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Mag block issues

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I'm running colt style mags for my pcc and using a bottom inserted mag block.   After a handful of mag insertions the mag block gets pushed up slightly which starts causing malfunctions.  Mag block feed ramp starts feeding the rounds too high.  

Any recommendations to fix this issue?   Should I consider a new lower receiver?

I do not want to switch to glock mags.

 

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Posted (edited)

I use an aluminum mag block from Macon Armory, but it is similar to several on the market... bottom load and held in place with a button head cap screw and small washer... it holds tension by two set screws that apply pressure against the forward edge of the mag well.... which can be tightened down pretty well to help limit motion... but...any gun smith or competent amateur tinkerer should be able to drill and tap a small hole at the base of the mag block, and using a similar cap screw and washer to the one at the top, and lock the adapter solidly in place

Edited by Les Snyder

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I fought with a mag block for over a year with the same issue and it was the Macon Armory design. It would run good for a while then start having issues where the block had moved up in the magwell. The only real fix for this is a dedicated lower or permanently affixing the mag block. I chose a dedicated colt mag lower.   

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Get the Hahn dedicated mag block (adapter).  The dedicated version goes in from the top and is held in place by the bolt release.   I shot a Colt SMG mag fed PCC for many 1000's of rounds a couple of yrs ago with the Hahn and it was flawless.  They are not cheap (around $200) but worth it if you want to stay with the platform.   

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On 10/14/2019 at 3:43 PM, bwikel said:

I fought with a mag block for over a year with the same issue and it was the Macon Armory design. It would run good for a while then start having issues where the block had moved up in the magwell. The only real fix for this is a dedicated lower or permanently affixing the mag block. I chose a dedicated colt mag lower.   

Which lower?  Will it run hollow points reliably?

How much?

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On 10/15/2019 at 3:53 PM, LtdShooter said:

Get the Hahn dedicated mag block (adapter).  The dedicated version goes in from the top and is held in place by the bolt release.   I shot a Colt SMG mag fed PCC for many 1000's of rounds a couple of yrs ago with the Hahn and it was flawless.  They are not cheap (around $200) but worth it if you want to stay with the platform.   

Will it run hollow points reliably?

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22 hours ago, tk4 said:

Which lower?  Will it run hollow points reliably?

How much?

I was running mine in a Spikes SBRed lower. If you aren't trying to utilize an already SBRed lower I would just go with a dedicated  QC10 colt mag lower and be done with it. My mag block would run any ammo I fed it as long as it stayed secured in the magwell. 

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22 hours ago, tk4 said:

Which lower?  Will it run hollow points reliably?

How much?


Quarter Circle 10 has the best Colt mag lower out there. They run great and should feed pointier hollowpoints well.

 

If you want reliability with some of the fat wide HPs out there - a 147gr subsonic gold dot or HST? You want Glock mags imo.

 

Colt mags leave well over an inch of space between the rear of the barrel and the front of the mag, that’s just the way the rearward-located and 90* upright SMG mag is going to leave things. So there’s a lot of reliance upon a well-designed feedamp, which is something QC10 did very well.

 

Compare that to a Glock lower from QC10 or one of other other high end makers, and those damn near skip the feedramp: the rear half of the brass exits the mag only after the bullet was fed directly down the center of the chamber, barely kissing the feedramp. The mag rides higher and due to the forward lean of the Glock mag, the feed lips are right behind the barrel.

 

Edited by MemphisMechanic

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On 10/9/2019 at 7:52 AM, Shootymacshootface said:

I had the same issue. I basically pinned the mag block in place with 4 machine screws, but I'm not worried about hurting resale value of an 80% lower.

 

This...

I added just a single screw through my lower into the (Rock River / Colt mag) mag block after I pulled the block out with an empty mag once. Colt used to pin the block in place as seen below (They may still do so AFAIK)

 

 

coltmagpinned.jpg

Edited by GunCat

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On 10/15/2019 at 3:53 PM, LtdShooter said:

Get the Hahn dedicated mag block (adapter).  The dedicated version goes in from the top and is held in place by the bolt release.   I shot a Colt SMG mag fed PCC for many 1000's of rounds a couple of yrs ago with the Hahn and it was flawless.  They are not cheap (around $200) but worth it if you want to stay with the platform.   

I got the Hahn.  It is working great so far, even with my RMR hollowpoints (only a small sample size of hps though).

Thank you all.

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