WEIGHING VS. RIM THICKNESS - part 1, 50 yards

22 Long Rifle ammo is finicky. Tell us all about it here.
TOP PREDATOR
A Poster
A Poster
Posts: 231
Joined: Sun Jun 28, 2009 5:05 pm
Location: N.E. PENNSYLVANIA
Contact:

WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by TOP PREDATOR »

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 ( viewtopic.php?f=4&t=4204%20Homemade%20r ... ss%20gauge ). 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.
"a craftsman can't realize his full potential, without finding the potential of the tools he uses...."
Hawk-1
A Poster
A Poster
Posts: 207
Joined: Mon Feb 01, 2010 6:49 pm
Location: North Carolina

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Hawk-1 »

quite interesting! I do believe you will see major differences at 100, compared to 50.
User avatar
AZRifle
A Poster
A Poster
Posts: 159
Joined: Tue Dec 08, 2009 5:01 am
Location: Arizona
Contact:

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by AZRifle »

Not to throw a monkey wrench into all of this but...

If the bolt closes at a certain depth every time and, the bottom of the case is held flush against it's face every time, isn't the vairable the overall length of the cartridge?

Jerry
Rifle Silhouette Information - http://www.RifleSilhouette.com
Arizona Land Surveying - http://www.AZLandSurveying.com
steve b.
A Poster
A Poster
Posts: 216
Joined: Fri Dec 21, 2007 4:15 pm

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by steve b. »

Exactly. The consistency of the location of the driving band in relation to the leade angle of the chamber. The actual thickness of the rim has almost nothing to do with it. You would have to measure if the rim thickness difference is making the OAL longer out the bottom (rim sitcking out further) or is it thicker towards the bullet (resulting is no gain), or is it actually the case is shorter, bunching up at the rim, making the OAL shorter?

That's why so many tests by shootes are producing different results. There is also the question of how precise testing equipment is and conditions.

Edit: "If ..... the bottom of the case is held flush against it's face every time."

Actually, this is not a constant. If you have a large chamber in your rifle, such as sporting type, there is a potential that the driving band will not engage the leade angle before the bolt closes, resulting in some play with loaded round, even with the bolt closed. This is commonly found on Ruger 10/22 factory barrels. This play was one of the reasons shooters began reworking their bolts on the 10/22 to reduce the massive amount of excessive headspace. On target grade bolt action rifles, this is fairly uncommon.

s.
Last edited by steve b. on Fri Apr 30, 2010 1:48 pm, edited 2 times in total.
Jerry G
Uber Master Poster
Uber Master Poster
Posts: 2746
Joined: Wed Apr 12, 2006 2:34 pm
Location: Casa Grande, AZ

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Jerry G »

Boy, that realy cleared it up for me. I'm going to stick with the better target ammo. :shock:
User avatar
Bob259
Uber Master Poster
Uber Master Poster
Posts: 4337
Joined: Sat Jul 15, 2006 7:16 pm
Location: Phoenix, AZ

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Bob259 »

Jerry G wrote:Boy, that realy cleared it up for me. I'm going to stick with the better target ammo. :shock:
Jerry... Steve's got enough information on this he could write a book on it.... :| Oh wait a minute he did :D
F Troop - Southwest Outpost

Proud Member of the Ram Slammers US Division (Two Bob)
User avatar
Jason
Uber Master Poster
Uber Master Poster
Posts: 3002
Joined: Tue Feb 28, 2006 7:36 pm
Location: Snohomish, WA

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Jason »

I was waiting for someone to bring up the fact that Steve wrote a whole book about this subject... =))
steve b.
A Poster
A Poster
Posts: 216
Joined: Fri Dec 21, 2007 4:15 pm

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by steve b. »

Ha...! I got busted.

I tell ya, I really want to update that book to reflects some changes in opinions that I've had since the release, and more so to correct all the errors my publisher left in it (I never saw a draft copy before print), but the two of us just can't seem to get along. So, I'm working on a new rimfire book that I will self-publish.

Anyhow, you got me!

Now, who is gonna notice the Silhouette article I have in the May Precision Shooting Magazine, dealing with practice ammunition vs. competition ammunition? I told the editor to expect to see more Silhouette stuff from me, and he commented that it was a fine thing to add to the magazine. Besides, how many articles do we need on loading 6ppc or how to neck turn brass?

s.
User avatar
Bob259
Uber Master Poster
Uber Master Poster
Posts: 4337
Joined: Sat Jul 15, 2006 7:16 pm
Location: Phoenix, AZ

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Bob259 »

steve b. wrote:Ha...! Now, who is gonna notice the Silhouette article I have in the May Precision Shooting Magazine, dealing with practice ammunition vs. competition ammunition? ..... s.
I will :) Can't wait.
F Troop - Southwest Outpost

Proud Member of the Ram Slammers US Division (Two Bob)
User avatar
jneihouse
Distinguished Master Poster
Distinguished Master Poster
Posts: 2144
Joined: Fri Nov 18, 2005 11:31 am
Location: Fort Smith Arkansas

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by jneihouse »

Has it got pictures??? I like pictures....words are confusing....confused Kitty is a bad thing....kidding aside, the mags a good read....would urge everyone who has not yet to subscribe....you don't find any of that "This rifle turned in several great 2" groups at 50 yds and is the next best thing since sliced bread" followed by a full page ad for the same rifle....and after several conversations with Steve I can assure you he's a quick study...his translation of the special aspect of our sport will be interesting to follow....And besides, he's a member of TK....enhances his credibility in the silhouette circles more than any number of books written...Many are called but few are chosen.. :D

Kitty
Commander in Chief, F Troop
steve b.
A Poster
A Poster
Posts: 216
Joined: Fri Dec 21, 2007 4:15 pm

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by steve b. »

Thanks for the kinds words everyone, I do appreciate it.

I'm rather smitten with this sport; there is something very special about the challenge it brings to each shooter at all the levels, and I was really impressed by how friendly and giving everyone has been at events. I have competed in a number of different shooting disciplines, and this by far has the best group of people that I've encountered. I'm proud to be a part of it. Mark, John, Bill, Tony, and many others have been very generous in helping my shooting improve and getting me on the right path. Thanks to all!

I still remember how much fun it was at Raton last year, and how darn good Motl's cookin was! I can't wait to get to Winns and then Ridgeway. Looking forward to it alot.

As for TP's original post, many of us have all been involved in testing, and the efforts he put forth are appreciated. It's one thing to guess as results, it's another to test, collect data, and then report. It takes time and effort, and that's the best way to learn new things and share ideas.

One thing I would change about the sport: If I can make a turkey spin 180 degrees and not have it fall off, it darn well should be worth 2 points and not a miss!

s.
User avatar
ShooterP14
AA Poster
AA Poster
Posts: 257
Joined: Tue May 23, 2006 5:50 pm
Location: Orlando, Fl
Contact:

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by ShooterP14 »

steve b. wrote:
One thing I would change about the sport: If I can make a turkey spin 180 degrees and not have it fall off, it darn well should be worth 2 points and not a miss!

s.
IMHO I think that turned targets #-o ~x( should be counted for ties (I.e. 0.1 point). :ymsmug: Well, it was just a thought...
The Wonderful White Winged Warrior - He's Everywhere! He's Everywhere!
User avatar
AZRifle
A Poster
A Poster
Posts: 159
Joined: Tue Dec 08, 2009 5:01 am
Location: Arizona
Contact:

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by AZRifle »

You guys are opening the door for paint chip analyzation, target setting standards and instant replay film at a match. haha!

Jerry
Rifle Silhouette Information - http://www.RifleSilhouette.com
Arizona Land Surveying - http://www.AZLandSurveying.com
Jerry G
Uber Master Poster
Uber Master Poster
Posts: 2746
Joined: Wed Apr 12, 2006 2:34 pm
Location: Casa Grande, AZ

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Jerry G »

Bob, I wasn't arguing with Steve. What I saw from his data was there are many variables in rimfire accurcy that we have no control over. I still think the answer to the ammo problem we all have is to buy the good stuff and have fun shooting. I also realize there are some out there that like to expermint with equipment and have a lot of fun doing that. I do enjoy a little of that myself. Sometimes the journey can be as much fun as the conclusion. In the case of making cheep ammo shoot real well, I do think that one has been beat to death, but I could be wrong.
Travelor
A Poster
A Poster
Posts: 239
Joined: Wed Apr 26, 2006 6:25 am
Location: Central Arkansas

Re: WEIGHING VS. RIM THICKNESS - part 1, 50 yards

Post by Travelor »

Actually I think that measuring the rim thickness is a way to determine the variation in amount of priming compound inside the fold of the case, not the length of the cartridge to the driving band.
George

No one cares how much you know until they know how much you care.
Post Reply