Gas Cutting? on boolit base...Acceptable or not?

[BK7saum]

I've been shooting a few 412640s out of a Model 57. They are shooting well with no noticeable leading to the barrel (I've only shot about 50 so far). I recovered one from my berm and the boolit looks like a bevel base. I presume it is from gas cutting, as it is a slightly irregular bevel all the way around the boolit base.

Is this normal? Alloy is 50/50 WW/Pb, air cooled with additional tin added. I'll try to upload a photo of the boolit later this evening.

Thanks. Brad

[35remington]

If they are shooting really well, don't worry about it.

Ignore everything else if they are shooting really well. Investigate further if you think you could or should be doing better.

Gas cutting won't put a bevel on the base. It will look like irregular eroded channels around the periphery of the bullet, often attacking the edges of the grooved portion of the bullet that has been displaced by the rifling, but it can and does erode channels elsewhere as well. Usually the gascutting is worse near the base and below the lube grooves, assuming the lube grooves have been filled with lubricant.

All plainbase lead bullets gas cut to some degree unless a filler is used. If the bullet is shooting well it is considered normal.

[303Guy]

All plainbase lead bullets gas cut to some degree unless a filler is used. If the bullet is shooting well it is considered normal.

Really? Since you mention filler I'm thinking that is for rifle boolits or is that for pistols and revolvers too?

[w5pv]

I use dacron filler in all of my cases from pistol to rifle it helps to get smaller groupings for me.

[Wayne Smith]

If you have no leading I doubt it's gas cutting. That leaves lead deposited on the barrel.

[ourflat]

Agree with Wayne!

[Whitespider]

All plainbase lead bullets gas cut to some degree unless a filler is used.

I'm thinkin' that must be an awful small degree...
I've recovered literally thousands of plain-base boolits from my range, especially in the spring after the snow melts. Other than the rifling engraving, most of them look pristine... and there is no naked-eye visible sign of gas cutting on any of them. (shrug) I've always been of the thinkin' if the boolit fits, and the lube is doing its job, gas cutting will be non-existent.

To the OP...
Without a picture I can only guess... but I believe you are seeing base "erosion" that can happen as the boolit passes from the cylinder mouth into the forcing cone. When the boolit base is in that "unsupported" gap, the corner, or edge, of the base can be blown away by escaping pressure, un-burnt grains of powder, carbon (smoke), ash, flame and whatnot... much like wind and sand will erode a mountain. Typically, if this is what's happening, over time you'll get a build-up of lead on the forcing cone, face of the cylinder, and even the frame.

Base erosion is not "normal"... any time the base of a boolit, or bullet, is damaged before exiting the muzzle, accuracy will suffer. A few different things may cause the erosion... individually or collectively. The common mechanical causes are excessive barrel-to-cylinder gap or excessive cylinder end shake, but a mismatch of alloy-to-load will also cause it. Both gap and end shake are easy to check with a feeler gauge... now understand that there will be varying opinions on this, but gap should be somewhere between .004 and .008, end shake should be something less than .006 (with zero being ideal). If that checks-out OK you may need to lighten-up on the load a bit... or use a bit harder alloy for your .41 boolits.

[44man]

I'm thinkin' that must be an awful small degree...
I've recovered literally thousands of plain-base boolits from my range, especially in the spring after the snow melts. Other than the rifling engraving, most of them look pristine... and there is no naked-eye visible sign of gas cutting on any of them. (shrug) I've always been of the thinkin' if the boolit fits, and the lube is doing its job, gas cutting will be non-existent.

To the OP...
Without a picture I can only guess... but I believe you are seeing base "erosion" that can happen as the boolit passes from the cylinder mouth into the forcing cone. When the boolit base is in that "unsupported" gap, the corner, or edge, of the base can be blown away by escaping pressure, un-burnt grains of powder, carbon (smoke), ash, flame and whatnot... much like wind and sand will erode a mountain. Typically, if this is what's happening, over time you'll get a build-up of lead on the forcing cone, face of the cylinder, and even the frame.

Base erosion is not "normal"... any time the base of a boolit, or bullet, is damaged before exiting the muzzle, accuracy will suffer. A few different things may cause the erosion... individually or collectively. The common mechanical causes are excessive barrel-to-cylinder gap or excessive cylinder end shake, but a mismatch of alloy-to-load will also cause it. Both gap and end shake are easy to check with a feeler gauge... now understand that there will be varying opinions on this, but gap should be somewhere between .004 and .008, end shake should be something less than .006 (with zero being ideal). If that checks-out OK you may need to lighten-up on the load a bit... or use a bit harder alloy for your .41 boolits.

This is good! The alloy for the .41 should be harder as it is a high pressure load. I bet the boolit slumps too.
Can't wait to see pictures.

[BK7saum]

Sorry for not getting back sooner. Daughters softball is taking up my free time.

[BK7saum]

Sorry about the poor cell phone pics. Its all I had at the moment.

Brad

[BK7saum]

I am thinking what I have is base erosion from a too soft alloy for my load. I'll probably go to straight clip-on wheelweight alloy and water drop them.

Would you agree?

Thanks, Brad

[35remington]

Sorry, but I recover a lot of bullets too, and examine a lot of them under modest magnification.

I'll stand by my statement that most are gas cut to some degree. Some gas always passes the bullet.

Bullets can gas cut yet leave a lead free barrel.

This sounds like an educational opportunity forming.

Bottom line is results not gas cutting.

[williamwaco]

Try something for me.

An experiment.

Take a loaded round, pull the bullet, inspect the base.

You need to know where this deformation is happening.


.

[BK7saum]

Williamwaco,

I've pulled multiple dummy rounds to check for sizing down of the boolit by the case. This is definitely happening during firing. I'm sizing these to 0.412" and using a 0.412" custom M die expander. Loaded boolits are as about as perfect as can be.

Brad

[44man]

Make the boolit hard and dump the "M" die, you have no tension. The cutting is happening either while the boolit is still in the brass or it is blowing out the gap.
Your setup sounds like you can seat boolits by hand. In either case the boolit can't leave the muzzle straight.
With a PB in the .41, water dropped WW's are the bare minimum.
I bet you are using a fast powder too.
Dump magnum primers, the primer might be blowing out the loose boolits and then they are hit with full pressure. The .41 case is way too small for a magnum primer.

[BK7saum]

44man,

The boolits have plenty of neck tension. Uncrimped, they are almost impossible to push the boolit deeper into the case. After.expanding I am left with an inside neck diameter of 0.4110-5. I have found that is about the maximum tension one gets anyway. Using the factory belling die of 0.408 wreaks havoc on my boolits due to sizing them during seating. I am using standard LP primers. The powder is unique and is not a top load, but not a mild load either.

[BK7saum]

I am not opposed in turning the m die to a smaller diameter, but I don't think I will gain anything.

I haven't tried this setup with 2400 yet, but plan to soon.

[44man]

Be OK, things you mention sound good enough but the boolit is too soft.

[BK7saum]

Thank you all for your help and input. 44man, thank you for diagnosing and confirming that my alloy is too soft for this application. I have about 16 lbs of these cast, but have the option of sticking a plain base check on them. I may go ahead and do that in order to use these as a hunting alloy/boolit.

Again. Thank you all,

Brad