Rim Thickness

[Rifleman51]

I know a lot of you already do this, but if you don't, sorting your rimfire ammo as to rim thickness can improve your groups.

I like the Hornady guage the best because it comes with a base that goes on the other side of the caliper. The Sinclair doesn't have that.

By sorting as to rim thicknes, your groups will be more consistant. Also, different rifles will have a particular rim thickness that they shoot the best with. You can save that rim thickness for when you want the best groups and leave the others for practice.

The rims that are either way bigger or smaller I put into a baggie to season a freshly cleaned barrel with.

It doesn't take a lot of time to sort the ammo as to the different thicknesses and will improve your groups. Give it a try.

The Wolf and Federal Auto Match vary from 39.5 to 41.5.

John K

[thomae]

Old post, I know, but I thought I'd add some information which may be interesting to those of you considering sorting by rim thickness.

I had about 700 rounds of Eley Sport (Inexpensive, but shot the best in my Savage MKII Heavy Barrel) that I wanted to sort.

I didn’t have a rim thickness gauge, so I decided to make one. Turns out it’s easy (if you have the right tools)

I already have a Hornady bullet comparator, so I have the red thingamagig (I’ll call it a “caliper base” since I don’t know the right word for it.) that attaches to the blade of my calipers.

I have a mini-lathe, so I chucked a piece of used .243 brass in the jaws and faced off both ends so they would be square.
(I immediately labeled it so I don’t get stupid and try to reload it some day.)

Here is a picture of the parts:



I put it into the Hornady caliper base (It fits quite nicely), and tightened the set screw to hold it in.
To measure rim thickness, zero the calipers on the empty .243 brass, than , and drop the .22LR round into the bullet-end of the .243 brass and measure the overall length with the calipers.

Here's what it looks like measuring:


One thing I noticed was that sometimes I needed to take two measurements to get a better idea of the average rim thickness. This is not difficult, I would measure, twist the .22 round about a quarter turn, and then measure again. Some rounds measured consistently regardless of how many times I turned and remeasured. Others varied depending upon where on the rim the caliper was.

Since my calipers measure only to the nearest .0005 inches, I sorted into the following categories:
.0360 - .0365” (about 5.7%: slightly less than 50 rounds)
.0370 - .0375” (about 43% - approximately 300)
.0380 - .0385” (about 36% - approx 250 rounds)
.0390” - greater (about 6.3% - slightly less than 50 rounds)

Note: I know the percentages don’t add up, but it wasn’t exactly 700 rounds…that’s simply the easy round number I used for my calculations.

FWIW: It would have been a closer count between the .037s and the .038s, but I dropped about 30 or 40 of the 038s on the floor
(Note to self: Try not to be a slapstick comedian: check both ends of your boxes and make sure they are closed before you pick them up!)

I have not yet had an opportunity to shoot my sorted ammo, so I have yet to see if the rifle actually prefers one rim thickness, or if the sorting simply improves consistency.

[TOP PREDATOR]

my homemade thickness guage:

http://savageshooters.com/SavageForu...html#msg226124

results vs. weight sorting:

50 yards
http://savageshooters.com/SavageForu...html#msg238005

100 yards (where it REALLY matters)
http://savageshooters.com/SavageForu...html#msg236024

[thomae]

To Top Predator:
Thanks for your post and for the various links. I must give credit where credit is due, and although I had seen similar gauges elsewhere, I recognized your photos, ergo, I think I must have viewed your post a number of months ago. I also believe that you are the one who put the spark into my head about using .243 brass. Thank you for your inspiration.

I find your test results interesting. I went to the range yesterday and shot some "sorted-by-rim-thickness" groups at 50 yards. When I get some time, I will compile and post my results.

All the best,

[TOP PREDATOR]

i had also somewhat recently got 2 bricks of F'uped ammo that wouldn't eject an average of 1 out of 5 wouldn't fire.

me being a pollack weight sorted the ammo and combined them into my old stock. the only way i knew it was the 2 new bricks is that there was a weight lot that was exhausted with the old stuff, and the new stuff replaced it. anyway, i should have shot a box of the new bricks as i contaminated my tried and trued stock.

the only way i was able to weed out the bad stuff was with the rim thickness gauge. apparantly the rims were too thin and the ejector arms couldn't pick up the rim to pull out the shell.

[Rifleman51]

After shooting some more rounds with different rim thicknesses, I did see a very slight advantage, but I'm not sure it's really worth all the work involved.
Maybe if I was a top shooter in a big match, but for the type of shooting I do, I doubt I'll continue to sort with rim thickness.

John K