Sunday, December 29, 2019

Piston vs Direct Impingement AR15 Testing

Piston vs Direct Impingement AR15 Testing

One of the things I have always wondered was how two identical AR15s would run with the only difference being that one is a direct impingement (DI) system and the other, a piston system. For those that are newer to AR15s, the vast majority of AR15s and military M16s run on a gas pressure bleed off port on top of the middle of the barrel which blows hot gas back through a small tube. That pressure blows the carrier back, unlocking and cycling the bolt, and carrier.



With gas piston systems, the process is similar however the gas bleed-off from the barrel pushes a piston and op-rod assemble located inside the gas block. The piston is pushed which moves the attached op rod which in turn pushes on a special bolt carrier and ultimately cycles the bolt. Most AR15 piston systems are either short or long-stroke systems. 

PWS’s is a long stroke system which is nearly identical to typical AK designs but is a proprietary system than cannot be retrofit to any AR15. The Short Stroke retrofit piston systems such as Superlative Arms, used in this test, can be retrofit to nearly any 5.56/.223 AR15. The long stroke piston systems have a stroke that extends the majority of the carrier stroke where the short stroke provide a quick short push to the carrier.

DIRECT IMPINGEMENT - The advantage of the DI system is that it is simple, lower cost, and does not require the precision setup for reliable operation that the piston systems does. The assembly precision is not as critical and the gas port alignment and fore-aft gas tube length can be off by a little and everything is still likely going to work just fine. The most significant disadvantage to the DI systems is they blow hot gas and burnt cartridge debris back into the action to power the cycling process which ultimately gums things up a bit and mandates cleaning ever 1500 or so rounds. With the addition of an adjustable gas block to allow tuning of the gas pressure, recoil can be greatly reduced (typically by about a third), less gas pressure, heat and debris is blown back into the action. In theory an adjustable gas block can deliver a \clearer and longer running DI gun. See my other article here on Adjustable Gas Blocks. With the use of suppressors though, gas pressures rise again and excessive gas is blown back into the shooter’s face if they are not re-tuning and lowering the gas block pressure for suppressor use.

PISTON - The main advantage is that piston systems do not blow hot gas or debris back into the action even with the addition of a suppressor. The cleaning interval can be greatly extended to 5000 or more rounds without a significant impact on reliability. Many shooters have noted 7000-10000 round cleaning intervals. My experience with previous builds and article has been that a piston driven gun seems to run so deceptively clean that I tend to forget completely about routine cleaning. Most piston systems also feature adjustable gas blocks which allow tuning of how much gas pressure the op rod piston sees. Piston systems overall have more mass in the system which means they soak up a bit more energy during each cycle. The result is a different recoil impulse… sometimes sharper and sometimes softer than DI systems. That extra mass can be problematic when working with lower pressure calibers such the 300 Blackout and especially with subsonic round. Some have figured out workarounds to increase gas pressure to drive the piston system to get 300 BO to work well in a piston gun. Suppressor shooters ideally want a 300 BO piston gun to have cleaner running gun that does not constantly blow hot gas back in their face. For this test I stuck with .223 builds.

THE PISTON VS DI QUESTION - The interesting question I had in mind was that if you had an optimized DI system with a properly adjusted gas block, how would that compare to a properly tuned piston system.  For this test, I built a custom mirror polished Barrett billet lower with a Hiperfire Elite Trigger and Ace UL rifle length stock and buffer. The uppers are both custom naked polished PWS Bootleg uppers with Faxon Match Series- 16" Pencil, .223 Wylde, Mid-Length, 416R, Nitride, 5R, Nickel Teflon Extension, and a .625-inch gas block size. These Match grade Faxon barrels are phenomenally accurate for their skinny super light profiles.



Both upper builds used PWS FSC compensators though I did test a number of different compensators with the system to see if there was some difference between certain comps and each system. For the record there was no magic combination of system vs compensator, each comp performed similarly on each respective upper.



The adjustable DI gas block was a Superlative Arms adjustable gas block and the retrofit Piston system for the piston upper was also Superlative Arms. The DI system featured a Faxon Lightweight Bolt Carrier to allow lower gas pressure setting and recoil reduction. The piston system features a Faxon Bolt with a Superlative Arms piston system (gas block, piston, and carrier).

In the scope of this test, the handguard, charging handle and optics really do not matter as long as the weight is not drastically different. In this case, I swapped between the Sig Romeo4T Red Dot, Holosun, and an Eotech XPS on each upper and saw no perceptible difference between the recoil impulse due to the optic weight swaps.



COST
There really is not a big difference in cost assuming you are buying quality DI components. A DI Adjustable gas block retails for around $100 and a quality Bolt Carrier Group is another $150. On the Superlative piston retrofit side of the equation, the complete kit minus bolt is $280. Add in $100 Bolt and the difference between the two systems is only around $130.

TESTING - CLEANLINESS
DI Left Piston System Right
I do have several other another Superlative Arms Piston uppers and one in particular has over 7000 rounds with an action that has never been cleaned and the bore has only had a foam Swab-It cleaner pulled through the bore. I knew what to expect on how clean the system runs.

DI System 
Both uppers were tested with 500 rounds each - 1000 rounds total. It was not a huge ammo load; however, the 500 rounds were more than enough to see the chamber crude build up difference between the two systems and get a feeling of each upper.  I used two sets of dry paper towels and wiped down the bolt and carriers, the inside of the action and the charging handles.

Piston System
The piston system’s chamber was basically spotless to the degree that it could be cleaned with a paper towel. The piston system was so clean that much of the material on the paper towel was just clean oil. The DI system on the other hand was as expected with a fair degree of carbon inside the receiver. It was cleaner than what a shooter would expect without an adjustable gas block. This DI system was adjusted to have about a third the pressure of a typical stock barrel, so it had about a third less crud in the action.  The DI upper is pictured on the left and the piston system on the right. You can clearly see the difference on the paper towels on who won this test - clearly the piston system.

WEIGHT
The piston system is heavier by not by much. The two handguards weighted in at the same weight. Technically the carbon fiber handguard was lighter than the hyperlight aluminum forend, however the Dolos quick barrel detach system added back some weight to the carbon fiber handguard. As tested without optics, the Piston system complete upper was 3-lb 12 oz and the DI complete upper 3-lb 1oz. The piston system is not that much heavier, the main weight difference is due to the DI system had an ultralight Faxon Bolt Carrier group. The realistic difference is the weight of the solid Op rod and marginally heavier gas block on the piston system. If the carriers were both the same weight, the difference would only be in the weight of bulkier piston gas block and op rod.

When it comes to weight, at the moment DI is the clear winner simply because a builder has the option to use a lightweight or ultra-light carrier with an adjustable gas block which can drop a huge amount of weight. If you are adjusting the gas pressure down and have a lighter carrier, you certainly do not need a heavier H2 or lardy H3 extra heavy buffer and can stick with a lighter standard carrier. All the way around the DI has the advantage to shed weight in a way that the piston systems do not.

TESTING - RECOIL & SHOOTING COMFORT
This was a rather interesting test because from an overall recoil impulse perspective, both felt very similar but the DI felt smoother and the piston system recoil... felt longer. The piston system always felt like something mechanical was happening all the way through the cycling process. I could literally feel the shot impulse, the op rod pushes back, the action cycling and the op rod and bolt resetting back into battery. The piston gun impulse feels like a process is going on vs just a recoil pop.

With that noted the recoil itself was similar between the two it just felt different. The DI system you identify the cycling process at 80% recoil and 20% carrier resetting into battery which overall felt lighter. The piston system was about 25% shot impulse, 25% op rod push back, 25% action cycling, and 25% the op rod and carrier final lock up. The piston system is different recoil feel that some will not like and some will. This was really a tie between the systems.

TESTING - ACCURACY
Strapping on a Burris 4.15-14 XTRII scope, the accuracy was so statistically similar, it is pointless to compare them. What I will note is that with plain old 40gr Fiocchi VMAX rounds I could consistently deliver ¾” 100-yard groups with either upper. These Faxon Match barrels, skinny or not, are super accurate.

TRICKS ONLY FOR THE DI GUNS
In addition to the un-natural weight reduction options, the caliber world is far more open to DI than the picky about pressure piston guns. Piston guns need the extra pressure to operate, but DI are much more flexible. Rounds like the 7.62x39 and 300 Blackout subsonic are still problematic for piston guns. Another trick the DI guns do is with the take-down kits like the Dolos system. The Dolos system allows the barrel to be removed from an upper still attached to a lower and as you can see with this kit stowed in small Hazard 4 Plan B sling pack, it delivers something exceptionally small and packable. Piston system are extremely sensitive to precise alignment and spacing of the op rod in relation to the bolt. A system like the Dolos cannot be used with piston guns due to the tolerances it requires for operation.

FINAL THOUGHTS
After 1000 total rounds, I wanted to shoot the piston system more than I did the DI system. The recoil was the same, but there was something about that mechanical almost steampunk feeling that made it fun to shoot. All along, I knew the piston upper would stay clean and keep shooting.  From a reliability perspective, both systems ran perfectly which might have changed as round counts increased.

Would I rather have a piston gun in the zombie apocalypse? Yes. The biggest problem I have with the short stroke piston retrofit kits is that they literally have to be set up perfectly, exactly, precisely or they do not run right. Once setup and locked down, they run perfectly and amazing and worth the effort. Once they are set up, they seem to deliver a gun that can run what seems like forever. If you have not tried a Superlative Piston retrofit piston build, it is a worthy build.

ABOUT SUPERLATIVE ARMS
There are a lot of different gas blocks on the market, however Superlative Arms versions are absolutely the only ones I recommend to people. Over the years I have actually weeded out all the other gas blocks I have and converted over to Superlative simply because of several reasons. They are the only adjustable gas block which has not failed, reliably holds the setting, and has a unique venting feature which vents the excess gas instead of restricting it. This ultimately delivers a DI adjustable gas block which stays clean and does not carbon over like other gas blocks.

Superlative Arms has also developed one of the easiest and most reliable retrofit piston kits available on the market. They provide good instructions and a very premium tier quality product that I personally have run well over 10K rounds through one of the conversions I did. If you are thinking about a Piston system, you might want to just convert your existing rifle or use this system for a new build.

Sunday, December 22, 2019

CAA Micro Roni V4 Testing - Proving the Value

CAA Micro Roni V4 Testing - Proving the Value
Answering everything you ever asked yourself about the Micro Roni


The CAA Micro Roni has been one of those products I've been wanting to test for some time. The question that crosses everyone’s mind is whether the Micro Roni is just a fun tacti-cool product or a realistic defensive option. During this last Black Friday, I finally relented on a deal from the Israeli retailer called YRS who sells the CAA Micro Roni products. YRS had an incredible deal for about $250 including the add on tactical light on the newest Micro Roni X Stab Gen 4 MIC-ROXG4ST for Glocks. To be clear YRS is not a product sponsor and they did not provide any discounts… in fact they have no idea I am even doing this review. About two weeks later, I had my Micro Roni shipment here in the US and a Glock 19 clicked in about five minutes later after reading the somewhat marginally vague instructions.

THE INTENT OF THE DESIGN
The intent of the Micro Roni Gen 4 is not to take the place of a rifle, short barreled rifle or even an AR pistol, it is first and foremost designed as a very compact handgun caliber PDW - Personal Defense Weapon. PDWs classically are chambered is handgun and small caliber soft armor piercing rifle rounds. 

The MP5 and Uzi formats both popularized and proved the value of a submachine gun size chambered in a 9mm handgun rounds with 2”-8” barrels. The intended ranges of these handgun caliber PDWs was 0-25 yards and this is where the Micro Roni fits from a realistic perspective. Yes, of course you can ring steel torsos at 100-yards all day until your heart's content, however typical 9mm rounds lose about half their energy at that distance and most consider 50-yards at the limit of realistic stopping power for most 9mm rounds.

FIT & FINISH
One of the reasons I hesitated so long on trying the Micro Roni was concern about the overall lockup between the Glock firearm in the Micro Roni. Glocks are good combat guns with good combat accuracy, but there is some engineered slop to assure when the gun is dipped in mil-spec mud it will not seize up and still shoot. 



Considering the polymer Micro Roni mounts to the polymer lower Glock rail and is secured via a rear polymer wedge/hasp, I was skeptical on the lockup points. Would polymer on polymer lockup and mounting be solid enough to deliver any real accuracy improvements or would it actually degrade accuracy due to all those potential movement points.

Though it only takes a tiny amount of wiggle to destroy accuracy, the lockup feels rock solid and I think it would take some high dollar measurement gear to discern the actual play between parts. My only real concern on fit was the top picatinny polymer rail which has some noticeable side-to side flex when pressure is applied to a riser mounted red dot or scope. Based on what I saw the flex “returns to zero”. The solution for me was to mount the optics on top of picatinny rail screw mount points which are solid.


CAA does offer an aluminum top rail option which could help improve accuracy a little, but I do not think it is needed based on my testing. If there is concern about that, a few dabs of Devcon 2-ton epoxy would lock that rail on so tight it would never move again. I would suggest going over all the seams and edges with an emery board (aka manicure file) to remove all the sharp casting edges to improve comfort.

PRODUCT IDENTITY PROBLEMS WITH THE MICRO RONI
There are a few problems with how many variants are out in the market of the CAA Micro Roni. There are CAA versions, plus MCK knock offs, plus international versions, plus dealer accessorized versions, plus old version with updates, plus different Sig/Glock/H&K variants plus concept photos which do not match the final production… it is all very confusing.


Add it that CAA does not even have the Gen 4 STAB listed on their site yet and also really does a poor job of helping you mentally sort that out - the result is that you can get frustrated pretty quick when shopping. YRS is one of the largest CAA official dealers and has the best prices and longest list of options. Yes, they are in Israel, but shipment was fast. What I would look for to match the reviewed Roni model here is the Micro Roni X Stab Gen 4 and specifically the “MIC-ROXG4ST” on the YRS site. 


Notably the white version was the only one on the site that had the right photo and the only one which did not show a concept photo of the Gen 4. The MIC-ROXG4ST is the only version that supports full size Gen 3, 4 & 5 Glocks including G17, G22, G31, G19, G19X, G23, and G32. I could not find anyone in the US that was stocking this newest version of the CAA MIC-ROXG4ST.

The add on tactical light is highly recommended and well worth the upgrade and is a very high quality and bright LED CR123 powered Olight tactical light - you will consider it a mistake if you do not buy it to start with.

FEATURES
This newest Micro Roni X Stab Gen 4 MIC-ROXG4ST version addressed many complaints of the original designs and offer shooters pretty much everything they've asked for in the Micro Roni over the years. The newest version has a longer folding brace which makes it more comfortable to shoot and overall much more usable. 



There is also a simple and unobtrusive trigger guard that covers the trigger on a loaded and cased gun which the earlier versions did not have. The ejection port has been enlarged to prevent jams and the charging carrier is now captured within the frame, so you do not have the opportunity to lose it. The slide release is now also exposed which drops the problematic slide release linkage of previous versions and reduces some cost.

The Micro Roni X Stab Gen 4 MIC-ROXG4ST has a new added feature that allows an integral lower rail to swap between an NFA legal angle forward grip or allegedly NFA legal angled magazine holder. This swap process requires two flathead screwdrivers to be simultaneously levered at the same time to release both the very stiff tabs for the swap - this a good thing because once clicked-in, it is literally impossible to move. 


The magazine holder is from my perspective an interesting feature, but logistically it is way faster to snag a belt mounted magazine on the reload. The mag holder is very secure and requires a push button release - that sounds cool, but in practice, it is slow. The other issue with the mag holder is that even a shorter G19 magazine mounts so far out of the holder that the Micro Roni loses a lot of it compact format which is its primary benefit. It sure looks cool, but I would stick with the forward angled grip and skip the magazine mount.

What is very unique about this newest version is that it will accommodate full size Gen 3, 4 & 5 Glocks including G17, G22, G31, G19, G19X, G23, and G32. Yep, one Micro Roni for 90% of the Glock models. This offers a single super versatile platform across a variety of guns. In my case, I tested with several Glock Gens and models including Gen 3, 4, & 5 G17, G19, and a Gen 5 G19X, however zeroing does change a little between the gun swaps so I would pick your favorite.

MOUNTING & USE OF THE MICRO RONI
Mounting up a Glock to the Micro Roni X Stab Gen 4 entails using the included hex wrench to adjust the blast shield/compensator to the appropriate model mark/length. I drilled a small hole in the rubber brace to hold the hex wrench for later use to assure I always have the needed tool with me. The chosen Glock model then snaps into the rear charging serrations, slides forward to then click into the rail lock. The final and third click is heard after closing the rear grip hasp and sliding it forward until it clicks. If everything has clicked in properly you should see green though a little side window at the rear grip hasp area.


The process is fast enough and with practice takes just a few seconds, however installation would not be something I would want to do under fire, but removal is pretty quick. The whole process is more of a pre-configured for shooting type setup in my mind. I can see where someone would have this Micro Roni X Stab Gen 4 in a daypack and wants to leave the pack in the car but avoid leaving a gun in a vehicle. 


The shooter could take a few seconds to remove their Glock from the Roni chassis to convert back to a CCW gun and that removal could all be done clandestinely within the confines of a pack. One annoyance is that the QD swivel is proprietary and is only available from YRS or CAA, why they would do this I have no idea.

Reloads are slower any way you slice it. For at least my hands, I need to do the tilt and shift movement which means that I need to rotate the brace from inside to the outside of my shoulder and then back again after the reload. A naked Glock is faster on the reload. From a reliability perspective we had zero issues testing through six types of brass and steel cased ammo of all various qualities. I would not hesitate at all in using the Micro Roni for self-defense applications where reliability would be critical.

ACCURACY TESTING SETUP

The big question everyone has is does the Micro Roni X Stab Gen 4 MIC-ROXG4ST make a Glock faster to shoot and/or more accurate. The short answer is yes, but with some caveats. To give the Micro Roni X Stab Gen 4 MIC-ROXG4ST the best fighting chance I tested for accuracy with Leupold 1.5-4 Hog Plex reticle scope - it was what I had in hand already in a QD mount for testing. Later I replaced the scope with a spare Vortex Sparc green dot because I thought the scope was overkill after seeing the accuracy results.

MAGICAL GLOCK ACCURACY ENHANCEMENT?
First I will note that the Micro Roni X Stab Gen 4 does not somehow magically enhance all the greatness of a Glock into a 100-yard precision sniper system upon insertion… it is still a Glock but with a shooting brace and a more precise single plane sighting system assuming you have a red dot or scope attached.

To set the expectation for accuracy, Ransom Rest fixtured groups will scientifically show the capabilities of handguns. From my experience, locking in a stock Glock into a Ransom Rest will deliver average groups in the 1” range at 25-yards which is a great group most really good shooters can deliver at 7-yards offhand. Glock’s official factory accuracy test is passing a 1-inch 25-yard group from a ransom rest type fixture. Yes, some Glocks shoot better than others and aftermarket triggers, barrels and upgrades can greatly change that accuracy. A few years back I shot a 10-shot 1.1” 20-yard group from a factory Glock and match ammo I was extremely proud of, but by contrast I can do that almost any day with my GP-100 revolvers. A few years ago, a friend and I would take turns ringing the 100, 200- and 300-yard gongs with our Glock 9mm and .40 S&W models. Shockingly, it was not that hard to hit with some regularity once you figured out the number of feet to hold over and get the sight zeros tweaked - possible but not precision. The Roni will provide more fun with these type of range antics.


If weight was not an option, which would you choose? A Micro Roni, MPX, or Galil

No amount of Roni magic will deliver better than 1” overall average groups at 20-yards or 12” at 200 yards. The only thing the Roni delivers is a braced format and single plane sighting system - both of which help improve your ability greatly to shoot your Glock accurately more quickly while reducing recoil to almost zero. The benefit is that someone with far less practice and experience can deliver more accurate hits faster with the Glock Roni combo than with a Glock alone - it is extremely easy to shoot. For the experienced shooter who can shoot to the limits of Glock’s accuracy, the immediate accurate benefits are there but much harder to see.

We did not see all these benefits at the 7-yard or even 10-yard range or even a big difference at the 25-yard range. Where we were finally able to see a big clear accuracy, difference was beyond 50-yards with most of our testing at the 75-yard line with Sig FMJ 124gr rounds and an unfired brand-new Gen 5 G19. The other shooter and I are both confident with shooting 10-out of 10 on steel torso targets at 50 yards with our preferred Glock, but the pace was faster with the Glocks mounted in the Micro Roni X Stab Gen 4 MIC-ROXG4ST chassis. At 75-yards, the pace differences and accuracy differences were significant with shot times well over twice as long with the bare Glock where the Roni system allowed solid shots quickly. A


t 75-yards we were seeing 8-12” groups with the Glock Micro Roni and 10”-20” groups with the bare Glock. Our best groups with the bare Glock were in the 8” range and we printed on very nice 4” group with the Micro Roni on a hostage target with Sig 147gr FMJ through the group moved high and right about 6 inches with that ammo. Ideally with Federal 147gr match rounds all these groups would have been tighter at this range, but the Sig 124gr and 147gr ammo worked for testing and proved the accuracy assumptions on the Micro Roni.

One thing people have noted is that the Roni dirties up the front and of your Glock pretty quick. I really had no issues with just wiping off all this powder residue with a Clorox wipe. yeah, they work really well for that. Dirty yes, affects function? No.


THERE ARE BETTER MORE ACCURATE TOOLS
Whether you are shooting a $2800 H&K MP5, $2000 SIG MPX, or a used Glock clicked into a Micro Roni, I didn't see any difference at all between these guns out to 25-yards. The Roni can help you shoot a Glock more accurately especially for less experienced shooters - but for longer pistol ranges there are better tools with more precision and higher velocities thanks to longer barrels or tighter lockup.

The Ruger PCC is an extremely reliable and accurate take-down rifle that accepts Glock mags. AR formats such as my 10-inch barreled PWS 9mm AR format PCC pistol fed by Glock mags can deliver consistently solid 1.25” groups a 100-yards, but that is a $1200 rig. Admittedly, I have several Sig MPX PDWs and they are about 2x more accurate at above 25-yards than the Glock Roni rig all thanks to a fixed barrel and more precise metal AR format - but is that worth $1500 extra premium on the MPX for 99% of buyers? I bet not. The popularity of MRO red dot optics on Glocks and other handguns also offer pretty substantial improvements in accuracy. A recent test of an IWI Massad 9mm with Burris FastFire III delivered incredible easy to shoot near single hole 7-yard groups so you might make the case if you can do that with just a pistol, why do you need the Micro Roni.

The problem with 9mm ammo at the longer 50 and 75-yards distances out of a short pistol barrel is that the point of impact and accuracy moves around a lot with various ammo - in our case, point of impact would shift as much as a foot and accuracy would jump from huge 24” groups down to 4” groups with ammo changes. Ultimately, I would say a scope is way overkill because at shorter distances you do not need it and at longer distances the accuracy and precision of the Glock Roni with varied ammo is more of a “shooting at the target” vs shooting with precision. A red dot is more than enough on this platform.

I think buyers have to look at the Micro Roni as simply an option to get into the PDW feel without a lot of investment, have some fun, and potentially shoot their Glock better. I would be cautious to artificially promote a bare Glock or a Roni equipped version to “as good as” status with the MPX and MP5’s of the world. Those gun on a different level… the Roni is just a convenient and far less expensive option. Where this setup does have a pretty big advantage is weight. Any of the above more accurate firearms are nearly twice the weight of the Roni plus Glock - if you are concerned about weight, the Micro Roni has a big advantage.

WHY BUY IT & WHAT IS IT GOOD FOR?
If we say that there is little difference in accuracy for the highly experienced Glock shooter under 25-yards between a naked Glock and a Micro Roni and that power and precision trails off so fast after that same distance, you start to ask why in the world should I buy one? There are several really good reasons.

The whole concept is cool fun and a blast to shoot. It is a fantastic gun to use for training new shooters. Everyone loves it and it is super easy to shoot. The one other person helping out on this test was my 80+ year old father who noted a huge difference in recoil. He also noted that something like the Micro Roni would be a really great home defense option for someone who did not have the upper body strength to properly control a handgun, maybe has some joint or muscle problems or where a rifle may be too heavy - excellent point. The brace afforded another point of contact and allowed a lot more stability. 


My father’s perspective was the Roni system delivers a ton of confidence around the handling and shooting of a handgun you may already own in a short format. If you already own a Glock, this is a simple and inexpensive add on that could keep you shooting a Glock format you like even if you do not have the strength to continue properly control a handgun. This is a great point for new and younger shooters… the Micro Roni makes it easy to shoot.


Size of Micro Roni vs MPX

Un-experienced shooters get to start seeing a huge jump in their Glock shooting precision which can be a big confidence booster when shooting from 7-25 yards. For example, my father has never been a great shot with a handgun, but with something like the Micro Roni, I would be confident that he could hit what he is aiming at with reasonable accuracy and in a defensive situation it would be my strong recommendation for him.

A PDW without the PDW cost. The other buyer for this is the single firearm owner on a budget who also wants to have a PDW format as well. Used Glocks and LEO trade-ins are super cheap these days to the point that anyone can afford to pick one up. The same cannot be said for the PDW market with most quality PDW firearms starting around $1000 all the way to the $2000+ Sig MPX and $2800 MP5 H&K formats. Even the CZ Scorpion starts around $900. Good lord, my mags alone for my MPX are $60. The Micro Roni X Stab Gen 4 is a cheap option to get into a PDW format for $300 + the Glock you already own. As a side point, if you are not enamored with the PDW concept in the Micro Roni, you are going to be ticked you spent $1800 to get basically the same functional concept. It is a fantastic starting place.

Of course, check your local laws first, but in most states and cities if you have a CCW license, the Micro Roni is just as legal transport as your pistol ...because it is still a pistol. The Micro Roni Gen 4 is legally just a holder for your Glock, so carrying it in a backpack while shopping is no less legal than carrying your Glock concealed and holstered through the same venue. It is a light-weight carry-it-anywhere option and depending on your backpack could be brought into play pretty quickly.

The final reasons for buying a Micro Roni is that it is just fun. Who would not want to take the great Glock format and have some fun with it beyond what it was designed for? We are all waiting for a factory Glock rifle that is unlikely will ever come. While Ruger, Keltec and the AR15 market finally delivered to us a Glock fed PDW and rifle, the CAA Micro Roni is a Glock powered option that is fun, reliable, and inexpensive. It may have its limits, but somehow none of us could stop shooting it.

FINAL THOUGHTS
Any concerns I had about reliability were addressed during the perfectly reliable performance during testing and would certainly have no concerns using the setup from a defense perspective. This is a fantastic home for a good used Glock 17 to just hang out in a Micro Roni. With the optional light, a used G17 with an extended +3 magazine extension, it is a fantastic light little setup, reliable, fun, inexpensive, and defensively practice.

SOURCES
https://www.yrsinc.com/product/micro-roni-stab-gen-4-caa-gearup-pdw-converter-for-generation-3-4-5-glock-17-22-31-19-23-32/