Load Density.

[Laurie]

Like you, I have been playing with Quick Load and wanting to test some powders that fill the case a little better than H4831SC. One that keeps comming to mind is N160 and N165 do to its lower BTU/KJ rating and higher fill ratio.

N165 is very widely used in the cartridge over 140s here in the UK - Viht powders are cheaper and their supply is more reliable than that of the American models, but in addition to those advantages it does work very well with 139-142gn bullets. I've also had excellent results from it in the smaller case 6.5X55mm.

There's certainly nothing wrong at all on that target and its verticals That's something I very rarely see on my long-range plots as both of the ranges where I do most of my LR shooting are in steeply sided valleys and wind often has a significant vertical component making it difficult to know what is behind some shots' positions. It's very common to hear competitors ask about the issue at the end of a relay and show relief if others had suffered the same problems at the same stage of the shoot.

 

[Laurie]

A friend, who builds his own rifles, built a .204, that shot very well, but had ESs in the +50 FPS range, with the most accurate powder, TAC, and 32 grain bullets. The powder was down in the shoulder. He shortened the chamber so that he can make cases from .223 brass, and his ESs went to single digit. The Powder is now slightly compressed. While it was very accurate before, he says that a test group, with the new, shortened chamber was literally in one hole. I believe that he shortened the .204 chamber by .080. He still gets velocities over 4,000 FPS. The same barrel was used for both chambers. He just set it back a little.

Boyd,

I've always thought the same thing about the .204 - ie that it has a longer case than need be. Like your friend, I had a 204 (factory Savage 12 LRPV varminter with 26-inch barrel) that shot very well indeed. I won the UK Benchrest Association 100yd Factory-Sporter class championship with it in 2011. It too never produced small ES values despite being able to produce groups in the low twos. I always assume that Hornady used the 223 Rem Mag case as its starting point partly to get the magic marketing 'fastest production cartridge' accolade, but also to stop the masses reforming other companies' .223 Rem brass as in the 20 Practical and Tactical. In any event, Hornady hit the big time and mades piles of money presumably, especially in the early days when there were no competitors - and well deserved too I reckon for having taken the huge risk involved in introducing a radically new cartridge!

The Savage LRPV is now a 223 and shoots 90gn Bergers very well indeed in short to mid range F/TR matches, but I still have a yen to try a shorter case twenty, so have acquired a collection of Berger 50s and 55s plus some Lapua / Dakota .20 tactical brass for a future fast-twist barrel .20 Tac rifle project. Everything I've read and heard supports the view that a relatively small cartridge case capacity reduction produces a big ES reduction in this example, so I'm living in optimism here.

Whether its purely a result of an increase in fill-ratio, or something else - well, that's a different and probably impossible to answer question. It comes back to that old perennial of why does the PPC beat various other similar designs. I've always tended to the view that hitting on the absolutely ideal powder charge weight / burn-rate / pressure build-up relationship with the calibre and bullet weight is the main factor. But who knows - if it works it works, and I'm happy to accept that.

 

[BoydAllen]

Thanks for the report. My friends .224 length .204 has one major difference between it and some of the other 20 caliber cases. The shoulder angle, and neck length for that matter, are the same as the .204. I think that having a sharper shoulder can help improve performance to some degree.

When Ackley discussed the advantages of his improved cartridge case shape, he wrote that either the sharper shoulder or the minimum body taper by themselves would give the desired result, although his designs had both.

Added later: On the point of the .222 mag case being a bit too long, I wonder how well filled the typical loads had the case. If we look back, before the advent of the PPC there were a number of wildcat cases, used in competition, that had body lengths somewhere between the .222 and its magnum version. Could it be that these resulted in a more complete fill with the powders that they were used with, and that that rather than their shorter powder column was their advantage over the full length .222 mag, (or perhaps is was both)? This is all before my experience in short range benchrest, so someone else will have to fill in the needed information.

 

[Webster]

You can get the same velocity from 90 or 102% density. It depends on the powder type. I think he was trying to relate accuracy to density not velocity.

 

[CatShooter]

I need to quite quoting Berger data, it's copyrighted. I will not enter my spreadsheet data for that reason.

Entering data from Berger's manual is not a violation of copyright - it is specifically addressed in the copyright laws under "Fair use".

You may repeat sections of material for a number of uses (including this), without violating the law, OR without upsetting Berger - it is free advertising for them.

 

[madderg]

Back at the end of the 1990's I designed a round call the 6MM284 Madd... what I based it on was a 284 case and the most accurate loads for it. Then I looked at how far up the case was filled, so I shortened the case to that length and gave it a longer neck to boot. I shot better speeds then any 6mm [ Remington 6mm, 243, 240 Weatherby mag., 6mm284] with less powder. I may bring it back to life in a 6.5 one of these days!! Bill Shehane did about the same thing in that era. Back then the go-to powder was H414 I seem to remember. Today it would have more options. My best group was with some Berger 60 something grain bullets, that topped out at 3930fps. and that was a 5 shot group at .044, man those were the days!!

 

[normmatzen]

Yes, Boyd, that's how I interpreted it.