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Nimitz

Sig MPX and Blue Bullets

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Given how much cheaper I can get Blue Bullets than the Extreme plated bullets I'm currently shooting in my STI I decided to by a sample pack to check them out.  So I made up a dozen Extreme plated124s & a dozen 125 Blue Bullets.  Same OAL for both (1.15) and same powder load (4.0 g WST).  Shot the Extremes first without issue.  Attempted to chamber the first Blue Bullet and the bolt wouldn't lock forward.  Worse, the round ended up stuck in the chamber and I could not pull the charging handle back to eject.  Ended up taking it apart at the range and was finally able to pull the charging handle back which separated the case from the bullet ... then used a squib rod to get the bullet out.  A good chunk of the polymer coating was scraped away at the sides near the base of the bullet.

Since this was literally the very first Blue Bullet I tried this does not bode well for using these in my MPX.  Anyone else using Blue Bullets in their MPX or is it just me?

I then loaded up a half dozen to try in my STI Steel Master and they worked flawlessly ....

If it weren't for the fact that the 124 Extremes at the same OAL worked without issue I might have chalked it up to needing to load shorter but that doesn't seem to be the case ...

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I'm loading 125 Gr Blue Bullets for my MPX rifle. Initially, I was shooting what I had loaded for my 9mm Tanfoglios. Those wouldn't cycle at all in the MPX & I was getting failures to extract/eject.

I spoke with a friend (who is a USPSA M class PCC shooter). He told me he loaded his rounds long to an OAL of 1.2. So, I followed his advice. they functioned flawlessly. I have since shortened them just a little bit to 1.18-1.19 and they run great.

One thing I have discovered is once the rifle gets really filthy, it won't chamber these rounds. Outside of one box of FMJ That measured to 1.15 (and ran well), all i have ever shot out of my rifle is the blue bullets.

Hope this helps.


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Your OAL is too long.  The projectile is hitting the lands and getting stuck on them.  You will need to shorten your OAL.  Of course watch your charge weight as 9mm is a small case and changes in OAL can make big differences in case pressure (and PF).  

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fair enough but the 124 Extremes don't really look any different in their profile/shape and they worked just fine ... can they be that sensitive to profile shape?  What OAL are you using for your MPX?

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it's hard to do the 'plunk test' with a MPX barrel since you can't get your fingers down far enough to see if the case rotates freely but I can drop a case in and then turn the barrel upside down to see if it falls out.  Anything else I can do to determine that the round is not too long and is hitting the lands?

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Hello: Lower the charge weight and load to 1.125" OAL. That should be short enough to clear the lands. Thanks, Eric

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I'd also mic the bullet diameter. Could be just a little bigger and enough to cause problems.

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Yes, that's what actually worries me. Over in the 9mm reloading subforum we're having a discussion about the variance in blue bullet weights and diameters ... The weights can vary by as much as 2 grains although I'm less concerned about that.  The variance in diameter I saw in jsut picking a handful of random bullets seemed to be a potential issue ... But I don't know how much over the actual barrel diameter becomes a problem ...

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I run my 9mm 124 bullets @ 1.125. Including blue bullets. I also use MTG bullets and Bayou with out issue.

 

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3 hours ago, Nimitz said:

Yes, that's what actually worries me. Over in the 9mm reloading subforum we're having a discussion about the variance in blue bullet weights and diameters ... The weights can vary by as much as 2 grains although I'm less concerned about that.  The variance in diameter I saw in jsut picking a handful of random bullets seemed to be a potential issue ... But I don't know how much over the actual barrel diameter becomes a problem ...

Your plated bullet is probably .355 and your coated lead Blue Bullet is probably at least .356 or so. If your barrel has a tight, short throat you may have to go very short to get the coated bullets to fit. I've got a KVP/Faxon barrel that's like that. If you're going to shoot lead bullets, they need to be sized to the throat. 

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I know I had to throat ream my Faxon barrels to work with my 125 blues at 1.135. Seems like most of  the 9mm carbine barrels are all made with tight throats.  The Xtremes that I used worked fine for me too. 

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14 hours ago, Nimitz said:

fair enough but the 124 Extremes don't really look any different in their profile/shape and they worked just fine ... can they be that sensitive to profile shape?  What OAL are you using for your MPX?

The profile (ogive) of the 125gr Blues and Xtreme are pretty different allowing the Xtremes to be loaded longer.  In any gun the max OAL for the Xtreme will be longer than the 125gr Blues, but that's only going to be an issue if your gun has a short throat like I guess your MPX does.  If you want to use Blue Bullets in a gun with a short throat get the 135gr.  The truncated cone profile allows them to be loaded much longer than the 125gr round nose.

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What Southpaw said.  I have run Extremes at 1.150 in my MPX but my SNSs can be no longer than 1.128.  To test, and this is the only way to know max OAL your specific gun for certain, pull your barrel of drop a round in and then push hard on the back of the case with your little pinky.  Turn the barrel upside down and if it doesn't fall out shorten and repeat.  Banging the barrel on the workbench so it comes out does not constitute a win.  :-)  

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Fair enough.  I'll shorten them and redo.  I was hoping not to have to change my press to run MPX reloads but I guess I'll look at changing my STI load so I can use just one load for both divisions ...

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I run blue bullet 147s at 1.138 and they work in my mpx and suppressed even. Mine is a gen 1. 

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well, it looks like I'm going to have to try the 135 truncated cone Blue Bullets if i want to use them in my MPX .... The longest OAL I could get away with and still pass the plunk test was 1.04. ....

Is the 147 Blue bullet similar in profile to their 135 truncated cone?  or is the barrel throat different between the Gen 1 & Gen 2?  there was no way anything close to 1.13 is working in my barrel ...

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I wish I knew. All I know is my gen 1 eats everything and anything and runs like a raped ape. The gen 2s seem to have issues with ammo. 

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Hmmmmm .... I ran some 124 extremes at 1.15 without issue and took a few 147 extremes that I use in my CZ and STI (1.15) and they passed the plunk test without issue ... I'll invest $20 for a sample pack of the 135s and see.  They won't go it waste if my MPX won't eat them ....

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2 hours ago, Nimitz said:

well, it looks like I'm going to have to try the 135 truncated cone Blue Bullets if i want to use them in my MPX .... The longest OAL I could get away with and still pass the plunk test was 1.04. ....

Is the 147 Blue bullet similar in profile to their 135 truncated cone?  or is the barrel throat different between the Gen 1 & Gen 2?  there was no way anything close to 1.13 is working in my barrel ...

Yeah I had a similar situation with a Kaw Valley barrel where I'd have had to load way too short in order to use the 125gr Blues.  I don't know what's with PCCs and short throated barrels...

I've used the 147gr RN Blues and they're a similar profile to the 125gr so they also would need to be loaded too short for your MPX.  The 135gr Blues should work well for you.  Every Xtreme I've tried ,124 and 147 RN and 135 RNFP all have profiles that allow them to be loaded really long.

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Yeah, I love my Extremes but 6 cents/rd vice 7.4 cents/rd for Extremes is hard to ignore at 25,000/yr ...

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isn't that a difference of only $350 in a year's worth of bullets? i'd go with the 7.4c bullet that is no headache, no adjustment and pay the extra 350 for my ease and happiness while reloading and shooting.

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Have 125 grain blue bullets ordered (had a credit) I have a ton of ramshot competition powder anyone got any load data with this combo? Trying to make my mpx run.. it won't run the light loads 

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