Safe minimum loads...double detonation??

[Lonewolf74]

I've heard about this double detonation thing happening with too light of load in certain cases and powders. I was wondering if anyone could explain more of this to me?

Would it be safe to go a grain or 2 under book minimum in most case's?

Also is there a point where you have too much bullet jump to the lands to be safe? Now I'm not talking a bullet seated down to where the ogive is below the case mouth or something that extreme but seated like .150 off the lands?

I ask these questions cus I've got a few rounds that I forgot to increase my powder charge while going to a lighter bullet which put me 2 grains below book min. Then I have a few rounds with bullets seated a fair ways from the lands while getting my die set. For curiosity sake I'd like to shoot these and see how they compare to my other stuff but wanna be safe

 

[Lonewolf74]

I should add for this particular application it's a 243 win with 95 gr bullets and 31 gr varget powder. Book min was 33 gr varget for 95 gr and best I can tell from the burn chart varget is on the faster burning end of powders for this cartridge.

Any help or advice is appreciated

 

[Edd]

Based on what I've been told by people whom I consider experts, I wouldn't load any cartridge to a fill of less than 80% of it's case capacity unless it was with a powder that was suitable for a reduced load. I don't Varget is one of those powders and I think your load is less than that. I think you are using the wrong powder anyway. I would use H4831.

 

[Svnmag]

Yes 4831

 

[CatShooter]

Gun powder does not "detonate", it burns. The only thing that detonates is the primer. Powder "deflagerates", and cannot be made to detonate.

If the powder charge is too light, it cannot keep the bullet going and then the bullet comes to a stop in the throat. Once that happens, it is impossible to get it going again, and the pressure continues to rise until the gun burst (it explodes, not detonates).

1 or 2 grains under starting load is fine.

 

[Lonewolf74]

Thanks for the reply's. Varget is not my first choice of powder I'm only using it to do this fire lap and coating process I'm trying out on this rifle. For the lapping the directions say to use the lightest charge of the fastest burning powder you can so I happened to have some varget and I found load data for it on hodgon's website.

Then I loaded some 95 gr plinking bullets to do the barrel coating process and figured I might as well stick with the same light load but forgot to increase the charge for the lighter bullet for the first 3 rounds. No big deal if I don't shoot em but I'm curious if I can SAFELY?

 

[J E Custom]

I've heard about this double detonation thing happening with too light of load in certain cases and powders. I was wondering if anyone could explain more of this to me?

Would it be safe to go a grain or 2 under book minimum in most case's?

Also is there a point where you have too much bullet jump to the lands to be safe? Now I'm not talking a bullet seated down to where the ogive is below the case mouth or something that extreme but seated like .150 off the lands?

I ask these questions cus I've got a few rounds that I forgot to increase my powder charge while going to a lighter bullet which put me 2 grains below book min. Then I have a few rounds with bullets seated a fair ways from the lands while getting my die set. For curiosity sake I'd like to shoot these and see how they compare to my other stuff but wanna be safe

Some cartridges can get away with minimum loadings others cant. The larger the case capacity the more likely you will have problems because of the air space in the case. Powder has it's own oxidizers and the more free airspace you have, the more oxygen the powder has to burn changing the burn rates. (Making it faster).

Squib loads can produce a double ignition and should be avoided because they can produce excessive pressures. If you get this "Double ignition" increase the powder charge and don't shoot any more of the reduced load for safety. the book minimum loads are only a guide and if you want less pressure than listed, look for the slowest powder listed for that cartridge and load to a case density of 85 to 90%.

IF you load to mag length or SAMMI length you will not have any problems with seating depth.


J E CUSTOM

 

[CatShooter]

Powder has it's own oxidizers and the more free airspace you have, the more oxygen the powder has to burn changing the burn rates. (Making it faster).

J E CUSTOM

Smokeless powder does not use oxygen to burn, because it does not "burn".

It cannot use oxygen from air. The nitrocellulose molecule is made up of it's own oxygen, carbon, and nitrogen.

When lit, nitrocellulose decomposes and releases oxygen, it does not consume it. Whether there is air in the case or not, it has no effect on the powder or the ultimate pressures in the chamber.

 

[Edd]

Gun powder does not "detonate", it burns. The only thing that detonates is the primer. Powder "deflagerates", and cannot be made to detonate.

If the powder charge is too light, it cannot keep the bullet going and then the bullet comes to a stop in the throat. Once that happens, it is impossible to get it going again, and the pressure continues to rise until the gun burst (it explodes, not detonates).

1 or 2 grains under starting load is fine.

Smokeless powder does not use oxygen to burn, because it does not "burn".

It cannot use oxygen from air. The nitrocellulose molecule is made up of it's own oxygen, carbon, and nitrogen.

When lit, nitrocellulose decomposes and releases oxygen, it does not consume it. Whether there is air in the case or not, it has no effect on the powder or the ultimate pressures in the chamber.

So, which is it?

 

[CatShooter]

So, which is it?

I am sorry... but what is your misunderstanding?

Neither comment conflicts with the other. They are about two different things.

The word "Burn" has a loose language meaning (gives off heat and light) and a technical meaning - oxidizes a receptor substance and gives off light, heat, and oxides of the substance.

Smokeless powder actually deflagerates, but we do not use language like that in common conversation.

 

[J E Custom]

Smokeless powder does not use oxygen to burn, because it does not "burn".

It cannot use oxygen from air. The nitrocellulose molecule is made up of it's own oxygen, carbon, and nitrogen.

When lit, nitrocellulose decomposes and releases oxygen, it does not consume it. Whether there is air in the case or not, it has no effect on the powder or the ultimate pressures in the chamber.

Well lllllllllllllll. I have to disagree with all of this post. Nothing personal.

Smokeless powder "DOES" Burn, and it has to have oxygen to do so. It creates it own oxygen so it can burn in confined spaces. (Like a cartridge case) extra air/oxygen in the case can add to the amount of oxygen increasing the burn rate of the powder that is controlled by the size and shape of the grains of powder. The mixture is essentially the same but the size and shape varies depending on the desired burn rate.

Explosives, Detonate and there fore cannot be used in firearms because they cannot be controlled to maintain pressures to a safe level.

Cartridge Cases with to much air space can be very dangerous and are normally dealt with the use of a filler to reduce the air volume in the case.

Squib loads can and often exceed SAMMI pressures because of the case volume and is the reason
that ALL loading manuals have a warning about Squibb loads and list only minimum load that can be safely used.

Nothing can burn without oxygen (One of 3 parts required to make fire) and Unless it can generate its own oxygen, it has to come from other sources.

Question? Is this a test? Ha Ha.

J E CUSTOM

 

[Edd]

I didn't think it was the air in the case that caused the issue. I thought it was the large surface of powder that could be ignited by the primer causing it to burn faster.

 

[CatShooter]

Well lllllllllllllll. I have to disagree with all of this post. Nothing personal.

Smokeless powder "DOES" Burn, and it has to have oxygen to do so. It creates it own oxygen so it can burn in confined spaces. (Like a cartridge case) extra air/oxygen in the case can add to the amount of oxygen increasing the burn rate of the powder that is controlled by the size and shape of the grains of powder. The mixture is essentially the same but the size and shape varies depending on the desired burn rate.

Cartridge Cases with to much air space can be very dangerous and are normally dealt with the use of a filler to reduce the air volume in the case.

Squib loads can and often exceed SAMMI pressures because of the case volume and is the reason
that ALL loading manuals have a warning about Squibb loads and list only minimum load that can be safely used.

Nothing can burn without oxygen (One of 3 parts required to make fire) and Unless it can generate its own oxygen, it has to come from other sources.

Question? Is this a test? Ha Ha.

J E CUSTOM

You must have missed out on 10th grade chemistry.

Smokeless powder (C6H7(NO2)3O5) contains more oxygen that it can use when it breaks down.

6 carbons
7 hydrogen
3 Nitrogen
11 oxygen

So, when the heat and flame are done, there is still unused-uncombined oxygen left over. It does not use "air" in the process.

 

[338Rocket]

This post does a good job of explaining detonation, at least how I have always understood it.

Now he goes into cartridges that I have no experience with, but the idea is the same, too little powder can create an over pressure situation.

http://www.longrangehunting.com/forums/f19/rem-700-action-limits-52987/index2.html#post363229