Meplat effect on BC

[JHardy]

With a 90 grain .223, you have plenty of BC. Put your efforts into techniques that will give you consistent BC -- thus waterline vertical. An easy task and you are almost there.

.040 meplat modification on a 90 grain .223 is rather large. Should be able to close them like a dart -- better BC and more consistent BC. As to the .020, you can even get it even smaller than that -- much smaller. Here is a hint and example of what I do. Get a nice cool drink or cup of coffee and one of your 90 grain match bullets. Take your time and look at the design of the meplat. Look at the size of the meplat. Look at the thickness of jackets. On some bullets, if the meplat closing fixture follows the ogive nicely -- like a tangent ogive -- that fixture makes a pretty bullet but does little compared to a fixture that can modify the Tangent to more of a Secant. If the bullet is a Secant VLD, your process is the same, but easier.

A match bullet is what it is and no more. Observe that bullet. Take measurements of the bullet. Look at the detailed data and diagrams of your bullet in Bryan Litz's library. Study ballistics and that will tell you how to design a bullet -- or enhance the one you have.

Like a great painting that speaks to you, a bullet will do the same thing. It will scream loudly in it's silence. Listen to it. Study it. Become it. Then you can modify it to make it your own design -- a better design that captures BC and waterline.

I know this response is a little bit of a "trip" and "off the top" but if you want to shoot your best you have to learn how to do more than simply closing the meplat with a "correct" fixture. You can get 90% of the sought after results by doing just that. if you want that extra point or X or a few .000 smaller group at 600 and 1000, that extra 10% is the road less traveled by most of your competitors. In time, that extra perfection will earn you the victory that would have otherwise slipped through your hands And yes, some youthful or senior shooter or best shooting buddy will beat the snot out of you on occasion with
much less to no effort -- and they will dog talk your big time. Payback is served cold while you eat a fine warm steak to celebrate your victory -- and your previous competitor in question will ask: "What in the world have you done to shoot so well today?" Your answer: "Here is a hint: Get a cool drink or cup of coffee and ........." How sweet it is

Enjoy the journey,
Jim Hardy

Hardy Custom Bullets, Inc.
Passion + Precision = Perfection

Shop: 770-886-1997
Cell: 770-855-8960

 

[Laurie]

Seems the bto movement was consistent across all the bullets over pointed and I did not notice any bulging at the tip but still tossed them. I might purposely do a few like that and shoot them at the end of a string next match and see what happens. [jsthntn247]

If you do, please post your findings.

 

[spclark]

I might purposely do a few like that and shoot them at the end of a string next match and see what happens. [jsthntn247]

If you do, please post your findings.

Indeed... seems like a worthwhile experiment! Once I'm done loading for the upcoming 2015 Midwest Palma Matches I may very well undertake a similar experiment, see what the effects are at 600 yards & if time & conditions permit at 1,000 also.

 

[jsthntn247]

I looked at the meplats for a while yesterday and decided to run a test at 1k when I get a chance. I had to point until the bto changed .004 to close the meplat completely. I pointed 5 bullets each at a bto change of .004, .003, .002, and .001. I sorted the bullets by base to tip first and all bto's moved exactly the same for each bullet in each group, so it is repeatable. I'll pick a calm morning and shoot the 5 shot groups at daylight at a large board and mark the impacts and report back. I will also shoot a control group of unmodified and a group of pointed to the max with no bto change. I'm assuming I will have to modifiy the case base to ogive measurement for each group to keep them the same distance from the lands but will check for that before hand.

 

[harv50]

following

 

[R.Morehouse]

This thread is some great stuff. I am trying to get a system down to do everything to the highest quality and ring every last bit of I can out of the reloading bench. Discussions such as this help me to see yet another level.... 8).....Just glad to be here.......Rick

 

[VaRandy]

Short and simple answer is yes. By how much, maybe a percent or two, have to fire them to find out.

Matches are one by a percent or two.

 

[dbduff]

Love this site!

 

[Joe Salt]

If I could add my two cents, After checking BTO. I first make sure mine go through a bushing that allows bullets, before and after to go though, this will also keep you from pointing too much!

Joe Salt

 

[M14AMU]

Probably more important is adhering to the IRONCLAD RULES OF MARKSMANSHIP!

 

[284winner]

Will these two bullets have a different bc? The more pointed one was .020 longer base to tip and undoubtedly went farther into the pointing die.

Without a doubt there WILL be a noticeable difference. Like stated above, hard to tell how much. Certainly not alot. Two percent maybe three. At extended ranges tho, 2-3% is a significant difference at 1000 yards. Even more beyond.

 

[paulT]

I looked at the meplats for a while yesterday and decided to run a test at 1k when I get a chance. I had to point until the bto changed .004 to close the meplat completely. I pointed 5 bullets each at a bto change of .004, .003, .002, and .001. I sorted the bullets by base to tip first and all bto's moved exactly the same for each bullet in each group, so it is repeatable. I'll pick a calm morning and shoot the 5 shot groups at daylight at a large board and mark the impacts and report back. I will also shoot a control group of unmodified and a group of pointed to the max with no bto change. I'm assuming I will have to modifiy the case base to ogive measurement for each group to keep them the same distance from the lands but will check for that before hand.

I ran a small test at 1000y pointing 200.20x with both the reccomended 20x bullet tipping punch along with a 185g hybrid tipping punch both batch of bullets started out with same ogive to base and overall length measurements at simlar weight, The 185g tipping punch pointed 20xs seem to have a longer portion of the bullet pointed with ogive to base measurement closed by a couple of thou, The reccomended 20x tipping punch pointed bullets closed the meplat length less than the 185h tip punch with no increase of base to ogive measurement but an increased overall bullet length roughly the same with both bullet batches, At 1000y the 20x tipping punch bullets shot in the range of 4 inch verticals with horizontal range as expected with the prevailing wind conditions however the longer pointed 185g h tip punch bullets shot 7 inch vert with what appears slight horizontal stringing possible reason for results is that a bulge was formed just below the pointed area by the 185g h insert.