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New rifle seems to run slow


trouble

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I built my first rifle using a 18" barrel with rifle gas. It seems to run very slow compared to all the carbine and mid gas guns I have. It does not short stroke, and it locks open on a empty mag. The rifle runs fine it just seems to run slow like I am waiting for the bolt to close to get the next shot off. Is it just the way rifle gas runs or is it just a diffrent impulse feel? Or is it just me. Any opinions or help on this would be great. Thanks

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You shouldn't have to wait to get the next shot off. If its working as it should, and it sounds like it is, maybe its just a different feel from what you normal shoot. How much lube are you using on the bolt carrier?

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My recent build was under gassed and felt just like this. It didn't start short stroking unless it got dirty but my rate of fire was noticeably slower and you could actually see the bolt carrier moving a tad bit slower in videos. I just had the gas port opened up a little bit and it was back to the way it was before I swapped barrels.

You could also check the gas block alignment and the gas port for burs.

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I would try it on another lower, which will narrow it down to a buffer/spring issue or an upper problem. If it runs slow on another lower, then look for friction in the top half. Full weight carrier, semi carrier, or lightweight? Brand new bolt/ carrier assembly? Sometimes a rough finish in the carrier bore or the cam slot slows unlocking. Some lower and bolt carrier combinations allow pmags to drag on the bottom of the carrier. That's easy to check by swapping in a forged alum mag. How easily does the carrier slide in the upper when you aren't compressing the buffer? There are a number of possible causes that aren't gas related. I had one brand new rifle come in that still had glass beads floating around in the upper from before anodizing! Made it all the way through final assembly without ever being rinsed out. Major name brand too! You could watch the bolt open and close, but it still cycled. Operating speed doubled after a thorough cleaning.

Also I agree with Ddustin about checking gas port alignment and debris/ burrs. What is gas port dia? Also, what bullet weight?

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What BCG? Is it new and coated (NiBo)? What stock? I agree with swapping the parts with your other guns to see if you can isolate any differences related to different stock/buffer, different BCG, etc.

-Mike

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There is a binding/friction problem somewhere. Start looking for signs of rubbing on any mating surfaces. The bolt carrier should slide freely in the upper (with the rear pin out and the rifle opened up or the upper removed from the lower). If it has that much drag and still cycles, I believe that you are getting enough gas to run the gun, so it shouldn't be gas related. What buffer/spring/tube combo are you using? How does it feel when you just cycle the bolt with the charging handle?

Hurley

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Try a different BCG. I have heard from multiple sources that a NiBo coated BCG seem to require a break-in period. I have been having trouble with a new rifle build and it ran like a champ with a borrowed uncoated BCG. Put my NiBo BCG back in and the troubles come back. Sounds like you have other rifles you can rob one from? I played around with some different buffers, but if I can't get mine to run, my NiBo bolt is going back...

-Mike

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