I posted this data on Uzitalk a few days ago and figured I may as well post here also:

M16 – Dedicated Upper .22LR ROF Comparisons [all using same bolt/recoil & frame assembly, sear trip, and D.I.Y. Anti-Bounce Weight (~1.1 oz.) swapped between uppers]. Prior to ROF tests, each barrel had ten or more rounds fired to season the barrel. Ten rounds per run:

With 9 in. bbl. w. thread protector - CCI MiniMag: 1179, CCI AR-Tactical: 1197; Fed. 36 gr.: 1118; CCI SV: 1054;

With 4.5 in. bbl. w. Griffin Armament CAM-LOK QD attachment and an A1 FH - CCI MiniMag: 1075, CCI AR-Tactical: 1086; Fed. 36 gr.: 1069; CCI SV: 954; Armscor 36 gr.: 969; Rem T’Bolt 36 gr.: 1069

Disclaimer:  I have no affiliation with or financial interest in any vendor or manufacturer.  I am not a competitive shooter or a blogger who receives any form of compensation or sponsorship for endorsements, or favorable public or private comments.  I do not have a website, podcasts, webinars, or online videos; or books/magazine articles.  Use of vendor and/or product brand names, if any, is for informational purposes only; and products or services were purchased by me from regular commercial sources.

Best of luck.
MHO, YMMV, etc.  Be well.


ETA photos of the D.I.Y. ABW that was used for the testing:



Note the the test ~1.1 oz. ABW comprises one of the chrome-steel D.I.Y. ABWs previously discussed with a small section of steel pipe fastened on the rear of the underside.  ETA - Total cost of this ABW was more than $0.80 but under $1.

Also, the less than 1000 RPM ROFs that were achieved using the 4.5 in., unsuppressed bbl. and low velocity ammo was at the lower limit of reliable full auto operation as cycling and ejection were marginal.

ETA: ROFs for 4.5 in., unsuppressed bbl., w. CCI MiniMag ammo:
Ciener (~1 oz.): 1168;
CMMG (~3/4 oz.): 1213;
DIY #1 (~1 oz., ~4.5 mm recoil spring shroud lug engagement notch): 1189; w. CCI SV ammo: 1079;
DIY #2 (~1 oz. ~6 mm recoil spring shroud lug engagement notch): 1168; w. CCI SV ammo: 1071; and
DIY #10 (~1.3 oz.): 1129; w. CCI SV ammo: 1000.

Additional ETA to indicate the physical difference between DIY #1 and #2.

Updated with photos and description of the ABW that was used for the testing.

Any ROF data using a 16 inch upper.?


RCA

Only with a CMMG Atchisson MkII/III chamber adapter in a 16 in., 5.56x45 barrel.  My only dedicated AR .22LR barrels are the 4.5 in. and 9 in.  From what little ROF testing I've done with the chamber adapter/16 in. bbl. setup, the ROF numbers seem to be pretty close to or a little higher than the 4.5 in. bbl. dedicated upper.  I'd expect that level of performance is due to a chamber adapter having gas leakage/blowback unless one does something like put a wrap of teflon tape around the nose of the adapter to seal the interface, which I did not do in the testing.
Without a 16 in. dedicated .22LR bbl. to test, I can only speculate that the ROFs would be pretty close to the 9 in. bbl. dedicated upper numbers as, IIRC, most .22LR ammo velocity pretty much peaks out in the 9-10 in. bbl. range.
MHO, YMMV, etc.

Here are some for you that I tested:
....BTW...I honestly don't care much about the cyclic rate for 22LR.  I am more concerned with reliability in this caliber.  In all centerfire calibers I like my MG's to run in the 600s.
I just happen to have this data as I tested the Bore Buddy weight as shown in the bottom picture and I actually run that one the most as it is the most reliable setup.







Below is how I typically run this upper and it is very reliable.

Thanks for the info gentlemen. Seems like amphibian agrees that a heavier weight is key.

I may have to buy that borebuddy weight after all. My cmmg weight rarely gets through a mag as it is. Gonna try some more barrel lengths and whatnot. Hope to have it running on a 10.5 somewhat reliable

Thank you for sharing the results of your testing.  Very helpful for those of us who enjoy the .22 in F/A.

I fooled around with a .22 "slow-fire" conversion I "invented" (by ripping John Browning off) for a while.  With CCI standard velocity ammo it would cycle around 620-630 RPM.  It had bugs, but ran well if everything was in the right configuration.  I lost access to the machine shop I was using to modify parts so I lost interest and haven't done anything with it for a while.  It might have commercial potential, but it's a very small market.

Second Amend and Amphibian:

Thanks for this information.

I think I'll get the bore buddy weights and install them.
I have a 16' CMMG upper, CMMG bolt assembly w/ the CMMG weight and auto sear trip that I have done most of the reliability mods in the sticky on the rimfire page.
Runs really well if you don't load much more than 20 rounds in the magazine when doing a mag dump.
Same with 3 different types of magazines I use.
For FA, I use CCI AR Tactical or CCI Mini Mag 40gr round nose as they seem the most reliable of the .22lr ammunition I've tested for FA.
I suspect that ROF is so fast that it outruns the single position feed magazines' ability to present rounds fast enough during a mag dump.

Perhaps the heavier bolt weight will slow it down a bit.

I would appreciate any other easy tips to slow down FA .22lr rate of fire that anyone may have.


RCA

Both the M16 and AR-15 pistol I have are configured with standard mil spec fire control groups (FCGs) and the .22 units installed have standard recoil springs; and most shooting is done without a silencer.  I have tried heavier ABWs up to 1.3 oz. and encountered issues that have led me to suggest that no weight should be added for AR-15 semi auto applications and the full auto ABW weight range of ~1 to 1.2 oz. is optimal for use with a variety of .22LR ammo in the SV to higher power range in connection with AR-15s and M16s of the same or similar configuration.

In particular, excess weight slows the bolt cycling velocity to the extent that poor/incomplete ejection results in jams on the rearward stroke, and poor feeding and incomplete ejector rim latching on the forward stroke.  And in semi auto, "doubling" results as the combined added weight plus hammer, trigger, and disconnector spring forces prevent proper FCG cycling.

When adding additional recoil weight, others have apparently reduced or prevented such issues by such methods as implementing reduced power recoil springs, reduced power FCG (in particular hammer) springs, using aftermarket FCGs, shooting only high power ammo, and/or shooting with a silencer.  There may well be other things one can do that I am not aware of or am not remembering.

MHO, YMMV, etc.

ETA: If one wanted to keep a 16 in. or longer barrel for legal (or whatever) reasons, I suppose a 12 in. nonrestrictive extension could be pinned and welded to a 4.5 in. bbl. thereby maintaining the lower pressure generation and lower ROF of the 4.5 in. bbl. though I don't recall seeing reports of such a configuration.

Looking for your input on bolt weight for my F/A 22lr build. It doesn't appear that Bore Buddy sells the brass weight anymore. They have two adjustable weight kits now - standard and "light". They claim the light kit should be used with barrels shorter than 8".

My barrel length is 4.5 inches.

Per their recommendation, I would go with the light kit, but that kit only goes up to 1.2 ounces. That seems light based on the testing here so I'm looking for advice.

Don't really care about ROF, just reliability. My attempts thus far have been riddled with malfunctions (mostly hammer dropped on a live round in the chamber with no ignition).

I run the 16 inch barrel in case I want to fire the upper on one of my other lowers.

Here is my current setup.




RCA

Additional ROF data for other ABWs added to original post.
Good luck.

Thanks.

Which configuration did you find to be the most reliable?

I currently have the CMMG ABW and can't even come close to a full mag dump without multiple malfunctions. 3-4 rounds is about standard.

You are very welcome.

One reliability issue I've had was when I switched from using a chamber adapter and a 5.56x45 barrel upper to a dedicated 9 in. bbl. upper, using the CMMG ABW (the only ABW I had at the time) caused sporadic bolt bounce, i.e., 3-4 rounds (sometimes only 1) and then a light hit/fail to fire.  Ciener still had the classic Atchisson ~1 oz. ABWs (which have been used successfully since 1980 by thousands of shooters) available, so I bought one and the bolt bounce was cured.  When Ciener jacked the price way up, I decided to mimic the design (the patent had expired in the 1990's) and wound up making my own DIY 1 oz. ABWs for $1.60/pair.  And, as the newly posted ROF data indicates, the ~1 oz. chrome steel ABWs also perform as designed.

The other reliability issues that I have actually experienced is the "doubling" previously noted when an ABW over ~ 1.1 oz. is used in my (semi auto) AR pistol with the 4.5 in., unsuppressed barrel; and when an ABW over ~ 1.1 oz. (the heaviest I have tried is ~1.3 oz.) is used in my M16 regardless of barrel length, the ejection is very weak - dribbling out or not being fully ejected and causing a feed jam.  The heavier ABW (and slower bolt speed) might also have caused feeding issues with some magazines, but I don't definitive evidence.

I'll also note that a potential issue with using weaker FCG springs to improve .22LR operation (especially in connection with a heavier ABW) is such use might cause failure to fire and/or trigger slap when center fire ammo uppers are used in connection with the same lower.

Good luck.
MHO, YMMV, etc.

The CCI Mini Mags function great for me in both a DPMS Kitty Kat (7" on M16 lower with 22 Ciener Kit) and American 180.  I use the CCI Standards when shooting suppressed (both platforms).

So sounds like I should be shooting for something in the 1 ounce range then for my 4.5" barrel?

I use M&P15-22 mags - do those have any known issues?

I do have JP reduced power springs so I will consider your advice if I go centerfire.

With mil spec parts that are properly installed in properly dimensioned upper and lower receivers, I have always had reliable semi and full auto operation using good quality, high velocity ammo in 16 in. bbl. 5.56x45 chamber adapter, 4.5 in. dedicated bbl., and 9 in. dedicated bbl. configurations with 1 oz. ABWs from Ciener as well as those that are DIY.

No personal experience with M&P 15-22 mags.

Disclaimer:  I have no affiliation with or financial interest in any vendor or manufacturer.  I am not a competitive shooter or a blogger who receives any form of compensation or sponsorship for endorsements, or favorable public or private comments.  I do not have a website, podcasts, webinars, or online videos; or books/magazine articles.  Use of vendor and/or product brand names, if any, is for informational purposes only; and products or services were purchased by me from regular commercial sources.

Best of luck.
MHO, YMMV, etc.  Be well.

Just a note for anyone that is using cmmg style mags. Get the McFadden lightning loader! It's absolutely amazing for loading these mags and your hands stay clean.

Also, arms unlimited has their house brand mags for cheap. $8 or less if you buy more. I'm about to buy a heap of them so I don't have to reload as much at the range. But the McFadden loader really makes it quick and easy. All the reviews I've seen are pretty positive too, the only negative ones are people trying to load other style mags

Great write up,  thanks for taking the time and sharing.