Best synchronizable heavy machine gun of the war?

• Aug 7, 2020

• #61

P-39 Expert

Non-Expert

1,810

605

Mar 12, 2018

Heath, TX

Excellent information, thank you for all your hard work.

Appears from these charts that there is hardly any penalty for synchronization. At 3000rpm for a three blade prop the first chart reflects a 16% reduction, the second reflects a 10% reduction and the third chart reflects only a 4% reduction in ROF.

Still seems low to me compared to other tests but those tests were on other synchronized planes.

Again, this is an excellent presentation of professional quality. Thanks.

 

• Aug 7, 2020

• #62

bruno_bis

Airman

17

4

Aug 3, 2020

You are welcome!

 

• Aug 7, 2020

• #63

bruno_bis

Airman

17

4

Aug 3, 2020

Just another comment on the "P39 Q case":

P39 "in general" is a nice example at showing the concept of "favoureable" layout of the gun. Muzzle is very close to the propeller and the offset of its line of fire with respect to the propellel axis is small. Moreover the width of the propeller blade is small at its intersection with the line of fire. This minimizes the time the blade takes to cross the line of fire, thus helping to arrange a feasible solution for a four-bladed propeller.
On the other side, engine to propeller speed reduction gear is high. At least the one adopted in P39 Q. Other fighters featured lower reductions. Since, for the same engine speed, "the greater the speed reduction -> the lower triggering pulse frequency", the sawtooth drops at critical speeds are deeper and this effect is, in absolute values, greater for guns featuring higher free rates of fire.

 

• Aug 8, 2020

• #64

A

Admiral Beez

Major

9,358

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Oct 21, 2019

Toronto, Canada

P-39 Expert said:

The only AAF fighter with synchronized guns used in quantity was the P-39 and it had both three and four blade props. Big brother P-63 had four blade prop.

Click to expand...

Didn't the Curtis P-40 have two cowl mounted .50 cal?

 

Last edited: Aug 9, 2020

• Aug 8, 2020

• #65

Clayton Magnet

Staff Sergeant

903

917

Feb 16, 2013

P-36 as well.
Didn't A-36's have .50's mounted UNDER the nose?

 

• Aug 8, 2020

• #66

S

Shortround6

Major General

23,201

16,394

Jun 29, 2009

Central Florida Highlands

I guess it depends on what is meant by quantity.
P-39s. around 9550 give or take.
P-36s (with one .50 cal gun) about 215.
P-40s (and Tomahawks) with cowl guns around 1600-1750 ?

AAF had about 470 P-40s with cowl guns of four types types, the rest were exported

 

• Aug 9, 2020

• #67

A

Admiral Beez

Major

9,358

10,677

Oct 21, 2019

Toronto, Canada

Clayton Magnet said:

P-36 as well.
Didn't A-36's have .50's mounted UNDER the nose?

Click to expand...

Not a fighter, nor AAF of course, but if P-39 Expert can indulge us I'd include the Douglas SBD with its two syncronized .50 cal. firing through the propeller. Used with great success against IJN fighters - one SBD pilot, Swede Vejtasa shot down three A6M Zeros in a single engagement.



Then there's the 17 USN/USMC squadrons operating the Brewster Buffalo with its cowl mounted twin .50 cal. But again, not AAF. My point is that at the beginning of their war, the US certainly embraced synchronized, firing through-prop machine guns in all branches of the military. The primary fighters of all branches of the US military (AAF, USN and USMC) each had them, as did the USN's dive bomber (SBD) and torpedo bomber (TBD).

 

Last edited: Aug 9, 2020

• Aug 9, 2020

• #68

A

Admiral Beez

Major

9,358

10,677

Oct 21, 2019

Toronto, Canada

When the Brits received their Brewster Buffaloes I've read they replaced the .50 guns with .303 guns. Did this include the cowl mounted guns? I wouldn't think the synchronization gear would be compatible, nor easy to adapt in an under-served outpost.