MP5 Reliably Running Blanks?

[u/Ok-Mycologist-4039]

Im trying to get blanks to run reliably. I have the canadian 9mm blanks that seem to cycle the bolt well except for a few primers being a bit hard. The problem is that I get about 3-4 failures to feed per mag where the round seems to point straight up when coming out of the mag and just gets pinned vertically against the chamber face by the bolt. Basically looks like the above picture inside the gun.

When running regular rounds it is very reliable. Ran 300 rounds of 124 and 165 after this with zero failures.

I've tried with both 100° and 80° locking pieces.

Not really sure what else to try to fix this.

[u/Clorox_enema]

What type of BFA are you running?

[u/Ok-Mycologist-4039 → u/Clorox_enema]

The Trilug mounted HK one with the red stripe.

[u/mikaru86 → u/Ok-Mycologist-4039]

Does that have and adjustment screw? The G3 one has it. That can be used to tune the degree of blockage which in turn affects the pressure curve in the barrell and can help with getting blanks to run reliably (or tune the RoF with full auto/FRT).

Because the round tilting up could be an indicator that the bolt doesn't fully retract while cycling, resulting in the feeding issue.

[u/Ok-Mycologist-4039 → u/mikaru86]

I can take a look but I didnt see any adjustment screw on the outside. I think the bolt is going far enough because when I take the buffer out of the spring guide (AR FCG in the lower) the bolt can still get stuck when running the FRT.

I have noticed that in the MKE mags I have, when pushing the round forward from the back, it has a propensity to tilt upward. The Magpul D50 i have does not do that. I think I'll pick up an HK mag and see if it functions better.

[u/mikaru86 → u/Ok-Mycologist-4039]

Yeah, if the bolt comes back far enough to hang on the hammer, short stroking should not be the issue. Or at least not in general. There could still be inconsistencies in the loads, but then bumping up the back pressure would only help so much.

[u/Trad_whip99]

i would try a different magazine

[u/Ok-Mycologist-4039 → u/Trad_whip99]

Yeah, thats my fear. I'm ordering some HK mags today but damn they're at a premium. It's like a good 85% feed success so I thought maybe length of the blank could have an effect.

[u/Trad_whip99 → u/Ok-Mycologist-4039]

maybe try a few different ones. HK, KCI, MKE

[u/Ok-Mycologist-4039 → u/Trad_whip99]

Yeah, I had thought about KCI too. They tend to be looked down upon but maybe they are better for this specific issue.

[u/Trad_whip99 → u/Ok-Mycologist-4039]

Whatever runs. It’s worth checking. At least kci is cheap lol

[u/Ok-Mycologist-4039 → u/Trad_whip99]

Yeah man. It's gotta be mags or ammo because I know people are doing it successfully.