OAL and Comparator Has My Head Ready to Pop

[BamaAl]

Just got a comparator and a Hornday OAL gauge in the mail today. Naturally I couldn't wait to play with my new toys and got straight to work. But these measurements have me so confused I don't know whether to scratch my watch or wind my butt. HELP!

Reloading 308 in a savage 11 long range hunter with a Bartlein barrel. COAL measures at 2.775 with up to 2 thousnadths variance either way using SMK 175 HPBT.

The comparator measured to the neck right at 1.624 very consistently on fire formed cases. Then I used the OAL to measure to the ogive when seated to the lands. 16 tries had a 2.4015 avaerage. Low was 2.39 and 2.413 was the high. Having never done this before I could easily chalk up the high and low to learning to do this. So that would mean I should try to get 2.382 to the ogive when I load.

Now here is the part making my head pop. Reloaded rounds, full length sized, measuring a COAL of 2.775 only had an OAL of 2.196 to the ogive. That means I would have to increase my COAL by .184 to 2.939 to hit what the OAL gauge is telling me. No freaking way. If I load to a COAL long than 2.79 the bolt is hard to close and at 2.8 forget it.

Any idea what the heck is going on? By the way, my rounds as they are will group at sub 3/4 MOA at 100 yards. If I was really jumping 0.18 inches to the lands wouldn't I see groups the size of Texas?

 

[oldfatguy]

Re: OAL and Comparator Has My Head Ready to Pop

Many factory rifles are throated by lawyers. Looks like your Savage was as well. I have 3 Remmy 700s that are realy long in the throat. If I loaded to the lands I'd have to use Scotch tape to keep the bullets from falling out.

Depending on what bullet you are loading, a long jump isn't necessarily a bad thing.


OFG

 

[ChrisGarrett]

Re: OAL and Comparator Has My Head Ready to Pop

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BamaAl</div><div class="ubbcode-body">Just got a comparator and a Hornday OAL gauge in the mail today. Naturally I couldn't wait to play with my new toys and got straight to work. But these measurements have me so confused I don't know whether to scratch my watch or wind my butt. HELP!

Reloading 308 in a savage 11 long range hunter with a Bartlein barrel. COAL measures at 2.775 with up to 2 thousnadths variance either way using SMK 175 HPBT.

The comparator measured to the neck right at 1.624 very consistently on fire formed cases. Then I used the OAL to measure to the ogive when seated to the lands. 16 tries had a 2.4015 avaerage. Low was 2.39 and 2.413 was the high. Having never done this before I could easily chalk up the high and low to learning to do this. So that would mean I should try to get 2.382 to the ogive when I load.

Now here is the part making my head pop. Reloaded rounds, full length sized, measuring a COAL of 2.775 only had an OAL of 2.196 to the ogive. That means I would have to increase my COAL by .184 to 2.939 to hit what the OAL gauge is telling me. No freaking way. If I load to a COAL long than 2.79 the bolt is hard to close and at 2.8 forget it.

Any idea what the heck is going on? By the way, my rounds as they are will group at sub 3/4 MOA at 100 yards. If I was really jumping 0.18 inches to the lands wouldn't I see groups the size of Texas? </div></div>

First of all SMKs can stand a jump, but .180" is a nice jump!

Secondly, there is a learning curve to the SP/Hornady OAL gage.

I'm not going to type it all out again, but my method is to take 3, or 5 bullets, mark them 1-3, or 1-5 and measure each 3 times.

Each time I measure a bullet, I have the tool oriented at either the 12:00 position, 3:00 and 9:00, relative to the thumbscrew. Thumbscrew up is 12:00. This matters, since chambers aren't perfect and neither are the modified cases.

I add these 3 measurements per bullet together and divide by 3, getting an average for bullet one. Repeat for bullets 2-3, or 2-5, using the 12:00, 3:00, 9:00 spacing.

When you're done measuring all of your 3, or 5 bullets, average those 3, or 5 'averages' together for your master average.

Keep your numbers on a piece of paper and keep the bullets in a ziplock baggie, so you can check throat errosion down the road.

Moving on...I'm having trouble understanding your problem?

As for the comparator vs. your throat size, you do know that they're not the same diameter, right?

That comparator might have an opening of .300" and your leade/throat might have an opening of .303" where the bullet actually begins to contact the rifling and forward movenment ceases.

For translating things to paper, I use my above method to get my 'master average', which is COAL. I'll then seat a bullet into a charged case to that COAL and then take my bullet comparator and measure the OAL. Since it's pretty easy just to dial in the COAL when adjusting the seating depth, I don't sweat ogive mesurements too much, but record them in my journal just to have the info.

If you then measure the loaded rounds for COAL, you'll get your usual variation, but if you measure them all using the SP/Hornady bullet comparators, you'll see that they're much more consistent.

How you label it within your reloading notes, is up to you.

Don't forget, that you have your anvil that needs to be accounted for and measured for height and I also put a witness mark on my anvil and all of my comparators and headspace bushings, so when I insert them, I cinch them down in the same spot each and every time.

They're machined by man and have some variations which a typical caliper can measure.

Chris

 

[Down South]

Re: OAL and Comparator Has My Head Ready to Pop

I have a factory TC Icon Precision Hunter 308 that I hunt with that I jump .140 to the lands with Berger 168 VLD's. It shot pretty good seated a lot closer to the lands but even better when jumped a long way from the lands. I never could try it jammed as the bullet was seated too far up in the neck. The good thing about jumping is that it fits in the mag easily.

 

[SSC]

Re: OAL and Comparator Has My Head Ready to Pop

Couple of things to look at:

1. variation in primer setting depth
2. variations in how you are measuring the round (wiggle it till it bottoms out)
3. make sure you are using the correct bushing of the comp tool
4. make sure you are testing multiple bullets multiple times
5.zeroing out the calipers once you loaded the tool. mine are always .003-.010 off each time
6. OAL only matters because after a certain point they no longer fit in the mag box other than that always use Ogive measurement.


just a few things to think about

 

[Fuzzball]

Re: OAL and Comparator Has My Head Ready to Pop

"If I was really jumping 0.18 inches to the lands wouldn't I see groups the size of Texas?"

No. Obviously. Seating to the lands is just web BS, that may work best but most likely it won't.

 

[SSC]

Re: OAL and Comparator Has My Head Ready to Pop

You can have good groups while jumping a pretty good distance. it is just not an ideal situation. Some bullets are finicky when it comes to seating depth, typically the VLDs, and others shoot just about anywhere.

 

[psubond]

Re: OAL and Comparator Has My Head Ready to Pop

sorry don't want to hijack just quick question
how tolerant are smk 168s (using them for short/mid range) for jump almost have powder dialed in was looking at jump next.

 

[ChrisGarrett]

Re: OAL and Comparator Has My Head Ready to Pop

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Psubond</div><div class="ubbcode-body">sorry don't want to hijack just quick question
how tolerant are smk 168s (using them for short/mid range) for jump almost have powder dialed in was looking at jump next. </div></div>

We have to be specific here, or mostly so. How far are you jumping them?

Federal GMM ammo is seated to 2.800 +/- .005", IME. If you're shooting a long throated Remington, you might be jumping them .100", .150", or even more? That ammo shoots well for a lot of weapons out there.

SMKs are tangential ogive bullets and as such, they can jump a bit, but it's never a good thing to send a bullet into a longer 'free space' before it hits the rifling, if you can help it. Things can go crooked, so to speak.

VLD bullets, like Bergers, AMAX, and others, are a secant ogive and 'prefer' to be touching, or jammed into the lands, because of their inherent sharp 'nose cone' shape.

Tangential bullets should be fine anywhere out to .025", or even .050", if you have the ability to control this parameter.

I did a test of the new .338 Berger 250gr Hybrids and in my post in this forum, my loads just barely off the lands, fared worse than the ones that were jumping a small and moderate amount, so getting close to the lands, or into the lands, isn't a panacea.

Chris

 

[Fuzzball]

Re: OAL and Comparator Has My Head Ready to Pop

"...it's never a good thing to send a bullet into a longer 'free space' before it hits the rifling, if you can help it. Things can go crooked, so to speak."

Never is a long time; I question the accuracy of your statement. It seems to be much more complicatied than 'things can go crooked."

 

[psubond]

Re: OAL and Comparator Has My Head Ready to Pop

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChrisGarrett</div><div class="ubbcode-body">

We have to be specific here, or mostly so. How far are you jumping them?

Federal GMM ammo is seated to 2.800 +/- .005", IME. If you're shooting a long throated Remington, you might be jumping them .100", .150", or even more? That ammo shoots well for a lot of weapons out there.

SMKs are tangential ogive bullets and as such, they can jump a bit, but it's never a good thing to send a bullet into a longer 'free space' before it hits the rifling, if you can help it. Things can go crooked, so to speak.

VLD bullets, like Bergers, AMAX, and others, are a secant ogive and 'prefer' to be touching, or jammed into the lands, because of their inherent sharp 'nose cone' shape.

Tangential bullets should be fine anywhere out to .025", or even .050", if you have the ability to control this parameter.

I did a test of the new .338 Berger 250gr Hybrids and in my post in this forum, my loads just barely off the lands, fared worse than the ones that were jumping a small and moderate amount, so getting close to the lands, or into the lands, isn't a panacea.

Chris

</div></div>

thanks for the explination. according to the comparator and oal gauge my current seating depth (right around 2.8 oal or 2.23 to ogive is about .9-1.0 off the lands but i can't load that long or the damn bullet will be falling out of the case, i might just have to leave it alone or if i do push it up probably won't be able to go more than .025-.03.


***disclaimer***
my numbers might be off atm i don't have my notebook in front of me...yay for keeping a laptop in the bathroom! screw magazines.

 

[JoshcBoucher]

Re: OAL and Comparator Has My Head Ready to Pop

I'm wrestling with the same problem. I loaded some old 125 gr.spitsers. The jump was horrible. They shot bug holes, at 100. Into the wormhole!

 

[BamaAl]

Re: OAL and Comparator Has My Head Ready to Pop

Well, today I went out and tested loads with Lapua for the first time. The load that did best measured .62" at 100 yards. And that was with the jump. So next I'm going to play with the seating depth to see what happens with the measurements the OAL gauge indicated. We'll see what happens.

 

[ChrisGarrett]

Re: OAL and Comparator Has My Head Ready to Pop

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Psubond</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChrisGarrett</div><div class="ubbcode-body">

We have to be specific here, or mostly so. How far are you jumping them?

Federal GMM ammo is seated to 2.800 +/- .005", IME. If you're shooting a long throated Remington, you might be jumping them .100", .150", or even more? That ammo shoots well for a lot of weapons out there.

SMKs are tangential ogive bullets and as such, they can jump a bit, but it's never a good thing to send a bullet into a longer 'free space' before it hits the rifling, if you can help it. Things can go crooked, so to speak.

VLD bullets, like Bergers, AMAX, and others, are a secant ogive and 'prefer' to be touching, or jammed into the lands, because of their inherent sharp 'nose cone' shape.

Tangential bullets should be fine anywhere out to .025", or even .050", if you have the ability to control this parameter.

I did a test of the new .338 Berger 250gr Hybrids and in my post in this forum, my loads just barely off the lands, fared worse than the ones that were jumping a small and moderate amount, so getting close to the lands, or into the lands, isn't a panacea.

Chris

</div></div>

thanks for the explination. according to the comparator and oal gauge my current seating depth (right around 2.8 oal or 2.23 to ogive is about .9-1.0 off the lands but i can't load that long or the damn bullet will be falling out of the case, i might just have to leave it alone or if i do push it up probably won't be able to go more than .025-.03.


***disclaimer***
my numbers might be off atm i don't have my notebook in front of me...yay for keeping a laptop in the bathroom! screw magazines. </div></div>

I'm a little confused? Did you have your barrel short throated for any particular reason? I think you said that you have to load to 2.790" for the bolt to close with the 175 SMKs and at 2.800", you can't close it, correct?

Are you sure that the bullet is jamming the lands at 2.800" and it's not just your shoulders needing to be bumped back a bit more?

That seems like you're really short changing yourself, since you're losing case capacity by seating deep.

You really need to go by the 'OAL' gage, as all that matters is where the bullet is seated when it hits the lands. An arbitrary hole in a SP/Hornady bullet comparator, may, or may not, mimic the actual bore dimension after the throat.

The bottom line is is that 2.800" is a no-go (so far) in your rifle when using the 175s and ehhh, a little bit of wiggle room is always a good thing and you don't have much, if any.

Chris