The elements of an Accurate Cartridge

[Grimstod]

Give me your thoughts and feedback after you have read these please.

1. Cartridge must have a shoulder to arrest brass flow and prevent donuts.
____a. Not enough should and brass flows to fast also headspacing tends to be less precise.
____b. To sharp and ES goes up as has been proven in some BR 30d vs BR Ai tests.

2. Cartridge must have enough room to seat the bullet with the base past the neck shoulder junction.

3. Cartridge must have a long enough neck to hold the bullet and chase the lands as the barrel ages.
____a. If there is not enough neck, moving you loaded round from box to chamber during a match can harm runnout.
____b. If you cannot chase the lands then you will not be able to shoot very long on a single barrel unless it is very under bore.

4. Must have quality brass available. (Lapua)

5. Case head must be strong enough to hold a primer for many reloads.
____a. The more reloads it can handle the more often it can be reloaded.
____b. Minimum of 50 reloads is needed to make for a truly long lasting case.
____c. Lots of brass around the primer is needed to keep them from coming loose.

6. Needs to fit in standard size actions or actions.

7. At least 1500-2000rd barrel life to get you through a shooting season.

8. Manageable recoil. If you are scared of pulling the trigger it wont shoot accurately. The limit here is the shooter.

 

[/VH]

6.5 x 47 Lapua.!

 

[dkhunt14]

Not sure what you are asking.

Number 1. I believe all brass flows some regardless.

Number 2. I believe when you seat the base past the shoulder neck junction, accuracy becomes unrepeatable. I think the pressure ring needs to be in a sized portion of the neck for accuracy.



Number 3. Some cartridges hardly move. A 300 WSM for example doesn't move .005 in 1000 rounds. Also if a cartridge let's a bullet move from box to chamber, it is not a good cartridge.

Number 4. There is nothing wrong with Norma or RWS.

Number 5 is important.

Matt

 

[dragman]

I think the most important element of an accurate cartridge is:
Knowing all the things that are listed and understanding them. If you know what good brass is, if you know how to set headspace and size brass and chase lands, If you have a chrono and know what ES's to look for you will have accurate cartridges no matter what your shooting.

 

[Grimstod]

I added two more I just remembered.

 

[SheepDog]

I always thought that the more square a cartridge was the more potential accuracy it had. Big diameter short cases seemed to be a trend for a while but I don't hear much about it any more.
A 30 to 40 degree shoulder would be about right
I like necks that are about two calibers long but I don't know if that would make it more accurate or not.
The difference in the hardness of the brass is due to the forming process used and when it is annealed during the process.
A larger diameter case would provide more material around the primer for durability.
A short or standard action would have to fit a "fatter" cartridge for a short fat case.
The life of the barrel is relative to the pressure produced and the speed of the bullet.
Smaller bullets with less powder give light recoil but you need long bullets and enough powder/velocity to keep the speed well above the speed of sound all the way to the target.

MY concept is to take a cartridge like the 300 ultra mag or even a cartridge as big around as the 50 BMG and make a case that is one inch from the base to the shoulder, put a 40 degree shoulder on it and a neck that is for 6mm that is about a half inch long. It would use a fairly slow burning powder behind a 120 to 140 grain low drag bullet.

Although I thought of this many years ago I have never built it. It would be an interesting project.

 

[Grimstod]

I like necks that are about two calibers long but I don't know if that would make it more accurate or not.
The difference in the hardness of the brass is due to the forming process used and when it is annealed during the process.

This is one reason I do not think the Dasher, as good as it has performed is not the ultimate answer for 1000 yards or more.

 

[dkhunt14]

This is one reason I do not think the Dasher, as good as it has performed is not the ultimate answer for 1000 yards or more.

If you are shooting BR the neck length like a Dasher is not a big factor. Most the top guys are rechambering at 500 to 1000 rounds. Others are replacing barrels at 1000 rounds. If you want to win a lot it is what is needed. That is why i shoot another gun in the shotoffs. I save my good barrel for the aggregates and big shoots. Matt

 

[dkhunt14]

I always thought that the more square a cartridge was the more potential accuracy it had. Big diameter short cases seemed to be a trend for a while but I don't hear much about it any more.
A 30 to 40 degree shoulder would be about right
.

The winning cases in 1000 yard BR are 6 Dasher and 300 WSM. They both are on the short side. It is about having the capacity to get the velocity needed with a fairly full case of the right powder. Not crunching the powder or having excess airspace. The two above mentioned cartridges both do that. Matt

 

[Ggmac]

Sheepdog, I did that 25+ yrs ago . I to of a 460 Weatherby , made it anywhere between 1.75 to 2 inch , I had more than a few reamers . 35-40 degree shoulder and numerous neck lengths and diam . It was in 6.5
No great miracles .
A case isn't necessarily accurate , it can be efficient!
Accuracy search is better focused on barrels and projectiles. Not to mention SHOOTER SKILL !

 

[Ggmac]

Forgot to mention , my experiment wasn't new it was based on a 348 win case necked down to 6.5 , that was about 10-15 yrs earlier than mine .

 

[Grimstod]

If you are shooting BR the neck length like a Dasher is not a big factor. Most the top guys are rechambering at 500 to 1000 rounds. Others are replacing barrels at 1000 rounds. If you want to win a lot it is what is needed. That is why i shoot another gun in the shotoffs. I save my good barrel for the aggregates and big shoots. Matt

I agree that neck length does help in barrel life but would consider the over bore ration a larger factor.

 

[dkhunt14]

I agree that neck length does help in barrel life but would consider the over bore ration a larger factor.

I believe if the Dasher had another .100 neck length it would double the rounds of accuracy. The TP point would be back in the case instead of in the throat. Matt

 

[savagedasher]

The new dasher brass has a longer neck but It also has less case capacity . In time we will know how it work out . Larry

 

[Canadian bushman]

I think i hold #4, #7, and #8 in the highest priority.

A cartridges reputation for inherent accuracy and tuneability probably tops my list.

 

[Grimstod]

The new dasher brass has a longer neck but It also has less case capacity . In time we will know how it work out . Larry

From what we have seen so far its not faring to good. The larger flash hole is a killer and brass life is no where near as good.

 

[dcali]

1 (Brass flow): I don't care about this at all, nor do I think we understand the impact of shoulder angle as well as we think we do.
2 (Base past the neck/shoulder): Not sure which direction you mean here, but this has more to do with overall case size. If you're seating too far in or out, you're probably pushing the edges of your chosen cartridge for whatever reason (probably because you are shooting F TR, or something like that). In other words, I don't care assuming the body is sized appropriately for the bullets to be shot.
3 (Long enough neck): A longish neck is a luxury in that it provides flexibility in bullet weight. I suppose it can be overdone.
4 (Quality brass): This is important.
5 (stong case head): This is also important. Small primers should be used if possible. This is how most of my brass dies.
6 (Fit standard action): non-negotiable. If I'm not buying some weird rifle just to use a specific cartridge. The standards are perectly good.
7 (Minimum barrel life): I would be hard pressed to shoot something I didn't expect at least 1,500 rounds of service from.
8 (Recoil): Totally application dependent. Less is always better, all else equal, but that's pretty obvious and all else is never equal.

One thing I've not really seen addressed except by speculation is the size of the cartridge base. The conventional wisdom is that short and fat is better, but I wonder if that's not because so much success has been had with the 6PPC. The advantage of a longer, skinnier case is that the same volume case has a smaller base, and therefore lower bolt thrust, which is a primary driver of barrel vibration. The reason given to not do this is usually something along the lines of "combustion isn't as good", but I'm not sure I've seen any conclusive evidence of that - just lots of theorizing and head scratching.

In other words, if you took a 6PPC and lengthened it until it had the same capacity as a 6BR, but retained the smaller case head, would you have a better cartridge than the 6BR?

 

[savagedasher]

I think a dasher or a brx is about the same class for mid and long range as a ppc is for short . Larry

 

[IdahoSharpshooter]

Does anybody really compete past 1000 yds with a Dasher? It seems awfully hard to beat one on a regular basis with anything else out there.
Or, is that just me...?

 

[Grimstod]

1 (Brass flow): I don't care about this at all, nor do I think we understand the impact of shoulder angle as well as we think we do.
2 (Base past the neck/shoulder): Not sure which direction you mean here, but this has more to do with overall case size. If you're seating too far in or out, you're probably pushing the edges of your chosen cartridge for whatever reason (probably because you are shooting F TR, or something like that). In other words, I don't care assuming the body is sized appropriately for the bullets to be shot.

1 You should care about brass flow. It means more trimming and that reduces the amount of brass you have in the case itself. Thus changing the way it shoots. If you have a lot it will not be as exactly consistent from shot to shot.

2 I was talking about seating it below this area. Doing so makes you vulnerable to the dreaded doughnut. And that is just plain bad for accuracy period.

I like your thoughts on the PPC base size. I think lengthening it has been tried though. Check out the 6AR I think it has same capacity as the 6BR but could be mistaken. Most say though that the 6PPC is accurate because the of the case proportions. Not the base size. Then again though we really do not know why its accurate. All the things I listed though do fit its description though.[/QUOTE]