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Discussion Starter #1
Hello to all, I am new, and my introduction is entered in "General Discussion". I have a couple of questions on backboring: I have an 870 Rem. barrel (3") that has been Briley choked, (screw in) and the forcing cone has been lengthened to 2 1/4". This barrel has been shot a lot, and is shot scarred just beyond the cone. I tried to polish it with Flitz but the marks are still there. I would like to have this barrel backbored and polished, but am uncertain this can be done with it having a screw choke. Any comments? Also, if this can be done, approximate price?
 

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OK....A couple of questions. Has the barrel been used for steel shot? Flitz is great for closing the pores and burnishing the barrels, but you will need something else to smooth out the barrel.
Now, for back-boring. There are good points and bad points. Forget the hype and type put out by today's gun writers. Back-boring helps the problem of steel shot bridging in the forcing cone and choke, but not much else. Problems can happen when one reloads if using one piece wads...they are under size and don't seal very good. In fact, the only overpowder wad I have found that would seal in BB barrels is the Ballistic Products X12X.
Now....You would have a problem with your choke tubes. They are set up now for the shot to transistion from a .720"+/- barrel, where the BB barrel would be .740"+/-
I think a must better solution would be to use a brake hone on an extension and polish it out near the forcing cone with a vari-speed drill. It's not a complicated process and Brownells has everything you would need. Some use a alum rod, split, and 300 grit paper, finishing up with 600 grit. I like the hone beter.
Best Regards, James
 

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Discussion Starter #3
James: Thank you for your response. Your suggestion of honing is the one best solution. I would assume that I would follow up on the honing with polishing. Am I correct on that? Your second paragraph answered my question perfectly, as that was my exact concern. When I do the honing, I would assume that the depth would be controlled by a stop or jig on the bit shaft. Is that correct. Thank you very much. You have helped considerably. Also, FYI.......No, I have never used steel shot in this barrel, but I have shot plenty of high antimony copper plated shot. I use the BP 12  wad and the corresponding gas seal. I have yet to try the "Turkey Ranger" wads, but that is next on my project list......LOL. Thanks again, RR
 

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Since no steel has been used, you might want to try one trick before the honing. Stop by a supply house and buy a tube of JR1 (jewelers rouge 1). Go bu your gun store a get a 10 cotton mop. With it installed on a secrtion of shotgun cleaning rod and hand drill....dampen it with some fine oil and then smear it with the JR1. Spin it through the forcing cone out to the end of the scratches. Many things this will solve the problem. Later this mop, after being washed and dry, works great with Flitz to remove fouling and plastic residue.
Yes...mark your extension with black tape when using the hone. Then finish up with JR1 and then Flitz. I might add that I have seen bad plastic wad build up that appeared as scratches, however the Flitz should have removed that. Strange though...I have never scratched a bore of even the softer steel used in the older doubles with copper-plate. Keep in touch and let me know how this project comes along.
Best Regards, James
 

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If I may respectfully disagree, I like backboring, but I am not sure it is worth the cost.  I did pick up (modest) velocity gains and pattern improvements.  As long as you do not go over 0.010", I haven't had any problems with gas sealing.  As noted above, the Ballistics Products wads are best, but I've used all kinds, even some OLD Alcan with no problems.  
Your 870 can be backbored, with the screw-in chokes, if the leading edge of the tubes is 0.010" or greater than the bore diameter, and most of them are.  But, keep in mind the results may no longer exactly match what's on the choke tube the way they did before.
I too am surprised you have scratches forward of the forcing cone.  If so, I wouldn't go to backboring JUST to sovle this.  If they are linear scratches, keep in mind they are touting linear grooves to stop spin and improve patterns, so you may be partway there for free.  Are you sure it isn't plastic?  Some of that stuff can be mighty tough, and it is very abrasion (i.e. Flitz, Semichrome, etc.) resistant.  For removing plastic wad buildup, wrap some cloth around an old bore brush.  Go OUTSIDE.  Slosh some laquer thinner or even better acetone on the cloth and swab the bore.  Voila, plastic gone!  Do not light a congratulatory cigarette (if you have the vice) or you may go up like a Roman candle.  Stuff is volatile plus, but it sure works.
Good luck.
 

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I'm not quite sure as to what I said that Virginian is disagreeing with? Except maybe my statement about your choke tubes. I am aware that there is a slight flare on the leading edge of the tubes. However, there are other choke considerations to take into consideration.
Let's go back and look at back-bored barrels. There is quite a difference in shotgun barrels, even from the same manufacturer. I have seem more than .010" difference in Remington barrels themselves. The most consistant barrels I have miked so far are the new Browning and Wivhester barrels being made onthe large hammer forge machines. Their specs are .720" on regular barrels and .740" on BB'd barrels. I have found, as others have, European barrels running as tight as .700"
Now, there are no established specs on BB'd barrels out there. I have seen barrels ruined by going as high as .760" by shade tree gunsmiths. When I was refering the the tubes....Any chage in the relationship of bore diameter to choke tube diameter will change things.
As far as blowing the gas seals...I can, and have, blown most of the one-piece wad seals on most of those wads in a .740" bore. Remington Power Pistons are the worst with the very shallow cups. Winchester AA wads, although they have a deep cup, are under size for the tapered AA hull.The only wads that works consistant in .740" and up BB'd barrels are some of the Ballistic Products deep cup wads, including the X12X, and the Win Red wad. When working with slow burn powders and heavy shot loads, not only the diameter of the wad is important, but also how flexible the plastic is.
So.....there are no set rules. BB'ing does change the constriction in existing choke tubes, even at polishing out a barrel .010", when stating back-boring, that can cover anything from .720" to .750" (refer to Brownells available BB reamers),there may or may not be any real change is patterns and recoil, and the question still arises....is it worth is? I prefer just to polish out the existing barrels.
Best Regards, James
 

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Discussion Starter #7
James and Virginian: I have opted to hone out the bore. Yesterday I ordered the flex hone kit from Brownell's. Since I work on other barrels, this kit will be a welcome addition to my gun tools. I will keep everyone posted on the results,which should be within a week or so.......Now, as to the "scarring", I am beginning to wonder if I have a little "egg on the face"......LOL. This could very well be plastic. Here is what I did as far as cleaning: I scrubbed the bore, using a bore brush covered with 0000 steel wool and Shooters Choice "Shotgun and Choke Tube Cleaner. Then I mopped the bore dry. I repeated this procedure several times. Then I dampened the bore with the same cleaner and applied JB with a cloth covered mop. Then I put a buffing cloth over a clean 10 mop and ran it back and forth with my electric drill. I did this two times. Most of the bore was mirror bright except for the trouble area. I can see that what I thought was scarring, could very well be melted plastic. Hence; the "egg on face" syndrome.......LOL.....Virginian: I will scrub with acetone and give you an honest answer...........Even if it hurts......LOL. James and Virginian: FYI....... The bore diameter of this barrel is .733. I want to thank each of you for your input so far. I love to learn.      RR
 

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Interesting discussion.  What I was disagreeing with was that I have not experienced the gas seals blowing in barrels up to .740".  I must also point out that most of what I did was like circa 1986, and I sold all my backbored guns when steel shot became the law.  Lack of foresight, say what?
They may have changed the wad composition and/or dimensions.  Back then I did not see much variation in barrel diameters either, and I was dealing with Remington barrels exclusively.
I was into long range waterfowl magnum loads and tried everything I could think of.  I actually got better than 90% patterns before I was through.  As to bore choke relationships, I agree completely, and remember once I got a 19% improvement with .003" change in constriction, with a backbored barrel.  The new Hevi-shot and tungsten-iron and tungsten-polymer shot seems to pattern even better than the old nickel plated shot out of a stock barrel with short forcing cones and no backboring.
I just picked up an old Garcia SxS 12 that fits me well and I killed some ducks with it pretty good and I think I'm going to lengthen the forcing cones on that sucker before it damages my shoulder.
Let us know how things turn out, and good luck.
 

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Discussion Starter #9
Virginian: I picked up some acetone today, and scrubbed the bore of this barrel. Here comes the truth.........drum roll.........It was not plastic. Whew!....LOL. Fortunately, the flex hone kit has arrived, and I plan to hone the bore later this evening. I will keep you posted.... On the forcing cone issue, as we all know, there are different schools of thought on whether or not this is a performance enhancing modification. I am one of those who find cone lengthening or angle relieving (as it really is) to be a good thing. This is because I have achieved better pattern performance on every barrel (too many lol) I own. Also, regardless of pattern, you get less recoil, and less recoil = better shooting. I had better get off my soapbox now, as I don't wish to start a tiff.....LOL. My main usage of pattern density is for turkey hunting. Will add more later on......"RR"
 

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I thought we were all saying about the same thing.
I also think a long forcing cone is best. I was just passing on some info why shotguns from Europe have short forcing cones for the nitro cards is use over there.
You may want to drop down and read the Tech Note on special long range turkey loads.
As for blown OP wads....I am somewhat at loss on why there seems more problems nowdays? It could be the makers are using more regrind to keep prices down?The best OP wad I have found for regular and BB barrels is the Ballistic Products X12X.
I also think the introductopn of wads for steel shot has given us some great wads for other shot. Due to the dangers with steel, I have found these wads to be the best plastic going.
Best Regards, James
 

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Discussion Starter #11
James: Sorry for the delay, as I have been out of town for the last 2 days. So far, I have honed the bore with the medium / coarse honer, and used the chamber and cone honer, which did reach into the trouble area. I just made the first pass with the "fine" honer, and the scarred area is now beginning to show signs of much improvement. The forcing cone itself, is vastly improved along with the main bore where it was not scarred. I did read your post concerning high performance turkey loads, and I am very interested in your progress. I too, use the BP wads and gas seal. So far, I haven't found any other wad that performs as well as these. Pretty much the same as you, I use the motor mica on my wads. I also am using Blue Dot powder, and I vibrate my buffer material into the shot column. This particular barrel gets about 78% with these loads at 40 yards. I am eager to see how it shoots after honing. As a final step after honing, I plan to polish with JB or Flitz. I will let you know the pattern percentage after test firing...... Oh, by the way, my tiff comment, I was just kidding. Thanks for the help, I do appreciate it.   "RR"
 

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Discussion Starter #12
James and Virginian: Our weather was good here today, offering me an oppurtunity to pattern the honed barrel. I shot 10 test patterns at 40 yards using the standard 30" circle. I spent the rest of the day counting shot holes......LOL. I used #4 shot (buffered) in a BP listed load. The previous average for this barrel was 78%. It now throws a solid 86%, for an 8% gain.The scarred area is all but gone, but slightly discernable in some areas. I am still at a loss to understand how this barrel became scarred. I wonder if a reamer got loose in there during the cone work?<!--emo&???--><img src="http://beartoothbullets.com/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'><!--endemo--> And yet, I surely would have noticed that at the time, which was over 12 years ago. Thanks for all the help and suggestions..........."RR"
 
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