EDM Rifling

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tatume

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Hello Folks,

First post here; looks like a very good forum.

I shoot cast bullets almost exclusively. My only experience with an S&W revolver with EDM rifling resulted in very bad leading. My other S&W revolvers and my Ruger revolvers in the same chambering, do not accumulate any lead at all. I have an extensive collection of sizing dies, and I tailor my cast bullet diameters to the throat diameter of the guns (0.0005 - 0.0010" under throat diameter). My cast bullets are not at fault.

I wish to purchase a new 357 Magnum revolver (6" or 6-1/2" L or N frame), but want to avoid EDM rifling. How can I tell which models use EDM rifled barrels?

Thanks, Tom
 
It's not EDM (electro-discharge machining) it is ECM (electro-chemical maching). If you search these forums you find much info on this topic. I'm of the school that the leading problem is not an ECM issue. ECM actually leaves the bore smoother than conventional rifling - so much so that the FBI was concerned that it might not leave distinctive identifying marks on bullets - not true, but smoother than button rifling.

Supposedly regular production and Pro guns are ECM rifled. Guns from the PC are button rifled. Not sure if that still holds true.

Adios,

Pizza Bob
 
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I believe my much beloved 696 has ECM rifling. I got leading in the barrel with every kind of plain lead bullet I tried. I have since gone to copper plated lead bullets. That solved the leading problem.
 
tatume said:
I shoot cast bullets almost exclusively. My only experience with an S&W revolver with EDM rifling resulted in very bad leading.

Thanks, Tom
Click to expand...

I shoot cast bullets almost exclusively. My experience with 3 ECM rifled 44 caliber revolvers is no significant leading.
Hot loads use Penn Bullets premium alloy (BHN 20). Throats on S&W revolvers are generally on spec in my experience. For example, my 44s measure like 4295 so I order 430 bullets.
 
First, size your bullets throat diameter to .002 over throat diameter, not under. This will not cause pressure problems even with maximum loads.


Second, drive a soft lead slug through the barrel and try it in the cylinder throats. If it will pass through all throats with little or no pressure all is good. If it will not the barrel groove diameter is larger than the throats then you have a problem! No matter what you do you will get leading because the bullets will be sized smaller than groove diameter when passing through the throats. The throats will have to be reamed or lapped to larger than groove diameter or resign yourself to shooting jacketed or plated bullets.


I have no idea how experienced you are with shooting lead bullets, but no matter what if the bullet is undersize, either by initial sizing or tight throats in a revolver, you will get leading. Most cast bullets are too hard too which also contributes to leading. Bullet fit and lubricant are the secrets to successful use of cast bullets! Unfortunately it is extremely rare to get truly good results if you are buying commercial bullets instead of casting yourself! They are usually under-size, too hard, and have worthless lubricant that is intended to be pretty and ship well rather than be an efficient lube!
 
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Alk8944 said:
First, size your bullets throat diameter to .002 over throat diameter, not under. This will not cause pressure problems even with maximum loads.


Second, drive a soft lead slug through the barrel and try it in the cylinder throats. If it will pass through all throats with little or no pressure all is good. If it will not the barrel groove diameter is larger than the throats then you have a problem! No matter what you do you will get leading because the bullets will be sized smaller than groove diameter when passing through the throats. The throats will have to be reamed or lapped to larger than groove diameter or resign yourself to shooting jacketed or plated bullets.


I have no idea how experienced you are with shooting lead bullets, but no matter what if the bullet is undersize, either by initial sizing or tight throats in a revolver, you will get leading. Most cast bullets are too hard too which also contributes to leading. Bullet fit and lubricant are the secrets to successful use of cast bullets! Unfortunately it is extremely rare to get truly good results if you are buying commercial bullets instead of casting yourself! They are usually under-size, too hard, and have worthless lubricant that is intended to be pretty and ship well rather than be an efficient lube!
Click to expand...

Kinda hard to size .002'' over throat in lots of instances.. Ex.. in

44cal the largest sizing die is .431''.... Same goes with bullet

moulds... Custom moulds are Pricey.. Same goes for sizers..


0lder 29s and 629s suffered from BIG throats.. Fortunately the 29s and 629s of the past 25 yrs don't

seem to have the oversize throat problems.. l have several 629s l shoot with no leading problems...

l cast/size @.431''.. My alloy is mostly a mixture of wheel weights. l size with a lube called Bens Red.

Best of all, they are SCENTED... My Magnum Hunter has over 12 thousand rds thru it.. Almost all are

home cast from wheel weights.. Were it not for lead bullets l could not afford to shoot... l get a little

leading... Big Deal... That means its time to clean... lf the little bit of lead bothers you, shoot a few

jacketed rds.. No more lead.
 
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sw282 said:
Kinda hard to size .002'' over throat in lots of instances.. Ex.. in 44cal the largest sizing die is .431''.... Same goes with bullet moulds... Custom moulds are Pricey.. Same goes for sizers.
Click to expand...

Size dies in any size you wish are available for the same or less than Star, RCBS or Lyman factory dies. Send me a PM and I'll direct you to the fellow I use. Fantastic quality and fair pricing.

Custom molds can be expensive, but worth every penny. A top notch four cavity mold can be had for $125. It uses standard RCBS two-cavity or Lee six-cavity handles. A Lyman four-cavity mold runs $80+ and uses special handles ($30). Send me a PM and I'll direct you to the mold maker I use. There are others of equal quality.

Revolver cylinder throats should be 0.002" larger than barrel groove diameter. Bullets should be sized to fit the throats snuggly. Bullets 0.0005" under throat diameter are ideal. Sizing bullets over throat diameter is not dangerous, as long as they chamber easily. Oversized bullets do not contribute to accuracy.

Back to my original question, my Model 629 is a PC gun. Now that I know what to look for, I determined that it has conventional rifling. Looking further, I found throats to be 0.429", the same as barrel groove diameter, which is likely the source of the leading problem. The cylinder is on its way to a craftsman of known ability to have throats enlarged uniformly to 0.431". Send me a PM and I'll direct you to the craftsman. He is a specialist who does not have an FFL, so do not send serial-numbered components to him. I have a sizing die that produces 0.4305" diameter bullets. If there is interest, I'll report the shooting results.

.
 
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l have to disagree.. Big throats + Little bore=BIG GROUPS:-(

That's why 25-5s in 45 Long Colt shoot so SORRY.. .455'' throats and

.452'' bores make them shoot Patterns instead of groups.. Problem was

not cured til the old Smith machinery was replaced app 25 years ago..

Lyman Cast Bullet Handbook tells all about sizing for accuracy. Most of

my moulds are Hensley&Gibbs.. No longer made, but still available used.

282
 
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sw282 said:
l have to disagree.. Big throats + Little bore=BIG GROUPS:-( That's why 25-5s in 45 Long Colt shoot so SORRY.. .455'' throats and .452'' bores make them shoot Patterns instead of groups..
Click to expand...

You omitted one tidbit: bullets significantly smaller than the 0.455" throats. Size the bullets correctly and this combination can be made to work.
 
I believe my 686-6 (made in 2004-ish) has the ECM barrel. I shoot mostly lead bullets, including soft swaged (Hornady), I don't have leading problems.

I also shoot swaged bullets in my 625-8 (made in 2008-ish), no leading there either.
 
tatume said:
You omitted one tidbit: bullets significantly smaller than the 0.455" throats. Size the bullets correctly and this combination can be made to work.
Click to expand...

No Sir.. Big throats, Small bores= poor accuracy.

My Model 25 in 45Long Colt shoots sloppy because it has BIG

throats, Small bore. Period. .455'' Bullets it shoots sloppy.

.452'' bullets it still shoots sloppy.. MISMATCHED throats and

bores will ALWAYS shoot sloppy... .452 bullet rattles/bounces

in the .455 throat/cylinder.. Hits .452 barrel off center. Bad

accuracy... .455 bullet in .455 cyl/throat hits .452 barrel nice

and straight, but gets squeezed, swaged, and deformed.. Bad

accuracy again... You will never get good accuracy as long as

the throats and barrel are MISMATCHED in size... PERIOD..
 
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The cylinder of my Model 629 came back from the shop a few days ago. Using a Sunnen hone, the throats were enlarged from 0.4290" to 0.4310". Bullets are sized 0.4305" (custom die) and fit the throats snuggly. What an improvement it made! The leading problem is completely cured, and accuracy is gilt edged.
 
Kernel Crittenden said:
The problem would disappear if you powder coated your lead bullets. Inexpensive and easy to do. So many advantages. I thought most lead bullet shooters adopted this technology years ago.
Click to expand...

Not necessarily. I BADLY leaded a 620 with Bayou Bullets Hi-Tek 158's....

It all comes down to sizing. Against popular belief, size does matter :)

Get the right size slug and doesn't matter what kind of rifling you have....assuming the cylinder throats aren't smaller than the bore.
 
This topic has been covered numerous times before . I have posted that checking the barrel for " tight spots " is just as important and the cylinder throats . I recently bought a set of pin gauges off Amazon for about $100 and found them invaluable . I take a pin gauge that drops in the muzzle and wait to see if I can push it all the way through the barrel . If it stopped short of coming all the way through , then I have a problem that needs fixing . Many many revolvers have a tight spot where the barrel threads onto the frame . When they index the front sight to the rear sight they " over torque " the barrel to get the sights aligned . I have " fire lapped " several barrels and the accuracy improvement was amazing . There are several good articles on the web about fire lapping barrels . The gentlemen at " gunblast " has an excellent article and the owner of Bear Tooth Bullets did an article on a ruger 45 colt , brand new and what he did to correct the cylinder throat size and barrel choke .
S&W 25-5's will shoot very accurately , even with over size throats . I know as I have one . I removed the tight spot in the barrel and cast / size .454 . It is very very accurate . Fire lapping is not difficult , but it does require a bit of effort , patience and understanding on your part. Anyone can fix the cylinder throat size themselves and fire lap a barrel . Again , I refer you to the article from Bear Tooth Bullets to illustrate how he fixed both easily and did not purchase expensive tools , reamers etc . Usually 15-30 rounds will fix the barrel problem . If shooting cast bullets it is definitely worth the effort as the reward is " simply amazing " , accuracy will be phenomenal and barrel leading problem removed , " if you do your part " . Regards, Paul
 
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