Meplat trimming by OAL or ogive

dave,

we definately agree there, we would'nt be shooting dashers if we did'nt. i wonder if the yaw is harder to tune out with our 8 twist dashers than say the 30's with slower twists? i am going down to missoula monday to start testing with a new lot of bullets. i will pay attention to the tears and maybe post some pics.
tom
 
Charles calculated BC does not account for yaw, as there is no way to predict it, and it would be unique to various combinations. You can see with JBM that meplats have by far the biggest affect on BC, given other expected bullet variances. IMO yaw induced by meplats is speculation.
Also IMO, meplat trimmers should really be called 'nose length trimmers' as they don't unform meplats.
They simply trim nose length, leaving the meplat where it ends up.

So far it seems assumed that meplats are made uniformed based on improved grouping at 1kyd.
But has anyone actually measured trimmed meplats to determine that they are in fact -the same?
 
All I can say is I would rather have a trimmed/uniformed meplat that reduces the BC spread than one that has not been trimmed. The proof is over the chronograph and on the target, has been for years.

Dave
 
mikecr said:
Charles calculated BC does not account for yaw, as there is no way to predict it, and it would be unique to various combinations.
Click to expand...
I *think* we agree. You cannot predict yaw, but I believe you can predict the effect of so many degrees of pitch/yaw on drag (b.c.) An increase (or variation) of 1-2 degrees would be significant in 1,000 yard benchrest, where 10-shot groups in the 5.5 inch region are not all that uncommon.

We probably need someone like Brian Litz. I always thought that the initial pitch/yaw (aka tip-off rate) was not calculable, but given a specific tip-off rate, you could measure how long it took to damp. Again, with measurement (not prediction), you can determine if a bullet is dynamically stable. If it is not, secondary yaw will increase after velocity drops below a certain point.

But who cares? As Dave said, the effect of meplat trimming -- or adding tips to bullets -- can be seen on both a chronograph like the Oehler 43, and on the group size on target.

I would think that if a bullet is well-pointed, a meplat trimmer will give the same meplat diameter, and the whole ogive shape will be constant across a batch of bullets.

There have been some issues with bullets having a radical design -- such as a 15-caliber secant ogive, and/or small meplats. They are just quite hard to make with the consistency of a less radical design. I suppose an optical comparator would give an answer, but I don't see the need. If the bullets are consistently well pointed up, having only a ragged meplat, uniforming will do it. If they are not consistent at the tip, nothing will help.
 
Hey guys, Then your saying meplat trimming works better than just pointing.
All I did last year was point and got very good results. And some nice holes in the paper So does this mean if I trim then point I could shoot some nicer groups.

Joe Salt
 

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joe,
the answer is.... maybe maybe not, and can't proove it yet. 4 of the 5 100's i shot last year were with pointed only bullets. BUT the vertical agg was smaller with bullets trimmed and then pointed. couple that with the fact that conditions just so happened to be better when i was shooting the pointed only bullets, how can we proove or disproove anything. and now they logged our range this winter and took away all our wind blockers:(

tom
 
Gonehunting378

If you shoot 5-100's and Kathy shot 2-100's and 2-99's I'd kind of say pointing has the edge. Not that I'm not going to try both, but with the pointing there is a difference in elevation. Let's see if I get this pic. right.
 

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Back to the original question

Monte,

I just trimmed some 107 SMKs with Dave's tool. This lot is unusually uniform for bearing surface length, weight and meplat form and very accurate right out of the box so it might not be the best sample to seek an answer from from but for what it is worth...

Meplats were about 0.059" with a radiused edge of about 0.005" before trimming and oal varied about 0.003".

After trimming for 100% clean-up the meplates are uniformly 0.064" with no radius and oal is uniform to the limits of measurement. Measurement of meplats was with a microscope reticle at 0.01mm grid and 6" digital caliper for oa.l

Working backwards from that I presume that with reasonably uniform bullets it wouldn't matter whether a meplat trimmer indexes off the ogive or the base of a bullet

Regards,

Greg
 
Meplat trim and point

Greg:

When I started meplat triming and pointing in 2002 with the Original Ferris Pindell die, I was only interested in improving the 300 SMK. Ferris and I discovered that the core went almost to the very end of the meplat -- which always looked like the mountains on the Sierra box. Ferris built me a very heavy duty mini lathe about 9" long to take care of the meplats. I would trim the meplats with an end mill to uniform them like Dave says. After the meplat trim, I was shocked to find that many of the cores wer off center! Additionally, the jacket material was so thick that it was impossible to point the meplats as desired. So, we used a tool in the lathe that drilled the meplats on center and thinned the meplat in a cone. Then I could close the meplats with the Pindell die very nicely.

As an aside, I could take the worst looking bullet in the box of 300 SMKs and adjust the die to close them up very small. The very uneven meplat would just "disappear" in the closing. You could see the nasty folds, jags etc. but they were "merged" into a uniform point. Johnny Byers made me a "bullet board" to place the finished bullets base down. I could them inspect them from the top with a magnifier for uniformity of closure. I would also use very small drills as "gauge pins" to make sure everything was uniform on the trim/pointed SMKs.

Before I got my Pindell setup, I purchased one of Dave's meplat trim fixtures. The first time I shot them in practice at 100 and 200 yards, I immediately noticed that the 300 SMKs with a meplat trim punched holes that looked like they had been cut with a 148 DEWC out of my competition .38 revolver. I believe that I went to Hawks Ridge the next Friday to get sighted in at 1000 for the Saturday match. This was the same weekend that they tried the TV camera set up and they needed a test subject. I thought like a good lawyer, and offered to sacrifice myself. Of course I got centered dead on the X ring. Guess who won the match that weekend? :)

I remember like it was yesterday when Dave brought his cut meplats to Hawks Ridge. Whenever Mr. Tooly tries something new, he always wins with it and that weekend was no exception. The only reason for the Pindell die was to recapture the BC lost by the meplat trim as I need all the help I could get shooting against the greats at Hawks Ridge.

As an aside, when I started shooting my closed meplats in my 338 UGA, I would test them against the unaltered bullets on Friday when I would come up early. As best I could tell, the closed meplats printed what looked like about 12" higher so I knew something good was happening. The down side is that you have to do SO much to the big 300s to get them to shoot competitively. I suspect that is about to change with offerings from Berger and others.

BTW, there have been many records set and Championships won in long range prone and F-Class using pointed meplats. But just like with fine carbide bullet making dies, not all meplat pointing dies are the same -- not even within the same make. Like all dies, some are better than others. I got lucky. Of course, Dave developed a fixture to insert Sierra tips in his BIBs, and Scott Fletcher had Dave make him a fixture as well. Their success is well documented.

Just remembering old times,
Jim Hardy
 
Greg Culpepper
If you have Sierra's out of the box with only 0.003 OAL variation I would buy a lottery ticket as you are the luckiest man on the planet.I find that much variation on the bearing surfaces of most out of the box custom bullets I buy.

MikeCR
I sort by bearing surface first then I sort again by boattail to bearing length and trim the meplats.Once that is done you can sort by OAL and keep all like bullets into groups.I agree with you that just trimming will give you a wide variation in meplat diameters and nose lengths.I suspect most sort to the gnats a$$ if they are going through all the other trouble.
Waterboy
 
Lynn,

I agree that I'm lucky, not just in finding good bullets either. I've got a green eyed, red headed, left handed, cajun, scorpio only child for a sweetheart. She's a postmaster and I know that you know what that means.

My luck with bullets is even better than you thought.

These 107 SMK's bearing surface length is so uniform that they are essentially identical. They are the most uniform bullets I've ever measured. And they're accurate. I've been shooting them, sometimes pointed and sometimes plain, without sorting since they can't be sorted into groups. Last match at Piedmont was half pointed (heavy gun)and half plain (light gun). Sam and the rest of the gang at Piedmont can tell you how they perform or you can check last years match results for yourself.

I understand your skepticism of my measurements. My experience with handmade bullet bearing surface uniformity is identical to yours. Send me your address so the bullet fairy can call on you. If you don't mind, when you get them, get back to us on how these SMK's measure (and shoot) for you. I'd like you to weigh them also and kindly report back on that as well even though I think sorting for weight is a waste of time with any good bullet. You will need a scale that measures with at least 0.02gr precision to get meaningful results. Like most folks here, years ago I had to sort 100 6.5mm142's into three groups which, from across those groups, varied almost 40 thou. Those days are over. I've gone through a thousand of these 6's and haven't culled one yet. Adding to that happy fact is that the other Sierra bullets that I got at the same time (30 cal 155, 175 and 210's and 7mm/175's) while not as uniform as the 6's still must be considered excellent, typically showing bearing surface length variation of 3-4 thou, as uniform as very good handmade bullets.

Sierra has put real work into their quality control and you can buy the result of that good work. We enjoy the best bullets ever from all our treasured makers and I don't see that going back. The market for accurate bullets is too competitive for any bullet maker to coast.

Greg
 
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Hi Jim,

We've missed seeing you at the 1K benchrest matches so it was especially nice for me to get to visit with you recently during the Palma trials at Butner. Congratulations again on winning your place on the US Palma Development Team.

Thanks to for the history lesson on bullet improvement strategies at Hawks Ridge. The work that you, Dave, Scott, Ferris and many others did to improve the bullets we could buy has done much to demonstrate to manufacturers that it was worth their while to do everything they could to improve their product quality before delivery. And even with those improvements we still chase further refinement to the great bullets we can buy today. Will we ever be satisfied? Surely not.

Best regards,

Greg
 
You told me so . . .

Greg:

I remember when you came across the dead nuts 107 SMKs a while back. I trusted your opinion so much that I IMMEDIATELY ordered 1000 of the same lot from the same vendor. Your were right.

As for the National Team, we both know (and others) that you will be shooting on that stage as soon as as the opportunity presents itself. And, thanks for your friendship and the encouragement in terrible shooting conditions at Butner during the Tryouts. I was blessed.

Jim
 
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