I like to build my AR's myself from scratch. At some point I'll probably build a .22 AR, but I think a .17 HMR would be fun. However, I'm finding it difficult to find companies that manufacture .17 HMR AR parts. I found a few that sell complete uppers, but I don't want that. Does anyone know where I can get such parts? Does anyone sell a .17 HMR conversion kit similar to the .22 kits? Thanks boys and girls.

Also, comparing .17 HMR to .22, I have not researched much or compared with my calipers, but I think between the two the brass is the same diameter. I think if the barrel was properly chambered and the magazine was correct, a .22 bcg would work just fine. Such as a 5.56 bcg will also fit 300 AAC, etc. I can get any barrel threaded for the AR 15 platform via my gunsmith. Hmm, I may onto something here.

Thoughts?

I may be wrong but I believe the 17 operates at a significantly higher pressure than a 22 which poses some real issues with making them work in an AR. I could be wrong.

Parts kit?  Not too certain.  Did a quick search and found Alexander arms making 17 hmr goodies (I'm sure that's what you found as well).  But no conversion kit as far as what I saw.  I'm sure you could call them up and order the parts you wanted if you wanted to build up your own, but I didn't see anything regarding individual bbls or bcgs.

That's something I've considered. Saami lists the chamber pressures of the following rimfire cartridges as follows:
.22 short- 21,000 psi
.22 LR- 24,000 psi
.17 HMR- 26,000 psi

All are well under the tolorances the AR platform can withstand, as the .223 Remington has a chamber pressure of 55,000 psi, which I shoot from my .223 wylde chambered AR along with 5.56.
There's another .17 variant, I think .17hm2? I can't remember, anyway, it's the same length as the .22 LR, and probably nearly the same in pressure and would probably function perfectly in a .22LR mag, but I don't see much point in doing that, I'd just shoot .22LR. The .17 HMR is the same length as .22 WRM if I remember correctly.

If the barrel clambering and mag were correct, the question is whether the .22 conversion bcg could withstand the extra 2,000 psi. The AR platform itself can handle it no problem, but I don't know about a .22 bcg. I assume they're only tested to withstand the 24,000 psi of the .22 LR, not the extra 2,000 psi. Hmm.

Yeah I found Alexander arms as well. I suppose they might sell parts if I called them, which I think I'll give that a go and see what they say. I think all their barrels were stainless and only as long as 18". My .22 LR lever action barrels are longer than that. If they were to sell me a bcg and mag, I think I'd get the barrel somewhere else. However, I don't know if their upper receivers are mil spec, they may have some monkeyed thing that fits their own stuff. I think I'll contact them and see what they say.

If anyone knows anything else please chime in!

Doubt you will find any 17HMR AR parts from reputable sources. Semi-auto 17HMRs have been somewhat problematical. There have been rim splits with some lots of ammo in the past resulting in damaged magazines or worse. Ruger announced a 10/22 Magnum rifle in 17HMR a number of years ago. (I saw a prototype at the Shot Show) Ruger never went into production with the rifle due to problems. Remington produced a M597 17HMR for a while, but recalled them due to safety and functioning  problems and replaced them with a 22 WRM. Savage and Volquartsen still sell purpose built 17HMR semi-auto rifles. The 17HMR was developed from the larger diameter 22WRM case not the 22 lr, so a 22 lr BCG would not be suitable without mods. I still have an aftermarket 17HMR barrel for my Ruger 10/22 Magnum receiver, but don't shoot it anymore due to safety concerns. Alexander Arms apparently has done the research to build a safe 17HMR upper, I haven't shot one but the reviews are favorable. I am tempted with their current Black Friday pricing on the upper though! Good shooting! Vic

Yeah that was some info I came across as well, with pics of rim splits. I wonder if that issue has sense been resolved. The thing I like about the .17 HMR is higher velocity than .22 LR and a bit more accurate. I'll see what Alexander arms has to say about it and I'll post the results. If I can't find a safe functioning .17 semi auto system to build from I'll then probably seek out .22 WRM instead..... or..... settle for a .17 HMR bolt action, though not as fun.

However, I'm not committed to .17 HMR, though it fits the bill. basically I want to build something that's only slightly more powerful than .22 LR. If anyone knows of a caliber similar in size and velocity to .17 HMR, that has been proven safe for semi auto use that I can build into the AR platform, suggest away.

Bottom line: slightly better than .22LR, safe functioning ammo for semi auto, and existence of AR parts for such a caliber.

Not sure about the Alexander arms but the new semi auto 17hmrs are delayed blowback design. Most likely why they are rare.

Franklin Armory sells AR uppers in 17WSM. They are a gas operated design co-developed with Osprey. The Franklin uppers are rather pricey and AFAIK they sell only complete uppers and not parts. I believe there are some 22WRM uppers as well. Not too much else available. Vic

I have been waiting for a reliable model to emerge. I have had my Savage for years, and enjoy it.  I amassed a pile of the ammo, too

Yeah, if something doesn't emerge then I'll end up picking up a bolt or lever action .17 HMR. If someone makes an upper I like then I might go that route, but with an Alexander arms upper, it's over  $700 and I'd probably remove the handguard and the charging handle wasting money. They have handguard upgrades but it costs even more. Seems a bit steep if you ask me. It's rare in the AR platform, so very little is known about reliability, and replacement parts are equally specialized and rare. That being said, paying over $700 for uncertainty doesn't feel good. If it was around $450 to $550 maybe I'd buy one.

I'll keep looking for what I want
Thanks for the input
Hopefully someone on here has the key to our .17 HMR AR dreams.

I have had an Alexander Arms .17hmr  upper  installed on my ar-15 lower for for about a month now. I have run over 600 rounds threw it. One session was almost 200 rounds. It has been flawless. No miss feeds or FTF. I put the PSA polished trigger setup in the lower with the heaver buffer cartridge for a smother/ lighter trigger. Again not one problem. Yes it was expensive but unlike the Savage A17 i do not have to run expensive and  hard to find  ammo for it. I have no regrets but I will say I  plow threw ammo 3x as fast as i do with my .17HMR bolt action Savage. As they say "try it youl like it" LOL

Awesome, thanks for the info!  

They're not.  .17 HMR is based on the .22 WMR; case and rim diameter is larger than .22 LR.

Not to discourage you, but the idea behind .22LR uppers and conversion kits is cheaper practice ammo.   That advantage is lost with .17 HMR, which costs roughly the same amount as 5.56 ball at $0.30-$0.35/rd.  Unless you have a more specific reason for wanting .17 HMR, such as varminting at longer ranges than .22 LR is capable of without the report of 5.56, I don't see the purpose.

Someone here reported cramming a .22" WMR into a modified AR .22" LR conversion bolt, and using Marlin mags in a home rigged magwell adapter.  It apparently ran, albeit his bolt is probably very much on the light side.  .17" HMR has a very different pressure curve from .22" WMR, which is why Remington recalled their 597s & screwed their .17" HMR 597 owners - they were having gas blow the magazines out the bottom of the rifles, IIRC.

You could fab a gas operated locking bolt like Franklin Armory, w/ an offset firing pin, and that would work safely.  Or you could try to figure out how much weight Alexander Arms is using in their blowback system (they also specify minimum hammer spring levels) and see if you could duplicate that.

Yeah my reason for wanting .17hmr is for small critter hunting at longer distance than a .22, but also without said critter exploding as a result of being shot with my 5.56/.223 rifle. Sometimes I like having enough small critter left to consume.

In regard to the brass size, I did discover it's a different size from .22lr, but same as .22wrm.

At some point I might settle for one of those Alexander arms uppers, but I just think I'd like a barrel longer than 18", which is all I saw on their website. All of my .22 rifles are longer than 18". Maybe they researched and tested barrel lengths like crazy and anything longer than 18" doesn't offer any additional accuracy to that caliber round. That's my biggest reservation from buying one of those uppers.

I keep forgetting to click quote instead of reply. I might not be making sense with my reply. My bad.