What’s the benefit of having a long necked cartridge?

[elkaholic]

Lots of good discussion! I have no doubt that there are MANY factors that can and do affect throat life. Many of these are obvious, and some maybe not so much. I am convinced that there is a very complex dynamic that takes place in the milliseconds that it takes during the ignition and burn process. Much of exactly what happens with all the different designs, powder burn rates, temperature differences, pressure, barrel quality, cleaning procedures, etc. etc., and there interrelationship, probably nobody understands fully. I CERTAINLY DON'T!
Here are some things that we do know, and the results in competition don't lie. MOST of the newer successful cartridges have at least a 30 degree shoulder and a relatively long neck.They also are normally shorter case body designs, and often have less body taper than the parent case. Some of these things are related to throat and some just to better efficiency and overall performance. I personally believe that shoulder angle and neck length DO play a role in part of the dynamic. Of course there are extremes, but to say that there is no difference, I think would wrong thinking. I doubt that anyone would think an inch long neck is beneficial anymore than one would want an 1/8" long neck.
We can all find exceptions to point out, but lets look at the 6.5/284. Obviously a very successful cartridge but (known to be a barrel burner)! It does have a pretty good shoulder, but little neck length. We can't say, "ya, but everyone overloads them" because that is not unique to the 284!!
The flame point thing, as has been explained to me, makes sense. Anyone who has ever used a cutting torch knows that the hottest point is at the tip of the inner flame! This is accomplished by "squeezing down the angle" when you adjust the torch. Sure, a rifle chamber is enclosed, and much of the powder is burned farther down the barrel, but that doesn't mean its insignificant!
I am sure a lot of you have already seen this, and likely have your opinion set, but for those who haven't, below is a pic of what I mean. Before the laughing starts, no, I can't draw a stickman!
We all have our opinions, favorites, etc., which is just fine and the way it should be.
As far as the OP's question concerning a shorter case length, I do believe a shorter burn column is an advantage but having said that, I don't think .016" on a Nosler length case is very significant for that purpose.
As for me, I don't intend to change the case design on the SS anytime soon! Some have scoffed at the whole concept, but the people who shoot them see it a little differently!
It's kind of like the song about "Grandma got run over by a reindeer". (some folks say they don't believe in santa, but as for me and grandma, we believe)....Rich

 

[Brad7348]

You know, that totally makes sense in theory. But a 6.5-284 has a steep shoulder angle and its is known as one of the fastest barrel burners out there. It also has a reasonably long neck, or at least average to long compared to say a 300WM. That round burns a mid speed powder, 4831 or 4350 etc. So in its case, something else is burning up the throat. It has to be related to the velocity, or.... Has anyone looked at the amount of contact surace the bullet has with the throat. Meaning, what length of bullet do the grooves have to cut. Some of these heavy bullets are quite long for their caliber. 6.5 140Gr, 7mm 180gr, 6mm 115gr etc. If it is a VLD design, some of that length is ahead of the Ogive so it doesnt nessisarily make the surfase contact area longer, but as you move the Ogive out toward teh tip to make a heavier bullet at the same length, you get a longer surface area on the bullet which equates to more friction at the throat which should = more heat. Another think to think about... When we load rounds "jammed" into the lands, the ogive of the bullet doesnt completely seal the throat from the chamber. As the charge expands the case, masive amounts of pressure build up behind the bullet because there is no initial "jump". Durring this short amount of time, there has to be extremely high pressured, high velocity, superheated gas squezing between the bullet and the tiny spaces in the lands. I would think this would have some serious cutting properties. Imagine pointing a water hose at the ground, then sticking your thumb over the end of a water hose. The later makes a difference. In a bullet normally seated, the initial "jump" may be enough to jam seal the throat, so it never sees that cutting action from extreme pressure squezing by. It would be cool to have the opportunity to look at 2 rounds, one shot from a normally seated bullet, and the other shot from one that was jammed into the lands to see if there is a difference in the way the sides of the jacket look. (Basically to see if there is any evidence of heat cutting into the jacket at all between the score marks) You would think it would affect both sides right? Just a thought.

 

[J E Custom]

Hunter Benchrest is single loaded, they do require you use an action with a magazine cutout. Just an FYI...
Has anyone heard that ball powders are suppose to burn cooler and reduce powder flame cutting?

Wayne

Thanks Wayne.
I have built a few Hunter bench rest rifles and they had to hold 5 rounds in the mag and had weight limits, but I assumed that they had to use the mag in competition. It makes more sense to single feed.

The military prefers the ball powders for combat, because it is not as abrasive as tubular powders because of the shape, and in rapid fire conditions, reduces fire cracking because of the heat build up when rapid firing.

When interior bore surfaces get hot they erode faster and fire cracking is also possible this is why the military prefers ball powders. Burn rates have little to do with it in my opinions, Its the shape of the powder granules that military thinks makes the difference. (I cant prove it ether way except that military Armories have rifles that still shoot well enough to qualify after 50 to 75,000 rounds.

J E CUSTOM

 

[elkaholic]

The 6.5/284 still has the flame tip very close to the case mouth though. Also, it is considerably more overbore than a 300wm which is a significant difference. A lot we don't know so use what works!

 

[Brad7348]

The 6.5/284 still has the flame tip very close to the case mouth though. Also, it is considerably more overbore than a 300wm which is a significant difference. A lot we don't know so use what works!

I have to apologize on this one. I didnt read your entire post before mine to notice that you referenced the 6.5-284 in your example. It was the first thing that popped in my mind too, but I saw it from the other point of view. Agree there are so many factors in play, we will probably never know.

 

[redleg1013]

I will preface this by admitting that I am still damp behind the ears and smell of the plastic wrapper I was wearing. I had read over on a BR forum when it came to trimming necks, that one should do so only when it hinders chambering (they made mention of a Sinclair chamber length gage). The reasoning was that one, ideally a neck should be at least a bullet caliber in length. Two, that the increased length causes just that much more resistance to overcome, allowing pressure to build just a hair higher with the same powder load, more bang for the buck so to say. Three, in relation to point two, is longer barrel life, something about pressure correlation to velocity.

I think I saw this in a roundabout way through this thread, but I'd be interested to know if it is unfounded. I'll go try it myself when I'm not laid up, but for now I'll kindly ask for the voice of experience and take notes from there.
Thank you. (edited for spelling and grammar)

 

[elkaholic]

I prefer around 1.1 calibers of neck length depending on bore size and bullet length.....rich

 

[kfreeze]

Could you push the 28 nosler shoulders back like the 6.5slr?

Yes, but you have to use a die with less shoulder angle like a 7mm saum. Then if you fireform a 40° shoulder back into the case you lose minimal case capacity. A friend of mine did the 28 Rowland by doing that to the 28 nosler case.

 

[kfreeze]

Another benefit of a longer neck is that you get don't have the boattail of the bullet pushed as far down in the case taking up space for powder. It can also help get the bearing surface of the bullet up above the area on the case where the donuts like to form.

 

[Rifleman97]

Another benefit of a longer neck is that you get don't have the boattail of the bullet pushed as far down in the case taking up space for powder. It can also help get the bearing surface of the bullet up above the area on the case where the donuts like to form.

Personally though if I'm shooting a caliber with long/heavy for caliber bullets, I'm throating it long anyways, it has the same effect.

 

[kfreeze]

Personally though if I'm shooting a caliber with long/heavy for caliber bullets, I'm throating it long anyways, it has the same effect.

I do that also, however if a case has a short neck you can end up with either very little of the neck holding the bearing surface of the bullet, or the boattail pushed farther down in the case taking up powder space.

 

[elkaholic]

If a rifle is throated properly for a given bullet, the throat length would be adjusted so that the bullet would then fit properly in the neck. If it is a factory chamber/cartridge, it is what it is??

 

[wildcat westerner]

Longer neck = flame point = double extra barrel life, double accuracy , blah blah blah .... ALL bs ........ it's a selling point to the unwitting

a neck .257" long vs .308" will have the exact same throat life in same caliber case with same powder charge ...... a .050" longer neck WILL NOT give you a thousand rounds of extra barrel life much less 100

can you imagine how silly it sounds that the "flame point" cools so much in .050" as to double barrel life ?

folks .... the powder is still burning beyond the case mouth and into the barrel

I've played with long necked wildcats and have trashed those designs in favor of shorter necks, SD's have improved, accuracy has improved as well as better velocity prior to pressuring out

Swamplord, would you care to share with me, your exact testing to lead you to the conclusions you reached. Thank you in advance. Gene S.

 

[ScottMc7]

Longer necked cartridge doesn't give longer barrel life based on experience. I've used both and you wouldn't see any difference.