MK103M Question

[N.Ishigaki]

The motorkanon type of MK103, “MK103M” delayed the development and could not enter production. Therefore Bf109s and Ta152s never carried MK103 as the motorkanon.

I wonder why MK103M took so long time for the development, and what the difference between MK103 and MK103M. When googled, I found game BBS postings saying MK103M had modified gas duct and no muzzle brake, but I couldn’t find books or documents supporting the postings. Also, I wonder such modification, not affecting the canon mechanism itself, need so long time.

[Nick Beale]

This book might help you: http://users.telenet.be/Emmanuel.Gustin/volume1/index.html

The author has a site devoted to cannon: http://www.quarryhs.co.uk/

[Broncazonk]

The MK 103 was introduced into service in 1943, well before the Do 335 or Ta 152.

The wing mounted MK 103 cannon was quite heavy, slow, and extremely inaccurate. And the recoil forces were enormous (2,000 kg per round with a muzzle brake {wing mounted} and 3,000 kg without {motor mounted}) which put significant stress (and movement) on the wings and mounts.

The motor mounted MK 103 cannon was just as heavy, just as slow (65-rounds/minute) and inherently inaccurate. (The motor mount didn't help the accuracy one bit.) "With a firing probability of 95%, it was calculated that 76 rounds would have to be fired from a range of 500 meters to achieve three hits on target. This figure rose to 203 rounds from 1,000 meters and 650 rounds from 1,500 meters." Dornier Do 335 by Karl-Heinz Regnat (Schiffer 2003)

A minimum of 76 rounds to get 3 rounds on target at 500 meters (95% of the time) is absolutely appalling inaccuracy. A fighter carrying the Mk 103 literally couldn't carry enough 30mm ammunition to get the job done.

Bronc

[N.Ishigaki]

Thank you very much, for your reply.

Nick, I just ordered the book. Fortunately, Amazon Japan had a stock.

Bronc, your information is so interesting. Rheinmetall-Borsig might not delayed the MK103M development, but might postponed in order to focus on MK108 development, I suppose. (Just an imagination!)

[Broncazonk]

The MK 103M ("M" for motor mounted) was not delayed. It was too heavy, too slow, and they could never make it accurate. The Me 109 was too small to utilize a Mk 103M. The weapon was too long and heavy to install it in that aircraft.

The Mauser Mk 213 {typo corrected: formerly "Mk 214"} revolver cannon was the answer to the Luftwaffe's desperate plea, but it came far too late to enter service.

Bronc

[Kutscha]

Depending on what ammo was used, the MK103 had a rate of fire from 380 to 420 r/m, not 65 r/m.

The MK214 was a 50mm weapon and certainly larger and heavier than the MK103. Did you mean the MG213?

Here is a web site on the MK103, http://www.deutscheluftwaffe.de/archiv/Dokumente/ABC/m/MK%20103/MK%20103%20Maschinenkanone.htm

[Broncazonk]

Thank you, Kutscha. I was indeed referring to the Mauser Mk 213.

As to the rate of fire, I double-checked the 65 r/m (as opposed to the oft cited 380 to 420 r/m) as I was utterly shocked by that very low/slow number.

My reference is: Dornier Do 335 by Karl-Heinz Regnat (Schiffer 2003) page 132.

The data is reproduced from the (original) Dornier Do 335 technical description manual pertaining to the Mk 103, to wit:

"One MK 103 in Mol 103/1A engine mount in forward engine, firing through the hollow propeller shaft. Rate of fire: sixty-five rounds per minute."

Shocking indeed.

The Do 335 only carried 70 rounds (possibly 65 rounds) (between Frames 1 and 2) for the MK 103. Unregulated the MK 103 would run at 380 r/m when firing HE/AP tracer, and at 420 r/m when firing Mine shells. 70 rounds at 380 r/m will give you 11-seconds of trigger time. 70 rounds at 420 r/m will give you 10-seconds. Factoring in the inherent inaccuracy of the weapon: "With a firing probability of 95%, it was calculated that 76 rounds would have to be fired from a range of 500 meters to achieve three hits on target. This figure rose to 203 rounds from 1,000 meters and 650 rounds from 1,500 meters," it was statistically impossible to hit anything at 380/420 r/m outside of 500 meters.

If I'm not mistaken, the Luftwaffe regulated the MK 103's rate of fire down to 65 r/m to improve it's statistical ability (not actual ability) to put rounds on target.

Bronc