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Mark I Upgrades For Std Velocity Ammo Reliability

This is a discussion on Mark I Upgrades For Std Velocity Ammo Reliability within the Gunsmithing forums, part of the Firearm Forum category; Getting into handgunning after years of shooting rimfire benchrest. I have cases of std velocity (subsonic) match ammo from Eley and Lapua. I figured I ...


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Old March 3rd, 2017, 03:21 PM   #1
 
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Mark I Upgrades For Std Velocity Ammo Reliability

Getting into handgunning after years of shooting rimfire benchrest. I have cases of std velocity (subsonic) match ammo from Eley and Lapua. I figured I would be able to shoot them in my 1980 Clark customized Mark I. When I tried shooting the match ammo I got FTE and stove pipes about every 2-3 shots. I also noticed that the firing pin strikes were shallow and at the very edge of the rim, deforming the cases.

First I changed out the firing pin and the extractor with parts from Tamdenkross. The extractor was a great upgrade but their titanium firing pin, while working, had an even shallower strike, also on the very outer part of the rim. After installing these parts, I was still having problems with FTE and stove piping, even when shooting the higher velocity Remington Golden bullets I had on hand (had them for probably 20 years.)

So, I saw on the SGW site that they had Ruger's new OEM firing pin that is a machined rather than stamped part and that has an improved tip shape. They also had the Volquartsen recoil rod spring assembly with extra springs that are lighter and heavier than the Ruger OEM spring. I figured these parts might be the solution to my problems. They came in today and I easily installed these parts, putting the light recoil spring in the assembly.

I then loaded up a magazine of Lapua Midas match ammo (that had been a chronic problem round) and rattled off 9 shots without a hitch. Ejection was positive and the cases landed 5 feet away. The firing pin hits were deeper and longer.

I highly recommend these upgrades (Tandemkoff extractor, new style Ruger OEM firiing pin and Volquartsen recoil rod spring assembly.) These upgrades were very easy to perform and there are videos on YouTube on how to replace these parts that were very easy to follow.



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Old March 6th, 2017, 06:35 AM   #2
 
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Just to be clear, it was a modified Mk I that failed with standard velocity ammo not a stock Mk I, right?
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Old March 6th, 2017, 12:36 PM   #3
 
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Also, standard velocity .22LR is NOT subsonic.
My Mark I from 1972 fires standard vels (at least 50,000 rounds) with no problems.
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Old March 11th, 2017, 08:09 PM   #4
 
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The modification to the Mark I was a Clark trigger job. It did not modify the recoil spring, firing pin or extractor. The ammo in question is Eley and Lapua Match ammo at about 1060 fps. CCI standard velocity is listed as 1070 fps, which is subsonic. Some makers standard velocity are subsonic and some aren't. Eley's high velocity ammo is @ 1250 fps, their standard velocity match ammo is listed on their website as 1080 (tho my lots are listed at around 1060)) and their subsonic is listed @ 1040 fps. I wanted my pistol to be able to handle the subsonic match ammo that I have several cases of that didn't quite measure up for benchrest competition. The modifications that I made allow my Mark I to reliably function with this Match ammo.

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Old March 12th, 2017, 07:07 AM   #5
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blackvoid, With exception of "Hyper Velocity" 22 LR ammo, all High Velocity and Standard Velocity 22 LR ammo will be subsonic in barrels less than 12". The last time I chronographed Wolf Target Match, rated at 1080 fps from a 24" barrel ..... it clocked in at 825 fps from my Ruger MK III with a 6 7/8" barrel. Typical High Velocity ammo will chronograph at about 900 fps. The speed of sound is about 1150 fps depending on altitude, humidity, and temperature. Subsonic does NOT mean the ammo won't make a bang .... it just means the bullet moves slower than the speed of sound.
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Old March 12th, 2017, 09:23 AM   #6
 
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I failed to mention that I was at the range on Thursday with my Mark I and tried an assortment of old match ammo (Eley EPS Tenex and Match, Eley Semi-Auto, Lapua Midas, Lapua Master M, & SK Match 50). I had only a couple stoppages in about 200 rounds, which is very acceptable to me and especially coming from 2-3 stoppages in every magazine, that I was getting before the modifications with these same match ammo. Had I not had all this low-powered match ammo that I wanted to use up, I would have just used higher-powered, higher velocity ammo, that my pistol was handling quite well. When all this old sub-par match ammo is used up, I will probably exchange out the low-powered spring and put in the Volquartsen recoil spring that matches OEM specs and then just shoot the much cheaper non-match ammo. The Volquartsen spring assembly also came with a heavier spring for hyper-velocity ammo, but I don't see myself shooting that type of ammo in this pistol. The $35 I paid for these upgraded parts was certainly well worth it.
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