Another 22LR Rim Thickness Discussion

[wkdickinson]

While reading a current thread about 22LR accuracy, I got interested again in measuring rim thickness. I have read that most people do not sort high-end target 22LR ammo because it is so consistent. I decided I wanted to see if that was the case.

Last fall I did some brand and then lot testing with my Anschutz Match 54 Super Match (1413) and found “a lot” of Lapua Center X that it liked really well. Fortunately, I was able to buy 2 bricks of it before the supply dried up. So, I pulled a box from each brick and measured the rim thickness using a gauge I made from a 223 Rem case, mounted in an aluminum base with a slot to attach it to the jaw of my Mitutoyo digital calipers.

After doing those I also found a new box of Eley TENEX and measured all of those. Then just for comparison did 2 boxes of RWS “Rifle Match” (they are about $5/box, compared to $10-$12 for the Lapua and Eley).

Like I expected, the expensive stuff is very consistent, while the mid-price is much less so (see the charts below). But what really surprised me was the disparity of the average rim thickness by brand.

Minitab statistical "graphic summaries" of the data:







Some observations:

• So in this small study there is almost a 3.5 thousandths difference between the average rim thickness of the Lapua CX and the Eley 10X. Both are truly "top-shelf" ammo, that shoot amazingly well. So is rim thickness really an accuracy criteria? Variation of rim thickness may be, but what brand your rifle likes may more likely be, the mean rim thickness.
• The ES of the rim thickness for both the Eley and the Lapua are reasonable close numerically, but if you look at the distribution curves, they are quite different.

I'm not sure I have learned much from this, other than the expensive ammo is definitely more consistent and it is probably is not worth the effort to sort by rim thickness.

 

[butchlambert]

I'm not 100% sure, but I doubt the serious shooters check rim thickness at this time.

 

[dellet]

While most don't sort for rim thickness because the time spent vs just buying better ammo make it tough to justify, engraving depth of the bullet into the lands can/does matter more than rim thickness.

You can't sort engraving depth without checking or sorting rim thickness first.

When shooting mixed lots or ammo that otherwise would be rejected it can help.

 

[butchlambert]

While most don't sort for rim thickness because the time spent vs just buying better ammo make it tough to justify, engraving depth of the bullet into the lands can/does matter more than rim thickness.

You can't sort engraving depth without checking or sorting rim thickness first.

When shooting mixed lots or ammo that otherwise would be rejected it can help.

Have you been around this game long?

 

[dellet]

Have you been around this game long?

Long enough that I don't sort 22LR, I buy what shoots best.

Too long, in that I till enjoy shooting rifles chambered in 22 short and will spend time sorting ammo because choice is very limited and it makes a measurable difference on target.

 

[butchlambert]

That's great!

 

[JMayo]

I shoot ara with some really great shooters.
Testing lots then buying what shoots best.
None of the measuring, weighing spinning or gifts to the gods is done.

I'm not talking about the good ole boy shoot.
Im talking hitting the dot at 50 yds consistently .. ie 2450-2500 ara.

 

[boltman13]

Because most of my 22LR shooting is off the bench at 100 yds. for score in at least some wind I do not sort by weight or rim thickness on premium amo, such as Eley, Lapua and RWS. If I ever get good enough at reading the wind for it to matter I may, but I doubt I live long enough. I know one fellow shooter who used to weight sort for IBS BR-50 matches but decided it wasn't improving his scores so he quit. He was finding no more than +/- 0.1 grain variance from the most common weight with RWS R50.

 

[wkdickinson]

Because most of my 22LR shooting is off the bench at 100 yds. for score in at least some wind I do not sort by weight or rim thickness on premium amo, such as Eley, Lapua and RWS. If I ever get good enough at reading the wind for it to matter I may, but I doubt I live long enough. I know one fellow shooter who used to weight sort for IBS BR-50 matches but decided it wasn't improving his scores so he quit. He was finding no more than +/- 0.1 grain variance from the most common weight with RWS R50.

In my limited experience I pretty much agree. However, I am still truly surprised at the difference in rim thickness by brand. But moving forward I am going to, buy good ammo and shot it.