Jp is expensive, but I wanted to build one nothing heldback gun and figured my 3 gun rig would be it.  this thing is a real bullet hose.  Too bad my skill level does the rig no justice.  Really this guns entire running gear is JP except for the gas block and gas tube.

JP 18" lightweight rifle barrel with JP bolt
SLR ultra lightweight 16.5" keymod handguard
PWS M-472 muzzle break with JP nut for clocking
Tarhill?? version of Hiperfire trigger
JP ULMOS (aluminum carrier)
JP Silent Captured Recoil Spring with spacer for rifle length buffer tube
SLR or Syrac Ordinance front adjustable gas block (really, they are both perfect so who cares which one it is)
Patriot Ordinance Roller Cam (dremeled the relief in the gas key myself)
Anderson upper and lower
Luth AR MBA rifle stock with cheek riser, but not the LOP adjuster
Gunshow Angled Vertical Forgrip at the very end the forend.
60 degree double sided safety lever.  I think Magpul
Extended charging handle latch.
Magpul MOE K2 (meant to get the plus, but was sleepy when placing the order.  I'm doing fine as is)
Aero Precision forward cant 30mm scope mount
Primary arms 1-6X scope.  I have a Vortex Strike Eagle, but cant tell much difference between the two.  I have yet to use the "goodies" on the PA reticle which is why I put it on this gun.

When I first set this rifle up it was overgassed.  I set the gas too high because the gun was still breaking in and I added an extra click to ensure reliability.  This DOES cause accuracy issues as the lightweight bolt assembly begins to move backwards before the bullet has left.  Argue with me if you want, I have seen the difference two clicks of the gas block makes both in sight movement and in bench accuracy.  Now this is an aluminum carrier with minimal buffer spring tension.  heavy steel carriers and heavy buffers / mil spec springs would probably entirely eliminate this phenomenon.  My entire first round of ammo testing was skewed by too much gas.

Over gassed was 9 clicks out.  The gun almost ran on 7 when first assembled.  I went to 8 and added a click for "reliability" to position 9.  I turns out position 7 was correct.  Broken in the gun will only spit out the empty hulls on 6, but runs like a top on 7.  Out of about 200 rounds in 3 gun and on the range I have only had one FTF.  Aluminum carriers require cleaning and EXTREME lubrication after ever shoot.  That is even in the instruction.  Lube the bolt carrier until OIL HITS YOU IN YOUR FACE, THEN ADD A FEW MORE DROPS.  Anyway, I left my oil at home and had not cleaned the carrier since the last match.  Had a single jam.  Ejected the empty, but did not grab the next round.  This was also on a full mag.  Pulled the charging handle and kept going.

Grouping - format is best 4 / all 5.  Bipod front, bag rear.  96 yds.  Never a windless day, but MS wind rarely gets over 5 mph.  PA 1-6x scope is great for go fast stuff, but it sucks for accuracy.  My targets are red and hard to see after the sun goes behind the trees.  A long range scope and black targets would do the barrel more justice.

Gunshow reloads from 2002 or 2003 - junk ammo that does no better than 2 MOA in anything.  This is my 3 gun load as it is very soft and I have been trying to use it up for years.  I bought 3000 rounds of it while in college.  LC brass with pulled / marked / out of round 55gr M193 bullets.  Yummmy.  Un known powder.
2.3" / 2.4" and this is typical.  This is worse than military ammo for accuracy.  May have also been overgassed.

American Eagle XM193AF90  
1.31" / 2.4"  overgassed

Hornady 55gr V-Max Varmint Express
1.05" / 1.23"  Overgassed
0.41" / 0.80" on position 7.

Hornady 53gr V-Max Superformance
2.01" / 2.05" Overgassed
0.64" / 0.96" on position 7

Federal Premium 69gr match GM223M ( best factory ammo you can buy)
0.51" / 0.71" on position 7

Winchester 69gr Matchking HPBT
0.54" / 1.42" overgassed
1.7" / 2.4" overgassed

Hornady Superformance 5.56 match 75gr BTHP (not for use in 223 chamber...oops)
3.7" / 4.0 overgassed
2.03 / 2.71" on position 7

Hornady Superformance 223 match 75gr BTHP
1.09" / 1.68" on position 7

Summary, this thing loves the light laser bullets.  Winchester match might do better now that I have turned the gas down.  This is definitely a sub MOA barrel even from a less than idea shooting position/scope set up.  You get what you pay for with the JP stuff, but to be honest.  I think a 3 moa gun would be just fine in 3 gun.  I had planned on critter hunting with this rig, but that was before I found the load my 6.8 likes.  So now I have a chainsaw-scalpel for a machete job.  Oh well.  It is the most perfect gun I ever built.  I just need to add some weight to it for longer shots and might swap the scope for a red dot.

EDIT 3-8-16
I dug out one of my old targets where I checked the POI shift of hot vs cold.  There was NONE that could be seen from the crappy gun show ammo groups.  Better ammo might show something, but we are definitely talking about less than 2 moa shift from COLD to HOT HOT HOT

5mph wind with Cheap Gunshow junk ammo from above.  5 shot groups listed as ....best 4 / all 5
cold barrel, slow fire - 1.67" / 3.0"
Then 20 round mag dump very fast (Hiperfire Trigger ).  Probably in about 8-10 seconds.
Mag change, get in position, then drop bolt just before firing first shot.  Each shot about 10-20 seconds apart depending on cheek weld and bag drift.  1.18" / 2.18".  This was after I put the gas block where it should have been.

I dropped the bolt at the last minute because I have learned letting a round soak in a scalding hot chamber heats the power and causes the shot to go out in space somewhere.

EDIT
Upper with no optic or mount is just over 4 lbs.
Lower complete is just under 3 lbs
Assembled rifle with YHM QD muzzle brake, no optic, no mount, no magazine is 6-3/4 lbs.

PA 1-6x scope with Aero Mount is 1.5# so scoped is 8-1/4 lbs.

I bought a Crono and decided to put my YHM ULT on just to see how fun it was.  

M4-72 muzzle brake is like a built in hair dryer, but keeps the gun in position even though the whole gun is too light.  I may make some bolt on weights for the handguard and buttstock.

Removed the muzzle brake and WOW. this thing kicks almost as much as my Mil-Spec type rifles I have had in the past.  It still less and more controllable, but THE MUZZLE BRAKE MAKES THE GUN FOR 3 GUN DOUBLE TAPS.  I now see that.  And I put soooo much time into trying to find the best bolt carrier, buffer spring combination when 75% of your sight movement is removed by the muzzle brake, not the guns internals.

Then installed the YHM DQ muzzle brake.  It only works a little less than HALF as good as the M4-72.  Id say it works about like the gunshow / Amazon COPY of a Jerry Miculek (but a real JM is as good as anything out there).

Then I put the silencer on.  POI shifted down 6", left 1". This was easy to dial into the scope.  Turned the gas down 2 clicks.  I also found that only XM193 runs 2 clicks below normal.  Everything else only needed 1 click below normal.   With the can on, the gun moves less than it did with just the YHM QD muzzle brake, but still only about 75% as stable as the gun with the M4-72 installed.  Now the extra weight on the end actually felt great.  The gun got a lot easier to aim, but even the extra weight of a silencer does not hold the gun as flat as a good muzzle brake for double taps.

Summary, for close range bullet hose you want the most aggressive compensator you can get, but  a silencer will not slow you down enough to make it any less fun.  I enjoyed shooting 3gun with a can.  I never saw any heat mirage, and did not bang it into any barriers.  My overall score still sucked, but that was mostly due to shotgun/user/ammo issues, no shoot penalties,  and A HORRIBLY designed 100/250 yd rifle stage with 4" diameter gongs at 100 for standing and kneeling.

I may try my 12.5 SBR out under the clock with the ULT attached.  It has similar internals, similar weight,  and the same trigger as my JP 18" rig, but no matter what the shorter gas system makes the gun move a little more
on double taps.  The JP 18" rifle with the same can moves a little less than the 12.5 MIDLENGTH SBR with near identical moving parts.

Under 30 yards, I would say none of this matters, from 12.5 MID with the can up to the 18" RIFLE with a comp, I think I could still keep doubles on paper with any competition rig.  

From 40 yards, I would say the Rifle has the edge even with the can.  With the compensator, I can double tap over 50 yards with my rifle if I have the muzzle calm before pulling the trigger.

JP 18" rifle from above.  Very windy 5-15mph from all directions.  Most groups were wider than they were tall.
NO CAN
AE XM193 ..... 0.89" / 1.60"
3275 ..... 3295 ..... 3281 ..... 3278 .... 3227.   Faster than mil spec 20"

Gunshow crap reloads ..... 3.0" / 3.3"
3258 ..... 3024 ..... 2961 ..... 2979 ..... 2949 - 300 FPS SPREAD...OUCH........JUNK...  3258 was noticeably louder

WITH THE CAN

AE XM193 ..... 1.55" / 1.94" (rapid fire, bad mirage from already hot silencer)  ..... 1.38" / 1.72" (pulled 2 shots) ..... 0.68" / 0.87" AMAZING FOR MIL SPEC AMMO
3263 ..... 3300 .... 3286 ..... 3275 ..... 3227  ...... 3281 ...... 3218 ...... 3168 ....... 3241 .... 3217..... 3xxxx ...... 3261 ...... 3270 ..... 3241 ..... 3266

Now there is a STRONG possibility I recorded something wrong and the .68 / .87 group and velocity was really Hornady 53gr SF.  I cut that group out for a keeper.  It is hard to believe M193 could do that, but I wrote it and its velocities down on the  AEXM193 box.

Gunshow reloads .....1.68" / 3.4" .... four shot group only
3029 ..... 3130 ..... 3104

Hornady 53gr Superformance ..... 0.80" / 1.12 ...... 0.42" / .72" .....BEAUTIFUL-  too bad I laid some 308's over this group.   4 were touching.
3278 ...... 3297 ..... 3272 ...... 3262 ...... 3285 ..... 3249 ..... 3273 ..... 3252 ..... 3275 .... slower than I thought, but this is still a wonder bullet with a .29 BC, like 69gr SMK but 200 fps faster.

I had other ammo on hand, but I did not try it cause I already know this thing likes 55 and 53gr Vmax.  I saved the other stuff for my 12.5 SBR.

Twist rate?

I have an aging nearly 20 year old JP Enterprises grade 1 24 inch 1:9 bull upper.    It loves stuff lighter than 55 grains.   Some of the best grouping stuff I had was 40grn Vmax.

I will never touch Federal Gold Medal ever again after the years where Federal had thin case heads or whatever it was that caused the primer pockets to open up and shit their primers into my action.   Federal Gold Medal and American Eagle both did it to me.   Shame too because American Eagle 50grn HP, the cheap shit, was some of the most accurate factory ammo I ever shot in my rifle.

Early on in the rifle's life I had several factory loads that were solid MOA performers.   For handloads I liked H322 or a similar rate Accurate powder.   Metered well from the measure and made for easy varmint blasting loads.    Had a load that averaged around 3/4moa for 10 shots.   Now the gun is starting to shoot looser and it is handloads I need for keeping MOA or slightly better.   But not bad for nearly 20 year old rifle with god knows how many rounds through it.

1:8

What brand lubricant was used for the aluminum carrier?

What ever you want as long as its gun oil.  This is a race gun, so I would not use motor oil or anything thick or gummy.  The parts are lighter than normal and moving faster than normal.  Thick oil might add drag.  Just keep it swimming in thin gun oil or equivalent and drown it before every match.

I use FP10.  Its old school and never caught on.  Rem oil or any name brand stuff is fine.

The jam I blamed on not lubing could just as easily have been caused by the junk ammo.