Rough bore

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  • Last Post 03 October 2015
bandmiller2 posted this 29 September 2015

I have always read that a rough bore is no good for cast slugs, in fact I think its carved in stone somewhere. I have an old Harrington Richardson ultra rifle in 30-06 that its former owner shot corrosive military ball in and was lax in its cleaning. The bore is dark but the rifle will hover around an inch at 100yds. with jacketed bullets. Have any of you shot good cast groups with a mildly pitted bore or is it a waste of time.?? Frank C.

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RicinYakima posted this 30 September 2015

I have had good results with removing all the copper fouling, then wiping in raw Lee Liquid Alox. After it dies, push through one dry patch. If the bore isn't good enough to take to the gun show, add another coat. Filling the pits lasts until you clean it, or the LLA falls out. Just don't shoot too fast and melt it out.

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oscarflytyer posted this 30 September 2015

haven't - but... heard a lead slug that is prob .002” overbore may do it. Heard/seen where some say they have had decent luck with this

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onondaga posted this 30 September 2015

bandmiller2

It is all conjecture till you get the bore immaculate and scope it.

I recommend you try my bore polishing method then fit bullets to the throat of the rifle. The polishing method will remove all coppering, all the black you see, clean to bare metal and polish what you have to a shine that likes cast bullets.

The polishing will reveal what you have and also be a good first step to try cast bullets in the rifle even if you don't scope the bore.

My polishing method is in the accuracy topic. Link:http://castbulletassoc.org/viewtopic.php?id=8364&forumid=63 Gary

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joeb33050 posted this 30 September 2015

Yes. I had a Peterson Ballard in 38-55 with a badly corroded bore that shot very well. With it I shot my first and only over-190 offhand score at Old Colony. At the same time I had a Schoyen Ballard in 32-40 with a rough bore that also shot very well-this more of a bench gun. With cast bullets I never saw that rough bores meant poor accuracy, I've had many less-than=perfect-bore guns that shot < 2” 5 shot 100 yard averages, and perfect-or-new bore rifles that didn't-not quickly/easily. I have a “perfect” Douglas premium air gauged barrel on a bench gun, Martini, that shoots OK but ain't a match winner, yet. However, today's barrels often or almost always shoot cast very nicely, regardless of what the borescope tells us. Some new Savage barrels are quite rough, but they D shoot cast. joe b.

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John Alexander posted this 30 September 2015

My first Savage M-12 BVSS varmint rifle bought new in 1999 for use in production class had the roughest bore, hands down, I have seen in bore scoping several dozen rifle bores. I shot the thing as was and from the start it would AVERAGE under .8” for 100 yard five shot groups with JBs and about an inch for CBs.  It was competitive in CBA competition.  After 10,000 shots and a lot of cleaning with JB and fine steel wool the bore was quite smooth and looked great but wouldn't shoot either jacketed or cast a bit better than when it was new and rough. 

If it is carved in stone that a smooth bore is needed for excellent accuracy with cast bullets the stone should be thrown away.

The only way to find out for your rifle is to use a proven bullet design fitted to the rifle and shoot it. John

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Longone posted this 30 September 2015

Frank,

I once had a P-17 that no matter what I tried would not shoot jacketed bullets to my satisfaction. The bore was not pretty, as a last resort I tried some RCBS 150 FN w/ Green Dot, it amazed me with a 3” group @ 200 yards and that was with open sights. So I guess before you give up hope try some lead it may just surprise you.

Good luck, Longone

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gnoahhh posted this 30 September 2015

I have a single shot German stalking rifle in 5.6x35R with a much less than perfect bore, with unusual dimensions- .226 groove diameter + 1/9” twist. In fact, the bore is a lot less than perfect. It is the best shooting “Hornet", with cast bullets, I ever owned. Lee Bators, as cast and with GC's (which in my case perfectly fit the throat) + 6grains 2400, yields sub-MOA groups at 50 & 100yds. Jacketed stuff, undoubtedly due to its offbeat bore dimensions, doesn't shoot nearly as well.

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onondaga posted this 30 September 2015

http://castbulletassoc.org/view_user.php?id=5654>bandmiller2

The reason I believe polishing will help your 30-06 Ultra is not just unproved theory. The minor pitting you mention does have a typical appearance. Each pit actually is an erosion crater with a top edge to a pit that is typically sharp. The sharp edged pits catch and hold fowling. the sharp edges of the pit cause the buildup of fowling and result in vertical stringing/despersion of shots as the fowling increases due to the fowling buildup associated with your minor pitting.

If you want to believe people writing that I am wrong , go ahead. I am telling you that my polishing method will round and polish the sharp edges of the pits and the pits will hold and build up less fowling. Fowling buildup that causes vertical dispersion will be reduced with bore polishing.

The materials I list for my polishing method are inexpensive and readily available. The job takes about 1 hour if you have a helper. It takes less time to do the polish than reading from people that haven't invented any method and haven't helped anybody get their bores better for cast bullet shooting.

The doubters will even say that fowling does not cause vertical stringing. The doubters will yet anyway use cleaning methods that strip bore finish away and wear their bores worse while getting no improvement over thousands of shots and wonder why.

Polish your bore, clean your BoreSnake when you are done polishing and pull the clean snake through  once every 5 shots. Try what I recommend before you believe it doesn't work according to detractors. The number of detractors is small and noisy and they don't shoot that well because their bores stink and they refuse to recognize or accept why.

Gary

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bandmiller2 posted this 30 September 2015

Geez guys what a support network, will give the polishing and cast slugs a try. Thanks Frank C.

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John Alexander posted this 01 October 2015

Frank, If you are going to try polishing your rough bore please do us all a favor and after you have cleaned your bore to remove metal fouling, and before polishing, shoot several groups with a well fitted cast bullet - say three 10 shot or five 5 shot groups.

After you have done the bore polishing use the same load and bullet to shoot another set of groups under the same conditions.  Post on the forum the results of the average group size both before and after. That would be a real contribution to what we know. Just stating our untested opinions more and more stridently shouldn't convince a rational person.

We can have all the reasonable sounding theories we can think up and have absolute blind faith in a procedure we favor, but we don't really have anything useful until we have tested out those theories with before and after testing.

The only thing close to a before and after test reported so far in this thread was my short report that a rifle with a very rough bore shot very well rough and didn't improve after the bore had been polished beautifully by use and cleaning with abrasives.  That isn't a perfect scientific test but better than anything else I have seen posted.  That shooting by the way was multiple consecutive groups in matches in front of witnesses not groups shot with a keyboard or the single good group that some folks like to post.   John

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JeffinNZ posted this 01 October 2015

I had a model 92 Winchester .32-20 that had a bore that looked like a dry river bed. Shot cast just fine.

Cheers from New Zealand

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R. Dupraz posted this 01 October 2015

Jeff, I have an 1873 Springfield TD that has a bore that mirrors your description of that “92". And it shoots big old 500 grainers ahead of a dose of Goex 3f amazingly well. No testing needed.  Just shoot it.  

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Paul Pollard posted this 01 October 2015

John Alexander wrote: Frank, If you are going to try polishing your rough bore please do us all a favor and after you have cleaned your bore to remove metal fouling, and before polishing, shoot several groups with a well fitted cast bullet - say three 10 shot or five 5 shot groups.

John, It will take more than 3 or 5 groups. 

Gary stated in an older thread about bore polishing: “If you are up to that challenge and maintain duplicating the loads you previously tested and your shooting skill remains at relatively the same level, I predict ~2% or better reduction in your group sizes."

For a 2% difference, you better shoot at least 55 groups of 5 shots. This may still not show any statistical difference, according to Joe B's formula.

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TRKakaCatWhisperer posted this 01 October 2015

Ahhhhh. Place your bets. MY prediction is that accuracy will be improved. How much? Hmmm. Not a clue. I will GUESS that there is a condition of bore that can be improved and a worse condition that improvement will be too small to measure. THEREFORE, how bad is the bore? How would one measure the roughness. Not a serious question, as the real criteria is how accurate is it and to what level of accuracy can it be brought up to.

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onondaga posted this 01 October 2015

http://www.castbulletassoc.org/view_user.php?id=216>Paul Pollard

You got me quoted correctly, 2% or better is the result I get. I don't think JoeB would do better than 2%. I think everyone else that shoots well will do a lot better.

The one pull of a clean dry BoreSnake every 5 shots I recommend is a big deal that works well after bore polishing. This cleaning keeps the rifle in a more consistent condition from shot to shot than nearly all shooters are accustomed to and adds to the 2% or better group size reduction.

The 2% or + is a small number to most shooters but is pretty significant if you are a 1MOA shooter already.

I also believe that the cleaning routine is pretty useless if your bore has not been polished well with my polishing method.

Unfortunately, if you have never had a rifle and load with jacketed bullets that you could consistently shoot 1 MOA 5 shot groups with, you aren't a good enough shot to notice a difference at all from the polishing and cleaning regimen I developed. That is not a statement to be skimmed over. You need to be a good shot first to show an improvement with the method.

Gary

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John Alexander posted this 01 October 2015

Paul, You are absolutely right. My suggestion of two 10 shot groups of five 5 shot groups could easily mislead unless the real improvement was quite large. To prove that you are getting a 2% or even 4% improvement takes dozens of groups both before and after. Let's be honest, nobody shoots that many groups before and after. Most shooters seem to think they are seeing a real difference by looking at one group before and one after.

Groups vary a lot. One group means almost nothing.  You can get a sense of how much accuracy varies from one group to another by looking at the firing tests in the Am. Rifleman.  The accuracy of the five 5 shot groups they fire usually varies nearly 100% from smallest to largest.  That is one of the five groups will be nearly twice the size of the smallest group. It doesn't happen every time but on average is is close to 100% difference. That's just the way it is for only five groups.  So when you think you are seeing an improvement by some change in load or component  by shooting a couple of five shot, or even ten shot groups you are kidding yourself unless the difference found is very large.

Of course ten or twenty shot groups are better but it's only a matter of degree the same thing applies to them only not quite as much.

To state that another way if somebody claims they get a 2% improvement by using some elixir or some procedure they are just guessing or hoping - unless they have shot a fantastic number of before and after groups under well controlled conditions. Few of us are nutty enough to spend our time that way. A 2-4% increase isn't worth the trouble.

John

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Paul Pollard posted this 02 October 2015

Some of us want to know. To determine which bullet (of three) to shoot at this year's National Match, I needed to shoot 55 5-shot groups. That is 55 groups with each bullet. Each bullet would shoot a really small group sometimes, but I needed one which would agg well over the long haul. One of the bullets proved to be inferior after 40 groups. The other 2 bullets needed 55 groups to determine the better-shooting bullet. It took spring and summer to run the test. I used Joe's statistical write up in the Fouling Shot.

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bandmiller2 posted this 02 October 2015

John I will try but the results may be skewed as I have done considerable polishing already. Is it possible to have a bore too smooth and glass like.?? Some claim less drag and leading if the bullet rides on the peaks and skips over the gullies. Frank C.

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John Alexander posted this 02 October 2015

OK Paul I stand corrected.  Some shooters do understand that it really does take a lot of groups to be reasonably sure of a small difference and were willing to pay the price to find out.  It must have worked for you because you did very well at the 2015 nationals even though shooting those puny little 6mm bullets against  big burly 30 calibers. Congratulations on your good shooting.

I tried to show that sometimes many groups are needed to see if small differences are real or imaginary in my article in the Jan/Feb 2015 TFS on finding the right amount of bullet lube.  After 5 groups with each condition it looked like one condition produced groups 13% larger than another condition.  But a simple statistical check showed that even though 13% is not a small difference, five groups of each condition weren't enough to give much assurance that the difference was real.  After shooting another 5 groups of each condition for a total of 10 each the 13% condition had completely disappeared -- or stated more accurately had never been there.

Many shooters don't like to think of statistics. Some are even openly hostile to the idea that statistics could be useful in improving our results. That is too bad. Burying our heads in the sand keeps us from learning new stuff and significance checks can be done using Joe's article in TFS. John   

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John Alexander posted this 02 October 2015

bandmiller2 wrote: John I will try but the results may be skewed as I have done considerable polishing already. Is it possible to have a bore too smooth and glass like.?? Some claim less drag and leading if the bullet rides on the peaks and skips over the gullies. Frank C.

I don't know if a bore can be too smooth. I know that some very rough bores shoot cast bullets very well and I have had very smooth bores that wouldn't shoot CBs, or anything, well -- but I can't claim that was because of their fine finish.  

You are right some have claimed that a bore can be too smooth . I can't remember if I have ever seen anything quoting decent test results that support that theory but maybe somebody here knows of such work. The"too smooth” theory you cite sounds like “common sense” and “logical” but a logical, common sense, theory is worth exactly nothing until you can show that it's works.

I understand that custom barrel makers like Shilen,Hart, and Lilja avoid lapping their bores very smooth by stopping after lapping with a fairly coarse grit.  Of course their concern is getting jacketed bullets under .25MOA so that may not apply to cast bullets

John

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