Sinclair OAL Bullet gauge

[rockstar.esq]

I saw this thing in a Sinclair catalogue. http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&type=store

It looks like a 3/4" nut that has a hole drilled in each flat side. Each hole is supposed to correspond to the ogive of a specific bore dia. They refer to this thing in the same area as their OAL gauges to determine how long a specific rifles chamber is. They claim that the overall length of a bullet is not consistent but that the length to the ogive is. This confuses me because they say the optimum OAL of your loaded ammo should be .005" - .010" shorter than the OAL of the rifles chamber. So if the ogive is the major diameter of the bullet, does this gauge determine how long the bullet is from the base to the end of the ogive? I hope this makes sense.

 

[Steve Smith]

"So if the ogive is the major diameter of the bullet, does this gauge determine how long the bullet is from the base to the end of the ogive?"

Yes. It will also determine the length of the entire cartridge from base to the ogive.

 

[Bullet]

Quote
This confuses me because they say the optimum OAL of your loaded ammo should be .005" - .010" shorter than the OAL of the rifles chamber.

When they say the OAL of the rifles chamber they mean fron the bolt face to the lands.

This means (on your loaded cartridge) from the base of your case to the ogive on your bullet. This is what Sinclairs gauge measures.

Sinclair is a great company with lots of great products for the precision loader.

 

[ocabj]

I use that exact bullet comparator from Sinclair. It's pretty handy. Definitely worth getting.

 

[Steve Smith]

You really need to use the Stoney Point Bullet Comparator and the OAL gauge together to understand how they work.

 

[esheato]

I just went through these questions and ended up buying both the Sinclair and Stoney Point products. On a daily reloading basis, I use the Sinclair "nut" more often.

While not cheap, buying both greatly helped my understanding and visualization of what I was measuring and why.

Ed

 

[Jon Coppenbarger]

I used mine the other day for 80smk's about 15 off and tonight I will load some Berger 75vld's 10 into.
Yes Steve I am speeding into the future.
And these are not for Marvin either!! LOL

 

[rockstar.esq]

Thanks for the answers guys. I especially like the reference to the Sinclair "nut". I have a further question along these same lines. I once heard that the tip of the bullet, the meplat I think it's called is actually less crucial to performance than the base of the bullet. I noticed when I look at photo's of Sierra bullets, the meplats aren't consistant. Given their popularity and reputation it makes me wonder why they wouldn't try to uniform them. I've seen tools designed for this purpose, any opinions?

 

[Ol` Joe]

I`ve seen write ups stating the metplat has litle effect on the bullets accuracy as you mention. I never paid much attention but, I haven`t noticed and problems with accuracy when shooting bullets that had damaged tips so there may be something to it.
The base is a different story. Thats the last part of the bullet to exit the barrel. The trouble is, as I understand it, if the base has a flaw the high pressure gas behind it will not flow out uniformly behind the bullet. The nick or flaw will allow gas to exit unevenly along the damaged side of the bullet unsetting it when it leaves the bore. This will cause the bullet to yaw or wobble and harms accuracy.

 

[donkee]

I am thinking about the Stoney Point doo dad that goes on your micrometer. As far as an OAL gauge, try this first, might save a buck or two.

http://www.larrywillis.com/OAL.html

About halfway down the page you'll see what I'm talikng about. It does a good job for me.