Apparent over pressure from mild load

[BongEyes]

G'day all

Im scratching my head on this one. Need some assistance.

Running a 6.5 PRC
28" Custom barrel SAAMI Chamber (.533 web)
on tikka t3 action.

153.5 Berger Hybrid Target
ADI 2217 (H1000) at 50.5grn (4.5grn below book max)
Surplus Indian Army LRP
Norma Brass trimmed to 2.015"
Loaded neck OD = .2935
Shoulder bumped back 0.002" after full length resize using SAC bushing die and mandrel
COAL 3.05"
Approx 25 thou jump to lands
Case capacity measured to 70.5grn h20

Velocity measured to 2915fps via Xero chrono which is super fast at this charge weight according to the book...
Using GRT this load is showing a pretty mild pressure curve...and certainly well below max


But, I have been getting excessive pressure signs; from the minimum charge upto 52.5grn
Heavy bolt lift/clickers
Cratered primers
Blown primer x2 once with a stuck case and torn rim from extractor claw
Ejector swipes
Primer pockets lose/unuseable after 2 firings on some pieces of brass.

Before you crucify me for running over pressure I have tried 2 different bullets and 2 different powders starting low and working higher. All showing signs of OP. 50.5grn has been fairly stable except for the clickers.

Really the only other variable to change is the brass (I've heard Norma can be very hit/miss on its QC and often produces soft brass) and I am heavily leaning towards this as the problem I am facing and wondering if anyone else thinks could be the issue...
However it dosnt explain the vast increase in velocity I am recording compared to what the book is saying...

Any insight on wtf is going wrong with this would be helpful. I have thought of everything I know and will be first to admit I don't know everything.

 

[RegionRat]

I realize it may be difficult to obtain any factory ammo for your rifle, but if you had a factory ammo for a reference load, you would at least know which part of the troubleshooting to investigate.

If that isn't possible due to the rarity of factory 6.5 PRC ammo, then I would inspect the bore and chamber. See if the barrel and chamber are really to the correct specs and also take a look to make sure it isn't copper fouled.

Any decent gunsmith should be able to cast the chamber and throat and also slug the bore and look for fouling.

Velocity (muzzle energy) is a direct clue to the pressure and when it is too high then so is the pressure. Good Luck and in for the reports.

 

[KnowNothing256]

How long is the barrel in the load data? Agreed that you seem to have a pressure issue, but it's possible that your high MV could just be due to extra barrel length, and the pressure signs are another issue.

Other possibilities I can think of:
- Lube on the cases leading to slippage (might not explain the blown primers)
- Carbon ring inhibiting initial bullet movement (spikes initial pressure)
- Tight bore (increases entire pressure curve)
- Incorrect powder weights due to scale reading incorrectly
- Primers are too hot (I'm skeptical of this, but it's possible)

 

[BobinNC]

ADI powder equivalent's are only accurate to within 5% (or 2.5 grains in your case)

Powder equivalents

This chart shows ADI 2217 as being slower than H-1000

Relative Burn Rates​

In other works there is no clear answer as to whether ADI -2217 is exactly the same as H-1000.

 

[Maurygold]

you're 300 FPS too fast for that load. something is up with the barrel/ throat/ chamber

Agree with the above - get a factory round and shoot it to confirm this is the case and it shoots several hundred FPS over the boox rec.

but also - get real primers for the future (this is not causing the issue though)

 

[918v]

What is the fired neck diameter?

 

[BongEyes]

Really appreciate all the replies so far. Hopefully I can get to the bottom of this with every ones help...

I realize it may be difficult to obtain any factory ammo for your rifle, but if you had a factory ammo for a reference load, you would at least know which part of the troubleshooting to investigate.

If that isn't possible due to the rarity of factory 6.5 PRC ammo, then I would inspect the bore and chamber. See if the barrel and chamber are really to the correct specs and also take a look to make sure it isn't copper fouled.

Any decent gunsmith should be able to cast the chamber and throat and also slug the bore and look for fouling.

Velocity (muzzle energy) is a direct clue to the pressure and when it is too high then so is the pressure. Good Luck and in for the reports.

My initial 20 rounds were from a box of factory Norma Whitetail 140gr soft point, used for breaking in the barrel and sighting in the scope.
Box velocity is listed at 2887 FPS (I assume 24" barrel)
I got a solid 3000fps average from the entire box of 20.
I cant say that these rounds "felt" right from the sound of firing to the feel of the recoil and even the slightly heavy bolt lift. It definitely felt odd to me. Looking back at the fired cases there is evidence of ejector swipe on the head stamps. I had not noticed this prior to just now.
Measurements of these cases are
AVG fired neck OD 0.297
AVG fired OD at web 0.533
AVG fired OAL 2.025
Unfortunately the gunsmith who built the rifle for me has been far less than helpful (practically useless) at trying to help me fix this issue. But I agree, I think casting the chamber and throat would be a good idea.

As for fouling, I have a pretty good cleaning regime. I usually clean every 50-100 rounds with good quality chemicals and equipment. I am mindful to work on the throat to avoid carbon rings, although I have no borescope to confirm this - I am fairly certain there wouldn't be a carbon ring present (I could very well be wrong of course)

How long is the barrel in the load data? Agreed that you seem to have a pressure issue, but it's possible that your high MV could just be due to extra barrel length, and the pressure signs are another issue.

Other possibilities I can think of:
- Lube on the cases leading to slippage (might not explain the blown primers)
- Carbon ring inhibiting initial bullet movement (spikes initial pressure)
- Tight bore (increases entire pressure curve)
- Incorrect powder weights due to scale reading incorrectly
- Primers are too hot (I'm skeptical of this, but it's possible)

Load data barrel is 24"

-I use Redding die wax, and always make sure to wipe the excess after resizing. I clean the chamber of any excess oils before firing and store my guns muzzle down so nothing creeps back into the chamber. I am pretty good when it comes to this.
-Carbon ring could be a real possibility... I am good with rifle cleaning and maintenance but don't own a borescope so cannot confirm that it exists or not... I think I will have to take to gunsmith to take a look.
-Tight bore is also something I would have to take to gunsmith to inspect.
-I did think about the scales being incorrect, but the level of powder in the case leads me to believe it isn't throwing too much powder. I have used these scales for many years and trust them. BUT I will check them just in case.
-Hot primers did also cross my mind, and they are an unusual purchase for me as Id usually use CCI br2 or br4 primers but these days with components I have to get what I can take. Funnily enough under initial testing I have had really low and consistent S.D's which leads me to believe they are ok?

ADI powder equivalent's are only accurate to within 5% (or 2.5 grains in your case)

Powder equivalents

This chart shows ADI 2217 as being slower than H-1000

Relative Burn Rates​

In other works there is no clear answer as to whether ADI -2217 is exactly the same as H-1000.

Those are some useful links Bobin, thanks for sharing.
I know that 2217 and H1000 aren't exactly the same but fairly similar. The data I am working with is listed straight from ADI's website at 49.5 min to 55.0 max with a 153 grain bullet.
H1000 was just for reference because Im not sure too many people would understand what I am talking about if I said AR2217.

you're 300 FPS too fast for that load. something is up with the barrel/ throat/ chamber

Agree with the above - get a factory round and shoot it to confirm this is the case and it shoots several hundred FPS over the boox rec.

but also - get real primers for the future (this is not causing the issue though)

I agree, something is definitely wrong.
As above, factory rounds through my rifle were ~115 fps faster than box. Assuming the box data is based on a 24" barrel that seems like a fairly normal increase for a 28" barrel?
Primers are subject to availability... Where I live, there is little demand for shooting components so we tend to get everything last. Im trying to make the best out of what I can obtain.

What is the fired neck diameter?

Factory loaded brass 0.2965 to 0.297
My handloads 2x fired and annealed 0.296 to 0.2965


Seems like the next logical step is to have bore inspected for carbon ring, and the chamber/throat inspected and cast...

 

[RegionRat]

My initial 20 rounds were from a box of factory Norma Whitetail 140gr soft point, used for breaking in the barrel and sighting in the scope.
Box velocity is listed at 2887 FPS (I assume 24" barrel)
I got a solid 3000fps average from the entire box of 20.
I cant say that these rounds "felt" right from the sound of firing to the feel of the recoil and even the slightly heavy bolt lift. It definitely felt odd to me. Looking back at the fired cases there is evidence of ejector swipe on the head stamps. I had not noticed this prior to just now.
Measurements of these cases are
AVG fired neck OD 0.297
AVG fired OD at web 0.533
AVG fired OAL 2.025
Unfortunately the gunsmith who built the rifle for me has been far less than helpful (practically useless) at trying to help me fix this issue. But I agree, I think casting the chamber and throat would be a good idea.

As for fouling, I have a pretty good cleaning regime. I usually clean every 50-100 rounds with good quality chemicals and equipment. I am mindful to work on the throat to avoid carbon rings, although I have no borescope to confirm this - I am fairly certain there wouldn't be a carbon ring present (I could very well be wrong of course)

Ok, so based on having a higher than expected speed out of the gate, with both factory and your own loads, along with the bolt lift and swipe comments, I would have to guess that the rifle will have to be further investigated.

Depending on what is found, it doesn't necessarily mean you have to scrap the bbl, however it might mean you will have to live with a slightly lower charge as a general approach. The fact that two different bullet brands, Norma and Berger, both gave similar results in terms of the pressure, means that it is likely the rifle.

(Put a Teslong borescope on your list... )

Just curious... do you know where the gunsmith got this bbl?
Have you ever done a casting, or slugged rifle?
If not, is there someone other than that uncooperative smithy that can help you?

 

[Im2bent]

Are you not getting the velocity you want with a charge that does not have pressure signs? You are getting pressure but also higher than expected velocity?

 

[Maurygold]

Are you not getting the velocity you want with a charge that does not have pressure signs? You are getting pressure but also higher than expected velocity?

Something is wrong. Reducing load to get the desired result will most likely lead to some other issue.

I’d send the gun back to manufacturer or math yo inspect. There’s something wrong

 

[Ledzep]

Ever cleaned carbon fouling out?

If you have more than 75-100 rounds since the last carbon cleaning I'd start there.

 

[straightshooter1]

G'day all

Im scratching my head on this one. Need some assistance.

Running a 6.5 PRC
28" Custom barrel SAAMI Chamber (.533 web)
on tikka t3 action.

153.5 Berger Hybrid Target
ADI 2217 (H1000) at 50.5grn (4.5grn below book max)
Surplus Indian Army LRP
Norma Brass trimmed to 2.015"
Loaded neck OD = .2935
Shoulder bumped back 0.002" after full length resize using SAC bushing die and mandrel
COAL 3.05"
Approx 25 thou jump to lands
Case capacity measured to 70.5grn h20

Velocity measured to 2915fps via Xero chrono which is super fast at this charge weight according to the book...
Using GRT this load is showing a pretty mild pressure curve...and certainly well below max


But, I have been getting excessive pressure signs; from the minimum charge upto 52.5grn
Heavy bolt lift/clickers
Cratered primers
Blown primer x2 once with a stuck case and torn rim from extractor claw
Ejector swipes
Primer pockets lose/unuseable after 2 firings on some pieces of brass.

Before you crucify me for running over pressure I have tried 2 different bullets and 2 different powders starting low and working higher. All showing signs of OP. 50.5grn has been fairly stable except for the clickers.

Really the only other variable to change is the brass (I've heard Norma can be very hit/miss on its QC and often produces soft brass) and I am heavily leaning towards this as the problem I am facing and wondering if anyone else thinks could be the issue...
However it dosnt explain the vast increase in velocity I am recording compared to what the book is saying...

Any insight on wtf is going wrong with this would be helpful. I have thought of everything I know and will be first to admit I don't know everything.

You said your "GRT is showing a pretty mild pressure curve" and so does my QL app. In fact, the curve is VERY low. While you say you're at "minimum charge up to 53.5 gr", that "minimum is based on who's reported minimum charge and case volume? Norma case volumes are 3-4 grs more in volume than other brands, so you could be well below recommended minimum case charge??? And, as I look at the powder charge of 50.5 grs ADI 2217 in my QL app, it's showing the case filled to only 85.5% (given your reported case volume). Case fill that low would give me concern for high pressure spikes, which is known to happen with a very low case fill. This may not be "THE" factor going on, but I have a feeling it's contributing a lot to it.

For my 153.5's in my PRC, I've never used H1000 or ADI AR 2217. I like to run 57.5 gr N565 behind 153.5's producing 2,980 fps out of a 26" barrel. But I've often seen reports for charges of ~57 grs of H1000 producing around 2900 fps. That why what you're reporting is a little shocking to me. My QL app shows a 50.5 grs of ADI AR 2217 produce ~ 2500 fps and ~50 fps more with case volumes reduced to what I get with my thicker case wall Lapua brass. I just can't imagine 400 fps difference that you're getting without something causing an unusually high pressure spike.

 

[918v]

Given you have plenty of clearance I’d be looking at those primers as they are prolly made from recycled bottle caps.

 

[BongEyes]

Just an update for those who are following, and again thanks so much for all your replies.

Took the barrelled action into the gunsmith today, along with some loaded ammo, fired brass from both my hand loads and factory loads.

-He measured everything with a micrometre, agreeing that there was (obvious) excessive pressure with the brass.
-He agreed dimensions of loaded rounds seemed normal and within specifications.
-He will pull some bullets from the loaded rounds and weigh the powder charges on his own scales to confirm my scales aren't the culprit.
-He will reset neck tension with a bushing die and reload these rounds with a different primer to confirm if it is a primer issue or not.
-He thinks that these primers are most likely causing the issue.
-He will then test fire the re-reloaded rounds to check for pressure signs again, and also chronograph the projectiles via magnetospeed.
-If primers are found to be an issue then that should offer a solution.
-He has agreed to cast the chamber and slug the bore to make sure it isn't a mechanical or dimensional issue with the rifle.

I have asked him to order in an AW2 reamer and open up the back end of the chamber for preventing clickers in the future.

Hopefully everything works out and it is something as simple as a primer.

Ok, so based on having a higher than expected speed out of the gate, with both factory and your own loads, along with the bolt lift and swipe comments, I would have to guess that the rifle will have to be further investigated.

Depending on what is found, it doesn't necessarily mean you have to scrap the bbl, however it might mean you will have to live with a slightly lower charge as a general approach. The fact that two different bullet brands, Norma and Berger, both gave similar results in terms of the pressure, means that it is likely the rifle.

(Put a Teslong borescope on your list... )

Just curious... do you know where the gunsmith got this bbl?
Have you ever done a casting, or slugged rifle?
If not, is there someone other than that uncooperative smithy that can help you?

A borescope has been on my wish list for some time... I just don't know if it will do my OCD any good but after all this I think visually confirming there are no carbon rings is going to be part of my regular maintenance.

Are you not getting the velocity you want with a charge that does not have pressure signs? You are getting pressure but also higher than expected velocity?

I am getting pressure signs no matter the charge. At minimum charge they are minor- but still there. And the velocity is much higher than expected.
I don't want to go below minimum due to risk of detonation.

Ever cleaned carbon fouling out?

If you have more than 75-100 rounds since the last carbon cleaning I'd start there.

Yep, it's part of my cleaning regime. Gunsmith will borescope the rifle to confirm there is no carbon ring but I get these pressure signs if rifle is clean or fouled.

You said your "GRT is showing a pretty mild pressure curve" and so does my QL app. In fact, the curve is VERY low. While you say you're at "minimum charge up to 53.5 gr", that "minimum is based on who's reported minimum charge and case volume? Norma case volumes are 3-4 grs more in volume than other brands, so you could be well below recommended minimum case charge??? And, as I look at the powder charge of 50.5 grs ADI 2217 in my QL app, it's showing the case filled to only 85.5% (given your reported case volume). Case fill that low would give me concern for high pressure spikes, which is known to happen with a very low case fill. This may not be "THE" factor going on, but I have a feeling it's contributing a lot to it.

For my 153.5's in my PRC, I've never used H1000 or ADI AR 2217. I like to run 57.5 gr N565 behind 153.5's producing 2,980 fps out of a 26" barrel. But I've often seen reports for charges of ~57 grs of H1000 producing around 2900 fps. That why what you're reporting is a little shocking to me. My QL app shows a 50.5 grs of ADI AR 2217 produce ~ 2500 fps and ~50 fps more with case volumes reduced to what I get with my thicker case wall Lapua brass. I just can't imagine 400 fps difference that you're getting without something causing an unusually high pressure spike.

-The load data I am using is directly from ADI's website for 6.5 PRC using AR2217 and a 153 grain bullet. There is nothing on there that I can see which stipulates the case volume of their test round.
-I see your point on having potentially too little of a case fill for the volume of my cases. However even with more powder in the case there are still pressure signs and in fact they get worse as the charge increases. Although I totally agree it is not ideal, do you believe 85.5% fill to be dangerously low?
-I have tested loads with this powder upto 54.5 grain which yielded avg speed of 2980fps although the accuracy was not there. And a little too fast for my needs. This speed exceeds the book maximum by 180fps using .5 less powder!
-With ADI's load data minimum charge of 49.5 can expect velocities of 2560fps. I'd hazard a guess that at 50.5 one might see around the vicinity of 2630fps. +or- 30fps
-The additional 300 FPS I am getting from this for sure is worrying, and why I am trying to get to the bottom of it. The more I am reading and learning the more I am starting to lean toward the primers being too spicy and coupled with the relatively low powder charge causing the powder to burn suddenly and unevenly... more like a sudden boom rather than a slower but steady push.

Given you have plenty of clearance I’d be looking at those primers as they are prolly made from recycled bottle caps.

918v I agree mate. Those Indians are certainly industrious little fellas but unfortunately their motto is quantity over quality.
Fingers crossed the federal primers the gunsmith will test with can shed some light...

 

[Maurygold]

Just an update for those who are following, and again thanks so much for all your replies.

Took the barrelled action into the gunsmith today, along with some loaded ammo, fired brass from both my hand loads and factory loads.

-He measured everything with a micrometre, agreeing that there was (obvious) excessive pressure with the brass.
-He agreed dimensions of loaded rounds seemed normal and within specifications.
-He will pull some bullets from the loaded rounds and weigh the powder charges on his own scales to confirm my scales aren't the culprit.
-He will reset neck tension with a bushing die and reload these rounds with a different primer to confirm if it is a primer issue or not.
-He thinks that these primers are most likely causing the issue.
-He will then test fire the re-reloaded rounds to check for pressure signs again, and also chronograph the projectiles via magnetospeed.
-If primers are found to be an issue then that should offer a solution.
-He has agreed to cast the chamber and slug the bore to make sure it isn't a mechanical or dimensional issue with the rifle.

I have asked him to order in an AW2 reamer and open up the back end of the chamber for preventing clickers in the future.

Hopefully everything works out and it is something as simple as a primer.



A borescope has been on my wish list for some time... I just don't know if it will do my OCD any good but after all this I think visually confirming there are no carbon rings is going to be part of my regular maintenance.




I am getting pressure signs no matter the charge. At minimum charge they are minor- but still there. And the velocity is much higher than expected.
I don't want to go below minimum due to risk of detonation.



Yep, it's part of my cleaning regime. Gunsmith will borescope the rifle to confirm there is no carbon ring but I get these pressure signs if rifle is clean or fouled.



-The load data I am using is directly from ADI's website for 6.5 PRC using AR2217 and a 153 grain bullet. There is nothing on there that I can see which stipulates the case volume of their test round.
-I see your point on having potentially too little of a case fill for the volume of my cases. However even with more powder in the case there are still pressure signs and in fact they get worse as the charge increases. Although I totally agree it is not ideal, do you believe 85.5% fill to be dangerously low?
-I have tested loads with this powder upto 54.5 grain which yielded avg speed of 2980fps although the accuracy was not there. And a little too fast for my needs. This speed exceeds the book maximum by 180fps using .5 less powder!
-With ADI's load data minimum charge of 49.5 can expect velocities of 2560fps. I'd hazard a guess that at 50.5 one might see around the vicinity of 2630fps. +or- 30fps
-The additional 300 FPS I am getting from this for sure is worrying, and why I am trying to get to the bottom of it. The more I am reading and learning the more I am starting to lean toward the primers being too spicy and coupled with the relatively low powder charge causing the powder to burn suddenly and unevenly... more like a sudden boom rather than a slower but steady push.


918v I agree mate. Those Indians are certainly industrious little fellas but unfortunately their motto is quantity over quality.
Fingers crossed the federal primers the gunsmith will test with can shed some light...

Is he the one who cut the custom barrel? What barrel manufacturer?

I’d be hard pressed to ever slug a barrel.

 

[Emerson0311]

Way over pressured with factory ammo? Gunsmith issue. My guess is the messing around with the reloads talk is him covering his mistake. Unless he doesn’t know wtf how to fix it, and its the same when you get it back.

Edit: unless the bore is too tight. Was it ordered that way? Who made the barrel? What are the specs? It’s almost like these basic questions would sort this stuff out…

 

[BongEyes]

Is he the one who cut the custom barrel? What barrel manufacturer?

I’d be hard pressed to ever slug a barrel.

He is the gunsmith who did the work, yes.
The barrel is made by TSE- Australia. Same make as the previous barrel I had on this action (it was in .308) and work also done by same gunsmith. Was exceptionally accurate and reliable, could not fault the barrel or workmanship on that barrel.

Curious as to why you wouldn't want to slug a barrel? Can it damage?

 

[DstRflMn645]

In post #7 you state that fired neck diameter is .297 and that fired brass is .2965-.297, your problem is not enough neck clearance. Neck clearance should be around .002 minimum. A quick check would be to take a fired case and see if a new bullet will slide into the neck, if it won't your neck is too tight.

John

 

[918v]

In post #7 you state that fired neck diameter is .297 and that fired brass is .2965-.297, your problem is not enough neck clearance. Neck clearance should be around .002 minimum. A quick check would be to take a fired case and see if a new bullet will slide into the neck, if it won't your neck is too tight.

John

His fired brass is .297” and his loaded neck is .2935” per the OP.

 

[straightshooter1]

-The load data I am using is directly from ADI's website for 6.5 PRC using AR2217 and a 153 grain bullet. There is nothing on there that I can see which stipulates the case volume of their test round.

Since manuals for powder charges will use case volumes that's typically used, especially those from powder suppliers, your Norma cases hold substantially more. If you were using a data from Norma, then I'd feel more comfortable. If you're at minimum charge and you're cases have 3-4 grs more case volume, then that's a problem; not so much using the max charge number.

-I see your point on having potentially too little of a case fill for the volume of my cases. However even with more powder in the case there are still pressure signs and in fact they get worse as the charge increases. Although I totally agree it is not ideal, do you believe 85.5% fill to be dangerously low?

I wouldn't think it's "dangerously" low. But it's effects are not good for the gun and for sure, not the brass.

-I have tested loads with this powder upto 54.5 grain which yielded avg speed of 2980fps although the accuracy was not there. And a little too fast for my needs. This speed exceeds the book maximum by 180fps using .5 less powder!
-With ADI's load data minimum charge of 49.5 can expect velocities of 2560fps. I'd hazard a guess that at 50.5 one might see around the vicinity of 2630fps. +or- 30fps
-The additional 300 FPS I am getting from this for sure is worrying, and why I am trying to get to the bottom of it.

Another thought occurred to me just now, though I've not ever heard of instances regarding very low charge weights, is there might be an issue with the powder itself. To test that, you'd have to get hold of some of that powder from another lot, maybe from someone you know.

There could be an issue with the powder's moisture content along the ambient temperature you're firing them in. Powder sitting around in dry hot climate can really reduce the powder's moisture content. Powder that dries out weighs less resulting in more powder by weight being put into the case. Still, I've heard of powder purposely being dried out to get more velocity that way, but never heard it able to get the kind of velocity increase you're experiencing.

Here in Arizona where Relative Humidity of the atmosphere can be very low. Like as I wright this, my gauges shows it's 10% outside. Indoors I'm at 29%. When the air is that dry, it can pull moisture out of the power really fast. How do I know? I track it by measuring my powder's moisture content every time I load up my cases. I make a concerted effort to keep my powder's moisture content close to what it was when I first open the container (like 45-50%).

The more I am reading and learning the more I am starting to lean toward the primers being too spicy and coupled with the relatively low powder charge causing the powder to burn suddenly and unevenly... more like a sudden boom rather than a slower but steady push.

Yes, too low of a powder charge changes the way it burns, particularly when unburnt powder is easily sent down the bore and later ignites in the bore before the projectile leave the muzzle. . . which is what can cause this issue and why it's not good to have very low charge weights.

Using a powder that gives you 100% case fill, or very close to it, works best all the way around. . . especially if you're after precision results.

 

[Im2bent]

Since manuals for powder charges will use case volumes that's typically used, especially those from powder suppliers, your Norma cases hold substantially more. If you were using a data from Norma, then I'd feel more comfortable. If you're at minimum charge and you're cases have 3-4 grs more case volume, then that's a problem; not so much using the max charge number.


I wouldn't think it's "dangerously" low. But it's effects are not good for the gun and for sure, not the brass.


Another thought occurred to me just now, though I've not ever heard of instances regarding very low charge weights, is there might be an issue with the powder itself. To test that, you'd have to get hold of some of that powder from another lot, maybe from someone you know.

There could be an issue with the powder's moisture content along the ambient temperature you're firing them in. Powder sitting around in dry hot climate can really reduce the powder's moisture content. Powder that dries out weighs less resulting in more powder by weight being put into the case. Still, I've heard of powder purposely being dried out to get more velocity that way, but never heard it able to get the kind of velocity increase you're experiencing.

Here in Arizona where Relative Humidity of the atmosphere can be very low. Like as I wright this, my gauges shows it's 10% outside. Indoors I'm at 29%. When the air is that dry, it can pull moisture out of the power really fast. How do I know? I track it by measuring my powder's moisture content every time I load up my cases. I make a concerted effort to keep my powder's moisture content close to what it was when I first open the container (like 45-50%).


Yes, too low of a powder charge changes the way it burns, particularly when unburnt powder is easily sent down the bore and later ignites in the bore before the projectile leave the muzzle. . . which is what can cause this issue and why it's not good to have very low charge weights.

Using a powder that gives you 100% case fill, or very close to it, works best all the way around. . . especially if you're after precision results.

How are you measuring powder moisture content?

 

[straightshooter1]

How are you measuring powder moisture content?

I seal a Kestrel DROP D3 in the bottle of powder until the reading levels off.

I know it's not a direct measurement of the powder kernel's moisture. But it's an excellent indicator and way to monitor changes in the moisture within the bottle that the powder is giving off.

https://kestrelinstruments.com/kestrel-drop-d3-wireless-temperature-humidity-pressure-data-logger?gad_source=1&gad_campaignid=17864808871&gbraid=0AAAAADtHI14GIEHeOpeQXnn95SawgL0gD&gclid=Cj0KCQjwt8zABhDKARIsAHXuD7aTtqqq8OON3C0XiUb7kynOHjz2EDMKgbMw5bFsUIBY4AhKzWURKnYaAlUaEALw_wcB