OAL variations....!?!?

[Jeremybj]

Greetings,

Just got my new 260 going and having some issues with the oal. I previously had a Redding comp seater die in 6.5 creedmoor and the oal was literally exact every time.

So now with my 260 the oal is varying by .004". I am using a second hand Redding comp die to do it. I am using fggm 308 brass that I necked down to 260 and trimmed it to length.

So here are the possible reasons why the oal is carrying
1) my second hand Redding comp die was in the for sale section for a reason.
2) the resized 308 to 260 brass isn't consistent
3) I'm not being consistent....???

If anybody has any insight that would be helpful. I do have a cheap set of rcbs dies I could try it with. I don't have any factory 260 brass to try it with.

Thanks for any help,
Jeremy

 

[Sig Marine]

Most of us reloading for accuracy use a measurement from the base of the case to a given point on the ogive using a comparator. OAL is a factor when restricted by max length based on a magazine but too inconsistent because of the variances in bullet ogives; we basically load at a seating depth that gives us the best accuracy based on the distance of the bullet to the lands. This said, brass and your case prep can play a part, bullet manufacture plays a part, your press technique plays a part, neck tension and lubrication can play a part, the die and seating stem can play a part, amount of powder and case capacity can cause inconsistent seating with compressed loads, etc.

What bullets are you using? Are you chamfering the inside of your necks? Are you using a lubricant before seating your bullets? Are you using the same pressure on your press handle when seating? Is the bullet tip bottoming out in the stem instead of being the stem making contact on the ogive and controlling the depth? The latter occurs when using the longer ogive bullets like the Berger VLD's which have a very, very long nose and usually require a specific seating stem. Is the load compressed?

Some things to think about/check. More information/details would help as well...

 

[grinnergetter]

Stopped having that when I started doing the seating process twice, or going to full seat then raising the ram a bit and hitting it again. Just an idea.

 

[Jeremybj]

I should clarify. I do measure the ogive, so the variation is at the ogive, not at the tip

 

[Jeremybj]

I'm using the Giraud power trimmer to trim chamfer and debur. The bullets I'm using are eld m 147s

 

[Rerun7]

What kind of difference are you seeing on paper from that .004 variance?

 

[spife7980]

Do you have similar differences in your base to ogive? Aka is it present in the bullets by themselves?

 

[CanSniper]

Man, I have been fighting this fight for a while now. Here is what I have found so far.

1. Annealing makes a difference.
2. Lube the bullet before seating.
3. Make sure the bullet fits in the seating. stem with no rocking.
4. Neck tension makes a difference.

I think it makes a difference. Especially if you are running close to the lands. The further the jump the less I personally think it matters. JMHO

 

[Jeremybj]

I haven't shot the rifle yet, but I intend to run .010 off lands so I'm running as close as .006 off lands. Part of me says run it .015 off lands and not worry about the variance, but I'd like to see what it looks like on paper first.

I'll do some measuring of the bullets tonight and take the die apart and see if the seating stem sits nicely with the bullets.

 

[Rerun7]

I haven't shot the rifle yet, but I intend to run .010 off lands so I'm running as close as .006 off lands. Part of me says run it .015 off lands and not worry about the variance, but I'd like to see what it looks like on paper first.

I'll do some measuring of the bullets tonight and take the die apart and see if the seating stem sits nicely with the bullets.

How do you know it’s a problem when you haven’t even shot it yet!!!

You are going to drive yourself crazy chasing this. Go shoot the rifle and see if there is any discernible difference on the target. I have run into this same issue and chased it for a while until I realized that it didn’t really matter in regards to the results I am getting on paper. Mine run a variance now but it’s a window that the rifle doesn’t seem to care.

If you shoot it and accuracy isn’t acceptable then by all means obsess over it. But don’t spend a lot of time trying to solve a problem you don’t know exists yet.

 

[Jeremybj]

Yeah, I can't argue with that logic!!

 

[Holliday]

Man, I have been fighting this fight for a while now. Here is what I have found so far.

1. Annealing makes a difference.
2. Lube the bullet before seating.
3. Make sure the bullet fits in the seating. stem with no rocking.
4. Neck tension makes a difference.

I think it makes a difference. Especially if you are running close to the lands. The further the jump the less I personally think it matters. JMHO

What lube are you using?

 

[CanSniper]

I use just a very light amount of sizing wax on my finger. Rub it on the bullet, trying not to get any on the boat tail so it does not contact the powder in the case. If you seat 5 dry, then seat 5 with lube, without touching the settings on the die. You will find that the 5 with lube are more consistent, and because they slip in easier they will be seated deeper than the dry ones. I believe this is due to the brass flexing under seating pressure. However it is not a one cure problem. Everything stacked together adds up. Maybe it doesn't make a bit of difference. But, I still keep a eye on it just eliminate inconsistency in every way possible.

I also played with the dry neck lube. Did not offer the same results for me. I also tried the Hornady one shot case lube. Just spray in the box of bullets and shake it up a little. But I worried about it contaminating the powder.

I don't necessarily worry about +or- .001 but when something is not right you can get some pretty wild swings. Plus there is always some pretty extreme fliers in every batch. I cull these out.

When it is going good, it's good. When it's not it's frustrating.

 

[Rhed]

I used to seat bullets with a Forster. It was consistent for most of the time. Also dip my bullets in dry lube just a little at the base. I switched to chamber seating and been consistent since.