Fast powers?

[Neomet]

Trying to find a load for my MPX carbine and I have to say I am somewhat surprised at how many people are using fast powders (TG, etc).  I'm thinking long barrel = slow powder.  Then again, I'm thinking AR 15 rounds, not heavier pistol projectiles.  Anyone care to educate the slow kid in class?

[MemphisMechanic]

A fast powder results in nearly all of the gas being used / expanded by the time the bullet exits the barrel.

Heavy bullets, fast powders, and light recoil springs shoot more softly and result in less muzzle flip.

All three are the opposite of what you would think to use to minimize recoil, but it's tried and proven a thousand times over.

[bmiller]

I tried using slower powders (autocomp, hs6) in my blowback gun.  Didn't work well. It blew a bunch of unburnt powder and carbon back into the action.  The lower was extremely bad.  That was with a 5.3 oz buffer. Heavier might help, but I doubt it. I have been playing with lighter bullets and bullseye. Mainly because that is what I have on hand.  I made a comp similar to an egw open gun comp, it does nothing for recoil, but does seem to tame dot bounce.  Initially, I thought my pcc would act similar to my open gun, I was wrong.  Turning up the power factor does nothing but add recoil in my gun.  I would be interested in your results with your mpx. I have have had the same thoughts about it.  I shoot coated bullets, so I am holding off on one until I see how they handle dirt and crud.

Edited November 12, 2016 by bmiller

[Les Snyder]

a couple of observations from years ago about cast bullets....the Winchester ball process powders seemed to not burn the base as much as the faster propellants, even in loadings over 1400fps (recovered metallic silhouette bullets)...the rear end steers the bullet... longer bearing surfaces tend to make my 9mm pistols shoot more accurately...

intuitive, but not necessarily true... a low standard deviation in bullet velocity may imply a good balance in the system...

I ran some Bayou 135s Wednesday... 3.7 of WSF gave me 1105fps with a standard deviation <5 fps... this is still 149 power factor, but food for thought... will test the 3.5 and 3.3 loads this week.. regards

[CZ85Combat]

Fast powder is the way to go. I am using 2.5gn of N310 with 147gn Blue Bullet @ 1.140, 901 fps, 132pf   standard deviation of 4 fps

[Les Snyder]

decided against loading two different powder charges... the 3.5 WSF 135 Bayou just squeaked 125.5pf out of the Briley barrel in the G34... looks like I'll settle on 3.6 WSF 135 Bayous for both...I can live with the 145pf in the carbine... shot the 3.7 Bayou coated bullets at the last match, and seemed to have less lead build up in the comp than the open base Precision Delta , but too soon to actually tell

[JonF]

Then again you have an MPX which employs a gas driven recoil mechanism so a slower burning powder may benefit you. I have a DI 9mm carbine and i *have* to use a slower powder (3N37) to get enough pressure, volume and dwell time to get the bolt to cycle. I still only load for minor PF but that dwell time is critical for me. Understandably, the mechanics of a blow back and traditional delay lock breech pistols are different than gas guns so it going to be a different conversation and different solution (ie. fast powders for them). Of course the MPX is a factory gun built for factory ammo but it stands to reason that slower powders and dwell time may be amicable for its type of mechanism. Some anecdotal evidence is the folks with trouble cycling 147's load/poly reloads through the Sig which will have a non-trivial lighter powder charge than a 115gr FMJ factory load.

[Hunter1998]

I use 5.5 CFE with 124 hp's with great success. Clean and very accurate in mt GMR