COAL Of Loaded Ammo?

[antelopedundee]

The other day I loaded 10 rounds of 6.5 - 06 ammo using Barnes 120 grain TSX BT bullets. The Redding #5 bullet seater plug was used to seat them. COAL of the loaded rounds varied by as much as 0.008 among them. AFAIK all copper bullets are machine made and not cast so one should expect them to be fairly consistent in length. I took 10 randomly selected bullets from the same box and they varied from 1.2500 to 1.2570 or a difference of 0.007. I'm not sure exactly where for each bullet that the difference arises. I'm assuming that the seat plug contacts the bullet somewhere on the ogive as it should.

It seems to me that these bullets are stout enough so that the seater plug contacting the point would be no biggie. That should give ammo all having the same COAL. So what would give the more consistent ammo, the stuff I just made or seating the bullets with the plug contacting the bullet point?

 

[Fire_9]

Measuring to the tip of the bullet I’m assuming?

 

[antelopedundee]

Measuring to the tip of the bullet I’m assuming?

Yes, since that distance is what determines whether or not the loaded round will fit in the magazine. The tips aren't soft so there's little chance of deforming them if the seater plug contacts them. COAL should be the same, but the distance to the leade would vary. Also I don't know how significant a .007 difference is.

So would folks here rather the seater plug contact at the ogive or the bullet tip?

 

[geewhiz]

So would folks here rather the seater plug contact at the ogive or the bullet tip?

ogive. If you are concerned about variation in the meplat then I would seat just a bit deaper so they will fit in your mag well. I see why you are concerned about overall length due to fitting in your mag well, but I think the measurement that matters is BTO.

 

[millerkiller77]

Yes, since that distance is what determines whether or not the loaded round will fit in the magazine. The tips aren't soft so there's little chance of deforming them if the seater plug contacts them. COAL should be the same, but the distance to the leade would vary. Also I don't know how significant a .007 difference is.

So would folks here rather the seater plug contact at the ogive or the bullet tip?

Seater to contact the ogive. Take a few projos and tap the meplat on a hard surface a few times. Compare before and after measurements and I think you'll be surprised

 

[BackofBeyond]

Ogive is much more consistent than meplat. I’ll check COAL length to ensure it’ll fit in the mag, but then set zero on Base to Ogive and roll with that.

 

[Fire_9]

Yes, since that distance is what determines whether or not the loaded round will fit in the magazine. The tips aren't soft so there's little chance of deforming them if the seater plug contacts them. COAL should be the same, but the distance to the leade would vary. Also I don't know how significant a .007 difference is.

So would folks here rather the seater plug contact at the ogive or the bullet tip?

I bet if you measure to the ogive the variation goes away. If .008” variation makes a difference in whether or not it’ll run in a mag, seat them deeper…

 

[antelopedundee]

Is 1.2500 to 1.2570 normal or excessive length variation from bullet to bullet during the mfg process?

My other issue is that the chamber has a short throat so I can't seat them deep enough to give these bullets the amount of jump that they are said to prefer, esp the 130 grain version.

 

[geewhiz]

Is 1.2500 to 1.2570 normal or excessive length variation from bullet to bullet during the mfg process?

My other issue is that the chamber has a short throat so I can't seat them deep enough to give these bullets the amount of jump that they are said to prefer, esp the 130 grain version.

I do not think that 7 thou of variation is excessive.

 

[mtmuley]

Ogive is much more consistent than meplat. I’ll check COAL length to ensure it’ll fit in the mag, but then set zero on Base to Ogive and roll with that.

This works. mtmuley

 

[Don Fischer]

I always measure to the tip and make sure the loaded round fit's the magazine. Like to start with the base of the bullet flush or close as I can get it to the base of the neck where it meet's the shoulder. Cartridges to long for the magazine don't make very good hunting rounds!

 

[antelopedundee]

I do not think that 7 thou of variation is excessive.

I wonder where the 7 thou difference manifests itself. If the amount of bullet below the case mouth is always the same then CBTO is the way to go. I wonder if someone as looked at differences in ES or velocity when all rounds are loaded to equal COAL or if one can even tell much difference.

 

[antelopedundee]

I always measure to the tip and make sure the loaded round fit's the magazine. Like to start with the base of the bullet flush or close as I can get it to the base of the neck where it meet's the shoulder. Cartridges to long for the magazine don't make very good hunting rounds!

In my case ammo being seated presumably to the same CBTO had some which wouldn't chamber. I was using new Quality Cartridge 6.5-06mm brass and it was a tight fit in this chamber. I ended up full length resizing some of it which was something I'd never had to do before. Have not had time to shoot it yet, too dang hot out.

 

[WapitiBob]

Is 1.2500 to 1.2570 normal or excessive length variation from bullet to bullet during the mfg process?

My other issue is that the chamber has a short throat so I can't seat them deep enough to give these bullets the amount of jump that they are said to prefer, esp the 130 grain version.

.007 is excessive for a machined bullet but my TSX bullets aren't machined.

 

[Don Fischer]

In my case ammo being seated presumably to the same CBTO had some which wouldn't chamber. I was using new Quality Cartridge 6.5-06mm brass and it was a tight fit in this chamber. I ended up full length resizing some of it which was something I'd never had to do before. Have not had time to shoot it yet, too dang hot out.

Hate to tell you this but, if you've ever bumped the shoulder as they call it, you've FL sized. You can't run a case that far into the die and leave any part untouched. I prefer to call it partial sizing. I neck size till the case will no longer chamber then partial size until the bolt close's easily on a sized case. All bumping the shoulder is really doing is sizing the case the fit that chamber.

 

[antelopedundee]

Hate to tell you this but, if you've ever bumped the shoulder as they call it, you've FL sized. You can't run a case that far into the die and leave any part untouched. I prefer to call it partial sizing. I neck size till the case will no longer chamber then partial size until the bolt close's easily on a sized case. All bumping the shoulder is really doing is sizing the case the fit that chamber.

I expect my chamber is "petite" to paraphrase my smith. All I know is that the new cases chambered harder than one would want for hunting ammo. I seated the die to just touch the shell holder. Took very little effort to run the case in and out. FWIW I never bump shoulders; I either run the die all the way to the shell holder or leave it at least a 16th short. For this gun I will always FL size.