COAL Tolerance?

[Jarhead]

+ or - .005 ok or too tight / loose?

[Enfield47]

For what? If it's blaster ammo it won't make a difference.

[thospb]

Measured to the tip or the Ogive? Tips get damaged and irregular. The Ogive is more consistent. Either way, .005" is not much effect on pressure, about the same as .05 grain of propellant.

[Jarhead]

Measuring to tip, so it what what would be maximum tolerance for COAL. There has to be a point where it affects performance. Shooting out of WWII style replica Sniper Rifles so they are not tack drivers but I want ammo to be as consistent as possible.

[allenj]

The only way to get true consistant OAL measurement is to measure from the cartridge base to the ogive. If you do not have the equipment to do that your best bet is to not exceed your maximum COAL and don't worry about those that are shorter.

[Jarhead]

Best tool to measure at ogive?

My targeted COAL is 3.115 and I'm getting 3.110 - 3.120 measuring at tip

[J-cat]

OAL variance is caused by two factors: bullet POS-ness and case POS-ness. In the former, the bullets are made using inconsistent length jackets, multiple lots are mixed together, etc. The bullets are wider or narrower at the seater stem contact point and that causes different seating depths. Usually, you can get mass produced match grade bullets to seat within .007" of one another. So, .010" is decent.

The latter factor is inconsistent case neck tension. The harder the bullet is to seat, the longer the OAL. If neck tension varies, so will the OAL.

[thospb]

Hornady offers an attachment for calipers, a complete set for most caliber is about $30 or you can get the individual pieces too. The difference you are measuring is just on the tip of the bullet, your seater die is pushing against the Ogive. For people who want each round to be perfect, they will modify the tip with a Meplat uniforming tool. I am not up to that level of perfection yet.

[Jarhead]

Just reloading for MilSurp right now, but want to learn the Art along the way

[J-cat]

So you're using 7.62 NATO brass?

[Jarhead]

This last batch was 7.92mm for my replica K98 snipers, but my next batch will 7.62 for my M40 and M40A1 and I will be using Lake City brass with either 168 match.

[J-cat]

Sort them by year. LC13 is very heavy and will throw off your OAL due to the additional neck tension.

[ElDub1950]

So, a varying OAL of .006 for generic 9mm, 115 Lead Bullets and mixed range brass, sounds like it's not unexpected?

Light loads, so not concerned. Just new at it and not sure what tolerance I should expect.

[J-cat]

If you are running mixed brass with max loads, then you are running excessive pressures in some of those cases.

[rcschummers]

Good stuff here, pressures because of decreased oal can be a serious issue if you are loaded to max.

[BLR81]

Originally Posted by Jarhead

Best tool to measure at ogive?

My targeted COAL is 3.115 and I'm getting 3.110 - 3.120 measuring at tip

How did you come up with the 3.115 figure and how accurate do you think that number is?

You could be over analyzing this. A K98 Mauser even a new reproduction is not sub moa rifle. You might be trying to squeeze out more accuracy than that rifle is capable of.

And, unless you've actually got the prints of the chamber you could be way off the lands. The SAAMI OAL for an 8mm Mauser is 3.250.

I have a 43 1903-A3 with a OAL to the lands of 3.424", but the SAAMI OAL is 3.340". That spec was issued in 1979, almost 36 years after my rifle was built.

[allenj]

Best tool to measure at ogive?

You'll get different opinions of course on which comparator is best. The Hornady is probably the most popular, I use one made by Sinclair and like it.

[Jarhead]

Originally Posted by BLR81

How did you come up with the 3.115 figure and how accurate do you think that number is?

You could be over analyzing this. A K98 Mauser even a new reproduction is not sub moa rifle. You might be trying to squeeze out more accuracy than that rifle is capable of.

And, unless you've actually got the prints of the chamber you could be way off the lands. The SAAMI OAL for an 8mm Mauser is 3.250.

I have a 43 1903-A3 with a OAL to the lands of 3.424", but the SAAMI OAL is 3.340". That spec was issued in 1979, almost 36 years after my rifle was built.

Got my info from the Sierra Manual for 8X57 w/ 200 gr. HPBT C.O.A.L 3.115 ..........I'm probably being too anal I'm all ears though ........

[Jarhead]

Originally Posted by rcschummers

Good stuff here, pressures because of decreased oal can be a serious issue if you are loaded to max.

That was my concern, not knowing a tolerance on COAL, I measure the powder for every round ..........I'm not confident enough to load to Max either.

[BLR81]

Originally Posted by Jarhead

Got my info from the Sierra Manual for 8X57 w/ 200 gr. HPBT C.O.A.L 3.115 ..........I'm probably being too anal I'm all ears though ........

The info in the Sierra Manual is simply the standard the Small Arms and Ammunition Manufacturers came up with so all their rifles and ammo would be compatible. As with my rifle which is .120" longer than the SAAMI standard, yours may be no where need the lands at 3.115.

The Sierra Manual for 175gr BTHPs in my 30-06 is 3.285 which is .140" short of my rifles lands. Of course my rifle is an actual Military weapon built in 1943.

You really need to verify the true length of your chamber. There are many ways, and you can find them on YouTube. I recommend the split neck case to start. Which ever way you try, use a new bullet with every test. A bolt action rifle will have no problem jamming a bullet .020" into the lands. So, any attempt to check can damage the ogive on the bullet and give you a bad reading on subsequent tests.

The dole rod method is good also. One of my favorite YouTube sites does a good job of explaining how it's done. Link: https://www.youtube.com/watch?v=GmDi7v530Og

One last comment; when I was working up loads for my 1903-A3, I used the Sierra recommended COAL for my powder tests. After I decided on my load I started looking for the best COAL. I started at the listed COAL and went out .100" in .010" increments. I saw little or no overall improvement. A one and a half moa rifle is going to shot one and a half moa whether you .005" or .035" off the lands.

And remember, most of us aren't great marksmen. So, when you fire your 5 shot groups, and one is 1.5 and the next is 1.7 with a flyer or two, was it you or was it the load? I've fired the same load several times with the same COAL, and still wasn't certain.

There is also other issues to consider like consistent neck tension. With the recommended OAL my 175gr SMK is seated so that the BT is in the shoulder and the bullet is held the entire length of the neck. Set out to the lands, the BT which doesn't touch the neck in further out, and less then 1/2 of the neck is actually touching the bullet. Plus at the Lands the cartridge doesn't fit in the magazine.

Have fun, and remember it's not a job it's an adventure.

[Jarhead]

Originally Posted by BLR81

The info in the Sierra Manual is simply the standard the Small Arms and Ammunition Manufacturers came up with so all their rifles and ammo would be compatible. As with my rifle which is .120" longer than the SAAMI standard, yours may be no where need the lands at 3.115.

The Sierra Manual for 175gr BTHPs in my 30-06 is 3.285 which is .140" short of my rifles lands. Of course my rifle is an actual Military weapon built in 1943.

You really need to verify the true length of your chamber. There are many ways, and you can find them on YouTube. I recommend the split neck case to start. Which ever way you try, use a new bullet with every test. A bolt action rifle will have no problem jamming a bullet .020" into the lands. So, any attempt to check can damage the ogive on the bullet and give you a bad reading on subsequent tests.

The dole rod method is good also. One of my favorite YouTube sites does a good job of explaining how it's done. Link: https://www.youtube.com/watch?v=GmDi7v530Og

One last comment; when I was working up loads for my 1903-A3, I used the Sierra recommended COAL for my powder tests. After I decided on my load I started looking for the best COAL. I started at the listed COAL and went out .100" in .010" increments. I saw little or no overall improvement. A one and a half moa rifle is going to shot one and a half moa whether you .005" or .035" off the lands.

And remember, most of us aren't great marksmen. So, when you fire your 5 shot groups, and one is 1.5 and the next is 1.7 with a flyer or two, was it you or was it the load? I've fired the same load several times with the same COAL, and still wasn't certain.

There is also other issues to consider like consistent neck tension. With the recommended OAL my 175gr SMK is seated so that the BT is in the shoulder and the bullet is held the entire length of the neck. Set out to the lands, the BT which doesn't touch the neck in further out, and less then 1/2 of the neck is actually touching the bullet. Plus at the Lands the cartridge doesn't fit in the magazine.

Have fun, and remember it's not a job it's an adventure.

I just started prepping brass for 7.62 X51 for my M-40 & M-40A1 but the next batch will be 30-06 for a 1903 / 1941 USMC replica sniper plus my replica M-70 Sniper.

Now on the 7.62 I'm trying to duplicate the Black Hills Match which shot pretty good out of both, using BH once fired brass.

I'm having fun ........