Measuring stuff, COAL, ogive, bullet jump

Starting with handloading. I'm doing reduced power loads with H4895, haven't found any Trail Boss on the shelf yet.

I have made a couple of attempts at measuring where the lands on my 12FV (308) are. My latest are confusing me a bit. I have bought some different bullets and started with Sierra TMK, partly because I thought they were on sale - but not so much at the actual cash register, grrrr.

The two bullets I'm trying to use for measurement are the Nosler 125 gr Ballistic Tip and the Sierra TMK 125 gr. When you look at these bullets they have similar, but quite different shapes. Both have a plastic tip. If I take a pair of these and drop them into the jaws of my calipers set to .300", The Sierra will drop about 1/8" further, clearly it's ogive is more to the rear.

If I drop these bullets into the chamber of my rifle and then measure with a dowel from the muzzle, they both seat with the tip the same distance from the muzzle. I have measured with an aluminum .25" dowel and a wood .25" dowel. I used a straight edge razor across the muzzle to mark the dowels. This seems like it would be quite accurate, but it bothers me the results seem to be different between the two methods and also what the bullets look like.

The measurement with the dowel is telling me that my rifle gives a cartridge length of 2.825" with these bullets touching the lands.

I have some other size bullets to try and also think I'll seat some bullets in empty cases and measure before and after etc. Not sure what I'm asking, maybe for one thing wether people think it's reasonable to use a dowel to measure the distance to the bolt face and the bullet tip to see what your camber size is?

Your method seems sound. Trust your numbers and start from there. Put the bolt in, measure again with your dowel. Subtract the measurement with the bullet from the one to the bolt face and you have a "max"coal.

A better measurement would be to measure the ogive with a bullet comparator, not calipers. Tips will be inconsistent, even with the plastic tips. Measure bullet base-ogive. Measure bullet base to tip. Do more math and you can get a pretty good idea of the o-give to tip length. the lengths may be closer than they appear; if they are not, you may need to alter your approach.

I think you have a good starting point. I would take your "max" coal from above and load a dummy round, no primer, no powder, to that length. get the bullet good and black, with a sharpie or you can smoke it with a candle, and push it up into the chamber with your finger. If it sticks, you are probably in the lands. Use a rod to push it out and look for where the black is gone, these marks will be the lands. From there you can progress several ways. I seat the bullet .005 deeper (measureing cartridge base to o-give; cb-ogive) and repeat the sticking it in the chamber. When it no longer sticks, you are free of the lands. If the possibility of error of .005 is good enough for you, then measure cb-ogive again call it zero. Anything shorter than that will be off the lands, anything longer will be jammed. Use the same bullet comparator, they are not always the same.

if I am not making sense, and you would like a better explanation, let us know and somebody can help fill in the blanks.

What I have found most consistent is to simply put a bullet in a case, make it long (.050 longer than the book) and gently move the bolt forward.

You will find the bolt stops, probably sticks a bit, bump it back with a plastic handle, seat bullet .005 - -101 deeper, repeat.

Eventually you will reach a point where the bolt goes all the way forward , close it. Open it and if it sticks you still need another .005 shorter.

I then take the Hornady bullet OGIVE tool and write down that that reading . It is not COAL (to the bullet tip) it is more accurate on the OGVIE (bullet shoulder)

There is some OGIVE variation (not nearly as much as bullet tip) so you will have to move it one more .005 5 increment to keep out of the lands unless very experienced and you shoot in the lands.


You are not measuring a chamber, you are measuring where the OGIVE of the bullet engage the land. Each mfg has its own take on the shape of the lands as well as throat length.

It only applies to that specific bullet type from that mfg.

Hi Schnyd and RC, thanks for the help.

I would have got back sooner but still puzzling my way along. Guess I'm a 3 steps forward, 2 steps back and then a step sideways kind of guy. I'm getting there though.

I've found one issue and starting to figure another one. I used an aluminum rod a couple of times and aslo a wood dowel. Today I noticed that while pushing a bullet out of the bore I put a small dent in the end of the wood dowel. Maybe it's 1/16" of an inch, I haven't tried to measure it yet. Since the dowel is smaller than the bore, I suppose sometimes the dent lines up with the bullet and other times not. This likely is part of why the Nosler and Sierra bullets look different and measure the same.

Where on the ogive do the bullet comparators measure? On a side note I see that the Nosler and Sierra bullets have a different diameter, basically .307 and .308 respectively. The reviews for the various Hornady and Sinclair tools for this say they have some varience and there are issue even comparing between two of the same brand...

My results with an empty cartridge and bullet where a little confusing too. It was very hard to see the rifling at the muzzle end, becuase the inside of the barrel is black mostly. With sunlight and a 10x pocket magnifier it became clear though, there are 6 rifling lands and they are maybe 1/4 the size of the valleys. So what I see on the bullet I marked with a Sharpie is 3 of the valleys showing on one side of the bullet, not the lands. Or the shape of the lands gets wider in the leade area?

For this I was using a fired case with only a very short amount of neck sizing. Now with this info I think I can do as you guys are describing with a case with more neck sizing ( Wilson dies which do 3/16" of neck sizing ) and use my aluminum rod to help coax the case out without moving the bullet in the case.

I did take some little pieces of 1/4" aluminum bar I had and drilled some different holes in it, "L", "M", "N" and 19/64". So I may have my own ogive measuring thingie now. Or maybe not! LOL.

Up I'm lazy and try to do things the easy way. The easiest I've found is to take a flat base bullet insert it backwards in a snug fit case, ease it in chamber, when you remove it you will have the length from case base to lands. When you load,use a bullet comparater to check base to ogive. When you do this you can set any jump or jam you want.

So let's start at the top. bullet comparators will measure the o-give in slightly different spots from one to the next. That's why you need to buy one and stick with it. Not just that brand, but that exact comparator. All the measurements you are making are relative to the lands. Because of that, you can use a tool that is relative to the same spot on each bullet. Calipers, as good as they may be, are shit for measuring round objects. You really need micrometers with very fine contact points to get .001 or better precision

I am a little lost from there. all you are trying to do is find out when you are no longer touching the rifling with a bullet seated in a chambered case. There is no reason to be looking down the muzzle. Take your dummy round, remove the bolt, and stick the dummy up in the chamber with your finger. Give the case head a good press. Remove finger. If it sticks in the chamber, the lands are holding it there. Tap lightly with cleaning rod from the muzzle end. If you pressed hard enough, there will be small marks on the bullet. They will be parallel to the neck and depending on how far jammed you are, look like anything from faint lines to squares. Seat the bullet .005, or .003 or .001 further into the case until the case no longer sticks when you put it in there with your finger. With the bullet comparator you used, you now know your "max" cb-ogive.

I would start with a full length sized, once fired case from your rifle.

You can coat the bullet with soot from a candle to help you see if the bullet has contacted the rifling.

I too use a bullet comparator. I only have one rifle in each caliber so for my gauge, I neck size a case, insert the bullet and chamber the round. I guess I have been lucky, I have not had the bullet "stick".

OK, some more frustration but I think I'm getting answers from my rifle now. The reason I was looking in the muzzle was to get a better idea of what the rifling looked like, so I could look for it on the bullet. Knowing there are 6 grooves and how wide the lands are helped. I was marking the bullet with a Sharpie because I thought it would help, maybe it did - but it also showed other things.

The thing I have been seeing up until now is a large scuff mark that goes about one third to half way around the bullet. It completely removes the marker. About .05" above this is a ring of 4 rifling marks, they looked like little square patches of missing marker. I have just been missing them because they are much smaller than the scuff mark. The rifling and the scuff are on the same side of the bullet. Is this trying to tell me that my chamber and bore are not as concentric as they should be?

This cartridge now measures 2.827", that seems reasonable but maybe a little short? Tomorrow I'll try repeating this a couple of times and also try another brand bullet.

I am following this thread as I go through the very steps you have been doing. Mine is a 223 though. I tried several times with a bullet put in a crimped case and couldn't get a consistent reading after retracting. I saw the same scuff mark(s) on the bullet that you did. Without a bore scope, I have concluded that there might a burr(or two) ahead of the lands that is catching the ogive and not allowing to fully seat in the lands.
When I retracted the bolt, I was not confident that the bullet was not hanging up on the burr?? and pulling it out of the case some. I did get fairly consistent results with the dowel rod method, but didn't match the bullet in case scenario.
Once my reloading equipment arrives, I hope I can seat some blanks and get a better feel for bolt to lands measurement. I want to get a fairly close idea, so I can work up loads with a known jump and work up my ladder test.

Quote:

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Originally Posted by upinthehills

Hi Schnyd and RC, thanks for the help.

I would have got back sooner but still puzzling my way along. Guess I'm a 3 steps forward, 2 steps back and then a step sideways kind of guy. I'm getting there though.

I've found one issue and starting to figure another one. I used an aluminum rod a couple of times and aslo a wood dowel. Today I noticed that while pushing a bullet out of the bore I put a small dent in the end of the wood dowel. Maybe it's 1/16" of an inch, I haven't tried to measure it yet. Since the dowel is smaller than the bore, I suppose sometimes the dent lines up with the bullet and other times not. This likely is part of why the Nosler and Sierra bullets look different and measure the same.

Where on the ogive do the bullet comparators measure? On a side note I see that the Nosler and Sierra bullets have a different diameter, basically .307 and .308 respectively. The reviews for the various Hornady and Sinclair tools for this say they have some varience and there are issue even comparing between two of the same brand...

My results with an empty cartridge and bullet where a little confusing too. It was very hard to see the rifling at the muzzle end, becuase the inside of the barrel is black mostly. With sunlight and a 10x pocket magnifier it became clear though, there are 6 rifling lands and they are maybe 1/4 the size of the valleys. So what I see on the bullet I marked with a Sharpie is 3 of the valleys showing on one side of the bullet, not the lands. Or the shape of the lands gets wider in the leade area?

For this I was using a fired case with only a very short amount of neck sizing. Now with this info I think I can do as you guys are describing with a case with more neck sizing ( Wilson dies which do 3/16" of neck sizing ) and use my aluminum rod to help coax the case out without moving the bullet in the case.

I did take some little pieces of 1/4" aluminum bar I had and drilled some different holes in it, "L", "M", "N" and 19/64". So I may have my own ogive measuring thingie now. Or maybe not! LOL.

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You are welcome. While I thought I was a good re-loader back in the 70s, when I got back into it around 5 years ago, I got my butt kicked around a lot.

Fortunately I have a brother who did the same thing and in fact was the inspiration for me getting back into shooting (won't go into gory details other than I could no longer ride a cycle)

Between the two of us we have struggled through what we thought we knew, to what is a fairly decent understanding of the art these days. Its changed and a lot of what is still published while it works is crude and self defeating in some ways.

While Hornady makes an adaptor to measure OGIVE for a given caliber bullet (goes on their micrometer adaptor for that and shoulder bump back) I just made my own. Just my peculiarity, I like making tools like that, the cost of the whole set is miner, its the fun of doing it yourself.

I took the smallest shoulder bump back and drilled it out. My measurements do not match anyone else's, but it does not matter, its all relative and as each bullet is different, it would have to be the same adaptor and bullet and the concept is the same. And in the end (pun) each gun shoots different, each on is s a bid different throats wise and its all unique to a given gun.

You are just measuring somewhere on the curve (OGIVE) of the front of the bullet.

I take a press down to the range with me and work with it down there with bulk loads with bullets seated out too far.

A resized case without the expander ball in the die will make a very solid test cartridge for the set, check and adjust method.

I am a kind of rubber meets the road type, I don't get to carried away with the nuances, just something that works.

I don't color the bullets, just seat them long and close, feel, adjust until they are free. Its going to be a shade off but I can't shoot good enough to tell anyway!

Quote:

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Originally Posted by Haiku_Rodney

I too use a bullet comparator. I only have one rifle in each caliber so for my gauge, I neck size a case, insert the bullet and chamber the round. I guess I have been lucky, I have not had the bullet "stick".

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If you use the manuals they mostly will not.

I am after two things. Where the bullet is at maximum so I have a reference to work back form for free bore (a little or a lot)

The other part is I shoot a lot and that tells me how much I have shot out the throat.

Quote:

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Originally Posted by WV1951

I am following this thread as I go through the very steps you have been doing. Mine is a 223 though. I tried several times with a bullet put in a crimped case and couldn't get a consistent reading after retracting. I saw the same scuff mark(s) on the bullet that you did. Without a bore scope, I have concluded that there might a burr(or two) ahead of the lands that is catching the ogive and not allowing to fully seat in the lands.
When I retracted the bolt, I was not confident that the bullet was not hanging up on the burr?? and pulling it out of the case some. I did get fairly consistent results with the dowel rod method, but didn't match the bullet in case scenario.
Once my reloading equipment arrives, I hope I can seat some blanks and get a better feel for bolt to lands measurement. I want to get a fairly close idea, so I can work up loads with a known jump and work up my ladder test.

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That's the reason I don't use a sliding bullet. Its hard seated in a sized case and just nudge it.

Its not spot dead on to .001, but then OGIVE varies as much a .003 to .005.

Any seating adjustment I do when shooting is .005. Too much bullet variation to make it worth less than that.

The Hornady bullet seating tool (aka Stony Gauge) is not bad, but I found I never had an stick no matter how far forward I tapped it.

That's when I went to a hard seated bullet and the nudge back.

Don't get me wrong, its a decent tool for rough, plenty good for hunting if you are doing safe setup so you can't have round issues (which I think is right)

My lattes is the Lyman M gauge to do the neck sizing and getting rid of the expander ball in the FL die.

Much smoother, more consistent, should torque the neck and shoulder out less, help the concentricity of the round.

Quote:

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Originally Posted by upinthehills

OK, some more frustration but I think I'm getting answers from my rifle now. The reason I was looking in the muzzle was to get a better idea of what the rifling looked like, so I could look for it on the bullet. Knowing there are 6 grooves and how wide the lands are helped. I was marking the bullet with a Sharpie because I thought it would help, maybe it did - but it also showed other things.

The thing I have been seeing up until now is a large scuff mark that goes about one third to half way around the bullet. It completely removes the marker. About .05" above this is a ring of 4 rifling marks, they looked like little square patches of missing marker. I have just been missing them because they are much smaller than the scuff mark. The rifling and the scuff are on the same side of the bullet. Is this trying to tell me that my chamber and bore are not as concentric as they should be?

This cartridge now measures 2.827", that seems reasonable but maybe a little short? Tomorrow I'll try repeating this a couple of times and also try another brand bullet.

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There are all those variations, the only way to know is to shoot it and find out.

They can get far enough out to make a barrel a problem shooter, ergo, while the rifling part is the most important, a good chamber is next up (and that's includes the leads, throat and all that. )

Don't get a boroscoep, it will frighten you how ROUGHT it all is (even the good ones(. Bullet don't care, they till shoot good. Usually they don't build copper though rough enough they will.

Hey, upinthehills. After my post from last night, I am too OCD to let it go. Blackened another bullet, dropped it into the chamber, pushed it in with a dowel, then forced it out from the muzzle end. It had a definite score mark before the lands which tells me I have a small burr affecting the bullet and crimped case test. Crimped another case(I use needle nose pliers), started the bullet in, but this time I was not gentle with closing bolt and extracting. I actually worked the bolt back and forth 4-5 times, then fully ejected. I repeated this a second time and was within .001 of each and also matched the number I got with the dowel rod method.
I repeated again on a different size pill two times, and was also within .001 both times. This one was within .005 of my dowel rod measurement. I am now fairly confident of using these numbers for jump. YMMV

Didn't mean to drop this thread. I'm making progress, but didn't get solid answers yet. Then I was distracted because I decided to make an effort to buy some Trail Boss when my local place didn't have it for a couple of months. That required more than an hours drive each way, which combined with the small quantity of stock inspired me to buy the big jug. My next trip to the range was a disaster and depressing. The only good news that day was half my targets didn't even get holes in them when I was done :o. Being freezing out didn't help, but on my next trip to the range things went better when I noticed I had been dialing in more right when I really meant the other right. Sigh.

My other distraction is I am learning about casting bullets and will try some of that. From that I am learning about making a "pound mold". This involves using a piece of soft lead in place of a bullet, chambering that dummy cartridge and then carefully beating the bullet down from the muzzle with a metal dowel. This will cause the lead to expand and fill the chamber and take an impression of it. When removed this can be used to accurately measure the groove and rifling diameters and also where the rifling starts.

In my case I bought a foot of 5/16" soft lead wire along with some alloy for casting. I hoping I can use this both for a pound mold and to slug the barrel. I did actually look for a lead fishing sinker to slug the barrel but there was only tin, steel and tungsten at the sporting goods store...