What is the most important aspect of a BR Cartridge?

[brianlewis]

Greetings, my first time on here and hope you can clarify some issues for me. I have only been involved in centerfire for three years, so I am an amateur. If we look at BR and PPC cartridges, I am assuming the first examples of each kind were developed over a period of time, tweaking specifications as they went.

If you look at PPC and BR cases they both have 30 degree shoulders, they are close to 1.52 inches in length, and the start of the shoulder is 1.075 inches from the base/rim (case length x 0.7072). The diameter of the case and the length of the necks aren't so consistent.

So I am trying to learn if all three dimensions listed - case length, shoulder angle and place where the shoulder starts, all combine to produce a great cartridge, or is there any one specification that contributes the most to the success (accuracy) of these cartridges. I know the rifle is a big part of the accuracy equation and may be the most important contributor to accuracy, but I want to leave the rifle out of this picture and just address the cases.

Thanks, Brian

 

[artbosco]

So I am trying to learn if all three dimensions listed - case length, shoulder angle and place where the shoulder starts, all combine to produce a great cartridge, or is there any one specification that contributes the most to the success (accuracy) of these cartridges?

You might want to consider the small flash hole and primer.

"Developed by Louis Palmisano and Ferris Pindell, the 6PPC is the “King of the Hill” in short-range benchrest competition, the most accurate cartridge ever invented. It completely dominates 100- and 200-yard Group BR Shooting. If you want to win in that game, you pretty much have to shoot a 6PPC, or some derivative of the 6PPC design. Easily made from Lapua 220 Russian brass, the 6mm PPC, like the 6mm BR Norma, has a small primer and small flash hole. The small flash hole/primer accounts for much of the 6PPC’s superior accuracy, though nobody really knows precisely how or why."

Source: http://www.accurateshooter.com/cartridge-guides/6mmppc/

 

[brianlewis]

LawrenceHanson - I don't think you are obfuscating, it is the kind of insight that I was looking for, way deeper than the surface I was scratching at.

Outdoorsman - Small primer and small flash hole is even more interesting than I bargained for, and the fact that it is not 100% understood how they interplay, that is even better. I know there is something similar with the 22 Hornet when you use small pistol primers rather than small rifle primers, gives you better accuracy.

Thanks.

 

[SmokinJoe]

The very short answer to your question: Available brass. The cartridge geometry was worked out through engineering and experimentation, but all the cartridge developers would tell you that getting those cases in high quality brass is the key to success. If you want to experiment some time, try two or three different brands of brass in a good shooting rifle with Lapua as the final brand. I think you will find that the Lapua gives noticeably better results, especially if you don't sort any of them. Have fun learning.

 

[brianlewis]

I think you will find that the Lapua gives noticeably better results, especially if you don't sort any of them.

SmokinJoe - Is that because the Lapua brass is more uniform dimensions/specs than other brass? So how does other brass compare to Lapua if they are sorted and uniformed? I know all brass is not the same thickness, is Lapua thicker than other brass and does that play a part?

I appreciate the feedback on this, and yes Joe, I am having fun learning about all this stuff.

 

[Webster]

There are far more knowledgeable people on the Forum than I. In the 6BR section of this website it states that the 22PPC, 6PPC and 6BR are the most accurate cartridges in the world. The PPC is rarely shot beyond 300 yards in competition. If most of us bought two $3000 bench guns with $1800 scopes, one a 6PPC and the other a 6BR I don’t think most of us have the time or skill to tell the difference. You didn’t state if you were interested in a hunting or a target gun. I bought a 6BR because it has more velocity than a PPC and it has very good barrel life. I have shot many groups under 0.350” with a 40 year old Remington factory stock and a 40 year old Unertl scope. It’s a 1972 Rem 700 with a Kreiger 6BR Norma 1:14 barrel, Jewell trigger and glass bedded, nothing else done to it. This is more than good enough for varmint hunting out to 400-600 yds. When you read about people shooting .25” aggregates at 100 yds. You have to remember that these people are among the best shooters on the face of the earth.

 

[BoydAllen]

Actually, shooting a .25 aggregate at 100 yards means that you are more of middle of the pack guy, at almost any benchrest match, if your match conditions were good.

Equipment is huge. I have a couple of friends that I have gotten started with their 6PPCs, and they both have been able to shoot groups in easy conditions that were under .2. They have two things in common, they have the right equipment, and they don't blow me off when I tell them how to get there.

Generally, when I have done everything that I wanted to, during a practice session, on a day when the conditions are easy, I will look around to see if anyone has been paying attention, and if there is, ask him if he would like to try a few shots. What generally results is the smallest group that he has ever shot. After which I point out to him that he may want to re- evaluate just how much shooting talent he really has. Like I said, equipment is huge.

As far as case design goes, for what ever caliber, give me a short, fat case, of good quality, shooting excellent bullets, down a top grade barrel, from a properly dimensioned chamber.

 

[Tozguy]

Talking about cases, after recognizing the similarities between the 6PPC and the 6BR Norma, why does the 6PPC seem to be more popular than the 6BR on equipment lists? Is there a finer point about the 6PPC that gives it a technical edge over the 6BR for benchrest?

 

[Frankr]

I really dont know for sure at this point but it seems my 6BR's have been able to shoot groups in the low to mid .100's easyly..and i seem to know several other fellows who can do the same with their 6BR's.
so why cant the 6BR shoot right there with the 6ppc, not sure at this point...but it might just have to do with the 6ppc works so well with a full to a packed full case of powder and you cant get no more powder in it..in the heat of battle-in a match-if things arent going well or you are not shooting well the first thing you want to do is change the load and you are usually in a panic but cant get too much more powder in the case,maybe just enough to tune it, i think sometimes that works very well in actual BR competition..when that scenario happens with the 6BR you can get too much powder in there and that causes problem's with a upset rifle,cases,shooter,targets ect..
And i do think the 6ppc is slightly(i do mean slightly)more accurate..
Now if you do follow match results,,as i do.. you will see that most BR shoots are won with a AGG in the high .100's(example .1887) yea thats 5 -5shot groups that measure that.. the super shoot was won with a .1538 agg.(a .1538 is very close to a world record) with the first three shooter agging under a .200.. and that what i look at how many shooter agged under .200 and how many shooters agged under .250..the super shoot would have say the top 25 shooter agging under .250 out of three hundred. but say at most matches the winning, the very best say one or two agged under .200 and only the top three or four agged under .250 so it would seem there are alot of aggs over .250, say in the mid .300's to .450's.. And under stand it is very hard to shoot a .250 agg at a BR shoot. so i shoot the 6BR because its what i like to shoot and i think the 6BR is just more fun.

boyd is wrong, if you show up at a reg/benchrest shoot at shoot a .250agg you should be in the top five to ten.unless you are at the super shoot then you might be 25th-30 out of 300 so a .250agg is allways better than mid pac.

 

[oldroper]

Talking about cases, after recognizing the similarities between the 6PPC and the 6BR Norma, why does the 6PPC seem to be more popular than the 6BR on equipment lists? Is there a finer point about the 6PPC that gives it a technical edge over the 6BR for benchrest?

When the BR first hit the market remington brass was the only thing made and there wasn't alot of interest in the BR case. Forget what year but the Sako 220 Russian brass ran out for the 6ppc so the 6br got another look again problem was Remington brass. Afew found out by shorten the BR case it shot pretty good and alot used the 7Br case just seemed to be a better case. Some were taking 7.6x39 cases making 6ppc brass some even turned the rim down on the BR case. When all this was going you had the 6mm VLD starting to take hold and then Norma made brass for the 6Br then Laupa brass hit the market for the 6ppc.

Shorten the Br case got in close to the capacity/velocity of the 6ppc and there was matches won and Dick Wright shot the shorten 22 Br for years.

 

[BoydAllen]

As a general rule, a fuller case is better than one that is less so, and with the powders that seem to give the best results for the range of bullet weights that work the best for 1-200 yd. benchrest, the 6PPC leaves less room between the base of the bullet and the top of the powder than would be the case with a 6BR. This is the reason that those who have wanted to use the BR case for so called short range benchrest, have generally shortened it, to reduce capacity, but of course making short BR cases is more work, and to what advantage?

 

[mikecr]

Whether cartridge design or gun design, per application, it's all bound and begins with the bullet.
Just put the dots on a board, and draw lines to dependents/precedents.
They will all center back to the bullet.

This applies to more than point blank range cartridges.