How Crazy Am I: Different Sounds From Different Rifling?

[TunnelRat]

Hi All,
So I had a fun day at the range yesterday. Brought with me some pistols, namely an M&P 9mm Fullsize, M&P 9mm Compact, HK P2000 9mm, and HK 45c. I shot the 9mms first, switching between them. I noticed something interesting. Now I could be completely crazy, but I swear that I could hear a difference between the pistols. I was shooting the exact same ammo, 115 gr Blazer Brass, through all of them. When I fired the HK P2000 I kept hearing this sound. It's hard to describe, but it had almost the after effect of a bit of a whistle, think firework, when I heard the report. I did not notice it with the M&Ps. Later when I shot the HK45c I noticed it as well. This was also Blazer Brass, 230 gr.

Given that it was the same shooter (me) the same location (I was in a numbered firing lane at an outdoor range), same time, and same ammo, that lead me to thinking about what could be different about the firearms. Barrel lengths were fairly similar. What was different is the HKs are polygonal rifle while the M&Ps are conventional rifling. Is it possible for the rifling to make a difference in the auditory report?

-TR

 

[James K]

It is possible that some rifling can allow more gas to escape around the bullet and produce such an effect, but it is also possible that the sound might come from the gun itself (spring vibration?) as the slide returns to battery.

It might be interesting to have a sound engineer run some tests but the cost would not be cheap.

Jim

 

[TunnelRat]

it is also possible that the sound might come from the gun itself (spring vibration?) as the slide returns to battery.

Hadn't considered that, I suppose it is possible.

I wish I could clarify the sound better. I also don't have anything of enough fidelity that wouldn't simply be drowned out by the noise if I tried recording.

 

[Brian Pfleuger]

A "fairly similar" barrel length could make a huge difference in muzzle pressure in handgun rounds. Also, any differences in chamber size and bore size will also effect pressures. I suppose that rifling pitch, style, even the number of grooves would also have some effect but I'd guess it would be masked by the larger factors.

 

[TunnelRat]

A "fairly similar" barrel length could make a huge difference in muzzle pressure in handgun rounds. Also, any differences in chamber size and bore size will also effect pressures.

While I see where you're going there, remember I noticed the difference with both the 9mm and 45ACP HKs. Thus it has to something inherent to both of those pistols. Given that the barrel lengths, chamber sizes, and bore sizes differ between the two HKs and yet I can hear it with both of them makes me question if those are the factors causing what I am hearing.

 

[g.willikers]

Could you play a tune with them?

 

[AndyWest]

Every time I shoot my 10mm G21 at the range, even with underpowered loads (that sound like 45 to me), someone recognizes the 10mm sound and gives me the thumbs up. It's bizarre to my tin ears, but some people can pick out very subtle differences, not just "bang" size.

 

[Archie]

Tune?

Could you play a tune with them?

Back in the day I could do "One Note Samba" on a submachinegun.

(Okay, okay. I'm sorry. I won't drift anymore.)

I'll have to pay more attention to the reports. I have mostly conventionally rifled (lands and grooves) handguns, with two H&Ks with polygonal rifling. I find more difference in calibers (larger bores being a bit lower in tone.)

Once upon a long ago, I remember hearing the bolt of the M14 I carried making a 'clank' when the bolt bottomed out in the receiver in recoil. I also remember the sound of the spring in the butt of the M16 when firing.

 

[rickyrick]

Are the barrels the same length?
That can make a perceptible difference in sound