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Bullet Comparator Question - Velocity - 02-25-2022
I am trying to find the seating depth using the Sinclair Bullet Seating Depth Tool, the measurement shows 1.4230 that's from case base to bullet base.
AR-15
Bullet: Speer 90gr TNT
Bullet Length: .8920"
Measurements
From case base to bullet base: 1.4230"
Add the bullet ogive: This is where the confusion starts, which one of the following numbers do I add to 1.4230" to get the right CBTO.
Hornady aluminum bullet comparator measurement of .3860" BTO
Sinclair steel bullet comparator measurement of .3110" BTO
There is .075" between the two gauges. Using the above measurements here is what I get.
CBTO 1.4230" + .3110" = 1.7340"
CBTO 1.4230" + .3860" = 1.8090"
With a COAL of 2.3150"
Where am I going wrong with these gauges?
Bullet Comparator Question - mdram - 02-25-2022
your overthinking it, what coal are you getting with tour calibers? what bast to ogive?
first time i load a bullet type i use a coal for 1 bullet only. after that i base everything off of base to ogive
Bullet Comparator Question - Velocity - 02-25-2022
mdram
I think your right, I am overthinking. It sounds easy reading the instructions and applying but where I get confused is the numbers are telling me the length from case base to the bottom of the bullet. And all I need to do is add the length of the bullet or the length of bullet base to ogive, that's my seating depth. Where I get confused is I haven't put the bullet in the case yet, how far does the bullet go in to the case what number should I be looking for?
Bullet Comparator Question - mdram - 02-25-2022
why does how far its in the case matter?
you could do
(bullet bto)-(cartridge bto-case length)
this should give the about of bullet in the case
tips can vary a bit
Bullet Comparator Question - SCJim - 02-25-2022
youtube has several how to videos that should clear up any questions
https://www.youtube.com/watch?v=3kL0HIgqqjU
https://www.youtube.com/watch?v=8H6WNbR87ZY
https://www.youtube.com/watch?v=lcrzSGtcnRA
Bullet Comparator Question - Velocity - 02-25-2022
mdram
Thanks
SCJim
Thank you, I'll go there and watch.
Bullet Comparator Question - Dt219 - 02-25-2022
Here is how I find distance to the lands. The aggravating part is finding the right piece of brass. Find a piece of brass thats been fired in that chamber that will hold a bullet, it doesnt have to be tight, if you dont have one you can use a Lee collet sizing die if you have one. Take that case swipe a little blue loctite inside the case neck, just start the bullet in the neck, then put the round in the chamber and let the bolt down easy, (might have to use forward assist ). Let it set 5 mins and pull it out. Measure how ever you wish, ( I do cartridge base to bullet ogive) That will give distance to lands with that particular bullet. I use the loctite to keep the bullet from being pulled out and staying stuck in the chamber when you extract. Works great for me
Bullet Comparator Question - Velocity - 02-25-2022
SCJim
Watched the vidoes, they are like the other 10+ videos I've watch. I even made me a gauge like the Hornady Length Gauge, and I use it. I may be mixing apples and oranges here and that may be the confusion. All my reading and video watching hasn't answered my question. If I want to back off the lands .020" or bump my headspace a .002" how can I do that when my gauged length is 2.3180" COAL or CBTO is 1.7420" using a 90 gr. projectile those measurements leave only .079" of projectile in the case. Is that all that's needed to go 600 yards? Here are my measurements with my home made gauge and also backed up by the Sinclair Bullet Seating Depth Tool within .002-.003":
Case fired once: 1.5050"
90gr. Projectile: + .8920"
COAL: 2.3970"
Gauge COAL: - 2.3180"
Projectile in case: 0.079"
Do those numbers seem right?
The cartridge is longer than the magazine.
Bullet Comparator Question - Velocity - 02-25-2022
Dt219
The brass I'm using for my process is a new piece of brass fired once from my chamber, I then drilled and tapped the brass 1/4-20, case measures 1.505" and then I use a overall length gauge.
Bullet Comparator Question - StoneHendge - 02-25-2022
I'm completely lost as to how or what you are measuring, but I just measured one of my 90 gr TNT rounds. COAL is 2.20" and I'm about 0.03" off the lands in a tight chamber. The base of the projectile is right around the bottom of the neck of my brass.
Bullet Comparator Question - Harpoon1 - 02-25-2022
StoneHendge Wrote:I'm completely lost as to how or what you are measuring, but I just measured one of my 90 gr TNT rounds. COAL is 2.20" and I'm about 0.03" off the lands in a tight chamber. The base of the projectile is right around the bottom of the neck of my brass.
I believe hes using the Sinclair measuring tool.
https://youtu.be/FYmVy-VhXgM
Bullet Comparator Question - Dt219 - 02-25-2022
You have got to be going about this in in the worse way possible. Sounds like you have confused yourself and us. It isnt hard. Try what I said. See if it helps you any. If the bullet is too loose in the case you have tapped just take some pliers or needle noses and lightly bent in the case mouth so it will hold a bullet.
For a 90gr tnt. My coal is 2.240 thats max on the lands. My cbto base to ogive is 1.730. Using the hornady bullet comparator
You need more than .079 in the case. I would not trust that
Bullet Comparator Question - Velocity - 02-26-2022
Well guys I don't know any other way to ask, only as I see it. I am trying to get a realistic measurement from my case base to my lands, but the COAL measurements are longer than my magazine. It's a new barrel and with these measurements it seems the chamber is to long, I don't know. I made a gauge something like the Hornady Length Gauge, I tapped a new fired case from my chamber and the length is 1.5050" I put a bullet in the case screw it on the gauge I place it in the chamber and run the rod up to the bullet and into the lands. See photo;
90gr. TNT
[ATTACH=CONFIG]18677[/ATTACH]
Bullet Comparator Question - Dt219 - 02-26-2022
What you have rigged up might work. Did you zero the calipers with the base attached ? Is the bullet moving in and out when after you push it against the lands and pull the measuring device out ? And next, several people on here cant get to their lands and still fit in the magazine. The purpose of that tool is to find where a particular bullet contacts the lands. I do not know if many that does load with the bullet into the lands. There might be but I havent ran across them on here
Bullet Comparator Question - Velocity - 02-26-2022
Here is a 123 SST
[ATTACH=CONFIG]18678[/ATTACH]
Bullet Comparator Question - Velocity - 02-26-2022
Dt219
I do not want to load to the lands I'm just trying to get a number so I can load about .020" off the lands. But it still won't fit the magazine. Thats all I'm trying to do is get a starting point.
Does the measurement of my 90gr TNT sound right. I don't know myself.
Bullet Comparator Question - Velocity - 02-26-2022
the gauge functions just like it's suppose to, the bullet fits snag also, no sloppy stuff and the measurements are backed by the Sinclair Gauge. It just seems they are to long for an AR-15.
[ATTACH=CONFIG]18679[/ATTACH]
Bullet Comparator Question - Dt219 - 02-26-2022
I will check what my 123 is when I get back home. Be late tonight
Bullet Comparator Question - Kosh65 - 02-26-2022
Are there the first handloads youve done for this barrel? Is it possible that your chambers throat is long?
Bullet Comparator Question - StoneHendge - 02-26-2022
Harpoon1 Wrote:I believe hes using the Sinclair measuring tool.
https://youtu.be/FYmVy-VhXgM
Well that's a silly tool.