Anyone here gauging .22 LR rim thickness?

[Patrick L]

I see a few ads for rim thickness gauges, with claims that sorting your ammo by rim thickness can improve groups.

Is anyone here actually doing this, and do you see any truth to the claims? I was thinking about giving it a try. I was also wondering if this is something that only applies to the high end precision stuff. My .22s are more middle of the road, certainly not junk but not Walther or Anchutz level stuff.

[Bent Ramrod]

I tried it for a while. Mine is one of those things that you attach to your dial caliper. Sorted a 500-round carton of that Russian “Junior” ammo made at the Klimovsk Stamping Plant. Made no difference that I could see. Same flyers around a core group, no matter what the rim thickness.

It might make a difference with higher grade ammo, but there are obviously other things going on that influence .22 RF accuracy.

[Petrol & Powder]

As for actually gauging rims, I do not currently do it. I have talked to shooters that sort cartridges and I've used the gauges (not my own).

Here's the bottom line - Back when you could buy a Neil Jones rim thickness gauge for about $30, you could use it to sort through cheaper bulk ammunition and eliminate some of the inconsistent rounds. It was cheaper than buying cases of Eley Tenex or Match.
The idea was that you could get enough consistency out of cheap ammunition that you could be competitive with the guys shooting the expensive ammunition without having to purchase the expensive ammo.

Most people eventually come to the conclusion that you're better off just finding the ammunition your gun likes and then buying as much of that particular ammunition that you can get your hands on. Sometimes even buying a particular lot number of that ammunition. If you ended up buying some high quality match ammo like Eley or the old Federal Gold Metal Ultra Match, the cartridges are extremely consistent and there's nothing to be gained by gauging each one.

So, the claims that sorting cartridges by rim thickness will improve your groups are true BUT the amount of improvement will be greater when sorting lower quality ammunition. If all of the cartridges are consistent to start with, there's little to be gained.

[Outpost75]

I always got better results by measuring bullet diameter and choosing the batches having fatter bullets.

[Eddie2002]

I've heard of weighing the rounds and sorting them that way. It is supposed to help with the lower cost bulk ammo. Measuring the bullet diameter would seem to make sense also.

[NSB]

I shot rimfire silhouette for many years. I did very, very well at it. I set several records that were never beaten for aggregate scores, individual scores, and shoot-off scores. I'm not telling you this to brag, I'm leading up to a point. Here it is: sorting rim thickness is a total waste of time. You might be able to gain some infinitesimal amount of group reduction if you were shooting a bench rest rifle with premium ammo, but even that's not guaranteed. I played around with sorting by weight, rim thickness, and bullet diameter. I sorted thousands of rounds and tested for accuracy. In the end it was a total waste of time. What isn't a waste of time is getting a large variety of premium ammo and spending time at the bench shooting groups. Here's an interesting find. I shot my all time best scores using Eley Std. Velocity.....the cheap Eley stuff. It had the greatest variation in weight of all the ammo I tested except the milk carton stuff (wax adds a lot of weight). I used Eley Std. Velocity at the Region 1 shoot and fired a couple of 60x60 scores and also shot 9x10 shoot-off chickens at 100 yards that were NRA rifle chickens, not IHMSA silhouette chickens. Those things were tiny, around a total of 1moa of target! I missed the first one and then ran nine in a row. I didn't sort any of that ammo. It simply shot great out of several guns I owned. Out of two of my guns is shot under .4" at fifty yards. Do yourself a favor and find the ammo your gun likes, not what measures the best. There's just too much variation in ammo, barrels, etc to sort out anything other than the end result....group size and repeatability. Now, if you're bored and there's nothing on TV, kill some time and measure ammo. It won't hurt anything, it just doesn't help.
Here's an interesting note: I shot the NRA shoot-off chickens using a stock Browning Buckmark 10" silhouette gun. It out shot my Anschutz Exemplar that day.

[Petrol & Powder]

NSB, that's sort of what I was trying to state but you said it better.

I knew a gentleman that was an outstanding marksman. He was one of those rare men that was honest, pragmatic and skilled. He told me the same thing that you stated and it's always proven to be true - Find what your .22 rimfire likes and feed that to it. I learned that about 30 years ago and it has held true. When it comes to .22 rimfire, Nothing will reduce group size more significantly than finding the load your gun likes.

Another guy I shot with did sort ammo by rim thickness and it did result in smaller groups when applied to cheap bulk ammo BUT it did NOT result in overall better groups when compared to finding what brand/type ammo the gun liked. He was cheap and I think that worked well enough for him. The gauge was a one time expense for him (he was an electrical engineer and seemed to place value on measuring devices but not much on supplies). I had far better results testing multiple types of ammo and recording group sizes.

I totally agree that when it comes to .22 rimfire guns, finding what your gun likes yields the best bang for your buck in terms of accuracy.

[NSB]

Petrol & Powder, you said it pretty good and I totally understood what you were saying. I just "jumped on the pile" to emphasize what you said. It was pretty obvious to me that you knew what you were talking about. I just hate to see people buying things to make improvements that are going to be pretty much a waste of their time. I guess in the end though, it's still up to them to prove it to themselves. Maybe with more of us sharing our experience on this subject the OP will spend the money on trial ammo instead of a gauge, to find out what shoots best in his gun.

[KCSO]

I Built a gauge and tried it out. The results were about 1/2" better groups at 100 yards on average with several different brands of ammo in a heavy barrel target rifle. In a custom Ruger 10-22 we got groups down to 3/4 inch or a little less with Federal ammo gauged. You need to figure how much that 1/2" will mean to you.

[Patrick L]

I might try it, but won't expect miracles. It sounds like it might help just a bit in my particular circumstances.

I shoot a Ruger American Rimfire. It's best efforts are right about 1/2 " at 50 yards. But I can't guarantee it will do that (or I will, for that matter.) I have LOTS of bulk ammo from when the drought ended. Not garbage cheap, but certainly not Tenex. I'm talking Blazers, MiniMags, etc. Stuff that can shoot decently, but just not as consistently as I would like.

Thanks for all of the great insights!

[country gent]

Not sure if I would "gage" for rim thickness or for squareness. I have always tested ammo and bought large lots of what worked. One of the best "cheap" 22 rounds I found was in the late 80s or early 90s at the cmp/dcm they had cmp white box 22 rimfire surplus for $80.00 a case (10 500rd bricks) this shot very well in all my rifles went back and bought 8 cases. Figured out to $8.00 a brick. THey also had fed match for $90.00 case.

[arcticap]

I've used a rim thickness gauge as part of a method that involves more than simply measuring rim thickness although rim thickness is one part of the equation.

I used it to determine the depth that the bullet [or the bullet ogive] would seat into the chamber of the gun.
First I would measure the rim thickness, then 2nd measure the overall length of the round, then 3rd subtract the rim thickness from its overall length to obtain
the bullet's chamber seating depth for that round.

Then I would sort the rounds into marked compartments of storage boxes that were labeled by position so "exact" length rounds would be together.

Lastly, I would have 3 plastic boxes of the rounds sorted according to their rim thickness, actually by the thickest part of the rim since not every rim is concentric or of the same thickness.

I found that chambering depth was an important factor which can't be determined without knowing the rim thickness.
I also found that rims of the same thickness that were concentric were the best rounds of the lot, usually these had the thinnest rims for that brand's lot.
The rims that had a 1 point variation on my dial in rim thickness and concentricity were the next best rounds of the lot.
The rims that had a 2 or more point variation in rim thickness were the least reliable rounds for accuracy.

While rim thickness played a role, it was not as important as the chamber seating depth of each round.
For some reason, the rims that were 2 points thicker than the smallest rims just didn't seem to have as much reliable accuracy.

I measured many bricks and cases of ammo, and still have some sorted from years ago.
My imported target pistol was very finicky but some cheap SV rounds could obtain accuracy similar to boxes of ammo costing much more.
However, only about 25% - 35% of the cheap rounds were worth shooting in a match.
The rest would need to be experimented with in another gun or to be used as plinking or practice rounds.

I eventually begin buying better ammo and stopped using the rim thickness gauge.
But I would still use some of the measured rounds in Bullseye matches for rapid & timed fire, and the more expensive ammo for slow fire only.

I also measured rounds for years when my son was shooting in junior small bore competition.
Just remember it's about chambering depth as well as rim thickness.
And that the chambering depth for each brand of ammo is based on the ogive for that particular bullet, just like in centerfire.

What I did not do was weigh each round because at the time I did not have an electronic scale.
But I did have a very high quality electronic caliper.

Overall length minus rim thickness equals chamber seating depth for the ogive of the bullet.
Then perform bench testing of various length bullets and don't forget to sort by how thick the rims are too.
Sort into 3 boxes for every batch of cheap ammo labeled A, B and C by grade based on similar rim thickness and then sorted by chamber seating depth.
One would be surprised by how much the ammo spec's vary within the same brick or case of some cheap ammo's.
I've measured more expensive ammo's too for my son't target rifle since it was also finicky and being used in competition.
It's like culling bullets by picking out the most uniform according to seating depth inside the chamber just like with centerfire.
It's not perfect but it's a way to utilize a rim thickness gauge to a fuller capacity.
I came up with this method myself and in the past have also explained how to do it on RFC.



At one time the compartments in this box were all full from sorting a case of ammo.
Top left are the shortest rounds and bottom right are the longest rounds.

[Petrol & Powder]

Along this same line, I purchased a die from Neil Waltz to flat point round nose .22 Standard velocity cartridges. Although some users report improved accuracy from rounds passed through that die, I purchased it simply to flat point bullets for pest control. The die will also make a hollow point but don't use that function. The workmanship and quality is top notch.

The best performing round in one of my rifles is not available in a flat point, so I decided to make flat pointed bullets. The jury is still out on improved accuracy but it is at least as good as it was before - so nothing lost. It may actually produce better group but I just have not had the time to really play with it.

The CCI Small Game Bullet has always been an excellent performer but that round doesn't make the smallest groups in my best .22 rifle.

[Patrick L]

Articap,

Please elaborate. Why does consistent chamber seating depth matter? Does it have to do with the distance the bullet travels till it hits the throat?

I'm not questioning your belief that depth is important, I'm just trying to learn everything I can, so I want to know why.

[KCSO]

Yep that's the gauge I built!

[NSB]

Articap,

Please elaborate. Why does consistent chamber seating depth matter? Does it have to do with the distance the bullet travels till it hits the throat?

I'm not questioning your belief that depth is important, I'm just trying to learn everything I can, so I want to know why.

Very good/expensive rimfire firearms, especially rifles, have what is known as a Bentz chamber. Some call it a Match Chamber, but that's not technically correct. A Bentz chamber will allow your preferred brand of ammo to sit in the chamber to where the nose/ogive of the bullet is in actual contact with the rifling. This keeps the bullet perfectly aligned each time and aids in accuracy. The only downside is that if you don't fire the round it usually won't allow you to eject it. You usually have to keep a tool around to "pick" it out of the action/chamber. Most of the time the RO will allow you to shoot it out. I've owned a few guns with these chambers and they did shoot better. Not just because of the Bentz feature, but because the entire barrel was made to exacting specifications. Some barrel makers will ask you to submit a round of your ammo and the chamber will be cut to match.

[arcticap]

Yep that's the gauge I built!

It's a great device.
I still have the original box too.
Do you still make them?

Articap,

Please elaborate. Why does consistent chamber seating depth matter? Does it have to do with the distance the bullet travels till it hits the throat?

I'm not questioning your belief that depth is important, I'm just trying to learn everything I can, so I want to know why.

Yes, in essence I'm just trying to keep the bullet a consistent distance from the rifling by measuring, and then testing to find the accurate range of bullet lengths
that seem to work the best for that gun's chamber and rifling.

Instead of using a micrometer adjustable bullet seating depth die like they use in reloading, I'm just trying to control the bullet depth inside of the chamber
since each factory bullet can be seated and crimped in a different place.

The cartridge over all length [COAL] can affect pressure and accuracy.
I think that's why the shortest and longest .22lr rounds in a box are usually not the most accurate.
The cheaper the ammo, the faster that it's made during production which can lead to more variations in case construction and the finished rounds.

"SAAMI specifies a nominal bullet diameter of 0.2255 with a tolerance of -0.004, while the specified bore diameter is 0.222. In practice, 0.224 or slightly larger bullets are common, with barrel groove diameters commonly around 0.223."


https://en.wikipedia.org/wiki/.22_Long_Rifle

"The quickest way to determine which seating depth gives best accuracy is to build three sample loads at each depth — say .015”, .025”, .035” — and test each from the bench. The most accurate should suggest where you need to further tweak your settings, whether that be deeper or in between two of your tested depths. At some point you should hit the magic spot and see your groups shrink nicely, sometimes even amazingly.....Basically you are tailoring bullet seating depth for the “sweet spot” your individual rifle likes with a particular style/brand/weight bullet. Once you’ve measured your deep-seated accuracy challenges, you can fix them."
http://dev.buckmasters.com/Magazines...the-Sweet-Spot


Another reference about COAL variables: https://bergerbullets.com/wp-content...13/03/COAL.pdf

[Patrick L]

Thank you !!

[yeahbub]

Arcticap, you seem to have gone through this in detail. When I get time, I'm going to have to study this and add the chamber depth/distance from rifling factor to sorting ammo. Just from what I've read so far, I get the impression that the ammo length/chamber depth match well on the brands the rifle likes. Your thoughts?

Patrick, my experience with gaging rim thickness isn't nearly as thorough as Arcticap, but was very effective in my Mossberg 44. I first tested various brands/styles of ammo to see what the rifle liked best and most consistently, which turned out to be CCI Blazer in 50 round boxes. For general plinking I shot it as-is, but for squirrel hunting and distance shooting, I would gage the rim thickness and separate them by each .001 of thickness and keep them in respective containers. Like Arcticap, I also found that some rims were thicker on one side of the rim than the other. If the variation was less than .001, I let it pass. Greater than that went to plinking ammo. Gaging reduced group size by half, making for reliable head shots out to 60 yards in the open woods where I hunted, given a solid rest and stationary animal. It's gratifying to keep them all on a quarter at that distance. I never spent long hours gaging mass quantities. Two or three hundred would see me through most of the summer and that can be done in an evening. I think it all comes down to your time and what it's worth to you. A gage doesn't have to be terribly pricey or sophisticated. There are some spiffy ones out there, but I got along well with dial calipers and a piece of round stock ground 1.100" long. square/parallel on each end(so your calipers will measure rim thickness starting at zero), center-bored through a few thousandths undersize and finished with a 5.75mm (.2264") drill bit and you're in business.

[arcticap]

Arcticap, you seem to have gone through this in detail. When I get time, I'm going to have to study this and add the chamber depth/distance from rifling factor to sorting ammo. Just from what I've read so far, I get the impression that the ammo length/chamber depth match well on the brands the rifle likes. Your thoughts?

Yes, a lot depends on the brand and bullet shape.
I think that every bullet shape may have its own sweet spot, and not every bullet shape will have the same "sweet spot" measurement in the end.
And then some guns just won't like some ammo at all no matter how much it cost.

I'll bet that velocity also affects accuracy as some guns prefer lower while others like it higher.
Folks buy the brand they choose and then just try to make the most of it.

I see this rim thickness gauge on the market:Raven Eye Custom Rimfire Rim Thickness Gauge for 22LR--->>> https://www.amazon.com/Raven-Eye-Cus.../dp/B0776C1DPC

They claim that the rim thickness indicates how much primer material is in the case which may affect velocity, which is aside from affecting chamber seating depth.
Read the reviews.