GMA 500 Jeff action

[Iclimb]

Hey wondering if GMA 500 Jeff action can be used for any other caliber? not sure if it is built specifically for that caliber? Actually hoping it would work on a 400 Jeff build….
id call them but being the weekend I doubt they will return my call.
Thanks guys!

 

[RR 314]

Hey wondering if GMA 500 Jeff action can be used for any other caliber? not sure if it is built specifically for that caliber? Actually hoping it would work on a 400 Jeff build….
id call them but being the weekend I doubt they will return my call.
Thanks guys!

Are you looking at the action for sale at one of the auction sites? I thought about it, but single square. OAL is considerably longer on the .450/400. Think it is a no go.

 

[IvW]

450/400 may not be the best idea on a bolt action..

 

[TSIBINDI]

...GMA standard magnum action will handle the .300WM, .338WM, .375H&H. .404Jeffery and the .500Jeffery. According to the GMA brochure.

 

[Nevada Mike]

I thonk GMA builds the Action for specific calibers - box. follower, etc.

 

[Iclimb]

yeah that’s what I’m wondering. It’s labeled specifically so I kinda am worried that’s what’s going on. We’ll see, I will know more Monday

 

[Ontario Hunter]

Rim diameter for 500 Jeffery is significantly wider than 404 Jeffery. You can't shrink the bolt face. Not without great difficulty anyway. You'd have to find another bolt. Big pain in the butt. Building a larger cartridge on a smaller action is doable. I did it building 404 Jeffery on 8mm Mauser action. Building something in reverse (larger to smaller) is much more challenging.

Also, the feeding rails would be set up for much thicker cartridges. They can be altered (there was a thread on that a while back) but it is a major undertaking that often as not doesn't work out. Delicate welding more metal on the rails, remachining, etc. Ugh!

I'm no gunsmith, but I think this would be on the magnitude of Mission Impossible. If it even can be done, it would be very expensive.

 

[Iclimb]

Yeah I looked up some bolt dimensions but off hand I can’t quote anything but the 300rum which was .575 if I recall

 

[Nevada Mike]

GM offers action with a couple of different bolt DIAMETERS- the bolt body, not just the bolt face.

 

[Ontario Hunter]

GM offers action with a couple of different bolt DIAMETERS- the bolt body, not just the bolt face.

Won't really make any difference re the difficulty (impossibility?) of this proposal. The only way to reduce the bolt face opening to hold a 404 Jeffery rim would be to add metal to the existing bolt (by welding) and then remachining the bolt face. Changing to a smaller diameter bolt won't work. It won't fit in a receiver opened up for a larger diameter bolt.

I dunno, maybe it is possible for a clever machinist/gunsmith to cut the bolt face back flush and start over? Then adjust head space on new barrel to accommodate it. But would there be any problems with ejection? Hmmm. I think the gunsmith would have to be in it for the fun of a challenging project. Too much labor and too much risk of it going south.

 

[Nevada Mike]

Won't really make any difference re the difficulty (impossibility?) of this proposal. The only way to reduce the bolt face opening to hold a 404 Jeffery rim would be to add metal to the existing bolt (by welding) and then remachining the bolt face. Changing to a smaller diameter bolt won't work. It won't fit in a receiver opened up for a larger diameter bolt.

I dunno, maybe it is possible for a clever machinist/gunsmith to cut the bolt face back flush and start over? Then adjust head space on new barrel to accommodate it. But would there be any problems with ejection? Hmmm. I think the gunsmith would have to be in it for the fun of a challenging project. Too much labor and too much risk of it going south.

This is the reason that I pointed out the difference… conversion to a cartridge with a smaller head diameter would difficult and probably not feasible. My opinion only

 

[gibbs30c]

The rim dia. of the 500 Jeffery is .575 and the rim dia of the 404 Jeffery is .543 for a .032 difference in dia and a .016 dia radius. so you would have to add that .016 to the circumference of the bolt face with a shim. However it may be possible to add all the .032 to one side of the bolt with a taper on the added "Shim" blending into the other side of the bolt face, and still have the firing pin strike enough of the primer to get positive ignition every time. It would also have to allow for proper feeding. It would depend on the bolt face configuration, which would work best.

I have reduced the dia of bolt faces by soldering a washer to the bolt face then machining the inside of the washer to the proper case head dia. and facing it off,.

It is done much as you would open up a standard bolt face to belted mag. dia. I have done this to get a good fit on 7.62X39 on Mauser 98 bolt faces.

However the extractor may then have to be reworked. That is why if the excess dia can be taken up on just one side of the bolt opposite the extractor and still get a very good firing pin strike, the existing extractor can be used and the amount of work reduced.

May I suggest you shop around for a P-14 or 1917 Enfield action. While of course not as new or sleek as the GMA and lacking the Square bridge they make an excellent 404 Jeffery, with only some work required on length on feed rails.

Steel blocks such as Weaver can not only be drilled and tapped to the action they can also be soldered to the action in addition to the base screws. While this of course is not as strong a mounting system as the solid bridge machined as part of the action, It comes very close.

I built a 404 Jeffery on a P-14 Enfield action that was used in a drill rifle and took it to Africa a couple of years ago.

It feeds flawlessly is deadly accurate, a real pleasure to shoot and to carry. Balance is perfect. I took numerous heads of game with it, and wouldn't trade it for any rifle out there.

If you are serious about a 404 Jeffery I would start scrounging for brass, as I believe Hornady has dropped it from their line. Brass may become as hard to get, as it was decades ago. Maybe PPU will pick it up.

 

[Ontario Hunter]

I would not try shimming one side of the bolt face. The idea is to load the cartridge straight into the chamber, not off center. Otherwise it's liable to bind in the chamber. The soldered washer idea might work but I have never heard of it. And, as I said, even if the bolt face can be modified, there's the feeding rails left to deal with. Not a project for the faint of heart ... or light of wallet.

Enfield is an acquired taste. But not yet a taste I have been able to acquire. They work ... and so does a 1962 Dodge Powerwagon. But I'll never drive one ... again.

 

[Nevada Mike]

But the Dodge Powerwagon has the cool factor.

Seriously, the Enfield P17 can be made into a very nice rifle, but it requires a good deal of work (aka Expense).

 

[gibbs30c]

I can assure you the washer "idea" works quite well as I have done it several times, again on both LR and SR Mausers. I did not come up with it, but learned it from an old gunsmith. If proper heat sinking of the bolt is done through the process, with lower temp soldering, the heat treatment of the bolt, especially the locking lugs is not compromised as it would be with the much higher temp of welding. Welding will require the bolt to be re-heat treated.

All staggered box magazines load from one side or the other, and then center about half way through the chambering process by the chamber itself. It is the job of the feed ramp to keep the the round from binding while chambering with the aid of the extractor in a controlled round feeding rifle. The only magazine system that feeds a round straight into the chamber is the single stack magazine, by the way a very good system when building a 500 Jeffery on a LR Mauser or Enfield action.

Of course the design of the round being chambered also has a great effect. Long taper rounds like the 375 H&H or the 404 Jeffery simply want to chamber.

As for feed rails I have never had a problem doing this job, and have never found it to be very difficult when "Opening up" a mag well. Maybe because I do it by hand and don't use my mill.

Now closing a mag well up such as taking a 500 Jeffery down to 404 Jeffery is a different ball game. But that is why God invented the single stack mag. Many sheet metal box mag can be fitted to convert a staggered mag well into single stack.

If I was to try to keep a staggered feed mag I would try first to make a follower that would hold the smaller dia. case against the mag well sides, rather then try to fill in the feed rails. Short of that it would be single stack feeding from the fitted sheet metal mag box to take up the excess mag well space and to bypass the feed rails altogether.

I'm not sure what you mean about Enfields being an acquired taste, maybe you haven't seen the Remington Model 720. It is a fine example of what an Enfield action can be turned into, even in a mass produced rifle.

As far as the Power Wagon I owned a 1968 back in the late 70's and early 80's. I wish I had never sold it! It never failed me and would not leave you stranded way down in some two track hole here in Colorado, as so many "shift on the fly" transfer case and auto locking hubs have done to so many late season elk hunters.

 

[Ontario Hunter]

I can assure you the washer "idea" works quite well as I have done it several times, again on both LR and SR Mausers. I did not come up with it, but learned it from an old gunsmith. If proper heat sinking of the bolt is done through the process, with lower temp soldering, the heat treatment of the bolt, especially the locking lugs is not compromised as it would be with the much higher temp of welding. Welding will require the bolt to be re-heat treated.

All staggered box magazines load from one side or the other, and then center about half way through the chambering process by the chamber itself. It is the job of the feed ramp to keep the the round from binding while chambering with the aid of the extractor in a controlled round feeding rifle. The only magazine system that feeds a round straight into the chamber is the single stack magazine, by the way a very good system when building a 500 Jeffery on a LR Mauser or Enfield action.

Of course the design of the round being chambered also has a great effect. Long taper rounds like the 375 H&H or the 404 Jeffery simply want to chamber.

As for feed rails I have never had a problem doing this job, and have never found it to be very difficult when "Opening up" a mag well. Maybe because I do it by hand and don't use my mill.

Now closing a mag well up such as taking a 500 Jeffery down to 404 Jeffery is a different ball game. But that is why God invented the single stack mag. Many sheet metal box mag can be fitted to convert a staggered mag well into single stack.

If I was to try to keep a staggered feed mag I would try first to make a follower that would hold the smaller dia. case against the mag well sides, rather then try to fill in the feed rails. Short of that it would be single stack feeding from the fitted sheet metal mag box to take up the excess mag well space and to bypass the feed rails altogether.

I'm not sure what you mean about Enfields being an acquired taste, maybe you haven't seen the Remington Model 720. It is a fine example of what an Enfield action can be turned into, even in a mass produced rifle.

As far as the Power Wagon I owned a 1968 back in the late 70's and early 80's. I wish I had never sold it! It never failed me and would not leave you stranded way down in some two track hole here in Colorado, as so many "shift on the fly" transfer case and auto locking hubs have done to so many late season elk hunters.

I'm a bit confused. How will changing the follower fix feeding issues in a staggered box? Follower is designed to push the last shell in the magazine against the walls. The rest will naturally compress against the walls due to their round shape and pressure from follower spring against the cartridge immediately below. Changing the follower will change how the last cartridge feeds. Magazine width and feeding rails control how the rest of the stacked cartridges feed.

Power Wagons should have come standard issue with kidney belt and football helmet. They were the definition of "rough ride."

 

[Nevada Mike]

...Power Wagons should have come standard issue with kidney belt and football helmet. They were the definition of "rough ride."

Oh. I thought my '47 Willys Jeep held that honor. Maybe not.

 

[gibbs30c]

The follower determines the position of, the pressure against the mag sidewalls, the tip and angle of the cartridges both at the bullet and the cartridge base, and the general alignment of the cartridges in the magazine. It does not just affect the first round in the box or the last to feed. Since all rounds stacked in the mag are held in the same above stated conditions by the round below it. Hence the follower is the absolute foundation of that stack in the mag. The follower and follower spring are a critical part of feeding for all rounds.

When we experienced feeding issues some decades ago now in the Rem 700 with Not Just the last round but with all the rounds in the mag box the issue was fixed with an after market follower. Anyone who is working on feeding issues regardless of what sequence of the rounds in the mag box that is presenting the problem but overlooks the follower is in for a a very frustrating time.

One other option for making a smaller cartridge in a larger mag well like a 500 J to a 404J would also be to build a thicker mag box that would effectively reduce the width of the feed rails

I would say if you are looking for a soft ride then yes a truck like the power wagon and anything over a 1/2 ton is probably not the best choice. But I would advise staying out of the two tracks that lead to the serious deep holes where the elk usually hide after opening day.

 

[Ontario Hunter]

Making a thicker magazine box would not "effectively reduce the width of the feeding rails." It would effectively reduce the effectiveness of the feeding rails by reducing the rails' ability to hold cartridges in the magazine (less lip on the feeding rails to hold fatter cartridges). This would "effectively" have exactly the OPPOSITE effect of what's needed to make a 500 to 404 conversion work. Clearly, the feeding rails are part of the receiver and the magazine box is not. Changing the box changes the box, changing the rails changes the feeding. Adjusting feeding for a different width cartridge typically requires changing the box AND the rails.

I just finished building a 404 Jeffery on a BRNO vz.24. Yes, I did widen the box (426 Rem Mag bottom metal) AND I had to change the rails. Here's the procedure for making the subsequent feeding adjustments. First, I lengthened the feeding ramp to accommodate longer cartridges. Then loaded the box with dummy rounds (bullets seated on empty cases with no primers). Next, I worked on the LEFT rail till it feeds correctly. THEN I went to work adjusting second dummy round feeding against RIGHT rail. When the right rail was feeding properly, THEN it was time to work on the last round in magazine. This required changing the follower so that the final round would slip sideways to the left during closing at just the right spot to start the jump under the claw. Otherwise the forward end of the cartridge would bind entering the chamber.

Changing the follower at this point did not change the feeding of the top two shells in the magazine which had already been adjusted. How could it? Those cartridges are resting against each other and the sides of the magazine box. The follower only affects placement of the shell it contacts. And it's only effect is to 1) push that shell against the side of the magazine box and 2) control to a limited extent when that shell, and ONLY that shell, jumps under the claw and onto the bolt face.

I don't need a monster mud truck to reach my game. I have two legs. And yes, I do know something about elk hunting.

I shot the below mule deer two days ago after hunting the network of coulees about five miles. Shot him by ten in the morning. The previous day my boots logged at least fifteen miles hiking the entire day. Missed a huge whitetail. The only two days hunting deer this year. My average is 1.5 days before I'm tagged out ... public land. Oh ... and I turned 71 last month.

Here's the 404 Jeffery build on Mauser 98 I completed this past summer. It cycles slicker than any factory model.

 

[Grumpy gumpy]

Unless I’m missing something, which is a possibility, if you build up one side of the bolt recess it will cause the cartridge cases to force themselves into the chamber at an angle and fire form crooked, in this case by .032” which if not corrected, could happen again the opposite way, causing undue stress on the case and I’m pretty sure lead to early case had separation. The low temp soldier with a firm fitting washer sounds like a better solution. I would, personally, have it built up by tig, machined and re-heat treated. Then I’d look at the feed rails and mag box. The spring clip idea may be thebetter solution to this
gumpy