I was loading up 100 test loads for 308 tonight using 147gn campro bullets but I keep getting a varied seating depth when checking with calipers. COAL varies between 2.802 and 2.786. The die and bullet seating stem are both secure and tight. I assume this is caused by the RCBS bullet seating stem on the ogive of the bullet, and that ogive being slightly thicker or thinner bullet to bullet? Is there a different die that would give a more uniform depth seat? Or is this more an issue with the bullets (IE. change vendor)?
Bullet seating depth varies
- Thread starter MarshallX
- Start date
- Location
- Western Manitoba
Your seating stem is contacting the bullet at a particular diameter - may or may not be at the "ogive". Dollars to donuts all of your loads have exact same length from their base to that particular diameter. Sometimes a mark is visible on the bullet where the seating stem was pressing on it. The C.O.A.L. differences that you are seeing results from the variation in the shape of the bullets that you are loading.
Bullets typically have a 20 thou variation from the tip to the ogive. This is meaningless, since it is the ogive to rifling distance that matters.
You need a device to sit on the ogive, so you can see how consistent your load is and also, once you know the length that suits your chamber, you can set the correct OAL for any new bullet you want to try.
I have made tools like this using a 1 inch piece of rifle barrel.
Why is your loaded round so short? My 308 ammo is typically .2.85 to about 2.90"
You need a device to sit on the ogive, so you can see how consistent your load is and also, once you know the length that suits your chamber, you can set the correct OAL for any new bullet you want to try.
I have made tools like this using a 1 inch piece of rifle barrel.
Why is your loaded round so short? My 308 ammo is typically .2.85 to about 2.90"
Yeah I notice the mark on the bullet, i was just trying to get uniform depth. I know the cases are all cut to the same length, so with this variance in the COAL, there will be variance in the depth the bullet base is in the cartridge. That in turn may affect the results of this ladder test with all these completed cartridges. Havent encountered this with the hornady 168gn bullets, so was a bit suprised when I started checking these campro 147gn bullets. But I guess thats what comes with the price.
The round isnt so short, COAL for .308 by the book is 2.80. Im looking for reliable feeding in SR-25 magazines.
- Location
- Western Manitoba
Maybe you are assuming that the distance from that "mark" to the bullet base is different from bullet to bullet. You need to measure that to know. In the end, your targets will tell you if there is a difference between the long nose and short nose bullets. If you can see that mark on some of your bullets, then measure from case head to that mark. As Ganderite says, it is the distance to the rifling that counts, not the COAL (so long as the round fits in the magazine).
No. If your seater is pushing down on the bullet near the ogive, the amount of bullet in the case will be quite uniform. The length variation is in the nose section.
The "book" COAL means nothing. What matters is how the OAL suits the magazine and the chamber throat.
I seat bullets to be 20 thou off the rifling, so long as that length will fit the magazine. 2.80 seems short if you are looking for accuracy.
Also, I think a ladder test is a waste on a mediocre bullet. A survey in 0.5 gr increments would be more useful.
A ladder test works only with a bullet of high quality so that the place it hist the target only reflects the load.
Military type FMJ shoot a group so big that it masks the effect of minor powder changes.
As it happens I was testing my new 308W Savage this week. 155gr Nosler match grouped 0.65 to 1.3", using 45.0 to 46.0 of 4895. (Commercial cases) I shot some FMJ and the group were in the 3" to 4" rnage.
That seems too bad to be right, so I am going to try again with milder loads. I would be delighted to get 2"
