Can indexing bullets improve groups

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  • Last Post 25 February 2015
John Alexander posted this 12 February 2015 

           

    Indexing is certainly useful for telling which bullets came from which cavity when the cavities aren't alike.  It is at least conceivable that in certain cases with really bad bullets that indexing may help shrink groups.  But a lot of good shooters don't index bullets and win without doing it.      Does anybody know of any systematic studies that give information on how bad (and in what way) a bullet has to be before indexing will show a measurable decrease in average group size?    Is it instead just one of those things we blindly do because we read somewhere that it works. Or maybe do in the hope that the more trouble and time we take to reload groups will magically improve.    My own tests were with bullets from a single cavity mold that was beagled out of round and in which the halves were offset more than .001".  These defects made me think that indexing would help. The bullets were shot in a falling block rifle so I could easily and precisely index bullets. I shot a lot of groups but could detect no difference in average group size compared with not indexing.    However, that was with one bullet design (similar to NOE 22570 RN) and in a rifle only capable of averaging about 1MOA for five shot groups.  With different or worse bullet defects, or with other bullet designs, or at higher levels of precision, results might be different -- but do we know?    Maybe we should try to find out.    John

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OU812 posted this 12 February 2015

Maybe hard alloys benefit most by indexing. Softer alloys not so much?

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Bud Hyett posted this 12 February 2015

A half century or more ago, Norma published a study on jacketed bullets, their 6.5 mm 139 grain match bullet, where they altered the nose and base to see what impact this alteration would have. Expectedly, any alteration to the nose or meplat was of negligible impact and any alteration to the base immediately increased group size. If I remember correctly, this was a short article in the American Rifleman. They made cuts in the base and indexed the bullets, they cut the nose off at diagonal angles, the made cuts on the meplat, it was an interesting experiment to read about. If I recall correctly, they used ten-shot groups for the standard of comparison. While a jacketed bullet, the results would be similar with cast. Norma chose this bullet since it was a recognized match bullet. In the late 1950's, this bullet was one of the best match bullets. They shot the altered bullets without indexing to see if that was an influence. Norma indexed the bullets and found the bullets were predictable as to impact. This indexing was at 90 degree intervals and the bullets impacted in the same area relative to the cut both in base and meplat. Their conclusion was that any irregularity was an influence on group size. The irregularity in the nose and meplat area was less than an irregularity on the base. The indexing did help reduce group size, but was not a cure. While hardly surprising to a dedicated cast bullet shooter, this was an interesting article and caused much discussion at the range bull sessions. 

Farm boy from Illinois, living in the magical Pacific Northwest

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RicinYakima posted this 12 February 2015

WOW! “A half Century or more” sure sounds a lot longer ago than “before I was drafted". Remember the article and controversy pretty well, but most folks forgot it almost as long ago.

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tomme boy posted this 12 February 2015

Only going to matter if your chamber is not true to the bore.

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joeb33050 posted this 12 February 2015

No, of course not!

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John Alexander posted this 14 February 2015

OU812 wrote: Maybe hard alloys benefit most by indexing. Softer alloys not so much? Maybe.  But who knows? Nobody knows, because we haven't done the work to find out. It is easier just to believe the old husband's tales passed down to us.  Sixty years after Col. Harrison published his attempts to find out what makes cast bullets work, or not work and got some answers (even though some of them were wrong) we still don't know some of the basic things we need to know in order to improve cast bullet groups.   Bud and Norma are right a known substantial defect like bases not square to the long axis of the bullet or a hole drilled into one side of the bullet degrade accuracy and if you know where the defect is you can index it the same for each shot you can get better groups. Several experimenters probably starting with Mann have done it. But it is hard to see how that could that possible apply to real bullets where gas checks are sometime less than square with the axis but bear no relationship with the parting line on the bullet.  We fear internal bubbles but there is no chance that indexing will help because the bubbles are randomly placed if there at all.  If indexing does help why haven't we had a good test to prove it.  Maybe Joe has done one he seems pretty certain.

John   

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Maven posted this 14 February 2015

Frank Marshall said it made a difference in a “Speaking Frankly” column reproduced in Lyman's “Cast Bullet Handbook, 3rd. Ed.”  He even provided targets:  indexing v. no indexing accuracy.

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John Alexander posted this 14 February 2015

What page is that article on?  I have the 3rd edition but got sidetracked by a couple of other Marshall articles.

You are right the late Frank Marshall, one of my favorite gun writers, said it made a difference.  So have a lot of other shooters.

Marshall didn't just give his opinion but also reported on tests that he had done that showed fantastic improvements by both indexing and sorting by weight.  Probably his most widely read article starts on page 140 of the NRA publication “Cast Bullets” edited by Col. Harrison.  I would urge any interested cast bullet shooter to read Marshall's article and then go back and read it again and compare his reported results to your own experience. there are several things in he article that are quite amazing. I will only mention a couple of his results that caught my eye.

Bullets visually OK but not indexed and not sorted by weight produced groups 4.3 times as big as those by bullets indexed and sorted to .1 grain variation in weight.  

Bullets visually OK and indexed and sorted to .5 grain weight variation (two tenths of one percent) variation on the 219 gr. 211284) produced groups 2.3 times as big as the same bullets indexed and sorted to .1grain variation (four one hundredths of one percent.)

I have done similar tests and have never been able to see ANY improvements by either indexing or sorting by weight.   I suppose one possibility is that Marshall tested a really bad batch of bullets. There may be other explanations. 

John

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Maven posted this 15 February 2015

Sorry John, but I can't give you a  page no. as I'm 1,500 mi. from home...in sunny Fla. (I think you can guess why!) ;)

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joeb33050 posted this 15 February 2015

Cut a “V” on the rim or base of the case.

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RicinYakima posted this 15 February 2015

I can not find it in the Lyman book, however it is reproduced on page 140 of Harrison's “Cast Bullets” published by the NRA.

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joeb33050 posted this 15 February 2015

Put a dent in the mold so the bullet has a dot.

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joeb33050 posted this 15 February 2015

Put the V or the dot or both at 12 o'clock in the chamber, and shoot a lot of shots with dot or V or both or none aligned.Measure the groups.See that there's no discernible difference in group size. Note that at least some times in bolt guns the ctg case with bullet rotates as the bolt closes. To align anything in bolt guns the ctg must be forced in the chamber until refusal, then bolt-preferably without extractor, is closed. Even then you're never sure the ctg didn't rotate as bolt closed. I've tested with a 30-30 Martini bench gun, a 32-40 high wall with bresein barrel owned by Ken Hall, a Hepburn 30-30 with bud welsh barrel, Schoyen Ballard in 32-40 and Peterson Ballard in 38-55. It's just another fairy tale, alignment changes nothing.  I've NEVER read a credible report of alignment of bullet, case or both increasing accuracy.

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John Alexander posted this 15 February 2015

RicinYakima wrote: I can not find it in the Lyman book, however it is reproduced on page 140 of Harrison's “Cast Bullets” published by the NRA.

Thanks Ric.  Yup, that's the version I was quoting from --  one of the bibles of cast bullet wisdom. I wonder how many thousands of hours of useless labor that article has inspired?  John

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John Alexander posted this 15 February 2015

Joe,

Thanks for the summation of your testing the effectiveness of indexing.  I withdraw my comment in my post #7 that “nobody knows.”  I guess I should finish reading the latest edition of your book -- or maybe it's just the memory thing.

Maybe everybody has figured this out and nobody is still indexing.  If some shooters are, I wonder if they have test data to support the practice.  How about folks shooting aggregates close to .5 MOA?  Can a positive effect be shown at that level of precision?

I know indexing can be shown to improve groups with big artificially manufactured flaws. But does it ever help with actual cast bullets not deliberately damaged?

John

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TRKakaCatWhisperer posted this 15 February 2015

John Alexander wrote: I know indexing can be shown to improve groups with big artificially manufactured flaws. But does it ever help with actual cast bullets not deliberately damaged?
Agree (first part).  Mann's volume documents it well.  So the question is (cast bullets not deliberately damaged) what unseen defects are there?  Where do these defects occur in the bullet and how REPEATABLE are they in size and/or location? Now we're talking about a level of precision of casting (and other operations of bullet preparation). I would ASSUME that some level of precision is gained by bumping/swaging and other processes.  My assumption is that there are some measurable benefits in the reduction of variations that affect accuracy.  Are these improvements so small that NO ONE has been able to measure and document them?  Perhaps, perhaps not. This raises the question of techniques of measurement.  There certainly are other measurement techniques of precision of anything manufactured.  Most of these are well beyond the capabilities of most all of us.  (I would love to take several hundred bullets  into work and check each one with the CMM.) Mann published a picture of a device to spin each bullet and to observe it's level of instability/stability when spinning on it's nose.  He discovered that a void could be found by that technique.  Certainly it stands to reason that a bullet if unstable in it's spinning would be less accurate that those that are stable. There is room for more good research here.

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TRKakaCatWhisperer posted this 16 February 2015

Hmmm.  There is an obvious advantage to indexing bullets that are not aligned in the case.  Measuring is straightforward, supporting the case in a number of ways (just observe the different styles of Sinclair gauges) and using a dial indicator.  Both sorting for smaller amounts of run-out and by indexing the round; again see Mann's volume. This gets back then to the original question of indexing JUST the bullet.  One simple method of indexing just the bullet would be to breech-seat and study the results.  Easy enough if you breech-seat.  

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joeb33050 posted this 16 February 2015

TRK wrote: Hmmm.  There is an obvious advantage to indexing bullets that are not aligned in the case.  Measuring is straightforward, supporting the case in a number of ways (just observe the different styles of Sinclair gauges) and using a dial indicator.  Both sorting for smaller amounts of run-out and by indexing the round; again see Mann's volume. This gets back then to the original question of indexing JUST the bullet.  One simple method of indexing just the bullet would be to breech-seat and study the results.  Easy enough if you breech-seat.   "There is an obvious advantage to indexing bullets that are not aligned in the case." Maybe a theoretical advantage, obvious to theorists, but I never found an advantage breech seating. Or read of experimental results showing one. "Measuring is straightforward, supporting the case in a number of ways (just observe the different styles of Sinclair gauges) and using a dial indicator.  Both sorting for smaller amounts of run-out and by indexing the round; again see Mann's volume."This seems to be about coaxial cartridges and measurements of concentricity. Pounded into dust elsewhere. Where in his book do you find Mann's talk about runout and indexing? "This gets back then to the original question of indexing JUST the bullet.  One simple method of indexing just the bullet would be to breech-seat and study the results.  Easy enough if you breech-seat."I did breech seat, in SS rifles, as described, and never found any relationship between indexing and accuracy-nor have I ever read a credible report of such.

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TRKakaCatWhisperer posted this 16 February 2015

I'm not ARGUING here.  Simply pointing out issues and aspects of the topic at hand. I look to those people that HAVE found success.  Just not finding nor recognizing it is not good enough.  MEASURE the effect and publish it.  The first step is clarification; research follows.  

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John Alexander posted this 16 February 2015

TRK wrote: MEASURE the effect and publish it.  The first step is clarification; research follows. Amen!  That's what we don't do much of.  We are going to have to begin doing that again just as the folks who got us to where we are did in the 70s and 80s (Ardito and others at that time.) -- but only if we want to improve.  Those who are satisfied with what we can do now of course won't be interested and that is OK too.  They may have as much fun but they won't learn anything new.    The other thing that would help would be put into practice what we do know instead of just doing the same thing more precisely. I wrote an article four years ago (TFS #213) showing that bullets with big gnarly wrinkles shot just as well as “perfect” ones at the .8 MOA level of precision. 

But we still have “serious people” advocating examining bullets with a magnifying glass and remelting bullets with tiny wrinkles all without offering one bit of test results showing that it does any good - just their uninformed opinion.  But, especially if it's in print, some folks will buy a magnifying glass. Cast bullet shooter's critical reading skills seem no better than the general public's.

Just trying to be more precise with our casting and loading procedures ain't doing the job as Joe's compilation of groups at the CBA nationals show.

John

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