Opening up the base of a Mark X action?

Ray B

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I have a magnum length Mark X action with custom bottom metal. The problem is that the open width of the metal is wider than the action opening. The result is cartridges hand-up on the corner resulting from the narrower action. All of the gunsmiths that I trusted to correct such a problem have passed away so now I have no one that I really trust. One solution would be to add metal to the sides of the bottom metal so that it fit evenly with the action, but holding the cartridges closer together would likely decrease the capacity from four to three rounds.

the other option would be to machine away the inside of the action so that it had the same diameter as the bottom metal. this seems to me might be the best solution but once the metal is removed it can't be put back, so I'm asking for advice on what to do. Have any of your run into this problem with previous magazine rifles?
 

Mr. Zorg

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I'm no gunsmith but have you investigated purchasing OEM magnum length bottom metal, NOS or new?

Zastava USA has indicated they're now carrying parts but I have no idea if that includes their bolt action product lines yet or just their semiauto lines.
 

baxterb

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You live in WA? Call Duane Wiebe. The contour of the magazine box and the underside of the action should match. Is the magazine properly machined for the cartridge you are using?
 

Ray B

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The bottom metal is Blackburn (pre-Swift) made for the FN/MarkX and similar 98 clones. But it is designed for actions that have had the lower portion opened.Checking the interior opening of the magazine at the rear (where the belt of the cartridge would sit) I have 3 metals to check. A 60+ year old factory Weatherby FN .87", factory MarkX from 1976 .91", Blackburn .97". nearly 1/10th increase in width. the follower of the Blackburn is also wider as it properly fits the wider opening in the magazine. I see no great functional advantage to the wider magazine. It doesn't allow the cartridges to compact sufficient to get another one into the magazine so the capacity remains at 3. Simplest solution and likely the one that I'll try to see what I think is to get a standard follower that will fit the action and make a sleeve that would fit inside the Blackburn metal to fit the narrower follower and the underside of the action.

I could get a factory bottom metal and replace the Blackburn, saving it for a future rifle to be built on an FN/MarkX action where the gunsmith would fit the two parts and chamber fir a cartridge that could use the extra diameter, possibly a 404 or 404 based cartridge.
 

sestoppelman

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I don't believe that there is a magnum length Mark X action, they just remove metal from the rear of the feed ramp, and lengthen the box to accommodate longer rounds like the .375 mag. As to the other questions, no help. You already have custom bottom metal so its gonna take some fiddling. Good luck.
 

Ray B

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DSC_0653.JPG
DSC_0656.JPG
 

sestoppelman

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Yep. And the screw spacing is the same and loading port as well. I just compared a std cal action to my .375 Whitworth. Same action. They just grind away some feed ramp and stretch the box.
 

Ray B

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L to R, Mark X 1976, Mark X 1991, FN Wby 1956
T to B: Wby, Blackburn, Zastava

The problem is the width of the Blackburn opening is wider than the opening in any of the three magazine wells. The best solution would be to take things to a gunsmith familiar with such things and have him/her remove the metal from the interior of the magazine well so that it would align with the bottom metal. However I'm not familiar with a gunsmith that I trust to know beforehand what it will look like when finished and I am reluctant to provide it for OJT. The other option is to fit the bottom metal to the action. this would involve getting a follower that is the factory width and adding spacer material to the Blackburn to eliminate the step where they meet.

My guess is that I will go with option 2 as a stop gap, then continue the search for a gunsmith. I see Duane Wiebe referenced. He lives about 200 miles from here, so I may give him a call and see if he will stoop to such menial jobs, or possibly refer me to someone.
 

sestoppelman

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Yeah its tough to find good smiths these days. My go to guy retired recently, worked near Everett, just down the road an hour from me. I had a project in mind but I may just bag it.
 

baxterb

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That Blackburn looks wide - is it specifically for the 375? How is it marked? I notice there are no shoulders in the front of the box to match up with the shoulder of the cartridge - meaning it looks like it's not setup for a specific cartridge - which they all need to be. The wider box dimension isn;t for added capacity, it's to allow the rounds to stack properly per Mauser's rule.

What calibers are we looking at? If you remove the follower from the spring, set it on a table and then set the box over it and lay in your rounds, will they lay correctly? Lots of things are going on with the Mauser system


sestoppleman - do you mean Mark Stratton?
 

baxterb

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I just found this on the Mauser geometry - this is what your action/bottom metal need to be configured to - based on your cartridge. With a Mauser, everything starts with the cartridge - then you go from there. A year ago I spent 3 days with DArcy Echols and my 9,3 doing this basic work to get it to feed. It fed horribly before the work, like a dream after.

https://www.africahunting.com/threads/proper-magazine-layout.35015/#post-366190
 

Ray B

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The three point contact works but I am not sure that it is necessary for proper feeding. If the cartridges are staked in a two row magazine the first cartridge in will contact the follower on the cartridge bottom and part way up on the inside of the case. It will also touch the magazine wall. the second cartridge in will touch the upper side of the bottom cartridge, the other side of the magazine and then the side of the cartridge that is above it. If the magazine is too narrow, that is that cartridges in a vertical row do not touch, I don't see that as a problem. the cartridges will be held by the two cartridges in the opposite row and the magazine wall. The problem will exist if the magazine is too wide. A cartridge will touch the magazine wall and the cartridges above and below it but there will be space between it and the cartridges in the opposite row. this space will allow for the cartridges to move about and cause feeding problems.

Given the belt diameter of the cartridge in question, 300 Wby is .532". The width of three cartridges stacked with two in a vertical row and one fitting in the notch made by the two is .993". The interior space in the three magazines has been noted as Wby FN .89", Mark X .91" and Blackburn .97", all of these are narrower than the width of the double stacked cartridges so in all three there would be a slight distance between the cartridges in the vertical rows. So they would be held in place as they moved up through the magazine.

There are two causes to my problem. One is the Blackburn follower is wider than the opening in the bottom of the action. the other is the step noted that catches the cartridges as they move from the magazine into the bottom of the action. The optimum solution to this would be to have metal removed from the action to allow for the bottom metal to fit against the action and have no decrease in opening size. the removal would be such that it would allow the follower of increased with to continue upward until stopped by the action rails. As noted, this is a one chance operation on the action since if it is done wrong, there is no way to repair it. thus my hesitancy of dashing out to the nearest machinist.

I suspect that in the future I will meet another gunsmith that I feel will be able to make such an operation on the rifle and will pursue it, until then, I'll be content to get a factory follower that will fit into the action and add spacers to the sides of the bottom metal to decrease the diameter to hold the narrower follower in place. Who knows, maybe I'll be so pleased with the stop gap that I'll just leave it that way and put the money saved toward a Heym 88B.
 

baxterb

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Your blackburn is in better shape to use the 300 WBY than my magazine was the 9,3. - at least it's got enough metal to get it to proper size.

A properly setup mauser mag box will usually allow two points of contact on the box - one at the base of the cartridge, and another at the shoulder. There will be a relief cut between these two 'steps' so the side of the case does not drag on the side of the box. Further, at the neck, the sides of the box will be relieved just enough to allow movement without dragging. If memory serves me right, Mauser's original math shows 23 different combinations of measurements for these dimensions (base and shoulder widths per cartridge) - in other words, there is no one-size-fits-all measurement, and Mauser was very specific on how he designed system. Winchester used this method until the Post-64s. Look at the mag box of a pre-64 and you will see two ridges sticking in from the sides of the box - these do the same function as what Mauser wanted.

Given your descriptions, I understand exactly what the problem is, but it will take a builder knowledgeable with the Mauser system to get it right.

Stuart Satterlee knows mausers, as does Lon Paul. Ed Lapour out in Brememerton has done excellent work, but not sure if he's retired or not. Chic Worthing in Malaga has also done great work, but I *think* he's retired.
 

Nhoro

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The three point contact works but I am not sure that it is necessary for proper feeding. If the cartridges are staked in a two row magazine the first cartridge in will contact the follower on the cartridge bottom and part way up on the inside of the case. It will also touch the magazine wall. the second cartridge in will touch the upper side of the bottom cartridge, the other side of the magazine and then the side of the cartridge that is above it. If the magazine is too narrow, that is that cartridges in a vertical row do not touch, I don't see that as a problem. the cartridges will be held by the two cartridges in the opposite row and the magazine wall. The problem will exist if the magazine is too wide. A cartridge will touch the magazine wall and the cartridges above and below it but there will be space between it and the cartridges in the opposite row. this space will allow for the cartridges to move about and cause feeding problems.

In my experience, the width of the magazine AND the width of the receiver are important. Too narrow and the cartridges tend to crossover or become cross eyed/squint. Too wide and they tend to spread too far and become pidgeon toed. With flat meplat bullets, they hang up on the chamber mouth in both cases. With spitzer bullets, you will probably be fine, the point usually enters the chamber and the bullet rides into the chamber on the curved ogive. So it depends on what you are going to use the action for and which bullets you will use. Spitzers-you are correct and will probably not notice any magazine/reciever problems.
 

Stuart Satterlee

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What caliber are you working with.
I've done quite a few custom conversions over the years based on all types of Mausers.
I use a special fixture that holds the Receiver upside down in my cnc machine.
Program coordinates are based on the magazine box opening dimensions of the magazine box that will be used for the build.
Caliber conversions involve machine work and feed and function is finalised by hand thru the experienced use of two different sized die grinders, special form mold stones and Emory cloth for final finishing.
One of my current projects is a 404 Jeffery based on a 1908 DWM Brazilian M98. I have the barreled action running 404 to perfection. It's full on conversion. I'll be starting the stock in the near future.
It's a very strong possibility I can get your Mark X working properly.
 

Ray B

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What caliber are you working with.
It's a very strong possibility I can get your Mark X working properly.

It's a 300 Weatherby. The action is a magnum Mark X with Blackburn bottom metal. At this point the biggest issue seems to be the width of the Blackburn follower- it is wider than the action open, so doesn't push the last round up to the rails. Brownells has a Wisner that I'm looking into for a swap.
 

baxterb

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What caliber are you working with.
I've done quite a few custom conversions over the years based on all types of Mausers.
I use a special fixture that holds the Receiver upside down in my cnc machine.
Program coordinates are based on the magazine box opening dimensions of the magazine box that will be used for the build.
Caliber conversions involve machine work and feed and function is finalised by hand thru the experienced use of two different sized die grinders, special form mold stones and Emory cloth for final finishing.
One of my current projects is a 404 Jeffery based on a 1908 DWM Brazilian M98. I have the barreled action running 404 to perfection. It's full on conversion. I'll be starting the stock in the near future.
It's a very strong possibility I can get your Mark X working properly.


Swap the CNC for a Bridgeport and the above is exactly what we did on my 9,3 - right down to the grinders, stones, and emery paper...
 

Ray B

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Further review showed that there were two issues. The front of the follower is slightly wider than the action opening- a problem that could be resolved with minimal metal removal. This wasn't an issue until the last cartridge allowed the follower high enough to contact the action. The main issue is that while both the length of the magazine well in the bottom metal and the bottom of the action exceed the necessary 3.6", the openings do not line-up. The magazine sits slightly forward. A portion of the back wall of the magazine could be machined out along with a little of the feed ramp on the action, and a little build-up of the front wall of the magazine would result in lining-up the two openings which would cure the problem. Now that I see the problem between the two, I can take it to the gunsmith and be able to show what the problem is and let his expertise correct it.
 

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