Flash Hole uniforming

[birdiemc]

I had my borescope in my hand today and for some reason decided to see what the flash holes look like after uniforming. Which led to comparing lots of different cases, then I got these before and after shots. This was done with a Sinclair tool in a once fired .308win FC case.
If anybody else feels like following suit I think it would be interesting to see the pictures/results from different mfr tools.

 

[Savage 12BVSS]

I've never seen close-ups like that but do it faithfully with a lyman tool. I've always felt it made the flame path uniform and hence made ignition more uniform. That's why I lean towards match and benchrest primers, uniformity is a good thing in reloading.

 

[SteelBanger]

Very cool before and after pictures! I bought the lyman tool when I first started hand loading so it's something I've just always done. It only takes a few seconds and you only have to do it once ... worth it to me no matter how big or small the gains may be.

 

[J E Custom]

Depending on the case brand this process can be very important. Some brands are drilled, and some are punched.
The ones that are punched Will/may sometimes have what I call a finger nail on one side that can be very detrimental to proper/consistent ignition.

Thanks for the pictures, they should help those that don't uniform the flash holes as part of their case prep understand the importance of this procedure.

Looks like you did a great job of not over doing it (Cutting down into the case head weakening it). Ignition starts here and everything should be uniform in order to get consistent SD.s

Good post

J E CUSTOM

 

[birdiemc]

Anybody else with a borescope and a flash hole tool?
Like I said this was with the Sinclair tool, I like it because it has the cone that fits into the case mouth, so it's easy to setup to prevent running too deep.
Just interested to see some pics from cases done with different brands of tools to see how the finished products compare

 

[Oddbod]

I have the Lyman tool & going by the swarf removed with only minimal use, there must be some pretty big flakes of brass sitting round the holes in factory brass, though use in fired brass seems to indicate a lot of it's blown away on first use,.
Doesn't stop me using it though, as it/s only a couple of seconds & might in a small way add to accuracy.
I've never thought of taking a photo down my borescope, so might try it out tomorrow.

 

[okie man]

I like the cut the Sinclair tool makes. Nice and flat. There's a fine line between no cut and way too much with the Lyman tool. I use a drill bit that just fits the inside the neck and a drill stop for mine.

 

[Mustang72]

I use a Lyman for mine. Just bought a new bag of Winchester brass and didn't need a boroscope to see how rough they were.

 

[Dirtrax]

I use the Lyman tool and it too has a cone depth stop. I've used a Sinclair and they both work equally well if the cases are properly trimmed.

 

[elf]

I use the primer hole cutter with my RCBS Casemate and it does a good job on most all brands. But I do not use it on Lapua brass because they are burr free right out of the box.

 

[Savage 12BVSS]

I use the Lyman tool and it too has a cone depth stop. I've used a Sinclair and they both work equally well if the cases are properly trimmed.

I agree with this post, I think the chamfer changes flame travel even in cases that have no punch hang pieces. But its only a personal unproved opinion.

 

[hogheadv2]

DAMMITMAN! Will these detail never stop ...... I took a long torx bit to mot of mine several years ago.
Let my cases run low to load all matching rounds this winter. This just put another week of time on my schedule.
Worth it...

 

[Creedmoor shooter]

I'll get my bore scope out tonight and try the same thing. Very interesting stuff.

 

[YZ-80]

I've never seen close-ups like that but do it faithfully with a lyman tool. I've always felt it made the flame path uniform and hence made ignition more uniform.

You are correct Sir! As a responsible and conscientious handloader I observe these practices as well.

On a side note, back in my motorcycling days, my mechanic did some top end work on a BMW boxer he had. He ground the intake valves around their perimeters to Ducati specs. This resulted in more uniform aspiration of the fuel into head. I think he picked up about 8 hp and 3 extra mpg!