.22 lr rim thickness

  • Thread starter William Colbert
  • Start date
doghunter said:
Ok, website politics aside.

A few years ago I made a gauge to check from inside the the rim to the top driving band, just like Mr.Wass was referring to.

The results were very interesting and a few of my friends made one too as we agreed that the 'luxury' of precisely seating projectiles as with centrefire reloading was not possible with rimfire ammunition.

Sure we wasted a lot of time measuring rim thickness and weighing the ammo and soon reached the conclusion that the quality control of modern 'top shelf' rimfire ammunition is very good.

So further investigation revealed discrepancies between the distance between the inside of the rim and the driving band (effective length).

Using the gauge to batch decent rimfire ammunition (Eley Tenex) it soon became apparent that a few thousands of an inch in the 'working length' made a measurable difference to the impact point. Maybe because the 'jump' was different, who knows what this does to the pressure?

Not much, but it's the difference between a 9 and a 10.

I have attached a typical photo of the results. L= 0.002" longer than the average length, S= 0.002" View attachment 21764View attachment 21765" shorter than the average length (about 20% of a typical box of Eley Tenex)

In the tight match chamber of my ancient Annie '54 apparently length does make a difference. All targets were shot at 50m outdoors on a very calm day.

Just my observation from down under.

* Doggie *
Click to expand...


doghunter,

Your gauge is most interesting. I would appreciate knowing how you control wax/lube build-up in the area of the driving band, when inserting and measuring each Tenex round? Would appreciate seeing a photo, or two, of what the chamber insert looks like in your gauge. Did you use a chamber reamer?

Yes, it might be a lot of work for the average person shooting in a local match, but if one was attending a national competition, it could be time well spent. Thanks for sharing. John
 
doghunter said:
Ok, website politics aside.

A few years ago I made a gauge to check from inside the the rim to the top driving band, just like Mr.Wass was referring to.

The results were very interesting and a few of my friends made one too as we agreed that the 'luxury' of precisely seating projectiles as with centrefire reloading was not possible with rimfire ammunition.

Sure we wasted a lot of time measuring rim thickness and weighing the ammo and soon reached the conclusion that the quality control of modern 'top shelf' rimfire ammunition is very good.

So further investigation revealed discrepancies between the distance between the inside of the rim and the driving band (effective length).

Using the gauge to batch decent rimfire ammunition (Eley Tenex) it soon became apparent that a few thousands of an inch in the 'working length' made a measurable difference to the impact point. Maybe because the 'jump' was different, who knows what this does to the pressure?

Not much, but it's the difference between a 9 and a 10.

I have attached a typical photo of the results. L= 0.002" longer than the average length, S= 0.002" View attachment 21764View attachment 21765" shorter than the average length (about 20% of a typical box of Eley Tenex)

In the tight match chamber of my ancient Annie '54 apparently length does make a difference. All targets were shot at 50m outdoors on a very calm day.

Just my observation from down under.

* Doggie *
Click to expand...

What some have done to answer much the same question is to cut a chamber in a small barrel section with the match reamer .
The OAL to the drive band gets pretty interesting, as has been found depending on barrel configuration, it would seem some barrels prefer short some long and some, does not seem to make a difference.
It also seems to have some bearing on the degree of fouling buildup in the throat.
 
center22 said:
doghunter,

Your gauge is most interesting. I would appreciate knowing how you control wax/lube build-up in the area of the driving band, when inserting and measuring each Tenex round? Would appreciate seeing a photo, or two, of what the chamber insert looks like in your gauge. Did you use a chamber reamer? John
Click to expand...

Thanks for the interest John. There is no appreciable wax build up in the driving band. When I see excess wax I wipe it off with a cotton tipped stick.
The measurement cup is Delrin, drilled accurately to 0.205". My prototype was quickly modified to include a 1/16" vent in the side as the wax seal would build up pressure inside the cup and give a false reading. Occasionally the vent should be checked to ensure that it is clear.

I have included my working drawings which should allow somebody to make something similar (sorry I am not very good at CAD).

I actually got the idea when Bill Calfee published a discussion that he had with an engineer at Eley regarding the importance of this dimension back in 2014, so I measured some Tenex, found some variations and decided to make the gauge.


Some interesting things that I did find was that Lapua Polar Biathlon is the most consistent rimfire ammunition that I have measured and the quality of Tenex has improved after the factory upgrade a few years ago.

Basically I think that is why barrel tuners work so well in rimfires, they compensate for variations in the ammunition but in some of our local events the rifle must be stock so this was my idea to help improve my scores, and it has.
 

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doghunter said:
Thanks for the interest John. There is no appreciable wax build up in the driving band. When I see excess wax I wipe it off with a cotton tipped stick.
The measurement cup is Delrin, drilled accurately to 0.205". My prototype was quickly modified to include a 1/16" vent in the side as the wax seal would build up pressure inside the cup and give a false reading. Occasionally the vent should be checked to ensure that it is clear.

I have included my working drawings which should allow somebody to make something similar (sorry I am not very good at CAD).

I actually got the idea when Bill Calfee published a discussion that he had with an engineer at Eley regarding the importance of this dimension back in 2014, so I measured some Tenex, found some variations and decided to make the gauge.


Some interesting things that I did find was that Lapua Polar Biathlon is the most consistent rimfire ammunition that I have measured and the quality of Tenex has improved after the factory upgrade a few years ago.

Basically I think that is why barrel tuners work so well in rimfires, they compensate for variations in the ammunition but in some of our local events the rifle must be stock so this was my idea to help improve my scores, and it has.
Click to expand...

doghunter,

Your description and drawing are most helpful. I plan to make a similar gauge. Thank you for sharing.

John
 
I fooled with the rim thickness thing and I never saw a difference in group size. now you sort by the front of the rim to ogive of the bullet, it does make a difference. 100 yd. 10 shot groups from an 1807 are 1" average.... jim
 
Tim et Als

tim said:
I know your from Maine, so I’ll type slow.
A. That’s not what we’re talking about.
B. On the list commentary.....largely wrong.......again.
C. I thought you took your jacks and went home.
D. That’s not what we’re talking about.
Click to expand...

Would you tell me what winning matches has to do with anything except to those who's egos won't allow them to enjoy living to just enjoy doing what they are doing?

There are a few people who will do anything to win at no matter what they do and some of them have all but destroyed IR 50-50. So, you tell me, who is the fool here?

I sleep well every night loving my life and being wherever I am and participating in whatever I choose to do. Even when I won a fair amount, it never really meant that much to me and the last few years, I have not been all that excited about winning anything. What is there in it when one wins something. The year I won the IBS Shooter of the Year I never experienced such a hollow feeling for having worked so hard for so many years to do it. So to that end, I quit the full force, head on competition and decided to enjoy the trip first.

I have no heroes and don't wish to be one myself. I feel sad for those who can't go places and just enjoy being there , making new friends and visiting long standing ones. Unlike some, I have a vast array of great friends I've had for years and it's basically to visit with them that has kept me at this for the past few and of course to be able to antagonize you and some of your pals. So, there is is. I get what I want out of it, regardless of how it looks to you bigger hat sized folks.

70 and sunny here today. Just finished pruning a few plants and shrubs. Life's good.

Pete
 
you might want to check

GordonE said:
PETE
Your dumb ass Approach to cambering a rimfire is stupid!!!!!!!!!!! Put some effort into learning before you put your mouth in gear. Last or close to is failure!!! iR 50/50 NATIONALAS

THE thief from NY
Click to expand...

the Sporter scores of the Maine State on 7-14 before you come to that conclusion, just sayin :).

Pete
 
Maine Scores Suspect Big scores at Capital City What happened at the Nationals? DARK CLOUD Just sayying EH !11111111111111
 
Good Morning America

5 days into a heavy Virus medical science has yet been able to determine its nomenclature. Had to go to the ER yesterday to get hydrated. It ain't the flu sez them, or anything else they know of. May be the tailing of the virus I acquired in Bristol, which lasted 6 long weeks. Another good example of no good deed going unpunished is my take. Have to wait er out is all. They told me to drink 12- 8oz glasses of water each day, and with a straight face !

Pete
 
Self induced

linekin said:
Seems like you’ve drawn the short straw of late Pete.
Get well my friend!
Keith
Click to expand...

I got drunk and bragged that I hadn't had a cold or flu in about five years back in August. Knew better but the evil alkehall will make a man do things he wouldn't otherwise do. I got harf the water down thus far. :)

Pete
 
Creeping Crud

Day 6 of the "unspecified" VIRUS. Visited Togus ER yesterday. Treatment was IV to rehydrate, magnesium tab, and Dr. Advice to take Imodium AD after bathroom trips. So there is no medical explanation for this case of THE REVENGE out here either Pete.
 
Butt Plug

Pete
You could Be the next Louie Pasture. You could Make one for you and one for Klaton. Hell while your at it make one for Gary. He may end up shootuing a 19xtarget.
 
Put some

Pete Wass said:
I got drunk and bragged that I hadn't had a cold or flu in about five years back in August. Knew better but the evil alkehall will make a man do things he wouldn't otherwise do. I got harf the water down thus far. :)

Pete
Click to expand...

lime juice in the H2O...goes down easier and may remind you of a gin and tonic!! Hope you feel better.
 
Fan Mail

GordonE said:
Pete
You could Be the next Louie Pasture. You could Make one for you and one for Klaton. Hell while your at it make one for Gary. He may end up shootuing a 19xtarget.
Click to expand...

Just some more fan mail from Some Flounder looks like to me.
 
Thanks Pete!

FBecigneul said:
Where did you finish, Gore?
Just asking.
Click to expand...


I have offered Jason Frymier use of the Facility to have IR50/50 UL Indoor Matches if he wants to try it ! He got with Mike Cameron to see if the Georgia Crew of 50/50 could Stimulate the effort ! I watch the entertaiment from the NYecker on here like above , the main thing is to show up and shoot some where ! I don`t think I have ever met either of you ,but I have met Kieth from Maine and he pushes pretty hard ! Try the Triple Crown this year , it`s the biggest thing in Rimfire and mixes all of us together for 22RFBR ! Maybe some ECK guys would show and support Paul ,he ain`t got a sniff from 50/50 NY guys and he takes up for them some times ! Think 22RFBR! Show up & Shoot!

Almost Forgot ; Tim Longcore from way up near Lake Michigan won down here this past weekend , that is something that makes us feel good !
 
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