XCR-M comparison; light profile barrel to heavy profile barrel

[Astute Observer]

So I decided to purchase a light barrel and keymod upper for my XCR-M. I found the picatinny rail and heavy-profile barrel were pretty hefty, and wanted to trim it down. However, with both a heavy and light profile barrel in my posession, I decided to do an A/B comparison. This is the first sort of comparison I've ever done, please offer any constructive criticism of my methodology. Where there are sloppy methods used, I try to mention it up front.

So I went to the range today and I fired four different ammo types out of both barrels, and came up with significantly different results for the two barrels.

While I have two receivers, I fired both barrels out of the same receiver. I didn't want to switch the receiver or optic, as I wanted to minimize the variables and just test the barrels. Optic used was a Millett 1-6x DMS. The centre dot was about 1.5 MoA thick unfortunately, so not the best precision optic IMHO. The setup looked like this:

Switching the barrel moved the point of impact about 14" off at 100m. I felt that's a pretty big difference for a rifle that has it's quick barrel change as the primary feature. However, I was quite pleased when I switched back, that the adjustment was the exact opposite - 14" back. So removing and replacing the same barrel returns to the exact same point of impact.

So here's the final results right up front in a chart... Numbers are minutes of angle (MoA) that I shot with an XCR-M using a light barrel or heavy barrel, and the type of ammo used.

I did a partial test like this in June 2014, and included those results as well. Since June 2014, Dave at Wolverine replaced my muzzle brake, gas block and gas tube on the heavy barrel in an effort to improve accuracy. It worked, if you compare the 2014 to 2015 data for the heavy barrel. Other factors that changed from 2014 - 2015 include the bipod. The 2015 test used a Tango Down bipod, while the 2014 used a FAB Defence T-Pod G2. Unfortunately I didn't have the same bipod available from last year. Of course the weather was different too. It was fairly windy today (gusting to 25 kmh I would estimate) while the day in June 2014 was relatively still. But all in all, I think the test is nonetheless revealing.

So let's look at the data!

The 2014 numbers show that the heavy barrel is indeed slightly more accurate than the light, even right out of the box. If you compare the results from 2014, the difference was about 1 MoA or so average for all ammo types. But for me, shooting 5-7 MoA is not satisfying at all, for either barrel.

From 2014, the light barrel:

7.62x51 Norinco. 4.75" group at 100m. Shot from light barrel June 2014.

180 grain Winchester Super-X Power-Point. 6.8" group at 100m. Shot from light barrel June 2014.

150 grain Remington Express Core-Lokt. 7.1" group at 100m. Shot from light barrel June 2014.



From 2015, the light barrel:

150 grain Remington Express Core-Lokt. 4.2" group at 100m. Shot from light barrel 23 May 2015.

180 grain Winchester Super-X Power-Point. 4.25" group at 100m. Shot from light barrel 23 May 2015.

7.62x51 Norinco. 5.3" group at 100m. Shot from light barrel 23 May 2015.

150 grain Hornady American Whitetail. 3.6" group at 100m. Shot from light barrel 23 May 2015.



From 2014, the heavy barrel:

180 grain Winchester Super-X Power-Point. 4.75" group at 100m. Shot from heavy barrel June 2014.

150 grain Remington Express Core-Lokt. 3.1" group at 100m. Shot from heavy barrel June 2014.


From 2015, the heavy barrel (shot twice to confirm I didn't just get lucky):

150 grain Remington Express Core-Lokt. 1.75" and 2.4" groups at 100m. Shot from heavy barrel 23 May 2015.

180 grain Winchester Super-X Power-Point. 2.2" and 2.25" groups at 100m. Shot from heavy barrel 23 May 2015.

7.62x51 Norinco. 2.6" and 1.8" groups at 100m. Shot from heavy barrel 23 May 2015.

150 grain Hornady American Whitetail. 1.75" and 1.9" groups at 100m. Shot from heavy barrel 23 May 2015.
I think I jerked the trigger on that one flier - I could have had a 1" group there potentially.

All in all, I think that the heavy barrel is much more satisfying. The weight difference was not worth the difference in performance. I also conclude that if you're having minute-of-pie-plate accuracy, your gas block might be loose in your receiver - that was the problem with my heavy barrel back in 2014, and might be the problem with my light barrel still.

Hope some of you found this helpful!

 

[Astute Observer]

On a completely different note, I did get one stoppage and it was the weirdest one I've ever seen. It was double-feed where the REAR end of an empty case being ejected was thrust back into the chamber by the next round being loaded. Took a pair of pliers to get that out. I turned down my gas setting from maximum to one-below maximum and she ran fine after that. This was using the heavy barrel.

 

[drifter dave]

Interesting!
No one with light barrels seems to have undertaken this test.

 

[saskcop]

Great review. Where did you get the keymod upper? How much dare I ask for a separate upper?

 

[Astute Observer]

Great review. Where did you get the keymod upper? How much dare I ask for a separate upper?

I bought the upper from Wolverine Supplies. Special order, the upper was $799 plus tax, minus 5% for military discount.

I purchased an upper, gas tube, and light barrel all together. My intention was to set up two complete uppers (less piston, bolt and bolt carrier), one for longer range shooting with the old upper and heavy barrel and the other with the keymod upper with light barrel, for fun close-in shooting. That way I wouldn't have to re-zero with barrel changes because the point of impact shifts so much.

But now I'm thinking that I'll just use the heavy barrel and keymod. If I can get the gas block replaced on the light barrel I might be able to put it to use, but as is, minute-of-pie-plate at 100m doesn't satisfy me at all.

 

[saskcop]

Sounds good. Thanks!

 

[Gryphon Energetics]

Fantastic post, thank you for sharing! I have oft maintained the XCR-M is more accurate than people give it credit for. With the right ammunition, that is.

With Hornady 150gr SSTs I managed to place three out of five rounds into a ragged hole at 60m. That surprised me. The remainder of the group constituted less than 2 MOA. It's a good platform.

 

[Predator]

Great post. Thanks for sharing.

 

[TG929]

Good view, it does tell the difference between light and heavy barrel.
I did encounter the same stoppage you experienced earlier this year. However, I was able to clear the chamber with little difficulty. I think the reason for your brass to be stuck was because your bolt slammed both the empty case and the cartridge against the chamber.

On the side note, you should get a better optic and try again. Based on my experience with the gun, XCR-M is definitely capable of 1-1.25 MOA grouping with correct ammunition.

 

[Astute Observer]

Good view, it does tell the difference between light and heavy barrel.
I did encounter the same stoppage you experienced earlier this year. However, I was able to clear the chamber with little difficulty. I think the reason for your brass to be stuck was because your bolt slammed both the empty case and the cartridge against the chamber.

On the side note, you should get a better optic and try again. Based on my experience with the gun, XCR-M is definitely capable of 1-1.25 MOA grouping with correct ammunition.

Well, I could blame the optic - but I also think I'm a 2 MOA shooter.

If I redo this test, I'll go and get a lead-sled and really sandbag 'er down, and remove me from the equation as much as possible

 

[Ar180shooter]

My question is how long did you take to shoot the groups? After 3 or 4 shots, I've found that the light profile barrels get really hot, and should have a chance to cool down before proceeding.

I'm asking because my experience with the light profile L's is that there is no appreciable difference in accuracy as long as you take your time when shooting the string and don't allow the barrel to get too hot.

 

[Astute Observer]

My question is how long did you take to shoot the groups? After 3 or 4 shots, I've found that the light profile barrels get really hot, and should have a chance to cool down before proceeding.

I'm asking because my experience with the light profile L's is that there is no appreciable difference in accuracy as long as you take your time when shooting the string and don't allow the barrel to get too hot.

Great question, I should have mentioned it in the earlier post... I waited until the barrel was just warm to the touch in each case. That time varied, but was between 3-5 minutes between five round groups

 

[markwhuron]

Would you please be able to measure the diameter of the two different barrels for me? With a calliper if possible.

Both sides of the gas block would be great!

I am really curious what the difference is.

I believe I have the heavy barrel, because it is HUGE. lol

 

[EDF339]

My xcrm is back to wolverine foe gas block/gas tube upgrade but too baf that the new 3 side port brake doesnt ome with teh upgrade package anymore.

 

[vdog]

thanks. this is really helpful.

 

[Astute Observer]

thanks. this is really helpful.

No prob!

My light barrel and upper receiver is actually in the mail right now, coming back from Wolverine after getting the new gas block and gas tube installed. So I plan to post an update comparing the barrels again in the next couple of weeks.

 

[Pr589]

Great question, I should have mentioned it in the earlier post... I waited until the barrel was just warm to the touch in each case. That time varied, but was between 3-5 minutes between five round groups

I think it would be important to let the light barrel cool in between shots rather than between 5-shot strings...if I'm interpreting what you say correctly.

Interesting test. I wonder how the XCR would do with some load development? Those groups are quite good for a semi with commercial ammo.

 

[JDForBrkFst]

When I get a chance to I'm going to revise my old post about the XCR M with my accuracy notes since having the rifle replaced. I had atrocious accuracy from my initial light barrel key mod. Both Cabelas and Wolverine did good by me. They ended up giving me a new rifle with the upgraded gas block and tube. It shoots reasonably well, although I plan on letting it cool between shots next range trip to see if that makes any notable difference. Kudo's on the heads up about hornady american white tail. It shoots well out of my rifle, I took my deer last season with it. Standing 72M, one shot, catastrophic heart damage.

 

[Astute Observer]

When I get a chance to I'm going to revise my old post about the XCR M with my accuracy notes since having the rifle replaced. I had atrocious accuracy from my initial light barrel key mod. Both Cabelas and Wolverine did good by me. They ended up giving me a new rifle with the upgraded gas block and tube. It shoots reasonably well, although I plan on letting it cool between shots next range trip to see if that makes any notable difference. Kudo's on the heads up about hornady american white tail. It shoots well out of my rifle, I took my deer last season with it. Standing 72M, one shot, catastrophic heart damage.

Absolutley, Wolverine are awesome for their service. I just got my new upper back and had them replace the gas system for my light barrel, will compare them soon!

And yeah - the Hornady American White Tail was surprisingly good at 100m for a "battle rifle". I haven't spent the money on match grade ammo yet, and I will be getting into reloading this spring... Given the performance with hunting ammo, I figure that handloading match grade bullets I can get this guy down to < 1 MOA... With the heavy barrel at least.

 

[EDF339]

XCRM gas block/tube upgraded by wolverine. It loves hand load for sure and ppl with best shooting skill should be able to bring it to sub moa
100M
shooting with bipod and rear bag
my set-up

PMC 147GR(4.057)

5 rnds grouping with varget(1.071)

10 rnds grouping with H335(1 flyer maybe?1.390.5)