Why is a faster propellant more suited to a light projectile

[in2anity]

It is common to use a faster than regular powder for a lighter than regular projectile (leaving more empty space). What is the science behind this?

Example a 125gr 308 pill works great with the slightly faster AR2207 - why is it so?

[SCJ429]

A complex subject, hard to explain in a quick post. Slower powders produce peak pressure for longer. Heavy projectiles are harder to get moving and faster powders build pressure quickly with a bullet that is resisting this movement which may cause the pressure to spike. Light bullet can be shot with slow powders but you can run out of space due to their bulk density and the bullet may exit before the burn is completed.

Use the slowest powder that gives you the speed you are looking for. It is much kinder on you throat. The case design will also dictate the powder you have to use. No use trying slow powders in straight walled cases even if you are shooting heavy projectiles.

[SCJ429]

Also 2207 is slightly faster than BM1 but much faster than 2208. If you used 2207 in place of 2208 with that weight of pill you would probably give away 200 fps. You would be better to use 2208 or 2206.

[bladeracer]

It is common to use a faster than regular powder for a lighter than regular projectile (leaving more empty space). What is the science behind this?

Example a 125gr 308 pill works great with the slightly faster AR2207 - why is it so?

More empty space?

[in2anity]

Awesome response and just the level of detail I was after SJ - thanks mate What you said totally makes sense - lighter pills spit out faster so you need to get the burn done sooner.

With respect to 2208 vs 2207, I hear you, but I’m reloading for economy - 2208 is basically 10grs more - and 2207 is one of my go-tos for other calibers.

So SJ do you feel a faster powder in a listed region is basically harder on the throat?

[gordicans]

It is common to use a faster than regular powder for a lighter than regular projectile (leaving more empty space). What is the science behind this?

Example a 125gr 308 pill works great with the slightly faster AR2207 - why is it so?

It's not just about the size of the projectile, it's about the shape of the case. For example a .222 (which is a very similar cartridge shape to a .308) can use a fast burning powder because of the neck of the cartridge. Not only can use a fast burning powder, but needs a fast burning powder because of the shape of the cartridge neck. The big neck slows down the burning, so you need a fast burning powder in these types of cartridges

[Apollo]

I think a couple of you are heading off down the wrong track and going to get lost in the bush.

A certain cartridge case does have a typical powder burn rate required for it's design. Has nothing to do with the size of the case neck. First and foremost you are trying to come up with a powder that has a complete burn before the bullet leaves the barrel muzzle otherwise you are simply wasting powder if it is still burning once the bullet leaves the muzzle.

The shorter or longer the barrel makes a difference to which powder is most efficient. The weight of the bullet has the same effect in that a lighter bullet requires less initial pressure to get it moving and you need the powder to burn quicker than a heavier bullet so it has a complete burn way before it leaves the barrel muzzle.

I don't see the relationship between a .222R and a .308W as the cases are completely different in design other than both being a bottle neck tapered case. Something close to a .222R would be say a .223R with the only difference really being the .222R has a longer neck. You don't use the same powder in each case with the same weight bullet. The old ADI AR2206 with a 50gr bullet for decades was one of the long term best combinations but the same 50gr bullet in a .223R would be best served with say ADI Benchmark 2 and produces far more velocity given also that the .223R has greater case capacity due to the difference in design.

Remember when choosing a powder for a given cartridge case your aim is to get close to a 95-100% case powder fill for best efficiency.

You have other factors as well that influence the type (burn rate) of the powder used like case shoulder angle and case neck length which both affect the burn shape from the case. The so called "barrel burners" due to many factors are harsh on barrels (barrel throat) for one being where the hottest part of the burn happens, inside the case neck or in the barrel throat.

So in my short answer for why a faster powder is more suited for a lighter bullet is simply to enable a complete powder burn before the bullet leaves the barrel.

Many will not agree with my thoughts so that is your choice in life. Look at the data supplied by ADI (Hodgdon USA who does the testing) for a typical bullet weight and see that in most cases there are say three powders suggested around a typical velocity result. But, how each perform in your rifle is up to you to establish because not all factors are the same as that tested.

[marksman]

I totally agree

[SCJ429]

Awesome response and just the level of detail I was after SJ - thanks mate What you said totally makes sense - lighter pills spit out faster so you need to get the burn done sooner.

With respect to 2208 vs 2207, I hear you, but I’m reloading for economy - 2208 is basically 10grs more - and 2207 is one of my go-tos for other calibers.

So SJ do you feel a faster powder in a listed region is basically harder on the throat?

The 308 is not hard on barrels and you are unlikely to notice significant shortening of the barrel life by using 2207. But I would not use it because you will usually see better results with 2208 because it fills the case better and should have a more reliable consistant burn. Save the 2207 for your 45/70.

[SCJ429]

I think a couple of you are heading off down the wrong track and going to get lost in the bush.

A certain cartridge case does have a typical powder burn rate required for it's design. Has nothing to do with the size of the case neck. First and foremost you are trying to come up with a powder that has a complete burn before the bullet leaves the barrel muzzle otherwise you are simply wasting powder if it is still burning once the bullet leaves the muzzle.

So in my short answer for why a faster powder is more suited for a lighter bullet is simply to enable a complete powder burn before the bullet leaves the barrel.

I don't disagree but sometimes you don't get a complete burn with the most suitable powders. Most big magnums have a flame eminating from the muzzle unless you have 30+ inch barrels. Even the humble 243 can produce big flames but I wouldn't be feeding it 2207 to try and prevent this.

[Apollo]

Muzzle flash is not something I have taken any note of and not quite the path I was heading.

I haven't watched even what I would call a very efficient powder load shot at night time to see. What I'm more getting at is those powder loads that don't burn efficiently and leave not only some unburnt powder in the barrel bore but sometimes in front on the ground.

Some mixtures of calibre and powder loads can leave a very clean bore and those not so good full of not so well burnt (black) fouling plus traces of powder granules on the ground out in front. To me that is not an efficient load.

On topic to me is to use a powder load that gives you the best efficiency and burn so if that is true you should have the best velocity and accuracy you can achieve. So in the years I've been playing there is a starting powder type for the bullet weight and barrel you are shooting, you may be able to tweak that with a faster or slower powder. I think that in any reloading manual you will see faster powders suggested for the lighter bullet range for that cartridge and calibre. Don't think I ever seen the reverse.

Just a note that all the powders made by say ADI are exactly the same base component mix. It's the retardant and granule size that affects the burn rate. Plus all those powders are coated with graphite to reduce static affects.

[SCJ429]

Nosler publish a most accurate powder recommendation with their load data. Pick a powder around this burn rate and you will be in the ballpark. You shouldn't be spitting out unburnt kernels of powder from your muzzle if you follow Noslers advice.

[Oldbloke]

+1 Apollo.

Just a side note. Powder Granual shape can also effect the burn rate.

[Stix]

I think a couple of you are heading off down the wrong track and going to get lost in the bush.

A certain cartridge case does have a typical powder burn rate required for it's design. Has nothing to do with the size of the case neck. First and foremost you are trying to come up with a powder that has a complete burn before the bullet leaves the barrel muzzle otherwise you are simply wasting powder if it is still burning once the bullet leaves the muzzle.

The shorter or longer the barrel makes a difference to which powder is most efficient. The weight of the bullet has the same effect in that a lighter bullet requires less initial pressure to get it moving and you need the powder to burn quicker than a heavier bullet so it has a complete burn way before it leaves the barrel muzzle.

I don't see the relationship between a .222R and a .308W as the cases are completely different in design other than both being a bottle neck tapered case. Something close to a .222R would be say a .223R with the only difference really being the .222R has a longer neck. You don't use the same powder in each case with the same weight bullet. The old ADI AR2206 with a 50gr bullet for decades was one of the long term best combinations but the same 50gr bullet in a .223R would be best served with say ADI Benchmark 2 and produces far more velocity given also that the .223R has greater case capacity due to the difference in design.

Remember when choosing a powder for a given cartridge case your aim is to get close to a 95-100% case powder fill for best efficiency.

You have other factors as well that influence the type (burn rate) of the powder used like case shoulder angle and case neck length which both affect the burn shape from the case. The so called "barrel burners" due to many factors are harsh on barrels (barrel throat) for one being where the hottest part of the burn happens, inside the case neck or in the barrel throat.

So in my short answer for why a faster powder is more suited for a lighter bullet is simply to enable a complete powder burn before the bullet leaves the barrel.

Many will not agree with my thoughts so that is your choice in life. Look at the data supplied by ADI (Hodgdon USA who does the testing) for a typical bullet weight and see that in most cases there are say three powders suggested around a typical velocity result. But, how each perform in your rifle is up to you to establish because not all factors are the same as that tested.

Whilst i get what you're ssying Apollo...some of whst you write, written in absolute terms, is contradicted later on in the post...or msybe its just how i read it...

So would it be fair to ssy, that you're trying to say it is a combination of many things together, examples of which you have written, that detrmine the best powder to use...& that as a general rule, the most efficient powder is one that completes its burn before the bullet leaves the muzzle, & that if one is chasing complete efficiency (meaning maximising velocity), this will most often be found with load densities in the order of close to or around 100%...but is not necessarily always the rule...

Also...i know a bloke, who is a believer in picking the slower of 2 nodes from any given powder/bullet combo, citing that more often than not, the slower node will be inherintly more accurate...

How does that work, given what you've mentioned in your post...?

[Apollo]

+1 Apollo.

Just a side note. Powder Granual shape can also effect the burn rate.

I am going on the general typical ADI extruded Rifle Powders. They are all the same shape granule just vary in size. I have no knowledge of their other powders nor does my friend who used to work at ADI testing powders. ADI Double Base and Imported Powders are a different animal.

[Apollo]

Nosler publish a most accurate powder recommendation with their load data. Pick a powder around this burn rate and you will be in the ballpark. You shouldn't be spitting out unburnt kernels of powder from your muzzle if you follow Noslers advice.

I like the Nosler published Data mainly because they also include a typical case fill percentage but they don't say who or where their test data is performed or if it's like a couple of other places that use data generated from QuickLoad and one of those is Berger Bullets who's data is very conservative to be on the very safe side. Go the other way and you may find someone like Nick Harvey who's load data you have to be very careful with because maximum could be dangerous. Talking with Nick either in person and/or on the phone makes you wonder, great bloke, great history BUT....!!!

[Apollo]

Stix, I don't see where I contradicted myself but you may read something I don't so please point that out if you wish.

The Topic Post is " a faster powder for a light bullet".... BTW I don't call them projectiles as I think that is an incorrect term. A projectile is anything that can be projected forwards ie like a paperclip... whereas a bullet is what is used in a firearm. SO...

We have a Cartridge Case, any case, any calibre. Someone like Hodgdon USA has a test facility and test Barrel/Chambers which are hooked up to pressure censors and give you pressure and velocity readings then they test a variety of powders from any number of suppliers. Remember Hodgdon do not make ANY powders. Then we have Nosler and maybe a couple of others who write load data that may use a RAIL GUN to do actual testing but different to Hogdon quote their accuracy test on a known target and put that in their manual.

Now, somewhere there was a published data that went with powder loads and actually quoted a burn rate down say a 24" barrel then compared that to target accuracy. I think the ideal was of course 100% burn before the bullet exits the barrel but in the same article I think from memory it went like 80% travel was ideal for what one wants to achieve which in my mind is that there is a total burn when the bullet has traveled only 80% of the barrel length so the last 20% it's actually slowing down..?? Or it's still traveling at maximum pace because the gas pressure has reached it's maximum and can't escape before the bullet exits. The flame is still there so I wouldn't doubt that at night you will see a Muzzle Flash from any firearm rifle/pistol.

The powder load should have finished burning all the available powder before the bullet leaves the barrel, back a bit but pressure behind the bullet is still building to keep pushing the bullet. Gas expansion but you don't want that to finish early. Remember it's a burn, not an explosion. A progressive burn just like a huge spring behind something pushing it faster and faster until the spring comes to an end.

Now, on Nodes.... Most every powder load and calibre has at least two if not more nodes of accuracy. Remember that you are tuning barrel harmonics so that the barrel vibrates the same each and every time at the same time when a bullet leaves the barrel end (muzzle) so it spits the bullet out in the same plane each and every time. Some of those nodes are very narrow in as far as a powder load, hence find your best load then fine tune it a fraction of powder. In general those lower velocity powder nodes are rather wide and due to variations of your own and/or the day you will get greater overall average accuracy. So the lower node may be more kind.

Now, some long range target shooters strive for maximum velocity..ie 1,000 yards.. and love the near push the load to it's maximum but they might find they have to adjust loads to the conditions each day. Some load at the Range and change every detail they shoot depending on a guess of the conditions.

We are getting way off track so I'll stop.....

[Oldbloke]

+1 Apollo.

Just a side note. Powder Granual shape can also effect the burn rate.

I am going on the general typical ADI extruded Rifle Powders. They are all the same shape granule just vary in size. I have no knowledge of their other powders nor does my friend who used to work at ADI testing powders. ADI Double Base and Imported Powders are a different animal.

For ADI rifle powders I believe you would be correct. But over the years many shapes have been and still are used in the industry. Changing the shape changes the surface area. A larger surface area will result in a faster burn rate.

Tube shaped as opposed to the usual "bar" shape would be just one example.


https://www.vihtavuori.com/tech-blog-po ... nd-shapes/

[in2anity]

Awesome response and just the level of detail I was after SJ - thanks mate What you said totally makes sense - lighter pills spit out faster so you need to get the burn done sooner.

With respect to 2208 vs 2207, I hear you, but I’m reloading for economy - 2208 is basically 10grs more - and 2207 is one of my go-tos for other calibers.

So SJ do you feel a faster powder in a listed region is basically harder on the throat?

The 308 is not hard on barrels and you are unlikely to notice significant shortening of the barrel life by using 2207. But I would not use it because you will usually see better results with 2208 because it fills the case better and should have a more reliable consistant burn. Save the 2207 for your 45/70.

Yet to chronoed, but showing promise.

02D37024-0EAF-4F20-9DAE-160344D78DAF.jpeg (1 MiB) Viewed 5306 times

[SCJ429]

Nice work, using 2207 isn't holding you back. The Speer TNT is such a great bullet, the price gives no indication just how accurate they can be. What rifle are you using?

[SCJ429]

Sorry I can see you wrote Tikka CTR on the bottom of the target.. No wonder you are doing well. Great bullet and the best factory barrel around equals good results.

[in2anity]

Nice work, using 2207 isn't holding you back. The Speer TNT is such a great bullet, the price gives no indication just how accurate they can be. What rifle are you using?

Sure is - I think it was you who said it “shoots way above its price point”. Well put. That’s out of a 20” tikka ctr - boringly accurate rifle. I want to try these loads at 500m next to some regular high-performing loads - I’m curious to see how much the wind knocks them about.

[SCJ429]

I have shot 7mm 110 grain TNT out to 300 metres and they can group quite well but their terminal performance starts to drop off. I would not use them for hunting at ranges longer than this.

[in2anity]

I'm not giving up on the speer bullet in the ruger blackout over 2205 - I've been playing with seating depths and I feel I'm closing in on a sweet spot.

[Stix]

I have shot 7mm 110 grain TNT out to 300 metres and they can group quite well but their terminal performance starts to drop off. I would not use them for hunting at ranges longer than this.

Hey SCJ...im curious to know more about your experience with theae...
What were you shooting them in (i mean cartridge & velocity)...?
Group sizes at 300...?
Also, what animals do/have you hunted with them , to say you wouldnt use them beyond 300...?

[SCJ429]

I am using a 7mmBR case and get around 3,000 fps out of them. It shoots about 1.2 inches at 300 in good conditions. I have used it on goats and pigs but a few times the animal has run off on me far enough so it took a lot of looking to find them. When opening up the chest cavity I did not find a lot of damage. When shooting at 150 metres the same shot does a lot of damage but closer to 300 it doesn't seem to be going fast enough.

A 7mm08 or 308 would be going a bit faster which would help in this regard.

[in2anity]

So riddle me this batman - why is 2207 popular in the 45-70? Out of a 24" bbl, woiuldn'y you want something slower?

[duncan61]

Its a straight walled case

[in2anity]

Its a straight walled case

Implying that all straight-walled cases require fast burning powder? So what's with all the listed mid-burn loads such as AR2206H and even 2208? The question is not what, but why.

[Stix]

I am using a 7mmBR case and get around 3,000 fps out of them. It shoots about 1.2 inches at 300 in good conditions. I have used it on goats and pigs but a few times the animal has run off on me far enough so it took a lot of looking to find them. When opening up the chest cavity I did not find a lot of damage. When shooting at 150 metres the same shot does a lot of damage but closer to 300 it doesn't seem to be going fast enough.

A 7mm08 or 308 would be going a bit faster which would help in this regard.

Thanks scj...good to know...
Ive currently got them for 7-08...ive only shot 2 goats & 2 sheep with them late last year & early this year, but didnt open them up...

Havnt had a chance to get bsck out again since...hopefully that changes sooner than later...