We can guess and suppose all day about what our rifle should do with such and such ammo or accessory.  The only way to be sure how it will perform is to test specific configurations.  I wanted to find out five things about my rifle: 1) will the AAC Ranger 2 affect the velocity of my rounds, 2) will my short barrel diminish velocity so much as to make my ammo ineffective, 3) what is the max effective range of my rifle as configured, 4) how much quieter will the AAC R2 make my rifle, and 5) which will give better performance in my rifle, XM193 or M855?

Well, here's the data I compiled.  My conclusions are below...


1) Will the AAC Ranger 2 affect the velocity of my rounds?  Clearly it did, but not significantly.  It made the XM193 a smidge faster (10-20 fps average) and made the M855 a smidge slower (about 35-40 fps average), when compared to shooting with Phantom.

2) Will my short barrel diminish velocity so much as to make my ammo ineffective?  Nope!  With 2600 fps being the accepted minimum fps required for these rounds to reliably and effectively fragment, I've got plenty of room to spare.

3) What is the max effective range of my rifle as configured?  By this I mean how far out will the ammo still fragment effectively.  Both rounds drop an average of 200fps per 100 yards, so this means the XM193 will drop to 2600fps at 118 yards and the M855 will drop to 2600fps at 139 yards.  Plenty far IMO for this type of rifle (close quarters), this wasn't designed to reach way out and touch someone.

4) How much quieter will the AAC R2 make my rifle, as compared to the Phantom?  A lot!  The Ranger 2 is advertised to have a NR (noise reduction) of 32dB my tests showed just 14dB.  Without the can I recorded 118dB and with the can 104dB.  Bear in mind that ammo, location, etc will have an impact on this.  However 14dB is perceived as a little less than half as loud.  This means the rifle sounds twice as loud without the can.  This is good.  104dB is quiet enough for me to shoot a few mags without ear protection (though I don't) while 118dB is loud enough to potentially damage my hearing forever.

5) Which will give better performance in my rifle, XM193 or M855?  Well the M855 is slower, but its higher mass allows it to keep its velocity out to a greater range.  Realistically though 20 yards doesn't make or break either round for me.  What matters is that both function well in my rifle.  My 1/7 twist barrel stabilizes both just fine also.  I'm really pleased with both and will buy and shoot whatever is available.

I'm glad I spent a few hours measuring and recording this data.  I now know exactly how two of the most popular rounds will perform in my rifle.  I don't have to worry about what somebody else believes is better...I know what's better.  I now know also that a 14dB reduction doesn't sound like much on paper, but it does sound good on the range.  Have fun.

Thanks for posting that.  Much discussion and anecdotal evidence on the boards, but no hard numbers.

The minimum velocity for fragmentation of M193 and M855 is 2700 fps not 2600.  Can you post revised stats for 2700 fps?

Quoted: I'm sorry, but your rifle didn't meter 118 DB without a can and 104 with a can. Most suppressed 22s will barely be in the mid 110s. Would you care to specify what kind of device you used to measure this? Your fragmentation thresholds are also a bit off. Abort, regroup, try again pls. ETA: For reference, your rifle should have been somewhere aroun 165db with no suppressor, and around 133db with the suppressor mounted.

You're right, I forgot you were there...NOT!  Don't presume to tell me what results I did or didn't achieve.  You have no idea what my testing methods were.  Though I hate to be baited by a know-it-all like you, I'll bite.  My friend shot my AR, I held the dB meter at head height approximately 5' to the right of the ejection port.  Ever measured dB's there?  Didn't think so...

Of greater importance, beyond the actual numbers are two points you seem to miss.  1) that the can does make a noticable difference in the noise levels and 2) I can shoot comfortably w/o ears when using the can.  Those were the points you should have taken away from my post; then perhaps politely questioned my testing setup, before putting your foot in your mouth.  

Calm down, bud. Cowboy's right---you need a very expensive, properly calibrated meter in order to be sensitive enough to measure the peak of an impulse noise (eg. a gunshot).

Thanks for posting your data .

As a sidebar: I have noticed that I get changes in performance going from one flash hider to the next. For instance what is an ultra-reliable carbine w/ an A2 can become a picky eater with a Vortex. So I can see how various FHs will affect functioning as well. I need to buy a chronograph. I would love to know what the KX3 on my 10.5" pistol does to performance, it sure slams the bolt back. I can't help but think that all that back pressure must come at the expense of velocity.

Disclaimer: I know this is only anecdotal information and not performed to a standard testing protocol dictated by any internationally known governing body. But, in my experience, it is repeatable.

I also wouldn't consider 5 round groups of surplus military ammo a solid baseline to compare velocity differences between suppressed and unsuppressed.  You have a pretty wide velocity spread there and thats only 5 rounds.  You could do the test with match ammo and shrink the spread, or you could increase the group size for the control and suppressor groups (say 20-50 rounds for a solid average).

The numbers I've seen with a suppressor on both my 5.56 and .308 are typically higher then without by a few percentage points.

and the other posters are correct. sound meters capable of metering high speed impulse sounds like that are uncommon and expensive.  You should have questioned the data the first time you got a reading thats lower then your average paintball gun or BB gun.