Which Hornady Case Comparator do I use?

[Jakal]

I am starting to reload for my Grendel. Not sure which case comparator to use.

In this link, it shows the D 400 in the first picture and then the B 350 in the second picture.

http://www.stu-offroad.com/firearms/reloading/headspace/headspace-1.htm

The B 350 seems to hit halfway between the base of the neck and the shoulder. The D 400 rides right on the shoulder.

I am trying to get my shoulder bump set up right the first time. The B 350 is for the 6MM PPC and the D 400 is for the .308 Winchester. I know the parent case is the 6 PPC but not sure which datum line to use on this.

Halfway between (B 350) or right on the shoulder (D 400).

I reload for other calibers (.223 and 458 Socom) in gas, but just starting on this one; so any help is appreciated!

[SG4247]

There is a sticky on the reloading page, that has a .pdf of the SAAMI drawing.

That SAAMI Grendel drawing shows headspace datum at .350" diameter.

.350" should work fine.

[Klem]

The B350 seems to be the closest to the datum line.

In mine the B350 readings are;

Unfired Lapua cases, 1.2040"
Fired Lapua cases (Lilja chamber), 1.2200"

From the website sticky;
SAAMI headspace Min, 1.2040"
SAAMI headspace Max, 1.2301"

That said, I use a rifle gauge to measure headspace. There's no settup and it's an easy visual glance. It gives not only longitudinal headspace (which is all the Hornady gauge measures) but also lateral headspace.

[Jakal]

I saw the reamer dimensions in Volume 1 of the handbook but missed that sticky, thanks for pointing it out! That would be good info to include in the manuals. My barrel is a Lilja AR740 profile.

I am working with Factory SST loads that have been fired once in my Grendel. I wanted to work the 300 pieces of Hornady brass first before starting 400 pieces of new Lapua brass. Don't mind screwing up the Hornady brass, need to get the bugs worked so I can start my charge ladders!

I'll update this with my Lapua measurements once I get rolling on those.

With the B350 I get the following measurements for once fired factory SST ammo....

New Factory 123grn SST load:: 1.213
Fired Case::1.220
Resized:: 1.208

So I am at .005 bump. I will stay there for now. Might change it later.

Thanks for the help.

[SG4247]

Yea, so the factory Hornady ammo is short. Way short, but they do this on purpose.

BTW, new Hornady brass is very short also.

What matters? Just that your bump is slightly less than your fired brass length by .003"-005". That fired length is determined by your actual chamber.

I actually use a .400" hole gauge to check my Grendel loads, and make sure that I push the shoulders all back about .003".

Works like a champ!

[NugginFutz]

+1

Bumping the case too much can lead to early case head separation by creating artificial excess head space. Once the round has been fire formed in your chamber, it has lengthened as much as it ever will. Full length sizing from that point of reference should bump the shoulder only enough to ensure the sized case allows the bolt to properly close and to go fully into battery. Bumping the case shoulder any more than that will only cause undue wear on the case by allowing it to stretch more than is necessary.

Is a .005" shoulder bump a catastrophe waiting to happen? No. But I would try to get that as close to .003" as you possible can. Certainly no longer than what you have.

[albireo]

With the B350 I get the following measurements for once fired factory SST ammo....

New Factory 123grn SST load:: 1.213
Fired Case::1.220
Resized:: 1.208

So I am at .005 bump. I will stay there for now. Might change it later.

Thanks for the help.

If your fired brass is 1.220, then a .005 bump for that barrel would be 1.215, no?

[SG4247]

If your fired brass is 1.220, then a .005 bump for that barrel would be 1.215, no?

Exactly.

I would resize the 1.220" fired brass to 1.217" (.003" set back) for my target rifles.

The hard part is making them all exactly 1.217". Some will be shorter, which I leave alone. The ones that are longer may need a little die adjustment and bump sized again.

So, I don't want any that measure longer than 1.217" because they may stop the action during feeding and not go into full battery.

[Jakal]

Thanks Albireo, I had the math right but used the wrong measurement.

SG4247 you are absolutely correct! So you use the D400 for your shoulder bump? That why I posted in the first place cause the B350 hits the shoulder in a position I was not used to seeing. The D400 hits right on the shoulder.

Referring to http://www.65grendel.com/forum/showt...endel-Drawings

I am curious about the max cartridge dimension that shows the 1.220-.007, is that where Hornady is getting the 1.213 measurement for factory loads?

If the max length on the chamber is the 1.230 and the min is the 1.220, then I would have to say my barrel's chamber is to the minimum end of the spec.

I'll reset my Redding die to 1.217, seat a bullet and trying chambering it up!

Thanks guys for not letting me screw my brass up!

[SG4247]

Thanks Albireo, I had the math right but used the wrong measurement.

SG4247 you are absolutely correct! So you use the D400 for your shoulder bump? That why I posted in the first place cause the B350 hits the shoulder in a position I was not used to seeing. The D400 hits right on the shoulder.

Yes I have a .400" hole in my gauge.

Referring to http://www.65grendel.com/forum/showt...endel-Drawings

I am curious about the max cartridge dimension that shows the 1.220-.007, is that where Hornady is getting the 1.213 measurement for factory loads?

Yes! Ammo manufactures will always make the ammo as short as possible, but in spec, to safely function in everybody's gun.

If the max length on the chamber is the 1.230 and the min is the 1.220, then I would have to say my barrel's chamber is to the minimum end of the spec.

Yes!

I'll reset my Redding die to 1.217, seat a bullet and trying chambering it up!

Thanks guys for not letting me screw my brass up!

The truth is it does not matter what diameter you use. You are creating a datum plane on the shoulder of your fired brass, created buy a thin round ring placed onto a straight taper. Where that plane exists... i.e. top, middle, bottom of the taper makes no difference as long as you use that same diameter gauge for measuring you fired brass and then on your re-sized brass.

Forget the factory ammo lengths, it is all too short (most is at a minimum of 1.213") as we know.

Forget the SAMMI dimensions, they are just a handy reference at this point.

All that matters at this point, is your chamber/your fired brass length.

Make your sized brass 3-5 thou shorter than your fired brass.

Now the bad part... Hornady and Laupa new brass is made to short for our liking.

This means we have to shoot it first to make it "fire formed" to 1.220"! Then we have to push it back .003"-.005" to give a "custom hand load" fit to our chambers.

Clear as mud?

[Drillboss]

This was a great post for me. I've always understood the concept of headspace, but never had the first clue how to measure it, except for go and no-go gauges.

Guess it's time to order some more stuff.

[kmon]

^^^^^^^^^^^
Spot on. Your chamber, your dimensions. As long as you are consistent in your measure and procedure then it will work for you and your rifle.

Ammo manufacturers make brass to the or near the minimum dimensions for a couple reasons, one it will fit all chambers, two a few thousandths less here or there adds up to a little less brass used. As long as it is consistent you will get consistency. Doesn't matter if it is the Grendel or another cartridge you will find those measurements are usually short on new brass from my experience.

[Drillboss]

I realized that a 35 cal bullet comparator works a just like a Grendel headspace comparator.

Too bad I realized that a couple minutes after I clicked "Submit Order".

[Jakal]

Glad we could help out, that's what the forum is for. Everybody helping one another out. I did settle on 1.216 shoulder for the Hornady brass and the 123 gr SST. Got 2 charge ladders ready , CFE223 & AR-Comp. 31 to 31.9 and 27 to 27.9 respectively, in 3 tenths steps. Just waiting on warmer weather to run them.