Determining OAL .308

FirearmsEnthusiast said:
This is an interesting thread - one other thought to add.

When using the Hornady tool and the modified case, the base-to-shoulder dimension may differ from the base-to-shoulder dimension of the brass you reload with.

So, you actually need 2 comparators - one to measure base to ogive (CBTO), and one (headspace comparator) that gives you a consistent datum point from case base to shoulder (CBTS).

Measure CBTS for both the modified case and your reloading brass. These are likely close but not exact. My modified case measures 1.619" CBTS. Most of my reloading brass is similar (example: 1.623)

For my Savage 10BA with Hornady 168gr BHTP Match projectiles, using the Hornady tool and modified case, base to ogive (CBTO) measures 2.208.

So, shoulder datum to ogive at lands = 2.208-1.619 = 0.589.
Less 0.015 (that's how much jump my rifle likes) = 0.589-0.015 = 0.574.

Reloading brass (example) = 1.623 + 0.574 = 2.197 CBTO (to ogive, not overall length).

Let us know your measurements using both the shoulder and the bullet comparators, if you have them.

Regards,
Peter
Click to expand...

My Ogive and headspace tools, are RCBS precision MIC.
For Ogive I don't use the dial on the tool, I just measure OAL of tool since it stops at Ogive, and this gives me a measure only I can work with to compare 2 rounds.

Since the precision MIC is not compatible with hornady OAL tool, I cannot get Ogive length where it stops.

My modified hornady case was 1.630'' headspace at shoulders.
I ran it in my redding body die, and bumped the shoulders back to 1.628'', like my loaded ammo, as my savage has exactly 1.630'' headspace on the spot.

The BTHP you are mentioning, I can run them longer (still ends up to be short), as the ogive is far from the bullet tip.
 
Chilly807 said:
I think you're missing part of the puzzle.. or maybe I am. Mine is a copy of the Hornady tool, and works great. You slip a bullet deep into the modified case, then fit the tool, complete with bullet and case, into the action until the case seats against the shoulder of the chamber. Then, while holding the tool in place, you loosen the clamp screw and use the rod to push the bullet forward until it stops against the rifling. Lock the clamp screw.
Slip the tool out of the action, push the bullet out with a cleaning rod or dowel (mine always stay in the barrel). Replace the bullet in the case and using a caliper measure either to the tip of the bullet or the ogive using a comparator. It's going to be more accurate measuring to the ogive, because that's where the rifling touches the bullet.
I don't understand how it could not work correctly using that process. Even if the modified case is a few thousandths off from a fired case it's going to be close. My tool was built using a case fired in my rifle, not resized.
All the factory rounds I checked were substantially shorter than my hand loads, showing a jump measurement of between 0.030"-0.090".
My hand loads chamber easily, showing no signs of being too long.
If your headspace was out to lunch or the shoulder on your cases was pushed back too far, that might cause problems. I don't have enough experience to say for sure.
My dies are set up to bump the case shoulder back about 0.001-0.002" from the fired dimension.
Click to expand...

My OAL tool is a red metal rod.
Threaded at the end, in which I screw the modified hornady case, which was shoulder bumped 2 thous to match my loaded cases.
The neck is loose, so a bullet could literally fall free in casing.
I have this plastic dowel which can be retained by a set screw at the rear end of red tool.
And right now, I am shoving the plastic dowel as hard as I can and jam bullet in the lands, as I am in disbelief from the measurments it spits out.

Yes I got a cleaning rod at the other end, if I want to go softly with the feel technique like they say in the manual, but that shortened the OAL even more.
 
Have you ever seen a savage jamming an SMK 175 in the lands at 2.780-2.785" OAL?
It may be normal and i may be overthinking this, but my friends with remingtons have jump and lack mag space to get closer
I feel like my method is not right to arrive to these results
 
Mystic Precision said:
Seat a bullet, jiffy marker, chamber... measure before and after. Keep shortening the seating depth until there are no or maybe 1 light mark on the bullet ogive. That is your zero point... 10 to 20 thou shorter... work up a load.

yes, it really is that simple.

Jerry
Click to expand...

That's how I did it for the first 50 years.

Then I bought a fancy tool. Have not used it yet. I still use a Sharpie...
 
Something doesn't seem right to me.
Most factory rifles like that are usually on the long side as far as I've seen.
If you have a decent micrometer measure the diameter of the bullets, sometimes bullets are on the large side. It may also have a tight throat, very worn out or out of spec reamer perhaps(hard to imagine but in high production anything can happen) but if its a bit tight and the bullet is a bit big, it may cause the interference, or other slight defect in there.
Those marks on the sharpie don't seem right to me, although you got a fair bit of it on there, maybe too thick. re-clean that chamber with some alcohol.

I use a gauge to push the bullet it and measure where it touches rifling, no issues on my end and very repeatable with a bit of care. I only do it 2-3 times to get my measurements for each bullet type, shouldn't take 50 tries.
 
SND said:
Something doesn't seem right to me.
Most factory rifles like that are usually on the long side as far as I've seen.
If you have a decent micrometer measure the diameter of the bullets, sometimes bullets are on the large side. It may also have a tight throat, very worn out or out of spec reamer perhaps(hard to imagine but in high production anything can happen) but if its a bit tight and the bullet is a bit big, it may cause the interference, or other slight defect in there.
Those marks on the sharpie don't seem right to me, although you got a fair bit of it on there, maybe too thick. re-clean that chamber with some alcohol.

I use a gauge to push the bullet it and measure where it touches rifling, no issues on my end and very repeatable with a bit of care. I only do it 2-3 times to get my measurements for each bullet type, shouldn't take 50 tries.
Click to expand...

Exactly my thoughts
Just ran my bullets on caliper, are all .308 dia, they're SMKs afterall
Before all these tests i cleaned chamber clean, and now that i'm doubting i cleaned it twice since.
308 chamber brushe, 308 chamber mop, i cant get any grit out anymore squeeky clean.

Since last post i ran sharpie test and hornady oal gauge test very carefully with the same bullet.
Now i get repeatable results with both methods, which is 2.750" OAL for that bullet, which i have kept ogive measurment for it

I swear this is driving me crazy!
 
So if your cartridge overall length is 2.75" and hitting the lands, what is your ogive measurement at?
 
The way i got to measure ogive isn't traditional
RCBS precision MIC, hash lines worn out on the side, so i measure both ends of the tool and it gives me repeatable results.
Measured that way, i get 2.698" on MIC tool
Just loaded 10 rounds and set them to 2.683" on mic tool.
All 10 loads give me precisely that number on mic tool, even if oal varies 5-6 OAL on both ends
 
MartyK2500 said:
Have you ever seen a savage jamming an SMK 175 in the lands at 2.780-2.785" OAL?
It may be normal and i may be overthinking this, but my friends with remingtons have jump and lack mag space to get closer
I feel like my method is not right to arrive to these results
Click to expand...

So you would prefer to have an ill fitted chamber and be miserable with mediocre accuracy????

Then you can spend a bucket of money replacing the barrel to get to where you are now???? Don't mean to sound harsh but that is what you are worrying about

If you were forced to use factory ammo, you have a legitimate beef.. but you are reloading so set it up to suit and enjoy.... The throat will move just fine with use but you can enjoy 3000rds of good shooting and have plenty of bearing surface to chase the lands as needed... this is all good stuff.

But if you are really unhappy with the current state, any gunsmith can extend your throat. Don't be surprised if they ask "Why?"

It is awesome that you are measuring and testing BUT trust your tools (or get different ones). This is reloading and these are rifles.... nothing is set in stone. Build ammo around best practises and work up a load to safe operating pressures. There is nothing more to it... and no two rifles need to agree.

Personally, I would work up a load and see what the barrel can give me. If this is one of the better Savage pipes, you could leave the range with a silly grin that lasts for days... and be the envy of your friends. But we can fix their rifles :)

Definitely use starting loads and work up slowly.

People spend a lot of money for these type of "custom" chambers.....

YMMV.

Jerry
 
MartyK2500 said:
The way i got to measure ogive isn't traditional
RCBS precision MIC, hash lines worn out on the side, so i measure both ends of the tool and it gives me repeatable results.
Measured that way, i get 2.698" on MIC tool
Just loaded 10 rounds and set them to 2.683" on mic tool.
All 10 loads give me precisely that number on mic tool, even if oal varies 5-6 OAL on both ends
Click to expand...

A couple of things.

First, forget about cartridge overall length measurements. Measuring the ogive is more accurate as bullet length varies from bullet to bullet. Measure cartridge OAL to ensure your rounds will fit in the magazine, that's it.
Second, if you are using a Hornady OAL gauge, it needs to be used with the correct size bullet comparator. Attach the comparator to your micrometer, close it and zero it out.

Now push a bullet up to the lands with the OAL gauge, then lock the screw. Measure the ogive with your zeroed out comparator.
As an example, I will do this with 10 bullets and if it keeps reading 2.260" I now know where my lands begin. If I want a 20 thou jump to the lands, I set my micrometer seating die so the ogive measurement reads 2.240". My cartridge overall length with a 175 SMK ends up at 2.825" ish (because like i said, measuring COAL is not as consistent as measuring the ogive).

 
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Mystic Precision said:
So you would prefer to have an ill fitted chamber and be miserable with mediocre accuracy????

Then you can spend a bucket of money replacing the barrel to get to where you are now???? Don't mean to sound harsh but that is what you are worrying about

If you were forced to use factory ammo, you have a legitimate beef.. but you are reloading so set it up to suit and enjoy.... The throat will move just fine with use but you can enjoy 3000rds of good shooting and have plenty of bearing surface to chase the lands as needed... this is all good stuff.

But if you are really unhappy with the current state, any gunsmith can extend your throat. Don't be surprised if they ask "Why?"

It is awesome that you are measuring and testing BUT trust your tools (or get different ones). This is reloading and these are rifles.... nothing is set in stone. Build ammo around best practises and work up a load to safe operating pressures. There is nothing more to it... and no two rifles need to agree.

Personally, I would work up a load and see what the barrel can give me. If this is one of the better Savage pipes, you could leave the range with a silly grin that lasts for days... and be the envy of your friends. But we can fix their rifles :)

Definitely use starting loads and work up slowly.

People spend a lot of money for these type of "custom" chambers.....

YMMV.

Jerry
Click to expand...

Believe me Jerry, if this really is what it is, i'll be very excited!!
I'm not disappointed it's going this way so far, just in a state of disbelief.
My 10TR cost me 680$, sold factory mag/stock/rail for 300$.
In my mindset, am looking for the problem as a 380$ barrelled action cannot have such a short throat.
Then again, savage might be set to surprise me.
I'll post results once i get them, lapua brass, varget measured with an fx120, cci br2, smk 175.
With all the reload tools you sold me.
If pipe is off we'll know soon enough!

I did get these results with varget measured in an rcbs chargemaster, regular win primers, 3x fired non-optimal processed FC brass, and hornady BTHP bullets at 2.800" oal, 100M



 
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J996 said:
A couple of things.

First, forget about cartridge overall length measurements. Measuring the ogive is more accurate as bullet length varies from bullet to bullet. Measure cartridge OAL to ensure your rounds will fit in the magazine, that's it.
Second, if you are using a Hornady OAL gauge, it needs to be used with the correct size bullet comparator. Attach the comparator to your micrometer, close it and zero it out.

Now push a bullet up to the lands with the OAL gauge, then lock the screw. Measure the ogive with your zeroed out comparator.
As an example, I will do this with 10 bullets and if it keeps reading 2.260" I now know where my lands begin. If I want a 20 thou jump to the lands, I set my micrometer seating die so the ogive measurement reads 2.240". My cartridge overall length with a 175 SMK ends up at 2.825" ish (because like i said, measuring COAL is not as consistent as measuring the ogive).

Click to expand...


My friend does have the hornady comparator, i will borrow it from him soon.
As mentionned, my RCBS gives me repeatable ogive results, good for me to compare between my ammo, just doesnt gives numbers i can compare with you guys.
Like posted earlier, if i load, "crappy plastic 2.800" magazine lenght", i'm still too long.
That savage got a funky pipe on it, either super cool/radical, either misformed and crap, we'll know soon enough!
 
I did a little bit of work/consulting with Savage when developing the concept of a target rifle. I pushed for an Obermyer chamber.

I no longer have any of the Savage prototypes, but I do have rifles with fairly fresh Obermyer chambers, and they touch Sierra MKs on the rifling at about 2.775".

They erode fairly quickly, so it wont be long before you are seating 2.800

A Remington is more like 2.900" Chamber designed by a lawyer...
 
Ganderite said:
I did a little bit of work/consulting with Savage when developing the concept of a target rifle. I pushed for an Obermyer chamber.

I no longer have any of the Savage prototypes, but I do have rifles with fairly fresh Obermyer chambers, and they touch Sierra MKs on the rifling at about 2.775".

They erode fairly quickly, so it wont be long before you are seating 2.800

A Remington is more like 2.900" Chamber designed by a lawyer...
Click to expand...


Cool information!
And good to know.
I have put this to rest, i will trust my data, load to it, and shoot it lots!

Edit, my round count is mid 500s btw
I have reason to believe throat may had been even shorter at start
 
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The Obermyer was designed to shoot the 147 NATO round. Hence it is short throated. Works very well with the Sierra 155's, which can be loaded close to the rifling. And it should also work well with the 175's, although, if I was designing a chamber for 175's, I would make the throat a bit deeper.
 
Just ran some groups.
2.735" OAL, looked friggin funny, but it's the first time i have no resistance closing the bolt.
At 2.800" i used to put a bit of muscle, even for factory ammo. First bolt gun so i had thought nothing of it back then. As i had shot 40 factory rounds for break in, so i never questioned reloads being the problem.

Using OCW and 3 shot groups, i like how my #6 load has some good groups higher and lower from it.
I guess that will be my load for now.
# 5 = 42.7 Varget = 0.59moa
# 6 = 43.0 Varget = 0.20moa
# 7 = 43.3 Varget = 0.52moa

Of all 10 groups, highest spread was 0.76moa

Loading 50x bullets rights now at 43.0gr varget
Tomorrow will be round 2 to test this load , 5 rounds per target, may this load be the right one so i can start going out further
 
I've been following your thread and was just going to ask what you ended up with, so thanks for the update. I have a Savage 10PC and I'm going through the same thing you are.

When I put a 175 SMK set over 2.800 in a fired case with a slight neck crimp the bullet is seated at 2.797 when I extract it. I seated again at 2.777 and sharpie'd, it shows some marks on one side of the ogive which I'm assuming is due to the extractor causing the bullet to be forced to the side as it extracts. Did you see this too with yours?
 
MartyK2500 said:
Just ran some groups.
2.735" OAL, looked friggin funny, but it's the first time i have no resistance closing the bolt.
At 2.800" i used to put a bit of muscle, even for factory ammo. First bolt gun so i had thought nothing of it back then. As i had shot 40 factory rounds for break in, so i never questioned reloads being the problem.

Using OCW and 3 shot groups, i like how my #6 load has some good groups higher and lower from it.
I guess that will be my load for now.
# 5 = 42.7 Varget = 0.59moa
# 6 = 43.0 Varget = 0.20moa
# 7 = 43.3 Varget = 0.52moa

Of all 10 groups, highest spread was 0.76moa

Loading 50x bullets rights now at 43.0gr varget
Tomorrow will be round 2 to test this load , 5 rounds per target, may this load be the right one so i can start going out further
Click to expand...

AWESOME... so glad the barrel really really wants to shoot

Remember to test further out to confirm that tuning for vertical is as good as it can be. Small changes in powder will change how the vertical groups.. and that has a profound effect at 1000yds

Enjoy

Jerry
 
recce said:
I've been following your thread and was just going to ask what you ended up with, so thanks for the update. I have a Savage 10PC and I'm going through the same thing you are.

When I put a 175 SMK set over 2.800 in a fired case with a slight neck crimp the bullet is seated at 2.797 when I extract it. I seated again at 2.777 and sharpie'd, it shows some marks on one side of the ogive which I'm assuming is due to the extractor causing the bullet to be forced to the side as it extracts. Did you see this too with yours?
Click to expand...

When doing the sharpie test
It would either form a perfect ring or nothing at all
If i was 1-2 thou from touching lands, i would then get only a small smear on one side
Does the 10PC also have a 5R barrel?
Myself, tested again before loading another 50 rounds at 2.735" tonight
Definately touching lands at 2.750"
 
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