Why do I need a Bullet Comparator?

04 December 2001, 05:19

I was looking through the Sinclair catalog, and these caught my eye. But, I can't understand why I would need one if I already have a Stoney Point Chamber-All OAL Gauge and a set of calipers. What's the point? I'm sure there is one, I just can't come up with it.

Thanks,
RSY

04 December 2001, 05:46

RSY

Well, upon further reflection, I think I've figured it out. I guess it simply eliminates having to check with the OAL gauge every time you change bullets for a rifle.

So, is the moral of the story "Borrow an OAL gauge, but buy a comparator?"

RSY

04 December 2001, 07:49

<Don Krakenberger>

As reloaders we'll never get accused of "under doing it!" I know someone will say it made a big difference for them to measure the distance to the olgive. But for me, and I do most of my testing at 300 yds,
every time I seat a bullet short by overadjusting the die it still goes right in there with the other bullets in the group.

04 December 2001, 09:33

<JCCD>

Bullet tips can vary in length a good bit and they can be mashed in a little on the tip so measuring to the ogive is a little more accurate when trying to keep the bullet to lands distance consistent.

04 December 2001, 09:43

Atkinson

I have never felt any great need for one.

------------------
Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

05 December 2001, 05:37

Bob338

If the items you are talking about are what I think they are, I have both. They both do the same thing. The bushings for the Stoney Point ARE comparators. The hex tool from Sinclair is handy only for a quick bullet measurement if you have only one caliper and don't want to attach the SP to it for that quickie. I dedicated one caliper to SP and never use the Sinclair comparator anymore.

05 December 2001, 07:28

RSY

Bob:

I think both items you're referring to are comparators. The OAL gauge is the rod-type instrument with the threaded case on one end, where you insert your bullet of choice to see at what seating depth it hits the rifling on your rifle of choice.

Again, it seems like two ways to skin the same cat.

Thanks,
RSY

05 December 2001, 11:39

Atkinson

A piece of wooden dowl is the most accurate, but one must do a fit on each brand of bullet..but it's cheap at 13 cents and last two life times.

------------------
Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

05 December 2001, 13:41

<goneballistic>

quote:
Originally posted by RSY:
Bob:
I think both items you're referring to are comparators. The OAL gauge is the rod-type instrument with the threaded case on one end, where you insert your bullet of choice to see at what seating depth it hits the rifling on your rifle of choice.
Again, it seems like two ways to skin the same cat.
Thanks,
RSY

Take 10 or so loaded rounds. Measure case head to bullet tip for your OAL, each one. You will most probably get several slightly different OALs from that group.
When you use your SP OAL gauge to get an OAL, then record that Max OAL (to the tips) for that particular bullet, then you use that figure for future reference, you would more than likely as not be a little off, because of the variance in bullet tips. Measure the OAL using the comparator, from the Ogive, record that measurement, it will be the same each time, as long as you are using the same unchanged bullet style.
As has been already alluded to, this is splitting a hair, especially for hunting loads. But, for fine competitive accuracy, or for someone who wants to see how accurate they can get for their own satisfaction, both tools are a good investment.

05 December 2001, 14:27

<Zeke>

Mr Atkinson,
Could you go into more detail about the wooden dowel method you mentioned?
Thanks
ZM

06 December 2001, 04:36

John Frazer

I use a comparator for all my COL measurements -- because I nearly went nuts trying to adjust my bullet seating die to give consistent lengths when measuring off bullet tips.

06 December 2001, 09:47

<monyhunter>

Yes, Ray, could you explain how you use a wooden dowel?

The only thing I have ever done is use a black "sharpie" marker on the ogive of the bullet. I start out seating the bullet long, then work my way down until it is 1/4 turn past the last time I could see rifling marks on the bullet. Not very scientific, but then again I have lots to learn.

I still don't get how people can be so accurate when seating bullets that they can varry them from .01 to .05. I just use 1/4 turn and I have no idea how far that is. Guess I should meassure next time.

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Monyhunter

06 December 2001, 10:08

Bob338

The wood dowel method (or a cleaning rod,) measures the tip of the bullet for the COAL. It isn't accurate because there is a difference in the distance from the ogive to the tip on all bullets, even those of the same manufacturer and lot number.

What you do is put the dowel into the muzzle with the bolt closed. Mark the dowel. Then, put a bullet into the lands. Put the dowel in again and mark again. The difference is the COAL with the bullet jammed. You get significant variance of as much as .015" depending on make of bullet. You also get a variance on measuring the marks on either your dowel or rod. On a cleaning rod you can put one wrap of masking tape and mark that and save yourself the pennies for buying a dowel.

06 December 2001, 10:53

RickF

It will make you feel better about your handloads.

Without meaning to pick on Swift, I loaded some 200 grain A-Frames for my 300Wby on the weekend. The variation in OAL was atrocious, upwards of 0.025". However, using the comparator to measure the variation in seating depth at the bullet ogive, they were within 0.004". And the variation in ogive IS the one that matters.