Cf-w a bolt setup

[CapnMorgan]

My a bolt runs great with 158gn subs I load, but not very reliable with 115gn store bought stuff. I remember reading a post by vegas about the original cf-w but I can’t find it. It’s currently as I received it from practical machine and slides freely in the upper. The problem is a closed bolt on an empty chamber randomly (short stroke).

I recall something about spring colors and cutting some off but can’t seem to find anything. If someone could point me in the right direction I would appreciate it.

Oh, it’s in a swd m11/9 smg.

 

[mtlcafan79]

Is it 115 UMC? That stuff is dirty and underpowered.

 

[KickStand]

I would cut a coil off and test it. If that didn’t work, keep cutting and re-testing until it works.

Ammo varies tremendously with manufacturers.

 

[Hey...]

Different issue, but mentioning incase it helps someone else.

My A-bolt needed a stronger extractor spring to run without a suppressor.

Both subs and 115. The suppressor’s back pressure was a crutch helping the system. Changed the spring to a stronger one and final puzzle piece solved.

 

[donkeyslayer]

Has it continued to fires after you release the trigger?

 

[CapnMorgan]

Hasn’t continued to fire after i release the trigger. I have only fired it suppressed, will try unsuppressed next time. I feel like the recoil spring is too heavy, but I don’t want to start hacking at stuff if im not sure lol. Something else I noticed is the bolt will travel far enough back to remove the charging handle. I don’t know if the bolt travels that far during live fire though.

Also, the barrel is ilwt 3 lug, upper is a standard m11 I ordered from sam. Standard m11/9 puck charging handle.

 

[Kramer]

Most 115gr causes issues in many guns and should be avoided.

 

[Vegas SMG]

Which “store bought” ammo are you using? I tested many thousands of rounds from over a dozen different manufacturers with various bullet weights.

I’d try different ammo before you start clipping coils. As shipped, the bolt should run perfectly providing there are no barrel alignment issues or heavy bolt to upper friction. The bolt should slide easily in the upper.

 

[Offmarksman]

Thousands of unsuppressed rounds with various brands of 115gr ammo. No issues…

 

[Gaujo]

I can run any 9 mm that there is in my M11A1, and you have way more stroke than I do, so it's a spring or friction thing.

 

[CapnMorgan]

I have herters, wwb, and blazer brass. Im not exactly sure what was in which mag. Not all mags malfunctioned. So im not sure which ammo it was. My 158gn reloads ran flawless. And some of the other stuff ran fine. Ill get some more range time in this week and not mix up my mags this time. All off this ammo ran fine in same upper with stock bolt. And I can’t feel any dragging or rubbing when cycling the bolt. It drops in and out freely. No wear marks anywhere.

 

[Maniac11/9]

Thousands of unsuppressed rounds with various brands of 115gr ammo. No issues…

Me too. I only buy 115gr 9mm ammo because it works for me.

 

[Gaujo]

Well you can buy a $4 spring and find out.

 

[Vegas SMG]

It may be unlikely, but what kind of magazines are you using? I tested with OEM Zytel mags, converted Madsen mags, converted PAM2 magazines, and Shockwave magazines.

I mark all of my magazines with a number or letter on the floor plate. If you have a malfunction with magazine number five, you can isolate it and check it later.

While we’re talking about magazines, slowly hand cycle the bolt with trigger depressed and an empty magazine inserted. Check for drag on the magazines.

 

[Hey...]

Yes on magazine drag. Most mags need tuning.

I use machinist’s dykem to mark the feedlips, run the bolt over and hand file if needed, put more dykem and repeat until the fluid is untouched. Having mags tuned is a base requirement, no bolt will make up for unfitted mags.

PAM2 have cartridge release issues that can be solved, but again, if mags run full speed the CFW (should) be close other than maybe an extractor spring which was my case.

I didn’t buy a specific spring from a seller. I used spring stock of similar size (I keep a lot of springs to tinker with) and in my case +1.5 coil of the same dimension stock and it was the key. McMaster Carr sells the spring in bulk if you measure and search.

 

[Vegas SMG]

It’s interesting that I’ve never seen or heard from another customer with a week extractor spring problem, but such is the “MAC” world. Just when you think you’ve seen it all or know everything, something weird will invariably present itself.

I rebuilt an A bolt for a high volume shooter with an estimated 30,000 rounds down range, and the extractor and extractor spring were both still good. In fact, all the components looked normal were within spec, but all were replaced as best practice given the round count.

I would make sure the bolt components are all lubed rather than running the bolt dry. Any bearing surface should have a small amount of oil to help the surfaces mate and move freely.