Inconsistent COL

[Mlgrace]

I have noticed that I am getting an inconsistent COL. Rockchucker press, RCBS dies, 7mm-08, Hornady brass, 139g SST. The charge is not compressed.

the brass is sized and the primers are seated correctly. The seating die is screwed into the press to the nut T the desired depth and the hex head keeper screw is installed and tight.

I have only been hand loading for a few years. What might I have missed that can cause this? Gracias.

 

[Dusty Stevens]

Measure the bullets by themselves preferrably using the exact seating plug from your die and total oal. I bet youll see the same inconsistency there youre seeing in the finished rounds

 

[Martin52]

Overall length variance can be due to variance in the length of the projectile from base to tip. This is not unusual and the rest of your reloading process may be fine.

Measure consistency from the cartridge base to the ogive on a loaded round, not to the tip. This might help:

Base to Ogive « Daily Bulletin

Content tagged with Base to Ogive.

bulletin.accurateshooter.com

 

[Idaho-Lefty]

I Lap my seating Stems for the desired bullet. I cover Bullet with, Lapping Compound, Spin Stem in good TRUE Drill, chuck ! You MUST hold Bullet, Straight ! Some of the Cheaper Bullets are all over the Map on Length from, Lot to Lot ! Once, I called Nosler Tech's on, the .270 cal. 140 AccuBond's and they said, ".025 thousandths, on length, is ACCEPTABLE from, set up to set up, on Machines" !!!,. OMG ! Needless to say, NOW, I buy several Boxes at a Time w/ SAME Lot # !

 

[Drolds72]

neck tension/spring back that is inconsistent will cause this as well.

 

[rsbhunter]

I have noticed that since I have practiced brushing the inside of necks, annealing (homemade $100.00 machine) and I use hbn on bullets and in side of necks, that if my oal from base to ogive varies more than .002, I worry.....cases that are fired multiple times get work hardened.... Making seating a highly variable operation...high neck tension increases variance... rsbhunter

 

[Idaho-Lefty]

My Vote is WITH,.. Erik Cortina,. I've quit worrying about, COAL that much, since owning, Tikka's with long freebores and using Tangent Ogive Bullets that, LIKE to, "Jump" ! Your Lead, is MOVING foreward, lil' by lil' with every few, shots ! Read Base to Ogive "Daily Bulletin" that, Martin posted ! That Article, has some of, your Answers ! I'm NOT, a "BR" shooter, tho ! Hunting and informal Target shooting, Steel Plates, etc. for me !

 

[Richard Coody]

I have noticed that I am getting an inconsistent COL. Rockchucker press, RCBS dies, 7mm-08, Hornady brass, 139g SST. The charge is not compressed.

the brass is sized and the primers are seated correctly. The seating die is screwed into the press to the nut T the desired depth and the hex head keeper screw is installed and tight.

I have only been hand loading for a few years. What might I have missed that can cause this? Gracias.

First can you see the difference on your target. Sort some for consistency and see if they shoot better than the others. If you can't see the difference why worry about it.

Most likely cause.

1. Inconsistent neck tension caused by work hardened brass. Cure annealing, neck turning, premium dies, using mandrels for final sizing, lots of experimenting and down the rabbit hole you go

2. Bullets with an inconsistent ogive curve. Sort about 50 and see what you get. Premium bullets vary a lot less.

3. Seater. Buy a Wilson in line die and arbor press

But just remember what I said at the start. If you can't see it on the target then why bother.

 

[K22]

Unless you are sorting bullets by ogive, some inconsistency is normal as measured from the tip of the bullet.

I've seen variances of + or - .005" in some high quality bullets in a box of 100. Match grade bullet tend to have less variation than hunting bullets.

Unless you're a bench rest competitor I don't believe it's an issue worth considering, at least that's been my experience. My precision varmint rifles with match grade barrels shoot in the sub 1/4 to 1/2 moa range with reloads that have the aforementioned variances. I should also state that I never seat the bullet closer than .010" of the lands because of bullet ogive variations.

 

[Mlgrace]

So I got concerned with this when I measured my case seating depth today at 2.894. Then I measured A half a dozen random completed rounds that varied from 2.79 to 2.84. Seems that my jump is pretty long? So then I started ordering why my seater was producing a variance.

 

[Dusty Stevens]

Pic stolen from here years ago. this is your problem. Die dimensions dont move unless something is loose which you verified. Measure the ogive and oal like i said earlier and youll see the difference.

 

[rsbhunter]

Just curious, how many firing's on brass and difference between od of fired neck and od of resized neck? If you have a nylon bore brush, try just brushing the id of neck before seating....I can notice a difference in seating pressure if I forget to do that....On the id/od of case neck, unless it's for a large bore, big recoil rifle , .0015-.0025 is usually enough tension to hold the bullet....rsbhunter

 

[Mlgrace]

Just curious, how many firing's on brass and difference between od of fired neck and od of resized neck? If you have a nylon bore brush, try just brushing the id of neck before seating....I can notice a difference in seating pressure if I forget to do that....On the id/od of case neck, unless it's for a large bore, big recoil rifle , .0015-.0025 is usually enough tension to hold the bullet....rsbhunter

Two reloads on these cases So three total. I use a nylon brush on every case with just a hint of lube. I have some starline new cases that I have not loaded yet.

I will check the dimensions in the morning.

 

[Mlgrace]

View attachment 1216425

Pic stolen from here years ago. this is your problem. Die dimensions dont move unless something is loose which you verified. Measure the ogive and oal like i said earlier and youll see the difference.

I will do the old eyeball test in the morning!

 

[Dusty Stevens]

I will do the old eyeball test in the morning!

Do the old caliper test. That pic is a gross example. Sometimes its hard to see .010

 

[Sandstorm]

Better bullets will help immensely also...Dustys right on.
And stop measuring Coal and start with BTO....just my 2c
Shoot well my friend.

 

[Bill Norris]

Agree I find base to ogive measurements will show u much less variances even with run of the mill bullets

 

[Dusty Stevens]

Theres another issue with the BTO measuring on those bad bullets- youre measuring the ojive at a spot thats totally different than where the seater plug hits. So just for giggles take those need to be sorted bullets and measure total oal, bto, then put your seater plug on it and measure again. The only solution, besides better bullets, is make your comparator the same dia as your seater or make a seater that hits where your comparator does. To really get right with less than perfect bullets, your seater plug AND your comparator should hit on the same diameter as your freebore dia (since thats the part that actually matters)

 

[Ned Ludd]

I sort bullets by OAL for pointing purposes and typically get around .015" overall spread from a Lot of Berger bullets with perhaps just a very few outliers that are even shorter/longer. I'd imagine the OAL range of the bullets Dusty showed in the picture above is more like .100". Regardless, I have also measured bullet base-to-ogive (BTO) on many occasions and find the overall BTO range is usually far smaller than the range of OAL of the same bullets. What that means is that the majority of bullet OAL variance lies in the nose region.

When you seat a bullet, the seating die stem contacts the bullet far out on the nose just below the meplat. When you measure cartridge base-to-ogive (CBTO), the caliper insert seats just above the bearing surface at the base of the nose, [relatively] close to where the bullet will first contact the lands. Because the majority of bullet OAL variance resides in the nose region, the distance between the seating die stem and caliper insert contact points also varies as bullet OAL varies (i.e. "critical distance" in cartoon below). This is one major cause of seating depth variance. However, the distance between the seating die stem and caliper insert tool contact points is only part of the overall nose length.

Because you were measuring cartridge overall length (COAL), variance in loaded rounds do to the entire nose region might easily be even greater. In other words, the more of the nose region you include in your measurement, the worse the variance is likely to be. As has been noted, measuring CBTO for loaded rounds with a caliper insert tool will likely give you much less variance. But remember, you can't just guess at CBTO based on a previous average COAL measurement. You will want to measure CBTO for all your loaded rounds, which also means setting up your seating depth tests using CBTO measurements. Once you get in the habit of using CBTO measurements for everything, rather than COAL, I suspect the seating depth issues will largely disappear.

 

[Texas10]

Many times, and this is especially true with slender long range bullets, the bullet tip (meplat) hits against the end of the seating stem, whereas the stem should push against the ogive, making for uneven seating. Before loading a new bullet, I pull out the seating stem and check the fit, often selecting another stem that fits better. Sometimes I just pull out a drill bit and bore a relief hole deeper in the stem, allowing it to push against the ogive instead of the tip.

The Hornaday A-Tip requires a special seating stem just for this reason. Too long and pointy for most stems to work properly.