Case mouth deburring.

Had a friend visiting my shop, looking for information on the RCBS MatchMaster . While chatting about programming changes that are available on the device, I was getting some new brass ready to enter the system. Using a tool, I was deburring the case mouths inside and out before running them over an expander mandrel. My friend thought both the deburring and mandrel were not needed and that he had never done either after 30 years of reloading even on cases he had trimmed. His comment was the expander ball in the sizing die took care of both. No way. I showed him the difference, while bullet seating, using the different methods. He could feel the consistency of the properly prepped brass over the way he had done it for years. Ah yes, another convert. Neck tension is very important if you are looking to get precision from you loading. I love my Giraud trimmer and it has become part of brass prep during every loading. The Giraud in addition to trimming takes care of case mouth prep during the same action. Whatta Hobby!

NFIE,

Couldn't agree with you more.
I have found over years of reloading - 60,000 rounds - that deburring inside and outside of my cases eliminates a lot of variance in the cases when loading bullets and makes the brass much smoother as the bullet is seated.
Not being able to use the same pressure on every bullet really causes variations in cartridge base to ogive measurements.
When the cases are deburred, my rounds are all +/- 0.001 inch or better across 25 rounds. (I generally load 25 rounds for each different load that I shoot.)
Without deburring, that different by about 3 times that.

Same. I deburr case mouth inside/out, clean & Swage primer pockets, & primer ignition hole and even deburr pockets if needed. Brass prep is everything.

Have always done it. I don’t look forward to doing it when prepping in bulk(just did 900+pcs in last few weeks!), but just know it has to be done…..especially after trimming.

I use a Redding internal deburring tool that can be set to depth off the cartridge vent. I do the first loading and all subsequent reloadings. Outside deburr I do initially on new or first fired brass but don't worry so much about that afterwards. If I trim the brass for any case stretch then I do an outside (and inside) deburring.

After first firing of new brass, everything gets sized then trimmed with the Giraud trimmer which also preps the mouth in the same operation. Cases get annealed often with the Giraud annealer. Whatta Hobby!

The fact that he has been reloading for 30 years and has never done that step shows that it is clearly not "necessary"..... but that's not to say it isn't beneficial.

It also depends on your trimmer- how clean it cuts and the bullet you are using. Some boat tail bullets load fine and upon pulling to inspect them they showed no jacket damage. Other bullets you can feel hanging up and then a little pop as they overcome the resistance (which can't be a good thing). It is a step that I do- but previously didn't- and it's not a night and day difference. Also- in neck tension testing I can not make it be as big of a deal as everyone tells me it is- when isolating only it. But still strive for consistency.

My friend has put a Giraud trimmer on his Christmas list. He thinks next year maybe an annealer. Looks like he is going to add the mandrel stage to his brass prep just be for the priming stage. He admitted that just because he did it one way for 30 years, there are better ways that really don't take that much extra effort. Learning different techniques and practices can be enjoyable.

Pulling a sizing button through their sized cases induces run-out. This is really true on unanealed and unlubricated brass. Pushing a mandrel in from the top seems to have helped my runnout issues. Nicer dies and presses may help also.

One reason why I like my Lee neck size die for the .308.

Quote:

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Originally Posted by Robinhood

Pulling a sizing button through their sized cases induces run-out. This is really true on unanealed and unlubricated brass. Pushing a mandrel in from the top seems to have helped my runnout issues. Nicer dies and presses may help also.

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That is the ticket. I use a mandrel for most cases. It does indeed reduce runout to a minimum. Whatta Hobby!

Always chamfer, especially after trimming. Though I only use a VLD chamfer tool because I like the less abrupt angle change and I feel like bullets start a bit easier.. The case mouths only usually need to be very softly worked with the chamfer tool to break any hard edge.

Also, I have found two other things in the process really, really help with consistency. The first is annealing. I anneal my "precision rifle" brass after every firing. Also, I use Hornady match grade dies, which utilizes a self centering neck size bushing that helps with concentricity and gives a much more consistent and tunable neck tension (I prefer right at 2thou neck tension for just about everything).