MTAP (Meplat Trimming and Pointing)

[makurtz]

Bryan

You stated "Show me a rocket or airplane that has a hole in the nose..." So I showed you one. Sometimes I think Berger 108s have something special in them. Mayber not a jet engine but there is something special about them.

Note the shape of the fuel tanks.

 

[davidjoe]

Yesterday I watched launch 7 from the ground at the distance of about 80 sound seconds from the site. The nose of the”Ship” isn’t particularly pointy, but for the duration of time that the nose is in and leaving dense atmosphere, the speed is relatively low, but certainly Mach multiples, - indeed interesting.

I-phones allowed perfect synchronization of review, from Turks and Caicos to Space-X. It’s been reported that communication may have been lost for an extended period wherein the ship reentered the dense atmosphere “ballistically”, which I take to mean un-accelerated, and unguided, but at very high sub-orbital speed, many multiples of exit velocity, and I’ll conjecture weather-vaning into the airflow.

We have probably all seen that only one side is tiled, and deceleration attitude would necessarily be “point-up” so as to spread the exchange of speed for heat over as much ship area as possible, all tile-protected of course.

There was a Delta passenger that captured a stunning video, that’s a wing in the second picture. I’m going to suppose the pilots shared some choice words in a quandary as they probably saw both the burst and the advancing debris towards them, with likely no briefing of the putatively irrelevant Space-X flight.

Naturally, I’m curious what can be gleaned about all this if anything, pertaining to bullet tips. Blow ups are bedeviling and not uncommon in my circles. Do they start at the nose from heating? Apparently the nose is the hottest at the target despite no frictional bore contact. Midjacket? Is the lead melted when it occurs, because there is most certainly a cloud. (It’s difficult to envision mere air resistance atomizing solid lead into a cloud). If it is molten, what does that say about the lead when bullets make it? What role does the cleanliness of the barrel play, relative to deformation that perfectly cleaned lands and grooves do?

Sunday in a match, scoring for a friend (not code for me) we both determined, visually and separately, as I also shot his rifle so he could watch, was blowing up a certain 109 grain bullet 550 yards down range. This did not depend on his newish barrel’s temperature at all, happening often in two strings before he gave up, and his case was a perfectly normal performing dasher with no signs of a problem.

 

[Ruger15151]

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I have the MTAP on order since the end of December. Hopefully I will see the shipping confirmation soon

In the meantime, I have a couple of questions. I will be trimming the meplat of both 7mm 180 gr hybrids and 6.5mm 153 gr hybrids. I purchased the additional caliber setup for the 2nd caliber. Will I need to make any adjustments to the cutter angle between the 7mm 180s and 6.5 mm 153s or just change the housing and bullet holder? I would like to be able to change between calibers as quickly as possible.

Secondly, If we are trimming the tip based on the location of the base, are we still concerned with Lot #s or are the lot differences equalized with the MTAP process?

 

[Chaotik]

Now there is an AutoTAP upgrade.

AUTOTAP Upgrade Kit

 

[CA_Shooter]

So if someone wanted to use the MTAP to be able to take off .1 inches of a 180 hybrid to get it to mag feed...would this be a bad idea?

 

[WSnyder]

would this be a bad idea?

Probably…. .100” isn’t a small amount.

 

[Ruger15151]

How much are you guys trimming off the tips of Berger 180s? What is too much and what is not enough?

 

[MikeRu]

How much are you guys trimming off the tips of Berger 180s? What is too much and what is not enough?

Bryan doesn't want to share this information and I am sure he has tested extensively.

A matter of personal preference.

I sort into about 3 groups that are ~3 thou different (e.g. 0-3.0, 3.5-6.5, 7.0-10.0), then trim to bottom of each group.

Or sort by 4 thou and trim to “bottom of group +1”.

Any outliers are used as cold bore fowlers or for tuning.

Others might sort by length into 1 thou groups and not trim at all.

 

[Chaotik]

A matter of personal preference.

I sort into about 3 groups that are ~3 thou different (e.g. 0-3.0, 3.5-6.5, 7.0-10.0), then trim to bottom of each group.

Or sort by 4 thou and trim to “bottom of group +1”.

Any outliers are used as cold bore fowlers or for tuning.

Others might sort by length into 1 thou groups and not trim at all.

So you are sorting your bullets before using the MTAP?

I was under the impression, perhaps mistakenly, that the benefit of the MTAP machine was to eliminate bullet sorting, which I personally find incredibly tedious.
I actually asked if they (Bryan/Katie) do any sorting of bullets, and their response was: "We do not do any bullet prep before using them in the MTAP, we pull them directly out of the manufacturer's box with no additional sorting."

I don't have the MTAP machine yet (on order since January 1), so I have not done any testing.

 

[MikeRu]

So you are sorting your bullets before using the MTAP?

I was under the impression, perhaps mistakenly, that the benefit of the MTAP machine was to eliminate bullet sorting, which I personally find incredibly tedious.
I actually asked if they (Bryan/Katie) do any sorting of bullets, and their response was: "We do not do any bullet prep before using them in the MTAP, we pull them directly out of the manufacturer's box with no additional sorting."

I don't have the MTAP machine yet (on order since January 1), so I have not done any testing.

I don’t have the MTAP either. Correct, the MTAP is one step trimming and pointing. But there’s still the issue of sorting for bearing surface or base to ogive, this can vary depending on the lot#. And if there is a variation remaining in bullet length after using the MTAP then I think someone will decide to trim first. Bullet length can vary by almost 20 thou at the extremes so trimming all that away in the MTAP seems a little risky.

 

[Chaotik]

I don’t have the MTAP either. Correct, the MTAP is one step trimming and pointing. But there’s still the issue of sorting for bearing surface or base to ogive, this can vary depending on the lot#. And if there is a variation remaining in bullet length after using the MTAP then I think someone will decide to trim first. Bullet length can vary by almost 20 thou at the extremes so trimming all that away in the MTAP seems a little risky.

I gave up on sorting by bearing surface or base to ogive after doing it for years and finding that it made no difference in my testing. I ended up just sorting with a BGC and then refining each sorted lot by overall length.

 

[pkthornton]

CNC bullet trimming and pointing...

Video showing the process:

When we designed the IDOD/AUTODOD, we had always envisioned a machining center, not just a neck turning machine...
A project I have wanted to get going for awhile is the MTAP. Meplat, Trimming and Pointing. Bullet pointing with a swaging process like has been done for a long time and can have many issues. Jacket distortion is the biggest. BC consistency is another issue. So in the past we have tried to mitigate this by trimming all of the projectiles based on the ogive as a datum. Then we would sort by overall length. Then we would setup the swaging process to a given length and then adjust the die for each other length in batches of a .001". The end problem with this, is the swaging process never guaranteed BC consistency.
The MTAP process does three main things:
OAL of the projectiles is the same as we are datuming off of the base of the projectile.
BC is more consistent as OAL and meplat angles and diameters are the same
Zero bullet jacket to lead core distortion
In my opinion machining instead of swaging is a much more consistent result with no chance of bullet distortion.
I can have any angle, radi, etc on my cutting inserts to give whatever machined shape we desire on any given projectile, it is a fully modular system. There are about 500 IDOD/AUTODOD machines in the world and those users can get the MTAP kit and easily turn their neck turning machine into a bullet machining machine.


Shown here are photos of a 180 hybrid 7mm right out of the box, compared to a bullet that has been ran with the MTAP process.
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Why don't we put meplat trimming responsibility on the bullet manufacturers? I don't get it. Do you buy a bad car and have to fix it? Do you buy a NEW house and have to rebuild it? Explain why we have to fix the meplat on a bullet?

 

[DaveTooley]

Why don't we put meplat trimming responsibility on the bullet manufacturers? I don't get it. Do you buy a bad car and have to fix it? Do you buy a NEW house and have to rebuild it? Explain why we have to fix the meplat on a bullet?

Trimming meplats is like buying after market performance parts for a car.

I'm the person that brought to light the importance of the meplat. Initial testing on my own and then a large scale test for Sierra. The Sierra test comprised of measuring BC's on untrimmed, trimmed and bullets where I installed tips. From 22 to 338 caliber. The condensed version is trimming reduced the BC extreme spread but also reduced the BC by 2-3%, tipped did the same thing and increased the BC slightly, 2-3%. But the gains made by uniforming the meplat don't really show up on the target until you get to 500 yds. and beyond.

All trimming must be indexed off the Ogive. The frontal profile is critically important.