Posted: 4/18/2017 12:45:19 AM EDT
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Can anyone comment on the compatibility of an LT PredatOBR barrel with an Aero Precision M5 upper receiver and rail? I'm thinking it's a proprietary size or something and won't work but curious to see if anyone's tried it. The 762 platform is pretty obscure across the various manufacturers.
LT PredatOBR 762 Barrel Aero M5 Stripped Upper Aero M5 Keymod Rail Also, I do see the barrel's description says the following: "NOTE: PredatOBR® Barrels only work with the PredatOBR rifle and require a PredatOBR® Barrel Wrench. Turn your single rifle into a rifle system." |
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Can anyone comment on the compatibility of an LT PredatOBR barrel with an Aero Precision M5 upper receiver and rail? I'm thinking it's a proprietary size or something and won't work but curious to see if anyone's tried it. The 762 platform is pretty obscure across the various manufacturers. LT PredatOBR 762 Barrel Aero M5 Stripped Upper Aero M5 Keymod Rail Also, I do see the barrel's description says the following: "NOTE: PredatOBR® Barrels only work with the PredatOBR rifle and require a PredatOBR® Barrel Wrench. Turn your single rifle into a rifle system." I've not tested the combo, but the barrel extension most likely will not fit the upper. Whereas the AR-15s comply to a standard, the AR-10 designs do not and LaRue uses an extension fitting only their rifles. |
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I've not tested the combo, but the barrel extension most likely will not fit the upper. Whereas the AR-15s comply to a standard, the AR-10 designs do not and LaRue uses an extension fitting only their rifles. |
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This will fit together fine. I have this combo put together using a LaRue Field Grade PTOBR barrel and a Lantac E-BCG, on a Fulton Armory lower with an MBT trigger group in it, just haven't test fired it yet. I hope to do it once I get back to California from Missouri later this week.
You will need to change the barrel nut to a DPMS pattern nut if your barrel has the PTOBR barrel nut on it. Cycling by hand , all works well. Keep in mind that most hanguard manufacturers use a proprietary bbl nut on their .308 stuff so don't be in a rush to buy a new nut. Decide whose hanguard you want first. Just order the part for a DPMS build. |
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This will fit together fine. I have this combo put together using a LaRue Field Grade PTOBR barrel and a Lantac E-BCG, on a Fulton Armory lower with an MBT trigger group in it, just haven't test fired it yet. I hope to do it once I get back to California from Missouri later this week. You will need to change the barrel nut to a DPMS pattern nut if your barrel has the PTOBR barrel nut on it. Cycling by hand , all works well. Keep in mind that most hanguard manufacturers use a proprietary bbl nut on their .308 stuff so don't be in a rush to buy a new nut. Decide whose hanguard you want first. Just order the part for a DPMS build. |
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Sorry for the delay. I have been on a tight schedule, now in New Mexico, tomorrow California..... Used an Aero M5 upper, should have put that in originally. Wanted the Aero lower too, just weren't available in the time frame I needed it. |
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Not familiar with the Mega-Matten uppers/lowers. You will have to research whether they are Armalite (AR-10) or DPMS Pattern (LR-308).....
I will try to post a picture of the weapon later today. I still haven't unloaded the tools/gear from the back of my 4x4, much less have it put away......... Gotta do that first, well, that and buy another MBT while the sale is still on. As far as the optics and MBUIS, I just used leftover stuff. It will have different optics/sights down the road. |
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Gotcha thanks. The Mega will take pretty much anything, I'd just have to match the barrel extension to the correct bolt. I suppose a call to the mothership may be in order to remove any doubt. 
The below picture is after the Tranquillo adapter and handguard were installed. The scope is a Leupold VX3, 2x8-40 with a Boone & Crocket reticle. Very disappointed in this scope after using the Mark IV version of this scope on the TOBR originally. The Mark IV now resides on my current 6.8 SPC build where it performs wonderfully. Way too good to pull it off and put it on this rifle. This will be my hiking weapon in bear country. Thinking about going with an Aimpoint M4s with the 6X magnifier..... PS: Magpul plastic BUIS are barf!!!! 
Please keep in mind that these are Californication models.... The OD green pistol grip on the left of the first picture is on my only registered Assault weapon.... The others are all now featureless rifles. (Which includes several not in these pictures) |
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^ Interesting. Let's us know when you shoot it. I might do the same thing in the future. Which bolt are you using btw? I must of miss it 
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I am using a complete Lantac E- BCG (Enhanced Bolt Carrier Group)...... It is designed to work better on suppressed weapons. Not that I have any supressors....... |
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The barrel extension issue was on an AR-15, not an AR-10...... Pretty much everything on that one was an issue!!! The only thing you need to watch out for with a barrel extension is whether it is the correct extension for the upper. As in M4 ramps versus A-3..... Again, an AR-15 issue, not an AR-10 issue. There used to be a show and tell on LaRue.com and on this site as well that will show you what I mean. Might want to do a search for that.
I have found that most quality barrels, if they come with the barrel extension installed, will head space fine. It would be really nice to have a set of go/no go gauges though. I am building up my supply of Armorer's tools slowly but surely!!!!! In the meantime, cycle it with dummy rounds. Shake it with dummy rounds chambered to see if anything is loose. Maybe fire an unloaded case that has been reprimered....... Looks like I am going to be working this weekend (all overtime) so I may not get to shoot anything. I need to sight in almost all my. AR-15's and both AR-10's due to optics being moved during the conversion to 'Featureless' for them...... Went through a couple of iterations before settling on what I have now. Need to finish sighting in the red dot on the AK too..... |
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The photos pertain to AR-15s because you don't have those options on 308 barreled weapons, thus no problems with barrel extensions. Buy the LaRue, you will be happy with it. My field grade barrel shot .750 when it was in the TOBR using the aforementioned low power Leupold Mark IV.
Just realized the first picture above does show the brown AR-15 I had all the problems with.... All is well with it now, pending a trip to the range...... It really never shot all that accurately before. Maybe now that the barrel is tight in the extension it will be a bit more accurate. Otherwise I may need to buy a Stealth barrel for it..... |
| For those of you interested in Larue 7.62 barrel compatibility, take a look at my response to this post: http://www.ar15.com/forums/t_2_219/282998_7-62-PredatOBR-barrels.html |
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Link doesn't work.
After shooting it at the range, the only issue is too many rubber 'O' rings on the extractor spring...... Should work fine next time out..... I will try to post better pictures of the bolt and internals/externals of the rifle after it gets cleaned. |
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Link doesn't work. After shooting it at the range, the only issue is too many rubber 'O' rings on the extractor spring...... Should work fine next time out..... I will try to post better pictures of the bolt and internals/externals of the rifle after it gets cleaned. |
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For those of you interested in Larue 7.62 barrel compatibility, take a look at my response to this post: http://www.ar15.com/forums/t_2_219/282998_7-62-PredatOBR-barrels.html |
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I've been following that thread as well and it sounds like I'll be good to go with an LT bolt in an Aero Precision carrier. Waiting to purchase until I can make sure it'll all work together but I'm sure this bolt will work just fine with this carrier. |
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My buddy and I went through this whole predicament and figured it out after a lot of trial and error. The lug length on the Larue barrel extension and the bolt is shorter than the standard DPMS patern. The longer lugs on a DPMS bolt won't lock into the Larue barrel extension. So, the solution is to buy a bolt from Larue and put it in your DPMS bolt carrier. This has been tested with both Aries and Lantac carriers. Let me know if you have any questions. The only two problems with this solution are the cost of a Larue bolt and the wait time. The following rifle was assembled using a LaRue 16.1" FG, AERO M5 and AERO BCG. The bolt would close sometimes, but not always. Replaced barrel with a MEGA 16" and it works fine. The FG LT bbl now stays with the .260 tOBR 
Get the LT bolt for sure |
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Finally got a chance to measure the lugs on both bolts.
LaRue: .307 Lantac: .314 I still want to try it at the range now that I have the extra 'O' ring removed. Just cycling rounds using the charging handle seems to work ok..... But I want to field test it. That is probably going to have to wait for next weekend. I'm just plain tired and think I will sleep in until at least seven tomorrow!!!!! (That's 2.5 hours past normal) Soonerman: Did you by chance pull the bolt out of the carrier and see if it would engage fully in the barrel when it was out of the upper?????? Also, did you remove any of the two 'O' rings in the Lantac ejector before or after trying it???? Oops! That was the MuffinMan! Doesn't he live on Drury Lane????? 
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| We never tinkered with the Lantac bolt because the Larue bolt was working perfectly. There was, however, an Aries bolt that was modified to work (shortened the lugs), but we were skeptical that we'd get the accuracy we wanted due to the imperfect nature of the lug shortening procedure. |
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You would need to use a dial caliper set up for measuring the depth of the bolt face to the outermost edge of the lugs on both units to see where the extra length came from. In front of the bolt face, behind the bolt face, or a little of both......
I never thought about it or I would have checked to see if the lugs fully engaged before installing the barrel in the upper.... If I had a pair of needle nose pliers that were long enough, I would give that a try anyway..... |
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You would need to use a dial caliper set up for measuring the depth of the bolt face to the outermost edge of the lugs on both units to see where the extra length came from. In front of the bolt face, behind the bolt face, or a little of both...... I never thought about it or I would have checked to see if the lugs fully engaged before installing the barrel in the upper.... If I had a pair of needle nose pliers that were long enough, I would give that a try anyway..... |
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Easy enough to fix if you have a lathe (and a friend good enough on it to do it!). I haven't used a metal lathe since my machine shop class in the early 70's in high school......
Thanks for the good info!!! If I decide to shorten the lugs I will ship it off to a reputable gunsmith somewhere that the research I will do leads me to believe it will be done correctly...... Probably be cheaper than buying the LaRue bolt...... |
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FWIW - A measurement of the LaRue lugs and a JP HP bolt. I checked both bolts in my LaRue .260 using the LaRue BCG against PTG go and no-go gauges, in each instance. Bothe bolts closed on the go and did not close on the no-go. I did not measure the bolt face depth, depth to back of lugs, etc., etc.
The LaRue averaged 0.3070 
The JP HP averaged 0.3105 
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Took the FG 7.62 (and a few others ) out to the range this morning. The 7.62 will chamber a round, but it doesn't let go of the round. It hangs half way out of the port, still in the grip of the ejector. The range I go to is not conducive to taking apart an extractor, especially if there is a little wind blowing... Way too easy to lose small parts in the dirt and dust. But I will take the other 'O" ring out of this extractor before I give up on it. However, that was the least of my problems.
The Brown AR-15 pictured in a comment above was a single shot, short stroking. The CCMG upper on it has always had functioning problems since I bought it brand new. Hey, you get what you pay for. It started off as a gas piston unit, talk about unreliability!!!!! I converted it to DGI and it works ok with 62gr. 5.56, but not 55 gr. .223.... Think I'm going to buy a .070 drill bit and open up the gas port. Even if it means I have to buy an adjustable gas port!!!!! I need it to be reliable with whatever I feed it!!!! .070 is what the port size is on my 6.8SPC (LaRue Black Gold triggers in both AR-15's, MBT in the 7.62) and the adjustable gas port let me dial it in great! Remington 115gr. match empties land at 5 o'clock, and the lower pressure Remington 115gr. ball lands at 4 to 4:30.... I sure wish Mark made an MBT for the AK!!!! I have a custom trigger in the AK that is waaaay better than the factory job, but it would never even remotely be confused with an custom AR Trigger!!!!! |
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Ok, Pulled the last rubber 'O' ring off the extractor for the Lantac BCG on the 7.62 with the LaRue FG barrel. If it doesn't work this time, I will have to buy the LaRue "Deluxe Parts Kit" for it.....
On the Brown AR-15 (CMMG = Certified Maximum Money Grabber) I checked the diameter of the gas port in the barrel. The smallest bit I had was 1/16" (.0625) which is the minimum size for a gas port in a 16 inch, carbine ported barrel... At least from my research. The 1/16" bit was much larger than my gas port which was maybe .590 in diameter, and that may be a generous guess. Anyway, drilled out the port to .0625... Will try both guns out next Friday. Still waiting for Mark to make an FDE stealth upper. 
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AR-15 Platform 5.56mm
Barrel Port Caliber Port dia. 20" rifle 5.560 .0935 20" rifle 5.560 .096 20" rifle 5.560 .098 16" mid 5.560 .078 16" mid 5.560 .081 16" car 5.560 .0625 16" car 5.560 .065 16" car 5.560 .070 14.5" car 5.560 .067 14.5" car 5.560 .086 11.5" car 5.560 .081 11.5" car 5.560 .089 24" rifle 5.560 .089 AR-15 Platform 300 BLK Conversion Subsonic Ammo Barrel Port Caliber Config. Port dia. 16" car 300 BLK UNSUP 0.125 16" car 300 BLK SUP 0.106 16" car 300 BLK SUP 0.11 16" pistol 300 BLK UNSUP 0.067 16" pistol 300 BLK SUP 0.086 9.5" pistol 300 BLK UNSUP 0.093 9.5" pistol 300 BLK SUP 0.093 8.1" pistol 300 BLK UNSUP 0.104 8.1" pistol 300 BLK UNSUP 0.12 8.1" pistol 300 BLK SUP 0.086 8.1" pistol 300 BLK SUP 0.093 AR-15 Platform 300 BLK Conversion Supersonic Ammo Barrel Port Caliber Config. Port dia. 16" pistol 300 BLK SUP 0.059 16" car 300 BLK UNSUP 0.099 16" car 300 BLK SUP 0.093 9.5" pistol 300 BLK UNSUP 0.073 9.5" pistol 300 BLK SUP 0.067 8.1" pistol 300 BLK UNSUP 0.076 8.1" pistol 300 BLK SUP 0.067 |
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Finally pulled the trigger on a LaRue Ultimate Parts Kit, which has the complete 7.62 bolt along with other nice to have parts. That should take care of the 7.62 issues. I will find out Friday morning if I have fixed the 5.56 issues.
5.56: I broke out the LaRuler and measured the distance from the shoulder to the gas port hole on the barrel. Then I measured the thickness of the handguard retainer ringy-thingy. Then I measured the distance from the edge of the gas port to the actual hole in the gas port...... Hmmmmmmm, something not right here. I guess when I tightened the barrel into the extension, it moved things just enough that the gas port "on" the barrel wasn't getting enough gas from the gas port "in" the barrel. I step drilled the gas port hole so that it will cover the hole in the barrel. |