DT's MicroGroove Bullet

[montana_charlie]

I'm starting this discussion due to a response to a post of mine by 45 2.1.
Here is that conversation, and we can go from there...


- Dan Theodore is currently working on a bullet design that has two main differences from the old standby designs. The grease grooves are very narrow and shallow, Presumably for his dip lube, as it sounds like anything else won't work. and the nose is more aerodynamic than the good old Creedmoor and Postell. Hmmm, you got a link? In order to center up in the bore, Dan's bullet depends heavily on the bore ride section being supported within the lands. Contrary to most BP ideas and right in line with smokeless ideas. To help insure this, he has gone to a shorter taper in the leade (3 degrees per side)...so the bullet can be inserted more deeply into the barrel. How so?
Here is the thread that first caught my attention...
http://shilohrifle.com/forums/viewtopic.php?t=7875

This the most recent thread on the subject, and includes a diagram of the .45 bullet...
http://groups.msn.com/BPCR/general.msnw?action=get_message&mview=0&ID_Message=31676&LastModified=4675605640907266950

The discussion where Theodore talked about going to a steeper leade is something I will have to search for. The other threads I've seen are mostly concerned with smaller caliber bullets, so I didn't make any attempt to note their locations. Those discussions about the .38 calibers usually have the bullet named 'MicroMiniGroove'.

As far as understanding how a steeper leade allows a bullet to reach further into the barrel...Dan explains it in more technical terms (if I can find them)...but, think of it this way.

Say you have a pencil that will just fit in the neck of a funnel. That's the bore ride fit.
Now, a half-inch back from the end, wrap some tape around the pencil to get a diameter too big to go into the neck. If the funnel wall has a very long, deep angle the tape will contact the wall before the tip goes very far into the neck.
Change to a real shallow funnel and the pencil goes in further before the tape hits the wall.

Sure, you can change the tape...just like you can change a bullet's shape...to get deeper insertion. But, if the bullet shape is unchangeable because you consider it to be 'aerodynamically perfect'...you gotta change the funnel to get the pencil in deeper.

Dan's 'tape' is the second driving band in the diagram of the .45 MiniGroove bullet. It is too big to be part of the bore ride, and is smaller than the full-diameter bands and base. It is supposed to contact the leade angle to provide a second contact area to point the bullet down the center of the bore. Having a short, steep leade angle allows the bore ride to sit deeper in the barrel.

Now you know everything I know about the subject, so far.
CM

[Buckshot]

..............Kinda like a tapered schutzen boolit maybe?

................Buckshot

[Char-Gar]

Looks like a "nosey" Loverin bullet..same principal anyway.

[45 2.1]

It seems like the BP guys are abandoning the undersize nose idea and going to the standard bore ride smokeless design now (that works better at long range). Its all about boolit fit!

So, is he lubeing these boolits with a lubrisizer and seating out? If so, he is going smokeless!

[13Echo]

A close fitting bore riding bullet in black powder requires very good control of fouling. This is being achieved by patching the bore after every shot and by careful attention to load development to get as clean a burn as possible and by using special lubes - Dan T's White Lightning. Otherwise the tight fit won't load without a struggle when the bore is fouled. A lot of interesting work is being done with bullet design and lubes for black powder now. Certainly there hasn't been this much going on since the days of the Creedmoor matches.

Jerry Liles

[45 2.1]

There was a thread discussing Lanotec as a miracle lube which kept fouling very soft with no fouling buildup. I have been unable to get any so far. With bore riding boolit designs, the BP guys at least have a chance of getting the groups I get with the same rifles with smokeless.

[montana_charlie]

..............Kinda like a tapered schutzen boolit maybe?


Looks like a "nosey" Loverin bullet..same principal anyway.
If you take the grooveless bullet in this old thread (http://castboolits.gunloads.com/showthread.php?t=9907) and lay one diagram on top of the other you will notice there's almost no difference...except for the grooves.

The second driving band on the MiniG takes that portion of the bullet out of the bore ride section, and the MiniG has a slightly smaller 'ball' used for the nose tip.

Disregarding those two details, and removing the grooves, makes all dimensions essentially identical. The MiniG bullet's smaller nose tip caused a change in the ogive arc, which made the OAL just a bit shorter.

So, is he lubeing these boolits with a lubrisizer and seating out? If so, he is going smokeless!
The bullet is expected to be seated out so the second band contacts the leade somewhere within it's 'cone'. Where that contact point will be depends on the gun. The main guy shooting it at LR is using a .45-70. So, it stands to reason he wants it poked out far enough to get something like a .45-90 powder charge under it. I think he's using 75 grains.

Dan will always recommend his own brand of lube, but this time he doesn't require a 'dipping' lube. He says to use WL BPCR lube (the lubrisizer kind), so I guess the lube choice is up to the shooter.


Changing gears...
I am not Dan Theodore's biographer, so I don't know much about his 'history'. And, I certainly can't get inside his head and tell you what he thinks is important about any aspect of BPCR.

But, since I have been reading his stuff on the internet, I've learned that he is an experimenter. He has worked on lubes, barrel configurations, and bullet design.

I think a 'bullet designer' should create a design which shoots like a champ in Everyman's rifle. Maybe he did that before I 'discovered' him...or maybe the Postell already fills that niche. (whatever...)

Dan has (apparently) set out to find the best long range bullet - cast from lead - and propelled by black powder - that can be used in the old single shot guns.

I happened onto his course of experimentation when he was in his 'grooveless phase', and it seems that it was during that quest that he settled on a bullet shape that meets his goals.
The requirement for 'dipping' lube and the problems with leading may be the factors which pointed him back (part way) to grease grooves...but he has returned to the grooved bullet with his new shape in tow.

The inventor of the 'grooveless bullet' has (apparently) moved on.
So...in spite of the time and effort that has gone into the quest...and disregarding the fact that some shooters claimed good success with the design...I am going back to grooves.

Whether I'll try the MiniGroove remains to be seen, but I have a nice grooveless mould which I'm willing to pass on to someone with more time and desire. To that end, I will soon post an ad in the Swappin' and Sellin' section.
From there we can discuss details, as the bullet it casts won't fit just every gun out there.
CM

[Bret4207]

Chargar hit on my thought- A Loverin design with a Squibb nose. Might just work.