How important is deburring and chamfering?

[_Raining]

I was being forgetful and did not deburr or chamfer any of my loads (100 pieces). By the time I realized I was shaving copper off the jacket I had already dumped powder in each case. I was being lazy and figured it probably wont make a difference. After seating 50 bullets I decided too much copper was being removed and inside neck chamfered the other 50 loaded cases.

10 each of 32.2, 32.4, 32.6, 32.8 and 33 grains of Varget in 6 Dasher were seated without inside neck chamfer. The other 50 (31.2 to 32) had been chamfered, I figured getting some brass shavings in the case was still better then shaving pieces of the jacket off. The bullets seated a lot easier. Also the groups for the 31.2 to 32 grain loads were much better than the 32.2 to 33 loads.

Possible reasons:
1. Shooter fatigue.
2. Wind started going nuts (I can't read wind well but this didn't seem like the case).
3. The rifle just doesn't like 32.2 to 33 (I find this unlikely as most of the posts I gathered info from had the chosen load in this range).
4. Chamfering the inside case neck. This is the most likely reason in my eyes because the good groups line up perfectly with the chamfered cases.

I normally don't forget to do this step so I have never seen the effects of it.

So, has anyone done any testing to see just how badly groups can get with little pieces of the copper jacket shaved off? If so, was it like 10% worse or 150% worse?

Or is it one of those things people are told to do and have never tried shooting groups without doing it.

Here is the info from the trip: https://imgur.com/a/mAxqOE8 . I did some ladder tests at 300 and 600 yards but seeing as how the 32.2 to 33 grain loads were erratic, the info is not valid for those. (I know you guys hate it when people do load dev without wind flags but you can't go down range at this place so that is never going to happen. They do have wind flags high up at the 200, 300 and 600 yard line, I am not sure if that is sufficient).

 

[RegionRat]

I found it not only showed up on the seating force, but on the chronograph and target as well.
I told myself some day I would do a controlled test, but have yet to run it. Without a doubt, it made a difference that day, but like your instance it was a known regret while I was in a hurry to get some range work done and I didn’t have enough processed brass. I reached for some brand new cases that had a poor ID chamfer and didn’t have the time to stop that day. I knew those rounds would only be marginal the minute I started to seat bullets and could feel the difference in seating force.

 

[LA50SHOOTER]

It has a bigger influence than some will suspect. - I pay close attention and try to do both as uniform and correctly as possible.

 

[Bart B.]

Make the inside case mouth edge a small radius as follows checking after each step with a magnifying glass to see progress the first few times to get the feel of the task:

1. After trimming to case length, debur inside edge a little with a standard tool.

2. Then twist an Easy Out screw extractor clockwise to debur the inner ridge.

3. Finally push the case neck onto then off a bronze bore brush spinning in an electric drill.

The inside edge now has a smooth radius to glide easily over bullet jackets without peeling off copper. Repeat after trimming case back a few thousandths.

 

[Ledd Slinger]

I use the KM chamfer tool.

From the KM website:

Several years ago Bob Pease wrote in an article,
“For years I have refused to use any of the conventional deburring tools on the market. The taper is far too abrupt to prepare the case mouth for the bullet to enter smoothly. This is a very critical point in the assembly of accurate cartridges. I once saw a big gun shooter pinch the nose of a hollow point bullet completely flat with a pair of pliers. It went right into his excellent ten shot group. Next he took a pocket knife and put a scratch on the heel of a bullet so small it could hardly be seen. That bullet went out of the group by over ½ inch. Later I demonstrated this on numerous occasions to other new shooters. One cannot emphasis enough the need for complete protection of the bullet heel and base.”

 

[Bill K]

Don't know how much it effects FPS, etc. as I never checked that with or without neck chamfering.
But I know, for sure, if you are seating flat base bullets it will shave and make them harder to line up properly in the neck, so that in it's self would effect accuracy, I believe.

 

[Dusty Stevens]

The k&m vld tool with the stop on it works real well

 

[Rsadams]

It's to easy not to do knowing there's bad effects if you don't... Cutting corners defeats the purpose of handloads....

 

[cw308]

I not only chamfer inside and out but polish up the necks with 0000 steel wool wrapped around a smaller cleaning brush , also dip the base of the bullet in Redding Imperial dry neck lube . Makes seating as smooth as silk .

 

[Iowa Fox]

Even after you chamfer in and out look at the mouth with a 12x Loupe. Rough as heck. I use a Varmint Al home made case spinner with 0000 steel wool. Now look at it with a 12x Loupe. Remember what the old guys said about scratches on the heel.

 

[jimmymac]

K&M tool. Consistent results.

 

[Fast14riot]

I use the KM chamfer tool.

From the KM website:

Several years ago Bob Pease wrote in an article,
“For years I have refused to use any of the conventional deburring tools on the market. The taper is far too abrupt to prepare the case mouth for the bullet to enter smoothly. This is a very critical point in the assembly of accurate cartridges. I once saw a big gun shooter pinch the nose of a hollow point bullet completely flat with a pair of pliers. It went right into his excellent ten shot group. Next he took a pocket knife and put a scratch on the heel of a bullet so small it could hardly be seen. That bullet went out of the group by over ½ inch. Later I demonstrated this on numerous occasions to other new shooters. One cannot emphasis enough the need for complete protection of the bullet heel and base.”

I'm not up on all the physics of it, but when I was working missile projects the trailing edge of the fins influenced the direction of rotation during super sonic flight and leading edge during sub sonic flight. Both were chisel edges.

 

[LA50SHOOTER]

Burnishing to a Smooth Finish After Deburring is also Important. - A magnifying glass or "hoop" are your friend !!

 

[Dusty Stevens]

Burnishing to a Smooth Finish After Deburring is also Important. - A magnifying glass or "hoop" are your friend !!

Loupe i think is what you meant

 

[LA50SHOOTER]

Loupe i think is what you meant

Yes !! - Thanks Dusty, - I just use the Brownell's Magnifier headgear & it has the "Loupe" on the side along with the magnifiers built in to the headgear.

 

[dogdude]

Trim, Deburr with the Wilson C/D tool.. chamfer first with the Wilson, then the K&M set @ correct depth..its much easier for a guy with Really bad hands....then to the power drill with brush wrapped w/oooo steel wool for the Smooth finish.

 

[Mad_Charlie]

Make the inside case mouth edge a small radius as follows checking after each step with a magnifying glass to see progress the first few times to get the feel of the task:

1. After trimming to case length, debur inside edge a little with a standard tool.

2. Then twist an Easy Out screw extractor clockwise to debur the inner ridge.

3. Finally push the case neck onto then off a bronze bore brush spinning in an electric drill.

The inside edge now has a smooth radius to glide easily over bullet jackets without peeling off copper. Repeat after trimming case back a few thousandths.

I have used this procedure since the early '80s, it works, however I also found that some kind of inside neck lube was necessary to prevent galling when seating. I used motor mica for some years and then dry graphite. I still use dry graphite when cases are very clean because seating pressure feels very consistent. I am now going to try a fine (800 grit) flex hone that fits the case necks to get a consistent finish. just ordered it today as a matter of fact. Will see how it works. I also intend to make a custom expander mandrel with an "M" step and follow with a light taper crimp after seating to close the case mouth back down. All "just because I want to see how it comes out".

 

[BartsBullets]

Trim, de-burr, and chamfer with a Girard case trimmer in one step. I can do about 100 cases in 10 minutes or so. Expensive but a thing of beauty. I real time saver and it does each case the same.

Bart

 

[Straightshooter1]

Trim, de-burr, and chamfer with a Girard case trimmer in one step. I can do about 100 cases in 10 minutes or so. Expensive but a thing of beauty. I real time saver and it does each case the same.

Bart

Expensive only if it's the bench Power Trimmer and only have one or two calibers. I use the Tri-Way Trimmer and it does like you say in saving time and produces very uniform case results . . . .

. . . as long as one has uniform shoulder measurements.

 

[BartsBullets]

Expensive only if it's the bench Power Trimmer and only have one or two calibers. I use the Tri-Way Trimmer and it does like you say in saving time and produces very uniform case results . . . .

. . . as long as one has uniform shoulder measurements.

I’ve got two bench models. I don’t think he had the Try-Way Timmer when I bought them but yes that would be a great way to go!

Bart