Determining OAL .308

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MartyK2500

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I thought I had this covered, but after trying to determine OAL of 175gr SMKs i'm now confused.
Factory barrel/bolt, savage 10TR.
I have this tool called hornady OAL gauge. And I have read instructions carefully, got repeatable results, and have tried it at least 50 times for each bullet.
Also have the modified case to screw in it, which I have chambered with bolt in and made sure of headspace to replicate my lapua brass settings.

When using with hornady match BTHP, it determined my lands we're at 2.820'', which I found to be normal since loading manuals state 2.800''.
Then I purchased some Hornady ELD match, OAL tool gave me a reading of touching lands at 2.750'', and manual states 2.800'' again. I figured the bullets have inconsistency, since I have had inconsistent ogives with these ones.
Yersterday I got sick of trying to tune hornady bullets and went straight up to SMK 175gr. Loading books say 2.800'' OAL once again.
I tried with my Hornady OAL tool at least 50 times this morning, and came out with a reading of 2.760'' OAL average.

I find this abnormal, a factory savage should be running 2.800'' at least.
Also loaded a dummy round with lapua brass and 175 SMK, @ 2.800'' long, once extracted it still measured 2.800''.

Should I ditch hornady OAL tool and use another method?
 
It could be that the resistance you're feeling when using the OAL gauge is the bullet hitting the free bore and misleading you into think that you're hitting the lands? Use a Sharpie and colour the bullet and repeat. See if you notice any markings on the bullet from making contact with the lands.
 
The OAL of a cartridge with the bullet at the lands will be different for different bullets. Your results are normal.
 
Alpheus said:
The OAL of a cartridge with the bullet at the lands will be different for different bullets. Your results are normal.
Click to expand...
That i understand, the ogive dimension is different from bullet to bullet
But having a run of the mill savage hitting the lands before it gets to 2.800", seem very unlikely and abnormal to me
 
Alright
Everywhere i read there is this craze about finding thinnest walled mags to allow maximum lenght OAL
I find it unusual to be 50 thous behind the maximum a plastic mag no one wants because it won't allow longer than 2.800".

Will continue my research, but the el cheapo savage 10TR still got a few surprises for me it seems!

Edit : Btw, just loaded and pulled the bullet 15 times in a row.
Loaded a smk at 2.900"oal, chambered with bolt and extracted.
All 15 times my oal once extracted, we're all between 2.809"-2.811"
Think im safe to reload @ 2.800", and also thinking these hornady oal tools may not be optimal.
That savage sure got tight throat, either a defect or the economy gun shop got this one right
 
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I'm no old pro at reloading, but your results don't surprise me either. The OAL tool simply allows you to accurately position the bullet in the modified case at the position where it touches the rifling. I guess you could use the OAL tool by itself and measure from head to tip, but that's assuming each bullet is identical from tip to ogive. Bullet tips are easily deformed, ogives not so much.

I prefer to use the tool along with a comparator. Then you can seat your reloads, using that same type of bullet, to just short of the lands, thereby minimizing "jump". If one were truly paranoid, they'd check each bullet in the box, though I'm satisfied that they're close enough. Different lot numbers should be checked as well, there is some variance from batch to batch I'm told.

When I open a new box, I measure using 5 to 10 bullets from the box, then average the results. There's seldom more than 0.002" variance from bullet to bullet measuring from the case head to the ogive. Some of that is measurement error, it's why I check several bullets.

The modified case that Hornady sells is a bit of a compromise in itself. A case that was fired in your rifle and not resized before being made into an OAL tool would be ideal, in that it fits your chamber perfectly. Mine is home made, seems to work just fine.

Hornady sells a comparator, as does Sinclair for example. The Sinclair model is simply a hexagon nut with a different size hole drilled in each flat to accommodate different calibers. You either zero your caliper on the nut itself if you're using digital, or subtract the nut diameter if using a dial.

Some people angst over the hole diameter, others don't get concerned as long as it is close to the minor diameter of the rifling and should therefore touch the bullet close to the ogive diameter. You're measuring using the same bullets you're loading, so unless the bullet profiles are different from one example to another, you're going to be very close.

If I'm missing something here (entirely possible!), feel free to point it out, I'm learning as I go along.
 
MartyK2500 said:
Edit : Btw, just loaded and pulled the bullet 15 times in a row.
Loaded a smk at 2.900"oal, chambered with bolt and extracted.
All 15 times my oal once extracted, we're all between 2.809"-2.811"
Think im safe to reload @ 2.800", and also thinking these hornady oal tools may not be optimal.
That savage sure got tight throat, either a defect or the economy gun shop got this one right
Click to expand...

You might be on the tight side of the fence, I think Hornady recommends only 3-4 lbs of pressure at most to seat the bullet against the lands? It may take more than that to push the bullet into the neck, depending on your dies. Your bullets may be engraving slightly.
 
Yes i will need a comparator.
I got an RCBS precision MIC but it would still be handy.

Myself also learning as i go along.
Seems like 6 years ago i learned to reload pistol in one evening,
And rifle, been 3 months and still learning.
Good thing CGN exists since i do not know much people locally that reload rifle!
 
Chilly807 said:
You might be on the tight side of the fence, I think Hornady recommends only 3-4 lbs of pressure at most to seat the bullet against the lands? It may take more than that to push the bullet into the neck, depending on your dies. Your bullets may be engraving slightly.
Click to expand...

While doing loaded dummy round test, neck was very slightly resized using neck collet tool.
So very little resistance closing bolt.
Seriously losing trust in hornady oal tool unless an Flcass shooter tells me otherwise (they seem to be my benchmark for 308 reloading)
 
MartyK2500 said:
Alright
Everywhere i read there is this craze about finding thinnest walled mags to allow maximum lenght OAL
I find it unusual to be 50 thous behind the maximum a plastic mag no one wants because it won't allow longer than 2.800".

Will continue my research, but the el cheapo savage 10TR still got a few surprises for me it seems!

Edit : Btw, just loaded and pulled the bullet 15 times in a row.
Loaded a smk at 2.900"oal, chambered with bolt and extracted.
All 15 times my oal once extracted, we're all between 2.809"-2.811"
Think im safe to reload @ 2.800", and also thinking these hornady oal tools may not be optimal.
That savage sure got tight throat, either a defect or the economy gun shop got this one right
Click to expand...

I think you mean a short throat.... and you should consider yourself lucky. many spend alot of money to fix long throated factory barrels to get what Savage has given you.

Worry about OAL as it pertains to your mag... that's it. If single loading, set the bullet ogive 20 thou OFF the lands and work up your powder charge. If you can do that with your ammo fitting the mag, you should be very happy.

Yes, the OAL, case base to bullet tip, will be all over the map when changing bullets and even bullets within the box of bullets. Worry about the ogive and that varies very little in quality bullets.

Go shoot the rifle and I think you will be happy with the results.

Jerry
 
I have gotten some bad results actually because of this Jerry.
Was reloading my hornady ELD match to 2.800'' for load development, before getting my OAL gauge.
Once I saw that even in development it couldn't group better than .8-9 moa, I starting chambering and extracting without firing and my bullet would be pushed back in the casing.

The SMK 175s, so far I can chamber and extract and they will retain their 2.800'' OAL.


What is your method for checking the lands?
A tool or just loading way too long and force it in, extract, measure?

My tools at hand are RCBS precision MIC, hornady OAL gauge, and by meticulously reading instructions and playing around with both, results seem odd.
 
MartyK2500 said:
I have gotten some bad results actually because of this Jerry.
Was reloading my hornady ELD match to 2.800'' for load development, before getting my OAL gauge.
Once I saw that even in development it couldn't group better than .8-9 moa, I starting chambering and extracting without firing and my bullet would be pushed back in the casing.

The SMK 175s, so far I can chamber and extract and they will retain their 2.800'' OAL.


What is your method for checking the lands?
A tool or just loading way too long and force it in, extract, measure?

My tools at hand are RCBS precision MIC, hornady OAL gauge, and by meticulously reading instructions and playing around with both, results seem odd.
Click to expand...

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
 
I'm having the same results with my hornady OAL gauge. I'm currently loading 50 grain v max .223 for my Tikka T3. The hornady tool is telling me 1.830 to lands but factory loads are measuring 1.857 with the comparator (2.240 COL).
 
Skel said:
I'm having the same results with my hornady OAL gauge. I'm currently loading 50 grain v max .223 for my Tikka T3. The hornady tool is telling me 1.830 to lands but factory loads are measuring 1.857 with the comparator (2.240 COL).
Click to expand...

Yep, starting to think that tool is :bsFlag:

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...

Thanks Jerry! :dancingbanana:
 
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
 
In first picture,
Casing to the left @ 2.797" OAL
To the right @ 2.820" OAL

Second picture
Reused same casing to the left that was 2.797", and seated at 2.792"
Still got a few markings but very light

Am i on the right path?
If yes i could measure ogive on my 2.792" casing, and this would be the ogive measure for my rifle, with SMK 175 touching the lands
Still looks very short eyeballing it which still raises a doubt in myself

Edit : forgot a detail
Pulled a bullet and reseated extra long
When i do that it always come back to 2.820" exactly with heavy marking



 
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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.
 
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