Ultralight Ultralight Rifles

[KyleR1985]

Interesting, I think Kyle or someone got right about 2.4 with the 77s, but can't remember which lower that was. I hope I don't have to do any surgery to make the 79gr drt fit which I have on the way finally. 2.36 works well with the Tennessee arms lower without cutting anything, maybe a little longer would work

I’ll have to go back to my notes. But I think I filed my carbon lower magwell, upper, and barrel extension to allow 2.4” overall. I think I Loaded a couple TMK’s at 2.39”.


My load testing shows a much bigger increase in velocity than I would’ve expected gaining .1” of case capacity.


I’ll see what I can dig up.


For reference, this is from my wife’s Howa mini with a 16” barrel:




I’ll have to find my notes on OAL at that CBTO, but it was measured with hornady comparator.

Bolt was a little heavy at the 27gr load.

Screamin

 

[Thegman]

Well crap, it's much worse with the barrel on, regardless if there's a round in the chamber or not. Pics for you all, notice the strait-back cam action, and the one smooth (rain proof) side.
One Pic shows the bolt being forced forward but yet it still needs to go another 3/16"! It's looking like the upper is not machined correctly, but it might be that the bolt isn't able to be pushed in deep enough. I tried a lot of force, like 50lbs, but no difference, it's a hard stop. Back to BCA it's going,
Maybe i got a bear creek arse version...
View attachment 849405View attachment 849406View attachment 849407

Probably not worth messing with too much, but can you try pulling the bolt out of the carrier and removing the spring? Just trying to isolate that variable.

If the spring is too large, I imagine it could be too long when fully compressed and stop the carrier from moving far enough forward to close the bolt.

 

[Trackselk]

Probably not worth messing with too much, but can you try pulling the bolt out of the carrier and removing the spring? Just trying to isolate that variable.

If the spring is too large, I imagine it could be too long when fully compressed and stop the carrier from moving far enough forward to close the bolt.

I'm not sure. I wanted to try that, but all I can see is a small pin which looks more like it separates part of the bolt, versus removing the whole thing. I'm eager to get it replaced, so I'll hopefully have it gone in the mail tomorrow. I'm guessing they put too long of a bolt in it, as it looks to function well, but is limited prematurely. I'm afraid to start driving out pins, as they might use that as an excuse to not replace it if I leave any marks...

 

[Thegman]

I'm not sure. I wanted to try that, but all I can see is a small pin which looks more like it separates part of the bolt, versus removing the whole thing. I'm eager to get it replaced, so I'll hopefully have it gone in the mail tomorrow. I'm guessing they put too long of a bolt in it, as it looks to function well, but is limited prematurely. I'm afraid to start driving out pins, as they might use that as an excuse to not replace it if I leave any marks...

Take a look at YouTube on removing an AR bolt from a carrier. It's super simple, won't hurt anything, won't leave marks and doesn't require any tools. Takes about 15 seconds. Something you have to learn with ARs anyway, so now is a perfect time!

 

[Southernfried]

Here are some other videos to help the OP.

BCA bolt

BCA bolt pt 2

BCA bolt pt 3

Link to another forum on the BCA

Hope it was ok to list another forum, if ya want to learn AR's that is the place.

 

[Trackselk]

Take a look at YouTube on removing an AR bolt from a carrier. It's super simple, won't hurt anything, won't leave marks and doesn't require any tools. Takes about 15 seconds. Something you have to learn with ARs anyway, so now is a perfect time!

Thanks, that is ridiculously simple, I'll see what it reveals