2011BLDR
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Posts posted by 2011BLDR
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expansion chamber
Depth should be
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1 hour ago, Bdh821 said:
Thanks for the input. I appreciate any info to be gained about the platform. Did you shoot A2? I would have loved to run into you if so..
Yea I did... I shoot Rio about ounce a month when a Tucson Match is Canx for whatever reason ( MD's are DOD and go TAD or the other range doesn't have the required #'s to hold the Match)
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11 minutes ago, Bdh821 said:
I've had issues. My MPX malf'ed yesterday which cost me a local club match win. it was a pcc match too. I'd say 150gr federal syntec ammo is the incorrect ammo for a MPX. They're gas guns and 150gr ammo doesnt make much gas...
regardless, ive had good luck with my MPX', but I've had issues too, like all PCCs. I have 3 MPXs tho. 1 practice gun, 1 match gun, 1 match backup gun.
That 150gr syntec is like 3gr of super fast powder designed for Production/Carry Optics 870FPS 4.5-5 " barrel (130.5 PF) ... when I tested it in a 16" MPX it only did 960FPS (90 FPS gain), most factory ammo gains 185-225 +FPS in the 16" barrel.
I have been running MPX's since the start of PCC in 2016. give it the correct ammo ( correct burn rate to generate gas, no coated bullets), maintain the gas plug expansion chamber and the extractor( insert spring & O ring) and they run soft fast and flat like an Open gun with a stock..
I have 4 paired up 2 for major / travel matches that rotate every other match as primary and backup ( originally Gen 2's re-barreled to PCC's last year). 2 for locals run one primary other is a back up ( one originally Gen 2 re-barreled to PCC last year) other one was bought as a PCC.
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On 1/1/2022 at 9:16 PM, Bdh821 said:
Care to elaborate more as I don’t understand restricted gas plugs for the MPX. What exactly does it do? I have 50-60k thru one of my MPXs and has the original gas plug..
Gas port in the barrel is just forward of the chamber about ¼” in to the rifling, location was chosen for the 4” barrel to work, all of the lounger barrel lengths are adding dwell time and increasing port pressure that leads to port erosion over time. The gas plug has an expansion chamber that fills with gas to delay extraction before the piston moves. When that expansion chamber fills up with Carbon/Lead/Poly Coating you are reducing the volume and delay to extraction. I.E you are attempting to extract while the case is still expanded against the chamber walls. As the barrel port erodes you are in effect pushing more gas in to the expansion chamber faster and reducing the delay to extraction causing the same issues.
The slot in the gas plug is .117” that is intended to work with a new barrel gas port on a 4” barrel dwell time. ILWT has gas plugs with .0520” and .0469” holes in place of the .117” slot.
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MPX's are not hard to maintain, just different than Blowback:
- ultrasonic tank every 500-600 rounds
- under stand the system gas requirements (med burn rate powders (CFE pistol,N330,N340, 3N37) @145-160PF
- under stand the EXTRACTOR system requirements ( tension on the retaining pin is my indicator) and rebuild it ( Sig factory parts only for the insert, spring and O ring) before it fails
- understand that gas port erosion is a issue, starts to effect gas system reliability at around 10,000-15,000 rounds, you can drop down to a .0520 restricted gas plug and keep going, and then down to a .0469 and keep going some more.
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1. Check all grip screws are tight
2. Ensure the front trigger guard pin is present
3. Pull the beavertail out and check function without it, look for side to side movement in the leaf spring and smooth disconnect movement
4.With the over-travel all the way out you could bind the disconnect / sear
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For the current competition 16” MPX's with the side venting brake yes it works just as well as the MBX did on the old gen 13.7” barrels for me. Lighter bullets medium burn rate powder ( CFE, N330, N340..) my current 3 loads I use depending on bullet availability:
· 100gr FMJ 6.4 CFE Pistol 1497 Fps
· 95gr Montana Gould JHP 6.4 CFE Pistol 1515 Fps
· 115gr FMJ/ JHP 5.4 CFE Pistol 1350 Fps
Give me minimal dot movement, as a factory reference in my 16" guns:
· Speer Lawman 115gr TMJ load is 1425fps
· Federal XM9001 115GR JHP is 1445fps
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16 hours ago, Dirty_J said:
Agree with lots of what’s posted here.
I find the MPX prefers a heavier projectile (124gr or over) and slower powders. I had much better luck with CFE pistol and Shooters World Auto Pistol, than sport pistol (which is my goto powder for carry optics).
If it is indeed prematurely unlocking, and sport pistol is all you’ve got... might consider the +20% recoil springs that are available. Could add a few ms to that dwell time.
Don't agree with the heaver bullets use 115gr @1360FPS /156PF as the easiest bullets to source right now. Had a wonderful 100gr @1520FPS / 152PF load but cant source the bullets again, same with a Montana Gould 95gr JHP @ 1550FPS / 147PF not being made right now..
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This covers 99.99% of the MPX issues:
1. How often do you clean the gas system= gas plug has an expansion chamber when that fills up with Carbon/Lead/Poly Coating you are reducing the volume and delay to extraction. I.E you are attempting to extract while the case is still expanded against the chamber walls
2.When have you last changed the extractor spring= see #1 above this adds stress to the extractor spring and overworks it reducing the extractor springs ability to maintain grip on the cartage case
3. How often do you clean behind the extractor= build up of Carbon/Poly Coating reduces the extractor springs ability to move and maintain grip on the cartage case
Usually I shoot 135gr Blues over 3.5gr Sport Pistol=Coated bullets are bad for the gas plug expansion chamber see #1 above… to use them your clean out on the gas plug would need to be every 200-300 rounds.. I never had good results with Sport Pistol fast burn rate powders fill the gas plug expansion chamber to fast and start the extraction process while the case is still expanded against the chamber walls see #2 above. MPX is better off with medium burn rate powders N330,N340,CFE pistol..
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20 hours ago, chase214 said:
How well does that comp work I saw earlier their gen 1 comps were in stock
This is the Micro JTTC, 4140 PH Stainless Steel. all of their previous comps are 7075 Aluminum.
Works well flatter than any thing you can do with a carry optics set up, dot stays in the center of the glass vary easy to track no real corrections needed between shots, BUT it is NOT at an open gun level of performance. If i was doing that 2 gun Nationals thing I would pair this up with my MPX.
I run 124 HST (Standard or +P)and Speer 124 Gold Dot...
I like carry comp guns my first one was a Glock 17 with a Jarvis single chamber comp back in 1990-1991..
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8 hours ago, Galun said:
I just developed a load that I really liked out of my gmr-15 with 14.5 inch barrel and pinned new style compensator (the one with port on top). 5.9 grains of long shot, Hornady 0.355 100gr FMJ, 1.08 OAL. Makes around 140-145 PF. Great snappy feel, dot bounced back quickly and felt like it barely moved, flat and accurate.
For my MPX's 100gr FMJ 6.4 CFE Pistol 1497Fps or 95gr Montana Gould JHP 6.4 CFE Pistol 1515 Fps = super flat minimal dot movement
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I went with the 4.7" so I could use the Armory Craft Guide rod and 1911 springs.
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wrong thread
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3 hours ago, Bdh821 said:
Geez maybe ill change mine out as it's one of the few parts I havent changed yet.
My maintenance issues went down 80% after Igot a big Ultrasonic tank the whole barrel will fit in (catty corner), this is the solution I use:
Got a cheap Tea Ball from Wallmart for the small parts...
Got to keep the expansion chamber in the gas plug free of carbon/lead build up, as it fills up you decrease the delay prior to the start of the unlock/ extraction process
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4th time I have heard /seen this happen.. 1st was AZ state PCC match stage 10 guy on my squad plug never found, detent was sticky..2nd local match guy on my squad plug was found, detent was sticky... Last month a friend called while I was driving home from a match, Plug not found told him to check the detent and gave him info on a replacement plug..
My theroy is that if the detent is not latched in solid (or is sticky due to carbon fouling) it starts to rotate due to vibration then the gas acts on the side of the slot to finish the rotation and eject it..
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I had both laser (CMR-206) and 45 offsets. Used the laser 3 times outside in matches and 10 times for indoor matches use the 45 offsets a lot more. Kept the laser around as it's weight was nothing, up until I changed hand guard profiles and removed the laser for ergonomic reasons.
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On 12/5/2020 at 7:59 PM, ddc said:
How does the "grip-ness" compare to an epoxy/silicon carbide treatment?
I do a grip texture in zones based on how your hands sit plus the reduction and undercuts combined with recoil give you the bight..sil carbide is just their and has a build up..
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12 hours ago, The Donald said:
Thanks, with so thought I see how to use the tip. I have a bunch of AR grips to practice on.
I have been doing grips since 1990 with thousands done....Sig,STI,Glock, M&P,H&K...evey type of polymer is different.. angle of attack with the iron and duration is critical... the tungsten infused grip react different..
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5 hours ago, The Donald said:
What tip did you used to stipple like that?
Flat tip.
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PCC is the only division that translates easy... Load no more than 32 rounds in a mag (+1 chambered if a loaded start), min bullet weight of 115gr max velocity of 1640fps... leave your 90- 100gr loads at home
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Done 4 or 5 now 2 samples attached:
- Raised the trigger guard undercut
- Raised, deepened and narrowed the beaver-tail
- Thin and radius the front and back straps
- Stippled
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1 hour ago, BillChunn said:
What is the NP3 sear? Is that referring to the Robar NP3 coating?
Apparently Robar closed shop, re-opened under a different name and is now referring all firearms work to outside companies. (found this in the Sig Forum).
BC
P320 Competition Trigger System
https://grayguns.com/product/p320-competition-hybrid-trigger-system/
- Precision-ground custom sear, polished and finished in hard nickel PTFE. Specifically designed for competition or range use only.
hard nickel PTFE = NP3
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GG Hybrid competition kit (with the NP3 sear) competition sear springs + the heaver trigger return spring +armory craft trigger. have about 0.012" pre-travel, zero over-travel , positive reset.....
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Romeo8T primary and Romeo4M offset.
JP GMR-15 or Sig MPX PCC final considerations
in Pistol Caliber Carbine
Posted
Depth should be