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 Author  Topic: Curved handle bars Oerlikon
Arjan Wiskerke

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Arjan Wiskerke  Posted on: Jul 18, 2019 - 2:06am
I'm in the process of adding the curved handle bars to the Oerlikon of my PT 515 model. I wonder when these curved handle bars were introduced on PT boats and whether or not this was originally a field modification.

I take it the handle bars were added to make elevation of the gun easier because the guns were mounted rather low on the deck. The trigger of the gun is not on the handle bars so it seems one hand had to be on the bars and one on the trigger which was located on the gun itself.

Not clear to me if the Oerlikon gun had a single shot option or whether the magazine was simply emptied automatically after having activated the trigger mechanism. Since there were no sights on this type of Oerlikon I take it the gun was more or less handled like a fire hose ?





Arjan


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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jul 18, 2019 - 4:00am
This should answer all your questions:

jVSj5.jpg



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Drew Cook

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Jul 18, 2019 - 4:38am
Another question re. the 20 mm Oerlikon...

Did the gun have an adjustable rate of fire? I've seen film of the gun in action on capital ships against Japanese aircraft, and the rate of fire is very rapid, like a machine gun.

I've also seen the gun in a very slow rate of fire, say in the movie "PT 109," and in single-fire mode in another movie ("Thunderbolt and Lightfoot").

I realize the movies are Hollywood fictions (well, fact-based, occasionally fictionalized, in the case of "PT 109"), but, did the Oerlikon have an adjustable rate of fire?


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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jul 18, 2019 - 4:45am
I believe the gun fired like the .50 cal, no selector switch for auto / single fire, it just fired as long as the trigger was pulled. And again like the .50, sights were available but often not used.

Interesting observation about the method of pulling the trigger when those curved grips were used, I have no clue. Nor do I have any clue about the contraption grips I posted above. :D

I don't think it had an adjustable rate of fire Drew.



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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jul 18, 2019 - 5:01am
This is the only image I found of a similar setup with the sight in use, on an Elco 80 in Norwegian service:

jf7dY.jpg

The sight:

jVz5S.jpg



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Arjan Wiskerke

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Arjan Wiskerke  Posted on: Jul 18, 2019 - 8:52am
Thanks so far gentlemen. I noticed that at least some of the Elco PT boats in the Med also had these curved handle bars but it appears the Higgins PT boats in the Med didn't have any fitted to their bow Oerlikon guns.

Regards,


Arjan


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Stearman

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Stearman  Posted on: Jul 21, 2019 - 3:10am
I just found out, the MK1 Oerlikon did have selective fire, semi and full. All other marks from the different country's were full auto only. As slow as they fired, one would think that a skilled gunner could quickly squeeze and release the trigger and only let off one round.


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Drew Cook

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Jul 21, 2019 - 8:27am
Thanks, Stearman,

It sure seemed so, from the films I mentioned. The 20 mms in those movies must've been Mark I models.


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  Jerry Gilmartin

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jerry Gilmartin   Send Email To Jerry Gilmartin Posted on: Jul 21, 2019 - 2:34pm
I looked in the 20mm Manual found on the HNSA website. It discusses the different Marks. 1,2 and 4
"The Mark 1 Gun was the original type made in Switzerland. The Mark 2 is the improved version made in England and also being made in U. S. A. The Mark 4 Gun is almost identical with Mark 2 except for slightly different manufacturing limits. Both Marks 2 and 4 Guns will be found in service in the U. S. Navy, but eventually only the Mark 4 will be manufactured in this country."
So from this I came to the conclusion that the 20mm cannons used on the PT Boats could not have been Mark 1. I also know that Mark 2 and Mark 4 have only Fire and Safe Positions on their Selector Switches. No Single Fire is possible in this API type cannon. The listed Rate of Fire is 450 rounds per minute.(about 7 rounds/second!) I imagine it can be slower than that but I don't know how you could control single shots, and don't think it possible.

To look for yourself; go to the HNSA Website, https://www.hnsa.org/manuals-documents/ordnance-gunnery-and-fire-control/ 20 MM Antiaircraft Gun, OP 911, 1943, is a Navy service manual for the anti-aircraft gun of choice during the early years of WW II.

Also a movie of a 20mm being shot recently at Stone Mountain Georgia https://www.youtube.com/watch?v=DC4mdAoRfK8&t=44s


Jerry Gilmartin
PT658 Crewman
Portland OR

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Arjan Wiskerke

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Arjan Wiskerke  Posted on: Jul 21, 2019 - 11:55pm
Thanks gentlemen ! Interesting footage Jerry, this clearly shows that the gun is mounted so low that sights are of no use when the gun is elevated beyond a certain angle (perhaps sitting on your bum would get you low enough to use the standard sights) .Interestingly this pic shows that the Oerlikon on PT 620 didn't have any sights but it did have both the standard shoulder rests and the curved handle bars :




Regards,

Arjan


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