Silly Me Post About Tracer Vs Non Tracer.

[earl1937]

Tested 50 cal offline with the target.

P51D
Conv - 300
Alt 1000ft
Level speed 301 ias
Target 300 yards

Tracers on - Concentrated dispersion 5ftx5ft with random dispersion 10ftx10ft at 300 yards.
Tracers off - Concentrated dispersion 5ftx5ft with random dispersion 10ftx10ft at 300 yards.

The IP point was exactly the same relative to the gunsight center and target in both cases with the same 5Mil nose down movement during firing. I suspect that 5Mil nose down depression might have some influence to player complaints. This can be seen with fighters that have wing guns outboard of the main gear with the offline target while shooting on full zoom. "For every action, an opposite and equal reaction".

A case could be made for testing convergence combinations at target 200, 300, 400 to present dispersion clouds as a player aid. The AAF 1945 armorers harmonization manual had graphic illustrations of this for the P51D set to 333yd conv. The assumption for the 50cal and 20mm was an ever expanding 4Mil dispersion cone along the ballistic arc at all ranges out to max effective. The famous "Shotgun Effect".

Thanks for your report sir and I will not reduce my converg to 300 instead of the 400 I have been using with the .50 cal aircraft!

[bustr]

Just for fun...

Random dispersion is often more important on long distance shots and snap shots. "Shotgun Effect". Or the 4Mil dispersion cone at range describing your random round position at any point in time.

P51D
301 ias
1000ft auto level

x = feet
(x) = High density impact pattern cloud blob.
(x)x(x) = Impact cloud blobs with space between pattern high density impact blobs or random dispersion blobs.
RandomDispr = low density impact ring of random flyers.

----------------------------Pattern at Target Range(yards)
Convergence-----200-------300---------400-----------------600 Target Range
250-275-300-----(10x5)-----(5x5)-----(5x5)3(5x5)-----(10x10)10(10x10)
RandomDisper---(12x9)----(15x10)------(20x10)-------------(40x20)

300-275-300-----(10x5)-----(5x5)-----(5x5)3(5x5)-----(10x5)10(10x5)
RandomDisper---(12x10)---(10x10)-----(20x15)-------------(45x20)

Convergence--------200---------300----------400-------------600 Target Range
300-300-300-----(5x5)3(5x5)-----(5x5)-----(5x5)3(5x5)-----(5x5)10(5x5)
RandomDisper------(15x10)------(10x10)-----(20x15)-----------(40x20)

350-375-400-----(5x3)5(5x3)------(8x3)-------(8x4)-----------6x5)5(6x5)
RandomDisper------(15x10)------(10x10)-----(15x15)-----------(25x35)

300-400-500-----(2x5)5(2x5)-----(10x4)-------(8x8)------------(10x10)
RandomDis----(10x10)5(10x10)--(12x10)-----(15x10)----------(20x10)

[muzik]

If I were making the ammo as a manufacturer, I'm pretty sure I would have tested and modified the amount of "powder" in the tracer rounds to make up for it as much as possible...

"...until I found out that I couldn't make various types of rounds with different components, with different weights, the exact same size and ballistics because the laws of physics stubbornly refuse to bend to my will."

You're suggesting they changed the length of the tracer round with that theory. I've never seen an ammunition belt that looked like an EKG chart.

If the two didn't fly the same path, what would be the point?

Because they believed it was better for accuracy than nothing at all.

(Those clever fellas back in the science lads figured out a way to get those pesky tracer rounds to fly the same path as the ball, the ap, the api, etc. That's why you have different types of tracer. They weigh the same with whatever they're belted with.)

Not so clever of a theory.

I doubt the people who designed the rounds know less than you do or that they sent guys to war with tracers that nowhere near where the rest of the bullets are going.

"THEY" didn't send anyone to war, the US military did. You seriously overestimate Uncle Sam's record for "quality in the field."

No one said they were nowhere near, they said "not the same." Tracers were not as accurate or as effective as ball or AP.

quote author=nrshida link=topic=351311.msg4645336#msg4645336 date=1374216506]
I'd have thought the solution is obvious - make every round a tracer. There might be a benefit to a mass-diminishing round as the velocity reduces 
[/quote]

Sarcasm I trust.

[icepac]

"...until I found out that I couldn't make various types of rounds with different components, with different weights, the exact same size and ballistics because the laws of physics stubbornly refuse to bend to my will."

You're suggesting they changed the length of the tracer round with that theory. I've never seen an ammunition belt that looked like an EKG chart.


Because they believed it was better for accuracy than nothing at all.

Not so clever of a theory.


"THEY" didn't send anyone to war, the US military did. You seriously overestimate Uncle Sam's record for "quality in the field."

No one said they were nowhere near, they said "not the same." Tracers were not as accurate or as effective as ball or AP.

quote author=nrshida link=topic=351311.msg4645336#msg4645336 date=1374216506]
I'd have thought the solution is obvious - make every round a tracer. There might be a benefit to a mass-diminishing round as the velocity reduces 


Sarcasm I trust.

The tracer rounds weighed more than the ball or HE rounds.

They were not shorter or longer but comprised of varying amounts of a few compounds to arrive at the different weights.

As far as how they fly, I am relaying my dad's experience in shooting thousands of rounds from a real plane in real combat conditions.

[Wiley]

"...until I found out that I couldn't make various types of rounds with different components, with different weights, the exact same size and ballistics because the laws of physics stubbornly refuse to bend to my will."

You're suggesting they changed the length of the tracer round with that theory. I've never seen an ammunition belt that looked like an EKG chart.


Because they believed it was better for accuracy than nothing at all.

Not so clever of a theory.


"THEY" didn't send anyone to war, the US military did. You seriously overestimate Uncle Sam's record for "quality in the field."

No one said they were nowhere near, they said "not the same." Tracers were not as accurate or as effective as ball or AP.

Muzik has the right of it here.  We're not talking about sniper level accuracy, we're talking about mass produced military ammunition in the 1940s.

Just for grins I ran the ballistics through a calculator for .50 API, Ball, and M1 Tracer using values from a quick google.  Unfortunately I couldn't find a ballistic coefficient or bullet weight for the Tracer, but the MV was around 300fps slower than the API or ball.

Ball- Ballistic Coefficient 0.67 weight 647 gr  muzzle velocity 2930
API- Ballistic Coefficient 0.65 weight 622.5 gr  muzzle velocity 3050
Tracer- Ballistic Coefficient 0.65 weight 643 gr  muzzle velocity 2700

The tracer bullet weight is fudged a bit because the only weight I could find for it was an overall round weight.  It was 21 grains heavier than the API on that chart, so that's what I went with.  I just threw in the API ballistic coefficient because I'd expect it to be more similar to that than ball.

At 600 yards, bullet drop was as follows:
Ball- 70 inches
API- 64.3 inches
Tracer- 83.1 inches

Difference: 18.8 inches

At 300 yards, it was:
Ball- 10.9 inches
API- 9.8 inches
Tracer- 13.1 inches

Difference: 3.3 inches

On vehicle size targets and given all the other variables, the differences are well within normal dispersion.  Tailgunning at long ranges, I could see knowing the tracers have a slightly different flight path being a benefit, but when it comes to forward firing MG's on aircraft at typical gunnery ranges, it's just not that huge of a factor.

Wiley.

[Blooz]

Muzik has the right of it here.  We're not talking about sniper level accuracy, we're talking about mass produced military ammunition in the 1940s.

Just for grins I ran the ballistics through a calculator for .50 API, Ball, and M1 Tracer using values from a quick google.  Unfortunately I couldn't find a ballistic coefficient or bullet weight for the Tracer, but the MV was around 300fps slower than the API or ball.

Ball- Ballistic Coefficient 0.67 weight 647 gr  muzzle velocity 2930
API- Ballistic Coefficient 0.65 weight 622.5 gr  muzzle velocity 3050
Tracer- Ballistic Coefficient 0.65 weight 643 gr  muzzle velocity 2700

The tracer bullet weight is fudged a bit because the only weight I could find for it was an overall round weight.  It was 21 grains heavier than the API on that chart, so that's what I went with.  I just threw in the API ballistic coefficient because I'd expect it to be more similar to that than ball.

At 600 yards, bullet drop was as follows:
Ball- 70 inches
API- 64.3 inches
Tracer- 83.1 inches

Difference: 18.8 inches

At 300 yards, it was:
Ball- 10.9 inches
API- 9.8 inches
Tracer- 13.1 inches

Difference: 3.3 inches

On vehicle size targets and given all the other variables, the differences are well within normal dispersion.  Tailgunning at long ranges, I could see knowing the tracers have a slightly different flight path being a benefit, but when it comes to forward firing MG's on aircraft at typical gunnery ranges, it's just not that huge of a factor.

Wiley.

So, why not run the numbers with the proper tracer rounds?

M20 is the API-T and M21 is the air combat load tracer round.

[Wiley]

The tracer I was using was the stats for the M1 tracer.

I don't seem to be able to find a bullet weight, muzzle velocity, or BC for the M21.  The M20 drops the same as the M8 API.

Really, it's a mountain out of a molehill.

Wiley.

[bustr]

From the 1945 manual of the Browning .50 cal fixed and aircraft.

Testing with 36in bbl.

M2 AP 2840fps 1.38sec to 1000yds. Elevation 35. round weight = .26lb

M8 API 2950fps 1.40sec to 1000yds. Elevation 30. Round weight = .26lb

M20 APIT 2950fps 1.40 to 1000yds. Elevation 30. Round weight = .26lb
Dim trace to 300 and bright trace to 1750.

M1 TR 2900fps 1.366sec to 1000yds. Elevation 35. Round weight = .25lb.
Traces to 1800yds.
(M1 Limited to use in ground machineguns in the continental U.S. and training. )

M10 TR 2900fps 1.366sec to 1000yds. Elevation 35. Round weight = .25lb.
Dim trace to 150, bright to 1900.

M17 TR 2900fps 1.366sec to 1000yds. Elevation 35. Round weight = .25lb.
Traces to 2450yds.

From the 1942 manual of the Browning .50 cal fixed and aircraft.

Testing with 36in bbl.

M2 AP  2900fps
M1 TR  2830fps
M1 I    2830fps

From AAF 1945 Gun Harmonizing Manual tables, all AAF fighters.

ANM2 Aircraft, Basic

M2 AP  2700fps
M8 API 2870fps

[muzik]

The tracer rounds weighed more than the ball or HE rounds.

Probably because the tracer charge weighed more than the gun powder. Not sure what the differences in lead or shell size were.

They were not shorter or longer

Because????  ...You cannot put different size rounds in the same MG belt!!

comprised of varying amounts of a few compounds to arrive at the different weights.

Exactly. You cannot make two shells the same size and weight but with different materials unless the components in both shells JUST SO HAPPENED to have the same weights.

They did not have a tracer charge that also worked as a propellant to make up for the displaced gun powder. Less powder, less projectile range. To make that projectile go the same distance as other rounds you would have to add more powder. More powder means longer rounds, more brass. Now you have short ball rounds and long tracer rounds.

If they could have made the various rounds perform the same and be the same size they would have.

They couldn't and they knew it so they compromised. They traded a little accuracy and hitting power for what they assumed was better shooting ability for inexperienced or less talented shooters. And if that turned out to be the case most of the time, then it was a good trade off.

As far as how they fly, I am relaying my dad's experience in shooting thousands of rounds from a real plane in real combat conditions.

Sorry, I don't know your dads experience. But with all due respect to his service and experience, science has come a LONG way since the 40s. Many people go their whole lives believing everything they learned even after new research proves old beliefs wrong.

Not all of what people or servicemen were taught was accurate in retrospect. Plus, people forget or fail to consider other explanations for what they see.

For example, if your dad did mostly ground attack where the guns are pointed downward, the "flat trajectory" he experienced may be simply explained by the fact that a tracer traveling at a downward angle is not going to drop as dramatically as one fired straight out. Gravity assisted energy retention.

If he fired on aircraft in a downward manner, same principle.

[Charge]

The projectile size can vary provided that while a longer projectile is further inside the casing there is still room for correct amount of powder. If there isn't, it will result even in drastically smaller MV or even feed failures if the gun is of blow-back type -as e.g. MG-FF. But that also depends on how much filling there is in the first place and what kind of powder is used (burn velocity). If the casing is already full with powder and a longer projectile needs to be inserted lower MV needs to be accepted or the powder changed to faster burning type, provided it is available and that the gun can stand it.

Compare e.g. MG151/20 AP and MG where the projectile size is vastly different. The MG is inserted just further inside the casing.

The ammunition in belt have to be near same length, of course, or else there is a possibility of feed error. Some gun configurations are more prone to jam if the ammo is even slightly longer that that allowed but that also depends on the feed system and how much recess there is in the barrel mouth to insert the projectile. I'm not sure if any gun system or feed system will not accept a round that has the projectile inserted slightly too deep inside the casing.

-C+

[bustr]

The rounds in question from WW2.

M1 T
M2 AP
M8 API
M20 APIT

These .50 cal cartridge had to meet an OAL of 5.45in to be fired from all  browning .50 cal used by US forces in WW2. What differed was the length and cross section of the bullet between types and the powder used in response.

Tracer only rounds were flat bottom Spitzer along with the M2 AP. M8 API and M20 APIT were boat tail. From the crimp band to the ogive tip, the length was the same. Not from the crimp band aft. Flat bottom spritzer did not have the same long distance stability as boat tail.

M1 T --- Bullet OAL = 2.40
M2 AP -- Bullet OAL = 2.40
M8 API ---- Bullet OAL = 2.31
M20 APIT - Bullet OAL = 2.31

Different powders were shaped differently allowing looser or tighter packing. Or their chemical composition allowed less to be used to achieve the required pressure for the InitV.

Inside of 2000ft(666yd) the ballistic differences between tracer and AP rounds is meaningless to the expected 4Mil dispersion circle or 8ft. AAF testing showed past 2000ft, fighter gunnery was not effective in air combat between moving aircraft to make shooting worthwhile. At 3000ft(1000yd) your 4Mil dispersion circle becomes 12ft or probably worse in reality. Even the crew gunners handbook for the AAF\Navy tells gunners to wait for 600 yards.