntech and FTE with Lawman. Same magazine as #2. Changed recoil springs to known red -25% strength, changed extractor spring and post, changed magazine spring and follower.
4. FTL with Syntech, same magazine. 1250 rounds since cleaning. Clean and polish feed lips and magazine. Polished feed ramp of barrel.
5. FTL with Syntech, still that same magazine #3 early into the mag. Am going to swap the spring from my practice mag into the #3 body.
6. FTL with Syntech, still that same magazine #3 early into the mag.


I ran 300 rounds through magazine #3 with the gas piston anti-seize coated with no FTL. @DMCutter this is why I keep the magazine. If I get good function with that magazine by changing other parameters then I might actually be making my ecosystem more resistant to future failures. I’m going to hypothesize that by having less friction on the piston, it can slam the bolt back sharper and make better use of the gas available.

That then might impart more energy to the return trip of the bolt and possibly prevent some of the draggy FTLs I got with a loaded mag #3.

We shall see! Promising so far.

[JCN]

Good range session today.

300 rounds on Upper #2. Started having a couple FTEs which I attribute to a dirty extractor and spring with a few thousand rounds on it. It was ~1800 rounds since I had cleaned the bolt / extractor so that’s not unreasonable.







Upper 1:
11350 of Syntech 150
50 of Eley PCC 124

Rounds since cleaned: gas 1400, bolt 0
Parts broken: 0

Items replaced due to wear:
Tappet gas ring 5500 rounds, $2.50 replacement.
Extractor spring and donut at 5750 rounds ~$5.00
Tappet #2 gas ring 5000 rounds
Gas plug #1, 2 gas rings 5000 rounds ~$12
Firing pin and spring 10000 rounds ~$42
Hammer pins and springs 10000 rounds ~$12
Extractor spring and donut at 10000 rounds


Malfunctions after the initial tuning: 6
1. Second to last round jam in new 20 round plus extension, subsequently no issues.
2. Trigger didn’t reset once during a session, DUE TO MY ERROR INSTALLING hammer spring legs under the pin and the pin walked.
3. FTE replaced the extractor spring and donut at 5750
4. FTE at 2600 on gas system without cleaning and 2500 on extractor spring
5. FTL at 10000 rounds early in practice mag 2. Will try and tune mag.
6. Double feed with lube on cases at 11000 rounds, mag follower was binding.



———-
Upper 2: 3200 of Syntech 150
600 of Syntech 130


Rounds since cleaned: 0 bolt, 600 gas system.

Malfunctions: initial tuning phase
1. Single FTL with 20 round mag in 30 degree weather with full magazine attributable to a caulked charging handle not allowing bolt closure. Resolved with stock charging handle and tested in cold.
2. Had another FTL with a new 30 round mag and extension that I had not ever used before. I had a FTL about 5 rounds in.
3. FTL with Syntech and FTE with Lawman. Same magazine as #2. Changed recoil springs to known red -25% strength, changed extractor spring and post, changed magazine spring and follower.
4. FTL with Syntech, same magazine. 1250 rounds since cleaning. Clean and polish feed lips and magazine. Polished feed ramp of barrel.
5. FTL with Syntech, still that same magazine #3 early into the mag. Am going to swap the spring from my practice mag into the #3 body.
6. FTL with Syntech, still that same magazine #3 early into the mag.
7. FTE with 130 Syntech at 3800 rounds total and was 1800 since cleaning.

Items replaced:
2000 extractor spring
3800 extractor spring

[JCN]

One thing I’ve noticed about the FTL when it happens is that the round gets jammed semi vertically in the area that the bolt would occupy.

So the question is what’s contributing to that.

Is it magazine spring pressure, feed lips or bolt gas versus spring? Probably a combination of all of the above.

I will note that in initial tuning when there wasn’t enough gas for the recoil spring, that is one of the common failures.

So I think multi factorial but I think addressing the gas and recoil is reasonable.

[JCN]

Upper 1:
11350 of Syntech 150
350 of Eley PCC 124

Rounds since cleaned: gas 1400, bolt 300
Parts broken: 0

Items replaced due to wear:
Tappet gas ring 5500 rounds, $2.50 replacement.
Extractor spring and donut at 5750 rounds ~$5.00
Tappet #2 gas ring 5000 rounds
Gas plug #1, 2 gas rings 5000 rounds ~$12
Firing pin and spring 10000 rounds ~$42
Hammer pins and springs 10000 rounds ~$12
Extractor spring and donut at 10000 rounds


Malfunctions after the initial tuning: 6
1. Second to last round jam in new 20 round plus extension, subsequently no issues.
2. Trigger didn’t reset once during a session, DUE TO MY ERROR INSTALLING hammer spring legs under the pin and the pin walked.
3. FTE replaced the extractor spring and donut at 5750
4. FTE at 2600 on gas system without cleaning and 2500 on extractor spring
5. FTL at 10000 rounds early in practice mag 2. Will try and tune mag.
6. Double feed with lube on cases at 11000 rounds, mag follower was binding.



———-
Upper 2: 3200 of Syntech 150
600 of Syntech 130


Rounds since cleaned: 0 bolt, 600 gas system.

Malfunctions: initial tuning phase
1. Single FTL with 20 round mag in 30 degree weather with full magazine attributable to a caulked charging handle not allowing bolt closure. Resolved with stock charging handle and tested in cold.
2. Had another FTL with a new 30 round mag and extension that I had not ever used before. I had a FTL about 5 rounds in.
3. FTL with Syntech and FTE with Lawman. Same magazine as #2. Changed recoil springs to known red -25% strength, changed extractor spring and post, changed magazine spring and follower.
4. FTL with Syntech, same magazine. 1250 rounds since cleaning. Clean and polish feed lips and magazine. Polished feed ramp of barrel.
5. FTL with Syntech, still that same magazine #3 early into the mag. Am going to swap the spring from my practice mag into the #3 body.
6. FTL with Syntech, still that same magazine #3 early into the mag.
7. FTE with 130 Syntech at 3800 rounds total and was 1800 since cleaning.

Items replaced:
2000 extractor spring
3800 extractor spring


Doing more mini-stage drills

[JCN]

Upper 1:
11350 of Syntech 150
350 of Eley PCC 124

Rounds since cleaned: gas 1400, bolt 300
Parts broken: 0

Items replaced due to wear:
Tappet gas ring 5500 rounds, $2.50 replacement.
Extractor spring and donut at 5750 rounds ~$5.00
Tappet #2 gas ring 5000 rounds
Gas plug #1, 2 gas rings 5000 rounds ~$12
Firing pin and spring 10000 rounds ~$42
Hammer pins and springs 10000 rounds ~$12
Extractor spring and donut at 10000 rounds


Malfunctions after the initial tuning: 6
1. Second to last round jam in new 20 round plus extension, subsequently no issues.
2. Trigger didn’t reset once during a session, DUE TO MY ERROR INSTALLING hammer spring legs under the pin and the pin walked.
3. FTE replaced the extractor spring and donut at 5750
4. FTE at 2600 on gas system without cleaning and 2500 on extractor spring
5. FTL at 10000 rounds early in practice mag 2. Will try and tune mag.
6. Double feed with lube on cases at 11000 rounds, mag follower was binding.



———-
Upper 2: 3200 of Syntech 150
1000 of Syntech 130
50 of Eley


Rounds since cleaned: 450 bolt, 1050 gas system.

Malfunctions: initial tuning phase
1. Single FTL with 20 round mag in 30 degree weather with full magazine attributable to a caulked charging handle not allowing bolt closure. Resolved with stock charging handle and tested in cold.
2. Had another FTL with a new 30 round mag and extension that I had not ever used before. I had a FTL about 5 rounds in.
3. FTL with Syntech and FTE with Lawman. Same magazine as #2. Changed recoil springs to known red -25% strength, changed extractor spring and post, changed magazine spring and follower.
4. FTL with Syntech, same magazine. 1250 rounds since cleaning. Clean and polish feed lips and magazine. Polished feed ramp of barrel.
5. FTL with Syntech, still that same magazine #3 early into the mag. Am going to swap the spring from my practice mag into the #3 body.
6. FTL with Syntech, still that same magazine #3 early into the mag.
7. FTE with 130 Syntech at 3800 rounds total and was 1800 since cleaning.

Items replaced:
2000 extractor spring
3800 extractor spring

[Nephrology]

I have been running the gas system really dry. Like bone dry.

Will try anti-seize on the gas piston of the Upper #2.



I have some left over from brakes.

It does get everywhere.

1600 degree temp resistance.

Will see if that improves function of loading cartridges.

If the bolt comes back with more force it’ll allow more time for subsequent rounds to feed…

Experimentation!

I use that stuff on the threads of my suppressor QD muzzle devices. Works well vs carbon lock