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mixed brass. red herring?
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posted
In your experience does mixing brands of brass have any appreciable effect on the ballistics of a given reload recipe? If so can you quantify?
 
Posts: 337 | Location: Devon UK | Registered: 21 March 2002Reply With Quote
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Yes it does...just take it as that.

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http://stevespages.com/page8.htm

 
Posts: 3282 | Location: Saint Marie, Montana | Registered: 22 May 2002Reply With Quote
<Gary Rihn>
posted
Internal volumes may vary, sometimes considerably. In smaller cases, it can be enough of a difference to be dangerous. In any case, you could have differing pressures between different lots of brass, making for some interesting ballistic differences.
 
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<green 788>
posted
If you are using a non-optimized powder charge, the pressure differences caused by brass variations could affect POI enough to cause over MOA performance. The interior dimensions of different cases are not always the same. If you use the same charge in two different cases, the case with the smaller interior will generate higher pressure, and cause velocity changes, which of course will effect accuracy.

If you're using what I call an OCW (optimal charge weight, which I define as the amount of a given powder in a given load recipe that ignites and burns most consistently), you may find that the brass differences don't change your POI all that much.

If, on the other hand, you are using a reduced or over-charged load, the consistency of burn may be altered enough to screw up your groups.

An example is the .270 Winchester, using 130 grain bullets and IMR 4350. I discovered (like Winchester before me, it turns out) that the best charge of IMR 4350 to use in this recipe is 55 grains. I began development at 53.5 grains, and fired four shot groups with shots 3 and 4 being of .3 grains greater charge. My first four shot group was two 53.5 grain loads, and two 53.8 grain loads. I continued doing this until I found a string of shots which grouped fairly close together on the target. This is similar to the Creighton Audette method, but is easier (for me) to do. What I discovered was that 54.7, 55.0 and 55.3 grains of IMR 4350 in the above recipe all printed inside 1 1/4 MOA. This was using WLR primers.

My next step was to test primer variations using the 55 grain center charge, which represented the deepest part of the accuracy groove. Federal 210's tightened the groups up better than any others I tested, and I then had an honest 3/4 MOA load. Fine tuning was done by selecting Winchester over Federal cases, and altering the OAL. This load and rifle shoots to the same POI every time I try it.

I could have stuck with the 53.5 grain charge, because it did print a pretty tight group. The problem was that 53.2 grains and 53.8 grains didn't do well at all, so I wasn't in a very deep accuracy groove. This recipe would not have tolerated minor deviations well at all.

I can load five rounds of my 270 recipe using Federal and Winchester cases, CCI, WLR, and Federal primers, all mixed up, and vary the charge weights from 54.7 to 55.3 grains of IMR 4350 and still shoot all five shots into 2 MOA or under. That's a resilient load, and even though IMR 4350 isn't all that tolerant of temperature changes, the load recipe isn't as sensitive as it might otherwise be to outside temperature change.

Many folks decry the lot to lot variations of powders, primers, bullets, and cases. I believe that if they are noticing such variations, they are either shooting BR, or their load isn't optimized for charge weight (OCW). Fine tuning for barrel harmonics can be done with primer variations first, then distance to lands variations.

These are only my opinions, but I think they have merit. This method has worked for me. I used to do my load development by selecting an OAL, a case, a primer, and then altering powder charges. I have found that my loads are more resilient and more tolerant of minor component variations if I identify the OCW first, then play with the other variables afterward.

Dan Newberry
green 788

 
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If you are talking about hunting loads, unless you are motoring your loads at the ragged edge of the top end, different makes of brass will have little real effect. You see, the "percentage" of volume that is lost or gained would be very small compared to the total volume of the case. As posted above, small (.223 sized) cases would be more critical to variations in volume as the "percentage" of variance may be greater.

[This message has been edited by beemanbeme (edited 03-24-2002).]

 
Posts: 2037 | Location: frametown west virginia usa | Registered: 14 October 2001Reply With Quote
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I have seen up to 100 fps variance in velocities with identical loads.Point of impact varied up to about 1-1/2" at 100 yards with some loads.Overal group size went from 1" to 2-1/2" with one rifle and at least doubled in others.Overall the effects are very noticeable even in hunting loads.
 
Posts: 3104 | Location: alberta,canada | Registered: 28 January 2002Reply With Quote
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I used to think the same thing. But once you start studying your brass, you'll see differences even within the same lot. The more "anal-retentive" a person is about their brass the better. That is the vessel which sends the projectile on its way. getting every load the same or nearly the same is the key. Just like a golf stroke...consistancy. There are all kinds of tools for case preparation. Try some out and watch your groups tighten up.

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Bill

The early bird may get the worm, BUT the second mouse gets the cheese.

[This message has been edited by HHI 7371 (edited 03-24-2002).]

 
Posts: 247 | Location: Butler, PA | Registered: 26 February 2002Reply With Quote
<green 788>
posted
Such variances again are more noticable and significant in non-optimized loads. Again, if you achieve the OCW (Optimal Charge Weight, defined in my post above) these effects will be minimized.

Another example is the .243 Winchester using the 85 grain Sierra HPBT "Gameking" and IMR 4350. The OCW is probably around 40 grains, as 39.5, 40, and 40.5 seem to group pretty close on the target. I don't, in this case use the OCW because I want maximum velocity. I shoot 43.5 grains of IMR 4350 in the above recipe, and this is a charge sensitive, case sensitive, and primer sensitive recipe. As long as I keep the components consistent, groups from my Remington 788 run well under 1/2 MOA. (If you see me claim 1/2 MOA accuracy out of many of the rifles I speak of here, it's because that's the standard I expect from them. If they are incapable of 1/2 MOA, I don't keep them).

So again, the answer to the original quesion is *sometimes*. It depends on whether you're dealing with a load that is using the OCW or not.

green 788

 
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<stans>
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When I load 9mm or 45ACP practice rounds, I don't worry about brass brands, but these are not max loads. For maximum loads or match ammo, I always use brass by the same manufacturer.
 
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I have a 8x57 that I can take a Win case, a Rem case, and a Hanson case, use 54gr of H-380 and a CCI250 primer, then I can load a 150gr Speer, a 150gr Sierra, and a 175 Sierra, and shoot a group under 1" at 100yds.
 
Posts: 3097 | Location: Louisiana | Registered: 28 November 2001Reply With Quote
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I never mix brass...Thats a sloppy practice.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

 
Posts: 42228 | Location: Twin Falls, Idaho | Registered: 04 June 2000Reply With Quote
<.>
posted
Yeah, well shoot me . . .

I mix brass . . . sleazy ol' "range pickups" and ya just don't know where it's been. But this for the revolver, handgun, and shooting conservative loads for plinking. Even the semi-auto, 45 ACP, I don't worry about pressure or much else in a straight wall, handgun case.

That said, I keep track of my .223 Ackley Improved brass for the Rem 700 PSS according to how many times it's been loaded. All the same lot, all matched up brass.

I plink and horse around with the handguns. I shoot surplus ammo in the Garand and the Mausers -- CORROSIVE ammo in the Mausers.

But the Rem. 700 PSS . . . I shoot eggs at 350 meters. No brass mix for that stuff. The brass that's been shot four times is separated from the stuff that's been shot five times -- even though it's all the same lot.

-- anal, but accurate!

 
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<eldeguello>
posted
Yes, it does. For example, I load a lot of 7X57mm Mauser ammo. Winchester cases have more capacity than Remington, and Norma cases have even more. If I use the same powder charge, bullet, and primer combo in these three different brands, there is a significant difference in both muzzle velocity, and, more important, chamber pressures. The smaller capacity cases give more speed and higher pressure. Also, most U.S. GI brass is thicker, and must use lower powder charges, than commercial brass of the same caliber.
 
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quote:
Originally posted by trans-pond:
In your experience does mixing brands of brass have any appreciable effect on the ballistics of a given reload recipe? If so can you quantify?


Many thanks; enjoyed reading and digesting your advice one and all.
I'll go with the concensus and see what improvements I can gain.
Best steer clear of "Matchkings" for present!!

 
Posts: 337 | Location: Devon UK | Registered: 21 March 2002Reply With Quote
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