How Much Barrel (weight) Can AR15 Receiver Handle?

D

Denver_AR

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Minuteman
Jan 3, 2020
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3
#1
Looking into building a long range AR and considering heavy barrels such as Criterion 24" bull barrel.
This seems like lot of barrel for an aluminum receiver. Overlooking balance and aesthetics, could the weight and sag on the receiver impact accuracy.
Any experience with this? Could it handle a can?
 
#5
I dont think its an issue in the sense that it affects accuracy, but I do believe that a longer heavier barrel may contribute to a bigger shift in POI from bipod vs shooting off a bag.

I have built 2 small fram guns with 24in bull barrels and .936 gas blocks. One a 6 arc, the other a 223 wylde. Both guns would shoot .2mil groups consistently at the bench and both of them have almost .5mil difference in POI between shooting from bipod and bag. My large frame gassers are .1mil maybe .2 difference between bipod and bag with heavy bull barrels.
 
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#6
For a barrel that heavy I would regardless of what's been done in the past use a heavy upper, Vltor MUR is a good option and the Seekins SP223 if want to run a specific handguard. JP makes some nice heavy walled uppers and so did Mega, not sure if they still make them. My personal favorite is the Seekins precision IRMT-3 UPPER. I'd also recommend you have your smith use a WOA Competition Barrel Extension.

WOA Extension Info

Shop White Oak Armament Online Store
www.whiteoakarmament.com www.whiteoakarmament.com
 
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#9
bigjake83 said:
A lot of use did, They were a fantastic LR upper for around $500 but that doesn't mean they didn't suffer from receiver flex.
Click to expand...
Mine is going on 10+ years old and will still hold just under MOA with LC 5.56 brass and 77 grain TMKs. I thought the barrel would have burnt out by now.
 
#10
The first AR i ever built was in the mid 90's before all ofthe heavy uppers and billet uppers.
It has a 24" SS bull barrel and has never given any issue with walking groups when it warms up, has been shot with bipod loaded and static as well as off of sandbags or the door window of a truck.
No difference other than some rests are more steady for accuracy.
 
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#11
My Krieger 24" bull barrels weigh 4 pounds, 8.5 ounces and I've never had any issues with the receivers that they're mounted in.



krieger_24_inch_ar15_001-2679405.jpg





55_grain_blitzkings_10_shot_group_at_100-2679318.jpg





krieger_24_inch_bull_barrel_on_scale_001-2774440.jpg



....
 
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#15
bigjake83 said:
For a barrel that heavy I would regardless of what's been done in the past use a heavy upper, Vltor MUR is a good option and the Seekins SP223 if want to run a specific handguard. JP makes some nice heavy walled uppers and so did Mega, not sure if they still make them. My personal favorite is the Seekins precision IRMT-3 UPPER. I'd also recommend you have your smith use a WOA Competition Barrel Extension.

WOA Extension Info

Shop White Oak Armament Online Store
www.whiteoakarmament.com www.whiteoakarmament.com
Click to expand...
Zev brought back the Mega sets, even built on the same original Mega equipment. Thick heavy walled upper like the seekins you like. The Mega is Thermal fit upper too.

934F93AA-C675-46F3-A9CA-CCC31131F1D9.jpeg
 
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#17
M4C proved small frame flat top uppers are wet noodles over 10 years ago; I can’t imagine a big, long, and heavy barrel helping that any. Granted now we have thick-walled billet receivers with true free float rails like that Mega, Seekins, and even Aero that may help the condition.
 
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#18
I recently built a 6mm ARC on Aero Precision upper/lower. Bought a Compass Lake bartlein- 24" with .936 gas block. Couldn't be happier with this setup. I've had no noticeable shift in POI going from bipod to barricades out to 600. I'm conscious of not loading into the bipod or the bag the way I do with my bolt guns. I think the platform will hold the heaviest barrel you're able to find for it. Wouldn't hesitate to recommend a 24" Criterion for this setup.

I do think with the way the handguard connects to the barrel nut one does have to be aware of how much you load a bipod or a barricade/bag- but that applies to the system regardless of barrel length.
 
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#25
I feel like all other things being equal, you get about 25 fps more per inch of barrel with the same load.

I also feel like barrel quality makes a big difference. My 24" Bartlein is over 200 fps faster than my 22" Balistic Advantage with the same loads (87gr Vmax and CFE223).
 
#26
y'all have given me great things to look at (and probably spend money on!) thanks! [/sarcasm]

I'm likely to end up with a Seekins upper next. I was holding out for a Wilson Combat upper to match the lower, but I like the idea of the handguard attaching to the receiver for a PRS gas gun rifle

Not that free floated handguards affect POI much that I can tell, but stiffer is better off barricades

M
 
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#27
JaoeyP said:
I feel like all other things being equal, you get about 25 fps more per inch of barrel with the same load.

I also feel like barrel quality makes a big difference. My 24" Bartlein is over 200 fps faster than my 22" Balistic Advantage with the same loads (87gr Vmax and CFE223).
Click to expand...

I have a 24in 223 BA barrel that seems slow also. it shoots pretty good, but it feels like i dont get very good speed out of it. Its only 80-90fps faster than my 18in larue for the same load.
 
#28
There is no valid equation to determine the change in muzzle velocity across a spectrum of barrel lengths and a variety of ammunition loads. The change in muzzle velocity will depend on a variety of interactive variables such as the barrel length spectrum involved (e.g. 20” to 16” versus to 16” to 14.5”), the operating velocity spectrum involved (e.g. a 20” barrel firing a load with a MV of 3,000 FPS compared to other barrel lengths versus a 20” barrel firing a load with a MV of 3,250 FPS compared to other barrel lengths) and the bullet weight spectrum involved (e.g. a 40 grain V-MAX versus a 75 grain OTM.)

The particular powder used in the loads will even cause variations between the spectrum of barrel lengths used. Throw in differences in barrel material, chambering, round count, etc, and the differences in the muzzle velocities between different barrel lengths becomes even more unpredictable. The only way to know what the difference in the muzzle velocities of differently barreled AR-15s is to chronograph them using a significant sample size in shot strings over the chronograph.

Here are some results from actual chronographing demonstrating the above variables. (All results are from semi-automatic AR-15s.)

An average difference in muzzle velocity between a 14.5” barrel and a 16” barrel using a 75 grain OTM load is approximately 86 fps. This gives you a difference of 57 FPS per inch of barrel.

An average difference between a 20” barrel and a 16” barrel is 108 FPS for a difference of 27 FPS per inch of barrel.

An average difference between a 20” barrel and a 24” barrel is 79 FPS for a difference of approximately 20 FPS per inch of barrel.



…
 
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#29
Curious if any of you on here that obviously have built far more AR's than me have built on the Wilson Combat heavy billet uppers with heavy longer than standard barrels ?
Mine only has a 16" fluted Recon barrel in 6.8spc that barrely peeks out the end of the handguard.
Just curious how they fare with heavy target barrels.
 
#30
Whelp, finally got rifle together and while initially it appeared to work well, I discovered about a .4 mil drop in POI when changing from front mounted bipod to bag (PRS-style off barricade). I'm using an Aero Precision upper and not sure of next move. I'm not seeing the velocity improvement I was hoping for with the 24" tube. May go back to 20 HBAR-style barrel.
 
#31
bigjake83 said:
For a barrel that heavy I would regardless of what's been done in the past use a heavy upper, Vltor MUR is a good option and the Seekins SP223 if want to run a specific handguard. JP makes some nice heavy walled uppers and so did Mega, not sure if they still make them. My personal favorite is the Seekins precision IRMT-3 UPPER. I'd also recommend you have your smith use a WOA Competition Barrel Extension.

WOA Extension Info

Shop White Oak Armament Online Store
www.whiteoakarmament.com www.whiteoakarmament.com
Click to expand...
I used Seekins receivers for 2x 22” Lilja heavy Grendel barreled builds. They shoot lights-out. I haven’t shot my 22” in forever though. I keep going shorter and shorter. My 12” is going to be my long Grendel pretty soon I think. Lol
 
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#32
Denver_AR said:
Whelp, finally got rifle together and while initially it appeared to work well, I discovered about a .4 mil drop in POI when changing from front mounted bipod to bag (PRS-style off barricade). I'm using an Aero Precision upper and not sure of next move. I'm not seeing the velocity improvement I was hoping for with the 24" tube. May go back to 20 HBAR-style barrel.
Click to expand...
If you aren't try a neutral load on the bipod. Ars are more sensitive to loading the bipod by far
 
#33
Dustyplyr said:
If you aren't try a neutral load on the bipod. Ars are more sensitive to loading the bipod by far
Click to expand...
Neutral all the way, all the time! I know some advocate for forward loading the bipod but I've never found much difference in accuracy between forward loading and neutral, at least with something that recoils as little as a 223.

Guess I'm a bit of a slow learner as Kinked pointed out this exact issue.
Kinked_Chrome said:
I have built 2 small fram guns with 24in bull barrels and .936 gas blocks. One a 6 arc, the other a 223 wylde. Both guns would shoot .2mil groups consistently at the bench and both of them have almost .5mil difference in POI between shooting from bipod and bag. My large frame gassers are .1mil maybe .2 difference between bipod and bag with heavy bull barrels.
Click to expand...

Of course, now that I understand the problem, I'm finding a lot of posts on the issue.

I'm also laughing a bit about when I used to shoot NRA High Power back in the 90's with an AR. I recall the recommended method for sitting and prone positions was to adjust sling length so you had to push the AR forward and the butstock into shoulder. Once adjusted correctly the rifle would stay in place just by sling tension and no muscle effort. The hotrod ARs had a free-floated handguard that looked mil-spec. That sling tension had to be influencing POI but suspect it was lost in the noise at 300-600 yards and using open sights.

I've ordered a Vltor MUR upper so will see if that helps.
 
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#34
bigjake83 said:
For a barrel that heavy I would regardless of what's been done in the past use a heavy upper, Vltor MUR is a good option and the Seekins SP223 if want to run a specific handguard. JP makes some nice heavy walled uppers and so did Mega, not sure if they still make them. My personal favorite is the Seekins precision IRMT-3 UPPER. I'd also recommend you have your smith use a WOA Competition Barrel Extension.

WOA Extension Info

Shop White Oak Armament Online Store
www.whiteoakarmament.com www.whiteoakarmament.com
Click to expand...
I’m probably going to have to replace the heavy contour barrel on my 14 year old Stag Varminter. It’s quite a bit larger than .936 & Stag doesn’t make the parts anymore. Do you think that WOA extension would be compatible?
 
#42
The standard flat top upper flexes quite a bit. Years back when Eric Kincel was still with Vltor, we toured the plant. They gave us the run down on how they used lasers to measure the receiver flex. This was part of the driving force behind the MUR.

Now you'll see that BCM has that beefed up Upper on some of their new upper halves. Kincel is, to my knowledge, still designing for BCM now.
 
#43
JS8588 said:
Is the barrel bedded? I know the MUR usually isn't thermal fit.
Click to expand...
Not bedded. I've tried bedding on an admittedly mediocre barrel and didn't have great results. My concern with bedding is trying to remove barrel at some point in future.
The MUR fit with almost no slop but no heat required. I "faced" the previous Aero upper as the barrel seemed to have a slight pivot in one direction, just pressing with hand. The MUR had this as well but only slightly. On both uppers this pivot went away as soon as barrel nut made contact with barrel extension ring.
TheMarkm87 said:
The standard flat top upper flexes quite a bit. Years back when Eric Kincel was still with Vltor, we toured the plant. They gave us the run down on how they used lasers to measure the receiver flex. This was part of the driving force behind the MUR.

Now you'll see that BCM has that beefed up Upper on some of their new upper halves. Kincel is, to my knowledge, still designing for BCM now.
Click to expand...
After looking at various uppers, I'm convinced the weak part of the upper is the threaded extension which the barrel nut threads to. Except for uppers like the Seekins IRMT, they all seem to have the same dimensions in this area and I would expect the same amount of flex. Maybe a monolithic upper could overcome some of my issue but unlikely I'll go that route.
 
#44
Denver_AR said:
they all seem to have the same dimensions in this area and I would expect the same amount of flex.
Click to expand...

Not so, according to the guys who did the MUR. The A2 upper, which has the same threaded extension, did not have the flex issue.

Now not too many people want a fixed carry handle anymore, so the MUR and the new BCM upper were specifically designed to reduce this.

None of us have the instruments to measure the standard flat top compared to the MUR or BCM, so I have no way to quantify the validity of the design improvement. And for what it's worth, I only have one MUR, and the rest are standard Colt upper receivers.
 
#45
TheMarkm87 said:
The standard flat top upper flexes quite a bit. Years back when Eric Kincel was still with Vltor, we toured the plant. They gave us the run down on how they used lasers to measure the receiver flex. This was part of the driving force behind the MUR.

Now you'll see that BCM has that beefed up Upper on some of their new upper halves. Kincel is, to my knowledge, still designing for BCM now.
Click to expand...
If you take a piece of aluminum and stick a steel rod in it, it will always flex a little under pressure.
 
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#46
Denver_AR said:
Whelp, finally got rifle together and while initially it appeared to work well, I discovered about a .4 mil drop in POI when changing from front mounted bipod to bag (PRS-style off barricade). I'm using an Aero Precision upper and not sure of next move. I'm not seeing the velocity improvement I was hoping for with the 24" tube. May go back to 20 HBAR-style barrel.
Click to expand...
Are you using the standard Aero upper or the M4e1 upper with the built in barrel nut?

FWIW, my Vltor MUR and WOA TR handguard show a .4mil shift low when going from a bipod to a bag. 27oz 16" barrel + ~15oz of a 5.8" suppressor (21-8"/~42oz). I do my best not to load into the bipod.
 
#47
Denver_AR said:
Whelp, finally got rifle together and while initially it appeared to work well, I discovered about a .4 mil drop in POI when changing from front mounted bipod to bag (PRS-style off barricade). I'm using an Aero Precision upper and not sure of next move. I'm not seeing the velocity improvement I was hoping for with the 24" tube. May go back to 20 HBAR-style barrel.
Click to expand...
belated reply, sorry.

i'm wondering if in situations like this, lapping the receiver front face, and thermo-fit or shims, helps to lock the barrel in for a rock-solid connection. And, as mentioned above, using the Aero Enhanced upper. :unsure:
 
#48
PBWalsh said:
Are you using the standard Aero upper or the M4e1 upper with the built in barrel nut?

FWIW, my Vltor MUR and WOA TR handguard show a .4mil shift low when going from a bipod to a bag. 27oz 16" barrel + ~15oz of a 5.8" suppressor (21-8"/~42oz). I do my best not to load into the bipod.
Click to expand...
Standard Aero as I wanted to use a long handguard with a built in arca rail. If that extension on the Enhanced Aero is one piece as it appears to be in pictures, that may be a much stronger solution and go a long way to prevent or at least reduce pressure on the handguard from influencing barrel shift.
(Man, I wish I hadn't seen that! :LOL: )

rpoL98 said:
i'm wondering if in situations like this, lapping the receiver front face, and thermo-fit or shims, helps to lock the barrel in for a rock-solid connection. And, as mentioned above, using the Aero Enhanced upper. :unsure:
Click to expand...
I did lap the face of the Aero and didn't notice any improvement when changing positions.

At a recent local match met up with a shooter running a JP with essentially same barrel, suppressor build. He also mentioned he sees about .4 shift between bagged and bipod positions. Between comments here and my own experience, I'm convinced this POI shift will always occur when using an upper with standard threaded extension.

Before swapping to the Vltor upper, I taped a laser to the end of the barrel then watched the dot through scope while changing from bipod to bagged positions. While not super precise, it was very plain to see the laser's POI shift between positions. This was also very consistent and repeatable between positions.
 
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#49
I got an Aero enhanced reciever and handguard in for testing. Should test next week.

Oh, and www.sgtofarms.com makes enhanced Arca rails for the Aero M4e1 upper.

www.sgtofarms.com

AR-15 15.5" ARCA Handguard | Sgt of Arms

This handguard is one of the most versatile handguards on the market. It has full M-Lok capabilities on both sides and the bottom but also has a full ARCA Swiss Rail on the bottom. The ARCA rail is great for locking into a tripod or being able to move your bipod to any point on the handguard...
www.sgtofarms.com www.sgtofarms.com
 
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#50
I have a 224 Valkyrie on a 24" barrel fluted, 6.5 twist, no muzzle device, measures .856" at the muzzle.
Its on a standard AR Areo upper, trued, glued, bolt carrier centered.
Capable of .5" 5 shot groups...note: with 3 shots through the same hole, with 95 gr SMK.
So....standard, forged, milspec recievers, work just fine, on bull barrels, no need to go high dollar billet, unless ya care to...
Your coin, your gun.
 

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