Fix / Repair Winchester Model 70 Detachable Box Magazine (DBM)

[lajd]

Years ago, I bought a used Winchester Model 70 with a Detachable Box Magazine (DBM). As far as I could tell, it was in great shape and little used. Judging from the model number, it was from the early 90s, although it looked close to new.

A couple years ago, the magazine broke on a hunt. I blame my dad, since he was using it at the time, but that is pretty much beside the point. It was hard to figure out exactly what was wrong, but clearly a spring had broken.

I took the gun to the local Winchester specialist, who told me these magazines were not serviceable, and they were no longer being made, and that I was basically SOL. I called Winchester, and they basically told me the magazines could not be repaired. Which was a real bummer, because I like this gun quite a bit. And therein begins my story...

(I decided to post on Calguns because the Winchester forums don't seem to be to active, and I don't really participate in any forums, but I wanted to share this information with any one else who had the same problem I had. Note that I am in no way a gunsmith, and I am sharing this for entertainment purposes).

Eventually, I came across midwestgunworks.com, which apparently bought all the inventory from the bankrupt USRAC. They had original mags, but wanted $115 for them. So I decided to take a closer look at this "non serviceable" magazine.

In the first picture, you can see the follower is drooping, particularly on the bullet side of the mag.

In the second picture, you can see how the lips of the mag base are rolled over, to lock the base plate to the mag body. But the primer side lip seems to be more of a "tab".

[lajd]

Default Fix / Repair Winchester Model 70 Detachable Box Magazine (DBM), 2

So clearly that tab had to go.

In picture 3, you can see that I dremeled off that tab on the mag base plate.

In picture 4, you can see the base plate now can be slid off. It requires squeezing the mag body, because there is a small notch on the mag plate that locks into a detent on the body.

Alright, now I am finally getting somewhere...

In picture 5, you can see the components of the magazine (which was cool - I was never able to find a schematic, and I could not figure out how the springs worked. Turns out there are two rolling springs on either side of the follower, that sit in pockets in the follower, and roll up and down as cartridges are loaded. They attach to the mag body through tabs that fit in a slot on the mag body wall. The tab on one spring had broken...

You can see more detail in picture 6. One broken rolling spring, and one rolling spring that is still properly attached, and presumably, functioning.

[lajd]

Default Fix / Repair Winchester Model 70 Detachable Box Magazine (DBM), 3

I had not come across these types of rolling springs before, and had not idea how to fix it (again, I am not anything close to a gunsmith). All my bolt action use leaf (?) springs, and all my mag guns (pistols and rifles) use "regular" springs.

I figured why not try to repair with regular springs.

The first thing I did was to cut a spring lock plate that would hold the bottom of the spring in position, and allow me to slide close the base plate. The other end of the spring would fit in the pocket underneath the follower, where the rolling spring had previously been.

Picture 7 show this. I cut it from some roof flashing I picked up at the hardware store.

Picture 8 shows what the new assembly will look like. I found the spring at the hardware for a couple of bucks for a 4 pack. Century Spring model C-762

Picture 9 - I epoxied the spring to the locking plate

Picture 10 - After some experimentation, I cut it to size.

[lajd]

Default Fix / Repair Winchester Model 70 Detachable Box Magazine (DBM), 4

Picture 11 - the final assembly.

Picture 12 - the mag seems to look and work like it should

Picture 13 - the mag loaded with three rounds. I think it originally held 4. But I think the new spring takes up too much room, even fully compressed, for that last round to fit.

I have several full mags through the action, and it seems to function just fine. I have not yet had it on the bench or in the field. I will have to see if the base plate can handle the recoil. However, it still does "lock" into place with that tab, and based on my manhandling it, I think it should work.

[Sky_DiveR]

Good thing you're good with your hands and know how to use the ole' noggin. Saved yourself $115 + shipping. Outstanding job.

Now that you know what failed, I hope you still don't hold your dad responsible. Coil springs like that do just fail all by themselves through use.

[langss]

That is a great fix. I know someone with the same problem. Thanks for Posting the information.

[lajd]

Glad it is helpful to somebody! One thought I had is that a progressive spring might work better - allowing for a stronger and more consistent feed. It also might make enough room to get a 4th round in the mag.

I will also point out this this magazine is sort of a shameful design on the part of Winchester. Why on earth would you make the mag non serviceable? That saves - what 5 cents??? I also wonder if they stopped making the detachable box magazine models because these springs were breaking (I read somewhere that they only made them for a couple of years).

Also, Sky, I continue to hold my dad fully responsible because, well... why not!

[lajd]

FYI. I took the gun to the range this weekend, and fed a couple dozen rounds through the mag and gun without issue.

[wapiti06]

Great info,I am having same problem. Can someone repost pic's of repair processe again because I can't seem to view them today, or send them directly to my e-mail. rjcatman@kalama.com