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trimming the bullet meplay for better BC

 
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  #1  
Old 11-25-2003, 02:01 PM
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Join Date: Jul 2002
Location: France
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trimming the bullet meplay for better BC

anyone have try or test to trim the bullet meplat ( with a lathe or a small tool as Tooley tool ) in the aim to get more constant BC and less elevation defect at long range ?

good shooting

DAN TEC
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  #2  
Old 11-25-2003, 02:42 PM
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Join Date: May 2001
Location: NC
Posts: 352
Re: trimming the bullet meplay for better BC

Dantec,
I've been busy at work and haven't followed the message boards hardly at all in the last month or so. Don't know what you've read or been told on this.
I've been using one of Dave's meplat trimmers (one of his first prototypes) for 2+yrs now. We also have tested plastic tipped bullets that we assembled at his shop. It's an ongoing experiment and we have tested using an Oehler M43 at 300yds to measure BC dispersion with "untrimmed meplats", "trimmed meplats", and plastic tipped bullets out of the same rifle at the same time back-to-back to give us hard numbers to go by. The M43 has the acoustics screens setup to measure time of flight and actual BC numbers for every shot fired. I can't argue with the numbers/results anymore. It's clear the trend is in the right direction and that is reducing vertical dispersion.
By doing this you are not going to make a good rifle into a great rifle. But you will do away with unexplained flyers and help your group become rounded rather than the vertical we normally see when scoring 1000yd BR targets.

Hope this helps,
Steve

[ 11-25-2003: Message edited by: Steve Shelp ]
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  #3  
Old 11-25-2003, 03:32 PM
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Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: trimming the bullet meplay for better BC

Steve,

Have you guys experimented with cutting the tips way back, or just enough so they all clean up square vs. the wild uneven ones etc.

Have you played with boring the HP out larger and it's effects either?

Do the really wildly uneven tip always reduce BC by a certain amount?

Have you all established a baseline BC ES for the squared tiped bullets and compared them to the ES of random selected out of the box bullets?

Sorry for the twenty questions. [img]images/icons/smile.gif[/img] I never thought of testing this, but the SMK's especially are definitely pretty whacked in this area.

I'm curious, do you guys leave the acoustic target set up, or use a stand for it that is always a set distance from the bench?

I don't have this type of permanent setup, it's a real PITA to get accurate measurements without this.

As I'm sure you're aware of, the distance is very critical for absolute BC numbers, relative ones for tests like you're doing would be easier, if that's all you were after.

I usually measure from the frame it's taped up back to the front of the bench, then subtract from this the distance the muzzle of each rifle stick out beyond the bench.

Do you guys use a seperate frame for the acoustic target just ahead of another target frame to icsolate the sound traveling through the frame. It does travel faster through the wood than it does through the air, and often the target backer material will transfer this noise to the sensor before the mach wave reaches it.
The sensor will sometimes trigger too soon in this case.


.....


A side note on the acoustic target:

I learned something you might find handy if you ever think you might be having a problem with a sensor not functioning. If you have access to a 35P you can plug the acoustic leads into, tapping the white plastic of the sensor with a fingernail should trigger the printer to print. If it doesn't it isn't working. You have to plug each sensor into the "on" plug in on the 35P (left plug on the 35P) and test one at a time tho. It will just print zeros, but the sensitivity of the sensor can be verified this way.

[ 11-25-2003: Message edited by: Brent ]
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  #4  
Old 11-25-2003, 07:26 PM
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Join Date: May 2003
Location: Townsville Australia
Posts: 98
Re: trimming the bullet meplay for better BC

Dantec,The 3 targets in the photo are from our recent 500 met State Champs i shot .....The one in the middle was shot with Meplat uniformed 187 BIBs and the other 2 without.....The small group target (1.230 ins) was also the 1st target of the day in the best of the average conditions offered,since building the new gun i used i have not had 1 day i could call good conditions to test properly in so i can't say for sure it's worth the effort ,But it looks promising so 1 will continue testing....I made my own Meplat uniformer because it's not exactly just down the road for me to buy one living in Australia..JR...
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  #5  
Old 11-26-2003, 12:43 AM
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Location: Palmer, Alaska
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Re: trimming the bullet meplay for better BC

Nice groups Jeff! What's that you were shooting?
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  #6  
Old 11-26-2003, 12:52 AM
daveosok
 
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Re: trimming the bullet meplay for better BC

Where is the datum point referenced from to cut the meplat?
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  #7  
Old 11-26-2003, 01:22 AM
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Join Date: May 2003
Location: Townsville Australia
Posts: 98
Re: trimming the bullet meplay for better BC

Brent,The match has originated in Canberra Australia ,it's called the "Fly Shoot".....Started at my range some 2000 miles north of there in 1993 .....Only shot at 500 met,quite a challenge really ,it's the only shoot i know of to join score and group together for a total:-i.e. take the middle target ,it has 4 of 10s and 1 of 8 so subtotal 48 + 9 points for the group with 1 shot through the FLY for a total of on that target of 57.1 out of a possible of 60.5....The points for group are 10 for sub 1 inch group on down to 1 point for a up to 10 inch .Groups on the 3 targets are 1.230 , 1.91 , 2.40, there is 2 more targets from this match i could not in the photo and they were the worst ones shot in the mirage ,the 5 targets together give a 5 shot x 5 targets Agg of 2.95 ins...Clear as mud i guess,hope this helps..JR..Jeff Rogers ..ps on our range we have a cash prize of $1000 for first 5 shots in the FLY
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