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 Author  Topic: MTB RONs, 7TH FLEET - Secret Information Bulletin
Joe Reese

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Joe Reese  Posted on: Aug 19, 2022 - 4:15pm
Hi all,

I tripped over this the other day, while surfing the archives, and thought you may find it interesting.

MTB RONs, 7TH FLEET - Secret Information Bulletin Report of MTB activities in southwest Pacific during closing months of 1943 to 1 March 1944

It goes into some of what they learned, what they found to work, what they experimented with, etc. I had no idea there was a boat sporting a stern-mounted 75mm.

https://catalog.archives.gov/id/77610509




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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: Aug 19, 2022 - 7:55pm
Wow Joe! This is pretty cool! I copied the text of the passage and posted it below. I wonder if there are any photos of PT336 that show the barrage rockets and the PT334 showing the 75mm gun mounted on her stern? Sounds like we have a new search request for the Forum! Jerry

pCGwM.jpg

Jerry Gilmartin
PT658 Crewman
Portland OR

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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: Aug 20, 2022 - 6:25am
I agree with Jerry, very cool and thank you Joe! And thanks for putting the text here Jerry. I checked my photos but I got nothing.

At 2/3 the weight, any ideas about why the 75mm didn't see at least some additional use on the PT's? I see it was only semi auto as opposed to the 40mm being full auto.


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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: Aug 20, 2022 - 9:22am
I found some info on the 75mm, there is supposedly a photo in Friedman's book but the poster on this thread, Bill Smallshaw, couldn't find it:
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?fid=102&cid=101&tid=2274&sc=20&pg=1&x=0

The post:
Freidman is a good source but there are a few inaccuracies in the book. For example one photograph has a caption stating that it shows a 75 mm recoiless rifle on a boat. I, for the life of me, do not see a 75 mm in the photograph.



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Joe Reese

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Joe Reese  Posted on: Aug 20, 2022 - 9:50am
I can't seem to find any other references to the 75 on a PT, or even that mount mentioned in the report. I will keep looking.

To take a layman's guess, I would have to go with rate of fire. There was mention of the bofors being enough to knock a mounted gun right off a barge, so I wonder if the Bofors' fire rate outweighed the 75's punch.

Jeff, I noticed you had a pic in the album of PT 131 with rockets on the deck. Are those the barrage rockets? I ask because one of the other war diaries I read, from the Mediterranean rons mentioned something to the effect of long range beach rockets(?). Unfortunately, I can't remember which document I read it in, but I wondered if they were the same as the barrage rockets, or more like the ones on 658.




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Joe Reese

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Joe Reese  Posted on: Aug 20, 2022 - 10:10am
I found it again. Bottom of pg 15 https://catalog.archives.gov/id/78345350

the "long range 5 inch beach rockets"

I'm not familiar enough with the rockets to tell if they're the same thing as on PT 131, or on the 658, or something else entirely.


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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: Aug 20, 2022 - 8:02pm
The 75MM M-4 as used on the B-25G, was heavy and slow firing, the later T13E1 was lighter and could sink a destroyer, but so could a squadron of B-25Js armed with as many as 14 .50 guns pointed forward. Below is a video of a B-25G with a 75mm on board, clumsy comes to mind! https://www.youtube.com/watch?v=cEek5IvGYKg


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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: Aug 21, 2022 - 1:40am
Yes it was not an auto cannon like the 37mm was. The USAF invented an auto loading 75mm called the T9E1 in time for use in Vietnam. During WW2, the only 75mm cannon available was the same M4 cannon used in B25 bombers. It was a breech loaded single shot cannon. The Wright Patterson USAF Museum has a T9E1 on display you can see on the internet. It looks pretty mean with the auto loading magazine on there! I dont know what they were thinking when they wrote that report!

Jerry Gilmartin
PT658 Crewman
Portland OR

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Joe Reese

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Joe Reese  Posted on: Aug 21, 2022 - 5:41pm
In my searching, I found this post from 2016, from this forum.

https://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?fid=102&cid=101&tid=4158&pg=35

Apparently, the Bofors rate of fire turned out to win the day.

Here's the Hyperwar link to At Close Quarters, for anyone who doesn't have it. I'm still trying to dig up some pics of it.

https://www.ibiblio.org/hyperwar/USN/CloseQuarters/index.html


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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: Aug 22, 2022 - 8:23am
Ahhh a classic Hollywood tale. The big but slow guy with a powerful punch getting whupped by the small fast guy! Nice video Stearman, the test shots were really rocking the B-25.

Jerry's boat has rocket launchers similar to these shown on this excellent site by researcher Tracy White: http://www.researcheratlarge.com/Ord/RocketLauncherMk49/

I never got into the rockets much and have forgotten much of the little I knew Joe. The PT 131 photo shows 4.5 inch beach barrage rockets in egg crate launchers, here's a closeup and text from a gentleman that knew about them:

pCpa7.jpg

pCjKJ.jpg



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