Fitting a S&W revolver barrel from a blank?

[wonderwolf]

Looking at fitting a barrel blank to a .38 spl - K frame that is lacking a barrel, Since this is a blank I plan to try several different ideas (milled integral front sight , 5" barrel heavy profile, about like the original heavy 10 but perhaps a touch heavier)

This barrel will only see cast bullets, mostly 158gr SWC's and 148 tin cans etc....In loadings from very mild to +P


The cylinder gap I'm aiming to get around .003"


Where I am hanging up at is how to go about doing the forcing cone from a blank.....how far in and what degree I should go. I'm not sure if I'll make my own forcing cone reamer at this time or not ( I have heat treat capabilities)

Also on the issue of how to handle the ejection rod lockup. it is the snub nose type ejection rod

I can do multiple barrels from the blank I have so if I mess it up it can always be adjusted or just tossed or whatever. But I don't want to waste my material, I've done rifle barrels just never something with this many nuances and need for detail.

[Drm50]

.003” is going to be a PIA. You will be cleaning cylinder face very often, depending on powder used.

[Outpost75]

Pass 0.003 / Hold 0.004 is as tight as I would go with wadcutter. On bull-barreled PPC guns a spring-loaded crane ball lockup is commonly done and works well. Also look at Taylor throating and a barrel twist of 1:14" or faster. Avoid a tight crush fit of the barrel threads in the frame, lest you collapse the barrel extension and induce "thread choke."

Do not go tighter than a UNF-2A thread. Instead of pinning the barrel use a service-removable Loctite such as 242 as a thread sealant to prevent chlorinated paraffins from gun cleaners and lubricants from migrating into the threaded area, which may cause stress corrosion cracking in conditions of high stress, high heat, high torque and high round count.

[dtknowles]

Why not go with the Dan Wesson approach and use a barrel and shroud since you are starting with a blank slate. You could probably use a stock Dan Wesson shroud and barrel nut and wrench. You can find them pretty reasonable. That also means that your cylinder to barrel gap can be set to whatever you want and if you don't like it you can adjust it. You would also then be able to have more than one length barrel.

Tim

[wonderwolf]

Why not go with the Dan Wesson approach and use a barrel and shroud since you are starting with a blank slate. You could probably use a stock Dan Wesson shroud and barrel nut and wrench. You can find them pretty reasonable. That also means that your cylinder to barrel gap can be set to whatever you want and if you don't like it you can adjust it. You would also then be able to have more than one length barrel.

Tim
Blank is ~45 bucks though and this is just a budget blaster project. The gap I think I can set pretty easily if I flub it I can lap a shoulder back.

[wonderwolf]

Pass 0.003 / Hold 0.004 is as tight as I would go with wadcutter. On bull-barreled PPC guns a spring-loaded crane ball lockup is commonly done and works well. Also look at Taylor throating and a barrel twist of 1:14" or faster. Avoid a tight crush fit of the barrel threads in the frame, lest you collapse the barrel extension and induce "thread choke."

Do not go tighter than a UNF-2A thread. Instead of pinning the barrel use a service-removable Loctite such as 242 as a thread sealant to prevent chlorinated paraffins from gun cleaners and lubricants from migrating into the threaded area, which may cause stress corrosion cracking in conditions of high stress, high heat, high torque and high round count.

Good info, thanks! I'll need to see if I can find a spec sheet of the thread/barrel shank are for a start

[dtknowles]

Blank is ~45 bucks though and this is just a budget blaster project. The gap I think I can set pretty easily if I flub it I can lap a shoulder back.

I am guessing that you will be doing your own machining. I wish someone would have answered the part about the forcing cone. I made some of my own barrels for my Dan Wesson revolvers and did not have a reamer for making the forcing cone. I know it is not right but I just lightly put a 45 deg. chamfer on the cylinder end of the barrel and left the muzzle alone. They shoot great with both jacket and cast with no shaving of lead. I used to set the gap at 0.005" with a feeler gage but now I do it by feel. I tighten the barrel until it touches the cylinder and back it off a tiny bit, I dry fire it double action for a full rotation of the cylinder to make sure it is not hanging up. I put the shroud on and tighten the barrel nut and do the double action test again. I am sure my gap is less than 0.005". I don't have problems with it binding as it get dirty but I don't shoot it double action, I always cock the hammer. I guess it could be dragging enough to make the double action trigger pull stiff.

Tim

[Wayne Dobbs]

Also on the issue of how to handle the ejection rod lockup. it is the snub nose type ejection rod.

You can buy a full length ejector rod and center pin and replace the snub length one you have now with something that works much better.

[Outpost75]

Regarding forcing cone angles S&W is generally 18 degrees and Colts and Rugers 11 degrees. An 11 degree reamer is recommended to clean up and remove circumferential tool marks in an existing 18 degree cone, as this can be done without setting back the barrel or enlarging the forcing cone entrance. For PPC revolvers used with wadcutter ammo a 6 degree cone works well. Brownell ' s makes Go/NoGo forcing cone gages, but lacking one of these, the mouth of a new, unfired wadcutter round should just enter the forcing cone entrance, but a fired case should not. This presumes charge hole to bore alignment is correct with no "tickers" felt with a range rod. In a new revolver up to 5 degrees of over-rotation at cylinder lockup may be observed, intended to compensate for wearing in of the lock work parts.

You want the front band of the wadcutter bullet to begin to engage the origin of rifling before the bullet base clears the front face of the cylinder. Use a 1/2" ball mill on L- handle with light touch just to break wire edge of forcing cone after reaming. Using sharp cutter with Brownell ' s Do-Drill, wiping flutes of chips after each cut, by hand, you should be able to produce a 16 micro inch RMS finish and no lapping should be necessary.

[dtknowles]

Regarding forcing cone angles S&W is generally 18 degrees and Colts and Rugers 11 degrees. An 11 degree reamer is recommended to clean up and remove circumferential tool marks in an existing 18 degree cone, as this can be done without setting back the barrel or enlarging the forcing cone entrance. For PPC revolvers used with wadcutter ammo a 6 degree cone works well. Brownell ' s makes Go/NoGo forcing cone gages, but lacking one of these, the mouth of a new, unfired wadcutter round should just enter the forcing cone entrance, but a fired case should not. This presumes charge hole to bore alignment is correct with no "tickers" felt with a range rod. In a new revolver up to 5 degrees of over-rotation at cylinder lockup may be observed, intended to compensate for wearing in of the lock work parts.

You want the front band of the wadcutter bullet to begin to engage the origin of rifling before the bullet base clears the front face of the cylinder. Use a 1/2" ball mill on L- handle with light touch just to break wire edge of forcing cone after reaming. Using sharp cutter with Brownell ' s Do-Drill, wiping flutes of chips after each cut, by hand, you should be able to produce a 16 micro inch RMS finish and no lapping should be necessary.

Thanks for this. Just to get clarity the angles you listed are half angles, like 11 degrees on each side of center like a 45 degree chamfer only 11 degrees or is the 11 degrees the included angle like an 11 degree cone and the taper is 5.5 degrees on each side? You don't mention the depth that we should run the reamer but I guess that is controlled by your measurement of open end of the forcing cone. That makes it sort of a cut a little and measure, repeat until good kind of deal but I would be doing this by hand anyway, if I do, I hate to mess with a barrel that is shooting great.

Tim

[Outpost75]

The angles are the total included angle, not Basic per side. A good base number for the major diameter of the forcing cone entrance is 1.05 times maximum bullet diameter, or .378 for a .38 Special.

[dtknowles]

The angles are the total included angle, not Basic per side. A good base number for the major diameter of the forcing cone entrance is 1.05 times maximum bullet diameter, or .378 for a .38 Special.

Thanks for clearing that up.

Tim

[wonderwolf]

The angles are the total included angle, not Basic per side. A good base number for the major diameter of the forcing cone entrance is 1.05 times maximum bullet diameter, or .378 for a .38 Special.

So would a shop made go/no go gauge be turned to the same taper and a max diameter of .378??

[Outpost75]

So would a shop made go/no go gauge be turned to the same taper and a max diameter of .378??

I would do .375 Go and .380 NoGo shooting for .378 as Mean.

[Cap'n Morgan]

Use the lathe for cutting the forcing cone. Make sure to check the runout with a dial.

[wonderwolf]

Use the lathe for cutting the forcing cone. Make sure to check the runout with a dial.

Single point or reamer?

[wonderwolf]

I would do .375 Go and .380 NoGo shooting for .378 as Mean.

But with the same taper?

[Outpost75]

But with the same taper?

Yes, same included angle as the piloted reamer. I use the revolver tool set from Brownell's.

https://www.brownells.com/gunsmith-tools-supplies/handgun-tools/barrel-tools/chamfering-tools/complete-38-45-chamfering-kit-prod26157.aspx

Here are part numbers for the plug gages: 274044

https://www.brownells.com/gunsmith-tools-supplies/handgun-tools/barrel-tools/chamfering-tools/barrel-chamfering-plug-gauges-prod626.aspx

[Cap'n Morgan]

Single point or reamer?

Single point! A sharp tool bit will do the trick, and you have full control over the cone angle.