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Posted: 9/5/2012 6:30:42 PM EDT
| I am building my first 9mm AR platform rifle. My first question is do I need a DI set up to run it reliably? My second question is what conversion block is good quality? I have been reading about a few and their are bottom feeding blocks and top feeding blocks, which is the most reliable to run? My last and final question is what conversion block is the easiest to use considering ease of magazine use? Thanks. |
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Quoted:
I am building my first 9mm AR platform rifle. Ok My first question is do I need a DI set up to run it reliably? No, many a COLT SMG been used for LE related purposes for years.. it plain old blow back. Reliability will come from how you fit all your parts so they function in harmony My second question is what conversion block is good quality? I have been reading about a few and their are bottom feeding blocks and top feeding blocks, which is the most reliable to run? They all serve same purpose, that is to hold magazine in position, hold ejector and ramp,, bottom feeder need typically some form of up/down adjust in magwell to find right height, top loader typically set right in place on lower' shelf.. you have to decide what fits your needs/desires for use of lower in long run.. I use the Hy-Tech block,, plain old Uzi mags, takes me all of 30 second or less to go from 556 to 9mm either direction. |
| You should ask is this going to be a dedicated 9mm build or one that you plan to swap back and forth between calibers. If it's a dedicated one, I'd opt for a dedicated magwell lower. Saves you the hassle of going and tinkering with the block to get it to run. The majority of 9mm issues on this board can be traced to either magazines or the mag block itself. |
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You can go either blow back or DI for the upper. But the DI is more expensive and my block back has been very reliable for me. So I don't think I would spend the extra to go DI. I will say the blow back has a sharper recoil impulse than my 5.56 AR, so take that into consideration. It isn't bad by any means, but I can feel the difference. So if you don't mind the extra money, a DI might not be bad to play with.
As mentioned above, decide if you want a dedicated rig or if you want a multi-use lower. That will help with advice on the mag well. If you go dedicated, get the dedicated Hahn mag block or a DD lower. If you want a dedicated rig and run a 9mm Glock, take a look at the DD Glock mag lower. I did a SBR AR lower that I wanted to switch out quickly at the range for every caliber I shoot in an AR platform. I have a few SBR uppers in different calibers, so I also went with a VM Hy-Tech Uzi block as it is quick to use and remove. It has been 100% for me, but it does look a tad goofy. It inserts and drops out as quickly as a 5.56 mag. Uzi mags are cheap and you can get everything from a 20rd to 32rd mags. In fact, the Colt pattern mags were based on the UZI mags. They are very durable and easy to load as they are a double feed mag. My M-11/9 single feed mags were a pain in the butt to load, so the UZI mags are a nice change. As for the upper, I have a RRA barrel that has been cut back to 5.5" on a RRA 9mm flat top upper. I have a ramped bolt, 9mm heavy buffer and a YHM lightweight carbine rail. It is blow back and it works well with my SWR Trident 9 suppressor. It is short and quit, especially with 9mm subsonic ammo. It is one of my favorite guns. |
| Thanks for the response. The lower will be a dedicated lower. What are some common problems with 9mm AR platform rifles? What do I need to watch out for? I am not new to AR's but I have never build a 9mm platform, just need some knowledge about the subject. Thanks. |
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People seem to have mixed results with 9mm AR's. Of course, the only ones you usually hear about are the ones with issues. I have two 9mm AR rifles and both are stone reliable day-in, day-out. One has a dedicated CMMG lower with their bolt (ramped from the factory). The other rifle is a Cav Arms lower with a RRA magwell in it. It was my first build and after the second trip to the range it was all "tuned" and ready to go. It only needed me to make minor adjustments to the magwell.
People will have favorites. Some will have horror stories. I am either lucky or just studied others posts here and learned about the quirks of the 9mm If you are looking for the best value in a 9mm rifle the CMMG seems to offer the most for the money. If you don't mind spending a bit more the Colt 9mm is held in high regard by its owners. After that you have many offerings at a wide range of prices. Some must have Glock magazines but for me it wasn't important. YMMV. You will hear some heated debates about what magazines will actually work in the 9mm AR. There have been mixed results for some. Other of us have found many different magazines that function well. Both my rifles run on an assortment of ProMags, CProduct, and modified Uzi's all equally well. But then, I might be Mr. Lucky on that....or I figured out how to adjust the block to make it work right. Or both? Anyway, the 9mm AR is a lot of fun, enjoy! |
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i was apprehensive about my first build. I thought i would try to knock out as many variables as i could when it came to quality and reliability. Lots of research on the forums lead me to install a dedicated hahn block and invest in metalform magazines in hopes of lowering the amount of tinkering needed for the build. After that it seems like finding the right combinations of ammo and buffer/spring setups is the last thing to do.
My first range trip resulted in some misfeeds, but after about 20-30 rounds it was all uphill from there. Very pleased. ETA: That first range trip i used a T1 buffer (very light) from spikes + quarters and an extra power wolf buffer spring. It ran but felt rough. Just bought a spikes ST-9x buffer and im gonna see how that works. |
| My 9mm build started out with a RRA 9mm 16" upper with a ramped bolt on a standard lower with a Hahn non-dedicated top loader and metalform mags. At the time i was sharing one lower with multiple uppers and wanted a quick change setup that was reliable. I'd seen numerous posts of people with this setup that had no issues, and since round 1 I have not had any failures. I mainly shoot light target reloads but I've tried a half dozen different brands of ammo, they all work fine. Later I purchased another standard lower to dedicate to this build so I added the Colt long finger catch to give me last round hold open (the non-dedicated hahn top loaders don't have LRHO, dedicated hahns do) and upgraded my RRA 9mm buffer to a Spike's dedicated 9mm buffer (ST-9X) just to smooth it out a little. If you don't go with a dedicated lower than Hahn, Spike's & RRA all make top quality magwell blocks. |
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