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Discussion Starter #1
Just got a new EMF/Pietta GWII 45 Colt,the Gunfighter with a 4 /3/4 inch barrel.

The Barrel is slugs about .451

The cylinder throats .450
.450
.452
.453
.453
.452
I am Planning on using a 225 Grain Lead Semi Wadcutter at about 6-7 Brinell Hardness and with about 9 grains of unique for a velocity of 950-1000 FPS.

I had originally thought about using .452 Bullets but dont know if the bullets shot through the .450 throats will bump up slightly in the bore for good accuracy.

Would you use the .452 bullets ,or buy .453 bullets or .454 bullets ?

Or would you open up the throats of the .450 throats to .453 and use the .454 inch bullets ?

I have some experience in opening up cylinder throats Using Veral Smiths Method of Slitting a piece of cold rolled steel and putting emery paper in the slit and spinning it in a drill until the bullet of choice would just push through the throat with light finger pressure.

Years and Years ago I did that to a Ruger Blackhawk Stainless 44 Magnum along with firelapping the Constriction from the barrel where the Barrel screws into the frame,Using Water Dropped wheel weights that I dropped from a LBT 280 Gr WFN Plain Base Mold.cut for my barrel. I set this up for Deer hunting
On a good day I could get 3 inch or less 3 shot groups at 50 yards shooting over the hood of my truck.

Now I have Killed enough deer so don't deer hunt anymore so I have no need for that Kind of accuracy and Instead or water dropped wheel weights (which by the way I found that by and Large they did not Kill nearly as well as an expanding bullet on deer )and now will be using a soft cast bullet.

Now I will be shooting at 25 yards and less and If can get 3 inch accuracy or so at 20 yards I would be fine with that.

What do you think ,Will The gun be capable of that with the Mismatched cylinder throats and .452 inch bullets as is or do I need to order bigger bullets and open up the cylinder throats ?
 

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The Hog Whisperer (Administrator)
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I would buy a reamer. Straight chucking decimal reamers aren't terribly expensive. 0.452" or 29/64" will work fine. Yes, you can do it with the split rod and emery cloth; been there, done that. Reamer will be straighter!
 

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I much prefer lapping to reaming, but strongly suggest you SHOOT the gun before altering it. If it ain't broke, don't fix it.
My practice is to lap to the largest throat and that sets the diameter of the bullet shot. A set of gauge pins are worth a LOT.

Of much more concern in a revolver is : Are the barrel threads square with the standing breech? Base pin? Is the base pin parallel to the bore? Are the chambers reamed square with the bore? Are the chambers 60 deg. apart? Was the ratchet cut in time with the chambers? Locking notches?

It is amazing how far off each of these can be and still have the revolver shoot well.
 

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Elk Whisperer (Super Moderator)
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Plus the split rod and emery will make "eggs" out of the throats. Fire lapping the offending throat(s) is more accurate than "flapping" it as one or both ends are always larger than the middle. The lead end isn't so bad being bigger, but the "off" end (?) not sure it would hurt anything, but. :rolleyes:

The dreaded barrel constriction will also be dealt with as well when fire lapping.

How many shots? The smallest throat in my SBH Hunter took 4 (four) coated with 600 grit paste to get it to "match" the rest using the same .431 cast bullet for the "thumb test".

As an added plus, the barrel is now slicker 'n cow slobbers on a tile floor and refuses to lead even with 429421's at 1300 fps.

A question:

I'm not fully understanding the whole need to shoot two or three different weight bullets out of your wheel guns. I shoot 255's (429421's) and 240 grain XTP's out of my Redhawk and for my shooting they both hit the same point of aim even at different velocities. Shooting say 180's and 240's and having to adjust sights for each one seems, well, silly (no offence) ?

RJ
 

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"Lapping cylinder throats is done with a brass, expanding lap to prevent 'egging', but I FULLY AGREE with one bullet, one gun. If you want to shoot more than one bullet, you need more than one gun.
I shoot nothing but LBT 255 gr. .411 dia in my .41 Mag because that's what I built it to shoot. I'm sure it WOULD shoot others but nothing else has ever been down the barrel.
 

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Discussion Starter #6 (Edited)
Guys apparently I did not explain properly as a couple of yall think I am talking about using different sized bullets !
Lets see If i can reword this better.

The meaning I meant to convey was would you Just use ALL .452 inch Bullets to split the difference between the cylinder throat size differences considering the accuracy I said I would be satisfied with.And considering the Barrel slugs at .451

Or would you use ALL .453 Bullets to split difference between the Cylinder throat size differences Considering the accuracy I said I would be satisfied with.And considering the Barrel slugs at .451

Or would you use ALL .454 Bullets to better fit the .452 Bullet throats and the .453 throats and not be concerned with the two cylinder throats that are .450 and considering the accuracy that I said I would be satisfied with.
And considering the Barrel slugs at .451

Or would you open up the smaller throats to a larger size and if so what size considering the bore size of .451 and the accuracy I said that I would be satisfied with.

I hope that I have better conveyed my questions that I have asked.
Lord Knows I would not use different sized bullets in selected cylinder holes
I have enough hassles without doing something like that !
 

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Customarily, the five smaller throats are lapped to the largest throat diameter and that diameter bullet is loaded and shot. First you have to determine what throat is the largest and how much larger it is than the others. Slugging is needed, but you need a good micrometer first. Direct read in .001 and vernier in tenths of thousandths. .0001. Calipers aren't accurate enough.
 

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Discussion Starter #8
"Lapping cylinder throats is done with a brass, expanding lap to prevent 'egging', but I FULLY AGREE with one bullet, one gun. If you want to shoot more than one bullet, you need more than one gun.
I shoot nothing but LBT 255 gr. .411 dia in my .41 Mag because that's what I built it to shoot. I'm sure it WOULD shoot others but nothing else has ever been down the barrel.
I have never use a Brass expanding Lap

What is the process for using a Brass expanding lap to open up the cylinder throats?

Where can I Buy a Brass expanding Lap to open up the cylinder throats ?

What is the cost for a brass expanding lap to open up the cylinder throats ?
 

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Discussion Starter #9 (Edited)
Customarily, the five smaller throats are lapped to the largest throat diameter and that diameter bullet is loaded and shot. First you have to determine what throat is the largest and how much larger it is than the others. Slugging is needed, but you need a good micrometer first. Direct read in .001 and vernier in tenths of thousandths. .0001. Calipers aren't accurate enough.
I have a couple of micrometers(think one of them is an old Mauser) although I used Calipers to do the measuring.
I will go back and use a micrometer to take the measurements.

When I opened up the throats on the Stainless Ruger Blackhawk I used a bullet From the mold I got from Veral Smith and dropped through each hole until it would just push through the throat on all the throats with slight finger pressure.
 

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Brass expanding laps are made in two styles: Through hole and blind hole. They expand about 10 to 15% over nominal size. Sometimes a lap has to be ground down to size on a centered grinder for gunsmith applications.
Here's the one I have for .41 cal.
https://www.mscdirect.com/product/details/05060264

The lap is a carrier for the abrasive. Common "Clover Brand" valve grinding paste in 320 grit is loaded onto the lap and fed through the FRONT end of the cylinder so the chamber is not touched by the lap. Thru hole laps have a slight bulge to them so they'll start in a hole and then lap out a bit as it goes back and forth, rolling the abrasive pasted between the brass and steel.
Adjust the lap to just drag in the throat, then a quarter turn of the swell screw. Use a LOT of light oil and about 100 rpm. Hold the cylinder by hand so the lap is self-centering. Feed the lap faster than you would a drill bit in wood and oscillate up and down until the lap no longer drags in the hole. You'll only take about .0003 per adjustment of the lap.
Brush and wash and then wipe ALL the grit out of at off of the cylinder and check the throat with a bullet or pin gauge. You want a slurp fit.

The lap should be 'juicy with oil and abrasive and raw brass should not show. It is the abrasive embedded in the brass and tumbling in the oil that does the cutting. If the brass is rubbing on steel, back off and go slower.

Just assuming my .41 Mag. because I remember the figuers--- It was made from a river salvaged .357 BlackHawk. The reamer pilot was .410 so all six chambers were bored to .408-.409 then lapped to .410, chambered to .41 mag and then the throats slugged to find the one largest one. There were three that was .4108 and three between .4105 and .4107. The smaller throats were lapped to .411 and all were polished to .4111 with dowel and 600 Wet or Dry.
Gauge pins only come in .001 sizes and specials are expensive. Look for a set of small hole gauges up to half inch. (ebay is great hunting grounds). Telescoping gauges are not as accurate and harder to use. A small, internal, three anvil micrometer is perfect, but terribly expensive for gunsmith sizes. Ebay #283682506055 is about perfect.....for $700!

You don't HAVE to measure anything if you have a good way to GAUGE and compare. Measuring saves time because you know how much material has to be removed to make it right.

Throats can be enlarged with a split dowel with alum. oxide cloth but it rounds the sharp edge of the throat. A brass lap does not round or 'funnel' a hole.
STAY OUT OF THE CHAMBER with abrasives unless you need to cure a problem.

It's common belief that as reamers wear and become dull they cut undersize chambers. That's not true. Reamers past their prime cut larger holes and many times rougher holes. Look for 'frosting' on new, shiny cases or one chamber that seems sticky in extraction. Many times small errors can be corrected with common tools and processes.
Some revolver cylinders are chambered two chambers at a time or even three at a time in multi-spindle machines, so it's common to see alternating large and small throats.

Measure twice, cut once. You cant put it back. ;)
 

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Discussion Starter #11
Brass expanding laps are made in two styles: Through hole and blind hole. They expand about 10 to 15% over nominal size. Sometimes a lap has to be ground down to size on a centered grinder for gunsmith applications.
Here's the one I have for .41 cal.
https://www.mscdirect.com/product/details/05060264

The lap is a carrier for the abrasive. Common "Clover Brand" valve grinding paste in 320 grit is loaded onto the lap and fed through the FRONT end of the cylinder so the chamber is not touched by the lap. Thru hole laps have a slight bulge to them so they'll start in a hole and then lap out a bit as it goes back and forth, rolling the abrasive pasted between the brass and steel.
Adjust the lap to just drag in the throat, then a quarter turn of the swell screw. Use a LOT of light oil and about 100 rpm. Hold the cylinder by hand so the lap is self-centering. Feed the lap faster than you would a drill bit in wood and oscillate up and down until the lap no longer drags in the hole. You'll only take about .0003 per adjustment of the lap.
Brush and wash and then wipe ALL the grit out of at off of the cylinder and check the throat with a bullet or pin gauge. You want a slurp fit.

The lap should be 'juicy with oil and abrasive and raw brass should not show. It is the abrasive embedded in the brass and tumbling in the oil that does the cutting. If the brass is rubbing on steel, back off and go slower.

Just assuming my .41 Mag. because I remember the figuers--- It was made from a river salvaged .357 BlackHawk. The reamer pilot was .410 so all six chambers were bored to .408-.409 then lapped to .410, chambered to .41 mag and then the throats slugged to find the one largest one. There were three that was .4108 and three between .4105 and .4107. The smaller throats were lapped to .411 and all were polished to .4111 with dowel and 600 Wet or Dry.
Gauge pins only come in .001 sizes and specials are expensive. Look for a set of small hole gauges up to half inch. (ebay is great hunting grounds). Telescoping gauges are not as accurate and harder to use. A small, internal, three anvil micrometer is perfect, but terribly expensive for gunsmith sizes. Ebay #283682506055 is about perfect.....for $700!

You don't HAVE to measure anything if you have a good way to GAUGE and compare. Measuring saves time because you know how much material has to be removed to make it right.

Throats can be enlarged with a split dowel with alum. oxide cloth but it rounds the sharp edge of the throat. A brass lap does not round or 'funnel' a hole.
STAY OUT OF THE CHAMBER with abrasives unless you need to cure a problem.

It's common belief that as reamers wear and become dull they cut undersize chambers. That's not true. Reamers past their prime cut larger holes and many times rougher holes. Look for 'frosting' on new, shiny cases or one chamber that seems sticky in extraction. Many times small errors can be corrected with common tools and processes.
Some revolver cylinders are chambered two chambers at a time or even three at a time in multi-spindle machines, so it's common to see alternating large and small throats.

Measure twice, cut once. You cant put it back. ;)
I will shoot it BEFORE I undergo any Modifications to the gun as I agree with you about not fixing something unless it is broke !

I really appreciate you taking the time to share your knowledge on this subject with me and others reading this thread.

Thank you much
Craig
 
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