9mm AR

[Jherexx]

Thinking of building an AR in 9mm because I dont have a pistol cal AR and most of the pistols I shoot are in 9mm. Also, this would simplify ammo logistics when going to the range.

Any preference of which system to build, Colt or Oly?

From what I have been reading on the diffrent boards, the Colt system is more finicky and takes more tuning than the Oly system. Anyone have experience on both these systems?

[the_man]

Colt systems are more common. The oly system use modified sten mags. While the colts have their own mags but after market mags are available. I didn't like the case ejector for the oly's either it was a little bent wire and I was not sure of it's durability.

I would stick to the rra or colts for part availability.

[Colorado Osprey]

Colt systems are more common. The oly system use modified sten mags. While the colts have their own mags but after market mags are available. I didn't like the case ejector for the oly's either it was a little bent wire and I was not sure of it's durability.

I would stick to the rra or colts for part availability.

The modified mag thing is untrue. Things have changed.
Oly pistol cal AR's come with Polymer mags. They are sold by and labeled as Olympic mags. Yes, you can still use old modified sten mags and you can also use unmodified sten mags with a magwell adapter like SNS and Hahn. Personally I actually prefer the reliability and cheap sten mags.... modified or using a mag well adaptor. If you weld you can make the adaptor and put togther mags for under $10 ea for 32 round mags uncluding the cost of the mags!

Olympic designed the pistol caliber uppers. Colt and other manufacturers have repeatedly tried to buy patent rights to build Olympic's design. They are always turned down. Even Colt knows that Oly's design is superior.

For reliability there is no comparrison.. Oly hands down.

The ejector on the Oly system is rock solid and reliable although it seems like a flaw design. I agree that when I was looking into getting a pistol cal AR I asked how often the little springy thing needs to be replaced. A tech person at Oly said that they last between 30-50,000 rounds. I bought a spare when I got my 1st Oly pistol cal upper. I have since got a couple of more in different calibers and haven't worn any of them out. My 9mm upper has about 10,000 rounds through it.

BTW, a replacement ejector spring was $2.49 when I bought it.

What is great about the Oly uppers is the fact that if you already have a 223/5.56 AR you just need to swap out the upper to a Oly pistol cal upper. No hammer, buffer or buffer spring changes. They are really that simple as to just slap it on and go.

There was a lot of negative press on Oly guns of the past(tight mag wells and cast lowers). Unfortuately the pistol cal guns get lumped in with the bad press. This is truely unwarranted as these are the best pistol cal uppers you will find.

If you gave me a Colt style upper I would immediately sell it and get another Oly.

Also don't forget Oly pistol cal uppers are available in multiple calibers. You don't have to limit yourself to 9mm. There is 40s&w, 10mm and 45ACP also. In the past they were available in 9x21, 9x23, 357 SIG, 45GAP, 41AE, 45 Win Mag, 7.62x25, 30 carbine

If you carry a Glock you might also consider a Glock style lower that takes Glock mags in 40 or 9mm as well. They are the the GL9 and GL40 models.

[Ranger]

This has always been a curious topic for me. Other than having lower ammo costs since you're firing pistol cals, is there another reason folks do this conversion?

[Hoser]

This has always been a curious topic for me. Other than having lower ammo costs since you're firing pistol cals, is there another reason folks do this conversion?

Cause I can.

[Ranger]

Cause I can.
So, it's sort of like "why does a dog lick it's balls - because it can" kind of thing? :)

[Jherexx]

The modified mag thing is untrue. Things have changed.
Oly pistol cal AR's come with Polymer mags. They are sold by and labeled as Olympic mags. Yes, you can still use old modified sten mags and you can also use unmodified sten mags with a magwell adapter like SNS and Hahn. Personally I actually prefer the reliability and cheap sten mags.... modified or using a mag well adaptor. If you weld you can make the adaptor and put togther mags for under $10 ea for 32 round mags uncluding the cost of the mags!

Olympic designed the pistol caliber uppers. Colt and other manufacturers have repeatedly tried to buy patent rights to build Olympic's design. They are always turned down. Even Colt knows that Oly's design is superior.

For reliability there is no comparrison.. Oly hands down.

The ejector on the Oly system is rock solid and reliable although it seems like a flaw design. I agree that when I was looking into getting a pistol cal AR I asked how often the little springy thing needs to be replaced. A tech person at Oly said that they last between 30-50,000 rounds. I bought a spare when I got my 1st Oly pistol cal upper. I have since got a couple of more in different calibers and haven't worn any of them out. My 9mm upper has about 10,000 rounds through it.

BTW, a replacement ejector spring was $2.49 when I bought it.

What is great about the Oly uppers is the fact that if you already have a 223/5.56 AR you just need to swap out the upper to a Oly pistol cal upper. No hammer, buffer or buffer spring changes. They are really that simple as to just slap it on and go.

There was a lot of negative press on Oly guns of the past(tight mag wells and cast lowers). Unfortuately the pistol cal guns get lumped in with the bad press. This is truely unwarranted as these are the best pistol cal uppers you will find.

If you gave me a Colt style upper I would immediately sell it and get another Oly.

Also don't forget Oly pistol cal uppers are available in multiple calibers. You don't have to limit yourself to 9mm. There is 40s&w, 10mm and 45ACP also. In the past they were available in 9x21, 9x23, 357 SIG, 45GAP, 41AE, 45 Win Mag, 7.62x25, 30 carbine

If you carry a Glock you might also consider a Glock style lower that takes Glock mags in 40 or 9mm as well. They are the the GL9 and GL40 models.

Confirms what I have been reading in my research. Oly style more reliable, colt style more availability. Now the search begins for an Oly upper in 9mm.

[Jherexx]

Cause I can.

exactly

[DeusExMachina]

I heard a 9mm AR has more recoil than a 5.56. Is that true?

[Colorado Osprey]

Yes, the 9mm or any blowback will have more recoil than a gas gun.
Some people have done them with the piston set up as a gas gun and they have virtually no recoil.

It was surprising the 1st time I shot one. It is not bad, similar to a 223 bolt gun.

[BPTactical]

If you are converting a standard 5.56 lower to 9mm, make sure you get the correct buffer and spring.

[Colorado Osprey]

If you are converting a standard 5.56 lower to 9mm, make sure you get the correct buffer and spring.

With the Oly system there is no need...

[Hoser]

If you are converting a standard 5.56 lower to 9mm, make sure you get the correct buffer and spring.

Nor the Rock River. All you have to do is change out the hammer unless you have your bolt ramped. In that case, just swap uppers and go.

My little 5.5 inch upper with AAC can runs like a sewing machine.

[BadShot]

I've had a complete RRA 9mm AR for years, bought under the same premise as the OP. Great training gun, lower ammo cost (at the time), pretty fricken reliable with good mags. I use the C-Products metal mags, tried out the cheaper promag poly's and that there was my problem. Since switching to all C-Products mags, the thing runs in a rather boring and reliable fashion. The setup pretty much mirrors my go-to carbine and I've run it in a high volume class already (hence the lesson about cheap ass poly mags).

Not really given the Oly's a look, but were I going to look at doing this from scratch, I'd most likely start with an Oly. Then again, might one day go for a .45 Cal version :)

So you've got options and I'll absolutely stand behind the RRA 9mm. It's a dedicated platform, but that was my intent. Its a training tool, not a go to weapon. I don't think the operation or recoil is noticeably different than any other AR I have.