Pressure rating of AR9s.

[arakboss]

Are AR 9mm rifles rated for shooting a steady diet of +P+ ammo. If not where is the weak point(s)?

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[arakboss]

This guy has had success running some hot 9mm through his 9mm AR:

I have run over 1500 rds of +++P loads through my RRA 9mm upper

For sake of discussion out of a 4" barrel and a 124gr projectile

9mm = 1100 fps approximately
9mm + P ( Corbon for example ) = 1250fps
38 super will do about the same ( 1250fps )

Sidebar : When shooting IPSC you need to make Power Factor =160 for Open Division
Since Power Factor = weight * velocity / 1000

Soooo, to make Major in Open you need to drive a 124gr to 1300 fps. Keeping in mind many competitors with the Open guns will drive the bullet even faster ( more powder charge to work the comp )

My 9major loads drive a 124gr out to 1400fps

Go here for load data ( forum for IPSC shooters ) http://www.brianenos.com/forums/index.php?showforum=72

Obviously you need to be very careful and when doing this inspect your brass very carefully before loading. I wont load the brass to Major more than once

Going back to your question, I couldn't resist running some of my 9 Major loads for my Open gun through my AR ( since the AR barrel is fully supported )

1500 rds later it seem to be no worst for wear. The 9mm buffer seem to be heavy enough. I see very little "flash" out of the chamber area when bolt is coming back , so I assume that bolt is not moving too soon

To answer your question, a +P load at a leisurely 1250 would be fine

Just be carefull if you decide to start loading 9Major since driving a 124gr to 1400fps when "normal" pressures give 1100 you know that the case is grossly overloaded

BTW - for you naysayers who say you can't load 9mm to those velocities, there are literally millions of 9major loads cranked out of the basement of IPSC shooters

I load about 15k a year of 9Major. Also, if you are loading 9Major make certain the rounds never find their way into a 9mm handgun with an unsupported barrel

If I were you I would stay at +P velocities. The only reason I am running 9Major is I have a Dillon 1050 with bullet feeder set up to crank out 9Major . IT would be a pain to be set it up for two loads so I leave it at 9Major

 

[RX-79G]

Seems like the only weak point would be the bolt opening early, rupturing the case and blowing the magazine out, since there are no locking surfaces and the barrel is thick.

This is more likely with a longer barrel.

 

[arakboss]

Seems like the only weak point would be the bolt opening early, rupturing the case and blowing the magazine out, since there are no locking surfaces and the barrel is thick.

This is more likely with a longer barrel.

I am thinking it would be wise to run a really heavy buffer and adjust the buffer weight downward until I can get reliable cycling. Some others have mentioned that bolt catches or stops might not hold up well to hi power 9mm loads?

Edit: maybe this guy here

KAK Industry AR15 9MM Carbine Buffer Extended, Heavy 10 oz

Enhance the recoil management of your 9mm AR-15 build with our AR-15 9mm Carbine Buffer Extended Heavy. Specifically designed for 9mm carbine configurations, this extended heavy buffer is crafted to offer superior recoil reduction and improved shooting control. The extra weight in the buffer...

www.kakindustry.com

 

[powermad]

I'm running a Vltor A5H4 buffer (8 oz) and a Rifle green spring in mine.
I had it set up with a Law folder and the adapter added another 2 oz bringing it up to 22oz total mass which was perfect.
I haven't run +p ammo but have run a bunch of the Winchester M1152 through it which is pretty hot with an advertised 1320 fps.

I put the folder on another rifle and now need to get a 10oz buffer as 8 wasn't enough.

 

[powermad]

What tears up the BHO is using a 5.56 buffer and no spacer like a stack of quarters.

No spacers needed if you use an intermediate buffer like the Vltor A5 or dedicated AR9 buffer.
A 5.56 carbine spring isn't enough.
An A2 rifle spring or a KVP HD spring works better.

 

[billdeserthills]

I am thinking it would be wise to run a really heavy buffer and adjust the buffer weight downward until I can get reliable cycling. Some others have mentioned that bolt catches or stops might not hold up well to hi power 9mm loads?

Edit: maybe this guy here

KAK Industry AR15 9MM Carbine Buffer Extended, Heavy 10 oz

Enhance the recoil management of your 9mm AR-15 build with our AR-15 9mm Carbine Buffer Extended Heavy. Specifically designed for 9mm carbine configurations, this extended heavy buffer is crafted to offer superior recoil reduction and improved shooting control. The extra weight in the buffer...

www.kakindustry.com

I recently got a heavy buffer for my AR45 build but this guy sells heavy buffers

Heavy Buffers | Products | AR15 Carbine Buffers

 

[arakboss]

Slightly off topic but if I wanted to make one of my AR9s a manual loader how could I keep the bolt from moving back after firing. I would want to retain the capability of pulling the bolt back with the charging handle to load the next round. Would a really stiff spring work? What weight of spring might I need.

 

[Certaindeaf]

The only reason he loads his brass once is because the primer pocket will no longer hold a primer.
If you're using a progressive like he does and are using range brass, you'll never know if you have a loose pocket. You'd have to prime with a hand priming tool to prove/verify the pocket is of proper size. No amount of "close inspection" will reveal a loose pocket.

 

[TTSX]

The only reason he loads his brass once is because the primer pocket will no longer hold a primer.
If you're using a progressive like he does and are using range brass, you'll never know if you have a loose pocket. You'd have to prime with a hand priming tool to prove/verify the pocket is of proper size. No amount of "close inspection" will reveal a loose pocket.

I've found with many of my rifle loads, the pocket loosening is why I scrap them before anything else. Testing out max loads definitely makes it happen quicker

 

[Alexx1401]

Slightly off topic but if I wanted to make one of my AR9s a manual loader how could I keep the bolt from moving back after firing. I would want to retain the capability of pulling the bolt back with the charging handle to load the next round. Would a really stiff spring work? What weight of spring might I need.

If you put in enough weight the bolt will of course not open, or at least not enough to eject the spent case. As an example when the CCI Quiet rounds hit I tried a box to see what they would do. In my semi pistols they worked great. They would not cycle but did not jam. The spring was enough to keep the slide from going far enough back. So would work the same way in an AR9 but, you would of course have to have a lot more mass. To try playing with it I would start with much more mass in the buffer weight first. If you put enough spring to keep the thing shut it may be a bear to cycle. More bolt mass should get the same results and make cycling the next round far easier. Be a fun little thing to play with and get what you are after.

 

[arakboss]

What tears up the BHO is using a 5.56 buffer and no spacer like a stack of quarters.

No spacers needed if you use an intermediate buffer like the Vltor A5 or dedicated AR9 buffer.
A 5.56 carbine spring isn't enough.
An A2 rifle spring or a KVP HD spring works better.

Can you explain why a lack of spacers would be hard on bolt stop. I am going to try out two carbine buffers together in A2 style tube. How do you measure the length your spacers should be?

 

[powermad]

With too much buffer travel it pretty much turns it into a battering ram.
You want the BCG to just go past the BHO, about the width of a quarter.

With a 9mm BCG and an A2 tube with a carbine buffer you'll need a bunch of quarters.

When I was messing with an A5 tube and buffer I used a 5/8" nylon spacer.

 

[arakboss]

With too much buffer travel it pretty much turns it into a battering ram.
You want the BCG to just go past the BHO, about the width of a quarter.

With a 9mm BCG and an A2 tube with a carbine buffer you'll need a bunch of quarters.

When I was messing with an A5 tube and buffer I used a 5/8" nylon spacer.

That makes sense, thank you. I am running two standard carbine buffers in the A2 tube. I will test it by adding quarters to see how far past the bolt catch the buffers are traveling.

 

[powermad]

Why two carbine buffers?

 

[arakboss]

Why two carbine buffers?

For maximum amount of buffer weight adjust-ability, uniqueness and to use what I already have around. I also wanted to run the longer extension tube so I could get a better cheek weld in a more natural position. I eyeballed the distance from the rearward postion of buffers to the bolt catch and there is at least a 1/4 inch of space so I will have to install some spacers to restrict the travel like you suggested.

 

[arakboss]

Slightly off topic but if I wanted to make one of my AR9s a manual loader how could I keep the bolt from moving back after firing. I would want to retain the capability of pulling the bolt back with the charging handle to load the next round. Would a really stiff spring work? What weight of spring might I need.

Here is a video describing a cool Veterinarian manual loading pistol. I would like to incorporate the twist/pull operation of this pistol into an AR9 style build.

 

[Hueco]

Here is a video describing a cool Veterinarian manual loading pistol. I would like to incorporate the twist/pull operation of this pistol into an AR9 style build.

I'm running a FailZero BCG and 10oz buffer for something like 24oz recip. mass and a Sprinco Orange, 8.3" barrel.

You mention using a heavy buffer/spring to accomplish your goal…if that's the path you want to walk, you may need to get out of regular gun parts and into some homemade goodness.

As far as I know, I've got the heaviest buffer available and one of the strongest springs, and the little B still cycles 115gr fmj plink with ease.

If you want the buffer system to stay there under its own weight and tension, it'll have to be heavy. I'm thinking you'd be better off designing a locking mechanism for the bolt.