Load to COAL or Comparator length?

[BLR81]

I was loading up some 260 Rem cartridges for a range visit Wednesday, and ran out of bullets and had to open a new box.

The normal load 42.0 grs of IMR 4350 with a 142gr SMK HPBT. The normal COAL is around 2.850 but I use my Hornady LNL bullet comparator to check seating depth and that normally reads around 2.245 or about .020 off the lands.

The first 30 Lapua brass loaded right at the 2.245 range, but when I looked at the cartridges that were using the new box of bullets the comparator reading increased to around 2.250-2.253 while the cartridge overall length dropped below 2.840 using the same setting on the seating die. (I use the Redding seating micrometer attachment)

So my question is "Does the Redding seating die make contact on the Ogive?" If it does then these bullets have ogives that vary .010-.015 from box to box. So, do I need to use the COAL or the comparator reading to set the die to match my previous worked up load?

I was getting sub 1/2 moa 5 shot groups at 300 yds. And, with the new bullets the COAL is shorter and the bullet comparator is longer. So do I leave the seating die the same or adjust it to match the original COAL or Bullet Comparator reading?

[Sig226]

Someone far more experienced than myself will come along in no time, however I have experienced similar to this in .308WIN for both a bolt gun and auto.

For me, COAL doesn't much matter unless I am loading for a magazine, in which case it may or may not.

So, non-mag fed/semi-auto, I always base my loads off ogive both in terms of load development and record keeping. I figure the change in OAL does make a difference in performance characteristics, but less than if the ogive was in a different position relative to the lands.

It is the same bullet for the most part so setting it back a bit more for safety probably is not necessary unless you are up close to max. I didn't look up your load, nor have a loaded for the 260 Rem. YMMV

[Bill Steele]

I was loading up some 260 Rem cartridges for a range visit Wednesday, and ran out of bullets and had to open a new box.

The normal load 42.0 grs of IMR 4350 with a 142gr SMK HPBT. The normal COAL is around 2.850 but I use my Hornady LNL bullet comparator to check seating depth and that normally reads around 2.245 or about .020 off the lands.

The first 30 Lapua brass loaded right at the 2.245 range, but when I looked at the cartridges that were using the new box of bullets the comparator reading increased to around 2.850-2.853 while the cartridge overall length dropped below 2.840 using the same setting on the seating die. (I use the Redding seating micrometer attachment)

So my question is "Does the Redding seating die make contact on the Ogive?" If it does then these bullets have ogives that vary .010-.015 from box to box. So, do I need to use the COAL or the comparator reading to set the die to match my previous worked up load?

I was getting sub 1/2 moa 5 shot groups at 300 yds. And, with the new bullets the COAL is shorter and the bullet comparator is longer. So do I leave the seating die the same or adjust it to match the original COAL or Bullet Comparator reading?

I think you lost me in the third para. The reading on the comparator (which references off the ogive) is more than the cartridge OAL?

Probably just me, but I am confused.

[BLR81]

I think you lost me in the third para. The reading on the comparator (which references off the ogive) is more than the cartridge OAL?

Probably just me, but I am confused.

You obviously did a better job reading then I did writing it.

The 2.850-2.853 figures should have been 2.250-2.253. So the comparators reading of the distance from the base of the cartridge to the ogive got longer by from .010-.013 while the COAL got shorter by .005-.009.

[BLR81]

Someone far more experienced than myself will come along in no time, however I have experienced similar to this in .308WIN for both a bolt gun and auto.

For me, COAL doesn't much matter unless I am loading for a magazine, in which case it may or may not.

So, non-mag fed/semi-auto, I always base my loads off ogive both in terms of load development and record keeping. I figure the change in OAL does make a difference in performance characteristics, but less than if the ogive was in a different position relative to the lands.

It is the same bullet for the most part so setting it back a bit more for safety probably is not necessary unless you are up close to max. I didn't look up your load, nor have a loaded for the 260 Rem. YMMV

The 260 is a necked down 308, and the magazine is more than capable of receiving cartridges whose overall length is greater than the distance to the lands.

But I've run many ladder test for this bullet and others along with changes in seating depth, and by far the most accurate was 42 grs of 4350 and the 142gr SMK. I can't imagine that the oal changing by .010+ will make that big of a difference since at least that amount is already seated beyond the lands.

But, I am concerned that I may need to adjust the seating depth every time I open a new box of bullets. I could figure it out myself by loading 10 with the die set as is, and then 10 with the die readjusted to seat them back at the 2.245 value. It's just such a hassle.

And it's somewhat of a waste of powder and bullets which are in short supply, just to find out. So, I'm hoping someone more experienced can save me.

[Bill Steele]

You obviously did a better job reading then I did writing it.

The 2.850-2.853 figures should have been 2.250-2.253. So the comparators reading of the distance from the base of the cartridge to the ogive got longer by from .010-.013 while the COAL got shorter by .005-.009.

And both the old and new lots were the same 142gr SMK's right? I have not seen that much of an ogive difference lot to lot with my SMK's.

In any case, the jump is most important, the OAL is unimportant.

The old comparator target will probably get you close to the old jump number, but with a different profile on the ogive, it likely won't be definitive in nailing the jump. I think I would determine what the old .020" jump will be with the new profile and establish a new comparator dimension target for that lot to assure the same jump. For .5 MOA, getting the jump exact likely won't be required anyway.

Also, have you measured/weighed the new lot to determine they all are the same dimension/weight?

Finally, for a complete non sequitur, you didn't buy the new lot from Cabella's did you?

[BLR81]

And both the old and new lots were the same 142gr SMK's right? I have not seen that much of an ogive difference lot to lot with my SMK's.

In any case, the jump is most important, the OAL is unimportant.

The old comparator target will probably get you close to the old jump number, but with a different profile on the ogive, it likely won't be definitive in nailing the jump. I think I would determine what the old .020" jump will be with the new profile and establish a new comparator dimension target for that lot to assure the same jump. For .5 MOA, getting the jump exact likely won't be required anyway.

Also, have you measured/weighed the new lot to determine they all are the same dimension/weight?

Finally, for a complete non sequitur, you didn't buy the new lot from Cabella's did you?

No not from Cabella's but I did buy them from Midway.

When I did the seating depth test, the .005 change both higher and lower created about an eighth to a quarter moa difference. While the seating that showed best was under a inch and a half at 300 yds, a .005 deeper created a 2 inch group while the same amount under created about a inch and three quarters groups.

Both are exceptable considering my marksmanship skills, but I would prefer to be more certain that the problem is me rather than the ammo when I practice. I'll take your suggestion and run my distance to the lands check with the new bullets and see how close they come to the original numbers.

As far as the ogive being different between lots, I was thinking that if the seating die didn't push on the ogive but further up toward the nose. Then if the nose were steeper the die would make contact later and seat the ogive shallower. But, for the COAL to be shorter then the nose would also have to be shorter along with steeper.

Ill check the new bullet seating to lands tomorrow morning.

[Bill Steele]

No not from Cabella's but I did buy them from Midway.

When I did the seating depth test, the .005 change both higher and lower created about an eighth to a quarter moa difference. While the seating that showed best was under a inch and a half at 300 yds, a .005 deeper created a 2 inch group while the same amount under created about a inch and three quarters groups.

Both are exceptable considering my marksmanship skills, but I would prefer to be more certain that the problem is me rather than the ammo when I practice. I'll take your suggestion and run my distance to the lands check with the new bullets and see how close they come to the original numbers.

As far as the ogive being different between lots, I was thinking that if the seating die didn't push on the ogive but further up toward the nose. Then if the nose were steeper the die would make contact later and seat the ogive shallower. But, for the COAL to be shorter then the nose would also have to be shorter along with steeper.

Ill check the new bullet seating to lands tomorrow morning.

The reason I asked about Cabela's is I did get a bad box of AMAX's. The box had a valid lot number, but the bullets were all over the place. The Hornaday rep said the kind of variation I was seeing wasn't possible in a single lot. We concluded either they were knock-offs or someone had sorted lots of boxes made over a fair amount of time and had returned the outliers in a single box that Cabela's just put back into new stock.

Definitely, if your rifle delivers those kinds of differences of POI with a .005" difference in jump, I would get the jump dialed first.

The seating plug won't be contacting the bullet in the same place on the ogive as your comparator ring. I think you would have to use a much smaller insert to get the comparator up that high on the ogive.

[ExtremeX]

One thing I have noticed when trying different bullets is the seating stem and bullet profiles don’t always match up.

I had to change my .308 seater twice when using my 168gr AMAX bullets since it was grabbing the bullet way above the ogive. The Foster ultra micrometer stem got me much closer to the ogive than the RCBS seater for example.

I am still running into this issue with my .223 bullets. My RCBS GM Match seater contacts my 55gr projects much closer to the ogive. The 75gr match bullets with the same seater plug contacts much closer to the tip of the bullet giving me larger variations when measuring with a bullet comparator.

This might be something worth looking into. Just remove the seater plug and throw a couple different bullets in there and see how close to the ogive they contact.

[ChrisGarrett]

There can be (are?) variations between production lots of the same model number of bullets. I think that I read that Sierra runs four different lines and depending on what machine you get, or how much the dies have worn over the zillions upon zillons of bullets produced on that particular die set, you might have a few thous of variance.

As an example, I have a 7RM and I'm fond of the Hornady 162gr National Match HPBTs. Over the years, I've collected some older boxes, some more recent boxes and some from right before they ceased production.

While they all share the same part number, there are three distinct variations, one in fact, having a rebated boat tail and the ogive numbers aren't anywhere close.

Chris

[BLR81]

Follow-up on my range visit. Reloaded the last 20 rounds using the bullets from the new box. Adjusted the die to seat the new bullets deeper, and back to my original seating depth of 2.245 on my Hornady LNL comparator guage.

End result was the load performed beautifully. All groups were sub moa at 300 yds, with the best 5 shot group measuring almost 1.5"s exactly or under 0.5 moa. All 5 shots in the 10 ring and 2 x's on a 8" Shoot-N-C.

I haven't checked the entire box but all 20 loaded to the proper length once the die was re-adjusted. Note to self, don't assume.

[Bill Steele]

Great news. I always measure and weigh each new box. I segregate down into sublots for my non hunting rounds. Seems to help when I am splitting hairs.

260 is a sweet round.

[dabibbee]

I agree with Bill, I measure any new box of bullets I buy because my shooting buddy got a bad box from Sierra that was .015" to .017" short on the ogive.
He had 62 bad ones out of 500 in the box of 175 SMK's. _ _ it happens!

Dave

[EL_NinO619]

Call sierra, I had a bad box and they replaced it, the also sent me a stack of their sweet labels.

[LynnJr]

TomDW
If your loading for benchrest you use a comparator and forget you ever measured C.O.A,L. to begin with.

The ogives of bullets loaded from a single die vary extremely little.Unfortunately mass produced bullets such as Sierra and Berger are made from a large amount of different dies and they vary as much as 0.020 in a single box.

The Redding seating dies with the hollow stem contact your bullets way up on the ogive probably around 0.218 in diameter.To check this out simply remove the stem and spin a bullet against it with moderate pressure until you see a ring and measure it.

Your bullet will be contacting the barrel at 0.256 diameter assuming a typical Krieger bore is used.So you are seating at 0.218 diameter to make contact at 0.256 diameter with bullets likely to have 0.020 or more variation in a single box.This is why when you measure your seated rounds with a comparator they vary.
Seating depth has the single biggest influence on your group size after you have decided on a powder charge so most competition shooters will try and keep it within 0.002 total variation as measured with a comparator.It sounds like a pain but if your seating with a competition seater with the micrometer top you can seat them all about 0.010 longer than you want them.You can then take all the rounds that were the shortest length and run them through the seater again.You then adjust again and run the next group and so on.

When you see shooters with a pressure gauge on there reloading press to measure seating force they are usually using custom bullets or measured and sorted bullets and the seating force is directly related to the seated length of the rounds.The rounds requiring greater force to seat will be longer as measured with a comparator.
We wil be shooting a 600 yard benchrest mtch this sunday in Ojai and my 6 Dasher rounds all measure 2.510 inches long as measured with a comparator and no rounds measure 2.509 or 2.511.
I will include a picture showing the seating depth measured in 0.001 increments as fired from the bench at 200 yards.You caee the groups tighten then open up again and this is repeatable.
Lynn