Has anyone documented the SD of flash hole debured ammo vs not deburred?

[dcmdon]

Hi all,

Over the next week I'll be loading up 400 rounds of .308 for my trip to Sig for their precision long range rifle class. I've got a load that works well, although I'm sure it could be improved.

UPS tracking shows that by this time tomorrow I'll have a flash hole deburring tool in my greedy hands. So my question is this, has anyone measured the muzzle velocity standard deviation of ammo made with deburred brass vs exactly the same ammo made with brass that was not deburred?

I'm curious if there is any real evidence that this helps.

Don

p.s. I'm hoping Eddie Coyle sees this.

 

[highscore]

Haven't documented this but for the time it takes, having to do it only once per case, it makes me feel good and confident in my loads. Not that I usually extracted the kind of precision I'd like to see but I watched my loads shoot 24 straight x's out of a Palma rifle using 155's at 1000 yards. It just makes sense that the flame will be more consistent directed through a burr free hole. Measurable, who cares. A lower SD does not necessarily mean tighter groups, looks good on paper but... Don't know what your tool is but make sure you don't open up the holes. Just clean off the burr.

 

[dcmdon]

I ended up with an RCBS. It has a stop so that i don't open up the hole.

I feel the same way that you do. For the time it takes, why not. I was just curious if anyone had documented anything.

I'm taking a class at sig in a couple of weeks. We'll be shooting out to 1000 yards. I ran some numbers through an external ballistic calculator and realized that a 30 fps variance in muzzle velocity will move the bullet something like 16" at 1000 yards. So I'm sorting brass and using the outliers at the beginning of the course when we are shooting 100 yards when 30 fps in MV is basically irrelevant.

Don

 

[EddieCoyle]

I deburr the flash holes, but I've never done a chrono comparison.

 

[Steve Marshall]

You'd have to have a huge population of data to prove anything given the normal variation. Suffice it to say the benchresters do it as a matter of course. They do it with the anticipation of reducing group size at 100 yards.

 

[noylj]

>Haven't documented this but for the time it takes, having to do it only once per case, it makes me feel good and confident in my loads.

This is the ONLY reason to do. A shooter needs to have confidence.
The assumption being "it can't hurt." However, nobody seems to ever test this and find out if it really "can't hurt."
If one needs to shave off 0.01" from the group size, then these bench rest "tricks" may have a place. If you need a reduction in the 0.1" range, that comes from the load, the rifle, and the shooter and not case tricks.
I am more than happy with 0.75" 100 yard groups with my Ruger .30-06 and doubt the rifle or I could do better no matter what is done to the case. So far, I haven't got my AR to below 1.5".