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 Author  Topic: .50 Cal. Mount Manual OP 893
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: Mar 5, 2014 - 5:54am
The hnsa site has the Mod. 1 & 2 version of this manual (Ordnance Pamphlet) (http://www.hnsa.org/doc/pt/fifty/index.htm), OP 951. Does anyone have access to the earlier manual for the Mark 17 mount, OP 893? I'm trying to find more information on the hand brake setup. The hnsa manual mentions a new style brake along with The heavy brake ring has been eliminated , and the brake shoe of the new brake operates against the outside of the fixed ring.. I was wondering if the protective shield around the base of the mount, above the top of the turret, seen on the earlier boats might have also functioned as the heavy brake ring.

Based on photographs, the protective shield appears to have went through a modification.
Early boats of the PT 103 class show a straight walled protective shield.
Boats starting somewhere between PT 118-139 seem to have a radius at the bottom.
Boats starting somewhere between PT 317-323 do not have the protective shield.
Higgins boats lost the shield somewhere between PT 215-237.

I looked up the title of the manual as well as another mentioned in the hnsa manual:
OP 893 - 0.50 Inch Mount Mk 17 Mod 0 Description, October 1942
SNL A-36 (OP 716) - Gun, machine, cal. .50, Browning, M2, water-cooled, fixed (Navy); and aircraft, basic (for Navy use only)
Issued with SNL A-36: OTI GV35-43 - Maintenance of Maximum Belt Lifting Capacity in Browning Aircraft Machine Guns Cal .30 and .50 M-2, 18 November 1943

Hand brake photos (early type are really hard to find) I have available show a spherical end on the handle up to PT 149. Later handles are a metal loop as seen in the hnsa manual.

Any help would be appreciated.



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Higgins Fan

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Higgins Fan   Send Email To Higgins Fan Posted on: Mar 6, 2014 - 11:29am
Have you contacted Harland at North American Restorations? He might be able to help.

--
National WWII Museum
PT-305 Restoration
Phone: 504-528-1944 Extension 375

Total Posts: 128 | Joined: Aug 17, 2012 - 7:48pm | IP Logged

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: Mar 8, 2014 - 4:18am
Thanks HF, I might give him a try. Images of his mount reproduction work sure helped a lot.



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