Author Topic: cheap ammunition, concentricity, barrels, and chambers. (Read 3326 times)

lucho · « **Reply #30 on:** November 17, 2004, 08:20:46 AM »

Dan

I would say that for real ammo and guns that the group one would get would be bigger that your theoretical group sizes. Which is to be expected, for the reasons you stated.

Ammo I have shot gives about

2+ inch groups for 70 ft/sec spread
1.5+ inch groups for 50 ft/sec spread and
1" groups for 30 ft/sec

So I would say that chamber, harmonics, rest, .....account for about 1/4 of the accuracy of a rifle/ammo combination.

I have to admit now that if I could get 1.1 inch groups from 50ft/sec ammo I would be very happy. If getting a tight chamber would insure that I think Dave would be right and you would save monney in the long run. And it might be worth doing.

How do you groups differ from the theoretical groups?

Lucho

PS All this talk about ammo and tight chambers shouldn't keep the newbie from shooting what they have or what they can afford. Silhouette's is a fun, exciting sport at any level. We just get off on talking about these "mice nuts" issues.

tirador · « **Reply #31 on:** November 17, 2004, 01:54:50 PM »

Dave, Dan and Lucho, I appreciate the advice and the what could happen if...

Frank Tirrell who writes for the Small Caliber News and the Precision Shooting Magazine amongst others has actually experimented with .22 Rimfire Chambers ("Small Caliber News" Winter Edition 2003 Vol.6 No.4).
In the article Frank Tirrell compares SPORTING CHAMBERS (read lose) to MATCH CHAMBERS (read tight) and comes to the conclusion that match chambers perform better than sporting chambers because they were designed for the purpose of attaining better accuracy. He quotes F.W. Mann the author of "The Bullet's Flight," published in 1909 "where he goes to great lengths to point out that a projectile that starts crooked in the bore does NOT straighten out in the bore. In turn it exits the barrel crooked allowing gasses to escape out one side tipping the projectile even further enlarging the projectiles gyroscopic spin on its route to the target" In my opinion a very interesting article.

Frank Tyrell has authored other rimfire articles for "Precision Shooting" in one of them using a sander he removed lead from the tip of some Eley 10x bullets so they looked like semi wad cutters and achieved better accuracy, believe it or not.

Frank Tyrell has also designed a nifty little tool that removes the ring of lead that forms just ahead of the chamber, which affects accuracy and is very difficult to remove.

For those of you that wish to read the article in its entirety I will include the phone number of the Editor of Small Caliber News 330 897 0614 and their Web link www.smallcaliber.com by the way I have nothing to do with either magazine I just find their articles interesting and at times very helpful.

I came to the same conclusion as Dave's of using custom barrels with match chambers to be able to use less expensive ammo with success some twenty years back. Tony

dave imas · « **Reply #32 on:** November 17, 2004, 03:40:55 PM »

Thanks Tony for confirming the thought process. The problem I was having was that I didn't realize that there is a significant difference between the Anschutz "match" chamber and a Lilja "match" chamber. The differences between a sporter chamber and the match chamber were intuitive. It was the subtle design differences but significant performance differences between the match chambers that I've found so delightful.
dave

TX Charlie · « **Reply #33 on:** November 17, 2004, 04:06:57 PM »

Toooo serious.
The correct method for ammo selection requires one to walk the firing line selecting one individual to loan you their rifle and ammo. Shoot the match with that equipment, FREE bullets are the BEST.
With the equation of FREE bullets and a loaner rifle one will shoot a great score or a bad score. If it is great then the story will be good and getting better with each telling. If the score is bad then you have many excuses, certainly not your bad shooting. FREE bullets are the BEST

tirador · « **Reply #34 on:** November 17, 2004, 05:10:31 PM »

You are most welcome Dave, regarding the differences between match chambers this is what Frank Tirrell in his Small Caliber News article has to say about them.

"Some manufacturers of 22 rimfires here and abroad have gone as far as to develop their own theories on chamber dimensions in an attempt to improve accuracy and provide the shooting public with better accuracy and have promoted them as production target models. However, they seldom outshoot the custom rifles built by the perfectionists who are acutely aware that real accuracy is in the details."

tirador · « **Reply #35 on:** November 17, 2004, 05:22:44 PM »

Charlie, Agustin Sanchez does it your way all the time with borrowed rifles and sometimes borrowed ammo. Last year he came in second at the Nationals on smallbore Hunting rifle using Federal 711 (He used Federal 900 with his Standard rifle) this year I made sure he was not taking any chances and had him use Eley Tenex for both matches instead.

tedfl · « **Reply #36 on:** November 18, 2004, 03:26:03 AM »

In case there are some of you that havent read this article, It might help to further clarify this discussion.

Tedfl

http://www.bellmtcs.com/FAQ/ChamberThroats101.htm

DanDeMan · « **Reply #37 on:** November 18, 2004, 05:34:45 AM »

Yo Lucho,

For real ammo and guns the groups seem to be smaller than the theoretical vertical dispersion listed that was solely a function of velocity variation. A number of years ago when we were shooting the Mexican PMC Scoremaster for practice and the 320 Super Match Fiocch for matches I did a lot of testing on Tuesday nights in totally calm conditions. The PMC typically would produce a velocity extreme spread of 50 to 60 fps for a 50-shot string over the Oehler chronograph. When 50-shot groups were shot at 100 yards the core group would be about 1. But out of the core group would be a few (5 to 10%) fliers that would open the group up to about 1.5. The 320 Super Match Fiocch typically had a velocity extreme spread of 25 to 35 fps. Those 50-shot groups usually had a core group that was a bit smaller than ¾ but the fliers only opened up the group to about 1. Certainly there was human error in the results, but after a number of times shooting 50-shot groups it was evident that the group size was consistent.

One of the reasons for shooting large groups was to see if there was any process drift. I was interested in seeing of the POI would change through the long string of fire. The rebarreled Anschutz 1808 did not show any POI drift. The original barrel on that rifle did show changing POI that would settle down after about 5 to 7 shots, not a good thing for silhouette shooting. That is why it was rebarreled with a custom barrel and tight match chamber.

One issue about tight match chambers is the chamber should not be so tight that the brass is burnished after extraction. That tight of a chamber will often not allow a live round to be extracted. That can be very dangerous as some can attest to. It is my experience that the engraving on the bullet is the most important part, not a super tight fit for the brass.

The 22LR was originally a black powder cartridge and it still is affected by the same issues that black powder cartridge rifles (BPCR) have. After a number of years of extensive BPCR testing, reamer design, bullet design, etc., I can say without equivocation that bullet-to-bore concentricity is the foundation for top-level accuracy. It is necessary, but not sufficient to excellent accuracy, but it must be in place for the low velocity variation and good gunsmithing to have their effects on accuracy.

shootingpaul · « **Reply #38 on:** November 18, 2004, 03:59:12 PM »

and what about rim thickness sorting tests?
I read one article that stated overall 5% accuracy improvement for sorted ammo, I was just wandering what is your opinion on that?
bring it on boys!!!!!!!!

dave imas · « **Reply #39 on:** November 18, 2004, 07:35:54 PM »

Pavel,
that one is easy. don't waste your time. most benchrest folks that have tried it stopped. not worth it. no significant improvement. if you have a 2" group at 100 meters and realize a 5% improvement you have a 1.90" group. A 1" group goes to .95" a .50" group at 60 meters goes to what... .475"? i don't think i could even measure the difference on the target. too much work for way too little return on investment.
dave

greer · « **Reply #40 on:** November 22, 2004, 03:49:27 PM »

Hey Dave, did you ever check to see which blue box you're using? Thank you, Sarah

dave imas · « **Reply #41 on:** November 23, 2004, 04:15:04 PM »

Hi Sarah,
I've yet to get home. I'll check as soon as I get there. Probably not till middle of next week.
dave

greer · « **Reply #42 on:** November 24, 2004, 01:59:01 PM »

Thanks Dave, I'll be watching for your post. Hope you enjoy the holiday. Sarah

davei · « **Reply #43 on:** November 29, 2004, 03:37:43 PM »

for those that are interested the ammunition i have been using is
Golden Eagle Target. Eley Prime, Hecho en Mexico. i made the assumption it was made by the same folks that make Aguila. is that incorrect?
dave

greer · « **Reply #44 on:** November 30, 2004, 10:46:53 PM »

Thanks for getting back with us, Dave. Near as I can see, the Golden Eagle Target is listed with all the other Aguila ammo. Thanks again, Sarah