WEIGHT VS. RIM THICKNESS - part 2, 100 yards

[TOP PREDATOR]

I started off at 50 yards, see: viewtopic.php?f=4&t=4318 (PART 1 50 YARDS) Unfortuanately we've been plagued with enough wind that would not do a 100 yard test justice, and today was the first chance I had to hit the range in a calmer setting.

Just as in the 50 yard test, three different ammos were shot from a Savage MKII BV 20" heavy barrel, bipod and rear bag, 1 lb trigger, 18x on the scope. 65 deg., high humidity (80%), cloudy to partly sunny, 3-5 mph but managable wind (may have opened up groups slightly).

I seperated the ammo like in the 50 yard test - several different 5 round same weight lots, several 5 round rim thickness lots (making sure that every round weighed differently to ensure results were based on rim thickness, not weight). This time I brought the chronograph to measure what is any differences / simularities there were between the diffeerent weight and rim thickness lots of the three different ammos, placed 5 feet from muzzle. Groups were measured on the outside edges of the group.

Group #1 excluded obvious flyers (main body of the group), group #2 included obvious flyers (ranging .25" to 1.25" away from the main group). Anything further away I considered a pulled shot and took another round to replace it. Any shot that I knew I pulled was refired also.

AGUILA MATCH RIFLE

(weight sort):

Weight - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

50.6 gr --- 1001 --- 42 ---- 2.5" ----- 3" ------- 1
50.8 gr --- 1010 --- 20 ----- 1" ------ 1" ------- 0
51.0 gr --- 1017 --- 7 ----- 1.5" ----- 2" ------- 1

(rim thickness sort)

Rim t. - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

.0355 ---- 1008 --- 25 ---- 1.5" ---- 2.25" ----- 1
.0360 ---- 1010 --- 14 ---- 1" ----- -2.75" ------ 2
.0365 ---- 1020 --- 13 ---- 1.75" --- 2.5" ------ 2
.0370 ---- 1011 --- 31 ---- 1.25" --- 2.25" ----- 1
.0375 ---- 1014 --- 30 ---- 1.5" --- -2.25" ----- 1

FEDERAL BULK PACK

(weight sort)

Weight - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

49.1 gr --- 1143 ---- 61 ----- 2" ----- 3.25" ---- 1
49.2 gr --- 1163 ---- 49 ----- 2" ------- 3" ------ 2
49.3 gr --- 1165 ---- 57 ----- +2" ----- 2.5" ---- 1
49.4 gr --- 1199 ---- 42 ----- too large to mention / measure accurately

(rim thickness sort)

Rim t. - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

.0350 ----- 1193 --- 56 --- 3.25" --- 3.25" ---- 0
.0355 ----- 1157 --- 68 ---- 1.5" ---- 3.5" ----- 2
.0360 ----- 1177 --- 40 ----- 2" ----- 3.5" ----- 2
.0370 ----- 1175 --- 51 --- 3.25" ---- 3.5" ---- 0

CCI BLAZER

(weight sort)

Weight - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

50.5 gr --- 1230 ---- 50 ---- 1.25" --- 2" ----- 2
50.7 gr --- 1237 ---- 35 ----- 1.5" -- 1.75" --- 1
50.9 gr --- 1238 ---- 38 ----- +2" --- 3.25" --- 1
51.2 gr --- 1246 ---- 19 ----- 1.5" -- 1.5" ---- 0

(rim thickness sort)

Rim t. - avg. fps - dev. - grp. 1 - grp. 2 - # flyers

.0380 ----- 1239 --- 12 --- +1.25" --- 2" ------ 1
.0385 ----- 1233 --- 30 ----- 2" ---- 2.25" ---- 1
.0390 ----- 1243 --- 35 ----- 1" ---- +1" ------ 0
.0395 ----- 1238 --- 22 ---- 1.5" --- 2.25" ---- 1

The one trend I did notice with all three ammos (in general) is that with the weight sort the FPS increased and deviation between the highest and lowest FPS decreased as the lots used heavier ammo. No such trend was evident with the rim thickness sort.

Both weight sorting and rim thickness sorting improved on the baseline groups shot by .25" to 1" - the baseline groups were 5 shots each of different weights and rim thicknesses to guage what or if any improvement was made. I also felt this simulated an absolute randomly picked "out of the box" 5 shot group.

CONCLUSIONS:

weight sorting -

1. Tighter groups, however flyers were further away from the main group.
2. The heavier the weight the higher the FPS.
3. The heavier the weight the lower the deviation.
4. More predictable the group and velocity.


rim thickness -

1. Larger groups, most flyers were not so far away from the main group.
2. No real trend or correlation between rim thickness and change in FPS or deviation.

Weight sorting produces more "lots" than rim thickness, perhaps telling me that it singles out more differences than rim thickness sorting. Although neither completely weeded out flyers, both did work to reduce them drastically and shrunk group size. Most of what I call "flyers" were only .25" away from the main group. If you feel that a .25" or even a .5" impact away from the main body of the group isn't really a flyer, you can make adjustments to the above measurements and eliminating many "flyers".

Both weight and rim thickness sorting produced a "magic lot" or two in all three ammos that the rifle really liked and produced a better group than the other lots. By looking at the group's size and shape, it appears that the rim thickness sorting was less "finicky" when switching from one lot to another, perhaps due to the larger group size as compared to weight sorting at 100 yards.

Strangely enough, the group results of 100 yards almost completely contridicts the 50 yard results. At 50 yards rim thickness seemed to have and advantage, while at 100 yards weight sorting performed better. The only thing i could ASSUME is that at longer distances, whatever it is about weight sorting superceeds rim thickness sorting and takes priority at those longer distances. If I didn't shoot it myself, I probably wouldn't believe it either. Yet another rimfire mystery.

For me, it appears that at shorter distances, rim thickness wins for group size, and for longer distances weight sorting. Of course different ammos, rifles, etc. may have different results. However, the use of the chronograph revealed the better consistancy of the weight sorting over the rim thickness sorting and the groups at 100 yards backed it up on average. This consistancy with the weight sorting in the end equates to accuraccy, at least at further distances, and isn't that what it's all about?

[Jerry G]

That is some interesting data. I guess the final question that remains is....... what happens if you sort by rim thickness then re-sort thoes by weight.

By the time you go thru all this you will spend more on ammo than if you just bought the good stuff.

[TOP PREDATOR]

yeah i did a few lots both weight and rimthickness, takes way too much time, might as well buy the good stuff at that point.

i just got 2000 rounds, once you get your parameters straight (lowest to highest lots takes about 15 min.) weight sorting 500 rounds take 1.5 hours with a digital scale.

[Jerry G]

Thanks for the info. I'm still not sure what a person does with the ammo that doesn't make the grade when you sort it, when you have one pile that shoots 1.5 and another pile that shoots 3 inches.

[Dee]

Thanks for the info. I'm still not sure what a person does with the ammo that doesn't make the grade when you sort it, when you have one pile that shoots 1.5 and another pile that shoots 3 inches.

You sell it to people shooting 50' indoors Or shot cans with it. I sat down the other night to weight sort some SK after about 20 I put them back in the box and decided to just take my chances. No doubt you could find some bad ones to exclude but I don't have the patience some of you do. Thanks for sharing your data TP it is always interesting to read.

Dee

[TOP PREDATOR]

thanks, dee

usually i'll use the ones that are not up to snuff as foulers, or shorter range shooting, or for chickens. the better grouping lots are used for the further out steel or shooting paper at 100 and 200 yards.

[Travelor]

Our Club has started a Thursday 100 yard RF match for us Old Farts. I have been having unexplained low hits so I started weighing my ammo (Eley Pistol Extra of a proven good lot) and this helped but I am still getting unexplained lows, just not as many. Ammo is really really consistent in weight and out of 100, I only get 2-3 that are either +.2 or minus .2 grains. These by the way shoot just as good as the weight sorted ammo.

I am shooting a two Anschutz rifles, one is a 1712 stocked by Evelio with factory barrel and the other is a 54:18 Running Board rifle in factory stock. Both guns are capable of grouping at or under 1" routinely with this unsorted ammo.

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George