Determining OAL for 6.5 Creedmoor

[graydond]

I'm reloading for 6.5 Creedmoor using a Hornady Lock-N-load full OAL Gauge. the instructions and YOUTUBE say to use the gauge with the comparator to determine the measurement of ogive to lands and the say that measurement is your overall case measurement. that number, in my case, is 2.228". as i take the cartridge out of the comparator and measure the case OAL from bullet tip to base i get 2.846". the max cartridge OAL from the Hornady book says 2.800. so, the question is....what dimension should i use for OAL? measuring to the ogive doesn't include the tip of the bullet in the tube. what am i missing....?

I'm using Hornady 130gr ELD bullet.

[NHSHOOTER]

Being that the part of the bullet that contacts the lands first is the ogive that would be the important measurement, how far the bullet point goes beyond the lands is pretty much irrelevant. I am not an expert but that is my interpretation and how I use my OAL gauge.

[graydond]

i understand that. so why don't they get the OAL measurement of the cartridge once the distance to the lands is determined? they are posting the distance TO the lands, not the true OAL. just confusing......

[NHSHOOTER]

I would have to say that you are looking at two different measurements, the distance from the ogive to the base of the case which is your measurement. The reloading manual for that particular cartridge States and overall length from the tip of the bullet to the base of the case. Not everyone uses an overall length gauge. The overall length that is stated in the reloading manual is an Sammi safe reloading length. I hope this clarifies it for you. If any other member has a more definitive explanation please feel free

[Rimfire5]

Remember that the 6.5mm CM was designed for both bolt actions and ARs.
You didn't say which you were loading for.

Most load manuals tend to show the recommended OALs suited for AR mags which require much shorter OALs than bolt actions for the bullets to fit in the AR mags. You get the same confusion trying to load heavy bullets for a .223 in a bolt action. Most load manuals show a recommended OAL of 2.260 which is normally recommended for AR loads. Trying to stay within the OAL recommended for an AR will cause higher pressure for heavy bullets jammed deep into the brass.

My bolt action 6.5mm CMs have mags that are closer to 2.900 or more, although I have found that some plastic AICS mags are limited to about 2.850
My aluminum AICS mag allows OALs up to 2.900.

The chamber measures you quote are appropriate for a 6.5mm CM.
Your measured OALs are in the range for a bolt action mag, but might be too long for an AR mag.

[graydond]

I'm using a Savage bolt action. it's just confusing that all the instruction I've seen are referring the base-to-ogive measurement as the OAL. misleading and confusing.

[jackstrawIII]

The oldschool way to do this is to take a loose case (once fired) and put a bullet in the mouth, which should barely hold the bullet. Seat it extra long then chamber it. The bullet will be pushed back into the case by the lands when you close the bolt. That's your "0" depth. Measure the COAL and then start bumping it back as far as you want. This works great for me. I bump .002" for standard bullets and .05" for monolithic (all copper) bullets. I'll then adjust seating depth as needed, but normally this will get you in the ballpark.

[44 AMP]

TO further confuse things, the definition of ogive, given in the standard reloading manuals is NOT the point where the bullet contacts the rifling.

The ogive is the ENTIRE sloped/curved portion of the bullet from when it reduces from full bore diameter all the way down to the tip.

The point where the bullet contacts the rifling is a POINT ON THE OGIVE, and can be (and usually is) slightly different for every barrel and bullet combination.

The most practical cartridge loaded length to use is the one that fits in your magazine (all the way from bottom to top), feeds through your action, and does not touch the rifling when the round is chambered and the bolt locked closed.

Assuming, you wish to use your rifle as a repeater, and not a single shot.

[jetinteriorguy]

The recommended OAL is to assure your ammo will fit in all available magazines and will feed properly in any rifle. If making them longer works in your magazine and action and suits your needs then have at it. Personally I like to try keep a full calibers worth of the bearing surface in the neck and not jamming the bullets into the lands, but that’s just me. I’m assuming from your confusion that your relatively new to reloading and my suggestion at this point would be to stick with SAAMI’s OAL recommendation to avoid any safety issues until you have a lot more experience.

[Shadow9mm]

Hornady makes modified cases designed to interface with their O.A.L. gauge. It kind of a system.https://www.hornady.com/modified-cases#!/ There are other ways to get around it as mentioned above.

Personally I love the comparator tool, its is a much better and more consistent way to measuring than off the point of the bullet.

Personally I rarely use my OAL tool and modified cases and measure the lands anymore. I do use it when dealing with a new gun or bullet to make sure the factory COL does not put my bullet too close to the lands (0.020 or more). The lands erode and move over time, trying to base accuracy off a moving point seems silly when you think about it. On top of that It just never worked for me. and I have never had a factory load that was too close to the lands. Honestly the OAL tool and modified case were kind of a waste of money IMHO and I do not recommend getting them.

Here's a video from a pro-shooter in relating to chasing the lands. I have been using his methods and have gotten great results every time. https://www.youtube.com/watch?v=oRXlCG9YZbQ

[RC20]

I'm using a Savage bolt action. it's just confusing that all the instruction I've seen are referring the base-to-ogive measurement as the OAL. misleading and confusing.

All my target rifles use Savage actions though it really does not make any difference.

The easiest way to deal with this is to size a case, seat a bullet long ( .040 COAL, ), then GENTLY move the bolt forward and if it goes try to gently close it.

It may not go all the way forward. Very likely it will not close.

It sounds like you are trying to get to the deep end of the pool and confused and I agree, so keep it simple.

Looking at Hornady manual, the ELD-M 140 gr Match says 2.800 COAL.

So load one to 2.840 and you almost certainly will have the bolt stop before it gets to where you can close it.

It may even stick. Gently tap the bolt handle with a plastic end of a screwdriver.

When out, seat the bullet .010 further in (2.830). Do the same bolt close op.

Probably around 2.820 it will close. If its 2.810 or other, makes no difference, that is about the absolute maxim bullet length. As a starter, I got with .020 shorter than the maximum. I know what I can extend it to but you got to be pretty precision shooting to see if it makes any difference.

All that inside measurement and Ogive does the same thing with somewhat better precision.

But unless you are shooting sub 1 inch groups at 100 yards, you won't see it.

Unfortunately what happens is an advanced method for a bench rest shooter gets popular and then all sorts of tools come out. Most of us can't shoot 1/8 inch groups.

Measuring at the Ogive is more accurate than tip measurement but not remotely like you can't load 3/4 inch group ammo without it.

As tip measurement can vary, it can look bad but your seater does not do off the tip, it does off the Ogive (someplace). Once you set it to a given distance, its going to repeat it, though the tip re-measurement on each case may look like it is not.

[cdoc42]

RC20 said:
"Unfortunately what happens is an advanced method for a bench rest shooter gets popular and then all sorts of tools come out. Most of us can't shoot 1/8 inch groups.

Opinion: that most can't do it is because most don't try.

"Measuring at the Ogive is more accurate than tip measurement but not remotely like you can't load 3/4 inch group ammo without it."

Opinion: But you can definitely load under a 3/4" group WITH it. A half-inch group or less gives the shooter much more confidence about his/her point of aim in the hunting field.

[44 AMP]

Opinion: But you can definitely load under a 3/4" group WITH it. A half-inch group or less gives the shooter much more confidence about his/her point of aim in the hunting field.

OK, but what use is it when your hunting rifle won't group that well??

Or, as a friend of mine is fond of saying, "how does this put an elk in my freezer with my .300 Savage 99??"

Point here is that loading practices that may produce tiny groups only have utility when used in rifles that may benefit from them,

I seriously doubt that loading to a point on the ogive is going to turn a 2MOA lever gun into a 3/4 MOA tack driver. Particularly if the load "just off the lands" won't work through the magazine or the action. Guys that are ok with single loading deer rifles generally hunt with single shots.

[RC20]

Side tracking from trying to help the OP out.

The point is, all that stuff is not needed when simple methods are there to get you very good results and only the fancy stuff may help a bench rest bug hole shooter of which the vast majority of us are not.

[cdoc42]

44AMP: "OK, but what use is it when your hunting rifle won't group that well??"

You won't discover that if you don't try to find the best setting depth that improves accuracy. Handloading gives you the opportunity to improve the accuracy of YOUR weapons. If you just seat each bullet to the cannelure as seen in factory rounds, (assuming there is one on your bullet) you have a cartridge that fits any gun. If that happens to coincide with the ability to put the bullet somewhere in an 18-inch paper plate at 100 yards and you're happy with that, fine.

[jmr40]

MOST loads shoot best with the bullet as close as possible to the lands. I no longer handload, but when I did, I always seated the bullets as long as possible to still fit in the magazine. If they would chamber without jamming the bullet into the rifling that was my OAL. If I had to seat them a bit deeper to achieve this, then that was my OAL.

I couldn't load them any longer unless I wanted a single shot rifle. If I wanted to experiment with a shorter OAL it was easy enough to take the loaded rounds and seat the bullet a tiny bit deeper. But I was always able to get the accuracy I wanted using this method.

SOME bullets are known to shoot better with a little jump before hitting the lands. I never tried any of those.

I never paid any attention to the OAL measurement, couldn't even tell you what it was most of the time. I did on occasion measure a round just to see, and it was almost always a bit longer than the load manuals suggested.

[NHSHOOTER]

cdoc42 and jmr40 Very well put, I use the Hornady oal gauge on every new bullet or caliber I start reloading and those oal lengths are all kept in a file to look back on, some bullets dont like much jump or the rifle doesnt, I have a kimber that wont shoot unless its got a good jump, same with the Barnes ttsx needs a good jump, experimenting is the only way to achieve that nice tight group and what someone else said, do you need a half inch group with a deer rifle, "no" but it sure is nice when you find a load that will give it to you..

[cdoc42]

Here are 2 examples that may help the OP understand bullet seating. My first deer rifle is a Remington model 700 in .270. I bought a new Model 700 in .270 and the throat in the older rifle is longer than in the new one. Seating measured from the case base to a spot on the ogive shows the difference:

Hornady 140gr SST

OLD: Base to ogive at rifling: 2.888"
Best accuracy is 2.842" = 0.046" from rifling

NEW: Base to ogive at rifling: 2.857"
Best accuracy is (coincidence) 2.842" = 0.015" from rifling


Hornady 150gr SP

OLD: Base to ogive at rifling= 2.841"
Seat 0.02" = 2.821" (will jam in "new" Model 700)
Best accuracy is 2.781" =0.06" from rifling

NEW: Base to ogive at rifling = 2.813"
Best accuracy is 0.02" = 2.793"

Notice the 0.06" cartridge in the "old" .270 is 2.781"and it will chamber in the "new" .270 but it will be 0.032" from the rifling, not accurate as the 0.02" measurement.

[Unclenick]

Graydond,

I think there is still a lot of confusion here. If you follow the instructions and use the gauge with the caliper comparator adapter, you get a measurement from a point along the bullet's ogive to the bottom of the case head that corresponds to the cartridge loaded with the bullet so far out that it is in contact with the throat of the barrel where the rifling begins. This is a reference point and not necessarily a recommended loading length. If you fire the load with the bullet touching the throat, the peak pressure will be about 20% higher than if you seat the bullet deeper to the SAAMI maximum COL, which for 6.5 Creedmore is 2.825 inches. Indeed, seating it about 0.020-0.030 inches deeper is all it takes to bring pressure down to what the load developers intended in most instances.

If you want to shoot with the bullet in contact with the lands, reduce all the charges in your load tables by 10% to get close to compensating for the pressure increase (when charge changes are small, the resulting pressure changes are close to the square of the change in powder charge). There are people who shoot this way intentionally. Middleton Tompkins, who probably has more long-range gold medals than anyone else on the planet, shoots this way. On the other hand, the idea that having the bullet close to the lands is best for accuracy is out of date. Berger discovered it wasn't reliably true when working with their original secant ogive VLDs (they now use a hybrid ogive). Indeed, Scott Satterly, a nationally ranked competitor, says he is now often shooting with 0.125 inches of jump to the lands. The Berger information is correct and applicable to all loads, though I would reduce the amount of change per step by a third for non-VLD bullet shapes.

Personally, I think a lot of the guys loading very close to the lands just weren't getting adequate cartridge concentricity out of the conventional Remchester brass they were using in the past, and throat contact tended to help make up for it. But today, you can buy Alpha brass for domestic or Lapua brass for import that is super uniform, and use a Redding Competition Seating Die or a Forster Benchrest Seating Die or the Wilson arbor press dies, and get very straight and concentric ammunition almost without trying.

You are currently getting a COL of 2.846 inches when your bullet is in contact with the lands. Knock off 0.020 inches, and you have 2.826 inches. That is just 0.001 inches over the SAAMI maximum, so I would use the SAAMI maximum 2.825 inches as my limit and be prepared to experiment with seating deeper, as it may tighten your groups.

[cdoc42]

My post above Unclenick's speaks to what he says about accuracy and the jump to the lands:

Hornady 150gr SP

OLD: Base to ogive at rifling= 2.841"
Seat 0.02" = 2.821" (will jam in "new" Model 700)
Best accuracy is 2.781" =0.06" from rifling

graydond: check the heading for a private message

[Nathan]

Originally Posted by graydond

as i take the cartridge out of the comparator and measure the case OAL from bullet tip to base i get 2.846". the max cartridge OAL from the Hornady book says 2.800. so, the question is....what dimension should i use for OAL?

Did you get your answer?

I think the Hornady tools are great, but possibly overcomplicate things a bit. Let’s discuss based on the Hornady tools.

CBTO (Case Base To Ogive) is the measure from case head to ogive. It is important for knowing distance from bolt face to lands for a given bullet on the cartridge side.

OAL or COAL are the same. They are case head to bullet tip. It is important because that measurement tells you what will fit in the magazine.

The OAL in the manual is important because that is the SAAMI spec. That is also the OAL that the bullet makers designed bullets to perform best at….powder makers designed loads in the manual to work best at and chamber reamer makers designed the chamber too.

It is likely quite close to the best performing OAL in your gun.

That said, I generally start at the shorter of mag length, max length where neck is fully contacting the bullet or 0.020” off the lands. Powder and OAL can be adjusted from where you start.

[GeauxTide]

Jeesh. There is an old moniker - Don't trivialize the momentous or complicate the obvious. I FL size my cases, use the COL from the manual and go shoot. I don't care to get better than 1/2" for hunting rifles, which multiple calibers (223, 243, 260, 6.5Creed, 6.5-06, 270, 280, 7RM, 308, 30-06, and 338-06) give using this method.

[RC20]

I never worried about 1.5 inches for hunting. Once you get past 300 yards the drop exceeds the group size by a lot. Then you better be rested, have the dope and a scope that reliably adjusts.

As for me, I have found some barrels like the bullet close to the lands and some have shot great set well back.

So put the it has to be up close with Urban legends and people who espouse one size fits all, well, that is how Urban legends get propagated.

A good starting point is .020 off the lands and then work it closer and further away. But sometimes a lot further away. Weatherby set his guns up that way.

I then use the Hornady Ogive tool that mounts on the micrometer to confirm the changes. Tip variation is a bit much.

Keep in mind that RCBS came out with that super precision auto powder dispenser despite the fact that you can't see a .1 difference in a load FPS wise. Its just eye candy for those that like new toys.

I will add in a Caveat on seating and bullet run out. If I Trim the case with a bias to Chamfer (using a Giraud setup) the bullets seat spot on or .003 runout. Some go as much as .005/006 but I have not seen that as a negative on my shooting (at best I am a bit under a 1/2 inch 5 shot group shooter, re-loader.

I do use RCBS Match seating dies mostly.