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#1358203 - 08/26/09 02:45 AM Homemade bullet comparator
huntnfish08 Offline
Seasoned Member

Registered: 11/28/07
Posts: 342
Loc: Central Wisconsin
I was just looking at bullet comparators on midway and saw PTGs comparator. Looks like a nut with holes drilled in it. I think I even remember someone making one. Anyone know what size hole to drill for a 223Rem?
I would guess that one would just zero their calipers with the comparator in and then each measurement would be base of brass to ogive?
Seems like a tool worth having, only not for 16.99 + shipping, when it can be made for about a quarter.

Info is much appreciated,
Adam
_________________________
Adam


17HMR / 20gr Gamepoint
CZ 223 / 52gr BTHP
AR 223 / 45gr JHP
Mossberg 500 / 0000 Buck

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#1358222 - 08/26/09 06:24 AM Re: Homemade bullet comparator [Re: huntnfish08]
Evil_Lurker Offline
PM senior

Registered: 07/30/05
Posts: 6721
Loc: Oregon
Quote:
" Measures from the major diameter of a bullet to the case head, rather than from the bullet's tip to the case head "


Quote:
Anyone know what size hole to drill for a 223Rem?



The thru-hole is actually a little smaller I'd say, since I can see a chamfer on the mouth.
Try a .220 thru with a .010 chamfer. That should set right nice on the ogive.

Make 2 and I'll buy one for a half dollar.
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IdBob: You will be missed, my friend.

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#1358442 - 08/26/09 01:12 PM Re: Homemade bullet comparator [Re: Evil_Lurker]
pyscodog Offline
PM senior

Registered: 12/04/06
Posts: 5893
Loc: okla
Borrowed 2 brass nuts from work. Made one for a 223 and one for 6mm. I used a .195 hole in mine, for the 223. I really can't see what difference the size of hole matters as long as you stay on the ogive and measure only your bullets with it. May not be the same with a store bought one, but it works!!

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#1358456 - 08/26/09 01:30 PM Re: Homemade bullet comparator [Re: pyscodog]
Evil_Lurker Offline
PM senior

Registered: 07/30/05
Posts: 6721
Loc: Oregon
From reading the description, I believe they want to measure to the end (or beginning, depending on how you define it) of the ogive, which would be the first point on the bullet that is .224 dia.
But I could be wrong.
It wouldn't be the first time. laugh

But since a different profile would change the reading if you were measuring to something less than .224, it makes sense.

I don't believe you want to be "on the ogive" at all.
Try about a .223 reamed hole, I bet that's close to perfect and as accurate as the factory ones.

I wish I had one here, I'd measure them all and post the results.

Of course if you're measuring the same bullet and just using it as a reference to re-set your seating depth, yours will work just fine. If you're using it to set different bullet profiles to a distance off the lands, I think you're going to be inconsistent.
Does that make sense?
_________________________
Let's keep this a nice site where we help the ignorant.

IdBob: You will be missed, my friend.

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#1358564 - 08/26/09 04:41 PM Re: Homemade bullet comparator [Re: Evil_Lurker]
pyscodog Offline
PM senior

Registered: 12/04/06
Posts: 5893
Loc: okla
Evil- Measure and post when you get the chance if you will please. I will modify mine to the diameters. Thanks!!

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#1358687 - 08/26/09 07:48 PM Re: Homemade bullet comparator [Re: pyscodog]
Jack Roberts Offline
Admin/moderator

Registered: 05/10/01
Posts: 15764
Loc: Elko, NV formerly MD
My Sinclair comparator measures .217"

Jack
_________________________

"When the going gets tough, the tough get going."
"Yeah, to where the going's easier." Ben Bova

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#1358907 - 08/27/09 12:15 AM Re: Homemade bullet comparator [Re: Jack Roberts]
cornstalker Offline
Die Hard Member II

Registered: 02/09/08
Posts: 1702
Loc: Colorado
My Stoney Point measures .215"

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#1358925 - 08/27/09 12:41 AM Re: Homemade bullet comparator [Re: Jack Roberts]
Helipilotm Offline
Die Hard Member II

Registered: 11/10/07
Posts: 1169
Loc: Utah
Originally Posted By: Jack Roberts
My Sinclair comparator measures .217"

Jack


+1
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Aim small miss small!

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#1358927 - 08/27/09 12:43 AM Re: Homemade bullet comparator [Re: Evil_Lurker]
coopslave Offline
Junior Member

Registered: 05/20/09
Posts: 31
Loc: beyond the horizon
Originally Posted By: Evil_Lurker
From reading the description, I believe they want to measure to the end (or beginning, depending on how you define it) of the ogive, which would be the first point on the bullet that is .224 dia.
But I could be wrong.
It wouldn't be the first time. laugh

But since a different profile would change the reading if you were measuring to something less than .224, it makes sense.

I don't believe you want to be "on the ogive" at all.
Try about a .223 reamed hole, I bet that's close to perfect and as accurate as the factory ones.

I wish I had one here, I'd measure them all and post the results.


Hey All, Whats shakin ?

Actually, the diameter that you want is the dia of the bore,(the dia of the lands) the diameter of the grooves is the same diameter as the bullet and the bullet comes in contact with the lands first, so the bearing suface of the bullet begins at this point as well as this same point being the end of the ogive. i hope that makes sense, but for a .223 you need a hole dia. of .219 for .243 it is .237
hope that helps

Later

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#1359431 - 08/27/09 08:09 PM Re: Homemade bullet comparator [Re: coopslave]
ackleyman Offline
PM senior

Registered: 01/08/03
Posts: 5262
Loc: Hickville
Hey All, Whats shakin ?

Actually, the diameter that you want is the dia of the bore,(the dia of the lands) the diameter of the grooves is the same diameter as the bullet and the bullet comes in contact with the lands first, so the bearing suface of the bullet begins at this point as well as this same point being the end of the ogive. i hope that makes sense, but for a .223 you need a hole dia. of .219 for .243 it is .237
hope that helps

+1

I use the Davidson ogive gage that fits on the blade of the dial caliper, real nice with a thumb screw that comes off easy to change calibers. I believe that they are $12.95 from www.sinclairintl.com

They will last you a life time, pass them on to your son when you die. I don't mind investing in a tool that does not get worn out

One more real nice trick that you can use the Ogive gages for is measuring the headspace length of a case. For instance, if you use a 30 caliber ogive gage, you can slip it over the neck of a 243 and perhaps the 25 caliber case to measure how long a fired case is in your chamber. As you set the full lenght sizer, you can know how much you are pushing back the shoulder of the case.

Also, many shooters have found that when the bolt starts to get a little stiff to extract a case that if you "bump" back the shoulder of a case.002-.003, the bolt will close easily once again. This saves from full length sizing the cases which also saves on brass life and trimming. The Forester/Bonanza dies have the shoulder angle already cut in their neck sizers, so that you can "bump" the shoulder with the Neck sizer saving $ from spending money on expensive shoulder bump dies.

For example, my 25/06 loads are hot, and I need to bump the shoulder every firing, resulting in only having to full length size every twelth firing on Win Brass that I determined with my "test load" brass. I use the same system with the 243 and 22/250.

Good luck!


Edited by ackleyman (08/27/09 08:37 PM)

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#1359656 - 08/27/09 11:27 PM Re: Homemade bullet comparator [Re: ackleyman]
huntnfish08 Offline
Seasoned Member

Registered: 11/28/07
Posts: 342
Loc: Central Wisconsin
Thanks for the info, guys. I think I'll give this a try and see what happens. Gotta run to the hardware store and buy a couple brass nuts tomorrow.No jokes please.

Adam

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#1359718 - 08/28/09 01:29 AM Re: Homemade bullet comparator [Re: pyscodog]
Evil_Lurker Offline
PM senior

Registered: 07/30/05
Posts: 6721
Loc: Oregon
Quote:
Evil- Measure and post when you get the chance if you will please. I will modify mine to the diameters. Thanks!!


I don't have one to measure, or I would. From all these posts, though, I have enough information to build one. wink
I see what the trick is, you want the hole diameter to be .224 at the point that the chamfer meets the flat surface of the comparator. That way, you can zero out the comparator thickness and get the correct reading.
Understand that concept? wink
_________________________
Let's keep this a nice site where we help the ignorant.

IdBob: You will be missed, my friend.

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#1359893 - 08/28/09 11:56 AM Re: Homemade bullet comparator [Re: Evil_Lurker]
coopslave Offline
Junior Member

Registered: 05/20/09
Posts: 31
Loc: beyond the horizon
Originally Posted By: Evil_Lurker
Quote:
Evil- Measure and post when you get the chance if you will please. I will modify mine to the diameters. Thanks!!


I don't have one to measure, or I would. From all these posts, though, I have enough information to build one. wink
I see what the trick is, you want the hole diameter to be .224 at the point that the chamfer meets the flat surface of the comparator. That way, you can zero out the comparator thickness and get the correct reading.
Understand that concept? wink


No,no,no if you make the hole in your comparator .224, the same diameter of the bullet, the bullet might pass through it will certainly go to deep and your not going to get an accurate reading FROM where the Ogive ends. Its very simple, use the bore dia. .17cal. = .168 22cal. = .219 .243cal. =.237 .25cal. = .25 and so on, if you look at any chamber reamer drawing it will give you the Groove dia. which is the same diameter as the bullet and it will give you the BORE diameter this is the dimension you need to use to make a comparator for a given caliber. If you need more dimensions than i already listed ill look em up fer ya ! oh and if you want it accurate you need to hold those diameters to + or - .0005, I made a complete set from s/s and i made a set to measure the case shoulder length as well, nothin like being a machinist !

Do you understand that concept ? just funnin !

hope that helps later

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#1359918 - 08/28/09 12:53 PM Re: Homemade bullet comparator [Re: coopslave]
Evil_Lurker Offline
PM senior

Registered: 07/30/05
Posts: 6721
Loc: Oregon
Quote:
No,no,no if you make the hole in your comparator .224, the same diameter of the bullet..


Read it again:
Quote:
...you want the hole diameter to be .224 at the point that the chamfer meets the flat surface of the comparator.



That's correct, you want a chamfer from the thru-hole (< .224) to equal .224 at the plane of the front surface.
Now you can zero out the comparator thickness and get the right reading regardless of ogive shape.

.219 for the thru-hole would work fine, but it's not critical. The bullet gets stopped by the chamfer and never touches the thru-hole anyway. So if I varied the thru-hole by several thou. either way, it would have no effect. Seriously.

Quote:
...oh and if you want it accurate you need to hold those diameters to + or - .0005


The only critical dimension is the chamfer depth, actually. And yes, it's very critical that it equals the bullet body diameter when Z = zero.
That's what stops the bullet and is the only point where it will touch. As long as the thru-hole is large enough that it doesn't make contact with the ogive or tip (and prevent it from seating against the chamfer) it won't matter. Making the thru-hole bigger just reduces the depth of the chamfer before it quits cutting.


Quote:
nothin like being a machinist !

Do you understand that concept ?


Yeah, actually, I do. wink I'm also sure, being a machinist, if you read exactly what I'm describing, you're going to agree. If not, show me the error in my math.

Quote:
just funnin !


You better be! laugh

If I'm wrong on this, I'm going to be eating some major crow. wink











Edited by Evil_Lurker (08/28/09 01:00 PM)
_________________________
Let's keep this a nice site where we help the ignorant.

IdBob: You will be missed, my friend.

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#1360440 - 08/28/09 11:30 PM Re: Homemade bullet comparator [Re: Evil_Lurker]
coopslave Offline
Junior Member

Registered: 05/20/09
Posts: 31
Loc: beyond the horizon
Ok, im not sure how the chamfer that you describe got into play, but if you chamfer the top of the hole (.219 dia) the bullet is going to come in contact with an angled surface.

Different bullets start/end the ogive at different places but you want to Measure EXACTLY WHERE your BULLET IS GOING TO FIRST CONTACT THE BORE and that dimension is .219, In Reality I guess that it could be any size you like as long as the bullet doesnt pass thru and you dont care where the bullet meets the bore.
But your measuring it at the junction of the face (of the comparator) and a .224 dia chamfer isnt gonna help ya, because it all would depend on the angle of the chamfer, a shallow angle and it will meet the bullet further back than if the chamfer has a steep angle. So if You make the face perpendicular to the .219 hole there is no angle to contend with, the .219 will work for each and every bullet made in .22 cal, and it will give you the EXACT point that EACH first touches the bore. However depending on the profile of the bullet and the chamfer angle that you select
(45,60,82,90,100,118,120 degrees and there are more) Lord only knows if thats the point that it first comes into contact with the bore. now do ya see ? and yes i was only funnin and I will ignore the other part! Sorry no crow served here !

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