UBR Question

[crimsonstone]

Hey guys,

Just ordered a Magpul UBR. I was wondering which buffer I should buy to begin with. I've got a 16" midlength rifle.. Will a standard carbine buffer work well, or should I buy an H buffer?

[John123]

Magpul's web site states this about the UBR.

• Uses carbine buffer and spring

hope this helps.

John

[crimsonstone]

I feel kind of silly.

I checked out Magpul's website while I was at work... must've read right over it.

Thanks, John.

[Warrior]

I feel kind of silly.

I checked out Magpul's website while I was at work... must've read right over it.

Thanks, John.

I think they mean not to use a rifle buffer. dimensionally the carbine buffer, H,H2,H3 are all the same they differ in weight. So you should use the appropiate weight buffer in the reciever extension. However you said you are running a 16" middy, the carbine buffer is fine you could go to an H buffer if you will only run 5.56 ammo in it. Just make sure it runs reliably with your ammo and you'll be fine.

[crimsonstone]

Interesting.

Are you saying that I should only use 5.56, instead of .223? Umm... 5.56 produces greater pressure, right? Greater pressure + heavier buffer = better compensation during cycling? Using .223 (less pressure) with a heavy buffer would be more mass than the round was designed for... therefore a carbine (lighter buffer) would produce the correct (or more correct) cycling ratio?

I'm really trying to pull together the very little knowledge I have for the topic to make a good guess for your comment. Am I close to being correct? I hope so.

[Warrior]

Interesting.

Are you saying that I should only use 5.56, instead of .223? Umm... 5.56 produces greater pressure, right? Greater pressure + heavier buffer = better compensation during cycling? Using .223 (less pressure) with a heavy buffer would be more mass than the round was designed for... therefore a carbine (lighter buffer) would produce the correct (or more correct) cycling ratio?

I'm really trying to pull together the very little knowledge I have for the topic to make a good guess for your comment. Am I close to being correct? I hope so.

Yes pretty close. The idea with a heavier buffer is to slow down the cyclic rate and reduce wear on parts as well as having a softer recoil impulse. 5.56 is loaded to higher pressures so it would be forceing your BCG back faster and harder than with .223 ammo. With the heavier buffer you are slowing that down a bit. With some configurations its possible to cycle so fast that the mag can't keep up and you'll have FTF. You have a middy gas system and a 16" barrel so a regular carbine buffer would be OK. I run a H buffer in my middy which happens to sit on a lower with a UBR. Hope this helps a bit man

[crimsonstone]

Awesome. Thanks for the info. I'm glad I was on the right track. One of those instances where trying to explain it myself helps solidify the knowledge.

I'm very excited to finish building this rifle. Almost done...

+1 to Warrior!

[Warrior]

Awesome. Thanks for the info. I'm glad I was on the right track. One of those instances where trying to explain it myself helps solidify the knowledge.

I'm very excited to finish building this rifle. Almost done...

+1 to Warrior!

Thanks man.
be sure to post some pics when your done, and ask questions if in doubt.