OAL or ogive to lands?

[ColinR]

I feel this is a silly question given that I have been reloading for years, but I learnt the basics loading pistol calibres. I now load rifle calibres in 7.62 and .338LM.

Given that the ogive of rifle bullets from the same batch can differ up to .0010" I tend to set the bullets to a consistent OAL by seating a little high then miking and resetting each one to an exact OAL. This obviously changes the distance between the ogive and the lands, but I still get consistent accuracy in both AI's.

What I'd like to know is a) Is this acceptable reloading practice and b) will I get even better results setting the bullet seater to one length and accepting differences in OAL? I use Sierra 155 grain HPBT and Lapua 170 Lock Base in the 7.62 and Lapua 250 Lock Base in the .338. Seating Tools are RCBS and Redding with micrometer settings. The tips of the Sierra HPBT's are not always consistently formed so I can see this affects the OAL - the Lock Base tips are more consistent being an FMJ. Loading the 7.62 using the OAL method with arguably inconsistently formed tips on Sierra 155 HPBT it shoots to better than a half MOA at 100 yards and will consistently knock out the vbull on Short Siberia - that is with Lapua cases and 44.2 of Vit N140 -acceptable accuracy, but am I doing it right by the book?

It seems that using either method there will be inconsistencies in bullet depth, but maybe .0010" difference has insignificant effect on pressure.

As I say this is not an accuracy issue, at least it seems not to be, but I would be grateful for some guidance on this matter as I have purchased a Hornady guage to measure to the start of the rifling lands and that depends on ogive position rather than OAL.

[DaveT]

Given that Case Head to Bullet tip measures are all but useless for reasons that you have noted (inconsistent manufacturing tolerances) I think that you are doing the right thing by using the Hornady gauge to get as consistent an OAL as is possible by measuring to the Ogive...... its the method that I use and I am happy with it.

There may be slightly better tools out there (but MUCH more expensive!) but could they really hold to better than .001" variation? Even the Ogive is never going to be 100% consistent ... its just better than the tip measurement .... I am happy in getting that level of consistency and don't believe that accuracy would suffer at that level at all.

[ColinR]

Given that Case Head to Bullet tip measures are all but useless for reasons that you have noted (inconsistent manufacturing tolerances) I think that you are doing the right thing by using the Hornady gauge to get as consistent an OAL as is possible by measuring to the Ogive...... its the method that I use and I am happy with it.

Hi Dave I thought that was pretty much the case and possibly I am led slightly astray by the fact my AI 7.62 AWM seems to shoot anything at 100 yds with amazing consistency.

I will certainly try the ogive to lands method - any thoughts of where I should start in terms of distance?

[ColinR]

Given that Case Head to Bullet tip measures are all but useless for reasons that you have noted (inconsistent manufacturing tolerances) I think that you are doing the right thing by using the Hornady gauge to get as consistent an OAL as is possible by measuring to the Ogive...... its the method that I use and I am happy with it.

While on the subject of manufacturing accuracy I bought some Hornady 285 grain .338 HPBT AMP bullets the other day. I cannot believe the accuracy of these bullets in terms of dimension and weight. The ogives are accurate to less than 0001" and they have a BC up in the .700's. I have never seen bullets with such consistency and can't wait to try them. Only problem is I tend to use only Vit powder, either N165 or N560 for .338 LM, and can't find any load details for this combination.

[DaveT]

Given that Case Head to Bullet tip measures are all but useless for reasons that you have noted (inconsistent manufacturing tolerances) I think that you are doing the right thing by using the Hornady gauge to get as consistent an OAL as is possible by measuring to the Ogive...... its the method that I use and I am happy with it.

Hi Dave I thought that was pretty much the case and possibly I am led slightly astray by the fact my AI 7.62 AWM seems to shoot anything at 100 yds with amazing consistency.

I will certainly try the ogive to lands method - any thoughts of where I should start in terms of distance?

There are two schools of thought..... one is to start ON the lands (particularly with VLD bullets) at lowered powder charges and work BACK if accuracy not apparent.

The other is obviously the reverse.... I have been starting at .020" off of the lands and creeping inward but am serously considering going the other way as most bullets are likely to show better accuracy close to the lands even if they are Tangent Ogive / Jump tolerant.... so logic indicates starting very close to or ON the lands with the usual caution re powder charges starting a tad lower due to initial startup pressures.

[Sim G]

it shoots to better than a half MOA at 100 yards and will consistently knock out the vbull on Short Siberia - .

Forgive me Colin if this comes across blunt, but you're trying to build a better mouse trap......

The AI, as good and accurate a rifle that it is, it's not a bench rest gun, nor will it ever be. Likewise, you won't get bench rest accuracy from it. Have you gone out further than 200m of Short Siberia?

You will reach the point of diminishing returns. The effort you put in will no way equal the output. A half inch at 100 (5 rounds, outside edge to outside edge?) would have been regarded as somrthing phenominal 15 years ago, people forget, out of a factory gun it is still phenominal.....

If ogive to lands, meplat trimming or crush fit is all part of the extended hobby of handloading, then fill ya boots!! Looking to have a .308 laser, I'd say don't waste your time, be happy with a really accurate load for a really accurate rifle.

[ColinR]

[quote

There are two schools of thought..... one is to start ON the lands (particularly with VLD bullets) at lowered powder charges and work BACK if accuracy not apparent.

The other is obviously the reverse.... I have been starting at .020" off of the lands and creeping inward but am serously considering going the other way as most bullets are likely to show better accuracy close to the lands even if they are Tangent Ogive / Jump tolerant.... so logic indicates starting very close to or ON the lands with the usual caution re powder charges starting a tad lower due to initial startup pressures.[/quote]

When I tried the Hornady guage, a bit rushed I must admit, the indicated OAL to the lands with a 155 grain Sierra HPBT was increased by what appeared a disproportional amount and possibly resulted in cartridge that would no longer fit the magazine - I didn't measure the OAL, but visually the bullet was sitting a lot further out of the case. This is partly why I didn't pursue the matter further as I was already getting acceptable accuracy. I think I need to spend some real time assessing the measurements and options because I think the 7.62 barrel (Walther I believe) has a long throat presumably to accommodate the dimensions of variable military cartridges with different weight bullets with different ogive position. I will take some measurements with different bullet types (155 Sierra and 170 Lock Base) and see where that takes me. Thanks for the input.

[ovenpaa]

While on the subject of manufacturing accuracy I bought some Hornady 285 grain .338 HPBT AMP bullets the other day. I cannot believe the accuracy of these bullets in terms of dimension and weight. The ogives are accurate to less than 0001" and they have a BC up in the .700's. I have never seen bullets with such consistency and can't wait to try them. Only problem is I tend to use only Vit powder, either N165 or N560 for .338 LM, and can't find any load details for this combination.

QL suggests a maximum load of 82.5 grains of N560 with standard build dimensions, if you can give me your OAL to the meplat, case capacity and barrel length I can give a more accurate figure.

Regarding your original question measuring from the Ogive is always going to give more accurate results even with the Lockbase (Great bullets BTW!) The issue with using an OAL gauge and rimless brass is you are referencing from the shoulder to the ogive, not the head to ogive so a very short distance. Fine in principle though as it gives you a measurement in time. Better to measure from the bolt face to the ogive as the bolt face is a constant. I have built a couple of OAL gauges that emulate this but I am yet to come up with the definitive gauge due to the differences between rifle models.

In my opinion there is not an ideal solution on the market right now, certainly not one that takes throat erosion into account and that for me is an important factor.

[ColinR]

it shoots to better than a half MOA at 100 yards and will consistently knock out the vbull on Short Siberia - .

Forgive me Colin if this comes across blunt, but you're trying to build a better mouse trap......

The AI, as good and accurate a rifle that it is, it's not a bench rest gun, nor will it ever be. Likewise, you won't get bench rest accuracy from it. Have you gone out further than 200m of Short Siberia?

You will reach the point of diminishing returns. The effort you put in will no way equal the output. A half inch at 100 (5 rounds, outside edge to outside edge?) would have been regarded as somrthing phenominal 15 years ago, people forget, out of a factory gun it is still phenominal.....

If ogive to lands, meplat trimming or crush fit is all part of the extended hobby of handloading, then fill ya boots!! Looking to have a .308 laser, I'd say don't waste your time, be happy with a really accurate load for a really accurate rifle.

Hi Sim G You know that's pretty much what I have been thinking. I have no problems with the accuracy even at 900m using the Lock Base bullets. I suppose its more a case of knowing and then doing what works. Not blunt in the least, just good solid down to earth advice, thanks. Colin

[ColinR]

[/quote]QL suggests a maximum load of 82.5 grains of N560 with standard build dimensions, if you can give me your OAL to the meplat, case capacity and barrel length I can give a more accurate figure.[/quote]

Hi ovenpaa thanks for the offer. I'm not sure what the OAL should be for these Hornady .338 HPBT bullets, they are very long! I will measure one to 20 thou off the lands and see what that comes out at. The barrel is standard AI .338 Lap Mag, 27" and has had less than 100 rounds through it so the throat should still be OK. Not sure of case capacity, having only ever used weight as a measure, but assume new Lapua brass. Not at home at the moment so unable to be more specific on some points.
'Scuse my ignorance, what is "QL"?