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Discussion Starter #1
I understand fire lapping can remove barrel constriction and smooth up the bore for less leading and better accuracy. Can you get the same results by shooting jacketed bullets? Assuming the barrel is the desired size.
 

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eehhhhh, Not sure I'm following exactly what you are after here....

Fire lapping is useful at smoothing tool marks in the bore, but only in the first little ways. Essentially a throat smoothing deal. If your bore was mis-made, that can't be helped by "gritty bullets" Bullets will never fill the bore perfectly, they tend to get the lands, and the center of the grooves.

Yes, jacketed bullets will also wear down any imperfections. One of the reasons that I personally see barrel break-in as a superstition. Best way to cause wear is.....USE!
 

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I'm not sure I know what exactly is wanted, either, but here's some information:

Barrels can be fire-lapped (that means bullets which are impregnated with grit are fired through the gun) with either lead or jacketed bullets. Some purveyors of fire-lapping kits suggest the use of lead bullets only on revolvers or other handguns, whereas they suggest jacketed bullets be used on rifles. Other purveyors suggest the use of lead bullets _only_ for all firearms.

If you've ever heard of the Tubb Final Finish product, those are jacketed bullets that are pre-impregnated with grit. I've used that system and found it completely useless to any good cause.

NECONOS sells either pre-impregnated jacketed bullets, or just technical-grade grit with which you may impregnate your own bullets. I've used this product and found it somewhat useful, but I don't believe that jacketed bullets are a wise choice even in a rifle. Can't say I know for sure, but that's my impression.

Beartooth Bullets sells dead-soft lead bullets and firelapping grit/kits. They say to use only lead bullets no matter what you're fire-lapping. I've used this system before and had very good results.

Impregnating your own bullets with grit is time-consuming and can be frustrating. It takes a bit of a knack to do it successfully. Practice makes ...better. :)

Another option is to have a gunsmith lap the barrel. I don't know whether this is effective on constrictions, or only on rough/fouler barrels. He won't shoot the gun to lap it, he'll make a lead lap and lap it by hand. It shouldn't cost you all that much, either.
 

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Yes you can remove a barrel restriction ( thread choke at the barrel frame interface )
Most times this is caused by a barrel not being timed correctly and has to be over tightened when screwed into the frame. They can run from .001 to .005 in some cases.
The condition can also be caused from roll marks on the barrel, and sight installation.
It is not recommended for the cylinder throats the throats should be reamed.
This is done mostly to shoot lead bulletsfirst you must slug the bore, and establish that yes you have a tight spot, also determine what the barrel measures, if the slug goes through a tite spot the measurement will be off by the amount of constriction.
In any event the throats must be bigger than the barrel grove. If not, get them reamed first. Veral Smith from lead bullet Technologies has one of the best kits available, with good instructions also reasonable $$ And he will speak with you on the phone.
It takes a little time and it's a little messy, but it works. If done correctly the barrel will have a very slight taper from the back to the front ( very good for lead bullets )
Naturally I left out a few thing cause it's just to much to type.
The other method is with a lead lap pulled through the bore many times , also with lapping compound.
 

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dhom, I'm not a supporter of fire lapping. If your barrel has a constriction, send the defective gun back to the factory and have the barrel replaced.
 

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Discussion Starter #6
Thank you for the responses! Yes, I am talking about cast bullet shooting in a 45 Ruger Bisley. Iowegan, I was not aware this was considered a defect. I don't know if I can detect a constriction by slugging the barrel. Do you slug the outgoing end of the barrel, remove the lead, measure, than repeat the process you starting by pushing the slug completely through and measure again?
 

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dhom, The technique used by nearly all revolver manufacturers for keeping a barrel tight in the frame is "crush fit" threads. Unlike a normal bolt and nut, the barrel requires considerable torque to screw it into the frame .... similar to pipe threads. The threads are intentionally cut shallow on the barrel so the frame threads will grip the barrel to keep it from torqueing loose. Barrels are made of much softer material so they will yield to the harder frame.

Constrictions from the above process are located just in front of the forcing cone and can happen in any caliber but are much more common (and more severe) with 45 cal barrels because they have thinner barrel walls.

Excessive thread constrictions are caused by either of two conditions ... the most likely being the threads were cut too shallow on the barrel due to a worn out die. If the barrel was torqued too much in an effort to correct the front sight for top dead center, it could also cause a thread constriction. Both of these conditions are indeed factory defects.

A different type of bore constriction can happen anywhere in the bore (very rare). It is caused when the tool used to cut the rifling "stutters" as it is being driven through the bore. This type of constriction is obvious when you look down the bore and will appear as disruption in the rifling ... again a factory defect. Yes, even "roll marks" can cause constrictions but they are so minor that it won't affect anything.

Slugging a bore is a very poor procedure and will almost always yield false information. Why? Despite lead being very soft, it still has some resilience. This means the "slug" will increase in diameter slightly when pushed out of the bore, which will give you a false measurement. Further, you need a micrometer accurate to .0001" if you expect to get any accuracy at all. A typical dial or digital caliper just won't cut it. Last, you need a way to apply proper pressure to the slug when measuring ... enough to get an accurate reading but not so much pressure where the slug will deform. Precision .010" steel arched shims are used on the bullet to keep the micrometer from "biting" in to the soft lead then the thickness of the shims are subtracted from the measurement.

The best procedure to test for constrictions is to use pin gauges, which are precision diameter steel shafts. As an example, let's say you had a 45 cal revolver. The true bore diameter should be .451" +or- .0005". Considering the rifling lands extend from the bore, the largest diameter pin gauge that will fit would be about .440" ... I say "about" because there will be a slight variation from gun-to-gun. So assuming a "normal" bore, insert a .440" pin gauge in the muzzle. It should slide through a clean bore with minimal friction. If the pin gauge stops before it exits the forcing cone, you have a constriction. By using a cleaning rod with the pin gauge stuck at the restriction, you can measure the depth of insertion and determine exactly where the constriction is, taking the length of the pin gauge into consideration of course. Once you determine the presence of a constriction, you can use progressively smaller pin gauges until you find the diameter that passes through the constricted bore. Subtract the smallest diameter from the largest and you will know the extent of the constriction.

Most people don't have access to pin gauges but there are other telltale signs you can look for. Minor lead bore fouling just past the frame junction is quite normal in all revolvers and is not always an indication of a constriction ... could be tight cylinder throats or a corrupted forcing cone ... or more likely, just a mismatch of bullet hardness versus chamber pressure. If your lead bullets are the proper hardness and match chamber pressure, cylinder throats are the proper diameter, and the forcing cone is in good shape, yet fouling in the bore extends from the forcing cone to the muzzle, then you very likely have a bore constriction issue that needs to be addressed. If you are not getting lead fouling all the way to the muzzle, then an excessive constriction is not the problem.

Virtually all revolver barrels mounted with crush fit threads will have a thousandth or two of constriction ... no big deal ... quite normal and it has minimal effect on accuracy or fouling, especially with jacketed bullets. With lead bullets, anything over a .002" constriction will start causing problems with bore fouling, which in turn affects accuracy. What does a constriction do? Simply, it sizes down the diameter of the bullet. With lead bullets, this may mean the bullet will lose the seal between the bullet and bore, thus allowing very hot pressure to vent past the bullet (blow by). When blow by happens, the circumference of the bullet is eroded (melted) and turned into lead vapor. Some of the lead vapor remains in the bore, hardens, and turns into lead fouling. The more rounds fired, the more fouling will build up and result in progressively worse accuracy. Jacketed bullets don't behave this way ... in fact they don't seal well to begin with so it would take a considerable constriction to affect accuracy.

What can you do about constrictions? Depending on severity, the best solution is to fire a couple boxes of jacketed ammo. This will "iron out" striation marks in the bore and will usually remove enough thread constriction where it won't be a problem. You could fire several thousand rounds of lead bullets and never affect constrictions. In severe cases (.003" or more) the best solution is to have a new barrel installed. If constrictions are .002" or less, selecting the proper hardness bullet to match chamber pressure will work quite well. When the bullet is sized down slightly then passes the constriction, pressure will again force the bullet to expand (obturate) and reestablish a good seal between the bullet and bore. This process is detailed in a document I posted in the Forum Library called "Lead Bullets and Revolvers". Click on this link: http://rugerforum.net/library/19869-lead-bullets-revolvers.html

Fire lapping will indeed remove thread constrictions but at the same time, the rest of the bore gets lapped too. If constrictions are bad enough where fire lapping is being considered, by the time you shoot enough fire lapping bullets to remove them, the rest of the bore will have rounded edges on the rifling and will have been worn more than if thousands of rounds of jacketed bullet had been fired. In other words, the bore wears out. For this reason, I discourage fire lapping.

Several years ago, a process called "Taylor Throat Reaming" was very popular. This technique uses a long 10 degree forcing cone reamer that cuts a deep throat in the barrel ... deep enough where it goes past the frame's threaded area. When a barrel throat is reamed with a Taylor Throat Reamer, it totally removes any thread constriction. Accuracy is vastly improved and lead bore fouling is almost non-existent. Brownell's used to sell these reamers but they have since discontinued them. I still have one for a 45 cal and have used it many times on Ruger BHs with great success. Of course "there's no such thing as a free lunch" and the Taylor system is no exception because about 5% of the muzzle velocity is lost. IMO, this is a small price to pay for otherwise exceptional results. Most good gunsmiths that have been in business for many years will probably have Taylor Throat Reamers. If you insist on repairing a revolver with excessive thread constrictions versus returning the gun, this is by far the best solution. It does not harm the rest of the bore but it is a somewhat radical modification so many people are afraid of it.
 

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Iowegan, thank you for the textbook article on barrel constrictions. With trepidation, I just ordered a Ruger stainless Super Blackhawk Bisley 5.5" in 45 Colt, due to the overwhelming influence of my brother, who loves his gun of the same model and caliber. He warned me that I would likely need to deal with the barrel and cylinder constriction issues, but said that, with some gunsmithing, I could have an accurate 45 Colt for far less than the cost of a Freedom Arms 97/83. Up until I read your post, barrel constriction was somewhat of a mystery. Now I realize it's all about the manufacturing tolerances. You have to pay for tighter tolerances. Hoping and praying for a gun with good dimensions!
 

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I also thought that Iowegan post was extremely helpful. So helpful, in fact, that I used a recently acquired pin gauge set to measure the bore of my .44 Mag Blackhawk. The 0.417 pin fit snugly and the resistance through the barrel was essentially uniform from muzzle to forcing cone and the 0.418 would not fit at all. So I conclude that I have no constriction - and that I just wasted $75 on a lapping kit that I ordered a few days ago. Too bad I did not find this post last week. Nevertheless this post enabled me to authoritatively conclude that two of my revolvers which I suspected of having a bore constriction in fact do not and the source of their respective lack of precision results from some other cause.

So, Iowegan, thanks for the information and education.
 

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BLFields, Loading lead bullets is quite an art. With jacketed bullets, you just pick a load from a reputable reloading manual and you're good to go. With lead bullets, assuming you want good accuracy and minimal bore fouling, you must select the bullet hardness that matches your chamber pressure and the bullet diameter that matches your bore. Further, your cylinder throats must be sized about .001" larger than bore diameter and your forcing cone needs to be chamfered to 11 degrees. If all these parameters are met, there's no reason why lead bullets can't be accurate. I'd take it a step further and say .... lead bullets will display superior accuracy over jacketed bullets.

The Forum Library article I referenced in the above post: http://rugerforum.net/library/19869-lead-bullets-revolvers.html has detailed information on how to match chamber pressure to bullet hardness. Yes, it really works ... first time and every time. Bullet hardness alone doesn't fix the problem but when the cylinder throats and forcing cone is right, it's amazing how accurate you can get .... and a box of ammo later, it's still accurate.
 

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Thank you for the link to the article. Since I am new here, I apparently do not have the requisite credentials to access that article just yet. I'm not entirely sure what credentials I need, but whatever they are I don't have them.

Regarding the cylinder throats, four are 0.430+, and two are 0.431+. At this point I don't know the actual bore size, only that the land diameter is 0.417. The only way I know of to ascertain groove depth is to slug the barrel which I plan to do later on this week. If the barrel slugs at 0.429, that will leave two chambers slightly over-sized. I don't believe that this condition alone is the source of inaccuracy in this revolver. I do think that your idea of investigating cast bullet hardness is the next area to explore and hopefully this experimentation will lead to a solution.

Based upon another detailed post you published concerning the use of Lil Gun powder, I bought some 300 gr. bullets and plan to do some testing probably next week. This is just to satisfy my curiosity; nothing I plan to do with this revolver will ever need a 300 gr. bullet to do it.

Thanks again for the pointers. I am sure that eventually this handgun is going to shoot as it should.
 

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Fire lapping is for sure a hot button topic.
All I can relate is my personal experience and results.
I have fire lapped over 10 (maybe 15) single action Rugers . Each has had a fairly extensive fire lapping session with stainless requiring more rounds of coarse grit than blue.
More often than not you can see the groups tighten as you are in progress.
When completed ALL have much reduced leading and what is left cleans very easy. Most (not all) shoot a tighter group , but none shoot worse than before fire lapping.
As mentioned , fire lapping is not the first step , that is chamber mouth. Your cast bullet should be a snug ,slight friction fit and push thru with finger pressure. Fix the chamber mouth first and you will find the older 45 caliber Blackhawks are the worst offenders for tight mouths.
I don't so much measure a slugged bore as feel it as I slug it. You can feel several slow spots as you push it thru . Often Ruger single actions have so much thread constriction
you can leave lead deposits just slugging the bore.
Ruger does NOT consider thread choke to be out of speck and will not change a barrel for that . It has been tried many times.

All this works well for me but,,,,,You must decide if it is the right course of action for you .
 

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needsmostuff, You're on the right track but your terminology is confusing. When I first read you response I had to do some interpreting. What you are calling the "chamber mouth" is really the chamber's "throat". Throats need to be large enough where you can easily push a lead bullet through nose first into the front of the throat. The word "mouth" is normally use when referring to the entrance of the barrel .... ie forcing cone.

BLFields, The Forum Library requires 10 or more posts (promotion to PFC) before you can access it. It has all sorts of stuff that I'm sure you will find interesting. As for your 44 cal throats .... try the recommended approach and attempt to push your lead bullets through the throats. It is not unusual for all six to be a slightly different size. If any are too tight, it's best to ream all 6 so they will at least be the same diameter.

Just my opinion but 300gr bullets are WAY over weight for a 44 cal. Your best results will be with 240~250gr.
 

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...I am sure that eventually this handgun is going to shoot as it should.
So now you've put it out there: you have an 'inaccurate' .44 Mag Blackhawk. Sharing all the details of this would aid the forum members in helping you to solve the issues you are having with the gun.
 
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