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Measuring overall length with Ogive

This is a discussion on Measuring overall length with Ogive within the Ammunition forums, part of the M14 M1A Forum category; Hi, I'm going to start measuring my handloads, the OAL, from the bottom of the case to the Ogive. I'm using SMK 168gr. What is ...


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Old June 27th, 2011, 10:42 AM   #1
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Measuring overall length with Ogive

Hi,

I'm going to start measuring my handloads, the OAL, from the bottom of the case to the Ogive. I'm using SMK 168gr. What is the length I'm looking for? I have no idea how to do this.

Also, can someone suggest a good bullet comparator? I'm looking at products offered by Sinclair Internaitonal.

Thanks

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Old June 27th, 2011, 10:50 AM   #2
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Me either. That's why I just use the OAL as measured by a dial caliper. The fancy equipment doesn't generate smaller groups, just wastes time. At least for gas gun handloads.

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Old June 27th, 2011, 11:23 AM   #3
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Anything you get at Sinclairs will be top of the line, great products and service. I measure COAL with calipers as well and never had a problem.

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Old June 27th, 2011, 11:26 AM   #4
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My main concerns with auto loaders are consistent cartridge lengths and being able to fit the magazine. The slight differences in bullets, and especially match bullets, likely won't matter much.

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Old June 27th, 2011, 01:29 PM   #5
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In a magazine fed rifle the magazine does dictate the maximum length of the ammunition.

For the bolt target rifle what I do is to slightly "bump" the neck of a spent cartridge with the resizing die so that the bullet with some degree of effort will slip into the neck of the spent brass by hand and be held there fairly tight. Not so thight, however, that the bullet can't be pushed in or pulled out, with some effort, of the spent brass by hand. I press by hand a bullet into the slightly resized case long. I cycle this "dummy" round into the chamber with bolt closed on it so that the bullet is pushed into the case by the closing of the bolt. I then carefully eject the "dummy" round from the chamber and measure it to the ogive of the round with the Hornady Lock-N-Load Bullet Comparator on the vernier caliper. What I have now is an index round of the chamber overall length for this exact particular rifle.

Next I figure how much clearance I want from the ogive of the bullet to the lands of the barrel. What I use for my 300 Win. Mag. for example is .010" bullet clearance off the lands. For a semi auto I may use more clearance.

I then total resize and trim several brass cases and seat the bullets into them without powder or primers working on the seating depth to get me .010" less length measured form the index round off the ogive with the Hornady bullet comparator. This may take several adjustments of the bullet seating die which usually requires that I remove the bullet in this brass if I go too short for seating depth and keep going until I get it correct for what I want.

After a few trial tries and adjustments I'll end up with a dummy round of the proper seated depth of bullet that I'm looking for. I keep this round as a reference for my live reloads and put it in a safe place.

I've used the Hornady OAL guage set up for this but this method works better for me with more consistantcy in measurement of OAL.

You will usually also notice that after several hundred rounds down the pipe that the measurement that you originally took will be off as the COAL increases due to the errosion of the throat of the barrel.

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Old June 27th, 2011, 05:03 PM   #6
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This is the only way I have been loading for about 6 months or so and am very pleased, I am currently using the Hornady System and it's pretty simple to use.

First off get this with the proper sized case or make your own if you have a tap/die set

http://www.hornady.com/store/OAL-Gauges/

After you find the MAX OAL by using the above tool with your bullet of choice you would then take this tool and measure to the ogive:

http://www.hornady.com/store/Bullet-Comparator-Kits/

For my M1A my MAX OAL is 2.870"/2.290" (using a Nosler 168 CC) the 2nd number is what is called OGL but as hammonje pointed out you are limited by mag length for a semi-auto but you can by testing get closer to the lands by seating to MAX OGL and see how they cycle in the mag (they most likely won't) but you can then seat them back .010" at a time to see what it takes and see if it help your groups any, in my case it did help some.

The tools themselves are fairly straightforward to use and for about $75 you can get both of these or less with a limited number of inserts and you can also get the headspace kit which will help you by telling you how far you are bumping you shoulder back on the brass to get max case life

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Old June 27th, 2011, 07:51 PM   #7
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Hey MRB14,

How long are your loaded rounds for the .300 Win Mag if your bullets are only 0.010 off the lands?



TX200,

Unless you have a very strange seating die, you already ARE seating by the ogive.

- Ivan.

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Old June 28th, 2011, 09:53 AM   #8
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Hey MRB14,

How long are your loaded rounds for the .300 Win Mag if your bullets are only 0.010 off the lands?



TX200,

Unless you have a very strange seating die, you already ARE seating by the ogive.

- Ivan.
It works out that the original total cartridge length with the method I use for figureing COAL was 3.631". So giving myself .010" clearance to the lands, the dummy round I use for a guage total lenght is 3.621". So the rounds I reload come out to approx. 3.621" if you are measuring from head to tip of bullet. I'm using the 210 grain Berger target bullets that measure an average of 1.466" in total lenght. The AI magazines I use for this target rifle has a length of 3.632", so it works with the length of my ammunition @ 3.621". I beleive a bit of luck here for magzine fit.

Using the Hornady comparator tool attachment to vernier caliper, my dummy round I use for a guage measures 2.908" to ogive of bullet. Thats after subtracting an inch that the Hornady comparartor attachment takes up in length. This is the lenght that I zero my vernier caliper to measure check my reloads for this rifle. This is the measurement thats most important to me as IMO measuring off the ogive most repeatable accurate method to measure here. Also, the tip of my bullets are trimmed and re-pointed with a meplat trimmer and a bullet pointing die and even with the use of these tools theres still going to be some varience in overall bullet length due to the tips.

Disclaimer: These finished dimensions of this above described ammunition is for this specific rifle only and should not under any circumstances be used for any other rifle. It is out of sammi specs. and could be dangerous to use with another rifle of even same caliber.


Last edited by MRB14; June 28th, 2011 at 10:16 AM.
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Old June 28th, 2011, 12:44 PM   #9
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The "ojive nut" that sinclair sells for about $20 is a great tool for the serious loader. That and a caliper will give you the capability to seat at the lands, or 20 mils out, or anything else yer little heart desires.

I have spent hundreds of (enjoyable) man-hours doing "everything" possible to the make the most accurate ammo for my -14's. Checking weight, lengths, neck thickness, concentricity, balance, primer pocket dims, flash holes, etc. And when I think I have the best ammo, I shoot my best.

But then, all that effort is not visible on the target, for most of us, most of the time. But it's a hobby - enjoy it!

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Old June 28th, 2011, 01:03 PM   #10
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if you are going by COL or bullet length, it is imperative that your reference round be "uniformed" meaning the bullet (s) be all of the same length! If not you can chase yourself silly.

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Old June 28th, 2011, 01:39 PM   #11
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if you are going by COL or bullet length, it is imperative that your reference round be "uniformed" meaning the bullet (s) be all of the same length! If not you can chase yourself silly.

Laus Deo
overbore
Yes.
Thats why I only use one grain weight of the same part number of the same batch or Lot# of the same brand of bullets to load for the target rifle. Even at that, I weigh every bullet after trimming and pointing and sort or cull for weight if it exceedes 0.10 gr. differrence in weight. Also, so far, I've only used Nosler brass of the same part number and batch for this rifle. With the brass I still weigh and measure neck thickness with small ball mic and sort or cull accordingly. When I re-order more bullets it will be direct from Berger where they can guarantee the same batch or Lot#. Same goes for the brass when I finally run out due to brass no longer being able to be reloaded.

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Old June 28th, 2011, 01:52 PM   #12
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I've got a couple comparators but don't them much.

If you stuff a cartridge into the chamber with your thumb and it won't fall out when the rifle is tilted up, then the bullet is contacting the lands. Knowing this, you can take a dummy cartridge (just a normal sized case), seat the bullet out long, then dial it in a little at a time till it falls out of the chamber on it's own. The dummy and die are set right at the lands. Stick the dummy in a drawer.

When you want to come back to that setting say some other time, you can back the seating stem out, run the dummy up and then run the stem back down till it contacts. The die is now again set to zero jump.

Adding the desired amount of jump on your live rounds from there is simple. Seat the first bullet, measure COAL, then dial the stem down till the COAL get's shorter by x amount. X being the amount of jump.

It's a heck of a lot faster and more direct than dealing with gages and such and the seating die is now good to go.

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Old July 1st, 2011, 06:15 AM   #13
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Originally Posted by 30Caliber View Post
I've got a couple comparators but don't them much.

If you stuff a cartridge into the chamber with your thumb and it won't fall out when the rifle is tilted up, then the bullet is contacting the lands. Knowing this, you can take a dummy cartridge (just a normal sized case), seat the bullet out long, then dial it in a little at a time till it falls out of the chamber on it's own. The dummy and die are set right at the lands. Stick the dummy in a drawer.

When you want to come back to that setting say some other time, you can back the seating stem out, run the dummy up and then run the stem back down till it contacts. The die is now again set to zero jump.

Adding the desired amount of jump on your live rounds from there is simple. Seat the first bullet, measure COAL, then dial the stem down till the COAL get's shorter by x amount. X being the amount of jump.

It's a heck of a lot faster and more direct than dealing with gages and such and the seating die is now good to go.
Exactly how I did this for years before the fancy comparator gauges came along from Stoney Point (now owned by Hornady), but I will say that system has significantly sped up the process on many subsequent loads. The problem, mentioned here, is that the mag in your M1A may well not allow the bullet to be seated out where it's positioned for best accuracy.

IMHO, you should have at least (!!!) 0.020 left over room between a loaded round and the cartridge OaL you create on your loading bench. This will allow the rounds to always work within the magazine.

BTW, also remember that seating your bullet into the case further, after you've developed the max load, will surely raise chamber (and thus port...) pressure, altering muzzle velocity and all the other variables. Not to mention group size!

These interactions and complex relationships are partly what makes this so much fun, but you gotta keep it all in mind and balance! Safety is the most important factor, right?

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