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Developing 9mm "Carry" Compensator Load. Primer Flattening, High Pressure Signs


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I'm interested in developing a load for a 9mm "carry" comp for fun but I'm looking for feedback on how much I can or should load it up.  I'm not necessarily looking to make major pf.  It would be great if it did but I'm not looking to push the limits of reliability or safety to do it. 

 

Without being able to measure chamber pressure are there other limits I should stay within?  Can I guesstimate chamber pressure with other metrics?  Based on a few of the threads I've read through I was going to start experimenting with VV 3N38 powder.

 

I'm more interested in the process than anecdotes but any feedback is appreciated.

Edited by Michael303
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1 hour ago, Michael303 said:

I'm interested in developing a load for a 9mm "carry" comp for fun but I'm looking for feedback on how much I can or should load it up.  I'm not necessarily looking to make major pf.  It would be great if it did but I'm not looking to push the limits of reliability or safety to do it. 

 

Without being able to measure chamber pressure are there other limits I should stay within?  Can I guesstimate chamber pressure with other metrics?  Based on a few of the threads I've read through I was going to start experimenting with VV 3N38 powder.

 

I'm more interested in the process than anecdotes but any feedback is appreciated.

If your "carry comp" is made with a fully supported chamber then you should be able to run 9 major, there is nothing actually special about 9 major barrels in any platform I have seen, yes some have their barrels throated to allow longer OALs but not all by any means. 

 

so process find 9 major load data on here for a bullet and OAL that will fit your magazines and plunk test in your chamber, back off the load and work your way up to where you want to be, about the only way to estimate pressure is to watch for primer flattening, if that starts getting silly then so is your pressure. 

 

 

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Based on this thread you've been reloading for a grand total of three weeks: 


It's not clear whether you even own a chrono yet.  I would not advise you to flirt with 9 major loads, especially if you're planning to run this in a plastic mass production gun like the Gen 5 Glock you've been posting about.  A burst case in a plastic wonder nine tends to direct the energy down into your palm instead of up out the ejection port. It's a riskier endeavor.

Plotting your velocities vs charge weight is an important aspect of pushing the limits in reloading. At some point the slope changes and you start getting less bang for your buck.  Reading primers and case head deformation can be important too.

I'm not sure what you're trying to accomplish. Do you just want a louder gun? Do you want more points hitting C's and D's?  Many modern guns can handle shooting 9 major for a couple shots, but any steady diet and they take a beating from loser tolerances over something built for the purpose.  I've been on multiple stages where the open Glock shooter's slide has cracked. It's usually just under the extractor.

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30 minutes ago, MikeBurgess said:

If your "carry comp" is made with a fully supported chamber then you should be able to run 9 major, there is nothing actually special about 9 major barrels in any platform I have seen, yes some have their barrels throated to allow longer OALs but not all by any means. 

 

so process find 9 major load data on here for a bullet and OAL that will fit your magazines and plunk test in your chamber, back off the load and work your way up to where you want to be, about the only way to estimate pressure is to watch for primer flattening, if that starts getting silly then so is your pressure. 

 

 

 

Thanks for the reply and I appreciate the direction.  This should be a great starting point now that I know what I'm looking for.

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18 hours ago, belus said:

Based on this thread you've been reloading for a grand total of three weeks: 


It's not clear whether you even own a chrono yet.  I would not advise you to flirt with 9 major loads, especially if you're planning to run this in a plastic mass production gun like the Gen 5 Glock you've been posting about.  A burst case in a plastic wonder nine tends to direct the energy down into your palm instead of up out the ejection port. It's a riskier endeavor.

Plotting your velocities vs charge weight is an important aspect of pushing the limits in reloading. At some point the slope changes and you start getting less bang for your buck.  Reading primers and case head deformation can be important too.

I'm not sure what you're trying to accomplish. Do you just want a louder gun? Do you want more points hitting C's and D's?  Many modern guns can handle shooting 9 major for a couple shots, but any steady diet and they take a beating from loser tolerances over something built for the purpose.  I've been on multiple stages where the open Glock shooter's slide has cracked. It's usually just under the extractor.

 

Thanks for the feedback on diminishing velocity.  I do own a chrono, thanks for asking.  Do you have a lot of experience working up 9 major?  I only ask because you seem to be classified in Prod and SS but not Open?

 

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38 minutes ago, Michael303 said:

 

Thanks for the feedback on diminishing velocity.  I do own a chrono, thanks for asking.  Do you have a lot of experience working up 9 major?  I only ask because you seem to be classified in Prod and SS but not Open?

 

I don't shoot open, that's true. My beyond book loads are limited to rifles.

We regularly get people asking about 9 major with limited reloading experience and I've been here long enough to see multiple iterations on this question. Your post threw red flags because you didn't mention the gun model or bullet weight, and you expressly discounted making major. That reminded me of this older discussion where someone put a comp on their G19 and then thought major would be fun. Your post history only references Glocks and I've personally seen two open Glocks shoot themselves apart.

 

So what are you trying to accomplish? If it's just a harsher recoil, look it up in a book and find a powder with high velocity 115gr bullets. But its your gun and your hands, we can only offer guidance.

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Posted (edited)
2 hours ago, belus said:

I don't shoot open, that's true. My beyond book loads are limited to rifles.

We regularly get people asking about 9 major with limited reloading experience and I've been here long enough to see multiple iterations on this question. Your post threw red flags because you didn't mention the gun model or bullet weight, and you expressly discounted making major. That reminded me of this older discussion where someone put a comp on their G19 and then thought major would be fun. Your post history only references Glocks and I've personally seen two open Glocks shoot themselves apart.

 

So what are you trying to accomplish? If it's just a harsher recoil, look it up in a book and find a powder with high velocity 115gr bullets. But its your gun and your hands, we can only offer guidance.

 

Thanks for the follow up.  I'm looking to optimize the performance of the comp.  Per my original post though, the priority is on safety and reliability and not necessarily making major PF.  As I mentioned originally, I'm more interested in the process and metrics of working up a "beyond book" load as you called it.   I wouldn't be surprised if the returns started to diminish on the performance of a smallish comp on a G19 before major PF was reached anyway.

 

Based on what's been mentioned, is it expected that I'd start seeing primer flattening and flowing well before making major?  Is any flattening acceptable?  

 

Edit to add: My uneducated guess is that a cracked slide, like you mentioned, would more likely come from being undersprung rather than higher chamber pressure.  Is this reasoned or off base?  This is digressing from the original post a bit but I'm interested in learning more here.

Edited by Michael303
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I was chatting with my buddy about this topic and he pointed out the Vihtavuori has load data with 3N38 and a 147gr projectile that meets major pf.

 

https://www.vihtavuori.com/reloading-data/handgun-reloading/?cartridge=89#content:~:text=3N38 0%2C41 6.3 357 1171 0%2C45 6.9 368 1207

 

My understanding is their load data meets CIP specs so that's not even plus P pressure.  Someone correct me if I'm wrong.

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47 minutes ago, Michael303 said:

I was chatting with my buddy about this topic and he pointed out the Vihtavuori has load data with 3N38 and a 147gr projectile that meets major pf.

 

https://www.vihtavuori.com/reloading-data/handgun-reloading/?cartridge=89#content:~:text=3N38 0%2C41 6.3 357 1171 0%2C45 6.9 368 1207

 

My understanding is their load data meets CIP specs so that's not even plus P pressure.  Someone correct me if I'm wrong.

This is true. It's not as hard to get to major with a 147gr projectile. I think there may be some legacy defensive loads that qualified or were close (147gr Black Talon +P? I don't recall). It's generally not the direction taken with a compensator though.  Open gun theory is based on producing a lot of gas that holds the gun down and locked, accomplished by using as much powder mass as possible. High powder masses are only safely accomplished with slow burning powders. Find a powder that burns slow enough to be safe but fast enough to move the bullet up to velocity, all while fitting in the volume available in a 9x19 case is the name of the game. It's a lot easier in the higher volume 38 super case which is why you still see people building super guns.

(don't take this image as loads, I think these are 9x19 cases, but I'm not sure)
JXiPsuO.png

 

7 hours ago, Michael303 said:

Based on what's been mentioned, is it expected that I'd start seeing primer flattening and flowing well before making major?  Is any flattening acceptable?  

 

Edit to add: My uneducated guess is that a cracked slide, like you mentioned, would more likely come from being undersprung rather than higher chamber pressure.  Is this reasoned or off base?  This is digressing from the original post a bit but I'm interested in learning more here.

I thought there was an old Front Sight article that showed this in more detail but I can't find it in back issues.

There are a number of signs in the brass that indicate you're reaching the limits of the load in that specific gun. Which shows up first varies as well. Primers are probably the easiest to watch because they're usually more consistent than mixed 9mm range brass. A normal pressure powder will have rounded edges like an unfired primer. As pressure grows, the corners of the primer flow into the pocket more. At the same time, in some guns with a larger firing pin hole, the primer also flows back into the firing pin leaving a small protruding nipple.  The primer might flow so much that it ruptures into the firing pin hole.  Marginally flattened primers are generally accepted as the limit you want to stop load development for that powder/bullet/oal combo.

You should also keep track of head stamp when working up beyond book loads and measure expansion of the case at the base. If your chamber isn't well supported you might start to see excessive pressure signs through case head expansion first. I don't have a measure of acceptable base expansions. A bulge appearing in your case web indicates to me that the barrel in that gun can't handle the development. You'd only be a bad piece of brass away from a burst.

Finally, shooting your load development over a chrono will help you recognize when the velocity/charge starts to go non-linear. This is sign that your continued search will be fruitless and that your chamber pressure are becoming erratic. The primers should warn you about this before hand, but its smart to monitor more than one effect.

Finally, production guns aren't as durable in the face of these loads as something custom or at minimum hand fitted. Tolerance stacking can lead to the slide accelerating into the locking lugs and battering the surfaces. I think this is the orgin of the cracked Glock slides I've seen. The comp holds the front of the barrel down and keeps the gun locked longer. I think this higher pressure and, to borrow a rifle term, "bolt thrust", all supported by the thinnest area of the slide under the extractor and instigates the cracks there. Cracks are stress concentrators based on how sharp/blunt they are. The bluntest crack (a round hole) still concentrates stress by a factor of 3x.

Plastic guns also don't contain the force of a burst case as well as the metal ones. The gas is generally directed down the feed ramp towards the magazine and between the shooter's hands. In contrast, the weak point on a 2011/1911 open gun is out the ejection port which is much safer if you have a catastrophic failure.

In a purpose built gun you can develop loads faster with some trust on the smith's reputation and experience. The tighter fit tolerances will prevent battering and keep it running longer too. But developing a max load for a production gun should be pursued with a bit more care.

edit: Oh yeah, make a note of what temperature you develop this load at. You'll want to know whether your powder is temperature sensitive and whether it gets faster or slower when hotter or colder; usually faster when hotter, but some are backwards. Your loads might become unsafe if you develop them in a ND winter and then shoot in an AZ summer.

These are all fine. The right one is pretty flat and should be your limit.
UUlVzYK.png

The nipple with firing pin wipe from a gun that might unlock a little too early. You definitely want to stay below this point.
O1F3hvU.jpg

Punctures.
uM0bnAL.jpg

Chamber support, it's all in degrees but watch for the brass flowing into this unsupported area:
sG7lqrp.png

Tracking velocity vs charge weight:
wzKmu35.png

 

Edited by belus
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Posted (edited)
14 hours ago, belus said:

This is true. It's not as hard to get to major with a 147gr projectile. I think there may be some legacy defensive loads that qualified or were close (147gr Black Talon +P? I don't recall). It's generally not the direction taken with a compensator though.  Open gun theory is based on producing a lot of gas that holds the gun down and locked, accomplished by using as much powder mass as possible. High powder masses are only safely accomplished with slow burning powders. Find a powder that burns slow enough to be safe but fast enough to move the bullet up to velocity, all while fitting in the volume available in a 9x19 case is the name of the game. It's a lot easier in the higher volume 38 super case which is why you still see people building super guns.

(don't take this image as loads, I think these are 9x19 cases, but I'm not sure)
JXiPsuO.png

 

I thought there was an old Front Sight article that showed this in more detail but I can't find it in back issues.

There are a number of signs in the brass that indicate you're reaching the limits of the load in that specific gun. Which shows up first varies as well. Primers are probably the easiest to watch because they're usually more consistent than mixed 9mm range brass. A normal pressure powder will have rounded edges like an unfired primer. As pressure grows, the corners of the primer flow into the pocket more. At the same time, in some guns with a larger firing pin hole, the primer also flows back into the firing pin leaving a small protruding nipple.  The primer might flow so much that it ruptures into the firing pin hole.  Marginally flattened primers are generally accepted as the limit you want to stop load development for that powder/bullet/oal combo.

You should also keep track of head stamp when working up beyond book loads and measure expansion of the case at the base. If your chamber isn't well supported you might start to see excessive pressure signs through case head expansion first. I don't have a measure of acceptable base expansions. A bulge appearing in your case web indicates to me that the barrel in that gun can't handle the development. You'd only be a bad piece of brass away from a burst.

Finally, shooting your load development over a chrono will help you recognize when the velocity/charge starts to go non-linear. This is sign that your continued search will be fruitless and that your chamber pressure are becoming erratic. The primers should warn you about this before hand, but its smart to monitor more than one effect.

Finally, production guns aren't as durable in the face of these loads as something custom or at minimum hand fitted. Tolerance stacking can lead to the slide accelerating into the locking lugs and battering the surfaces. I think this is the orgin of the cracked Glock slides I've seen. The comp holds the front of the barrel down and keeps the gun locked longer. I think this higher pressure and, to borrow a rifle term, "bolt thrust", all supported by the thinnest area of the slide under the extractor and instigates the cracks there. Cracks are stress concentrators based on how sharp/blunt they are. The bluntest crack (a round hole) still concentrates stress by a factor of 3x.

Plastic guns also don't contain the force of a burst case as well as the metal ones. The gas is generally directed down the feed ramp towards the magazine and between the shooter's hands. In contrast, the weak point on a 2011/1911 open gun is out the ejection port which is much safer if you have a catastrophic failure.

In a purpose built gun you can develop loads faster with some trust on the smith's reputation and experience. The tighter fit tolerances will prevent battering and keep it running longer too. But developing a max load for a production gun should be pursued with a bit more care.

edit: Oh yeah, make a note of what temperature you develop this load at. You'll want to know whether your powder is temperature sensitive and whether it gets faster or slower when hotter or colder; usually faster when hotter, but some are backwards. Your loads might become unsafe if you develop them in a ND winter and then shoot in an AZ summer.

These are all fine. The right one is pretty flat and should be your limit.
UUlVzYK.png

The nipple with firing pin wipe from a gun that might unlock a little too early. You definitely want to stay below this point.
O1F3hvU.jpg

Punctures.
uM0bnAL.jpg

Chamber support, it's all in degrees but watch for the brass flowing into this unsupported area:
sG7lqrp.png

Tracking velocity vs charge weight:
wzKmu35.png

 

 

Thanks for taking the time to put that all together.  I'm sure a lot of this info can be found in previous posts if you know what you're looking for but it's great to have it all in one place, especially if you don't know what you don't know.  I'm sure other newbies will find it helpful going forward.  

 

I appreciate the granular detail on reading primers.  I've noticed the firing pin wipe on cases I've picked up at the range but it never occurred to me what it was.

 

This all did remind me of a recent video on the Atlas Gunworks YT channel where the owner explained how hard 9 major is on all guns, how much time they spend answering questions on the subject, and how they'd like to see major power factor lowered to the 145-150 range.  Doing that would certainly make Open more reliable and less expensive.

 

 

Thanks again for the knowledge.

Edited by Michael303
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  • Michael303 changed the title to Developing 9mm "Carry" Compensator Load. Primer Flattening, High Pressure Signs

One thing to keep in mind is that your Glock "carry gun" only has a small one or two port comp. Open guns have 4 -8 big ports or more. Your small comp will be over powdered long before you get to a 9 major load.  Building a load that has more gas then your comp can use will only result in more recoil and broken parts. A test you can do with your gun is to shoot a USPSA target with the muzzle 2"-3" from the cardboard and see if the cardboard rips from the gas or is there just a bullet hole. If the cardboard rips your load is over powering the comp. An efficient comp and load combination  will have 85%-90% of the gas being used in the port of the comp.  Loading more powder to generate more gas then the comp can use efficiently will be wasted out the front of the comp.  So you should be looking at a medium slow burning powder. Powders you should be looking at: N330, WSF, BE-86, N340.  It's not velocity of the bullet you are looking for it's the gas produced to reduce the muzzle rise. Lets look at 1070fps - 1180fps with a 115gn bullet. A faster burning target powder will get you there with about 4.0gn - 4.5gn of powder, with the medium slow burning powder will get you there with about 4.8gn - 5.4gn of powder to get the same bullet FPS. The slower burning powders are using more powder to do the same work. you get the idea. The Slow burning powders that are typically used in an open gun will burn dirty at the lower charge weights that you would use, at the higher charge weights most of the gas will be going out the muzzle.

Edited by CZ85Combat
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Primers don't always show signs of pressure...these once fired Browning cases failed early in 9mm load development...other brands went well beyond this load with no problems...pays to sort and test...

20200823_114933-1.jpg

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On 8/23/2020 at 12:59 PM, PhotoRecon said:

Primers don't always show signs of pressure...these once fired Browning cases failed early in 9mm load development...other brands went well beyond this load with no problems...pays to sort and test...

20200823_114933-1.jpg

Ummm...Browning brass...???

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14 hours ago, PhotoRecon said:

Yes, Browning factory ammo and those marks on the head are supposed to be antlers...the brass is supposedly made for them by Winchester...

I'd be curious to see how well supported that barrel is.

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Czechmate fired single shot with no mag in gun...inspection of brass not yet fired shows weak construction right were these failed...wasn't even to SAAMI max when these failed...

 

1000s fired with other brass at much much higher power with no problemo...

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