Modern Sporter builds Q&A

[onetwentyish]

My BCG sits proud of the upper even when it is at its farthest point in travel.
I thought that it was a little unusual but if you push the upper backwards the carrier engages the buffer and closes the gap.
It seems like that’s how it was designed to work.

Unless the tab at the rear end of the BCG is too tall to fit inside the buffer tube... it’s hard to tell from the pictures.

Thats exactly the case. Its the same height a gas key would be, but to make the MS differ from an AR they thickened the lower and shortened the upper so your BCG protrudes. Ingenious really, but in this instance its no bueno.

[Crashed]

Sweet, just got my phone call my set is all ready. Now have to figure out how this box of parts I have collected actually gets all together to form a complete pew pew machine.

[Dietz]

Seems like opening the ejection port for the very few who will use big calibers is going to cause a bunch of weird issues and severe uneven wearing for everybody down the road. The top bolt carrier sliding surface on the ejection port side is unsupported, it doesn't contact the upper at all for the lenght of the port, and it hits the ledge created by the opened port when it moves back...

When the bolt carrier is in battery, the rounds in the magazine push up hard on the bolt carrier... having both sides of the top of the carrier contacting and sliding along the upper is very important, otherwise the bolt carrier is getting some weird twisting force and motion during cycling if one side is floating unsupported like that because of the rounds in the magazine pushing up on it.........................no?

Can ATRS chime in on this please?

[robab]

It’s a Spikes Tactical Kit, I gutted an upper. I have a lower in run 2, if you can cut a notch over the buffer tube loop I’m happy with that (if there’s an extra cost for machining I’d also understand). The charging handle would cover the notch anyways. The more I look at it the more I think the barrel needs that material, it’s right where the chamber ends.

I have a cmmg 22 kit my upper is on route. I’ll try it and report back next week sometime.

[Kratos]

I have a cmmg 22 kit my upper is on route. I’ll try it and report back next week sometime.

If the BCG looks like mine it won’t work, and from what an internet search shows it has the tab.

[robab]

If the BCG looks like mine it won’t work, and from what an internet search shows it has the tab.

I’d say your right. But I’ll try. I may even send to a machinist to modify it to fit if possible.

[greg olmstead]

I wonder if the jp 22lr kit would work. It looks like a different setup

[scourge18a]

I see the issue with the 22 tab, if it were me and I was dedicated to it I would file the tab.
But that issue aside, here is how the BCG sits if anyone is curious. You just slide it to the rear and pop the front pin in.
[IMG][/IMG]

[jiffx2781]

...

[alberta tactical rifle]

I've never built an AR before so this might be an obvious question but:
Do you guys have any recommendations for lubrication?
I understand you're supposed to apply some grease to the barrel nut threads?

For BCGs and general lubrication G96 Gun SPRAY is what we recommend on all of our semi autos. For barrel retention nuts moly grease, we sell both.