Trimming and pointing

[BradY]

Bryan

A quick question,

Im trimming and pointing some 7mm 180gr hybrids which Im only doing to try and eliminate any possible inconsistencies in BC for long range f class, not to deliberately try and push for more BC. I notice some of the meplats seem to have only a slight amount of material trimmed off them, and others have more. The trimmer I use is indexing off the ogive of the bullet so Im assuming some have slightly longer tips on them. It doesnt seem much until you trim. Anyway the ones that have more material taken off seem to point up with a smaller internal diameter of the meplat vs those that have less material removed. Is there a ballistic difference between the smaller internal diameters at long range or does it all matter about the outside profile of the meplat- which should be the same after my trimming and pointing operation.

 

[DocUSMCRetired]

We actually don't recommend that you trim when pointing.

1. Always leave a tiny air gap in the meplat.

2. "Trimming. Sometimes you can see tiny imperfections after pointing, but to say you "need" to trim after pointing is to say that the small imperfections make a difference. "If your goal is to make bullets that fly uniformly at the highest levels, it may not be necessary to trim them." - Bryan Litz. In fact Bryan Litz has won a quite a bit of and in his own words "I've never trimmed a bullet tip, before or after pointing". So in the end it is up to you to decide."

https://www.facebook.com/AppliedBallisticsLLC/posts/959982670730283

 

[barefooter56]

BY1983,
If your meplat trimmer works off the ogive of the bullet. You will have to sort your bullets by base to ogive into groups and adjust the cutter for each group so you are trimming them all as close to the same as you can.

 

[jsthntn247]

If you don't trim before you point, you will have to sort you bullets based on OAL. If not you will point the longer bullets allot sharper than the shorter ones. My 90 vlds vary in length .018 from shortest to longest. If I were to set the die up to point a short one without moving the base to ogive measurement of the bullet then point a long one on that same setting the bto measurement would change signifigantly on the longer one and actually buckle the bullet jacket. I sort in .001 batches and point each accordingly.

 

[Jay Christopherson]

If you don't trim before you point, you will have to sort you bullets based on OAL. If not you will point the longer bullets allot sharper than the shorter ones. My 90 vlds vary in length .018 from shortest to longest. If I were to set the die up to point a short one without moving the base to ogive measurement of the bullet then point a long one on that same setting the bto measurement would change signifigantly on the longer one and actually buckle the bullet jacket. I sort in .001 batches and point each accordingly.

How do you know the difference in bullet OAL is at the tip and not somewhere else (say, base/boattail length, bearing surface length, or really, any point that is south of the tip), in which case, it makes no difference at all what the OAL of a bullet is when you go to point it.

 

[BradY]

So just pointing by itself will reduce BC inconsistency? Im happy not to trim, but some of them take material off a high point only ie the meplat isnt flat and square. I thought doing this would assist in uniformity between projectiles which is what Im after. Chasing extra BC isnt what Im trying to do. I do a sample sort of bullets BTO as well before doing this but Im really happy with the consistency of the sample I took from this batch so I left the rest be. Havent had any culls yet.

 

[dannyjbiggs]

If you don't trim before you point, you will have to sort you bullets based on OAL. If not you will point the longer bullets allot sharper than the shorter ones. My 90 vlds vary in length .018 from shortest to longest. If I were to set the die up to point a short one without moving the base to ogive measurement of the bullet then point a long one on that same setting the bto measurement would change signifigantly on the longer one and actually buckle the bullet jacket. I sort in .001 batches and point each accordingly.

How do you know the difference in bullet OAL is at the tip and not somewhere else (say, base/boattail length, bearing surface length, or really, any point that is south of the tip), in which case, it makes no difference at all what the OAL of a bullet is when you go to point it.

We don't really know where that OAL error resides!? But, we have to grab hold of something to achieve some half-assed order to the trimming and/or pointing process...even if it is not perfectly accurate. For trimming, to just go thru your box of bullets without first OAL sorting will yield over-cut and under-cut mephlates. I'm not saying that it would not be fashionable to run a sample, and take an average cutting height (I won't dare do that)...but a 100% OAL sort beats the heck out of that approach. For pointing, to just go thru your box of bullets without first an OAL sort will yield over-pointed and under-pointed mephlates. If you have pointed in this fashion, you should at least go one ardorus step further: Closely examine the mephlate diameters under magnification and eye-ballingly SORT THEM BY MEPHLATE DIAMETER and shoot them in those batches. But with this step, you have basically sorted them by OAL (using your pointer)...think about it...haven't you? And, what you have left really makes you want to do some re-pointing. So, my advise is to just go ahead and OAL sort the whole darn mess to begin with.

Dan

 

[6BRinNZ]

If your indexing off the ogive, wouldn't it be best to use a bob green tool to sort and then trim? Then use OAL to group for pointing? Shoot in batches of OAL pointed?

 

[jsthntn247]

If you don't trim before you point, you will have to sort you bullets based on OAL. If not you will point the longer bullets allot sharper than the shorter ones. My 90 vlds vary in length .018 from shortest to longest. If I were to set the die up to point a short one without moving the base to ogive measurement of the bullet then point a long one on that same setting the bto measurement would change signifigantly on the longer one and actually buckle the bullet jacket. I sort in .001 batches and point each accordingly.

How do you know the difference in bullet OAL is at the tip and not somewhere else (say, base/boattail length, bearing surface length, or really, any point that is south of the tip), in which case, it makes no difference at all what the OAL of a bullet is when you go to point it.

Like Dan said, you really don't know where the variance is. Bullets with the same bto measurement can also have the largest overall length difference. When pointing, the bullet sets on a flat base on its boat tail and is pushed up into the tipping insert, that's why sorting by overall length is important if you don't trim. I've tried trimming and found that all I end up doing is clogging the meplat on bullets that get allot taken off and they don't point up as good as the others that have little to none trimmed. I just point now and that seemed to add 6% to the bc as best as I can calculate.

 

[6BRinNZ]

BY1983 - have a read of this thread - read Toms post - it'll get you to where you want to go. BTW Bob green tool best tool I've bought that is coincidently related to my vertical improving noticeably (1 of 3 changes so I can't hang it all on the Bob green tool).

http://forum.accurateshooter.com/index.php?topic=3889079.0