DIY Bullet Comparator

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DIY Bullet Comparator

Post by Oldbloke » 13 Nov 2018, 8:49 pm

For a long time now I have measured to the bullet tip. As we know not ideal as there is sometime makers variation or minor damage causing some variation in length. I've compensated by measuring a few and calculating an average.

Anyone considered making one. Just looks like a nut with hole drilled in it. They are about $60 to buy. Seems a rip off to me.

I figure a 5.5 mm for 224 and a 7.5 mm drill for 308 will be just about right.
Last edited by Oldbloke on 14 Nov 2018, 4:42 am, edited 1 time in total.
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Re: DIY Bullet Comparitator

Post by Kelsey Cooter » 13 Nov 2018, 9:05 pm

I reckon you'd be best off hitting up one of the blokes at your local engineering workshop to do a cashy, or if you know someone whos good on a lathe so its spot on the size.

I actually received my comparator in the mail today, I've been avoiding it because I also thought them to be a rip off but finally bit the bullet last week and bought a set. I've got to say after having a play with it tonight I'm really glad I stopped being a tight ass and bought one
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Re: DIY Bullet Comparator

Post by bladeracer » 14 Nov 2018, 2:05 pm

Oldbloke wrote:For a long time now I have measured to the bullet tip. As we know not ideal as there is sometime makers variation or minor damage causing some variation in length. I've compensated by measuring a few and calculating an average.

Anyone considered making one. Just looks like a nut with hole drilled in it. They are about $60 to buy. Seems a rip off to me.

I figure a 5.5 mm for 224 and a 7.5 mm drill for 308 will be just about right.


As KC said, it's just a hole. All that matters is that it is accurate enough to give you the same measurement consistently.
I bought the full Hornady kit with all fourteen caliber inserts, not a bad piece of kit at all.
The holes are 13-thou undersize, so .211" and .295". You ideally want the hole to match the rifling diameter so you are measuring the exact point the bullet meets the rifling.
If you don't have a lathe, drill the hole undersize, then hone it up to the required size with a split rod and a strip of emery cloth in a drill.

Or you could just buy the inserts and cut a slot in those so they fit your caliper without the holder.
https://www.ebay.com.au/itm/Hornady-Lock-N-Load-Bullet-Comparator-Com-224-Cal-Insert-222/162772287193

Frankly, the $68 is a steal in my opinion for the amount of time you'd spend making them for more than one caliber.
https://www.ebay.com.au/itm/Hornady-Lock-N-Load-Bullet-Comparator-Set-with-6-Inserts-B234/322694501516
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Re: DIY Bullet Comparator

Post by marksman » 14 Nov 2018, 3:45 pm

Oldbloke wrote:For a long time now I have measured to the bullet tip. As we know not ideal as there is sometime makers variation or minor damage causing some variation in length. I've compensated by measuring a few and calculating an average.

Anyone considered making one. Just looks like a nut with hole drilled in it. They are about $60 to buy. Seems a rip off to me.

I figure a 5.5 mm for 224 and a 7.5 mm drill for 308 will be just about right.


I did similar years ago before I got the hornady comparator, as long as it works for you :thumbsup:

but the good thing about the hornady comparator is it locks onto your vernier
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Re: DIY Bullet Comparator

Post by Oldbloke » 14 Nov 2018, 7:06 pm

"but the good thing about the hornady comparator is it locks onto your vernier"

Yeh agree. But I just checked and have a brass nut that looks the goods. I won't have a lot of use so I think I'll give DIY a crack.
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Re: DIY Bullet Comparator

Post by sungazer » 15 Nov 2018, 7:47 am

Hey Oldbloke probably no surprise but I made my own. I do have the advantage of having a lathe not that it is really necessary. I got a small bit of round SS bar stock and drilled it out using ever increasing drill size until I got to the correct sizes. It is best to go a bit undersized then hone it out with wet and dry. I made one end a bullet comparitor and the other end for case shoulders.
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Re: DIY Bullet Comparator

Post by Oldbloke » 17 Nov 2018, 7:15 pm

Done. Took about 15 minutes.
A 5.5mm & 7.5mm drill for 224 & 308.

Near enough.

DIY Compator.jpg
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Re: DIY Bullet Comparator

Post by Laddie1012 » 09 May 2019, 6:59 pm

Guys... thank you DIY and OEM aficionados for the various comments on the inspection tool.
The part that I struggle with is...what next?

I can cope with the concept that setting to the ogive will give the best grouping ( to a degree ) but am a bit unsure what the consensus is for what to do if the ogive position on the projectile varies.
Most dies set the projectile depth to allow for a COAL based on the tip location and in a perfect world that would be "set and forget" after the shooter determined the best off lands "jump" or "jam".
My question is after you have determined that you're between 5 or 15 thousandths off the magic ogive position but have the tip at your best "you beaut" normal COAL do you just re-seat deeper and batch or have some other practical techniques that work for maintaining a precision overall batch. I don't shoot that well but can pick up 1/2 MOA on longer ranges (600 yards plus) that can be directly attributed to higher velocity shots caused by higher chamber pressure due to the boat tail being pushed deeper in the case.

How do you manage things AFTER you've used your tool?
The next consideration is what happens when the comparitor shows you're too DEEP already?
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Re: DIY Bullet Comparator

Post by bladeracer » 10 May 2019, 3:54 pm

Laddie1012 wrote:Guys... thank you DIY and OEM aficionados for the various comments on the inspection tool.
The part that I struggle with is...what next?

I can cope with the concept that setting to the ogive will give the best grouping ( to a degree ) but am a bit unsure what the consensus is for what to do if the ogive position on the projectile varies.
Most dies set the projectile depth to allow for a COAL based on the tip location and in a perfect world that would be "set and forget" after the shooter determined the best off lands "jump" or "jam".
My question is after you have determined that you're between 5 or 15 thousandths off the magic ogive position but have the tip at your best "you beaut" normal COAL do you just re-seat deeper and batch or have some other practical techniques that work for maintaining a precision overall batch. I don't shoot that well but can pick up 1/2 MOA on longer ranges (600 yards plus) that can be directly attributed to higher velocity shots caused by higher chamber pressure due to the boat tail being pushed deeper in the case.

How do you manage things AFTER you've used your tool?
The next consideration is what happens when the comparitor shows you're too DEEP already?


Seat your bullets a little long, then run each round through the caliper and seat then individuaĺly so they're all the same. Any that are short just need a couple taps in the inertia hammer to pop the bullet out slightly, then adjust it as required.

It is also possible to make a seating die insert that perfectly matches the diameter of your rifling. A tip I saw recently was epoxy in the insert, some lube on the bullet, stick them together and the insert takes the shape of your ogive.

Personally, I find seating to ogive length to be an unecessary pain in the arse. Use quality bullets and seat to overall length to fit your magazine. Unless you're chasing extreme precision.
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Re: DIY Bullet Comparator

Post by Oldbloke » 10 May 2019, 4:41 pm

"A tip I saw recently was epoxy in the insert, some lube on the bullet, stick them together and the insert takes the shape of your ogive."

Pretty smart.
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Re: DIY Bullet Comparator

Post by Laddie1012 » 10 May 2019, 5:04 pm

Thanks bladeracer...
I'm using a Savage model 12 varmint 223 for F1 target, 1:9" twist so not the ideal rifle but it will give sub-MOA at 300 and 500 yds.
We use electronic targets and the velocity is recorded for each shot at the target...so it's a good guage but not a true chrono.
After measuring the lands and working a COAL 60.5mm for the projectile it groups well at 100 metres and my recent 300/500 targets show about a 60 fps velocity tolerance, the "fast" shots are high and slow are low by about 1/4 MOA each way. I put that down to brass tolerances and projectile mass variation; on 69 gn the manufacturer tolerance is around +/- 0.5 gn.
I have just started to batch weigh the projectiles...
Since my post yesterday I set up a 5.5mm die nut and a dial guage to measure variations from ogive to back end of the boat tail.
The boat tail is not dead flat but is within about 1-2 thousandths of an inch; the ogive to tail dimension varies up to 20 thou... with a fairly even spread between top and bottom tolerance so +/- 10 thou (0.25mm each way)
Thanks for the epoxy ogive insert tip.
First up I'll push the guaged projectiles to the different seat depth to suit the ogive and run them through. ..I'm guessing higher velocity on deeper seating so maybe will just click the elevation turret to suit.
Not that I rate it as edge of the seat reading but I'll report back.
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Re: DIY Bullet Comparator

Post by marksman » 10 May 2019, 5:55 pm

the problem I see doing this "A tip I saw recently was epoxy in the insert, some lube on the bullet, stick them together and the insert takes the shape of your ogive" is that you do not want to hug the bullet because of the differences in batches, this idea is only good for the bullet used to make the mould, you only want the polished ring edge touching, the main difference from a vld and standard ogive seater stem is that the vld is deeper so people think the same with comparators
this is why you should be measuring your projectiles into groups with very little fudge factor then when you seat them they will have very consistent oal with very little fudge factor, as long as your neck tension is good and consistent, I find that with some bullets eg... bergers I do check but they are very consistent always and I can be lazy not worrying about oal being consistent
if you dont want to have to worry about your oal jump large or jam, dont seat close to the lands
the idea of a DIY bullet comparator is a good one :thumbsup:
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Re: DIY Bullet Comparator

Post by bladeracer » 10 May 2019, 7:45 pm

marksman wrote:the problem I see doing this "A tip I saw recently was epoxy in the insert, some lube on the bullet, stick them together and the insert takes the shape of your ogive" is that you do not want to hug the bullet because of the differences in batches, this idea is only good for the bullet used to make the mould, you only want the polished ring edge touching, the main difference from a vld and standard ogive seater stem is that the vld is deeper so people think the same with comparators
this is why you should be measuring your projectiles into groups with very little fudge factor then when you seat them they will have very consistent oal with very little fudge factor, as long as your neck tension is good and consistent, I find that with some bullets eg... bergers I do check but they are very consistent always and I can be lazy not worrying about oal being consistent
if you dont want to have to worry about your oal jump large or jam, dont seat close to the lands
the idea of a DIY bullet comparator is a good one :thumbsup:


Yes, I probably should have qualified that but it seemed unnecessary in a thread specifically about ogive measurement. You don't want a mould of the bullet, you only need a faint ring of epoxy at the mouth of the insert so it just gives you the ogive.
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Re: DIY Bullet Comparator

Post by Stix » 10 May 2019, 8:30 pm

bladeracer wrote:
marksman wrote:the problem I see doing this "A tip I saw recently was epoxy in the insert, some lube on the bullet, stick them together and the insert takes the shape of your ogive" is that you do not want to hug the bullet because of the differences in batches, this idea is only good for the bullet used to make the mould, you only want the polished ring edge touching, the main difference from a vld and standard ogive seater stem is that the vld is deeper so people think the same with comparators
this is why you should be measuring your projectiles into groups with very little fudge factor then when you seat them they will have very consistent oal with very little fudge factor, as long as your neck tension is good and consistent, I find that with some bullets eg... bergers I do check but they are very consistent always and I can be lazy not worrying about oal being consistent
if you dont want to have to worry about your oal jump large or jam, dont seat close to the lands
the idea of a DIY bullet comparator is a good one :thumbsup:


Yes, I probably should have qualified that but it seemed unnecessary in a thread specifically about ogive measurement. You don't want a mould of the bullet, you only need a faint ring of epoxy at the mouth of the insert so it just gives you the ogive.

:thumbsup:
In which case, just drill it out the closest you can get to the bullet diameter without going over...

I just imagine if going to the lengths of making your own for say a 22, use a 5.5mm drill as OB says & then polish the rest out if you're so anal, without going over dia of course... :D
(Thats assuming you dont have steel turning equip like me).

Anyway...i just bought the Hdy kit...done...check measure the 20 cal 32 Zmax's match the number in my notes i always misplace for every batch i load & every fox still falls over as far as i shoot em...
Bonza... :thumbsup:
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Re: DIY Bullet Comparator

Post by TassieTiger » 10 May 2019, 8:42 pm

I honestly with I never bought one, I wish I’d never heard of the word - it had messed up what little k ow ledge I thought I had...
I bought the hornady comparator - I’ve found that many middle range projectiles can vary by .5 - .8mm in diameter and that completely can screw up OAL. It messes with your head...
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Re: DIY Bullet Comparator

Post by marksman » 10 May 2019, 10:02 pm

ImHO if you get the amount of bullets you are going to load to very much the same at the time you are reloading, 20 or 50 or whatever you will find that they will still shoot good even if they are 5 thou different than the last time you reloaded as long as they are the same this time, then next time may be a tad different to this time but get them the same this time, you may have to adjust your scope a bit because of a small difference but it wont be much

I am getting tired and I think you can tell :lol: hope you can understand what I am trying to say :thumbsup: :drinks:
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Re: DIY Bullet Comparator

Post by Laddie1012 » 10 May 2019, 11:59 pm

...just a quick note to Oldbloke.
Sorry steal the thread from a DIY comparitor guage discussion into something else.
I have made a DIY tool from a brass nut drilled with 5.5mm and it seems to work well.
My initial setup is just measuring the projectile before seating which I'm doing with a dial guage; I was worried that even a light micrometer touch might force the projectile taper in the hole too much and I figured the spring tension in a guage is light and constant.
I have a test calibration projectile that I drop in every few measurements and it gives repeatable +/-0.001" readings so the DIY tool does give accurate figures but no doubt some will argue that 5.5mm might not be the perfect bore...dunno. I was surprised at the ogive tolerance spread but I know for my rifle that 0.1mm makes a big difference to my groups.
So yeah, thanks for adding another few hours to my reloading time but if it lets me hit that X ring more often it's the cheapest reloading tool to help. :)
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