Case Weight - When Does It Matter?

[Phil3]

I am loading new unfired Winchester brass in an AR-15 chambered in 223 Remington to fired at 100 yards. I want as small a groups as possible, and would like to know to what extent weighing and sorting cases matters in this application. Of the 91 total cases:

Grains
92.1 - 93.0 5.5%
93.1 - 94.0 26.4%
94.1 - 95.0 45.0%
95.1 - 96.0 18.7%
96.1 - 97.0 4.4%
Total 100.0%

The cases were weighed after trimming to 1.750", case neck chamfered and deburred, primer pocket reamed and flash hole deburred. Scale was RCBS1500 ChargeMaster.

I will be using Lapua cases in a Howa bolt action at 100 yards as well. Do I need to weigh these and sort? What should be done with brass that is at far extreme of weights...for both Winchester and Lapua brass?

Phil

 

[Bob3700]

I don't know that I would spend the time to weigh the cases that you are going to shoot in an AR15. The wild ride that the loaded round takes from mag to chamber coupled with the relatively generous chamber tolerances sort of place a lid on ultimate accuracy.

I would only worry about weighing cases if my shooting exceeded 300 yds.

Bob

 

[Phil3]

When building the AR-15, I asked Krieger (the barrel maker) to chamber it with the most accurate chamber possible. According to them the chamber is a minimum spec SAAMI 223 Remington chamber.

My range distance is pretty much limited to 100 yards, and suspect as well, that the case weight may be immaterial, but wanted other's opinions.

Phil

 

[nosualc]

Cull out the 10% at bottom/top and shoot them separately from the other 90%.

Then tell us, can you tell the difference?

Betcha can't. Not in an AR, not at 100 yds.

-nosualc

 

[savagedasher]

Everybody loads and preps different, I feel you got the cart in front of the horse, till the brass has Ben fired and sized the case isn't uniform, then you can prep it properly. Water grains of capacity means more to me then total weight. Good Shooting Larry

 

[Phil3]

I trimmed the cases before firing because they varied significantly in length. By .009" from one extreme to the other. I also wanted to weight the cases, AFTER any brass was removed. The trimming required chamfering and deburring at the case neck. The primer pocket and flash hole work are one time events and can be done with new brass.

I don't think I will much bother with the capacity as there seems to be an opinion for my purposes, it will not matter much. Also, this seems to be a very time consuming and tedious effort. ??

Phil

 

[savagedasher]

The reason I do it after then the case is fully stretched.

 

[bheadboy]

for bolt rifles, i fully fire/prep brass then weigh, including neck turn first -my rule i have followed has been +/- 1 grain from median for each 100+/- gr of weight

thus for yours if it were a bolt, +1/-1 gr from the medium of 95gr.

for the ar forget it.

Bob

 

[langenc]

The reason I do it after then the case is fully stretched.

So how much weight change is there after firing a case once? Twice? Three times?? This question assumes there will be no more trimming between shooting the cases.

 

[CZ550]

I know I am gonna get burnt at the stake for this but in my experience competing and testing loads for 600 IBS.

This would be a complete waste of your time from an accuracy standpoint.

Will it help your confidence that it may.

 

[Phil3]

Well, no burning at the stake from me. If does not matter, I save some labor that can be spent on something that does matter. Thanks for the input.

Phil

 

[ronemus]

I did an experiment several years ago to determine just how much effect brass weight has on .223 loads. I used WW brass (sized, trimmed and deburred, primer pockets uniformed, flash holes deburred, and neck turned) , WSR primers, charges of RL-15 or N-550 powder weighed to 0.1 gr, and 75 gr A-Max bullets. Using the lightest and heaviest cases (sorted from 1000 once-fired I had on hand), I had two lots of 10 cases with a 3 gr difference in weight. The average muzzle velocity difference was 16 fps, just a bit more than the 12 fps due to 0.1 gr of powder. I choose to sort 0.5 gr lots of brass for my long range loads, but the effect will only matter at 800-1000 yards - the vertical displacement on the target from such a small velocity change is negligible at shorter distances. Unless you control all other sources of variation, the effect of brass weight is negligible.

 

[searcher]

I'm a brass prep fanatic and I shoot f-class, point blank benchest and try to eke every bit of accuracy out of all of my guns just to see how far I can go. I am a big believer in weighing cases - but not in an A/R. I have several heavy Krieger, Hart and Shillen barrels on A/R's and a few of them shoot much better than a few bolt rifles I have - consistently in the 2's in no-wind conditions. I have found that no appreciable (even noticeable) difference was found by weighing the A/R cases. Nor did I get appreciably better aggregates using Lapua brass over new, unfired Lake City brass. What I did get noteworthy improvement from was a VERY LIGHT (45% surface contact) turning of the necks, using heavy tension from a smaller neck bushing and utilizing NO crimp(don't use moly bullets with this technique). I use a Redding "s"-type bushing full-length sizer. I shoot the A/R's at targets and varmints under very controlled shooting from a steady bench. When shooting Across The Course, my position shooting (along with most people) is not concise enough to have made the accuracy improvement meaningful. I'd probably focus more on loaded round concentricity, bullet weight, powder work-up, etc. As for the bolt gun, I'd stick to Lapua brass for the better quality and extended reloadability and neck-size only.