that little space

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Ken Campbell Iowa posted this 04 April 2019

this doesn't quite fit into the " shoot out lead " thread so will start a new one.

first here is a current discussion on this at rimfirecentral.com ( you don't need to join to read the text, just for the pics . )

https://www.rimfirecentral.com/forums/showthread.php?t=1156477&p=11426965&utm_source=threadloom&utm_medium=email&utm_campaign=ed1312&utm_content=iss52

next most serious shooters have some thoughts on this little space just in front of the end of the case neck ......  the obsessive mj benchrest guys advise to just ignore it.

when i was shooting ara 22rf benchrest i was bragging that my wonderful br barrels did not lead.  a shilen techie shooting with us laughed and told me yes, they all do.  so i bot a $700 borescope ... and shilentechie was right ... that little space fills full of lead on all 22rf rifles.

***************

some brands were better than others ... federal was bad, lapua not so much .. but all filled that space with lead/carbon. on one barrel i short chambered so that the rifling nearly reached the case and it still made the little ring.  shot great by the way.

***************

do harder casting alloys do that?  does it matter ?   in 22rf we told ourselves it might even make the group more consistent.  22rf can take 5 to 25 fouling shots after cleaning ...

how many fouling shots do you national record guys need ??  i hear 1 or 4 ... why so few ? alloy? ...  larger diameter to lead ring thickness ?   ... ??

ken

 

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45 2.1 posted this 05 April 2019

Interesting topic.... I wish I had some answers, but I've only got questions. I do know something on throat/leade wear patterns though....... and that depends on how it was originally chambered in front of the case neck. It isn't what you would think either as they all seem to do the same strange things!

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John Alexander posted this 05 April 2019

Ken,

I wrote a Fouling Shot article about "the gap" back in 2011 #213 but don't go back and read the article expecting to find answers.  I just described the situation and asked if anybody had ever run experiments to see if closing the gap (longer cases or shorter chambers)  It may be as much as .050" for some chambers and cases. I never got any response from anybody that claimed to know if it caused trouble.

Back about the turn of the century (I like that phrase) I made up a bunch of "match" cases for the 223 from 222 mag cases the eliminated all but a few thousandths of the gap and have been shooting them every since for most all my 223 shooting bit still don't know if it improved accuracy or made it worse. My guess is that it is just one more picky detail that some of us do that doesn't help a bit.

I hope your bringing up the subject will stir up somebody who has some answers.

John

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joeb33050 posted this 05 April 2019

 

ACCURACY AND Case length

 

 

 

In the Nov./Dec. 2001 ASSRA Journal article: “The Importance of Case Length in Cast Bullet Accuracy”, the author stated that short cases yield less accuracy than cases close to maximum length with cast bullets. The mechanism proposed is that the unsupported bullet in the gap between case end and chamber end will be expanded by the firing pressure, then the expanded section will be swaged down as the bullet moves through the throat-and the expansion/swaging will be uneven and cause inaccuracy. This article opened up a potential accuracy-improving easy and inexpensive shortcut. The article did not include any supporting data, so I imagined that what was put forth was a hypothesis.

 

            To test this hypothesis, I needed a rifle that shot fixed ammunition at high enough pressures, with sufficient accuracy, and for which extra long cases could be made or found.

 

The only rifle available to me that met these criteria was a Savage Tactical rifle with synthetic stock in 300 Winchester Magnum, fitted with a Weaver 3-9X telescopic sight. I owned this rifle for about four years, and it was reasonably accurate with cast lead bullets at slower velocities, 1200-1500 fps.

 

(We are told, and I believe, that cases that are too long will jam bullet and case neck into the throat of the rifle and cause very high pressures on firing.)

 

Pressure must be sufficient to expand the bullet into the space left by the short case. Expansion of the bullet under the gas pressure on firing is sometimes called "obturation".

 

            In a private communication with the author, he said “… obturation of lead-alloy bullets occurs at about 1500 psi times each Brinell hardness point, e.g., a Brinell hardness 10 bullet requires about 15,000 psi peak chamber pressure to achieve sufficient obturation to essentially fully seal the bore”

 

            With wheel weights reported at 9-12 BHN, the pressure required to obturate would be 13,500 to 18,000 psi. 

 

A pressure of greater than 18,000 psi was required. The Lyman Cast Bullet Handbook, third edition, shows a 187 grain 311334 bullet in the 300 WM with 17.5 grains of Unique at 1605 FPS and 26,400 psi. The load given below of a 208-grain bullet and 17 grains of Unique should produce at least this pressure, which exceeds the obturation threshold.

 

After several weeks of experimentation, I found a load that shot accurately at higher velocity:  The 311299 bullet was cast of newly melted wheel weights, weighing 208.5 +/-.5 grains, sized in a .314” die, lubed with the NRA Alox-beeswax formula and gas checked (Hornady).

 

This bullet has three bands and two lube grooves along with the gas check shank. As loaded, the first band is out of the case with none/little of the first lube groove exposed.

 

17 grains of Unique was used with no filler, Remington L.P. #2 1/2 primers, LOA = 3.455”.

 

I loaded one case at the range, sizing the neck in a Lee sizer, expanding the neck in a Lyman “M” die and seating the bullet with the Lee loader.

 

I used this load and loading method for all groups shot in this test.

 

Extra long cases were made from Federal 300 H&H Magnum cases full-length sized in 300 WM dies and trimmed to about 2.660”.

 

The chamber would accept a case of 2.648”, .028” longer than the published case length and .033” longer than the trim-to length.

 

Being chicken, I trimmed the cases to 2.643”. After extensive firing, the cases measured 2.621" to 2.630”. What happened was that the tapered 300 H&H case had blown out to fill the chamber and shortened during firing.

 

 

 

The first test with short cases.

 

On March 13, 2002, using the load noted above and one R-P case measuring 2.605” long, I shot five 5 shot 100-yard groups that averaged 1.132":

 

 

 

The test with a long case made from a 300 H&H Magnum case

 

On March 21, 2002, using a case 2.630” long made from a 300 H&H Magnum case and the load noted above, I shot five 5 shot groups averaging 1.468".

 

After shooting, the 2.630” case was 2.626”/2.628” long, it had blown out and shortened.

 

 The problem was that the 300 H&H cases were tapered, and a 300WM case formed from them and trimmed to just fit in the chamber, shortened after firing. I needed longer cases.

 

 

 

The test with a long case made from a 375 H&H Magnum case

 

I went to the Internet and asked for samples of 375 H&H Magnum cases, which don’t have the taper of the 300 H&H. Alston Jennings was kind enough to send some. I formed three of the cases to 300 Winchester Magnum, leaving the necks long.

 

 

 

On March 27, 2002, with one case formed to 300WM 2.642" long and the same load, I shot five 5 shot groups averaging 1.438"

 

After these 25 shots the case length was 2.646”.

 

 

 

The test with the long 375 H&H Magnum case trimmed short

 

I then trimmed the case to 2.605” and shot five 5 shot groups averaging 1.036", same load as above. 

 

After these 25 shots the case was 2.608” long vs. 2.605” before the shooting.

 

 

 

Lengths of 300 WM cases

 

"Book" case length                             2.620”

 

"Book" trim to                                    2.610”

 

My rifle chamber length:                    2.648"

 

            Formed from 300 H&H, case length: 2.630"             after firing, 2.626"/2.628"

 

            Formed from 375 H&H, case length: 2.642"             after firing, 2.648"

 

            Formed from 375 H&H, case length: 2.605"              after firing, 2.608"     

 

 

 

Table of group sizes fired with 300 WM cases of different lengths, inches.

 

 

 

Date

13-Mar-02

21-Mar-02

27-Mar-02

27-Mar-02

Case Length

2.605"

2.630"

2.642"

2.605"

First

1.378

1.117

0.978

0.880

Second

0.821

1.073

1.497

1.627

Third

1.111

2.224

1.099

1.106

Fourth

0.986

1.653

1.399

0.785

Fifth

1.364

1.271

1.438

0.784

Average

1.132

1.468

1.282

1.036

 

 

 

 

 

All these groups were shot at a pace determined by the time required for reloading the one case. No wind flags were used, the rangemaster stopped the shooting after each 15 minutes of “hot line” for target change. The gun was cleaned once at the end of the day.

 

Comments and Conclusions

 

I don’t like to use cases that are close to the maximum possible length. If the case lengthens slightly, then excessively high-pressures may be experienced, as the bullet and case neck are jammed into the leade/throat/ball seat.

 

The average group size for the 20 groups was 1.23”. Six of 20 were under an inch.

 

Pressure was high enough; bullet hardness was low enough (new wheel weights) and the bullet had an exposed section outside the case about 1/8” long ready to expand or obturate.        There were no called flyers in 100 record shots from the bench. There was one stranger in the third group shot on 3/21/02.

 

I see no accuracy improvement using longer cases. The hypothesis failed this test.

 

One test doesn’t establish the fact, but I have seen no data supporting the hypothesis that longer cases improve accuracy in soft cast bullet shooting. If longer cases do produce better accuracy, I want to know it. I would welcome any other data on either side of the issue.

 

            I have worked with a Savage 12BVSS in 223, forming brass from 222 Magnum cases because the chamber/brass on hand combination resulted in a gap between the end of the case and the end of the chamber. I was not able to detect an improvement in accuracy.

 

            I've been working with my Martini bench rifle and a M54 Winchester rifle, both in 30/30, both with "long" chambers. Using Buffalo Arms "long" 38/55 brass, I've formed 30/30 brass about right for the chamber.

 

 I was not able to detect an improvement in accuracy with longer cases in either of these guns. I'm still trying.

 

At high pressure and velocity, I have been able to shoot cast bullets and have a ring of lead left in the chamber. It looks like the bullet expanded into the gap between the case neck and the step at the end of the chamber, and then the resulting ring was sheared off.

 

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Shopdog posted this 05 April 2019

Just a cpl notes..... 22RF straight wall case,vs bottle neck in a CF. And 2,on 22's you're limited...at least from a practical standpoint... on neck/case chamber clearance. Where on handloads,you can change the neck clearance a whole lot easier.

Have other thoughts on CF,lead blow back and pressure waves but afraid my testing methods won't pass muster here. Good luck with your project.

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John Alexander posted this 05 April 2019

Joe,

It looks to me like your work has nailed the answer well enough for any reasonable shooter. Please write this up and submit for a Fouling Shot article. Good to have it on our forum but anything here will disappear into cyber space and be gone in fairly short order in spite of our archives.  Fouling Shots on CDs and thumb drives will have more staying power -- but also limited.

Are the results of this work in the latest version of your book? Books have a chance of lasting a long time.

It would be a shame to lose this (again).

John

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.22-10-45 posted this 05 April 2019

I have a shilen barreled .22 Hornet...chambered by the late Mr. Ed Shilen himself.  Even though I specified a tight minimum dimensioned chamber..and it is snug..the chamber is about .032" longer than max. trim length recommended for Hornet brass.  I believe this is a built in safety measure..a .222 Rem. Ruger No. 1 is also longer by about the same amount...the .30-30,s are even worse..up to 1/16" longer.  I have used lead alloys from a soft 20-1 lead-tin up to Lino.  I never had a leading problem in this area with any alloy.  However, fired cases sometimes come out of chamber with a thin ring of lube .032" long sticking to mouth of case..never lead though.  I believe there is a problem with too long/too short brass in shooting real black powder..as the sudden kick of the black obturates the relatively soft lead into any gap that exists.

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joeb33050 posted this 05 April 2019

This article is ~ 16 years old.

I got it at the Yahoo Group site "CASTBULLETINFO", in the folder 'CAST BULLET INFORMATION", where I put articles from the book in alphabetical order by title.

I set up this Yahoo Group site to store articles/experiment results, I thought that we were in agreement about that.

90% of what I've put on the site has been on the CB-BOOK Yahoo Group Site since 2006.

CB BOOK required me to allow people to become members; CASTBULLETINFO allows anyone to join.

This, and most, forums will not print tables, a PITA to say the least.

As always, Glenn is free to copy and print anything on either site, any time.

So far there are 14 members, so there is little interest in the files; I'm happy to keep adding experiment results and articles; whether anyone reads them or not. It's part of my hobby.

joe b.

 

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John Alexander posted this 06 April 2019

Looked up the article in "Cast Bullets for Beginner and Expert.  in the better format I could even remember reading it earlier. I should be worrying more about stuff disappearing out of my head than into  cyberspace. But that is a losing battle as well.

John

 

 

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RicinYakima posted this 06 April 2019

Joe B.

I can not access the files because I was  a member using Window 7. My computer is now Window 10 and I forgot the password I used. So, until I can duplicate the old password from Window 7, I can not update or reenter. I'm old and forgot it and didn't write it down on paper with a pencil. It will not let me reentry with my only email address. I am not a computer guy, can you tell?

Ric

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Dukem posted this 06 April 2019

Any black powder cartridge rifle shooters using case stretchers care to chime in?

Duke

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Tom Acheson posted this 06 April 2019

BPCR....mine is a .40-70 2 1/2 (Sharps Straight). Correctly head stamped cases aren’t real common. One route is to use slightly stretched 30-40 Krag cases. Another route is to use 405 Winch. cases. I chose the 405 Winch. cases. Out of the box they are too long so you trim them to fit the gun’s chamber. I do not have a bore scope so the presence of a little gap for lead to accumulate is unknown.

This gun has never seen smokeless powder, just BP. The gun always gets cleaned at the range following the shooting and the presence of lead is quite minimal so I can’t say that any lead streaks on the patch are from rifling or the little gap.

Tom

 

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John Alexander posted this 06 April 2019

Ric,

Sounds like a password go around I had last week. I have tons of them on a list but still find times when I am at a loss.

John

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Dukem posted this 09 April 2019

I too have a Sharps 40-70 straight. When I first got it the brass was formed form 30-40 brass. Later when Richard McKinney was rechambering 40-70s to accept trimmed .405 brass I had that done. Thankfully I bought 350 cases right away as I hear Hornady has stopped making them. (I saw a box of 50 at a gun show this Winter for the princely sum of $119.00) I find trying to trim then fire form them to leave only a .005" gap a real challenge. The first ones I trimmed to exactly 2.500" ended up at 2.482" after firing them. I was fit to be tied. Now I trim them long and fire form using a 230 grain cast .41 mag cast bullet and I can now get 2.495 to 2.499".

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RicinYakima posted this 09 April 2019

Yes, I fire form first long, then trim before resizing. The reason is that the dies excessively resize the cases and make them too long. Then when I expand the mouths, they are too short. FWIW

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Ken Campbell Iowa posted this 15 April 2019

as part of my project to create a FS index, i get to/got to read all the fouling shots ...

FS 111 ( sep.94 ) is another dandy: 

Frank Marshall opines that 0.002 long "little space" is good ; 

"" Jose Gonzales O'Tool "" ... mentions he is getting 1/4 inch groups with his Ardito rig .. and he trims 1/8 inch short     " so i never have to trim again " ...

******************

like they say, i guess that is why we have benchrest matches ...

ken

 

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John Alexander posted this 15 April 2019

Interesting. A perfect example of evidence vs. opinion or belief.  Frank Marshall was crafty but his opinions should be viewed skeptically just like all opinions.

Not all opinions are equal and none are equal to evidence to the contrary.  

John

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