6.5CM Reloading Question

[Oregonlaw76]

All - New to reloading and starting with my 6.5CM. Have a good start with 147g ELD match with 38-40g H4350. Everything I see says base to tip should be 2.8” ish. I used a Hornady OAL and modified case numerous times and got 2.65 oal consistently to the lands. So .020 off lands to start got me 2.63 and I loaded 12 rounds ladder of powder charges.

Now I’m second guessing myself. Did I screw something up and need to remeasure and reload my initial rounds? Or is it possible that is accurate (though short) OAL”?

Thanks in advance.

 

[Nimothy]

Your coal is 2.65? Or base to ogive is 2.65?

 

[powerspc]

All - New to reloading and starting with my 6.5CM. Have a good start with 147g ELD match with 38-40g H4350. Everything I see says base to tip should be 2.8” ish. I used a Hornady OAL and modified case numerous times and got 2.65 oal consistently to the lands. So .020 off lands to start got me 2.63 and I loaded 12 rounds ladder of powder charges.

Now I’m second guessing myself. Did I screw something up and need to remeasure and reload my initial rounds? Or is it possible that is accurate (though short) OAL”?

Thanks in advance.

I think you are confusing Cartridge Overall Length (C.O.L.) and Cartridge Base To Ogive (C.B.T.O). The COL is base of cartridge to tip of loaded round, the CBTO is base of cartridge to the Ogive. The Horandy gauge is telling you the distance from the base of the cartridge to where the Ogive is touching the lands in your rifle not COL. It is not possible for the COL to be 2.800 and the CBTO to be 2.65.

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 2

The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another measure of length for loaded ammunition which is highly important to precision.

bergerbullets.com

 

[spife7980]

I don’t thunk he is confused at all. His bullets are hitting the lands .15 earlier than he expected (that’s .15 earlier via either method)

I suspect its due to runout or something off center and you’re hitting one side earlier than the other.
What number did you get if you gave it a health jam instead of trying to find first touch?

Color the nose/bearing surface transition in sharpie and see if you get imprints on all sides evenly spaced or it it’s dragging it off of one side only.

 

[powerspc]

I don’t thunk he is confused at all. His bullets are hitting the lands .15 earlier than he expected (that’s .15 earlier via either method)

I suspect its due to runout or something off center and you’re hitting one side earlier than the other.
What number did you get if you gave it a health jam instead of trying to find first touch?

Color the nose/bearing surface transition in sharpie and see if you get imprints on all sides evenly spaced or it it’s dragging it off of one side only.

You know you may be right; I think what was confusing me is that with the Hornady gauge you're usually measuring the CBTO not the COL. You can measure the COL with that gauge but I don't think that was its intended purpose or probably as accurate(?).

 

[BBVDD]

Everything I see says base to tip should be 2.8” ish. I used a Hornady OAL and modified case numerous times and got 2.65 oal consistently to the lands. So .020 off lands to start got me 2.63 and I loaded 12 rounds ladder of powder charges.

Is your gun a BA or gas gun?
I can’t see any possible way the chamber is that short.
if it’s a BA you need to remove the firing pin and seat a bullet long and slowly work down the length until your bolt freely falls to find the correct length to lands.

 

[spife7980]

Is your gun a BA or gas gun?
I can’t see any possible way the chamber is that short.
if it’s a BA you need to remove the firing pin and seat a bullet long and slowly work down the length until your bolt freely falls to find the correct length to lands.

That has nothing to do with the oal gauge results.

 

[918v]

Maybe he meant 2.85”? Typo?

 

[BBVDD]

That has nothing to do with the oal gauge results.

There is no way possible his chamber is that short.
None

 

[Billl223]

I have an older Hornady O.A.L. gage that I used on my Tikka 6.5. The OAL was 2.93 with a Hornady 140 ELD Match bullet touching the lands. The length of the factory load was 2.81. I tried various lengths including 2.92 OAL and generally saw no improvement but did load up some @ 2.83 to try as that showed the most promise.

 

[Oregonlaw76]

I appreciate all the responses. No typo, that's why I'm concerned. It sounds like I made an error. I don't think I mixed Ogive with COAL, but just to make sure my process was:

Attached modified 6.5 CM case to OAL gauge and took out bolt (Rifle is bolt action Tikka with Krieger bbl)
Grabbed one of three Hornady 6.5CM 147g ELDM bullets and inserted into modified case
Backed bullet way into casing and inserted casing into chamber until full stop
Pushed grey insert to push bullet fully forward until full stop and use thumb screw to hold measurement
Remove gauge and ensure bullet is against grey insert and then measured base to tip
Repeated that process 2 more times with that bullet, and then repeated 3 more times for each of 2 other bullets from the same pack.
Measurements were all in the 2.647 to the 2.655 range so I settled on 2.65 length tip to base is touching the lands, so I loaded to 2.63 tip to base.

From the comments sounds like somehow I wasn't getting the full measurement and this is way too short.

 

[918v]

The problem is if your chamber was really this short, you would not be able to close the bolt on a factory round.

 

[918v]

If you want to test this theory, make a dummy round at 2.810” and try to chamber it.

 

[Oregonlaw76]

Thank you, I’ve shot probably 60 factory rounds no problem. I just went and measured, and they fall about 2.81. So I think that reaffirms I somehow got short measurements.

 

[powerspc]

For some reason this is hurting my head or I'm just not understanding. You don’t measure cartridge base to tip of bullet with the Hornady OAL gauge. What you’re trying to measure is the Cartridge base to where the ogive hits the rifling. You do this with a set of calipers and the attachment that came with the Hornady gauge attached to those calipers and then in your case with the 5-26 insert attached. This measures from the base to the ogive or CBTO. This is the measurement you want. Then you can back that measurement off .020 if that’s where you want to start. If you’re measuring from base to tip of bullet, that is incorrect.

 

[Tokay444]

Please post pics of how you’re measuring whatever it is you’re measuring.

 

[Oregonlaw76]

I went and bought a Hornady bullet comparator, remeasured per above posts, and getting reasonable measurements. Consistently 2.895 COL so will start at 2.875 for my first reloads and work from there. I appreciate the assistance.

 

[powerspc]

you’re still saying COL which is wrong, you want the CBTO not the COL. anyway, good luck.

 

[cm1021]

Yeah my head is hurting trying to understand. There are TWO different hornady gauges that you need to be using. One with the modified case will give you the maximum length for YOUR chamber for the bullet to touch the lands. (Side note. You need to make sure that your chamber is clean and that the case is completely seated.) The other gauge measures off of the ogive. This will give you cbto(cartridge base to ogive). You use both of these to find your lengths. You want to measure off of ogive vs tips as there is more variance in bullet tips vs ogive datum point.

Hopefully you're not too confused. If you have any questions shoot me a PM. I'll try to help best I can

 

[MudMuppet]

 

[SFeldt]

I found that Hornady eld bullets like a decent jump. I would start in the .030-.060 range

 

[spife7980]

For some reason this is hurting my head or I'm just not understanding. You don’t measure cartridge base to tip of bullet with the Hornady OAL gauge. What you’re trying to measure is the Cartridge base to where the ogive hits the rifling. You do this with a set of calipers and the attachment that came with the Hornady gauge attached to those calipers and then in your case with the 5-26 insert attached. This measures from the base to the ogive or CBTO. This is the measurement you want. Then you can back that measurement off .020 if that’s where you want to start. If you’re measuring from base to tip of bullet, that is incorrect.

Yeah, youre just not understanding.
You can totally take oal measurements with the hornady oal tool. Its in the damn name.

Whether you measure base to ogive or base to tip your choice between those two is a complete independent variable than what hes talking about, his measurement would be .15 short on either coal or cbto.

I agree that the base to ogive is a better point of measure but thats neither here or there when both measurements would be .15 short, doesnt matter what the number displayed is if its not in relation to the lands or the mag length. COAL is not "incorrect"



So OP, and to other people who dont know what they are talking about: The nose of the bullet where the copper gets pinched down can vary more than the full diameter bearing surface of the bullet. As such measuring off of the most consistent part of the bullet is preferred over the part that varies more. The ogive is technically the entire curvature of the nose but for reloading we care about where the bullet actually touches the barrel which is right in front of the full diameter on the nose.

So the part labeled jump is going from the bullets bearing surface right just on the ogive to the lands where the barrels rifling begins which is where the bullet meets the barrel. When you are using the oal tool you are trying to find the point where the bullet touches the lands and you have zero jump so that you know where your bullet actually is in relation to the chamber.

In your creed your barrel will have a .256 hole and then it will have some extra material scooped out to a .264 measurement. The bullet comparator is cut to measure right about on that ogive spot in the middleish of the lands, it should be something like a .260 hole with a slight amount of taper which puts you pretty close to the middle.

Different bullet shapes will have different over all lengths and positioning from one another when measured from a consistent point such as the ogive. So the COAL number for an ELD bullet wont equal a number for a SMK bullet.

.

So to help diagnose the problem OP, follow 918s post about seating one long to see if it fits. I would also color the bullet with sharpie and the case neck and shoulders to see if its dragging prematurely somewhere.
You could have a varmint reamer with very little freebore by design or possibly a reamer with no freebore intended to be followed by a throating reamer so to say its impossible is wrong too. But more likely its off center, fat case necks, just dragging, could be any number of things. Sharpie is a nice visual indicator of what or at least where its hitting inside the chamber out of sight.

 

[Steel head]

Professor spife has spoken!

 

[cm1021]

Yeah listen to spife. He explained it WAY better than I wasnt trying to. But that's exactly what you need to do and know.

 

[MudMuppet]

Dropping knowledge, I understand the difference, but this is the best explanation I’ve ever seen

 

[powerspc]

Yeah, youre just not understanding.
You can totally take oal measurements with the hornady oal tool. Its in the damn name.
View attachment 7328207




Whether you measure base to ogive or base to tip your choice between those two is a complete independent variable than what hes talking about, his measurement would be .15 short on either coal or cbto.

I agree that the base to ogive is a better point of measure but thats neither here or there when both measurements would be .15 short, doesnt matter what the number displayed is if its not in relation to the lands or the mag length. COAL is not "incorrect"



So OP, and to other people who dont know what they are talking about: The nose of the bullet where the copper gets pinched down can vary more than the full diameter bearing surface of the bullet. As such measuring off of the most consistent part of the bullet is preferred over the part that varies more. The ogive is technically the entire curvature of the nose but for reloading we care about where the bullet actually touches the barrel which is right in front of the full diameter on the nose.
View attachment 7328227



So the part labeled jump is going from the bullets bearing surface right just on the ogive to the lands where the barrels rifling begins which is where the bullet meets the barrel. When you are using the oal tool you are trying to find the point where the bullet touches the lands and you have zero jump so that you know where your bullet actually is in relation to the chamber.
View attachment 7328229

In your creed your barrel will have a .256 hole and then it will have some extra material scooped out to a .264 measurement. The bullet comparator is cut to measure right about on that ogive spot in the middleish of the lands, it should be something like a .260 hole with a slight amount of taper which puts you pretty close to the middle.
View attachment 7328236



Different bullet shapes will have different over all lengths and positioning from one another when measured from a consistent point such as the ogive. So the COAL number for an ELD bullet wont equal a number for a SMK bullet.
View attachment 7328222.

View attachment 7328223
View attachment 7328225




So to help diagnose the problem OP, follow 918s post about seating one long to see if it fits. I would also color the bullet with sharpie and the case neck and shoulders to see if its dragging prematurely somewhere.
You could have a varmint reamer with very little freebore by design or possibly a reamer with no freebore intended to be followed by a throating reamer so to say its impossible is wrong too. But more likely its off center, fat case necks, just dragging, could be any number of things. Sharpie is a nice visual indicator of what or at least where its hitting inside the chamber out of sight.

Thanks Spife, I learned some things as well! I've just always used CBTO as the measurement not worrying about the COL unless my seated bullet didn't fit the magazine. But your explanation makes perfect sense to me now. Much appreciated! Sorry to the OP as well, what I probably should have said is "less accurate" as opposed to "wrong". Apologies also if I 'semi'-hijacked the thread!

 

[Oregonlaw76]

Great forum, all very helpful. Measuring the CBTO with the comparator got me on the right track (and out shooting) and I’ve gone back now based on all this information and duplicated the results using COL as well. Amazing how understanding the concepts makes executing the process easy. My theory on the bad initial results (as someone mentioned) is that I was starting with the bullet too far in the modified case so when I pushed it forward it was canted and the tip was catching a groove or land prior to straightening out. Either way, heading back to the range today. Thank you all.