Stumbled onto success! Wax check?

[PWS]

I ran out of gaschecks earlier this winter and being short on money and long on time decided to keep playing around with loads.

Test rifle is an off-the-shelf Ruger S/Lam in .30-06 and the mold is a stock Lyman #31141 date stamped 05-08 that casts in Linotype at ~ .310-311" (certainly not a "perfect" mold). Loaded to 3.060" oal over 10gr Unique, fired by CCI300s (ran out of LR's too...) and tested at 50yds.

This is the braggin' group of the three. Next was 1/2" and last was 1 3/8". No big deal you say but everything the same but with a 200gr LBT cut for the rifle cast in Linotype, treated the same way and the WORST group of ten at 50 has been just under 1/2". The LBT just starts to lead foul (1250fps mv) as does the Lyman (1350fps mv). The most intriguing part is that bullets fully lubricated shoot into 1 - 1 1/2" at 50. After reading a few threads about "overlube" or "lubepurge", I lubed up some bullets so that the gas check shank was the only place with lube and.... :holysheep


What a difference in accuracy!

http://castboolits.gunloads.com/imagehosting/166284d77045c38c5a.jpg

I recovered one of the Lymans from the snow downrange and hmmmm.... One side is pristine except for the rifling, the other shows... gas erosion? It can't be friction erosion as the shank isn't touching the bore. Why did the gas erode the side of a bullet when it didn't erode the base?

http://castboolits.gunloads.com/imagehosting/166284d77045c4a97d.jpg

http://castboolits.gunloads.com/imagehosting/166284d77045c5af31.jpg


I'm guessing that 10gr is just a skosh too much with the Lyman and right at that point with the LBT. The LBT maintains the same level of accuracy but the Lyman dropped off. I'm going to try some 9gr loads next. Both bullets have approached 1MOA with various loads with gaschecks but neither have ever shot this well!

[BulletFactory]

you found a bullet in the snow?!? Did you use a metal detector? That's hard to do.

[Rangefinder]

This is just a wild guess off the top of my head and after work (so thinking isn't always top-notch)... BUT--does this bullet seat deep enough that the base is below the neck? The gas erosion could simply be from that side of the bullet being on the bottom as chambered and in direct contact with the powder when fired--gas expansion happens really fast, but if it's a fast powder and a light charge, it's still starting below the bullet rather than behind it as it would with a full case or a filler.

Again--just a theory, so don't quote me on it.

[longbow]

That is certainly gas cutting and I see a little erosion on the base. The gas picks the easiest spot to "leak" and starts to cut the boolit there then if there is enough pressure it gets by somewhere else too or just cuts bigger in one spot. I have seen bad gas cutting down one side and I have seen boolits so badly gas cut there was no rifling showing and almost no w lube grooves.

Boolits well over bore diameter do seem to be more resistant to gas cutting (obviously a better seal). If your mould is under size you might lap it a thou or two for better fit. If the LBT was cut for the gun it should be good though. You might be at the pressure/velocity limit for PB in that gun with that load.

Believe it or not I have found many boolits in the snow and one that must have traveled most of 50 yards under the snow then hit frozen sand or something and popped up. It was laying unmarked at the 100 yard berm on top of the snow!

I always look for boolits... in the snow, after the snow melts and in the berm (soft sand). There is lots to be learned from recovered boolits.

Longbow

[geargnasher]

Good job!

I don't see any gas erosion at all. Maybe a skid mark from the snow, but nothing that looks like gas pressure cuts to me. Something else to try along with your lube "check" is put about 3/4 grain of fluffed Dacron to fill the space between the lube check and the powder, it might take closer to a grain. Reduce the Unique a grain or so also, the Dacron will raise pressure more than enough to compensate. The Dacron might help protect the base even more and helps with a "softer" launch, which in turn might take care of that hint of leading you're having even though it isn't necessary at all for combustion or consistency with Unique. I think the LP primers are also a large part of your success, less initial pressure.

Try some gas checks again as the budget allows, and use less lube or a softer lube. I get the best results typically lubing only one or two grooves of my .30 caliber boolits, maybe you will too.

Gear

[303Guy]

You don't get gas erosion or flame cutting on the base of the boolit - only on the sides. Thats because it's not the flame or the temperature doing the cutting but rather high velocity gas passing the boolit through very small gaps, at high pressure (and at high temperature) that erodes the lead from the boolit.

What I see does not look like flame erosion (or gas cutting). At first glance it looks like it but the area where it appears to be makes no sense. I'm with geargnasher.

Here's some flame cutting.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-522F.jpg

The hot gasses under pressure must have found a casting flaw and leaked through it, opening it up some.

[Bret4207]

Just a guess, but how is your alignment? Are the case necks of the loaded round a close fit? Is there any boolit run out at all? I think you need to continue along this line and see if you can pick up a pattern to this. Try marking the boolit and see if it's always on one side of the barrel that this happens.