Non-standard recoil spring in AMT Backup

[Sturmcrow]

I bought a 40 S&W AMT Backup, and reamed the chamber out to 10mm Auto. The magazine is 45 ACP length, so removing the spacer inside allowed 10mm to feed like a charm. If you do a google search, there is a fairly exhaustive writeup about the process that another fellow put together.

The problem is, this thing kicks like a mule. I am fairly recoil insensitive and am more worried about what this is doing to the gun than to my hand. I believe that the recoil spring needs to be greatly strengthened. At the moment it seems that the slide is slamming into the back of the receiver, giving the large amount of perceived recoil. The whole gun is not that much lighter than my Glock 20, though I suppose the slide is quite a bit lighter.

I've checked the Wolff site, and they do have springs for this gun in its 45ACP configuration. I know that 45ACP is much lower pressure than 10mm. Am I correct in assuming that I need even stronger springs than those?

Other than measuring the spring rate of the current spring with my bathroom scale and trying to find something of similar dimensions, but higher rate at the hardware store, do I have any other options to pick up a stronger spring?

[ReloaderFred]

One thing you'll have to consider when looking for another spring is "spring stack". That's the total sum of the diameter of each coil times the number of coils. If you go above that total with a new spring, the recoiling slide may smash the spring.

You may be able to run another spring inside your current spring, or even outside your current spring, if there's room. It's been many years since I've seen the inside of an AMT Backup, so I don't remember how much room there is in there.

Sometimes doubling springs works, and sometimes it doesn't. I would start off with a much lighter spring inside the current spring and see if there's still room for the slide to fully retract. If there is, then you can go from there.

Hope this helps.

Fred

[Sturmcrow]

Fred,

Thanks for the idea. I had not considered another spring inside, and had also kinda thought that the spring stacking up was what stopped the rearward movement of the slide.

I think a call to Wolff is in order. Do you know if they have decent customer service?

I did some measurements. It looks like my current spring stacks up at 0.66" (21 coils, 0.031" thick). I think the gun could handle up to 0.725" of spring stack. There is quite a bit of space inside the current spring, aside from where it narrows at one end. I think you may be on to something. I could fit a spring up to 0.05" coil thickness inside, or a bit smaller, to leave clearance for movement.

[ReloaderFred]

Wolff has excellent customer service, Sturmcrow. I would look for a light spring to go inside the factory one, if there is room. You probably don't want to double the spring load, as that would probably be too much. All the double spring guide rod setups I've seen have combined a light and heavy spring to accomplish the right balance.

Hope this helps.

Fred

[220swiftfn]

I'd suggest calling Wolff to pick a Tech's brain as well.


Dan