OPC “Placemat,” Notice planned delivery has slipped considerably from 2021 to 2023.
Naval News and writer Peter Ong bring us an update on the status of the Offshore Patrol Cutter Program.
I did not see any particular surprises, but there may be a hint of how the 30mm Mk38 Mod4 is viewed in this question and answer.
Naval News: Will the Mark 38 MOD2 be changed out now that the US Navy is planning for Mark 38 MOD4s with 30mm?
Brian Olexy: The OPC program includes each cutter receiving one MK 38 MOD 3 with 7.62 mm co-axial gun. There is no plan at this time to change to a MK 38 MOD 4d for UAS operations. (emphasis applied–Chuck)
My immediate reaction was–what did the gun have to do with UAS operations? There was nothing about UAS in the question. Then I recognized a possible connection. The 30mm has a demonstrated counter-UAS capability using air burst ammunition that the 25mm does not have. The response may reflect the author’s comments that were not recounted in the post, or it may be that the Coast Guard has recognized the use of the 30mm as a counter UAS weapon.
UPDATE: I was contacted by the author and informed that an error had occurred in the publication of his story and that the correct quotation included no reference to UAS. It should have read.
7. Will the Mark 38 MOD2 be changed out now that the US Navy is planning for Mark 38 MOD4s with 30mm?
A. The OPC program includes each cutter receiving one MK 38 MOD 3 with 7.62 mm co-axial gun. There is no plan at this time to change to a MK 38 MOD 4.
Chuck Hill's CG Blog 
Actually they do, the Orbital ATK 25 CDTE (Counter Defilade Target Engagement) ammunition. Originally meant for the XM25 25x40mm Punisher Grenade Launcher, refitted to an 137mm shell casing…
@Secundius, do you have a link to information about this new round and its adaptation to our gun?
It’s dated for 2012, so I can’t be sure if it’s still active! But Orbital ATK produced the 25mm CDTE round, whereas HK the other contractor was developing the 40mm propellant cartridge.
Just in case the linksite address fails, the publication is called:
“General Dynamics Ordnance and Tactical Systems: Next Generation Fuzing for Next Generation Weapons, Medium Caliber Ammunition Scalable Airburst Fuze”, by David A. Andersen…
( https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2012/fuse/13938Anderson.pdf )
Nexter of France is also producing an Air Burst 25x137mm round, the 25x137mm HEI-AB. Item number 154 (NOT Page Number)…
( https://www.nexter-group.fr/sites/default/files/2020-05/20180604%20Nexter%20-%20Catalogue%20Ammunition.pdf )
@ Secunidius, the link did not work for me. Attempts to find reference for a 25x137mm air burst round also failed. Since these dates back to 2012 it appears the airburst round never went into full production.
“Naval News”, says a 7.62×51 Nato co-axial with be side mounted on the OPC’s Mk.38 Mod.3…
( https://www.navalnews.com/naval-news/2022/01/u-s-coast-guard-provides-information-on-the-offshore-patrol-cutter/ )
@Secundius, found the Nexter HEI-AB round. We would still need a modification to the gun mount that would find predicted time to intercept and feed info to the round to use it. Not impossible, but not done yet to my knowledge, and doubt if the round is currently in USN system.
It’s fair to say that if Nexter of France is producing them, then so is the United States. Unless you actually believe in a Single Manufacturing Supply Source for ammunition is a good idea…
“It’s fair to say that if Nexter of France is producing them, then so is the United States.”
You can’t make that assumption. You also cannot assume that if ammunition is being produced that it will be in every allied nation’s arsenal or that all weapons will be adapted to use it.
Nammo of the Netherlands also produces the 25x137mm HEI-AB, and also have a manufacturing facility in Mesa, Arizona called Nammo Defense System which produces Military Ammunition…
@Secundius, you seem to be getting closer, but still not apparent that a 25x137mm air burst round is in the Navy’s ammunition system or that the 25mm Mk38 can use it. Would be encouraging if you could find that.
The USCG is arming the OPC with something, but not with either the Mk.15 CiWS or the Mk.38 Mod.4. So I guess we’ll have to be patient a little longer to find out…
@Secundius, “The USCG is arming the OPC with something, but not with either the Mk.15 CiWS or the Mk.38 Mod.4. So I guess we’ll have to be patient a little longer to find out…”
As of now it is a 57mm Mk110, a 25mm Mk38 Mod3, a pair of .50 caliber in remote weapon stations, and some crew served .50 cal. Have you seen indication of something else?
Didn’t the USCG mention something last month about coaxialing the Mk.38 Mod.3 with a 12.7x99mm machine gun, or was that the USN…
The arc of fire for that single 25mm Mk38 Mod3 gun is limiting. It’s mounted high, over the hangar, which is fine, but then has those 2 satcom antennas on either side. Someone needs to consider moving them or placing 2 Mk38s P/S or mounting an additional one forward on the level below the bridge.
Got an email from the author who said there was an error in publication:
I added an update to the post to reflect this.
OPC ‘sustained’ speed is 17 knots with a 22.5 knot max? Is that the ‘sprint’ speed? SMH. I always felt it should be able to sustain 20 and sprint to 25 or 26. But that’s just me.
That’s about the cruising speed of a Panamax Container Ship (i.e. 16.5kts) that the OPC are likely to Escort Convoy if and/or need to…
The US Navy’s amphibious ships tend to max out at about 22 knots and their underway replenishment ships at about 20. The OPCs if properly upgraded, might have a role escorting them.
But what is the LAW likely to be…
As far as I know, it’s the way the hull was designed for a maximum speed of ~22kts. Even if and I’m saying a big IF you were able to fit the Wartsila RT-flex96-C Marine Diesel at ~114,800-bhpinto it, it’s not likely to go any faster by one or two knots…
17 knots is a high cruise speed, probably doable without much strain, using only one engine (7,280 kW or 9,760 hp available on only one engine). Sustained speed is 22.5 knots. That probably means at 80% of the engines rated horsepower and probably in the most adverse conditions of load, trim, and environment.
Power requirements vs speed for the OPCs is going to be similar to that of the 378s. Also keep in mind that as a rule of thumb, provided they are otherwise the same, you need to double the horsepower output to add four knots speed.
For comparison, on a 378, we used to cruise on one shaft and one diesel engine freewheeling the second shaft. The 378s only had a total of 7,000 HP on two diesels. On 3,500 HP or a bit less we were able to make 11.5 knots.
Using diesels both shafts for 7,000 HP a 378 could do 19 knots. Using one turbine on one shaft and freewheeling the other, we could make about 22 knots on 18,000 HP, but that was in an inefficient configuration dragging a shaft and requiring a slight rudder offset to maintain a straight course. On two shafts we could make 28/29 knots on 36,000HP.
The OPCs can develop 54% of the max HP of the 378s but claim a max speed 6.5 knots lower.
To look at it another way, the 270s have the same HP as the 378s on diesels and they produce a similar speed, 19.5 vs 19 for the much larger 378s. Doubling the available HP to 14,000, would likely result in a speed of 23.5 knots.
I have always thought the reported maximum speed for the NSCs and OPCs have been conservative. Looking at other ships with similar power available, I think, under all but the most adverse conditions, the OPCs should be able to do 24 knots or perhaps slightly more.
The minimum max speed for the Light Amphibious Warship (LAW) will be 14 knots. They would prefer 15.
The Fairbanks-Morse are licensed copies of the German-made MAN 16V 28/33D Marine Diesels which were designed for Long-Range at lower revolutions, NOT speed. If the USCG wanted Faster Speed at the instead of range, they should have chosen the MTU Marine Diesel…
19,520 HP is 19,520 HP no matter what engine it comes from and doubling that to 39,040 if properly geared and given a propeller of the proper diameter and pitch would increase speed by about four knots.
Probably true, but the USCG chose the speed range gearing for the OPC for a reason, unless the diameter of the ship’s screws variable speed without any gearing through an electric motor…
For sake of logistics, and considering that they’re almost the same hp, I would have stuck with the MTU diesels. After all they’ve got MTUs in the FRC and NSC.
There is an important concept here: https://chuckhillscgblog.net/2017/07/10/hull-speed-maximum-cruise/
Vards 115 and 125 based on OPC quote 23 knots. Their original concept for OPC goes without the electric motors, uses the 20V engines and quotes speed of 24.5.
@Andy, the Wikipedia entry for the Heritage class cutters (https://en.wikipedia.org/wiki/Heritage-class_cutter) which seems to be correct in all other respects lists the speed as 24.5 knots.
“Naval News” dated 13 January 2022, “U.S. Coast Guard Provides Information On The Offshore Patrol Cutter”…
( https://www.navalnews.com/naval-news/2022/01/u-s-coast-guard-provides-information-on-the-offshore-patrol-cutter/ )
@Secundius, you know that is the article that is the original basis for this post.
Actually NO, because your article came to me as part of the Disqus Great Discussions Comment Site and not directly from you as a “follower” to your WordPress blog site! My comments were based on what I knew of the OPC up to and including at the time you posted it. My bad then…
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