Pressure differences within tenths of a grain?

nomad 68

nomad 68

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Just want to pick some brains on this. I have a savage 99 carbine in .300 sav that I load at present with cci lr primer, varget and 150 flat base interlocks. This rifle is almost unexplainably accurate with 41.5 gr of varget but shows a bit of bulging in case in front of flash hole. When I back off to 41.3 gr, it does not have any bulging. Although not quite as tight of a group, still quite accurate. Any body else ever see pressure signs within a couple tenths while still under "max loads"?this rifle has a 20" barrel if that matters. Thanks I load for 6 other cals,always staring at or below max and never saw any case bulging of any kind.
Edit. Damn spell check lol
I ment staying at or below max. I start at min and work up for accuracy.
 
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Agreed that this is not a safe approach or load and yes a few tents of a grain can make a difference. Max loads found in your reloading books are established using the reference chambers of the testing agency or powder manufacturer doing the tests. Each rifle's chamber can and will likely be different that the test reference. Note that different reloading manuals will have vastly different max loads.

Having the brass bulge before having pierced primers is unusual in most calibres but I don't load 300 Savage. Still I think you are risking a case rupture.
 
The 0.2 grain difference in powder weight represents 562 psi and 11 ft/sec 2455 ft/sec vs 2466 ft/sec, according to generic Quick Load entries.

The difference between 41005 and 41572 psi may be enough to cause what you observe.

What are your velocities?
 
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Just remember to consider the ammo temps. It may be contained today @ that powder weight and temperature, no so much if temperature of the ammo changes winter to summer, hot truck, etc.

I'd consider finding the next lower node.
 
BCBRAD said:
The two grain difference in powder weight represents 562 psi and 11 ft/sec 2455 ft/sec vs 2466 ft/sec, according to generic Quick Load entries.

The difference between 41005 and 41572 psi may be enough to cause what you observe.

What are your velocities?
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Don't know velocities. I have been meaning to pick up a chrony. Any recommendations?
 
I always start at min and work up. Just so happens most of my rifles shoot very well at or near max for the particular powder I use in each and it's data. I never exceed max and never saw a pressure sign. Maybe it's my brass? I am using virgin hornady cases for the .300 sav.
 
2/10 of a grain of powder doesn't mean squat. What you are seeing is perfectly normal with modern undersize brass and generous chamber of the old 99. Don't worry one little bit about it, all loading manuals take into account that 95% of all 300 Sav rifles are in fact 99s and unless you are 3 or 4 grains over the hottest book max (which you obviously are not), you have no need to worry in the slightest. The bulge ahead of the web means you have just reached the pressure where your case expands and will actually seal the chamber, you are not over pressure at all, you have just reached the proper working pressure of your cartridge and rifle.
 
c-fbmi said:
2/10 of a grain of powder doesn't mean squat. What you are seeing is perfectly normal with modern undersize brass and generous chamber of the old 99. Don't worry one little bit about it, all loading manuals take into account that 95% of all 300 Sav rifles are in fact 99s and unless you are 3 or 4 grains over the hottest book max (which you obviously are not), you have no need to worry in the slightest. The bulge ahead of the web means you have just reached the pressure where your case expands and will actually seal the chamber, you are not over pressure at all, you have just reached the proper working pressure of your cartridge and rifle.
Click to expand...


I agree with this completely.

BCBRAD, how do you get the pressures you are describing. Hopefully you aren't using a proportional ratio. Pressure curves don't work that way. Pressure will depend on many things starting with powder type and density of the charge in conjunction with the weight of the bullet.

If you have a special formula that is credible, I would really appreciate seeing it as it would certainly be a boon to any handloader.


hometownhero, small case pressures can be effected by a tenth grain increase in powder charge, depending on how small sometimes to dangerous levels. Also with small cases like the 218BEE which have very small capacities. That being said, especially with pistol cartridges bullet diameters will make a difference as well.

In cartridges from 223 Rem and larger until you are approaching maximum pressures for the particular firearm they are being loaded into a tenth grain is around the same tolerance most scales are built to and I can tell you from experience that the larger the case capacity the less difference it has. For example I did some checking with a couple of different mid size cartridges over one of the old screen type chronographs. They tended to be a bit closer in readings then the Chrony. Anyway, a tenth grain below or above my base load made no discernable difference in velocity. Velocity increases or decreases with pressure. All of the cartridges tested averaged within 15 fps of each other. The spread was a little greater with a light registering Chrony. We would have tested more with the screens but the supply of screens was limited and the darn things were extremely expensive.
 
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Being a 99 ( (2) 303 Savages, 250-300 and 358 Winchester) owner I can vouch that the chambers tend to be on the looser side and case bulging is but one of the characteristics of loose chambers.
Not a bad thing on a lever action but It should be mentioned that proper reloading practices are in order, specifically the resizing of brass is critical if case separations are to be avoided.
You should rework the brass as little as possible trying to minimize work hardening of the brass. Neck sizing and a shoulder bump dies would be perfect, but careful adjustments of a FL sizer can also work reasonable well.
Enjoy that 99.
BB
 
c-fbmi said:
2/10 of a grain of powder doesn't mean squat. What you are seeing is perfectly normal with modern undersize brass and generous chamber of the old 99. Don't worry one little bit about it, all loading manuals take into account that 95% of all 300 Sav rifles are in fact 99s and unless you are 3 or 4 grains over the hottest book max (which you obviously are not), you have no need to worry in the slightest. The bulge ahead of the web means you have just reached the pressure where your case expands and will actually seal the chamber, you are not over pressure at all, you have just reached the proper working pressure of your cartridge and rifle.
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Awesome, thanks. I was hoping it was not a pressure issue.
 
Measuring case expansion just forward of the extractor groove at the unsupported section of the case is the best way to check for over pressure without pressure measuring equipment.
Read the Hodgdon's link below.

Simple Trick for Monitoring Pressure of Your Rifle Reloads
http://www.hodgdonreloading.com/reloading-education/tips-and-tricks/simple-trick-monitoring-pressure-your-rifle-reloads

Below, both of these cases were fired in my No.4 Enfield rifle and look completely different. The reason is the Priv Partizan case is larger in diameter and .010 thicker in the base web area.

The Greek HXP case is smaller in diameter and thinner in the base web area and the brass in the base area is slightly softer.

This is the reason why military 7.62 brass is thicker in the base and 5.56 brass is made harder in the base.

privihxp-1_zpsshjfudwg.jpg



Bottom line, the expansion ring you see on your cases has more to do with how the case is made and very little to do with chamber pressure.

How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/2014/05/how-hard-is-your-brass-5-56-and-223-rem-base-hardness-tests/
 
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No such thing as being at or below "Max". You mean you are below Max in the book. But that does not mean much about your rifle.

The Max load could be 2 or 3 grains more or less than the book - for your rifle.

If the book tested in a Savage 99, you could take the velocity they declared max, and then using the same powder, use that velocity to determine max in your rifle. If the velocity is the same as theirs, the pressure would be similar.

As for your bulge - If extraction is the same feel, then it means nothing. 0.2 gr in a rifle is a common variation of thrown charges.
 
Ganderite said:
No such thing as being at or below "Max". You mean you are below Max in the book. But that does not mean much about your rifle.

The Max load could be 2 or 3 grains more or less than the book - for your rifle.

If the book tested in a Savage 99, you could take the velocity they declared max, and then using the same powder, use that velocity to determine max in your rifle. If the velocity is the same as theirs, the pressure would be similar.

As for your bulge - If extraction is the same feel, then it means nothing. 0.2 gr in a rifle is a common variation of thrown charges.
Click to expand...
Yes, max in book and no extraction is the same.
 
bearhunter said:
I agree with this completely.

BCBRAD, how do you get the pressures you are describing. Hopefully you aren't using a proportional ratio. Pressure curves don't work that way. Pressure will depend on many things starting with powder type and density of the charge in conjunction with the weight of the bullet.

If you have a special formula that is credible, I would really appreciate seeing it as it would certainly be a boon to any handloader.


hometownhero, small case pressures can be effected by a tenth grain increase in powder charge, depending on how small sometimes to dangerous levels. Also with small cases like the 218BEE which have very small capacities. That being said, especially with pistol cartridges bullet diameters will make a difference as well.

In cartridges from 223 Rem and larger until you are approaching maximum pressures for the particular firearm they are being loaded into a tenth grain is around the same tolerance most scales are built to and I can tell you from experience that the larger the case capacity the less difference it has. For example I did some checking with a couple of different mid size cartridges over one of the old screen type chronographs. They tended to be a bit closer in readings then the Chrony. Anyway, a tenth grain below or above my base load made no discernable difference in velocity. Velocity increases or decreases with pressure. All of the cartridges tested averaged within 15 fps of each other. The spread was a little greater with a light registering Chrony. We would have tested more with the screens but the supply of screens was limited and the darn things were extremely expensive.
Click to expand...


These are predicted pressures via Quickload. In the above example I applied generic inputs (eg: listed case capacity, barrel length, bullet from QL inventory, burn rate for Varget).

So the pressures listed are a close ball park number. For spot on numbers one must physically measure case capacity in grains of water, measure length of bullet, weigh powder to the nearest .02gr, apply barrel length.

Then, know the velocity , use a magnetospeed or better yet a LabRadar . If velocity differs from predicted adjust burn rate to match given velocity. The program will give you barrel time in mS and pressure in psi.

I have been using a Labradar and Quickload for a few years now and finding a safe accurate load has been much easier and can quantify such with mathematics and physics.

Also, if you are at the optimum charge weight, therefore optimum burn, then a few 10ths of a grain either way tends not to have much change, basically you will have a tolerant load.

The key to make it all work are accurate inputs and an understanding of the program.
 
BCBRAD said:
These are predicted pressures via Quickload. In the above example I applied generic inputs (eg: listed case capacity, barrel length, bullet from QL inventory, burn rate for Varget).

So the pressures listed are a close ball park number. For spot on numbers one must physically measure case capacity in grains of water, measure length of bullet, weigh powder to the nearest .02gr, apply barrel length.

Then, know the velocity , use a magnetospeed or better yet a LabRadar . If velocity differs from predicted adjust burn rate to match given velocity. The program will give you barrel time in mS and pressure in psi.

I have been using a Labradar and Quickload for a few years now and finding a safe accurate load has been much easier and can quantify such with mathematics and physics.

Also, if you are at the optimum charge weight, therefore optimum burn, then a few 10ths of a grain either way tends not to have much change, basically you will have a tolerant load.

The key to make it all work are accurate inputs and an understanding of the program.
Click to expand...

Yes. If you develop a load in the spring or fall, try it with an extra half grain to see if the heat of the summer will cause problems.
 
Ganderite said:
Yes. If you develop a load in the spring or fall, try it with an extra half grain to see if the heat of the summer will cause problems.
Click to expand...

The Quickload program factors in temperature, apply temperature you expect to encounter. From very warm to cold your charge weight may vary up to 1/2 grain to keep velocity in line on '08 and '06 sized cases.
 
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