.22lr rim thickness gauge?

[hunter87]

Been toying with the idea of getting one but do they really work anyone here have any experience both good or bad?

http://www.intershoot.co.uk/acatalog/Gehmann-Rim-Thickness-Gauge-138-128.html

[achosenman]

I sort my 22lr ammo by rim thickness. It makes a huge difference with some brands of ammo, Eley hp subsonic to be exact.

 

The rim thickness variation is astounding for a supposedly premium manufacturer. It really shows up at long range, 100yds or so. It matters not so much about the thickness but that they are all the same. It takes about 30 minutes to sort 500rds using an accurate set of callipers and a empty 223 case. There is no need to bin any rounds, they just have to be batched by rim thickness

 

RWS hp sub sonic have identical rim thickness and there's no point in trying to sort them.

 

ATB

[hunter87]

Thanks for the heads up achosenman really appreciate the advice

[Foxshooter]

Works well with HMR ammo too. By batching you take out the odd fliers that seem to turn up without any good reason

 

Mark

[gbal]

I sort my 22lr ammo by rim thickness. It makes a huge difference with some brands of ammo, Eley hp subsonic to be exact.

 

The rim thickness variation is astounding for a supposedly premium manufacturer. It really shows up at long range, 100yds or so. It matters not so much about the thickness but that they are all the same. It takes about 30 minutes to sort 500rds using an accurate set of callipers and a empty 223 case. There is no need to bin any rounds, they just have to be batched by rim thickness

 

RWS hp sub sonic have identical rim thickness and there's no point in trying to sort them.

 

ATB

Very interesting.

What sort of difference in POI are you finding?Is it in any way related to the rim thickness..eg thicker gets progressively more deviant? Eley,especially,though I don't often shoot them much beyond 50y.

Just how do you do it!? 223 case etc

Gbal

[achosenman]

Very interesting.

What sort of difference in POI are you finding?Is it in any way related to the rim thickness..eg thicker gets progressively more deviant? Eley,especially,though I don't often shoot them much beyond 50y.

Just how do you do it!? 223 case etc

Gbal

Just use a fired 223 case. Pop the primer out and measure the 223 case, re- set the zero on the callipers. Drop the 22lr round into the neck of the 223 and re-measure. what you get is rim thickness.

 

Mine all come out at .041/.042/.043 thou. On my rifle I get a far better accuracy using .042 and.043 rim thickness. I think this is going to change since I have just had my Rifle back from Callum Ferguson who has installed a new Lilja barrel for me. I've yet to shoot it but I'm down with a nasty bout of flue or something at the moment.

 

The difference in impact is about .5moa between the .041thou and the .043 thou batches. I re zero for each batch since it only takes a few shots and 50 yds is easy to find on pretty much any patch of ground.

 

Doing the above allows me to punch the centre out of the 1 inch target patch at 100yds with no fliers. To my mind it make the 22lr vastly more reliable and usable at range. I hate inaccuracy in any rifle, be it PCP pellet gun, or a centre fire. There is absolutely no excuse these days.

 

I'm not sure what the truth is about what is happening with rim thickness. One theory suggests headspace, another goes on about differing amounts of primer compound spun into the case during manufacturing process. They thicker the rim ( more internal volume in the rim) the more primer compound, so it changes the cartridge since as a percentage it makes up quite a bit of the entire propellant force on firing.

 

I only wish it wasn't worth doing because it can get tedious, but every time I take that 100yd headshot, I'm glad I did.

 

ATB

[gbal]

Just use a fired 223 case. Pop the primer out and measure the 223 case, re- set the zero on the callipers. Drop the 22lr round into the neck of the 223 and re-measure. what you get is rim thickness.

 

Mine all come out at .041/.042/.043 thou. On my rifle I get a far better accuracy using .042 and.043 rim thickness. I think this is going to change since I have just had my Rifle back from Callum Ferguson who has installed a new Lilja barrel for me. I've yet to shoot it but I'm down with a nasty bout of flue or something at the moment.

 

The difference in impact is about .5moa between the .041thou and the .043 thou batches. I re zero for each batch since it only takes a few shots and 50 yds is easy to find on pretty much any patch of ground.

 

Doing the above allows me to punch the centre out of the 1 inch target patch at 100yds with no fliers. To my mind it make the 22lr vastly more reliable and usable at range. I hate inaccuracy in any rifle, be it PCP pellet gun, or a centre fire. There is absolutely no excuse these days.

 

I'm not sure what the truth is about what is happening with rim thickness. One theory suggests headspace, another goes on about differing amounts of primer compound spun into the case during manufacturing process. They thicker the rim ( more internal volume in the rim) the more primer compound, so it changes the cartridge since as a percentage it makes up quite a bit of the entire propellant force on firing.

 

I only wish it wasn't worth doing because it can get tedious, but every time I take that 100yd headshot, I'm glad I did.

 

ATB

Many thanks for a really clear and informative reply.Half an inch at 100 is quite important in the context of head shots,but its good that batched by rim thickness are consistent,'just' different POI-I suppose it might be .5 moa either way,so up to 1 moa in an unsorted box...

Anyhow,agree about the ethics of accuracy-but being accuracy oriented,I'm going to use a 222 case! or even a 22PPC one!! :-)

Gbal