OAL gauge

[juanito]

I just received my oal gauge today and did my measurements. I was loading per spec from Barnes website at 2.735 for a 7mm-08 120 grain ttsx.I made 10 different measurements with the gauge today and this is what I got.I am asking for suggestions from you guys.I was getting a 5 shot group about the size of a 50 cent coin (100 yards). I do realise that these rounds like a jump a bit but what would you all suggest to tighten the group up.It looks like I have some room to work with.

2.894
2.888
2.887
2.891
2.886
2.889
2.889
2.887
2.888
2.887
This is using the Hornady OAL gauge.Thanks for any responses..

[highpower790]

Start working from mag length to max length in .020 increments.

[juanito]

Will give it a try...Thanks

[FromTheGrave]

Honestly when using a OAL gauge like that you should be using a comparator to measure to the ogive.

Since I'm guessing you're not, you're going to have to go from the shortest oal that you measured, and use that as your reference point.

2.886" was your shortest.

Not using a comparator I wouldn't load over 2.876 just to be safe.

[juanito]

You are correct, I am not.But I will take that information. Thank you.

[JDay]

Yep. OAL gauge checks the headspace of the brass. You'll need another gauge and a modified shell to find the proper seating depth for your rifle.

[ar15barrels]

I just received my oal gauge today and did my measurements. I was loading per spec from Barnes website at 2.735 for a 7mm-08 120 grain ttsx.I made 10 different measurements with the gauge today and this is what I got.I am asking for suggestions from you guys.I was getting a 5 shot group about the size of a 50 cent coin (100 yards). I do realise that these rounds like a jump a bit but what would you all suggest to tighten the group up.It looks like I have some room to work with.

2.894
2.888
2.887
2.891
2.886
2.889
2.889
2.887
2.888
2.887
This is using the Hornady OAL gauge.Thanks for any responses..

Just as a control, measure the SAME CARTRIDGE 10 times.
How consistent are your measurements?

[juanito]

That was 10 attempts at measuring with the OAL gauge and a clean new bullet.

[J-cat]

Then your gage isn't worth a s-word.

[juanito]

Maybe I just put to much pressure then.Just looking for suggestions.I'll try again when I get home from work.Thanks

[JDay]

Make sure the brass is all the way in the chamber before you push the bullet into the rifling. And take your measurements using a bullet comparator.

[Metal God]

OAL gauge checks the headspace of the brass.

Are you sure about that . My understanding is a "OAL" gage messures the OAL and a "Head space gage" messures the head space . Setting aside the fact head space is a chamber measurement and can not be measured off a loaded cartridge . How would you measure head space using a OAL gage ?

OP
Those gages are a bit tricky to measure a consistent OAL . I agree with others that say it's best to use a comparator that measure from the O-give . http://www.midwayusa.com/product/231...ProductFinding . Bullets vary to much in length from base to tip to measure from case head to bullet tip . Depending on the bullets you can get a COAL measurement difference of a few thou to several thou .

I just did these measurements yesterday to help on another forum .

OK I just went and measured 10 or 41 rounds I loaded yesterday . These are 308 using 175gr SMKs

Head to O-give
1) 2.2075
2) 2.2065
3) 2.2070
4) 2.2075
5) 2.2080
6) 2.2070
7) 2.2080
8) 2.2075
9)2.2075
10) 2.2075

COAL = same cartridges in same order
1) 2.7880
2) 2.7930
3) 2.7990
4) 2.7960
5) 2.7930
6) 2.7960
7) 2.7990
8) 2.7955
9) 2.7875
10) 2.7915

That is .0015 swing from head to O-give and a .0125 swing in COAL . As you can see those rounds will have a pretty consistent jump to the lands but the COAL is all over the place and shows what I mean by OAL means close to nothing if measuring from the O-give .

Those were not seated with a competition seating die but a standard Redding seating die with micrometer that engages the bullet at .270 and my comparator engages the bullet at .300 .

NOTE : Yes I know they are loaded below minimum COAL . It's a long story as to why and not important to the point at hand

[FromTheGrave]

That was 10 attempts at measuring with the OAL gauge and a clean new bullet.

Do you mean using a different bullet each time? (I hope)

Or were you using the same bullet each time?

[JDay]

Are you sure about that . My understanding is a "OAL" gage messures the OAL and a "Head space gage" messures the head space . Setting aside the fact head space is a chamber measurement and can not be measured off a loaded cartridge . How would you measure head space using a OAL gage ?

Ignore that, I was drinking.

[ar15barrels]

That was 10 attempts at measuring with the OAL gauge and a clean new bullet.

It's probably one of those tools that uses calipers.
Calipers don't work well for people not super familiar with using calipers.