# Bullet seating



## Donnie m (Jul 6, 2009)

I am having an issue with bullet seating depth the problem is my loads on my 6.5 x 284 are 3.105 when seating I get random seating depths of 3.100 - 3.105. I am using RCBS dies and this set seams to be the only ones I have had this issue with?


----------



## swglenn (Sep 20, 2009)

Your seating die is pushing down on the part of the bullet that actually engages the lands, not on the tip. If this point isn't consistent from bullet to bullet then the cartridge overall length will vary. Even then the overall length may not be the same to a couple of thousandths. Not really a big deal as long as where the bullet engages the lands is the same length from cartridge to cartridge. 
What bullet are you using? A run of the mill hunting bullet may not be held to the same specs as a target bullet. For hunting this is not usually a problem since if your aim is good on a heart lung shot you will be fine. In target shooting, particularly at longer distances, 600-1000 yds, this can become more of a problem which is why they use custom target bullets.
The target shooters will use a die that has a micrometer on the top to adjust the seating depth to 0.001". But again the critical measurement is keeping the bullet engaging point at the same point in respect to the lands. If this varies from shot to shot then the barrel pressures can vary and the velocity will change and that will cause a change in the vertical placement of the bullet.


----------



## 27contender (Dec 22, 2008)

I am just a b-gunner but .005 WOW! I have a hard time getting that out of my set up. Granted I just started trimming (and I messed up a few of those +/- .01 maybe). I looked at a box of factory ammo that I thought would have a OAL of 3.570 that shoot pretty well out of my gun (sub moa 100 yrds) and found that they ranged from 3.452 to 3.594.

I guess I have a ways to go to catch up to you!


----------



## Screeminreel (Jun 2, 2004)

Donnie m said:


> I am having an issue with bullet seating depth the problem is my loads on my 6.5 x 284 are 3.105 when seating I get random seating depths of 3.100 - 3.105. I am using RCBS dies and this set seams to be the only ones I have had this issue with?


Not up on the particulars of the case your loading but do need to ask,

Are you measuring the total AOL bullet tip to base, or using the base to ogive dimensions?

Have you shot any to verify they aren't grouping the same?

How close to the lands are you loading?

If measuring the total, you will easily see this much variance in bullets from just about most manufactures, some with the plastic tips are a little better but will still vary.

Even using the base to ogive you can see a difference depending on where or how your seating plug contacts the bullet. In most cases you can do one of two things, either have the plug fit to your choice of bullets, which will sometimes work over several brands with similar profiles, or measure and separate your bullets by base to ogive lengths before you load them.

I have a couple of plugs that I have simply run a drill into to relieve the tip clearance on. They were seating off the tips only. This allows them to get a bit lower on the bullet, but still might give some differences.

I generally only worry about this on a couple of rifles I use to shoot well out past 600yds with. Everything closer, I really don't worry about as it hasn't made much of a difference in the accuracy. They will all still shoot small groups.


----------



## Ernest (May 21, 2004)

Use a bullet comparator devise to measure, not just overall length with calipers. The key measurement (assuming no mag. length restrictions) is base of case to major bullet diameter. 

An Overall length variance of .005 with mass marketed bullets is to be expected. 

Here is a catalog cut explaining: 

We have been making these hex style bullet comparators for over 20 years, and believe we make the most accurate tools available. The holes in the Sinclair Bullet Comparators are cut with throating reamers to accurately duplicate the actual throat of a rifle. The comparator is used with calipers, and allows the reloader to accurately measure the length from the major diameter of the bullet to the case head. It also enables you to make accurate seating depth changes to your bullet seater. The Sinclair Comparator does not attach to your calipers, so your calipers are free for other measurements. Machined from stainless steel.

There are two different models of Sinclair Comparators to cover bullets calibers from .17 caliber to .338. The first model (09-600) features holes bored and throated for .224, 6mm, .257, 6.5mm (.264), 7mm, and 308. The second model (09-700) has holes throated for .172, .204, .224, .270, .308, and .338 caliber.


----------



## Pocketfisherman (May 30, 2005)

If you really are getting variation using the ogive measurement, look for problems with the shellholder like crud in it.


----------



## THE JAMMER (Aug 1, 2005)

Wow. Lots of great info in a short thread. Take to the bank what was said by: swglenn, screeminreel, and ernest. All great info, with, what I think is the most important, is to use a comparator. That gives the most important measurement, because it's the distance between the the point on the bullet that first contacts the lands and the lands that is the most important one.

As was said depending upon the type of bullet, the oal of the bullet will vary, especially on bullets which do not have a plastic tip. Just take several match type bullets and look at them side by side and you will see that they are not the same length. This problem is minimized with the tipped bullets, because they are generally more uniform in their OAL, just because of the nature of that tip.

I always use a comparator measurement when reloading. I will generally start a load with the maximum OAL for that cartridge, and see what the comparator length is for that OAL. I then shift to using only the comparator length when adjusting seating depth thenceforth in the developing of that load.

THE JAMMER


----------



## pulpfishin (Nov 27, 2006)

Screeminreel said:


> I have a couple of plugs that I have simply run a drill into to relieve the tip clearance on. They were seating off the tips only. This allows them to get a bit lower on the bullet, but still might give some differences.


I have drilled out EVERY seating die plug I own, and it makes a HUGE difference!!!!

I actually have a friend with a lathe, so I'm able to do it with greater precision than most.

The number one advice I give to anyone reloading is to seat the bullet using the ogive only. It allows for tighter tolerances in seating depth, and reduces bullet run out significantly.

Using the tip to seat you will always encounter variations in the amount of compression on the tip of the bullet (especially soft points). This is where much of the variation in seating depths comes from.


----------



## B-Money (May 2, 2005)

mash out a set of 12. Group them into the 3 longest, 3 shortest and 3 middlest?...

See if the groups are different on paper. If yes..fix. If no... then ... no problem.


----------



## 27contender (Dec 22, 2008)

Man I have a ways to go.
R


----------



## B-Money (May 2, 2005)

My math didn't work in my earlier post. You will have 3 bullets left over. Should have been 4, 4 and 4. What do you expect from a born-again accountant??


----------



## Ernest (May 21, 2004)

******* bullet comp. Use at your own risk. Goes like this.

Take a shot out piece of brass, and resize the neck. With bushing dies, use a small bushing for the caliber. With a full length die, depending on die adjustment, you can pull the expander so as to resize the neck relatively small. We want a tight necked piece of brass here.

Use a hack saw to cut a caliper groove in the base of the case.

Take the loaded round, place the ******* bullet comp. over the bullet. It should hang up right around the major bullet diameter. Don't push it too hard, cause you don't want to seat it, just get it to hang up.

Depending on the hand gun brass you have laying around, you can use this same basic approach by finding a hand gun case slightly smaller than the major bullet diameter of your rifle round.

This will give you a _relative_ measurement from case head to major bullet diameter. Not super match grade bench rest accurate, but if you are consistent with the caliper tension, a decent degree of accuracy.


----------



## CHARLIE (Jun 2, 2004)

Man what an in depth discussion. Somewhat beond my expectations regarding reloading but all good reading. I had to read and re read Earnest's post but I finally figured what he was trying to get across. (I think)

Charlie


----------



## Ernest (May 21, 2004)

I was less than clear. 

Key measurement - case base to forward most point of major bullet diameter (some say ogive.) Its the forward most fat part of the bullet and is the spot where the bullet first engages the lands. You can't measure this distance easily with simple calipers. 

Comparator is simply a devise that slides over the bullet point so as to facilitate measurement of the distance from case base to the major diameter. Its a relative, not absolute, number cause when you use your calipers, you measure the critical distance plus the length of the comparator. 

I was trying to describe this ******* method of building your own comparator with stuff laying around the house. 

Its one of those, easy to understand when you see it, hard to describe deals.


----------



## CHARLIE (Jun 2, 2004)

I got it Ernest, I got it... How do you spell devise ??

Charlie


----------



## Ernest (May 21, 2004)

See, part of the thing is this. I'm not a great speller. 

Long story made short, I was hooked on fonics, and later, I x-caped from rehab.


----------



## CHARLIE (Jun 2, 2004)

I love it.. Into Texting too I see 

Charlie


----------



## Donnie m (Jul 6, 2009)

I am using 140 grn Berger VLD. And yes I am measuring overall length with calipers. I would not be to concerned but I do shoot out past 600 with this gun. All the brass was trimmed and weighed to achieve best overall performance but this issue is driving me nuts as 1 will be on the next 3 off and the next on. I will look at better way's of measuring. Thanks for everyones input.


----------



## Screeminreel (Jun 2, 2004)

Donny,

If you keep measuring off the tips you will continue to get weird readings. 

Get the now Hornady set of comparators. They come in a set which will cover most any caliber you load. Then you will get more accurate measurements. Fact is your already probably hitting within about .002" as it is unless your tips are hitting the top of your seating plug as mentioned above. 

IT is just a biproduct of how they bullets are formed that the tips are not all exactly the same. It doesn't mean they won't shoot good groups. If your really that concerned get one of the meplat trimmers and that wil cut them all the same. I have one for my LR rig and I haven't noted it made that much difference out to 1150yds. I did however use the comparator to check the lengths. 

Good luck, and don't let it get ot you too much.


----------

