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WEIGHT VS. RIM THICKNESS - part 1, 50 yards

 
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  #1  
Old 04-23-2010, 09:13 PM
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WEIGHT VS. RIM THICKNESS - part 1, 50 yards

In the never ending pursuit of weeding out fliers, lotting accurate rimfire ammo, and finding ways of "upping" the performance of typically non-match type ammos, two suggestions are usually brought to the forefront: lot ammo according to weight and lot by rim thickness. The idea of weight lotting is that the same measurement of components used to make a round can be lotted by weight, therefore putting "like" rounds together for better consistancy. Since rimfire ammo headspaces on the rim as it rests around the outer chamber, the idea is that the varying thickness of the rim changes the headspacing / overall length, and that "like" rim thicknesses give better performance.

But which one produces the best results?

I set out today to test weighing vs. rim thickness at 50 and 100 yards as conditions were really calm. As I started to shoot at 100 the wind picked up to 10 mph, and started to mess with the groups, so I'll have to do a 100 yard test later (part 2) when the weather will have less effect on the results.

I figured I'd start out at 50 yards using 3 types of ammo I had handy: Federal bulk, CCI Blazer, and Aguila Match Rifle. I had 30 rounds of Wolf MT, but even though I didn't shoot them, I measured them anyway, both weight and rim thickness. The Wolf produced hardly any variance in either catagory, which could be another reason why it's so accurate in so many rifles.

First I weighed out lots of each ammo, to the tenth of a grain. Second, I seperated each ammo into lots by rim thickness, using a homemade rim thickness gauge (Homemade rim thickness gauge). To ensure that the results of the rim thickness measurements were unbiased by similar weights, the rounds that I used to in the thickness lots were 1 round from each weight lot with the same rim thickness, then put together in an lot of 5. The odds of having 2 or more similar weights in the rim thickness lots at 0.

All the ammos produced many weight lots, but fewer lots of rim thickness, which I thought was interesting and convienant if the rim thickness lots shot better than the weight lots (more rounds with less seperation). The rounds seperated by rim thickness had varying weights within them. But will that work?

Federal bulk - 10 major weight lots with 3 lots holding the most amount of rounds. 5 major rim thickness lots with 2 lots holding the most amount of rounds.

CCI Blazer - 8 major weight lots with 2 lots holding the most amount of rounds. 5 major rim thickness lots with 2 lots holding the most rounds.

Aguila Match Rifle - 9 major weight lots with 3 lots holding the most amount of rounds. 6 rim thickness lots with 3 lots holding holding the most amount of rounds.

Wolf MT - (measured but not shot, only 30 rounds on hand) 4 weight lots with 1 lot holding the most rounds. 3 thickness lots with 1 lot holding the most rounds.

The ammo was shot from a Savage MKII BV, bipod and rear bag, 1lb trigger, 16x on the scope. 47 deg., low humidity, sunny, no wind to mention at the time. I shot a baseline group of 5 rounds consisting of 1 round of varying weight and rim thickness to ensure the best weight variance I could to simulate a "out of the box, untouched" result.

The Federal bulk "assorted" weight group produced a 1.75" group. 3 five round groups of same weight lotted ammo were shot and produced tighter groups, a 1.6" average. Still not the best, but it is cheap bulk ammo, and an improvement none the less. 4 five round rim thickness lotted groups were then shot, with an average of a 1.35" group. A better improvement lotting with rim thickness over weight.

The CCI Blazer "assorted" weight group produced a just over an inch group. 3 five round groups of same weight lotted ammo were shot and produced tighter groups of and average of just under an inch. 4 five round rim thickness lotted groups were then shot, with an average of a .71" group. Most of the rounds in these groups were touching each other (clover leafing) and very impressive for an economical ammo.

The Aguila Match Rifle "assorted" weight group produced a little over a .75" group. 3 five round groups of same weight lotted ammo were shot and produced slightly tighter groups averaging .66". 4 five round rim thickness lotted groups were shot, with an equal average of a .66" group. Both 1 weight and 1 rim thickness measured lot produced a 5 round .5" group.

Seems that the rim thickness lots produced the smallest groups after all, and within those groups, the holes seemed to be have more clover leaf than the weighed lots.

A few more trends showed that certain rim thicknesses shot better groups than others (same as weight lotting) and higher / lower points of impact depending on thickness (same as weight lotting). Another trend was the thicker the rim, the higher the point of impact - not by much, but enough to notice. Perhaps more primer filling in more space? I'll have to chrony different thicknesses at a later date, as I didn't anticipate needing it today.

Another thing that struck me as odd is that the Aguila had the most amount of weight and rim thickness lots, yet historically shoots the best for me out of the three ammos fired at 50, 100, and 200 yards. Perhaps it's the standard velocity being more consistant than the high velocity through my rifle?

CONCLUSION - both measuring weight and rim thickness did improve groups from just shooting from the box, and both are viable ways of improving accurracy. As mentioned before, I wanted to shoot the same course of fire at 100 yards, but the wind picked up enough to give inconclusive results at 100. I believe that at 100 yards the advantages of mesuring either weight or rim thickness would be more revealing to which method produces the best results. I'm not abandoning all my weight lots - yet - until I can see the difference at 100 yards, but from what today has shown me (at least at 50 yards), rim thickness lotting seems to have a bit of advantage over weight lotting.
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Old 05-04-2010, 02:24 AM
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Re: WEIGHT VS. RIM THICKNESS - part 1, 50 yards

WOW what an awesome test and very interesting i also shoot a mixed bag of ammo whatever i can get/ price usually Aguila supermax 30 gr American Eagle 40 gr or Remington Viper 36 gr when i finish typing this out i wil mic. out all of the rims to see what sort of improvement i can get by doing that. thanks for taking the time to do that and then post up your results.

I am currently compiling a list of of 22lr and 22Wmr ballistics
muzzle Energy/velocity then at 50 yds and at 100 i also am measuring ballistic coefficient using a sample of ten rounds per box but scince i cant get my hands on all types of ammo im afraid that list wont get completed.

The .22WMR list is done with quite a few of the B.C's measured if anyone is interested let me know and i will post it up i have it in wordpad and for those who want it in Exel format and here is the link for the ballistic coefficient calculator i use Precision Ballistic Coefficient Estimator its at the bottom of the page.
So if anyone wants to make there own measurements and get real B.C. data you can you will need a micrometer to do so, but you can get one for about $25 at an auto parts store. or just take about %30 percent off of the manufacturers B/C data and you will be pretty close from what i have found
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Old 05-06-2010, 04:49 PM
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Re: WEIGHT VS. RIM THICKNESS - part 1, 50 yards

i'm thinking that it would be of great value to the rimfire guys, as bc's are hard to come by in general.

thanks for the bc's
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Old 05-07-2010, 08:56 PM
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Re: WEIGHT VS. RIM THICKNESS - part 1, 50 yards

i have an ammo shipment coming in on the 10th with 2 more brands of 22lr ammo ive never had before so i will post up what i have then.

here is the 22WMR info ive collected

the format is messed up due to the size of the wordpad document
but if you look at the spaces and the header with what the numbers represent you should be able to make it out, or if you want i will email you the wordpad or exel documents and that will be easier to read

{sectional density} Ballistic coefficient
Brand grain tip {SD} MV ME V@100'E @100' MP ft.lbm MPH B.C aerodynamic efficiency
-----------------------------------------------------------------------------------------------
ft.lbf
Win Mag CCI/Speer 30 V-Max .085 2200 -322 -1571- 164- 9.43 1500.0 .090*-.098*
Win Mag CCI/Speer 30 TNT G .085 2050 -280 -1317 -116 -8.79 1397.727
Win Mag CCI/Speer 30 TNT-HP .085 2200 -322 -1405- 131- 9.43 1500.0
Win Mag CCI/Speer 30 JHP .085 2200- 322 -1375 -126 -9.43 1500.0
Win Mag Federal 30 TNT-HP .085 2200- 322 -1419 -134 -9.43 1500.0
Win Mag Hornady 30 V-Max .085 2200 -322 -1002 -67 -9.43 1500.0
Win Mag Winchester 30 JHP .085 2250- 337 - 9.64 1534.90
Win Mag Remington 33 Accuti .094 2000 -144- 1217- 109- 6.60 954.545 .090-.095
Win Mag Winchester 34 JHP .097 2120 -339 -1435 -155 -10.30 1445.454
Win Mag CCI 40 FMJ .114 1875 -312- 1366- 166 -10.71 1278.409
Win Mag CCI 40Jktsprpn .114 1875- 312- 1385 -170 -10.71 1278.409
Win Mag CCI 40 JHP .114 1875 -312 -1319- 155 -10.71 1278.409 .075*-.083*
Win Mag CCI 40PlatedHP .114 1875- 312- 1319- 155- 10.71 1278.409
Win Mag Federal 40 FMJ .114 1880- 314 -1121 -112 -10.74 1281.818 .090*-.095*
Win Mag Fiocchi 40 JHP .114 1910- 158- 1143 -116- 7.63 910.227
Win Mag Fiocchi 40 JSP .114 1910 -158- 1143- 116- 7.63 910.227 .090*-.100*

Win Mag PMC 40 FMJ .114 1910- 158 -1205 -129 -7.63 910.227
Win Mag PMC 40 PSP .114 1910 -158 -1205 -129 -7.63 910.227
Win Mag Remington 40 JHP .114 1910- 158- 1141- 116- 7.63 910.227
Win Mag Remington 40 PSP .114 1910 -158 -1141- 116- 7.63 910.227
Win Mag RWS 40 JHP .114 1410- 177- 1197- 127 -8.06 961.363

Win Mag Winchester 40 FMJ .114 1910 324 -1330- 157 -10.91 1302.272
Win Mag Winchester 40 JHP .114 1910 324 -1326- 156 -10.91 1302.272
Win Mag Winchester 45php .128 1550 240- 1147- 131 -9.96 1056.818 .95*-105*
Win Mag Federal 50 JHP . .142 1530 260- 1197- 159 -10.93 1043.181
Win Mag CCI 52#12Shot .148 effective range 10 ft

i just added hyphens in there to make the chart a little easier to read

if anyone has any ammo thats not on here would you make measurements and post the results using the ballistic coefficient calculator i have posted up earlier thanks

Last edited by Savageman69; 05-19-2010 at 06:04 PM. Reason: corrected velocity for fiocchi pmc and remmington 40gr bullets
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Old 05-14-2010, 04:23 AM
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Re: WEIGHT VS. RIM THICKNESS - part 1, 50 yards

I know i said i would post the .22lr ballistics table up but its 5 pages long so cant do that if you would like what i have feel free to e-mail me and i will send you what i have.

I check my e-mail every day or two so i will get whoever requests the chart to them within a week i know this stuff is important specially when buying ammo that you may not have used before so i will send it out as soon as i can,
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