TargetTalk

PETE S wrote: I am going to have to get a rifle case to because the barrel/compensator combination is so long it does not fit the factory case! Presently I remove the compensator to carry to and from the range and this changes the point of impact on the target.

Pete,
I solved this problem by shortening the barrel. My FP now fits in its case and has better balance as well. In addition, I did not find that the longer improved my shooting, so there was no loss in going back to the original sight radius.
YMMV
Fred

Next week I'm starting a new course here at the university where we make prototypes of mechanic objects. I've been playing with the thought of a compensator/dissipator based on a scaled down M82A1 muzzlebreak. I think this will be fun! =) I actually have the option of making it in solid titanium in our free form machine. =)

If this compensator is done you can surely expect a range report on it this summer! ;)

Yes - with hot enough ammo, you could push your competitors right out of their shoes, or at least out of their holding area :-P

great idea! Gonna convert the FP to .223 instead of .22 :P

Steve Swartz,
I started out with an off-the-shelf CM84 and then I put on the new long morini compensator. My reasoning was that the greater weight at the front end would dampen small natural vibrations. I also had the sight groove retooled so that the front blade sight is the same position as the off-the-shelf original. Is my physics off? Does more weight farther out actual dampen vibrations or does the theory not apply here?
Elliott Dushkin

Elliott:

Uh Oh "Release the Engineers!"

No, you are not entirely incorrect in your reasoning. Structural vibration in general has a few dimensions that may/may not be significant for accuracy: frequency of wave, length (duration) of vibration, and magnitude of wave. High magnitude, slower, longer wave vibrations tend to be bad mojo. Short, stiff barrels (pistols) generally have higher frequency, shorter duration, smaller amplitude vibrations. I think generally the "barrel vibration" issue is considered not very significant for low-powered pistols? That having been said- Couple of other points to ponder perhaps:

- It's "stiffness" if I remember my Statics course properly that is a key driver in vibration frequency and duration. But it's counter-intuitive a little. A relatively "limp" structure will vibrate in lower frequencies but for a shorter time; a stiffer structure will vibrate at higher frequencies for a longer time.

Part of the trade-off involved in longer barrels/shorter barrels is that you are affecting the "natural" frequency of the barrel in response to the round going off. So stiffness doesn't directly equate with damping, just the frequency. However I don't believe this is necessarily a significant factor for .22 LR pistols though? Barrel "whip" is a factor for accuracy in long barreled high-power rifles of course (and artillery pieces) but not low-power pistols so much.

- Damping with "cantilevering" (use of weight-distance "moment arms") can indeed be effective . . . but generally will first affect the natural frequency of the vibration (lengthening?) and will only secondarily reduce the "life span" of the vibration; shortening the duration a bit. Still not short enough to be gone by the time the bullet is gone though.

I don't have my CRC standards handy at the moment; perhaps another contributor can chime in (on the relationship between barrel length, stiffness, weight distribution, and wave characteristics)?

Anyhow

Assuming the actual barrel length is unchanged, by weighting and extending the end you may in effect be helping your pistol barrel emulate a rifle barrel (in terms of vibration) and this might not in itself be helpful from an accuracy standpoint.

But how does it feel? Is it easier to hold/follow through? I think the ergonomic effects would be more significant than any effect on absolute precision or "accuracy."

Steve

Elliott:

Sorry about the previous response. I was focused on barrel vibration damping and think I missed your actual point.

I agree with your reasoning for a couple of reasons. One, if Yur'Yev is to be believed, a higher rake angle combined with muzzle heavy feel is conducive to "loading up" or pre-tensioning the wrist and this directly contributes to stability.

Two- and this is not discussed so much by the true experts so I might be out to lunch- but you have the "Pointer Effect."

What the heck is the "Pointer Effect?"

It's kind of a Swartzism so needs a metaphor/analogy to describe.

Picture a golf ball with a long thin dowel stuck in it.

Scenario 1: put the golf ball in the palm of your hand, and point the dowel at a distant object.

Scenario 2: hold the dowel in your hand (golf ball at the other end of the dowel) and point at the distant object.

Scenario 1 is "squirrely" and Scenario 2 is "stable." It is easier to "hang the golf ball out there" and move the dowel end to point at a distant object than it is to hold the golf ball and try to point the twitchy dowel.

However

Many shooters prefer to have the center of mass of the gun enclosed in their hand. Those shooters would totally disagree with my description above and say it was exactly backwards.

Steve

elliott wrote:Steve Swartz,
I started out with an off-the-shelf CM84 and then I put on the new long morini compensator. My reasoning was that the greater weight at the front end would dampen small natural vibrations. I also had the sight groove retooled so that the front blade sight is the same position as the off-the-shelf original. Is my physics off? Does more weight farther out actual dampen vibrations or does the theory not apply here?
Elliott Dushkin

Elliott,
You should have the answer to your own (implied) question - does my modified gun allow me to shoot higher scores? Theory is great, but experimental results are crucial :-)

Fred