Meplat Trimming

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chinga
Posts: 10
Joined: Thu Aug 30, 2018 12:11 pm

Meplat Trimming

#1 Postby chinga » Mon Jul 15, 2019 2:21 pm

Hi All,
I’m only quite a new shooter and have a question on meplat trimming. Currently I’m trimming the meplat on my 155 30cal projectiles. I’m not pointing them as the price for a die is a little out of my price range for now but the advantages of getting more consistent flight is worth trimming. what I am doing is using a 1mm drill bit to clean the inside end of the projectile after trimming to create a symmetrical opening. The question is...is it worth using the drill bit to clean the inside end up rather than having it half full of copper? Will this create more drag on the projectile as it now has a hole on the end catching wind?
Also what is the advantages of batching these projectiles now once trimmed?
Look forward to hearing everyone’s opinions on this and what processes are really worth the extra time and effort.
Thanks

Peterla
Posts: 245
Joined: Tue Dec 14, 2010 10:49 am
Location: Barossa Sth Australia

Re: Meplat Trimming

#2 Postby Peterla » Mon Jul 15, 2019 2:59 pm

I do point the 155.5 Berger bullets then use a center drill to clean the inside a very very small amount
Then I use 1000 wet and dry to deburr the outside.
I then point them as I have a pointer unlike you.
This is only done on 700 yard plus projectiles.
I think if you over trim you might get a slight drag from burs but I am not an expert here.
Just trim as small amount as possible of and make sure you have a sharp cutter and burs are kept to a very small amount

Batch by bearing surface can help for the longs but you need good measuring equipment to do this.

bruce moulds
Posts: 2599
Joined: Sun Jun 19, 2005 4:07 pm

Re: Meplat Trimming

#3 Postby bruce moulds » Mon Jul 15, 2019 9:42 pm

drilling the front will make no difference to drag.
if you have burrs on the outside of the new meplat, and they are variable, that might be negative.
before pointing, we only used to trim.
there was an obvious reduction in b.c. as evidenced by lower point of impact.
when using one trimmed bullet as a control under a magnifying glass, and rolling other trimmed noses past it, showed that rarely were 2 meplats the same diameter.
this was mostly with sierra 142 matchking 6.5 mm, which must have had differing ogives from different machines
the point is that not only was b.c. being reduced, but b.c. sameness was being reduced.
in theory pointing will solve the problem, but you have to be pretty on the ball to be sure.
and if you overpoint, you can bulge the ogive and then have varying leade angle relationships.
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

wsftr
Posts: 100
Joined: Tue Jan 30, 2018 12:58 pm

Re: Meplat Trimming

#4 Postby wsftr » Tue Jul 16, 2019 9:11 am

That must be some pretty good flight consistency to make it worthwhile reducing the BC.

chinga
Posts: 10
Joined: Thu Aug 30, 2018 12:11 pm

Re: Meplat Trimming

#5 Postby chinga » Tue Jul 16, 2019 1:27 pm

Thanks Peter and Bruce for the great information looks like it’s definitely worth the money to splash out and get a pointer to get those meplat diameters more consistent and bring back the BC. Why do projectiles have a hole in the end? Does it help with stability in flight? Also when pointing is it ok to completely close up the hole or should you always leave a small opening?

ben_g
Posts: 166
Joined: Sun Apr 24, 2016 7:37 pm

Re: Meplat Trimming

#6 Postby ben_g » Tue Jul 16, 2019 1:59 pm

Don’t completely close the hole!! You run the risk of crushing/deforming the jacket.

I have just entered the world of pointing, and only as I got a die for a good price.

I would argue if your just starting out, and your shooting the short fat 30cal pills your time is better spent worrying about other variables. Namely reading the wind and shooting!!

Pointing has the biggest BC gain in long secant ogives and Hybrid ogives, the smaller calibres responding better as the size of the meplat relative to the nose section is larger.

If you really want to do it read this first.

http://appliedballisticsllc.com/Article ... inting.pdf

chinga
Posts: 10
Joined: Thu Aug 30, 2018 12:11 pm

Re: Meplat Trimming

#7 Postby chinga » Tue Jul 16, 2019 6:55 pm

ben_g currently I'm using berger hybrids so this process would as you said improve my BC and your exactly right about learning the wind but if you can keep your vertical group distance to a minimum you don't need to be as good to read the wind to still score in the circle. Between the projectile and the case there is so much "tweaking" you can do to both and like any newbie Ive caught the bug.

6.5x55ai
Posts: 201
Joined: Mon Mar 18, 2013 4:21 pm
Location: Waikato NZ (Ex Tyabb)

Re: Meplat Trimming

#8 Postby 6.5x55ai » Tue Jul 16, 2019 6:56 pm

chinga wrote:Thanks Peter and Bruce for the great information looks like it’s definitely worth the money to splash out and get a pointer to get those meplat diameters more consistent and bring back the BC. Why do projectiles have a hole in the end? Does it help with stability in flight? Also when pointing is it ok to completely close up the hole or should you always leave a small opening?


The hole in the tip is the end of the process whereby the projectile is formed (drawn) from the base to the tip. Part way thru its manufacture it is a tube with a closed end (the base).

I found it impossible to completely close the tips with my Hoover die. I used to reach an adjustment on the die whereby no further closeure occurred but further die adjustment caused the projectile to became "grippy" in the die when I went to remove it from the die. I couldn't determine by measuring though what had changed. I think my Hoover instructions do mention bulging at the ogive. I couldn't determine any change in the bearing surface but for the projectile to become slightly tight in the die that is where the change must have occurred, or on some part of it.

BTW: I have given up meplat trimming and tipping for shorts at club level. I lost the enthusiam for all the pre-sorting the boxes of projectiles into batches, ending up with several batches, even with quality projectiles like Berger. I may have been doing it wrong but each batch needed different adjustments to the meplat trimmer and the tipping die. I found if you used the same adjstment on the meplat trimmer for all projectiles in a lot some ended up over trimmed and some under trimmed, hence the need to batch.

Another BTW: I use a Montour County Rifles meplat trimmer. It has a minute drill (smaller than 1mm) in the end of the cutter which cleans out the meplat at the same time as trimming it.
Before that I started out with a Sinclair unit which was a POS.

ben_g
Posts: 166
Joined: Sun Apr 24, 2016 7:37 pm

Re: Meplat Trimming

#9 Postby ben_g » Tue Jul 16, 2019 7:24 pm

chinga wrote:ben_g currently I'm using berger hybrids so this process would as you said improve my BC and your exactly right about learning the wind but if you can keep your vertical group distance to a minimum you don't need to be as good to read the wind to still score in the circle. Between the projectile and the case there is so much "tweaking" you can do to both and like any newbie Ive caught the bug.


Pointing is the last 1% in the equation though and your wasting your time inside 900 yards IMO,

I managed to place reasonably well at the NSW long range champs (1000,1100,1200yards) shooting Berger 215’s. I just sorted them BTO, that loads elevation was excellent for the whole weekend.

I’m only exploring pointing in search of the last 1%, though usually if I have a shot out of the group at any distance i need to look in the mirror for the problem not the reloading bench.


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