AR-15 9mm adapter blocks: top or bottom load?

[Cameramonkey]

So I've got a lonely pistol lower that wants a mate. I decided to play around with a 9mm pistol and reuse that instead of buying yet another lower that is built for 9mm or playing with a 223 pistol.

So I see there are both top and bottom loading adapters. What are the pros and cons of each.

I assume both a pro and con of a bottom loading unit is that it is easy to remove. (pro that you dont have to take it apart, con that it is more likely to accidentally come out.

I'm not afraid of opening the rifle, and I dont plan on switching back and forth between rifle and pistol, so I assume I want a cheaper top feeding unit.

What am I missing?

 

[AngryRooster]

I've never seen it, but I've heard stories that the ones that insert from the bottom can split the receiver. Some of the blocks have an adjustment screw that tightens it in the receiver, if it's over tightened then it can crack things, or so I've read.

When my wife built hers she went with the Hahn dedicated block. She has other AR's and didn't care about switching calibers with this particular one. It's been flawless since the first round. CMMG lower (we tried on both our INGO lowers and they were both out of spec for the block. The block worked with fine with several other brands). PSA upper w/ BCG, proper Spikes 9mm buffer, PSA (Metalform) mags. ALG trigger.



I'll probably build one myself this fall or next year. On mine I plan on using the drop in top loading Hahn block.

 

[Simon6101]

Check out the Stern Defense Mag block. Goes in from the bottom and i just a couple of minutes you can switch back to another caliber. If you want to check thier stuff out I have one installed and would be glad to let you take a look.

 

[Ggreen]

Macon armory. If you have any issues and he answers his phone and explains how to fix it without having to dredge through half truths and biased forum posts. I can post detailed photos of mine if you want. It inserts from the top, so there is no way its coming out in a class or a competition. I don't like the easy change options, I used permanent loctite on the set screw s for security.

https://maconarmory.com/products/9mm-colt-pattern-magazine-well-adapter

 

[Simon6101]

My Stern Defense is being run with a Binary trigger and I have had no problems at all. It is held in by the mag release and has been completely reliable. I like this option because I can change calibers as I want to run with the Binary trigger.

 

[Cameramonkey]

Macon armory. If you have any issues and he answers his phone and explains how to fix it without having to dredge through half truths and biased forum posts. I can post detailed photos of mine if you want. It inserts from the top, so there is no way its coming out in a class or a competition. I don't like the easy change options, I used permanent loctite on the set screw s for security.

https://maconarmory.com/products/9mm-colt-pattern-magazine-well-adapter

Got mine, and looks good so far. Hoping to shake it out on the range later this week.

Though he appears to have changed them. They are now bottom loading. I couldn't get mine to load either way, then I noticed a hex screw with a large head on top at the back left corner as seen from the top. it hung over the edge of the unit slightly. Sure enough, Once I removed that I could insert it from below. When I put the screw back in it locked it into place.


Now the only weird thing is this pistol cycles manually just fine totally empty. but if I insert a mag with snap caps in it and pull the charging handle and release, the bolt hesitates for a brief but perceptible moment before it runs home. (and before it even gets close to the magazine)
Doesnt seem to do it when I cycle it with the mag out though. Could need to be lubed a bit better. Its a little dry ATM.

So you say this thing is adjustable? I do have to say that if so, its rather disappointing because no documentation was in the box, and I cant find any on his website.

 

[Ggreen]

Got mine, and looks good so far. Hoping to shake it out on the range later this week.

Though he appears to have changed them. They are now bottom loading. I couldn't get mine to load either way, then I noticed a hex screw with a large head on top at the back left corner as seen from the top. it hung over the edge of the unit slightly. Sure enough, Once I removed that I could insert it from below. When I put the screw back in it locked it into place.


Now the only weird thing is this pistol cycles manually just fine totally empty. but if I insert a mag with snap caps in it and pull the charging handle and release, the bolt hesitates for a brief but perceptible moment before it runs home. (and before it even gets close to the magazine)
Doesnt seem to do it when I cycle it with the mag out though. Could need to be lubed a bit better. Its a little dry ATM.

So you say this thing is adjustable? I do have to say that if so, its rather disappointing because no documentation was in the box, and I cant find any on his website.

Working on a write up now. Macon will hook you up with a call tho.

Basically the common problem is the ejector. My first step with a magwell adapter is to polish the feed ramp and the ejector. I lightly file the stamping burrs and I personally true the face that contacts the spent case. More contact, more consistent ejection.

With the upper off. Insert magazine and lock the lower in a vise. Take the bcg and run it back and forth in the lower and you'll see how the ejector rides. I lightly bend it inwards until it lightly touches the carrier.

Now put the upper on without the bcg. Many 9mm uppers are out of spec. They will push the ejector further inwards. That can stick your bcg messing with cycling. It can also push your mag in a weird way that drives the follower into the feed ramp. I have fixed multiple colt mag ar's this way.

Test firing you should be able to catch all of your spent brass in a small bucket. Ejector misalignment will lead to one ejecting forward and one back, followed by fte with a round feeding over the top. This is because the ejector is not riding the bcg.

I'll post a full write up this week. I've even got a cheaper adapter that requires a Lot of work to contrast.

There isn't a lot of good documentation on these adapters anywhere. One of the not easy to learn portions of ar building. I sat with mine for a few hours on a bench learning it, one call to Rudy at Macon would have saved time, but I wouldn't have learned how it really works.

 

[Sigblitz]

I've never seen it, but I've heard stories that the ones that insert from the bottom can split the receiver. Some of the blocks have an adjustment screw that tightens it in the receiver, if it's over tightened then it can crack things, or so I've read.

When my wife built hers she went with the Hahn dedicated block. She has other AR's and didn't care about switching calibers with this particular one. It's been flawless since the first round. CMMG lower (we tried on both our INGO lowers and they were both out of spec for the block. The block worked with fine with several other brands). PSA upper w/ BCG, proper Spikes 9mm buffer, PSA (Metalform) mags. ALG trigger.



I'll probably build one myself this fall or next year. On mine I plan on using the drop in top loading Hahn block.

 

[AngryRooster]

Really? I'm not the only one that has mentioned this, there are a few other people that had problems.

We tried the Hahn block in a total of 10 lowers. It fit perfectly in every one of them except the pair of INGO lowers we got from the first run. That's the reason we didn't order any more on the next run of them.

 

[Ggreen]

I had issues with a bci lower not being milled out properly. It is the only lower I own that wouldn't fit a rise armament drop in trigger. I dremeled it to fit, but it's the only lower I've ever seen have that issue.

 

[Sigblitz]

Really? I'm not the only one that has mentioned this, there are a few other people that had problems.

We tried the Hahn block in a total of 10 lowers. It fit perfectly in every one of them except the pair of INGO lowers we got from the first run. That's the reason we didn't order any more on the next run of them.

I wouldn't expect fitment issues from a personalized lower. That is surprising.

 

[Cameramonkey]

I wouldn't expect fitment issues from a personalized lower. That is surprising.

Personalization has no bearing on in/out of spec. If they mold/mill out of spec lowers for themselves, they are going to do the same for the personalized ones. Same steps for both up until they engrave it. (excepting crazy ones like the Spikes Tactical skull lowers, etc)