i use a wilson microtrimmer and have the whidden meplat kit, trimming 7mm berger hybrids. how much should be trimmed? if i adjust the micrometer to trim a 'little' from one bullet, it may not even touch the next one. now what? readjust the micrometer for each one? sort by some criteria first? would appreciate some advice please.
meplat trimming question
- Thread starter dunraven
- Start date
I have the same setup you are using. I pick out about 20 bullets at random from the box. Measure the OAL of each and find the shortest. Set your trimmer to just trim .010" or so from that bullet and leave it set there. Trim all the bullets to the set length and you at least have a good base to meplat. I point the bullets from that point (every pun intended) but regardless you have a more uniformed group than you had to begin with. FWIW I have found with Berger Fullbores that the longest OAL to the shortest before trimming is about .008" for the three lots I have on hand before trimming.
I trim the same was as the previous poster but just enough to clean the rounded brass in the tip of the shortest ones, but I batch them as I go into two batches according to whether the cut is mild or aggressive. I'm not as anal as some batching projectiles, but I reckon that the difference in cut is a reflection of bearing surface length.
DocBII
Gold $$ Contributor
dunraven,
This works for me, I use a minimum of 500 as lot. Sort by ogive length first, a maximum of +/- 0.0025 batches. Measure bullet length for 30-50 bullets, set the trimmer to take off 0.010 of the longest length and trim all the bullets. You'll get a yield of about 150-200 with even points off the first pass. If you get more, you're taking too much off; if less, not enough. Set the trimmer to take off another 0.010, run the untrimmed or unevenly trimmed bullets, yield should get another 150-200. This depends on the bullet consistency. If needed, make a third pass on the remainder. You may have 20-50 which don't fall into a group, either by ogive length or trim length, use these for sighters or whatever. You can remove the swarf from the points by tumbling with ball bearings in a vibratory tumbler before pointing. Takes about 30-60 minutes. Or you can put about 50 in a box holding 500 of the bullets and shake and twist for 10-15 minutes. The latter is not as effective as the former.
Then point the two or three groups, starting with the longest bullet length. Re-adjust the point die for the shorter groups.
HTH,
DocB
This works for me, I use a minimum of 500 as lot. Sort by ogive length first, a maximum of +/- 0.0025 batches. Measure bullet length for 30-50 bullets, set the trimmer to take off 0.010 of the longest length and trim all the bullets. You'll get a yield of about 150-200 with even points off the first pass. If you get more, you're taking too much off; if less, not enough. Set the trimmer to take off another 0.010, run the untrimmed or unevenly trimmed bullets, yield should get another 150-200. This depends on the bullet consistency. If needed, make a third pass on the remainder. You may have 20-50 which don't fall into a group, either by ogive length or trim length, use these for sighters or whatever. You can remove the swarf from the points by tumbling with ball bearings in a vibratory tumbler before pointing. Takes about 30-60 minutes. Or you can put about 50 in a box holding 500 of the bullets and shake and twist for 10-15 minutes. The latter is not as effective as the former.
Then point the two or three groups, starting with the longest bullet length. Re-adjust the point die for the shorter groups.
HTH,
DocB
You're likely to mess your bullets up with all the merchandising & generalizations about what you're doing.
Keep in mind that the important adjustment here is NOT bullet OAL.
You want same meplat diameters, as this holds a large affect to BC.
Trimming them all to the same lengths, while causing different meplat diameters, is degrading to the whole purpose.
To achieve same meplat diameters with trimming you would first establish matching datums on the nose(not way back at the base). Why not back at the base? Because that's base length + bearing length + nose length, and OAL does not directly(if at all) correlate to meplat diameter variance.
To establish bullet nose datums you would first match noses by ogive radius(not nose length) (cull the rest). With this, and taking trimmer datum off matching ogives, you can at least cause both meplats and nose lengths to be the same. NOW what matters is more consistent.
Point from here, again, off matching ogive datums.
Bearing length and base length are relatively minor to BC. If you desire to match them, then you'll have to do so as individually as meplats.
This is not easy and since you can't adjust base or bearing lengths, matching means more $culling$.
Keep in mind that the important adjustment here is NOT bullet OAL.
You want same meplat diameters, as this holds a large affect to BC.
Trimming them all to the same lengths, while causing different meplat diameters, is degrading to the whole purpose.
To achieve same meplat diameters with trimming you would first establish matching datums on the nose(not way back at the base). Why not back at the base? Because that's base length + bearing length + nose length, and OAL does not directly(if at all) correlate to meplat diameter variance.
To establish bullet nose datums you would first match noses by ogive radius(not nose length) (cull the rest). With this, and taking trimmer datum off matching ogives, you can at least cause both meplats and nose lengths to be the same. NOW what matters is more consistent.
Point from here, again, off matching ogive datums.
Bearing length and base length are relatively minor to BC. If you desire to match them, then you'll have to do so as individually as meplats.
This is not easy and since you can't adjust base or bearing lengths, matching means more $culling$.
Dunraven...the first thing I do before pointing and/or trimming is to do a 100% OAL sort into .002 batches. Thereafter, starting with the longest batch (or the shortest, your choice), I set my trimmer (or pointer, if I'm not planning to trim) for that batch. For the next lower batch, I adjust my pointer/trimmer down .002, and so on, until I have finished all batches.
FWIW, I seldom remove more than .005 when trimming; and, I set my pointer to basically restore .005 to the bullet OAL.
It's practically MANDATORY to do an OAL sort prior to taking on the pointing process or the trimming/pointing process, IMO.
Dan
FWIW, I seldom remove more than .005 when trimming; and, I set my pointer to basically restore .005 to the bullet OAL.
It's practically MANDATORY to do an OAL sort prior to taking on the pointing process or the trimming/pointing process, IMO.
Dan
dmoran
Donovan Moran
Similar to Tom, I qualify in 3 steps:
- Base to Ogive: A-------B
- Base to Seater: A--------------C
- Tare length the ogive's: B------C
(my reasoning; I want consistent bullets to seating length, with relevance to BtO qualification)
Next I check the OAL A-------------------D
If they measure close (under say 0.003"), I do not trim and will just point them. If they have more, trimming is needed.
But here is a kicker: again like Tom, I am also a group shooter, and have to test the modifications to raw accuracy.
Because with some bullets I have experienced loses to raw accuracy when trimming and/or pointing, and is not always a gain. And can not take for granted that pointing and/or trimming is always going to be a gain, because I have seen it go both ways.
At the same time, a score shooter could have gains in BC that may out weigh a raw accuracy lose, due to windage gains, and is more likely to get more positives from pointing and/or trimming then a group shooter.
My 2-Cents
Donovan
- Base to Ogive: A-------B
- Base to Seater: A--------------C
- Tare length the ogive's: B------C
(my reasoning; I want consistent bullets to seating length, with relevance to BtO qualification)
Next I check the OAL A-------------------D
If they measure close (under say 0.003"), I do not trim and will just point them. If they have more, trimming is needed.
But here is a kicker: again like Tom, I am also a group shooter, and have to test the modifications to raw accuracy.
Because with some bullets I have experienced loses to raw accuracy when trimming and/or pointing, and is not always a gain. And can not take for granted that pointing and/or trimming is always going to be a gain, because I have seen it go both ways.
At the same time, a score shooter could have gains in BC that may out weigh a raw accuracy lose, due to windage gains, and is more likely to get more positives from pointing and/or trimming then a group shooter.
My 2-Cents
Donovan
Dusty Stevens
Shiner
You must sort them off the same point your trimmer indexes off of. If you sort with a tool that goes just say .500 from the base but your tool indexes .650 from the base you got a lot of variance there. So whatever the hole size is on your sorting tool your cutter needs the same size hole or youll see the variances in ogives between bullets very quick
No, if you use a BGC (like Tom) or tare to determine relative match in ogive radius (like Donovan), your noses will be sorted to shape. When your trimmer takes datum off those matched shapes, then meplats can be set to the same diameters through trimming to the same nose lengths.
It's all relative and tools never have to and never do actually match anything. In other words, there is no standard to match other than what we set locally.
We merely have to know what we're doing.
Also, Meplats are not a tuning attribute, for either precision(grouping) or accuracy(score).
So matching meplat diameters will not affect tune.
That notion must be coming from something else.
But if you're mismatching meplat diameters, well that's going to directly affect external ballistic results right there.
It's all relative and tools never have to and never do actually match anything. In other words, there is no standard to match other than what we set locally.
We merely have to know what we're doing.
Also, Meplats are not a tuning attribute, for either precision(grouping) or accuracy(score).
So matching meplat diameters will not affect tune.
That notion must be coming from something else.
But if you're mismatching meplat diameters, well that's going to directly affect external ballistic results right there.
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