I need a Physics lesson...

sliponby

New member
My humble pistol collection consists of 3 9mm's, a .380 and a 38sp. I carry a PM9 or G26 and occasionally an LCP.

My question is will a heavier weight round such as a 147gr facillitate more reliable operation (less likely ftf's etc.) than a lighter weight such as 115gr? It seems like I've read somewhere that the heavier bullet is the way to go.

My carry round in my PM9 is Speer GD's 124gr+p short barrel and in my G26 I run Winchester Bonded PDX1 124gr+p.

Thanks for your input on this subject.
 
My question is will a heavier weight round such as a 147gr facillitate more reliable operation (less likely ftf's etc.) than a lighter weight such as 115gr?

It depends on the recoil springs. Too weak a spring will cause malfunctions as will a too heavy a spring.

Most semi-autos allow for switching springs to fit your ammo.
 
It depends on the recoil springs. Too weak a spring will cause malfunctions as will a too heavy a spring.

Most semi-autos allow for switching springs to fit your ammo.

yeah this one is true.

My Coonan Classic has a light spring to shoot 38 specials and a Heavier 22lbs spring to shoot 357 magnums. I have a lot of 110 grain 357 magnums that I think will feed better with a lighter spring because the gun feeds any thing 125 grains or heavier great but the 110s are a crap shoot. I have some 90 grain extreme shock (over priced) ammo that I have not tried yet but I assume it is the same at the 110s.
 
My question is will a heavier weight round such as a 147gr facillitate more reliable operation

Maybe, maybe not. As kraigwy said, it is dependent on the springs. But it is also dependent on slide weight, feed ramp angle and shape, magazine lips and follower, and a few other subtle details.

Most 9mm's should be able to run 115-147 gr. ammo reliably with no alterations. But many guns have a certain type of ammo they don't like, often because of bullet profile. If yours is hiccuping, try a different type or brand.
 
To add one point to the excellent, already-posted comments, a heavier projectile (all other factors being equal) will reduce slide recoil speed and will therefore potentially extend the structural fatigue life of the handgun. Please understand that the foregoing is very theoretical: (1) any reasonable firearm is designed to handle all such loads and (2) springs should be regularly changed and, as already noted, can/should be altered for the ammunition used. Nevertheless, the impact of the recoiling slide with the frame (especially if they are dissimilar metals, such as a steel slide and an aluminum frame) can eventually cause crack initiation/propagation. This is why some individuals use "muffs" (to reduce impact forces), although -- as with all engineering matters -- there is a downside to their use.
 
Use the weight that the gun was designed for ! Originally the 9mm was designed for 115-124 gr . However there have been weights from 90-147 gr. Considering the variables I think for that case 115-124 weights are still the best.
 
If the particular 147 grain loading has a higher momentum it will cause the slide to come back with more force. It is easy enough to determine the momentum of the bullet, just multiple the mass x velocity (the power factor). While this won't get units that are typically useful it is still a measure of momentum.

If you want to shoot the lighter rounds you can swap out the recoil spring to something lighter as was said before.
 
mete, you have actually posted two separate conditions. First, you said to use the weight the gun was designed for. But then you said (implied) to use the weight the cartridge was originally designed for.

I would only worry about original cartridge design if using guns from close to that design period. Modern guns should be designed to take modern, standard variants of the cartridge.

One could check the owner's manual or ask the manufacturer's CS, if in doubt.

I find my 9mm pistols hit closest to POA with 147 (FNX-9 and PM9) and 124 (BHP but I had the sights regulated for 124 GD).

All three feed 115-147. POI varies with weight, as one would expect.
 
My second sentence was a historical comment .
When we look at guns like the Walther P38 and Luger - they were designed for the 124 gr bullets. There is a long jump from mag to chamber with these guns an they didn't like short bullets like a 90 gr .Those were less reliable.

In the early days of the 40S&W , HK was about to release a pistol to the market .At the time somebody started selling a 135 gr bullet .HK held back to make changes so the pistol would reliably function with that light bullet.

Another significant change in pistols was designing the feed ramp to be able to function with various shaped bullets ,JHP etc. Come to think of it the Luger originally used bullets of truncated cone shape .When they came out with the drum mag IIRC the TC bullets were not reliable so they switched to RN !!
So it all comes down to picking the round that the gun is designed for and the particular one that gives best reliability and accuracy. Even if it's not YOUR favorite.:)
 
MLeake said:
POI varies with weight, as one would expect.

Agreed... it's been my experience heavy slow bullets hit higher than light fast ones.

As far as the spring issue, my opinion still rest on what my old mentor showed me. Find the ammo that your pistol likes for accuracy. No matter what that turns out to be, watch your brass. If the spent brass is flying 20 feet into the weeds, you need a heavier spring. If it barely bubbles up and rolls onto your foot, you need a lighter spring. Goal is 6-10 feet away in a nice little pile. Hope that helps.
 
SmokyBaer: said:
Agreed... it's been my experience heavy slow bullets hit higher than light fast ones.

As far as the spring issue, my opinion still rest on what my old mentor showed me. Find the ammo that your pistol likes for accuracy. No matter what that turns out to be, watch your brass. If the spent brass is flying 20 feet into the weeds, you need a heavier spring. If it barely bubbles up and rolls onto your foot, you need a lighter spring. Goal is 6-10 feet away in a nice little pile. Hope that helps.

Next we'll be debating whose pistol groups its spent brass the tightest. :D

Now there's an original thread topic!

:)
 
All current manufacture semi-autos ought to be able to handle standard loads without ftf's. A couple of wrinkles are particular to your specific situation, however: you're using compact nine's and you're running +p ammo through them.

The smaller the pistol the less mass in the slide, so the designers build in a heavier recoil spring to keep the gun from beating itself to death. Unfortunately, a more massive slide and weaker spring is more forgiving than a less massive slide and a heavier spring.

Two things may be happening: the first is that you may be riding the recoil with a soft grip, robbing the slide of energy as it comes back. As previously stated, lighter slides and heavier springs like this less than larger pistols. If this is happening, your ftf will involve the round stopping partially into the chamber.

The second possibility is less likely, and has to do with the pistol timing. When a pistol recoils, the rounds in the mag actually compress the spring and drop down as the slide is coming back. The weapon is timed so that by the time the feed rail is on its way forward, the top round in the mag has returned to the point where the feed rail will push it into the chamber. If your ftf's involve the slide rail riding over the top of the round to be fed, you've got a timing problem. You'll wind up with an empty chamber. Like I said, not too likely.

Bullet weight can affect point of impact because the speed of the bullet dictates at which point during the recoil the bullet leaves the muzzle. Heavier bullets with the same recoil impulse will hit higher because they are slower, and exit the bore after it has risen further during recoil. Bullet weight should not affect reliability because commercial ammo is loaded within a fairly narrow range of pressures (SAAMI). The pressure is what generates the recoil, not the bullet weight. Usually handloaders, who may be operating out on the edges of the pressure range, monkey with the recoil springs to facilitate the use of particularly light or heavy loads.
 
To answer the OP's original question, a heavier bullet is neither inherently more or less reliable than a lighter bullet. As others have mentioned, a specific spring configuration might work better for different weight guns. It is also possible that the caliber, bullet shape/design, and bullet weight may make a bullet more or less stable depending upon the twist rate of the rifling. You usually talk about this more in connection with rifles.
 
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