MAX-11/15 with 16” Barrel: Test Results and Video

[Eric]

The MAX-11/15 is a remarkable, well-designed, well-constructed upper receiver system and a lot of fun. I bought two of them. For the second one, I bought a 16” barrel so that I could increase the muzzle velocity and use it with one of my Trijicon ACOGs and have the bullet drop compensation lines in calibration.

I know a lot of people in the NFA world and on this site love short barrels and I do like the stock MAX-11/15 for its overall length. It is a good length for mounting a suppressor, for example, but in general, I prefer longer barrels as I don’t like to give up any more bullet velocity than necessary. I actually prefer the AR-15 with a 20” barrel over the carbine versions, but because of the limitations with the M-11/Nine lower receiver, a 20” barrel on the MAX-11/15 would be quite unwieldy. The 16” barrel gives me most of what a 20” barrel would do without being too unwieldy. In most cases that I tested, it provides an extra 300+ FPS. A 20” barrel would only give about 100 FPS on top of that. So I am completely happy with the 16” barrel on my MAX-11/15. It’s sort of my “Poor Man’s M249 SAW.”

I’m attaching a photo of my two MAX-11/15s and a chart showing the bullet velocities I measured with the 10.5” and 16” barrels. With a 16” barrel and the original Lage MAX-11 fixed stock (seen mainly in the video), the overall weapon is 1/2” shorter than a standard AR-15 with a 20” barrel. With the Lage AR15 Monolithic Stock Adapter and Magpul ACS stock (seen briefly near the beginning of the video), it is 1/4” longer than the AR-15. See attached photo.

Based on the results I had with my first MAX-11/15, I simply set the gas block on the 16” upper to be open 10 clicks as a starting point. So far, I have made no effort to fine tune it. I will later but have not yet. With the ten clicks, I did some quick and dirty calculations and estimate that with 55 grain Winchester 5.56, I’m getting about 925 RPMs. I would like to lower that a bit and I think I can. A quick and dirty calculation with the 55 grain TulAmmo looked to be about 775 RPM which is actually not bad.

Here’s a video showing some of the testing I did with the 16” barrel. Note that the bullet velocities for the 55 grain rounds shown in the video are not reflected in the attached chart. I shot those clips after I made the chart:

https://www.youtube.com/watch?v=g1GHe-Bl5ec

(Note: the above link is to a slightly edited, shorter version of the video I originally posted and incorporates the bullet velocity chart shown below)

 

[Mackjack]

Nice write up!

 

[agriebel]

Interesting that the tula 62gr was faster than the 55gr.

 

[rybread]

Looks good nice work. I have an M249 stock I might put on my buffer tube- if anyone has already done that let me know how!!

 

[Doobis]

Fantastic video! That is the exact setup I have been wanting to see the 11/15 in.

 

[Eric]

Interesting that the tula 62gr was faster than the 55gr.

That caught my attention, too. I wondered if that was just a fluke with that particular lot number or if that's normal for TulAmmo 62 grain. Most of the ammo I tested was purchased within the last year. That 62 gr box was purchased in 2016.

 

[lokifox]

I like the barrel! What was the make?

 

[Swampfoxoutdoors]

Like the looks of that longer barrel. Now needed to try out a 20-24" barrel.

 

[Eric]

I like the barrel! What was the make?

https://www.dsarms.com/p-16905-dsa-...17-twist-straight-fluted-stripped-barrel.aspx

 

[gorillastomp]

Eric you are just an awesome guy! Very good video and write up!

 

[Eric]

Just a note about the above video: I replaced the original link with a link to a slightly revised version. It replaces most of the Chrony bullet velocity tests with the chart summarizing the bullet velocities. It's more than a minute shorter.

https://www.youtube.com/watch?v=g1GHe-Bl5ec

 

[IndustrialRescue]

Excellent!

 

[EL DUCE]

Eric you are just an awesome guy! Very good video and write up!

Yep! Thank you!

 

[M16er]

He hates those cans!

 

[PDXsparky]

Great video. I'm still smiling about it.

 

[A&S Conversions]

Eric, have you thought of using a 16" barrel with a mid-length gas system? I have found that the mid-length gas system has a significantly slower cyclic rate than that of a carbine length 16" barrel. Just a thought. Thank you for making this post.

Scott

 

[Eric]

Eric, have you thought of using a 16" barrel with a mid-length gas system? I have found that the mid-length gas system has a significantly slower cyclic rate than that of a carbine length 16" barrel.

A mid-length gas system is a good thought. When I ordered the 16” barrel, I wasn’t really thinking about its effect on cyclic rate. I was really only thinking about muzzle velocity and the fact that the carbine length gas system would be a direct swap with the 10.5” barrel. That said, I did finally get around to playing with the gas block settings this last weekend and plan to do more this week. As indicated above, as a starting point, I simply set the gas block at 10 clicks based on my experience with the 10.5” barrel. But I now know that 6 clicks open is better and I may be able to go lower. At 6 clicks, I was seeing 62 grain TulAmmo running at about 650 RPMs which is probably as low as I want to go. The Federal brass was running at about 880 RPM. I’m going to see if I can get that lower. For me, I sort of consider 750 RPM to be the sweet spot, but I can be happy with 880.

By the way, I am going to update my bullet velocity chart because I’m finding that the velocities for TulAmmo are different for more recent purchases. The 62 gr. velocity has gone down and the 55 gr. velocity has gone up. I don’t know if that’s a quality control issue with TulAmmo or a deliberate choice on how they are loaded.

I’m glad folks have enjoyed the video. Cutting an even swath through a row of soda bottles in full auto is harder than it looks. It’s especially annoying when an exploding bottle pushes an adjacent bottle over before you have a chance to shoot it.

 

[Eric]

Here is an updated chart showing bullet velocities coming out of my MAX-11/15 with the 16 inch barrel. The main reason for posting this is because I was suspicious of my previously posted results that showed the 62 grain TulAmmo was faster than the 55 grain TulAmmo. I wondered if that lot of 62 grain ammo was an anomaly so tested a few other lots. What I found was that I had a lot of 62 grain rounds apparently from 2014 that are, in fact, loaded hotter than other lots that I’ve since tested.



This new chart reflects the results for ammo that I have bought within the last year. This is true for all the brands except the Lake City ammo. I’m not sure what year that is from. The results for the 62 grain TulAmmo are more in line with what I’d expect. Moreover, in most cases, I’ve increased the sample sizes from 5 rounds to between 10 and 20 rounds on this new chart.

I’m also posting a chart showing the Rate of Fire (ROF) for several common ammo types. These are the results I obtained after adjusting the gas block to its optimal setting following the instructions in the MAX-11/15 owner’s manual.



Surprisingly, the result I obtained for all the ammo I tested was that opening the gas block to 6 clicks produced the lowest rate of fire that would cycle consistently. That makes it easy for me because I can just leave the gas block open to 6 click for anything I shoot. This is a very different result than what I experienced with my MAX-11/15 with the 10.5” barrel. In that case, the optimal setting ranged from 7 to 11 clicks and depended very much on the type of ammo.

I do not own one of those nifty electronic timers that determines rate of fire. The way I measured ROF was to record a ten round burst on video. I then loaded the file into Quicktime or Adobe Premiere and looked at the time stamp for the frame where the bolt closes to fire the first round and the time stamp where the bolt closes after the last round was fired. The RPM would then be 600 divided by the time duration of the burst. Since the video is only recorded at 30 frames a second, I’ve rounded the results to two significant figures. I’m satisfied with the result because the ROF for the same type of round will vary somewhat from one test to the next.

Anyone curious to see my ROF tests or who wants to measure the ROF yourself can view the video here:

https://www.youtube.com/watch?v=T5K21JwlwEM

I will eventually post my gas block setting and rate of fire results for the 10.5” barrel in a separate thread.

 

[strobro32]

Very nice Eric. That is great information.
My only suggestion is don't edit the video to create longer strings for ROF tests.

When I do rate of fire testing I use a program called Audacity. It is a free audio recording program. It lets you see and select the shots down to the millisecond. Medphys told me about it. After comparing the results of this program to multiple Pact timer tests, I convinced it's as accurate or more.

Because the first and last shot on most open bolt guns are difficult to determine by sound waves, it's best to use more than 10 shot strings to find ROF. I like to use the longest strings of automatic fire to determine ROF. If someone posts a video of 20 or 30 rounds fired, I throw out the first and last shot of the string to get an accurate count.

 

[Eric]

Thank you for the feedback Strobro32. My reason for editing the video to create longer strings was because I felt it was easier to get a qualitative "feel in your head" for the ROF and the relative differences if the burst was longer. I didn't think there would be too much interest in viewers trying to actually measure the ROF from the video. All my measurements were based on the actual video image of the bolt closing at the beginning and end of the burst. I understand the difficulty of trying to determine the ROF by sound waves because one of the things I did was to look at the graphical image of the sound track and calculating a ROF from those. It turned out that was much less consistent so I didn't use those values.