My love hate with a Ar9

Tomme boy

Well-Known Member
These are loaded warm. I talked to the balistician from SW powders and he assured me they were safe for pressure in blow backs and guns that are rated for a regular diet of +p pressures. The powder is Auto pistol. It is 1 powder in front of hs6 and no5 for burn rate.

This is what we has in its description. . This propellant is a good alternative to Longshot, HS-6, and Accurate No 5.
 

Petrol & Powder

Well-Known Member
The problem isn't too much pressure, the problem is too much pressure for the mass of the bolt and the strength of the buffer spring.

The case probably would not rupture if it remained IN the chamber with the bolt closed behind it until the bullet departed the muzzle.

A heavier bolt, a stronger spring or both a heavier bolt & stronger spring - will delay the opening of the bolt long enough for the pressure to drop.
 
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Ian

Notorious member
Think about what Fiver wrote.

You have very low engraving resistance from a powder-coated lead bullet. You have an appropriate for cartridge powder. You likely have normal peak pressure potential in the system. The problem is the burn curve of the powder with low shot start initiation pressure. Case obturation is happening too late or not at all, so the timing is off and when you get a weak case (or whatever) once in a while, kaboom.

Tell the ballistician your shot start pressure is 1000 psi and you'll likely be guided to a faster-burning powder.
 

fiver

Well-Known Member
okay so which direction do you go?
slower would be the indicator....????????????
but then your just slightly delaying and lengthening the peak time.

faster might not pop the bolt because you ain't got the gas volume, unless it's a blowback design then that's the direction I'd go.
 

Tomme boy

Well-Known Member
I have a lot of unique but it does not meter very well in small charges on my presses. I have a large amout of tightgroup. It is what i like in several other handguns. I can not remember if i ever tried it in this one. In g19 and cz75 it works perfect. Snappy but the accuracy is really good with it. Or bullseye. I have a 8lb jug of that unopened from when I was shooting the 45acp.

I guess I will load up some with a couple different powders and see what they do. I might have to dig out my pro 1000 setup in 9mm so I don't have to change over one of the other 2 presses set up for other rounds. Just might have to rob one of the powder measures off another press. I can't remember if it has one on it or not.
 

popper

Well-Known Member
Tell me if I am wrong but it appears to be an Aluminum case. Also bullet base appears to be where it blew. Consider the case where bullet engraving in the barrel increases pressure enough to blow back the case and light bolt (case is now projectile). Stress point in the case is the ring at the bullet base. With all the blowback PCC carbines around, this problem should be majorly reported. Changing to a heavier buffer does 2 things, slams a misshaped case fully into the chamber and slows the blowback.
another 135gr that does not have to be seated as deep as this one another clue. I use 135gr with WST in my 9 but it's an xds. Not exactly a blowback. Stinger 22lr don't have that problem in a Marlin 60 which is blowback. Beats the crap out of the buffer but cases aren't swollen.
 
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Tomme boy

Well-Known Member
It is a brass WIN case. And it is a known problem just like CW said. As he sees it in shooting steel matches. The case is fully supported when it is in battery. Pretty sure It is a timing issue as fiver has said.

Another thing that effect the timing and extraction that has not been brought up is the hammer spring. It has to be extremely heavy on these to slow the bolt from coming back. I am using a drop in cassette type trigger that PSA makes. It is rated for use in 9mm pistols and carbine. It has an extremely heavy hammer spring but a lite 3lb pull.

As to the 22 not doing it is because of the amount of case diameter. Even though they are the same psi as the 9mm it has to act on a much smaller area. And they do swell. Or get glock belly. Found lots of them over the years laying on the benches at the local shooting range.
 

popper

Well-Known Member
Stinger is the ultra high velocity 22lr. Case is longer for more powder. Pic just looks al. color.
Problem I have with your conclusion: If pressure is high enough to blow the SIDE of the case but front part isn't 'latched' into the chamber. Bullet DIDN'T exit barrel. I had a 40sw blow the head off, bullet exited and hit target good. Case was still in barrel. XDm is basically blowback with the barrel 'step' for a lock. Your powder is at the slow end of the chart. Could be part of the problem. Seen lots of PCC fired, even the 'ugly' one. No problems. Most of these guys are spray and play too. Not really my problem as I won't have one. And, yes, Mod 60 will go full auto if the disconnector is bad. At least until it jams.
 

Tomme boy

Well-Known Member
Well I went and changed over one of my presses to the 9mm. Ran a couple dummies to make sure everything was right. Hooked up the knock off of a mr bullet feeder to the bullet feed die. Turned it on and it made one revolution and stopped.

That's strange I did not put any bullets in it yet. Checked the micro switch for the feed die and that was ok.

The circuit breaker was tripped. Reset it and turn it back on. It trips again. So i take out the feed disc and nothing is in there that would bind it up. Out comes my power supply and i hooked it up and i felt it bind up. So i then hook it up in reverse. It takes off. Then stops in the same spot once it made a complete revolution.

This stopped on me a few times last year when I got it. But it never tripped the breaker. I always thought a bullet was just jammed.

Ordered a new motor and gearbox for it. 12v 10rpm 90° shaft. Should be here in a couple days. I did load 20 rounds by hand feeding the bullet die.

Seems like I always get the junk and problem child's. If this keeps up I am about ready to sell everything and just go fishing.
 

Ian

Notorious member
No, Tomme, I'm usually the one who has hell getting anything made right or to work right, new or used. Except for Lee Precision. Most of their stuff works for me, except for that stupid pro auto drum measure which is broken by design.
 

Bruce Drake

Active Member
first time I setup my AR9, I had a similar incident as well. I switched to a heavier 8oz Spikes Carbine buffer from a stock AR15 carbine buffer. in addition to the weight, its also longer and it helps with bolt jump as well.
 

Tomme boy

Well-Known Member
Got the new motor in and all is good for now. Just have to make it to the range. Loaded 50 to check with the titegroup. I made enough for the gen 4 g19 to test also. If I remember right I tried it in the block but did not like the recoil impulse.
 

Tomme boy

Well-Known Member
Well they worked. But I don't like them. With the heavier buffer they were not throwing the brass nowhere near as far as it normally does. A lot less. With 3.9gr to regroup they were going an avg of 1194fps. 16" barrel.

I think I may just try a different powder measure for unique. I was using the Lee auto disc pro withe the adjustable disc. I also have a couple of the auto drums. They work pretty well with everything I have tried so far. Other than leaking with anything ball powder.

Anyone use imr7625? I have about 2.5lbs tucked away from loading 20ga. I miss might as well use it up. Get it off the shelf.
 

Ian

Notorious member
Just use the normal disks with Unique. Titegroup is rumored to be sketchy in the nine, very sensitive to small case volume changes.
 

Bruce Drake

Active Member
Well they worked. But I don't like them. With the heavier buffer they were not throwing the brass nowhere near as far as it normally does. A lot less. With 3.9gr to regroup they were going an avg of 1194fps. 16" barrel.

I think I may just try a different powder measure for unique. I was using the Lee auto disc pro withe the adjustable disc. I also have a couple of the auto drums. They work pretty well with everything I have tried so far. Other than leaking with anything ball powder.

Anyone use imr7625? I have about 2.5lbs tucked away from loading 20ga. I miss might as well use it up. Get it off the shelf.
As long as they are fully exiting, who cares how far out they fly afterwards?