I've finally gotten my RDIAS and 5.56 Compressor upper out of jail (7 months).   The 5.56 and .300 BLK uppers run fine but the 5.56 upper charging handle dragged some, the action was stiff, and LRBHO wasn't happening until after a couple mags.

There is a lot of info here on 5.56 to 9mm conversion but I still have a couple questions.

1.  My setup includes a LWRC UCIW stock which comes with a UC2 buffer weighing 3.2 oz.  What I have read so far indicates the buffer it is too light for 9mm blowback upper use.  Correct?

2.  Heavybuffers.com has heavier buffers made for the UCIW.  They have a 5.5 oz. for 5.56 and one that is north of 8 oz for 9mm.   I am considering a Spikes Recluse 9mm upper (one stamp) with integrated suppressor.   Is the 5.5 oz heavy UCIW buffer sufficient for 9mm suppressed so I can use it for all 3 uppers?  Has anyone here used either heavy buffer with 9mm and/or 5.56 and how do they perform?  What will work un-suppressed in case I go for an upper with no can?

3.  Besides LRBHO, who likes what as far as 5.56/.300 BLK to 9mm drop in conversion blocks?  Manufacturer, top load vs. bottom load?  Simplest install/removal.  Here is a link to some info I found very helpful but would like suggestions from you folks before deciding.  Gunmann Mag Block Comparison

Thanks!
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Spoke with Clint at Heavybuffers..com and he said the 5.5 oz buffer may work for 9mm.   Spikes had installed a T3 (5.5 oz.) in my setup originally so I ordered a heavy buffer to replace the light 3.2 oz. one that came in the UCIW stock.

As far as the 9mm conversion it might be easier to figure this out one bite at a time:

Anyone using a 5.5 oz. buffer on your AR lower 9mm conversions?  If not what weight do you use?

I've found answers to most of my questions.  5.5 oz Heavybuffers.com buffer should work fine in the LWRC UCIW stock with 5.56, .300 BLK, or 9 mm uppers.

my SBR mag block is from Rudy at Macon Armory (above post)... I would suggest you limit the over travel on the bolt so that it just locks back to save wear and tear on the LRBHO... I use a hand built 5.3oz buffer and standard carbine spring with a NFA bumper... it works with my 7.5" and 10.5" barrels

I have 2, 16" carbines for USPSA PCC (Glock format)... one has an NFA bolt (slightly heavier) the other PSA, both have PSA uppers... primary uses A1 stock and Enidine hydraulic buffer and standard rifle spring... other is a carbine and uses the 5.3oz buffer and carbine spring

all work with reduced hand loads of a 142 power factor (135 Bayou at 1050fps) as well as factory 115 and 147

Thanks to Rudy at Macon Armory for answering all my questions on the phone today.  When I get my ducks in a row I will be back in touch and jump a bit farther down the rabbit hole.

9mm Blowback bolts don't have a set standard, but the ones from CMMG and QC10 I know supports the FA trip.  I don't know about the others.

Yeah, broken bolt stops seems to be correlated to the length of travel behind the stop.  On my 9mm SBR, I have maybe 1/16 inch and haven't had any issues, but I think if you can keep that gap to be 3/16 to 1/16, you should be good.  Once the bolt begins to reverse its travel, it can't build too much velocity with that small gap.  Since the energy in the bolt is proportional to the velocity squared, limiting that gap will also limit the velocity when it hits the stop.

I have Clint's heavy buffer (normal size extension) and with it set to 12oz., it will not cycle weaker ammo unsuppressed (Remington UMC for example).  But suppressed it will cycle anything.  So the answer to your ps is False.

Thanks for the info.  My ducks are lining up nicely.  Arfcom is a great resource.

btw.  If I can find a dedicated 9 mm lower with a shelf I can drop the RDIAS in that is an option I haven't considered yet but could be perfect solution.