9x19mm AR-15 Folks....I need to pick your brains.

[cslinger]

Ok so I want to eventually build a 9x19mm AR15 on a Bushmaster lower.

I was thinking about either a Rock River or Oly upper. I want it set up to use Sten mags(unless people have had bad experiences) but I have some questions.

1st, what is the deal with the hammer? Do you really need to use a 9mm specific hammer?

2nd, buffer tube/spring. Does it have to be 9mm specific?

3rd, what are the best mag well adapters to use.

4th am I missing anything?

Thanks
Chris

 

[Redlg155]

Well..from my experiences..

I shoot a Rock River Mid length upper with a Bushy lower and Rock River mag block, which is also a Colt pattern. I also use a 9mm buffer, also from Rock River. The Oly uses a slightly diffent system and a sten mag setup.

I can only answer questions for my RR system.

1. It is advisable that you get a 9mm hammer. The 9mm hammer may be used with a .223 as well, but you may suffer from light strikes since the hammer mass is less. You can also modify a .223 hammer for the 9mm. The major difference is the vertical clearance needed to work with the 9mm bolt. There is a lot of good information on how to do this over at AR15.com in the pistol calibers section.

2. The buffer does not have to be 9mm specific, but it is generally advisable that you go with a 9mm buffer in a shorty or collapsible stock. There are a lot of folks out there running a 9mm upper with a standard buttstock and buffer. The spring is the same for 9mm and .223. However, there is a plastic spacer that RR makes if you choose to use a 9mm buffer in a full length stock. As I understand things, the 9mm buffer is essential with full auto fire, but not as crucial for semi. I use a 9mm buffer in my shorty stock just in case. Also, the 9mm buffer is the same length as a CAR buffer, only that is has more mass.

3. I like the Rock River mag well adapter based on the Colt system. It uses Uzi mags that have a mag catch opening cut into the magazine body. The downfall is that uzi mags are costly when compared to the stens. The benefit that I like is that you use the standard magazine catch instead of a paddle release normally required for the stens. There are also a couple of new mag blocks out on the market that might be worth a look at. Again, they are discussed in detail over at AR15.com. I bought mine to have realistic training at a fraction of the cost of real 5.56 ammo. Using a paddle release negates that advantage for me.

I'll try to type more later..I'm off to the movies!

Good SHooting
Red

 

[Fly320s]

I have a RR 9mm upper on my Bushy lower. I forget the model, but it's the carbine version with a flat top and short handguards. I also use the modified Sten mags with the correct adapter. I can't remember the name of the adapter, but you can find it on AR15.com. I think I bought it from Brownell's.

1. The hammer only needs to be filed a fraction of an inch. The part that needs the filing (polishing is more like it) is the top corner closest to where it contacts the firing pin. That corner is the part that will hang-up on the 9mm bolt because the 9mm bolt does not have the relief cut on the bottom. I actually ground my hammer down too far and had to replace it. On my second try I used my Dremmel to take off just a hair of metal. I didn't measure it, but the thickness could not have been more than 1/16 inch. Just enough so that the bolt clears the hammer on return to battery.

2. I use my stock Bushmaster buffer and spring. No mods whatsoever. Winchester USA (white box) 9mm runs great. UMC 9mm runs really, really slow. Must be lower pressure. (Semi-auto only. bummer)

3. I've only tried the adapter I have now. It takes a ton of milling on the adapter to get it to work with the Sten mags and to fit in the AR15 well. But, once you get it in, it works fine.

4. Maybe. The Sten mags themselves must be modified to work correctly. An AR15 style notch must be cut into them so that they will latch into place. There is no last-shot bolt hold open.

Modifying the mags is relatively easy. I did mine with the ever popular Dremmel and some cutting discs for tempered steel. The cuts are not beautiful, but they work.

The mag well adapter is held in place with three small set screws and the mag catch. It will stay secure for awhile, but prolonged firing will require you to tighten the screws. Some folks have a dedicated lower that they drilled and tapped to make the mag well adapter a permanent fixture.

I love my 9mm AR15 setup. But, if I had known about the Beretta Storm I would have bought one of those instead. My AR15 is great, but the work and expense to get it running was a serious pain. Less money than a Storm, but I prefer to pay and play. Call me lazy.

I don't really enjoy, or have any skill for, machining metal. The mags I did myself. The adapter I took to a gunsmith with a milling machine.

If you do decide to do it, read the AR15.com thread two or three times. Some of the original posts have been deleted so it might be hard to follow, but all the info is there.

I'll answer more questions if I can.

Good luck.

edited to add: My Sten mags use the standard AR15 mag catch. I drop the mags using the same mag release/catch that came on the rifle.

 

[carpettbaggerr]

Mag adapters:


http://www.kurtskustomfirearms.citymax.com/catalog/item/29585/386988.htm


http://www.socommfg.com/9adapt.htm

 

[Fly320s]

CSlinger, any progress?

 

[Molly]

I had the Oly upper on a BM lower. They worked fine with no mods - when they both arrived, I attached them and was shooting in about two minutes. I used the socommfg.com block with the sten mags. It worked fine as far as the mag fit, removal, etc. but loading a sten mag is very difficult and I could not do it without the rather costly brass loader from ohio ordnance. Plus, when the mag was full, the first round almost always failed to feed. However, the rest of the rounds shot perfectly everytime. I always used Greek Olympic brand 124gr that had subgun printed on the side, which is to imply that they were loaded to be hotter than standard. They seemed to be.

I did nothing to the firing pin, buffer, bolt, or anything else. In fact, once I put the gun together I don't think I ever took it appart to even look inside.

 

[cslinger]

No Progress Really

This is my September project....if you know what I mean, fingers crossed, letters written, phone calls made, i's dotted and t's crossed.

I am picking up a collapseable stock BM lower as soon as the ban is lifted. This will go on our BM shorty AK brake and that A2 lower will be the designated pistol caliber lower. At least that is where I am going with this at this time. I may end up building a flat top semi auto M4 out of it with all the evil goodies just because.....well just because darn it.

The ban never really effected me so much as I like single stack handguns, .45s and could really care less about bayonet lugs, flash hiders etc.

The only thing that really torqued me off personally is the stock. I want the ability to fold or collpase the stock on the short AR. Actually the whole law torqued me off but affected me little.

Anyway come September I am picking up the collapseable stock BM lower, 6 Walther P99 full caps and a few SIG P229 full caps and they will be my celebrate the death of the stupid law party favors.

I have heard from many people the Oly upper usually works without any modification, except the mag well block, so that is probably the route I will take if I go 9mm. Besides they give me discount for my C&R

thanks again,
Chris