Making progress, more questions..

[mbohuntr]

Well, sorted my fired brass by brand, then weight... Worked up some accurate loads, and am now ringing 6" steel at 300+ yards. Shot 2" vertical spread, and 6" horizontal on a gusty day, so, not unhappy at all.

Question.... The brass I used was from a batch that had 2 distinct weights, 2-3 grains apart. All shots from the lighter weight group. If I switch to the heavier weight brass, it would reason to have less volume, therefore something should change with pressure/velocity... I'm in the middle of the charge range, so no safety issues, but what to expect??? more or less velocity??

2nd part, what about another brand of brass, same length, same weight, fired by same gun..? Same velocity??

Thanks,
Mike

[jim_k]

Brass weight is a crude measurement, not directly related to shooting small groups. Don't weigh it, just use same brand brass, with the same headstamp. The important measurement is the case capacity, and any decent brass will have consistent case capacity within the brand (Federal, Lapua, Norma, Nosler, Remington, Winchester, Barnes, other top brands). They will all have different case capacity compared to each other, though, so pick one and stay with it. Most shooters will use only their one chosen brand of brass.

[darkker]

Question....
1) If I switch to the heavier weight brass, it would reason to have less volume,
2) therefore something should change with pressure/velocity...
3) I'm in the middle of the charge range, so no safety issues, but what to expect??? more or less velocity??
4) 2nd part, what about another brand of brass, same length, same weight, fired by same gun..? Same velocity??

Lets get you some answers, So the question is what do you ACTUALLY want to know??
1) Would it "Reason"? Well, you COULD reason that. But unless you know what alloy and components everyone is using, you can't use that as any semblance of absolute. There was an article done something like a year or so ago, where they looked at several brands including the "cool" ones. Everyone uses a different mix, and don't always hold that mix anyhow. So, do you want to guess, or do you want to know? Knowing means measuring the volume, not making assumptions; your call.
2) In theory yes, the practucality of it may or may not be large. I missed what case you are dealing with, but smaller cases suffer much more than larger ones for minor volume wiggles. If you are loading by weight, it can aggrevate it moreso than loading by volume.
3) Depends. If you are using a comfortable fitting powder, meaning good case fill and not on the real slow or fast side of things. Then a tad more volume will slow you down some, but again the amount depends on many variables.
4) Goes back to the earlier comments about case brass differences. If you are told there are two different people who are the same height and same weight, that doesn't mean they are built the same. One could be muscled-up like crazy, and the other a donut packing super chunk. There was a VERY large study done, IIRC by the Pic arsenal; anyway they were studying case volume discrepencies on the 5.56 NATO case. Every machine on the production line had different states of wear, and so different normal tollerances for average case volumes they would churn out. The overal variances were stunningly large. So what cases are you talking about? If you are a "winchester" fan, they sold that business over a decade ago, and purchase on a "least-cost" bidding process. So whom makes their cases may change at any point. Further potentially exacerbating the issue.

Point being that if you really want to know all of these things you need to measure them.
Personally I load by volume, which is what extruded powder is designed around. This will control burning rate variables by volume much moreso than loading a case by weight. If you find yourself battleing case volume variation, you may want to consider it.

Cheers

[mjcmichigan]

Keep good notes, write down your observations.

Remember a grain is a 70th of a gram. A 1/10 of a grain is a 700th of a gram. It's tiny.

My 3006 cases, all R&P vary 20 grains.
My Norma brass on a 300 Winmag varies 4.. the r&p has two humps. I keep them seperate. Could be old vs new


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[mbohuntr]

Thank-you! I didn't consider the alloy as a weight factor.. I'm using IMR 4064 for .308, and H4895 for .223. I used all Hornady brass. I am building a log book that should eventually give me correct come up for all ethical ranges that I am capable of shooting. My thoughts are to eliminate most variables except temp, and have that compensated for in the log book.

What do you guys do to measure volume? I was thinking sand...

[jim_k]

You can use H4895 to good advantage in .308 Win as well as in .223. H4895 is temperature stable to a greater extent than IMR 4064. You load by volume by using "thrown" charges from a powder dispenser. The most accurate powder dispenser on the market, to my knowledge, is the Lee Perfect Powder measure. They are cheap enough, about $20, that you can get one for every powder volume you want to use. Do not use ball powder in them. They clog up. An RCBS powder dispenser with a micrometer attachment throws ball powder plenty well. Ball powder is harder to ignite, so best groups may need a hotter primer, either a magnum primer, or a mil-spec primer.

[mbohuntr]

You can use H4895 to good advantage in .308 Win as well as in .223. H4895 is temperature stable to a greater extent than IMR 4064. You load by volume by using "thrown" charges from a powder dispenser. The most accurate powder dispenser on the market, to my knowledge, is the Lee Perfect Powder measure. They are cheap enough, about $20, that you can get one for every powder volume you want to use. Do not use ball powder in them. They clog up. An RCBS powder dispenser with a micrometer attachment throws ball powder plenty well. Ball powder is harder to ignite, so best groups may need a hotter primer, either a magnum primer, or a mil-spec primer.

I use that measure and love it, thanks, I was referring to measuring case volume using some media to the top of the case and weighing that media to establish volume compairisons..

[foxx]

^^Water

[RC20]

Going by the vertical of 2 inch's. That's 1/2 MOA.

Wind is horizontal factor so hard telling there.

I would not bother with the brass other than my mfg.

Other factors have more input when you get down there.

Sizing, case fit to chamber, neck tension.

[mjcmichigan]

1+ water, 1+ neck tension, 1+ RCBS powder dispenser, then weigh on beam scale to verify and tweak. 1 necksizing, bump the should back 0.01 to 0.2 every time. (If using a bolt, if semi auto stick to fl


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[mbohuntr]

Just tried the water with the .223 cases, 3 grains difference with brass, absolutely no difference in volume.. :) weighed 2 cases of each group, set tare for each group, and weighed just the water.. 30.7 gr. each group exactly.

[jim_k]

That's the same weight number I use for my Winchester headstamp brass. Lake City and WCC are 31.0.

[darkker]

Do not use ball powder in them. They clog up. An RCBS powder dispenser with a micrometer attachment throws ball powder plenty well. Ball powder is harder to ignite, so best groups may need a hotter primer, either a magnum primer, or a mil-spec primer.

Aye Caramba!!! Lots of problems in that sentance Jim. Ball powders in the Lee work perfectly fine, been doing it for 20 years. The issue is a combination of things. 1 is the tightness of the drum, folks LOVE to over-tighten and then warp the plastic. Next is the static, wipe the internals down with very fine graphite BEFORE you use it and all is well. Last occasional issue is the drum rotation stop. Some who don't coat the internals will have a sticking issue. pull the drum apart and snip it off, and you can dump the drum verticle if you like. The REAL reason to be cautious with volume compared to extruded, is due to ball powder having coatings control burning rates, not geometry.
As for the "Ball powder is harder to light, and use a mag primer". Roy Weatherby himself hated shooting his rediculous cartridges at full power. We know that, because at the time it was well known that he was using some VERY old tech ball powders(the only thing with a slow enough BR to make his creations work) and was downloading his cavernous cases massively. 300WBY case with 30-40% case fill. Well he came back from an elk hunt in the Rockies and convinced Federal and apparently the general population, that we "needed" a magnum primer to light that devil ball powder when it's cold....

So lets re-cap:
1930's cars were a POS, compared to what we have today.
1930's ball powder when filling a WBY case under 50%, is very hard to light.

If you want to make this a fair comparison and look at ball powders that are even remotely modern, then ball powders are VERY easy to light. Infact changing to a mag primer in several applications won't even change your pressures. Look at the pressure traces below, the only thing changed in that load was the primer.

[mbohuntr]

Am I correct in my assumption that if two different head stamps are fired in my rifle, then weighed identical using water, they will shoot the same?

[foxx]

No, that is not correct.

THe brass is still different. Once you sort by headstamp and do all of your other prep, sort by volume.

Does it make a whole lot of difference, practically? Maybe not in your rifle and application. But, in theory, volume is just one (maybe final) way to sort of many.

[jim_k]

See for yourself if the cases with the same weight shoot to the same POI. I would recommend only trusting ones with the same headstamp. Thanks for the information in the post above, regarding the Lee dispenser and ball powder. Looks like good info.