Re: Bullet Diameter Measuring Tool - Finally Finished
- Thread starter PMA3
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Re: Bullet Diameter Measuring Tool
When I did it, it was purely for a brief survey and I made some assumptions. I only hold the bullet so that the micrometer can clamp on it. As you can see in my photo in Reply #40, the ratchet can hold it strong enough to hold up a 77 grain 223 bullet.
However, if you are interested in a more vigorous method, I would suggest clamping a stop under the jaw which would allow you to rest the tail of the bullet on its surface. That way, you can adjust where the stop is so that you are consistently measuring the same pressure ring area. Now, this does not take into account whether the bullet is concentric but I don’t think your method will do that either. For that, you will have to take at least three measurements around its circumference using the micrometer.
When I did it, it was purely for a brief survey and I made some assumptions. I only hold the bullet so that the micrometer can clamp on it. As you can see in my photo in Reply #40, the ratchet can hold it strong enough to hold up a 77 grain 223 bullet.
However, if you are interested in a more vigorous method, I would suggest clamping a stop under the jaw which would allow you to rest the tail of the bullet on its surface. That way, you can adjust where the stop is so that you are consistently measuring the same pressure ring area. Now, this does not take into account whether the bullet is concentric but I don’t think your method will do that either. For that, you will have to take at least three measurements around its circumference using the micrometer.
Re: Bullet Diameter Measuring Tool
Add to the tool a precision ground cylinder that's the same diameter of the bullet (as designed). Put this "standard" in the v-block and zero the dial indicator. Then measure the bullet. Results will show as amount over or under the nominal bullet size.
Maybe a turning mandrel in a custom diameter for a quick, easy, and precision "standard".
338 Mollett said:
Add to the tool a precision ground cylinder that's the same diameter of the bullet (as designed). Put this "standard" in the v-block and zero the dial indicator. Then measure the bullet. Results will show as amount over or under the nominal bullet size.
Maybe a turning mandrel in a custom diameter for a quick, easy, and precision "standard".
Re: Bullet Diameter Measuring Tool
Actually trying to measure roundness with a two point mic can give wrong answers in most cases. Most often used is a three point shaft mic that has a vee or a vee block/indicator setup. Out of roundness is usually lobed and two points can't catch the magnitude.
The only problem with measuring any of this is the cost of the right tool used to measure to these tolerances. Either an indicating mic like the one I posted or a snap gage would be the quickest to get actual measurements without taking into account roundness. It's hard to beat their speed vs conventional mics but it comes with a price tag. The mic I listed is well over 1k. The only problem with the indicator/vee block method is the price of an indicator that will truly repeat to less than .0001. Most are at least 750.00 and good ones go well on up from there. Just because the resolution goes out so many decimal places it doesn't guarantee it can measure to it.
To sort bullets and reach a compromise with speed and cost a gage like the OP mentions sounds like a good idea. It would take testing to see how much of a problem having one stick in a hole would be though. I mean you would have to start with the smallest hole each time and if it's larger it wouldnt make it through.
jlow said:
Actually trying to measure roundness with a two point mic can give wrong answers in most cases. Most often used is a three point shaft mic that has a vee or a vee block/indicator setup. Out of roundness is usually lobed and two points can't catch the magnitude.
The only problem with measuring any of this is the cost of the right tool used to measure to these tolerances. Either an indicating mic like the one I posted or a snap gage would be the quickest to get actual measurements without taking into account roundness. It's hard to beat their speed vs conventional mics but it comes with a price tag. The mic I listed is well over 1k. The only problem with the indicator/vee block method is the price of an indicator that will truly repeat to less than .0001. Most are at least 750.00 and good ones go well on up from there. Just because the resolution goes out so many decimal places it doesn't guarantee it can measure to it.
To sort bullets and reach a compromise with speed and cost a gage like the OP mentions sounds like a good idea. It would take testing to see how much of a problem having one stick in a hole would be though. I mean you would have to start with the smallest hole each time and if it's larger it wouldnt make it through.
Re: Bullet Diameter Measuring Tool
No expert here and I understand why using a two point mic is not as good as a three point mic would be better, but it would seem that an out of round bullet will show up as inconsistent diameter with a two point mic if you measure at least three measurements around the circumference as I originally suggested. You certainly don’t know what the max and min diameters are but you should know that there is a problem which is really what you are interested in?
Using a gauge like what the OP is describing, I can envision an undersized bullet that is elipical in cross-section fitting perfectly through the optimal diameter gauge and the operator not knowing it is happening…. THAT is what I don't like about this idea of a go/no go gauge.
No expert here and I understand why using a two point mic is not as good as a three point mic would be better, but it would seem that an out of round bullet will show up as inconsistent diameter with a two point mic if you measure at least three measurements around the circumference as I originally suggested. You certainly don’t know what the max and min diameters are but you should know that there is a problem which is really what you are interested in?
Using a gauge like what the OP is describing, I can envision an undersized bullet that is elipical in cross-section fitting perfectly through the optimal diameter gauge and the operator not knowing it is happening…. THAT is what I don't like about this idea of a go/no go gauge.
Re: Bullet Diameter Measuring Tool
It depends on how the diameter is lobed. I'm not sure the nature of the bullet making process but it is very possible to measure undersized or round with a two point mic and the shaft not fit into a ring gage and not be representative of its diameter. There used to be an example at a place I worked in the lab. Had a shaft ground to 1.3748 minus .0005. Measuring with a two point mic would get 1.3740 in three places and looked round but under. The part was not even close to fitting through a 1.375 ring gage. Wouldn't even start. Vee block and indicator showed multiple lobes and scanning on the cmm showed 5 distinct lobes with an extreme diameter of 1.376. Very eye opening for choosing the proper tool to measure. Form of shafts and holes are one of the hardest.
My guess is that the bullet will be very round and you should be able to get a close enough measurement two point. Just don't go telling any bullet manufacturers they are wrong
. There are so many factors to precision measurement. When I do contract measurement for customers it's done in a temp controlled room on calibrated equipment and the part stabilized temp at least 24 hours before with all conditions recorded.
It depends on how the diameter is lobed. I'm not sure the nature of the bullet making process but it is very possible to measure undersized or round with a two point mic and the shaft not fit into a ring gage and not be representative of its diameter. There used to be an example at a place I worked in the lab. Had a shaft ground to 1.3748 minus .0005. Measuring with a two point mic would get 1.3740 in three places and looked round but under. The part was not even close to fitting through a 1.375 ring gage. Wouldn't even start. Vee block and indicator showed multiple lobes and scanning on the cmm showed 5 distinct lobes with an extreme diameter of 1.376. Very eye opening for choosing the proper tool to measure. Form of shafts and holes are one of the hardest.
My guess is that the bullet will be very round and you should be able to get a close enough measurement two point. Just don't go telling any bullet manufacturers they are wrong
. There are so many factors to precision measurement. When I do contract measurement for customers it's done in a temp controlled room on calibrated equipment and the part stabilized temp at least 24 hours before with all conditions recorded.Re: Bullet Diameter Measuring Tool
Plug gages and ring gages are some of the most accurate ways there are for finding true "working" size of holes and shafts no matter it's form. The hard part is finding actual measured differences causing problems when it shouldn't. This go/nogo gage is just simulating ring gages at different diameters. You control the extreme form by the diameters specified. As an example if it fits through a .2434 hole and won't go through a .2432 hole it's max diameter is somewhere in between and could be sorted and is a very good representation to it's size without going into further detailed measurements to find them out.
Hope this helps. Personally I think for the purpose at hand you are correct that you probably could catch potential problems. I would start that way myself and may try a few just to see with the indicating mic. The hole gage would be a good representation though of max diameter including form as long as getting stuck wasn't a problem.
jlow said:
Plug gages and ring gages are some of the most accurate ways there are for finding true "working" size of holes and shafts no matter it's form. The hard part is finding actual measured differences causing problems when it shouldn't. This go/nogo gage is just simulating ring gages at different diameters. You control the extreme form by the diameters specified. As an example if it fits through a .2434 hole and won't go through a .2432 hole it's max diameter is somewhere in between and could be sorted and is a very good representation to it's size without going into further detailed measurements to find them out.
Hope this helps. Personally I think for the purpose at hand you are correct that you probably could catch potential problems. I would start that way myself and may try a few just to see with the indicating mic. The hole gage would be a good representation though of max diameter including form as long as getting stuck wasn't a problem.
Re: Bullet Diameter Measuring Tool
I understand the potential complexity of items that are out of spec, I mean really you could somehow have a lump fused to the surface of the bearing surface at only a specific place. Would that affect MV, sure, but your chance of finding it without a scanning EM is nil.
So coming back to the reality of measuring bullets, one has to make some reasonable assumptions about problems that any method can address. In this case, it is they can be undersized/oversized, and if not concentric with two opposite lobes which the mics should catch.
The way I look at reloading, none of the “improvements†we put in will make the final product perfect, but each improvement makes the final product an iteration better and that to me is what this is about.
I understand the potential complexity of items that are out of spec, I mean really you could somehow have a lump fused to the surface of the bearing surface at only a specific place. Would that affect MV, sure, but your chance of finding it without a scanning EM is nil.
So coming back to the reality of measuring bullets, one has to make some reasonable assumptions about problems that any method can address. In this case, it is they can be undersized/oversized, and if not concentric with two opposite lobes which the mics should catch.
The way I look at reloading, none of the “improvements†we put in will make the final product perfect, but each improvement makes the final product an iteration better and that to me is what this is about.
Re: Bullet Diameter Measuring Tool
I'm ignorant as could be when it comes to all of this precision measuring you guys are talking about but I would like to try something like the op proposed. My thinking would be something similar to a neck bushing made from carbide but maybe it wouldn't be feasible.
I'm ignorant as could be when it comes to all of this precision measuring you guys are talking about but I would like to try something like the op proposed. My thinking would be something similar to a neck bushing made from carbide but maybe it wouldn't be feasible.
Re: Bullet Diameter Measuring Tool
Was driving home tonight and thought of a potential problem with the idea of using different size bushing to sort the different size bullets – the problem relates to entry angle.
Since we are talking differences of only 1-2 ten thousands of an inch and the fit is soo tight, there is very little tolerance here and since we are dealing with bullets which are long, the angle that the bullets are introduced into these bushings could be pretty critical. It would seem like that even a few degrees off from a absolutely perpendicular entry would make the diameter of the bullet significantly bigger and come off as being too large and cause a jamming effect?
This reminds me of previous efforts of getting a large couch through a tight fitting doorway and the trouble I have experienced....
Was driving home tonight and thought of a potential problem with the idea of using different size bushing to sort the different size bullets – the problem relates to entry angle.
Since we are talking differences of only 1-2 ten thousands of an inch and the fit is soo tight, there is very little tolerance here and since we are dealing with bullets which are long, the angle that the bullets are introduced into these bushings could be pretty critical. It would seem like that even a few degrees off from a absolutely perpendicular entry would make the diameter of the bullet significantly bigger and come off as being too large and cause a jamming effect?
This reminds me of previous efforts of getting a large couch through a tight fitting doorway and the trouble I have experienced....
Re: Bullet Diameter Measuring Tool
I'm picturing something like the Buhay tools comparator where it is stepped from a larger diameter down to the actual size used. Maybe even a slight taper rather than the step. That should help line the bullet up square wouldn't it? Or a piece similar to the caliber sleeve on a pointing die? I've been thinking about this method of sorting for awhile. When measuring Bergers with a mic I find that there is a pressure ring (right term?) right at the boat tail that is significantly larger than the bearing surface. With this bushing type sorting, this ring is going to determine which pile said bullet goes into but is this the real point that a guy would want to sort from or would it be the shank size variance that would make the difference on target? I guess the way I'm thinking about it now is, that ring may be an insignificant point of concern once the powder is lit.
I'm picturing something like the Buhay tools comparator where it is stepped from a larger diameter down to the actual size used. Maybe even a slight taper rather than the step. That should help line the bullet up square wouldn't it? Or a piece similar to the caliber sleeve on a pointing die? I've been thinking about this method of sorting for awhile. When measuring Bergers with a mic I find that there is a pressure ring (right term?) right at the boat tail that is significantly larger than the bearing surface. With this bushing type sorting, this ring is going to determine which pile said bullet goes into but is this the real point that a guy would want to sort from or would it be the shank size variance that would make the difference on target? I guess the way I'm thinking about it now is, that ring may be an insignificant point of concern once the powder is lit.
Re: Bullet Diameter Measuring Tool
jlow & LRPV,
Sorry for the late reply; our PA deer season ended last Saturday and I was hunting all week.
These are both excellent ideas, they seem to go hand in hand. If the hole can be made with
a tapered cone, this would really help self align the angle of entry and would be much better than
a straight hole. I have found two sources for the tool and am awaiting quotes...I will discuss this
change when I'm contacted...a work in progress.
jlow & LRPV,
Sorry for the late reply; our PA deer season ended last Saturday and I was hunting all week.
These are both excellent ideas, they seem to go hand in hand. If the hole can be made with
a tapered cone, this would really help self align the angle of entry and would be much better than
a straight hole. I have found two sources for the tool and am awaiting quotes...I will discuss this
change when I'm contacted...a work in progress.
After 5 months of trial and error, I finally now have a tool that works like I envisioned it would.... it took me less than an hour to sort 500 Berger 108 gr. 6MM bullets. I am already measuring bearing surface with the Buhay Comparator, meplat trimming and tipping with the Hoover tools and weight sorting to .01, so another hour spent trying to get the best matched bullets seems like time well spent.
The holes were burned first with electrical discharge machining (EDM) to .2430", then finally hand polished out to reach my target diameters of .2433", .2436" and .2439" as my lot of 3500 bullets measured .2436" when I took a random sampling of 75 bullets. I learned that you need a hole TWO ten thousandths larger before the bullet will slip through the hole, not ONE, so a bullet that is .2435", .2436" or .2437" will not go through the .2436" hole but will easily slide through the .2439" hole. A bullet measuring .2434" or less would slide through the .2436" hole, so if the bullet settles in the .2436" hole, I know it is either .2435", .2436" or .2437" and that range is acceptable to me. The bullets were started tip down in the .2436" hole, then I let them slide to a stop (see pic). All bullets were easily pushed up and out with my index finger....not one bullet out of 500 got STUCK in that hole! Only TWO of the 500 bullets did not slide through the .2439" hole and were delegated to clay bank foulers. I also periodically measured random bullets with a Starrett 1" outside mic secured in a Hart 3rd hand stand as a further control measure. I'm posting 4 pictures (I hope they post) so you can see what the finished tool looks like. For me, this was a worthwhile project and gives me the results I'm looking for.
The holes were burned first with electrical discharge machining (EDM) to .2430", then finally hand polished out to reach my target diameters of .2433", .2436" and .2439" as my lot of 3500 bullets measured .2436" when I took a random sampling of 75 bullets. I learned that you need a hole TWO ten thousandths larger before the bullet will slip through the hole, not ONE, so a bullet that is .2435", .2436" or .2437" will not go through the .2436" hole but will easily slide through the .2439" hole. A bullet measuring .2434" or less would slide through the .2436" hole, so if the bullet settles in the .2436" hole, I know it is either .2435", .2436" or .2437" and that range is acceptable to me. The bullets were started tip down in the .2436" hole, then I let them slide to a stop (see pic). All bullets were easily pushed up and out with my index finger....not one bullet out of 500 got STUCK in that hole! Only TWO of the 500 bullets did not slide through the .2439" hole and were delegated to clay bank foulers. I also periodically measured random bullets with a Starrett 1" outside mic secured in a Hart 3rd hand stand as a further control measure. I'm posting 4 pictures (I hope they post) so you can see what the finished tool looks like. For me, this was a worthwhile project and gives me the results I'm looking for.
Attachments
Rather than shooting them into the clay bank, did you shoot them at paper to see what kind of problem the odd bullets actually caused?
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