Air Gun Home :: View topic - Does a heavier grained bb pack more punch than a lighter one

gage3780 · Member

Will a 7.2 grain bb pack more power hitting a target than a 5.1 grained BB., or is it just a waste of money buying the better bb for just target shooting? Question

Will a heavier grained one travel a greater distance also?

dobiman · Veteran Member

There is a guy on Youtube, RuneRebel who tests bb guns with different weight bbs and gives the velocity for each out of the particular gun. From that info, you can figure the energy from the bbs. There seems to be plastic bbs, steel bbs, and lead bbs that are tested. He also does an informal accuracy test on each bbs. Maybe you will find your answers there.

gage3780 · Member

Thanks for the info I will check I out.

shawn706 · Member

We shoot competition with 11/64 IN CHROME 52100 GRADE
24 ball bearings. We're mainly looking for consistency for what we do, but as my backstops can attest, the do hit harder. They're smaller diameter and heavier weight are also helpful shooting in windy conditions. Not sure what grain they are but I know they're heavier than the competition grade BB's that daisy sells. I got a survey from Daisy earlier this year after the National competition asking if coaches would be willing to pay more if they started sell ball bearings. $8 per thousand vs $4. I replied that I'd pay $16 to be able to use them at the National match.

cobalt327 · New Member

Custom fitted barrel ID's notwithstanding, for that to work well in the 'average' bb gun barrel the shot OD would need to be larger than ~0.172 (11/64"). Avanti BBs (Daisy's premium brand as I'm sure you know) measured the largest (thus are the heaviest) and had the highest average velocity in the vast majority of BB guns I tested them in- IIRC, I got a 2 fps increase in MV from a Daisy model 105 Buck using Umarex over the Avantis in a 10 shot sample but that was a single test so repeated tests or a larger sampling could negate this.

Of a randomly selected group of 50 Daisy Match Grade Avanti BBs, the diameters were:

1.735- 4
1.740- 45
1.745- 1

Now, if there were steel shot made to a higher ball bearing spec that were also at least 1.74" OD, I'd be all over them, too!

cobalt327 · New Member

icuppu · New Member

In responding to this question, I have no access to the original question, exactly, without going back, but for fear of Murphy's Law, i will go with the following:

Does a 7.4 grain pellet hit harder than a BB?

If your projectiles in question are travelling at the same velocity out the same power plant barrel then the heavier 7.4 pellet would hit harder and travel farther and faster at longer range due to its higher sectional density (SD), which would also give it a higher ballistic coefficient (BC); furthermore, it does this by overtaking the lighter 5.14 BB at longer distance; even though, the lighter BB would come out the barrel much faster, at first and in short range.

In continuation, if you are firing them from the same power plant gun, besides the heavier 7.4 pellet hitting harder, it travel less distance in the same amount of time as the lighter BB, at short range, along with having a higher ballistic arc than the lighter 5.14 grain BB that will shoot flatter and travel faster, at first, due to its lighter mass, but will fall behind at longer range due to its lower BC.

The reason the pellet hits harder from the same power plant gun is because the skirt seals much better than the solid round BB allowing more gas kinetic energy transfer. The less seal of the BB allows some of the compressed gas molecules to squeeze between the BB and the barrel and thus loosing those escaped gas molecule's kinetic energy to the atmosphere in front of the projectile instead of into the projectile from behind as momentum and inertia changes.

The energy difference is not much, but the cost savings and fun shooting shotgun patterns with the BBs outweighs the more expensive pellets unless you are doing sniper shots and what counts is the one shot one kill bar ammo expense.

Some mandatory math follows, so break out your 99 cent calculator:

As my rule of thumb: psi x π/4 x d^3 x Bbl"/12 = fpe (derived from 100% potential energy and a relative conservative efficiency of a stock higher end off the shelf air gun, in a perfect world)

As a physics law: sqrt(fpe x (671^2+1)/mgr) = fps

Note: A more exact constant for sea level at 45 degree latitude is the following: (2 x 9.80665 (g-exact by definition) / 0.3048 x 7,000), or 671.1457962^2

pi/4 (π/4) to 32 decimal places, gets the round area of the barrel, or bore along with squaring the diameter (d^2)

pounds per square inch (psi)

Barrel length in inches (Bbl")

Converting barrel length inches to feet (Bbl"/12) because there are 12 inches in a foot

Foot Pound Energy (fpe)

Feet per Second (fps); in addition, [fps x 0.3048 = m/s]

mass in grains (mgr) 'not manager', Case in point: there are 7,000 grains in 1 pound and they are neither medicinal nor recreational, but metallic such as lead (Pb)

square root of (sqrt(...))

Transfer Port Orifice Diameter (d) calculated at maximum at Caliber diameter (least efficient or shots per fill, but most Brute Power or Mach time!)

Caliber Diameter (d)

Efficiency value is given same as Caliber Diameter (d); efficiencies higher tend to blow out seals and cause premature parts wear and tear, but Wow! Anything less, you need to clean and tune your gun and match it with the magic projectile.

So, d x d x d = d^3 (Yes, that's where that came from and it only took me 55 years to normalize the caliber, transfer port orifice diameter and normal average efficiency to be represented by one variable as a quick rule of thumb to be later tweaked into custom values each, but a great start, give or take about 100 fps, and that's without even firing the gun and assuming that it is in goof working order with better than average economy ammo.); else, your guess is better than my calculated predicted value based on empirical tests for over 50 years.

If you are shooting with CO2 compressed gas, use my, or the following rule of thumb equation:

100 x π x e^(T in F / 71.8) = CO2 psi

Reverse engineering:

71.8 Ln(psi / (100 x π)) = T in F of the CO2

Temperature in Fahrenheit (T in F)
Carbon Dioxide (CO2)

Note: the wider range you try to calculate the CO2 pressure, the closer the "71.8" will move towards 71.2, but I find the 71.8 a better fit for CO2 shooting purposes around the 75 degree window +/- 5 degrees.

For example, I'm shooting a CO2 BB gun with a 24 inch barrel and the ambient temperature is 83.13400387 degrees Fahrenheit (only because some of you will check the math).

Lo-and-behold! The CO2 pressure just happens to be 1,000 psi! Coincidence? I think NOT! Its the equation that only took me 54 years to figure out.

Now plugging the variables into the said equation:

1,000 psi x π/4 x 0.177^3 x 24/12 = 8.710 431 628 fpe; rounded to 8.71 fpe (in a perfect world)

Next,

sqrt(8.71 x (671^2+1) / 5.14 gr BB) = 873.5 fps (in a perfect world)

sqrt(8.71 x (671^2+1) / 7.8 gr pellet) = 709.1 fps (in a perfect world)

A BBs BC is approximately 0.0160 and an average round nose pellet is approximately 0.0360 (for comparison purposes only. My disclaimer is: "In a perfect world")

The best velocity for accuracy and paper cutting power combination for Olympic style precision shooting is 567.89 +/- 10 fps in 0.177 wad-cutter pellet (indoors with almost no wind, not even an upwind fart). Above that, you start trading off accuracy/precision for power (maybe you might want to start cutting through heavier cardboard, I don't know).

At the other end of the spectrum, the best power and accuracy combination is around the 80% Mach velocity, which varies as the climate and location varies such as the time of day (noon vs. midnight can have a drastic change interpreted in over 100 foot elevation change and not even moving your position).

At standard temperature and pressure (STP) it is approximately 1116.45 fps (340.3 m/s), so 80% of that, if you are going to be shooting at sea level and freezing temperature, is 893.16 fps (272.2 m/s), so wear a thick insulated coat.

Note: keep in mind that a 1 degree error can give you approximately a 50 feet elevation error in Fahrenheit, and a 90 feet error in Celsius, so use an accurate thermometer, which means more expensive, or more than 99 cents.

The reason to stay below 80% Mach is because air resistance increases as the square of the velocity, and above 80% it starts creeping up to the cube of the velocity, and I won't even address going above Mach and back down past Mach.

Without more background information on your power plant gun, type of gas, ammunition, barrel length, transfer port orifice diameter, smooth vs rifled and choked bore, number of lands and grooves and depth of cut, it is difficult to cover exactly what your question asks, but it was a great start.

Maybe I read too much into your question and got carried away and should have just answered with a simple modern youngster cell phone text style response such as "Yes"? So, please excuse my liberty to respond to your question because I am a product of my parents forcing me to do my homework, every day, of the week, holidays not excluded, not even on my birthday. On one of my birthdays they gave me a pencil and paper pad to write down what I wanted for my next year's birthday and I wrote down "a beebee gun". What I got was a grammar book and a dictionary. The "A BB gun." came the following birthday and that was 56 years ago.

Lastly, BBs can outperform pellets any day if you sort, clean, weigh, measure for out of roundness by simply rolling them on a cutting board and keep the ones that roll straight down into a small neck bottle as your performance BBs and the rest as fun can killers; compared with just opening an average economy tin of pellets and picking them out of the tin at random. Precision is repeat-ability, accuracy is hitting the target. The worst hit in history is still far better than the best miss in history. Numbers don't lie, but you can lie with numbers. Do the math(s).