9MM AR MASTER THREAD

[MCASSgt New River]

Does anyone have one of the new Hahn blocks with the "M4 type" feed ramps? Can anyone state a benefit of the Top VS Bottom loading VS Dedicated blocks? I have the RRA block currently, smooth feed ramp, but sold off the donor 9mm rifle and need to replace the block & bcg and I'm not sure whick I wanna go with. My sbr will ONLY be used in 9mm so even a Dedicated Block would be fine if it makes a real differance.

Thx,
MCASSgt New River

[chrismartin]

Does anyone have one of the new Hahn blocks with the "M4 type" feed ramps?

I haven't seen those. Have a picture?

Can anyone state a benefit of the Top VS Bottom loading VS Dedicated blocks?

Dedicated: Inserts from the top, held in by the bolt catch and upper, mag hold-open works, uses 5.56 bolt catch
Top: Inserts from the top, held in by the upper, hold-open typically does not work (bolt hold open may work with hahn if you install 9mm bolt catch.
Bottom: Held in by mag release and/or set screws, hold-open works

I went with the dedicated. bolt catches are off-the-shelf 5.56 parts, they are pretty simple to remove if needed or broken. Some bottom models with set screws are nice because you can move them up and down a bit if you have feeding issues. However, that also means that they can move on their own if the screws become loose.

[MCASSgt New River]

Does anyone have one of the new Hahn blocks with the "M4 type" feed ramps?

I haven't seen those. Have a picture?

Can anyone state a benefit of the Top VS Bottom loading VS Dedicated blocks?

Dedicated: Inserts from the top, held in by the bolt catch and upper, mag hold-open works, uses 5.56 bolt catch
Top: Inserts from the top, held in by the upper, hold-open typically does not work (bolt hold open may work with hahn if you install 9mm bolt catch.
Bottom: Held in by mag release and/or set pins, hold-open works

I went with the dedicated. bolt catches are off-the-shelf 5.56 parts, they are pretty simple to remove if needed or broken. Some bottom models with set screws are nice because you can move them up and down a bit if you have feeding issues. However, that also means that they can move on their own if the screws become loose.

Picture as requested:


I decided to go with the bottom loader, not exactly the one pictured, as being able to move up or down in the magwell seems like it could help feeding issues that may come up.

THX !

[chrismartin]

The picture is what Hahn has been supplying for some time now. I have those ramps on my dedicated block.

Chris

[rob_s]

I have the dedicated as well, and it has those same ramps.

[MCASSgt New River]

I have the dedicated as well, and it has those same ramps.

Will the last round bolt hold open work using the dedicated block work with mod'd uzi mags?

[rob_s]

I have the dedicated as well, and it has those same ramps.

Will the last round bolt hold open work using the dedicated block work with mod'd uzi mags?

no clue. I don't have any. Only mags I have a Colts and Crap-Products, both of which hold open (provided that the Crap-Products feed well enough to get to the last round, which isn't guaranteed).

[Walker Precision]

I have the dedicated as well, and it has those same ramps.

Will the last round bolt hold open work using the dedicated block work with mod'd uzi mags?

Nope. The Uzi mag followers lack the tab to activate the bolt stop.

[srt-4_uk]

First let me say I am an AR newbie but I am not new to guns. I am looking into piecing together my 9mm AR and I had a few questions. I planned on using a RRA 7" upper with a SBR'd AGP lower. Besides the upper, Ill need the mag block, buffer, and hammer. Is there anything else I would need? Also the upper has a railed gas block with a free float tube hand guard. I wanted a longer hand guard tube but it doesn't look like it would clear the gas block. Am I right in assuming the "gas block" is only for a front sight and is removable since the 9mm works on blow back?

[MCASSgt New River]

First let me say I am an AR newbie but I am not new to guns. I am looking into piecing together my 9mm AR and I had a few questions. I planned on using a RRA 7" upper with a SBR'd AGP lower. Besides the upper, Ill need the mag block, buffer, and hammer. Is there anything else I would need? Also the upper has a railed gas block with a free float tube hand guard. I wanted a longer hand guard tube but it doesn't look like it would clear the gas block. Am I right in assuming the "gas block" is only for a front sight and is removable since the 9mm works on blow back?

SRT,

Welcome to the wonder world of 9mm Ar's! I love mine once I got all the quirks sorted out. I found that using a heavier buffer annd buffer spring helped quiet down the ejection port noise when shooting suppressed.

If you plan on going suppressed will you thread your RRA 7" or replace it with a TROS? You are right in the assumption that the 9mm is a blow back design and thus no gas tube/block is needed. I run my buis flip up on my Spectre length handguards and it works just fine.

MCASSgt New River

[srt-4_uk]

Thanks for the input.

The RRA is already threaded for 1/2x36. I had planned on getting an adapter to convert it to standard 1/2x28 but now that you say it, I am liking the 3 lug QD idea.

The Spectre length hand guards are 9.5" right? That is about the length I was looking for but they dont make that length in the style I wanted. They only make 4.2", 7.2" and 12.5". Ill probably just get the 7.2" so I'm not adding any extra length if I'm not shooting suppressed.

[MCASSgt New River]

...if I'm not shooting suppressed.

Thats the funniest thing I have heard all day.

[srt-4_uk]

touche

[srt-4_uk]

So what mags does everyone recommend? I have the RRA Mag block. I saw mixed reviews from the C-products. How about the Bushmaster poly mags? How about Metalform?

[MCASSgt New River]

So what mags does everyone recommend? I have the RRA Mag block. I saw mixed reviews from the C-products. How about the Bushmaster poly mags? How about Metalform?

IMHO I would go with Uzi mags. You can buy a 3 pack with pouch from Cheaper Than Dirt and mod them yourself. It is a learning process but they will be keeps once you get everything sorted out. I love mine and plan on ditching the C-Products at some point.

[srt-4_uk]

So all I would need to do is cut out slot for the mag catch correct?

[MCASSgt New River]

So all I would need to do is cut out slot for the mag catch correct?

Yes, what I did was:
1. remove (or swing it out of the way) mag catch,
2. insert the mag,
3. use a pencil (mechanical will make it easier due to the very thin lead) to mark where you need to dremel,
4. measure again, ensuring upper will close and that the rounds are as close to the feed ramp as possible,
5. measure one more time before you cut
6. take your time and have fun.

MCASSgt New River

P.S.
Measure, measure, measure then cut...you only get one shot at the process.

[delta9mda]

i new to all of this and have questions:

why not start with a dedicated lower (cmmg) that has the mag block built in? are there any issues with this set up?

[WasDustyJacket]

That is what I have but then it limits you to that one caliber.

Using a removeable block gives you options to swap calibers/uppers.

[MCASSgt New River]

That is what I have but then it limits you to that one caliber.

Using a removeable block gives you options to swap calibers/uppers.

+1

I run 9mm & .22lr on my 5.56 lower.

[rob_s]

Removing mag blocks to change calibers is something I once thought I might do, but given I don't even change out uppers that's a fantasy world I'm no longer living in. *IF* I thought that FA was something of use to me I *might* change my mind about that, but I have no use for FA anyway.

I've seen a few dedicated lowers that look interesting to me. Primarily the ones that change the profile of the entire magwell from the outside as well, as I think they give a better visual index for speed reloads, and provided they are designed correctly should require less tinkering. The Double Diamond is one such, if a little pricey.

[delta9mda]

i do not intend to swap calibers and all of that. that will be taken care of with dedicated .223 guns.

what i want to do i make an sbr 5-6" barrel and have an 8" can for it (or something like that).

[chrismartin]

The Double Diamond is one such, if a little pricey.

The Double Diamond is pretty cool because they will engrave it from the factory. Ready to SBR right from ordering it.
Yes, it looks a little pricey, but $100 "normal" lower + $200 Hahn mag block + engraving is more than the double diamond with engraving. I know you can get cheaper blocks than the hahn, but I don't think the DD is a bad deal all things considered. Yes, it should maybe be a little cheaper, it's not like it's much more work than a 5.56 lower, but it is a specialized lower volume item.

[Davo5o]

Anyone run one of these LWD lowers yet.

I'm planning on getting one and doing a 10" build. Any help greatly appreciated. Thanks

http://www.lonewolfdist.com/Detail.aspx?PROD=186982

[srt-4_uk]

Thanks to this thread, I got my 9mm setup running great. I ended up using the C products mags and put about 400 rounds through my setup last week with no problems. Now the only problem I have is the stock AR trigger. I do not have a ramped bolt but is there any problem running an aftermarket trigger like a Timney, JP, or Geissele?