AR-15 .40 cal carbine

[392heminut]

So, I got the .40 S&W carbine built and took it to the range over the weekend. It's got a 16" barrel and uses Glock mags. (No pictures yet) It's got the PAW lower with their 9mm buffer and spring in it. Damn thing has a pretty good kick and flings the brass a good 20' at about 4:00 o'clock! I'm thinking about dropping a Sprinco orange spring in there to tame it down and then maybe experimenting some with a heavier buffer. @98Z5V, what's your thoughts on that spring in this app? I know you have experience with them.

Edited May 27, 2019 by 392heminut

[Albroswift]

I know I'm not 98, but:

A good way to tell what the recoil system is doing is look at the buffer bumper occasionally. In my opinion it should show signs of bottoming out but not beating itself up.  20ft at 4:00 sounds about right.  Experimenting with different springs and buffers is the name of the game.

Running reliability?

What is the weight/length of your buffer? I'm running a 10oz in my 16in carbine with a 308 carbine spring.

 

[98Z5V]

6 hours ago, 392heminut said:

So, I got the .40 S&W carbine built and took it to the range over the weekend. It's got a 16" barrel and uses Glock mags. (No pictures yet) It's got the PAW lower with their 9mm buffer and spring in it. Damn thing has a pretty good kick and flings the brass a good 20' at about 4:00 o'clock! I'm thinking about dropping a Sprinco orange spring in there to tame it down and then maybe experimenting some with a heavier buffer. @98Z5V, what's your thoughts on that spring in this app? I know you have experience with them.

That's a good spring to run in a 7.000" extension, and tame a .308AR, so it would be a good choice in this application.  We all know that .40 is just "10mm lite," and it recoils like it.

At SHOT this year, I hit the Sprinco booth up - the whole crew did, 4 of us.  We spent over an hour there BSing with those guys, and talking shop, talking specs - they get it.  Look into their "convertible buffer."  It was close to release during the show, and it's badass.  It's atake-apart buffer, with all the weights you'll need, so you can tailor that thing any way you want to.  It's pricy - but it's every buffer-weight combo you could think it.  I still can't find it on their website, so you might have to call them about it.

That 9mm buffer you got - it's longer than regular 3.250" carbine buffers, and heavier, right?  I have two pistol buffers that are 8oz, and those are doing a good job - but on 9mm and .45ACP carbines.  That ain't .40.    

Edited May 28, 2019 by 98Z5V

[392heminut]

Tom, the buffers in both of the pistol caliber carbines are 3.25" and 5 ounces. They both have 7" extensions.The buffers seem to be plenty long enough, no evidence of the BCG hitting the lower on either rifle.

I had one or two jams with each of the 3 mags I ran through the gun, always a nose up, base down jam. That could be the magazines though. I couldn't get the same mags I use in the 9mm which work great in the 9mm (SGM) and bought some Elite Tactical Systems magazines from Brownells. I've seen a guy have problems with the ETS mags in 9mm which is why I suspect them. I'm not going to condemn the mags though until I've gotten a couple hundreds rounds through the gun. I've only put 90 through it so far.

[Albroswift]

SGM mags will also suck in a  40. Who's barrel did you use? Seems like the 40 is a lot more tempramental, magazine wise. New gen glock mags work the best. Also the no-name 31 rounders from Classic Arms work 99%  RWB  GL40-31MAG.

While the BCG is small enough that it won't ram the ears of the receiver if it goes back too far, it will be traveling a lot farther and therefore faster when it strips the round then I think would be ideal, I think you want to limit travel to about 1/8" past bolt catch. I would suggest heavier buffer and spacer or get the longer buffer style. Here is a typical spacer if you don't have tools to turn your own one:

These are a couple samples for heavy buffers pistol caliber length from Joe Bobs:

(1) KVP 7.5oz Stainless Blowback Buffer

(1) KVP 10oz Tungsten Blowback Buffer

This is a another option to the Sprinco spring:

(1) KVP Extra Power 17-4 SS PCC Spring

 

 

[sketch]

running the kvp 10,oz here had mag issues thus far? seems the lips on the glock mags i found are alitle tight like my .9mm.. 

[98Z5V]

11 hours ago, 392heminut said:

Tom, the buffers in both of the pistol caliber carbines are 3.25" and 5 ounces. They both have 7" extensions.The buffers seem to be plenty long enough, no evidence of the BCG hitting the lower on either rifle.

 

They won't have BCG overtravel and hit the lower - but they travel WAY beyond the bolt stop/bolt catch - and break that motherfucker on the last round.  Lot of force coming forward, with more distance to travel, before it hits that bolt catch.  It's like using a 3.250" buffer in a 7 5/8" extension, on a .308AR - except you're not slamming the ears on your lower.

Specific Pistol buffers are 4 1/8" long, and weigh 7 or 8oz - remember, there's not a bolt sticking out of the front of these pistol BCGs - more overtravel before the bolt stop catches it, otherwise.  Longer pistol buffers - or $1.75 in quarters stacked in the extension bottom - take up that space that the "no-bolt" leaves.  The heavier buffer weight counteracts the force of blowback operation.

Here's the Spike's pistol buffer that I stuffed in the AR9 and AR45:

 

[392heminut]

Caught this on sale and ordered it and a Sprinco orange spring;

http://tacticalsolutionsgroupllc.com/-AR-9-BUFFER-8oz_p_231.html

[392heminut]

On 5/28/2019 at 11:27 PM, 98Z5V said:

They won't have BCG overtravel and hit the lower - but they travel WAY beyond the bolt stop/bolt catch - and break that motherfucker on the last round.  Lot of force coming forward, with more distance to travel, before it hits that bolt catch.  It's like using a 3.250" buffer in a 7 5/8" extension, on a .308AR - except you're not slamming the ears on your lower.

 

Neither of my builds have BHO on the last round so that has not been an issue. The 9mm gun is functioning good but I'll stack some quarters in it and see how it runs though.

[392heminut]

On 5/30/2019 at 11:29 AM, 392heminut said:

Caught this on sale and ordered it and a Sprinco orange spring;

http://tacticalsolutionsgroupllc.com/-AR-9-BUFFER-8oz_p_231.html

Well this buffer and the orange spring made quite a difference! The gun still flings the brass back about 20-30 feet between 4 and 5 o'clock but the recoils is noticeably less and absolutely no malfunctions with the 30 rnd ETS mags. I figured the feed malfunction was the bolt just plain running too fast and this bears that out. The ammo I've been shooting has been the factory 155 grn. Border Patrol issue hollowpoints and that stuff is hot! I need to get some of my reloads put together to see how they function. The reloads I have right now are for competition and are loaded a bit longer for my 2011 so they won't fit in a regular 40 S&W mag. I'm guessing this gun will be sweet shooting with my 175 grn. TC loads.

[98Z5V]

1 hour ago, 392heminut said:

Well this buffer and the orange spring made quite a difference!

That is good fucking news, brother!!!   Hell YES!!!  

[Albroswift]

+1 on slower bolt speed making the cheapie mags feed better,  even the uber cheap ones. Red spring maybe even better judging from last sundays data, although I didn't have an orange spring to try.  

[98Z5V]

@Robocop1051 this is another one of the recent ones that could move to the new section - this is good stuff...  

[Robocop1051]

7 minutes ago, 98Z5V said:

@Robocop1051 this is another one of the recent ones that could move to the new section - this is good stuff...  

It’s been relocated to the PCC section 

[98Z5V]

You are fast like rabbit, my brother.  Astounding...  

[MikedaddyH]

Just wanted to piggyback on this thread to keep it alive ! I am going to post a picture of a AR-40s&w rifle i built , never shot ,then robbed the BCG for another gun. But it was damm pretty !

[MikedaddyH]

AR40s&w