Low pressure "proof" round?

[Mall_Ninja]

So lots of times Tula or PMC Bronze are recommended when people want to test their gas systems on the minimalist pressure ammo. I started thinking that since we cannot control the product any manufacture produces, is there enough use for people "in the know" to devise a sort of "low pressure test" round or at least "spec" it out? Something to give everyone a repeatable baseline to test to. Since we have a high pressure proof to test durability, why not a low pressure to test minimum pressure for proper cycle (for such things as proper buffer weight)?

[TMS951]

I do 6 mags with 5rnds each of Tula. Mostly looking for failure to lock back. 6 mags and 30rnds helps make up for manufacturing inconsistencies IMO.

[Mall_Ninja]

Well when I state manufacturing variance im not just talking about lot to lot. Whats to say that they wont decide to increase/decrease the powder charge? Change the chemical make up a little? Different primer? Lots of variables that the manufacturer isn't required to disclose unless its "NATO". There is only a SAAMI spec for 223 and who knows how close they monitor production? Week to week, year to year, there could be a huge variation.

Simply put, using production non-NATO "spec" ammo is far from "scientific" analysis when it comes to "testing" of a firearm. I see much more scrutinization on less important aspects of the AR platform...

[foxtrotx1]

EDIT for simplicity: I have had short stroking with some WOLF cases, not with others.

I'm pretty sure their lot to lot does vary. But my N=1.

[TMS951]

I understand wanting a known precise proof round. I would say use a good .223 round by a high end manufacturer like black hills.

Then you know all 5.56 and and good .223 will cycle.

I don't shoot much crap ammo, so I know if it locks back with tula for the most part everything else I shoot will work.

If you want to always shoot crap ammo idk what to say...buy a shrubmaster with a huge port?

But if you want to shoot crap ammo I am surprised you are concerned about the precision of your "light proof".

keep in mind by setting up your gun to cycle the lightest of light rounds it will be over gassed / under buffered for real ammo.

[Mall_Ninja]

Personally, wanting to know what the lowest pressure round your rifle will cycle has little to do with the desire or intention to regularly shoot crap ammo. It, at least for me, is the desire to know your gas/buffer combination on a custom build (nearly ALL of my rifles) is sound. Without the ability to run a low pressure round you will have no idea what your operating parameters actually are. Anyone can run a carbine buffer and run NATO and have no issues, besides accelerated wear and tear. But what happens in a bad situation and all you have available is poor quality?

Perfect example is the here and now. Ammo availability is sketchy at best. I have pretty good luck lately getting PMC and Tula. Do I prefer it? Hell no, but will I run it if its the only choice? YUP...

Last week both my recent builds (Bravo 18" Mk12 SPR and DD 16" middy) would lock back with Tula and PMC Bronze, wether on top of a carbine H3 or an A2 rifle lower. Yesterday, with a semi BCG, H3 the Bravo SPR stopped locking back on Tula. It would cycle flawlessly 100% otherwise.

If you are like me and have at least one rifle that is a SHTF rifle, do you really want to chance having it right on the margin of reliability? Or do you just run a carbine buffer and deal with the excess wear and tear? Personally id rather have a baseline thats repeatable and tune each build to be "just right". The BCM Mk12 is normally on top of an A2, and yesterday WOULD lock back on the A2, just not the H3. To me this is a perfect setup as 100% cycling is more important than locking back. Since Tula is so low pressure. If the SHTF and I ran out of M855 and 77Gr. SMK's I know that worse case it will cycle crap ammo, even if I have to charge it in-between mag changes...

[Mudpie1313]

I ran into the under pressure issue with my pmc bronze this weekend. Two of my frankenguns would not cycle it properly. Both would eject but not cycle back enough to pick up the next round. Run by hand, pick up each time, but my Syrac Ordanance upper with the adjustable gas block will eat anything. I run the 5.56 in all three with no issue even when working the trigger hard.

[Mall_Ninja]

I ran into the under pressure issue with my pmc bronze this weekend. Two of my frankenguns would not cycle it properly. Both would eject but not cycle back enough to pick up the next round. Run by hand, pick up each time, but my Syrac Ordanance upper with the adjustable gas block will eat anything. I run the 5.56 in all three with no issue even when working the trigger hard.

In my case I suspect the large weather change we had here. Cooler temps and very high humidity probably reduced chamber pressures and velocity. I noticed that at 528 yards, my Barrett went from .5-1 Mil hold over (100 yd zero) to 2 full Mils. So it wasn't just my AR's that changed behavior a bit...

Have you experienced a large weather change recently that could have contributed?

[Suwannee Tim]

I understand very well what you want and it makes good sense to me. I do this over and over working up loads for semi-autos. I want to work towards the maximum and minimum loads though I don't usually work down to loads that actually fail to function the action. I am an old revolver and bolt action guy and of course these types do not fail to function no matter how light the load. Except for 45 ACP I am kind of new to reloading for semi-autos having only done it in a big way for the past year or two. One thing that does surprise me is the wide range of loads that will safely function semi-autos.

If you reload this is an easy thing to do. If you don't reload maybe you should consider it.

[Mudpie1313]

In my case I suspect the large weather change we had here. Cooler temps and very high humidity probably reduced chamber pressures and velocity. I noticed that at 528 yards, my Barrett went from .5-1 Mil hold over (100 yd zero) to 2 full Mils. So it wasn't just my AR's that changed behavior a bit...

Have you experienced a large weather change recently that could have contributed?
It has been humid here but I experienced the Tula issue on one of the same ones in an air conditioned range. Ammo had been kept in air conditioning including car ride to range. It is a DPMS upper and lower with 13.7 Rainier ultra match with pinned Hawg. It has a carbine buffer.

[Mall_Ninja]

It has been humid here but I experienced the Tula issue on one of the same ones in an air conditioned range. Ammo had been kept in air conditioning including car ride to range. It is a DPMS upper and lower with 13.7 Rainier ultra match with pinned Hawg. It has a carbine buffer.

Humidity mostly effects ballistic trajectories (air density), temps effect chamber pressure which in turn effects gas pressures. Here it took about 20 degree temp drop to make my rifle stop locking back on the same lot of Tula.

Experienced reloaders and/or shooters with chronographs can tell you how much ambient temps can effect velocity and chamber pressures...

[Mall_Ninja]

If you reload this is an easy thing to do. If you don't reload maybe you should consider it.

Once I get through the rest of this 50 BMG ammo I will be more motivated to make the investment!

As of right now I only have a pistol capable loader...

[MistWolf]

Actually, it isn't ambient temperatures that affects pressure, it's ammo temperature- specifically the temperature of the powder.

Before the industry can come up with a "minimum pressure proof round" they'll have to get together and set a pressure range (and define the pressure curve) within which a self loading firearm will reliably operate so they'll know what the minimum is. It would have to be done for each caliber and all types of self loading actions would have to be tuned to meet the criteria.

This is an area where the shooter has to become their own SME and shoot their rifles to determine how they'll be tuned for what ammo. The bottom line really is this- A properly tuned AR will run most of the ammo that's out there, with the exception of some extremely low powered/sticky types (by "sticky", I mean cases that are made of materials with higher stiction than brass, such as steel or aluminum and require more force to feed and extract reliably)

[Mall_Ninja]

Actually, it isn't ambient temperatures that affects pressure, it's ammo temperature- specifically the temperature of the powder.

LOL To keep the explanation short, when I say ambient, I mean the temp of the powder/cartridge/primer. If your house is 72 degrees "ambient" then what would be the powder temp of your ammo sitting on the dinner table in "YOUR" house?

If the range you are at is 72 degrees "ambient", what would the temp of your box of ammo sitting on the shooting table be? I was not extremely thorough in my explanation because I wrongfully "assumed" most reading this would get what I was saying. Apparently not...


It would have to be done for each caliber and all types of self loading actions would have to be tuned to meet the criteria.

You are looking way to deep into this. I wasnt saying the "industry" should develope low pressure proofs for everything under the sun. I was refferring to the people on this forum who know their shit, developing a low pressure "proof" for us to use specifically in AR-15's using NATO 556 and SAAMI 223 ammo...

Something like "Using the LP proof my rifle will lock back with an H2 but fails to lock back on an H3". By using a set "proof load" a guy in Florida can expect to get the same test results as a guy in California. With variation from Lot to Lot and month to month and brand to brand. How much "data" is there actually out there in regards to what to test to? Its far from scientific to just tell someone to try a certain brand (Tula, PMC Bronze). The Tula you have in your hands could be quite a bit different from the Tula I have in my safe. If BCM wants to "HPT" and some guy in Antarctica wants to do the same. They will have a "comparable" test result as the HPT proof round has a "STANDARDIZED" set of parameters which makes it "REPEATABLE AND CONSISTENT"...

[Mudpie1313]

Yea, I was not looking that deep.:blink: I had the same issues with ftf from Tula and PMC bronze on two of my rifles.Tried different mags but cycles fine when worked by hand or if I used 5.56 brass. I have an ace entry on one and ace socom on the other both with carbine spring and buffer. My third has Syrac ordanance upper with adjustable gas block it will eat anything. It has carbine buffer and MFT stock. I was trying to figure why the ftf happened and that is the only thing I can figure. My 14.5 will spray 5.56 like no tomorrow will stove pipe an ftf with the bronze. I started to think the buffer tube was shorter on the ace stocks causing a stiffer spring.:rolleyes:

[Kilo 1-1]

I can understand this thought process that the OP posted at the top, as I went through something like this.

That said, I'll echo what's been said above, Tula is shit. At this current climate, I train with 90% steel cased Tula or Brown bear stuff.
With my old Stag 16" carbine upper (statistically known to be over-gassed ) with H buffer, Tula would sometimes short cycle and or not lock back on last shot, but not very common. These were the older earlier lots of Tula from a few years back. No issues with Brown Bear.

In my current BCM LW 16" Carbine upper with H buffer, it's cycled through it all and locked back with last shot. This is the later lot of Tula. No issues with Brown bear either.

I purposely went with a BCM carbine upper over a midlength because I wanted the extra gas to cycle weaker training ammo. Although I've seen many midlengths cycle with weaker ammo, I've seen some that can't, so that's why I went carbine. When shooting NATO spec rounds (M193/M855), the BCM with H buffer is still cycling smoothly (subjectively). I could probably go with a H2 with the NATO rounds, but I kept the H buffer as the primary because it cycles reliably with all the ammo I use.

[Suwannee Tim]

Once I get through the rest of this 50 BMG ammo I will be more motivated to make the investment!...

There is this idea out there that you need a superdynawhopper progressive press to reload. If you reload you really, really need a good single station press and a good scale. Everything else is accessories including the souped up progressive. I make more lots of experimental ammo than production lots and most of those are made on the single station. You can get your feet wet on a shoestring to mix a couple of metaphors.

[Mall_Ninja]

There is this idea out there that you need a superdynawhopper progressive press to reload. If you reload you really, really need a good single station press and a good scale. Everything else is accessories including the souped up progressive. I make more lots of experimental ammo than production lots and most of those are made on the single station. You can get your feet wet on a shoestring to mix a couple of metaphors.

In regards to 50 BMG and any other precision rifle rounds (for me 556 and 762 NATO, 338 Lapua as well) I completely agree. In fact, with 50 BMG specifically, cost is not the reason I would choose single stage. Its primarily safety. I plan to load, check and recheck every single round. Its just plain to dam DANGEROUS to take any chances with something that powerful. However, for 556 blasting ammo and any pistol, I would go progressive...

[MistWolf]

LOL To keep the explanation short, when I say ambient, I mean the temp of the powder/cartridge/primer. If your house is 72 degrees "ambient" then what would be the powder temp of your ammo sitting on the dinner table in "YOUR" house?

If the range you are at is 72 degrees "ambient", what would the temp of your box of ammo sitting on the shooting table be? I was not extremely thorough in my explanation because I wrongfully "assumed" most reading this would get what I was saying. Apparently not...

I "didn't get it" because the use of "ambient temperature" in this case is inaccurate. While the average temperature of the air and surroundings may have affect on the temperature of the powder of the ammo, there's no guarantee it will. At the range, the air temperature may be 72* but the ammo might be out in the sun getting much warmer. Or the box the ammo is in could be getting warmed by the sun. Ambient temperature and powder temperature can vary wildly according to localized conditions, something a shooter needs to be acutely aware of.

Humidity plays no role in chamber pressure


You are looking way to deep into this. I wasnt saying the "industry" should develope low pressure proofs for everything under the sun. I was refferring to the people on this forum who know their shit, developing a low pressure "proof" for us to use specifically in AR-15's using NATO 556 and SAAMI 223 ammo...

Ok, not an industry wide change. Even so, we would have to define what the lower limit would be and standardize it among ourselves. It likely would have to be a handload "xbullet in xcase using xweight of xpowder with xprimer and loaded to xOAL". We would need to figure out what kind of pressure the load was generating in a standardized chamber and whether or not the load is generating the right pressure. Without this kind of standardization, the whole exercise is a waste of time and resources. It's not "looking too deep into it" it's realizing what's needed to make the program work

[Mall_Ninja]

I "didn't get it" because the use of "ambient temperature" in this case is inaccurate. While the average temperature of the air and surroundings may have affect on the temperature of the powder of the ammo, there's no guarantee it will.

So maybe I need a list of what you think causes such major discrepancies between ambient and ammo temp.


At the range, the air temperature may be 72* but the ammo might be out in the sun getting much warmer. Or the box the ammo is in could be getting warmed by the sun.

Yes, and I might choose to set the box of ammo on the radiator of my diesel, or pre-heat it in a pressure cooker. But within REASON ambient temp is going to be pretty close and made perfect sense in the context I was using. Why muddy the water?


Ambient temperature and powder temperature can vary wildly according to localized conditions, something a shooter needs to be acutely aware of.

If someone is aware that temperature, wether ambient or dynamic, effects chamber pressure, than common sense should be enough to figure out from there.


Humidity plays no role in chamber pressure

Agreed, was that just a random statement or are you implying I said something to the contrary?


Ok, not an industry wide change. Even so, we would have to define what the lower limit would be and standardize it among ourselves. It likely would have to be a handload "xbullet in xcase using xweight of xpowder with xprimer and loaded to xOAL".

Absolutely...


We would need to figure out what kind of pressure the load was generating in a standardized chamber and whether or not the load is generating the right pressure.

Actually, the best bet I think is to use a test barrel thats equipped with pressure transducers. Measure several of the "lowest common denominators" and average those results. Then develop a load that represents that average.


Without this kind of standardization, the whole exercise is a waste of time and resources.

Agreed...

[MistWolf]

...Yes, and I might choose to set the box of ammo on the radiator of my diesel, or pre-heat it in a pressure cooker. But within REASON ambient temp is going to be pretty close and made perfect sense in the context I was using. Why muddy the water?...

Hoo-boi... You don't know how much heat ammo can absorb just from being left in the sun or locked up inside a car and how common an occurrence both are

[foxtrotx1]

When I'm shooting here in AZ, ammo and mags left in car get hot. In the summer the air in the car can go up to 180 degrees. Imagine how hot our ammo gets in there? :D

[Mall_Ninja]

Hoo-boi... You don't know how much heat ammo can absorb just from being left in the sun or locked up inside a car and how common an occurrence both are

Actually I do, but (see below) getting into those kind of details was not the object of my post, which is why I tried to move on. Obviously that has been quite an issue...



Experienced reloaders and/or shooters with chronographs can tell you how much ambient temps can effect velocity and chamber pressures...

I have seen a few inches (higher) POI shift on my Barrett after grabbing another box of 661 Gr. FMJ that was in a gear bag in the sun rather than on the table next to me. Thats the most POI shift I have seen related to temps, but could partly have been a flyer. Seems my 556 stuff is not nearly as susceptible on the same day same yardage.

Can we get back to topic now?

[Mall_Ninja]

When I'm shooting here in AZ, ammo and mags left in car get hot. In the summer the air in the car can go up to 180 degrees. Imagine how hot our ammo gets in there? :D

I personally never leave ammo in the car as we see similar temps here. I also do not shoot ammo that has been significantly heat soaked either.

If its too hot to touch, you are Tom Cruise'n the danger zone! :D

[MistWolf]

You don't even understand the topic well enough to know why it was important to be clear about ambient temperatures and pressure.

You're on your own from here, kid

[Mall_Ninja]

You're on your own from here, kid

You sure will be mist...

[patrick sweeney]

Back to the original subject;

Finding an acceptable lower threshold may be difficult. I once developed a load for competition, using Winchester 63 grain softpoints, and pushing them at a poofty 2300 fps.

All my ARs would cycle it.

I think the only approach that might have value is to use the actual ammo that gives some rifles fits. If that is Tula, then Tula is your test ammo.

[Iraqgunz]

OK kiddies. Please knock it off.

[Mall_Ninja]

Back to the original subject;

Finding an acceptable lower threshold may be difficult. I once developed a load for competition, using Winchester 63 grain softpoints, and pushing them at a poofty 2300 fps.

All my ARs would cycle it.

I think the only approach that might have value is to use the actual ammo that gives some rifles fits. If that is Tula, then Tula is your test ammo.

The only issue, is we dont know if they change something. If they change primers, powder, charge, etc. suddenly the pressure could go up or down significantly. Lot to lot variance could be all over the place so even though its "acceptable" to use Tula or Bronze like we have been doing, it certainly isnt optimal.

In your above example, which is a great one by the way, would those same AR's cycle Tula or Bronze?

[patrick sweeney]

That was long before the ex-commies were sending ammo our way. None exist in their original configuration any more, so no way to find out.

[Mall_Ninja]

That was long before the ex-commies were sending ammo our way. None exist in their original configuration any more, so no way to find out.

Bummer!

[Suwannee Tim]

Hey Mall Ninja! You haven't mentioned your 50 BMG all day!

[Mall_Ninja]

Hey Mall Ninja! You haven't mentioned your 50 BMG all day!

SHIT! Thanks for reminding me! Im under quota... :(

FYI:

750 Grain AMAX will not penetrate 1/2" mild steel at 528 yards (but puts a real WHOOPING on it)...

661 Grain Barrett M33 goes through like Taco Bell goes through me...

There you go, sort of on topic (not really) and 50 BMG all in one post!

[elephantrider]

Humidity mostly effects ballistic trajectories (air density)


Just for the record, humidity has almost zero effect on ballistic trajectory.

[Suwannee Tim]

I just finished reloading 20 rounds of 416 Rigby with 400 grain bullets and Reloder 19 powder. Hornady manual called for 84 to 94 grains of powder. I had several hang fires and one fizzle. Then I looked in the Speer book (I had forgotten Speer makes a 400 grain 416). They call for a starting load of 102 grains and a top load of 105. Damn big difference. I really think RLR 19 is too slow for this cartridge. I just got some IMR 4007 SSC, I think I will try that next.

Hey! If Mall Ninja can talk about his 50 then I can talk about my 416!

[Mall_Ninja]

Hey! If Mall Ninja can talk about his 50 then I can talk about my 416!

Heck ya man, after all it was my wifes idea to get the Barrett, shes compensating...







For being a midget! :D:D:D:D:D

[AlphaKoncepts]

Why not reload a series of low pressure proof rounds, working your way down down down until you find consistent failures to cycle. Then you know the bottom end of what it takes to cycle your firearm.

If I had unlimited time and money things like this are the kinds of things I would love to experiment with. For example swap a spring and run the test, swap a buffer and run the tests. See REALLY what affect these have on the system.

[patrick sweeney]

An interesting idea, but one that gets more complicated as you delve deeper into it.

OK, you settle on a 55 fmj, and once-fired, good brass.

What powder? If you simply use the typical .223/5.56 powders, as you go down in charge weight, your extreme spread will go up. You'll soon find that the pressure variances will be so great that the occasional low-pressure load drops below normal levels, and you get malfs.

But is that what you want?

So, you switch to a bulkier, faster-burning powder, one happier at lower velocities, to keep your extreme spread within norms. What does that do for port pressure?

We can certainly experiment with this, but we can't be certain (absent pressure-barrel readings) just what it is we're getting.

[Mall_Ninja]

Both of you guys make good points. What I was imagining was going with the most common (light end) projectile to keep costs as low as possible. Same as powder and primer, nothing fancy. The starting point would be the lowest velocity known load.

The best bet would be to use a test barrel with pressure sensors and run a few different cartridges from a few different "lots". Tula, Brown Bear, PMC Bronze, etc. Find the lowest average pressure accross the board and then tune to be below that.

No doubt it would take some trial and error, and a lot of real world testing by industry people who can be trusted. Say, send a few boxes with different charges to 4-5 different people. The objective being to have them run in differing, known good, rifle setups (different barrel lengths, gas systems and buffer assemblies) and see what the results are.

Once its developed then we have a repeatable, "lowest common denominator". A load that anyone can have the recipe too and test their own setups.

This way, if Tula, PMC, etc. change stuff around it doesnt matter and we wont be getting jumbled test data...

[Suwannee Tim]

Shot the Rigby today, all 20 rounds. That son of a bitch kicks!

[rjacobs]

Shot the Rigby today, all 20 rounds. That son of a bitch kicks!

So you are saying you dont have a problem with low pressure?:suicide2:

[Mall_Ninja]

So you are saying you dont have a problem with low pressure?:suicide2:

HA! Thats what she said! :D

[Hitchhiker]

I just finished reloading 20 rounds of 416 Rigby with 400 grain bullets and Reloder 19 powder. Hornady manual called for 84 to 94 grains of powder. I had several hang fires and one fizzle. Then I looked in the Speer book (I had forgotten Speer makes a 400 grain 416). They call for a starting load of 102 grains and a top load of 105. Damn big difference. I really think RLR 19 is too slow for this cartridge. I just got some IMR 4007 SSC, I think I will try that next.

Hey! If Mall Ninja can talk about his 50 then I can talk about my 416!


I've loaded quite a bit of 416 Rigby and for anything with that size case and / or near 100 grains of powder, the only primer I've found that works well is the Federal 215. The other magnum primers don't equal the Federal 215 primer for large cases and large amounts of powder.

[Mall_Ninja]

I've loaded quite a bit of 416 Rigby and for anything with that size case and / or near 100 grains of powder, the only primer I've found that works well is the Federal 215. The other magnum primers don't equal the Federal 215 primer for large cases and large amounts of powder.

Sounds crazy to me? I have blown a hole in a blue, shop type paper towel, at the end of a 32" barrel with just a primed case! You would think something with that much "boom" would ignite any kind of powder just fine?

[Hitchhiker]

I've tried IMR-4198 and H4198 with 55 grain bullets and no amount of H4198 will cycle my rifles. A few people it works for them. IMR-4198 does cycle and fairly well for me. A few people claim IMR-4198 doesn't work in their rifles. I've since used IMR-4198 with 55 grain and 69 grain bullets.

Some people get way with 21.5 or even 22.0 grains with 55 grain bullets but the powder is so fast I load 21.0 grains because I think the pressure can climb quickly with hotter loads. With 62 grain and 69 grain bullets I use 20.0 grains,, which is about max. The results are best 55 grain bullets and velocity is a bit low with 69 grain bullets. If a rifle will cycle with IMR-4198, it will work with just about any factory loads.

Australia used H322 for their early 5.56 ammunition in their Steyr AUG rifles. Australian special forces wanted to use the M4 due to the available accessories. The original Aussue 5.56 ammunition wasn't reliable in the M4 due to the powder and the bullet shape and the case capacity. Australia then developed IMR-8208 XBR powder for the M4 with a standard SS109 bullet and larger, standard volume 5.56 case. The newer ammunition has a green bullet tips.. Both use 63 grain penetrator bullets but the shapes of the bullets are different. The older cases have thicker case heads with reduced capacity.

Australia quit making primers in 1999 and the primer plant was destroyed to make room for 2000 Olympics. Australia now imports CCI primers from the US for 5.56 and 7.62 ammunition and RWS primers from Germany for 50 BMG ammunition.

The only difference in the military 5.56 powder and commercial IMR-8208 XBR is the commercial powder is dyed grey-black to make it look more like traditional IMR powder. The military powder is a lighter color as the Australian powder making process uses less graphite than original IMR powders.

IMR-8208 XBR is made to meet the gas port pressure requirements of both the Steyr AUG and the Colt M4. The required ranges of gas port pressures for both rifles overlap each other but at different ends of each ones required range of gas port pressure.

Most countries, like the US, use double base ball powder for their 5.56 ammunition. Australia only makes single base extruded powders. The required powder density is high which can make the powder a bit touchy, especially in larger cases such as 7.62x51.

Canada only makes extruded powders but makes a special double base extruded powder for their 5.56 ammunition and a single base powder extruded powder for their 7.62 ammunition.

Neither Australia nor Canada wanted to import powder for their military rifle ammunition, so their had to develop powders for the cartridges and rifles they use.

[Mall_Ninja]

Canada only makes extruded powders but makes a special double base extruded powder for their 5.56 ammunition and a single base powder extruded powder for their 7.62 ammunition.


Awesome info, thanks! Whats the difference between single vs double base powder? Shape?

[Hitchhiker]

Awesome info, thanks! Whats the difference between single vs double base powder? Shape?

Currently, propellants using nitrocellulose (detonation velocity 7,300 m/s) (typically an ether-alcohol colloid of nitrocellulose) as the sole explosive propellant ingredient are described as single-base powder.

Propellants mixtures containing nitrocellulose and nitroglycerin (detonation velocity 7,700 m/s) as explosive propellant ingredients are known as double-base powder.

During the 1930s triple-base propellant containing nitrocellulose, nitroglycerin, and a substantial quantity of nitroguanidine (detonation velocity 8,200 m/s) as explosive propellant ingredients was developed. These propellant mixtures have reduced flash and flame temperature without sacrificing chamber pressure compared to single and double base propellants, albeit at the cost of more smoke.

In practice, triple base propellants are reserved mainly for large caliber ammunition such as used in (naval) artillery and tank guns. During World War II it had some use by British artillery. After that war it became the standard propellant in all British large caliber ammunition designs except small-arms. Most western nations, except the United States, followed a similar path.

In the late 20th century new propellant formulations started to appear. These are based on nitroguanidine and high explosives of the RDX (detonation velocity 8,750 m/s) type.

[Hitchhiker]

Extruded powders can be either single base or double base.

Double base powders can have higher energy and velocity than single base powders at similar pressures. And it's easier to make them with higher density which takes up less case capacity.

Ball powders are always double powders due to the way they are made.