Finding Precise COAL On The Lands

[SparkyLB]

Or, "The Wheel, Reinvented." Apologies in advance for a long read. I wanted to leave no questions, so here goes.

This is not an attempt to avoid purchasing a precision mic by RCBS or any other tool made expressly for this purpose, but I don't think I'm a fan of the Stoney Point (now Hornady) gauge.

I've been thinking about a method to find COAL from bolt face to lands, and came up with a plan that I'd like some opinions on. I've been reloading since the 80's, but this thought came to me yesterday. This would performed in, and intended for use by only one rifle. This rifle has had a new barrel installed a couple of weeks ago by me, and was properly headspaced with go and no/go gauges. The once fired brass would be provided by this gun. FWIW, I'm achieving almost MOA results with factory ammunition as I have not started to reload for this 270 Win. yet.

OK.. . . . here's the plan.

I'd remove from the bolt, the firing pin, extractor and ejector. The case would be a once-fired, fireformed casing that has not been resized in any way. This should yield a case that's +/- .001" small in every dimension (except for case neck length, which I might shave 1/32 from, to ensure it doesn't contact the chamber edge). The case would have no powder or primer. Just an empty case and a new bullet.

A very small amount of JB Weld would be applied by Q-Tip to the inside of the case mouth, about 1/8" below the lip. I'd make sure that the first 1/8" inside the brass was left clean, so no JB Weld could leak out of the case mouth and into the chamber. I'd also give the compound a few hours to tack up, before inserting the new bullet, so it can't flow out. A new bullet would then be dropped into the case, keeping OAL as long as possible for now.

After the new bullet is inserted into the brass; the "cartridge" would be dropped carefully into the chamber while the rifle is stood on end, muzzle on the floor (so gravity won't hinder the process.) The bolt is then inserted, lowered slowly and gently, then closed. After 24 hours, the expectation is that the resulting cartridge would be an exact duplicate of the chamber from bolt face to ogive on the lands.

If necessary, a cleaning rod might have to be used to coax the cartridge out of the chamber.

I could then use a bullet comparator like Hornaday or Sinclair's hex nut, and mic. the cartridge. I'd keep this dummy round in my reloading die box, and use it when I reload, as a starting point from which to subtract COAL, as I look for the bullet jump that this gun likes.

Thanks for reading this far, and please share your opinion. I'm pretty thick skinned, so if it's the dumbest thing you've ever heard--let's hear it! If this has been done a hundred times, let me know. Any opinions, like what you might do differently, not do, or would do that I haven't. . . . .would be appreciated.

Thanks, all!!

[kkeene]

Just split a case neck with a dremmel tool with cut off wheel. Split neck to neck / shoulder junction. De-burr inside and out of slit with a small stone in the dremmel tool.

Pinch the neck slightly, if required, to hold the bullet, seat a bullet long. When extracting this dummy round, support the case with your finger as soon as you can to prevent the bullet from dragging on the side of chamber during extraction. Measure COAL several times until you get a consistent measurement.

Realize that bullets in the same box will have different lengths, so this method is only as consistent as the bullets that you are using.

I often keep that bullet with the split case so that I can measure throat wear over time.

I would not use epoxy or other glues.

Keith

[LongRange]

just food for thought here...i just re-barreled my 260 and sent dummys in to have it chambered to. when i got the barrel i put it in my vise and checked all 3 bullets i had it chambered for(BEFORE)threading it on to the action with the stoney/hornady OAL gauge. each bullet(139g lapua,140g hornady and 142g SMK) were checked 10 times and all measurement were exactly the same measured off the ogive.
personally i dont think there is an exact way to measure the distance to lands and my only problem with your idea/thoughts here is "WHAT IF" some of the JB seeped out past the bullet/case and got into the lands? that would cause MAJOR problems for you...best case "IF IT DID HAPPEN" copper fouling,inconsistent groups,fliers ECT..."WORST CASE" we never hear from you again because of a catastrophic failure.

my advise to you is if you try this is to take a 12 gauge patch folded in half wrapped around a nylon bore brush with a light coat of oil on it and spin it in the chamber to coat it then send several oiled patches down the barrel to make sure EVERY part of the barrel has a light coat of oil before you set the dummy in for the night.

[Texas10]

I would like to suggest is a method I just used the other day after reading about it, can't remember where, but i was also getting erroneous measurements from my Hornaday LNL gage and wanted something more precise.

1. Take your fire formed cartridge as you describe and neck size it only, then seat your bullet long. Using a permanent marking pen, "paint" the bullet very evenly black, let it dry a few minutes and chamber it. If you feel pressure when closing, the bullet will be shoved back in to the cartridge a bit, so no worry. You may need that cleaning rod to help it back out of the chamber.

2. Notice the marks in the black ink. Set the cartridge in your press and push the bullet deeper what ever you think will get it closer to just touching the lands.

3. Clean the bullet and paint as before. Chamber it, remove and examine again for signs of lands marking the Ogive portion.

Continue with this technique, making smaller and smaller adjustments to the OAL until you see the barest of marks in the "paint". This is your datum point for touching the lands, but it is only valid for the tool you are using to measure to the ogive. If you buy another tool, you'll have to repeat this process as is it unlikely any two tools will reference from exactly the same point on the bullet contour.

I do as you describe and keep a dummy cartridge for each bullet so I know exactly how far out to seat and still keep clear of jamb situations. I'd suggest you mark it with a serial number and reference elsewhere the date, gun, bullet, and caliper insert used to measure ogive, etc in your notebook.

I mean….if you really want to get anal about it. LOL :rockon:

Oh, and if you decide to go with the epoxy and, of all the bad luck, have it stick, just heat the chamber with a hot air gun until the epoxy lets go. It won't hang on much above about 250 F. Of course, you'd first want to have it out of the stock.

[sharpshooter]

There is an easier way, especially when setting up a new barrel. Before you install the barrel, drop the headspace gauge in and measure the protrusion. Now drop in a sized case and measure it also, record the difference if any. Seat a bullet long in the sized case, and then drop it in the chamber and measure it. Measure the protrusion and record the difference.
Adjust your seating die to make up the difference from the empty case to the loaded one. Make the allowance for the difference between the empty case and the go gauge, plus .002" for headspace clearance.
For example: let's say the go gauge protrudes .127", a sized case protrudes .126", so you need to add .001" for the difference, plus .002" for the head space clearance. Let's say that your long seated bullet cartridge protrudes .153". So .153"-.129"=.024". Adjust your seater die down .024", re-seat the bullet and use this for a comparator measurement.

[D.ID]

You said "you don't think you like the hornady gauge".
Have you had trouble with one?
How often do you intend to repeat measurements as the throat erodes?
I have to admit to having had such great consistency with the hornady that I can't even entertain the thought of going to all the trouble of alternatives.

[Hotolds442]

This is the method I use, so far it seems to be working well plus it's quick and easy.
http://www.youtube.com/watch?v=9OZ8u8e7mSc

[SparkyLB]

This is the method I use, so far it seems to be working well plus it's quick and easy.
http://www.youtube.com/watch?v=9OZ8u8e7mSc

Thanks for the reply, Hotolds442. I've always been a bit leery of that tool, as I'm concerned with the potential deflection of the plastic parts causing an erroneous measurement. Maybe it's a groundless concern, but. . . .


Just split a case neck with a dremmel tool with cut off wheel. Split neck to neck / shoulder junction. De-burr inside and out of slit with a small stone in the dremmel tool.

Pinch the neck slightly, if required, to hold the bullet, seat a bullet long. When extracting this dummy round, support the case with your finger as soon as you can to prevent the bullet from dragging on the side of chamber during extraction. Measure COAL several times until you get a consistent measurement.

Realize that bullets in the same box will have different lengths, so this method is only as consistent as the bullets that you are using.

I often keep that bullet with the split case so that I can measure throat wear over time.

I would not use epoxy or other glues.

Keith

Thanks, Keith. I've read a bit about this method, and was concerned that the splits in the case neck might affect the chambering of the brass due to the "petals" flaring out. At this point, all I've done is read, so the only knowledge I have is from reading of the attempts of others.


just food for thought here...i just re-barreled my 260 and sent dummys in to have it chambered to. when i got the barrel i put it in my vise and checked all 3 bullets i had it chambered for(BEFORE)threading it on to the action with the stoney/hornady OAL gauge. each bullet(139g lapua,140g hornady and 142g SMK) were checked 10 times and all measurement were exactly the same measured off the ogive.
personally i dont think there is an exact way to measure the distance to lands and my only problem with your idea/thoughts here is "WHAT IF" some of the JB seeped out past the bullet/case and got into the lands? that would cause MAJOR problems for you...best case "IF IT DID HAPPEN" copper fouling,inconsistent groups,fliers ECT..."WORST CASE" we never hear from you again because of a catastrophic failure.

my advise to you is if you try this is to take a 12 gauge patch folded in half wrapped around a nylon bore brush with a light coat of oil on it and spin it in the chamber to coat it then send several oiled patches down the barrel to make sure EVERY part of the barrel has a light coat of oil before you set the dummy in for the night.

Thanks for replying, LongRange. I would take 3 precautions to darn near guarantee that no leak could occur. The JB Weld would be applied deep within the neck, in a very small amount, and would be given time to get tacky before the bullet was inserted. That said, if I do go forward with this; I would take your suggestion about the oil in the chamber and barrel.

[SparkyLB]

I would like to suggest is a method I just used the other day after reading about it, can't remember where, but i was also getting erroneous measurements from my Hornaday LNL gage and wanted something more precise.

1. Take your fire formed cartridge as you describe and neck size it only, then seat your bullet long. Using a permanent marking pen, "paint" the bullet very evenly black, let it dry a few minutes and chamber it. If you feel pressure when closing, the bullet will be shoved back in to the cartridge a bit, so no worry. You may need that cleaning rod to help it back out of the chamber.

2. Notice the marks in the black ink. Set the cartridge in your press and push the bullet deeper what ever you think will get it closer to just touching the lands.

3. Clean the bullet and paint as before. Chamber it, remove and examine again for signs of lands marking the Ogive portion.

Continue with this technique, making smaller and smaller adjustments to the OAL until you see the barest of marks in the "paint". This is your datum point for touching the lands, but it is only valid for the tool you are using to measure to the ogive. If you buy another tool, you'll have to repeat this process as is it unlikely any two tools will reference from exactly the same point on the bullet contour.

I do as you describe and keep a dummy cartridge for each bullet so I know exactly how far out to seat and still keep clear of jamb situations. I'd suggest you mark it with a serial number and reference elsewhere the date, gun, bullet, and caliper insert used to measure ogive, etc in your notebook.

I mean….if you really want to get anal about it. LOL :rockon:

Oh, and if you decide to go with the epoxy and, of all the bad luck, have it stick, just heat the chamber with a hot air gun until the epoxy lets go. It won't hang on much above about 250 F. Of course, you'd first want to have it out of the stock.

Thank you for the reply, Texas10. I've read a bit about this method, and it seems like it could work. I might give it a try.


There is an easier way, especially when setting up a new barrel. Before you install the barrel, drop the headspace gauge in and measure the protrusion. Now drop in a sized case and measure it also, record the difference if any. Seat a bullet long in the sized case, and then drop it in the chamber and measure it. Measure the protrusion and record the difference.
Adjust your seating die to make up the difference from the empty case to the loaded one. Make the allowance for the difference between the empty case and the go gauge, plus .002" for headspace clearance.
For example: let's say the go gauge protrudes .127", a sized case protrudes .126", so you need to add .001" for the difference, plus .002" for the head space clearance. Let's say that your long seated bullet cartridge protrudes .153". So .153"-.129"=.024". Adjust your seater die down .024", re-seat the bullet and use this for a comparator measurement.

Thank you, Fred. Your method is practical and sounds like a winner. It's tempting to tear down the rig and try it; but I have an EGW one piece rail that's loctited to the receiver. As you know, this mount overhangs the barrel nut. On top of that is a zeroed-in scope that sits in EGW rings. These rings have screws on the sides, so they'd have to come off to get to the mount. If I ever change barrels again, I'll definitely use this method.


You said "you don't think you like the hornady gauge".
Have you had trouble with one?
How often do you intend to repeat measurements as the throat erodes?
I have to admit to having had such great consistency with the hornady that I can't even entertain the thought of going to all the trouble of alternatives.

Hi, D.ID. Thanks for the reply. I've never used the Hornady tool. As I mentioned in a reply above, all my knowledge with this facet of reloading is from reading, so I don't have any hands-on experience here. I'd repeat the process when accuracy diminishes, suggesting throat erosion has changed bullet jump. From what I've read about the Hornady tool, is some experience a lack of repeatability. I've also read that it takes a "feel" to get it right. If I did buy a tool that was made for this task, I'd probably get the RCBS Precision Mic before any other.

[limige]

no problems here using the hornandy tool. don't know what the issue is with whomever you were talking to on it. pretty cut and dry, consistent readings for me

[limige]

I will add, I also use calipers with a bullet comparator installed to measure the round after setting the length.

so you need the
oal guage
comparator kit
calipers
modified case
bullets

[limige]

http://tapatalk.imageshack.com/v2/15/03/09/38b573a4266ef42acc01c46d68dc6286.jpghttp://tapatalk.imageshack.com/v2/15/03/09/66aa3d0823dca333042faf1d66cc1bb7.jpg

[SparkyLB]

I will add, I also use calipers with a bullet comparator installed to measure the round after setting the length.

so you need the
oal guage
comparator kit
calipers
modified case
bullets


Yep. Still undecided on what route to take. I did see an encouraging You Tube video where a bullet is seated long, and the user successively tightens the seating stem in very small increments until the bolt will close. The FP, ejector and extractor are out, and he uses a very gentle hand to "feel" where the bolt is just about ready to close. I might try that method. I respect the forum's response on the JB Weld idea, and think I'll not take the chance.

Here's the video (https://www.youtube.com/watch?feature=player_embedded&v=Jv-D1mEI514). Seems pretty straightforward, but a mite time consuming.