DD mk18 failure to feed?Magazine issue or something else?

[kukworld]

Hey guys
Just went to range today to test our my brand new DD MK18 upper (0.07 gas port). I’m running a Bootleg adjustable carrier and vltor A5 with H3 buffer and springco green. Also running a socom 556rc SB can

When the gun is suppressed, and using brand new lancer mag, I’ll get 1 failure to fee per magazine. My initially thought was the buffer is too heavy and the rifle is little bit of undergassed, but my ejection pattern it’s about 3-5 o’clock, so it might not be gas issue. And then i ran one of my old black lancer magazine and it’s run good without hiccup.

So this sound more like magazine issue instead of buffer being little too heavy?

Speaking of bootleg adjust BCG, the setting is at unsuppressed. I was not able to turn it to suppressed setting due to the adjustment key is too “shallow”

If I’m able to turn the BCG to suppressed setting, I should be using H2 instead?

Experts, please let me hear your opinions

Thanks!


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[MistWolf]

Have you performed a lock back check?

I assume that when you say "H3" buffer, you mean an A5H3 buffer. It's my belief that the A5H3 buffer is too heavy. If you need something heavier than the A5H2 or rifle buffer, it's time to dial back the gas.

Do a lock back check with an A5H2 or A5H1.

[kukworld]

Have you performed a lock back check?

I assume that when you say "H3" buffer, you mean an A5H3 buffer. It's my belief that the A5H3 buffer is too heavy. If you need something heavier than the A5H2 or rifle buffer, it's time to dial back the gas.

Do a lock back check with an A5H2 or A5H1.

Yes, I meant A5H3. The bolt will lock back fine after last round with A5H3 buffer.

Unfortunately I can’t dial back the gas since I don’t have adjustable gas block


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[MegademiC]

Yes, I meant A5H3. The bolt will lock back fine after last round with A5H3 buffer.

Unfortunately I can’t dial back the gas since I don’t have adjustable gas block


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Is this with silencer, without, or both?

[kukworld]

Is this with silencer, without, or both?

The bolt locked back with silencer on, I didn’t test it without silencer but I assume it will lock back as well


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[Maharlika75]

Agree that it seems like your buffer is too heavy. You can open it up and take one of the weights out, fairly simple to work something out cheaper than buying new buffers.

[Campbell]

Same problem with the DD bcg?

[scooter22]

How many mags have you tried that have all fed reliably?

What ammo are you shooting?

Have you tried a standard carrier?

[kukworld]

Same problem with the DD bcg?

I dont have DD bcg. I purchased as stripped upper from Brownells during Black Friday sale


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[kukworld]

How many mags have you tried that have all fed reliably?

What ammo are you shooting?

Have you tried a standard carrier?

I only brought out lancer magazine that day. Black ones are old (300-500 rounds) FDE color are brand new. The only problems I have it’s with the new magazines.

The only other bcg I have it’s from KAC which doesn’t fit into this DD upper.

I was running the bootleg bcg in unsurpassed setting, so in a way it’s standard bolt. However I have to say this, when I received the bootleg bcg, the lugs are very rusty, and I have to oil it to smooth the surface out. I did contact bootleg to exchange new bcg due to unable to adjust the “gas port” however, their response has been slow.

I have been shooting primarily Fiocchi 55g ammo in 2018 through various rifle and I have been running this ammo with KAC suppressed, it’s overgassed but no hiccup.

Since the upper it’s pretty new, I’m going to running about 500 more rounds to break it in, will see how it works





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[kukworld]

Agree that it seems like your buffer is too heavy. You can open it up and take one of the weights out, fairly simple to work something out cheaper than buying new buffers.

Thanks for the input.
I would think I need heavier buffer, to give the magazine more time to feed before the bolt travels back, but I could be wrong


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[mack7.62]

Do yourself a favor and get a mil spec BCG, H2 buffer and some Gen 3 PMAG's and start over.

[scooter22]

I think the mags are the issue.

Is that ammo .223 or 5.56 pressure?

If .223, then a lighter buffer would likely help.

Also, you can definitely use the KAC carrier just NOT the bolt.




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[kukworld]

I think the mags are the issue.

Is that ammo .223 or 5.56 pressure?

If .223, then a lighter buffer would likely help.

Also, you can definitely use the KAC carrier just NOT the bolt.




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It is 223.

Bootleg just send me a replacement. I’ll test again next week. I also ordered H2 buffer to try it out


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[MadAngler1]

Do yourself a favor and get a mil spec BCG, H2 buffer and some Gen 3 PMAG's and start over.

+1

Does the upper run OK with the std DD stuff (bolt carrier and buffer)?

[glockshooter]

This seems like a normal story. People keep buying parts and pieces having no idea how they work and wonder why they don’t work. This is part of the problem I read regularly on this site. People buy stuff and throw it together without having experience of what actually works together. The parts listed in the OP were all outside of what DD originally designed the upper to work with. We building a rifle or modifying one you can’t change everything all at once. You change things as needed, not just because.

[kukworld]

This seems like a normal story. People keep buying parts and pieces having no idea how they work and wonder why they don’t work. This is part of the problem I read regularly on this site. People buy stuff and throw it together without having experience of what actually works together. The parts listed in the OP were all outside of what DD originally designed the upper to work with. We building a rifle or modifying one you can’t change everything all at once. You change things as needed, not just because.

I see what you saying, but doesn’t apply to this case. I purchased a stripped DD upper from Brownell. I didn’t change 1 single thing from the upper, it’s complete factory upper. I added pri gas buster ch, surefire warcomp and adjustable bcg...why? Because I’m gonna run this rifle 100% suppressed.

I would agree with what you said if I lm trying to build the mk 18 upper myself by testing different adjustable gas block or trying out different barrel with different gas port.



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[jackblack73]

I see what you saying, but doesn’t apply to this case. I purchased a stripped DD upper from Brownell. I didn’t change 1 single thing from the upper, it’s complete factory upper. I added pri gas buster ch, surefire warcomp and adjustable bcg...why? Because I’m gonna run this rifle 100% suppressed.

I would agree with what you said if I lm trying to build the mk 18 upper myself by testing different adjustable gas block or trying out different barrel with different gas port.



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His point is that you're trying to use a DD MK18 upper with an adjustable carrier, A5 receiver extension, and A5H3 buffer. If you buy a complete MK 18 from DD it comes with none of those things, and probably works very well.