Cartridge ogive length 300 win mag

[Dale692000]

Good morning all,

My usual source of accurate info and advice, is currently sunning himself in a nice hot country (you know who you are uncle Terry) So thought i'd ask here.

I have a Sabatti Rover Tactical in 300 win mag, and the ogive and overall length seem huge compared to sammi specs of 3.340
My C.O.A.L is 3.700 with a base to ogive of 2.972.

I'm using 208grn Hornady ELDMs

I've used the OAL gauge, this gives me the 2.975 and a 3 thou jump takes it down to 2.972. Seating at this depth means if the round doesn't go off, i actually have to remove the bolt, as the round is too long to come back out the ejection port, and certainly doesn't fit the mag, which is fine, as i'm shooting off a bench and single feeding anway.

I have also stripped the bolt, seated to that depth and the bolt just drops when closing, so it doesn't feel like i'm in the lands, and in fact i need to seat the bullet a further 0.02 of an inch before i get any resistance, and at that length the bullet is almost falling out the end of the case.

These measurements seem ridiculously long, and i'm sure i'm missing something somewhere. I'm fairly new to reloading, and haven't encountered this issue on any of my other rifles. Does anyone have any advice please? It would be greatly appreciated.

Just as an aside, i've put in the above figures into GRT, and using N160 and a starting weight of 68.2grns and approx speed of 2772.8fps and a finish weight of max 70.0 and speed of 2837.3fps

I've attached a screenshot of my GRT in case i'm missing something.

 

[Eric the Red]

SAAMI spec will have been created using a lighter weight bullet, so naturally shorter. I question loading so long. The case neck in a 300WM is short and there needs to be a good depth of bullet in the case (IIRC rule of thumb should be the diameter of the bullet seated). So I think you are creating an issue there. I would also comment that you will find a node getting the same speed with much less powder seating short enough to dare I say it - fit in your magazine and eject in the normal manner? I wouldn't worry about the jump - some rifles respond well to it and it will prevent pressure spikes. Also - a 3 thou jump is really not a jump! You're almost certainly within the measuring error of your equipment. So bring it back, use less powder and have same effect (quite likely more consistently) - and be able to use the rifle as it was intended. Somewhere between the 3.34 and you max mag length will do just fine. HTH

 

[jthyttin]

Quite probably you will find seating depth, that will produce good accuracy with long jump. For som quick'n'dirty instructions refer to e.g.

Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifle.

bergerbullets.com

Loading 3 thou off the lands is not good practice, since minor variance in bullet dimensions (and your loading procedure) will result in great variation to initial powder burn (bullet resistance). I'd advice loading at least 20 thous off. But your post also raises question, how accurately are you using the OAL tool? Or do you use modified case for measurement, and compare that to actual loaded ammo (or dummies)? That could well result in some variation, although 300WM should headspace on the belt. Many shooters adjust their dies so that the headspace from shoulder is minimal (they usually say "headspace from shoulder", but that's only possible if original belt headspace is quite loose).

Usually it's also recommended that you keep about one caliber of bullet in the neck (cylindrical portion, that is). Target shooting it's not necessary to treat that as gospel, but some thought should be given how the bullet is actually holding up there, on top of the cartridge...

 

[Dale692000]

SAAMI spec will have been created using a lighter weight bullet, so naturally shorter. I question loading so long. The case neck in a 300WM is short and there needs to be a good depth of bullet in the case (IIRC rule of thumb should be the diameter of the bullet seated). So I think you are creating an issue there. I would also comment that you will find a node getting the same speed with much less powder seating short enough to dare I say it - fit in your magazine and eject in the normal manner? I wouldn't worry about the jump - some rifles respond well to it and it will prevent pressure spikes. Also - a 3 thou jump is really not a jump! You're almost certainly within the measuring error of your equipment. So bring it back, use less powder and have same effect (quite likely more consistently) - and be able to use the rifle as it was intended. Somewhere between the 3.34 and you max mag length will do just fine. HTH

Thanks for the advice and tips, it's much appreciated.

I did a load of ladder testing at Sammi spec with the same bullet, and got some good SD's of around 6.3-9, unfortunately the best group i could manage was around 0.56 moa at 100 yards and an average speed of 2725fps, which is ok, but probably won't equate well at 1000 yards. Measuring the Ogive was also near impossible as there was so much bullet inside the case lol.

Seating out to the longer length, the bullet actually seats to around the bottom of the shoulder, so don't think that would be an issue.

I'll try seating to the magazine instead, i can't remember the exact length on that, but its somewhere around Sammi spec, and i'll try loading aroun the best nodes i had with the last lot of testing, maybe i can tighten up the groups.

 

[Dale692000]

Quite probably you will find seating depth, that will produce good accuracy with long jump. For som quick'n'dirty instructions refer to e.g.

Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifle.

bergerbullets.com

Loading 3 thou off the lands is not good practice, since minor variance in bullet dimensions (and your loading procedure) will result in great variation to initial powder burn (bullet resistance). I'd advice loading at least 20 thous off. But your post also raises question, how accurately are you using the OAL tool? Or do you use modified case for measurement, and compare that to actual loaded ammo (or dummies)? That could well result in some variation, although 300WM should headspace on the belt. Many shooters adjust their dies so that the headspace from shoulder is minimal (they usually say "headspace from shoulder", but that's only possible if original belt headspace is quite loose).

Usually it's also recommended that you keep about one caliber of bullet in the neck (cylindrical portion, that is). Target shooting it's not necessary to treat that as gospel, but some thought should be given how the bullet is actually holding up there, on top of the cartridge...

hey,

Thanks for the advice, and the berger bullets snippet.

The OAL gauge i'm doing 10 measurements, and then taking the shortest and going back a further 3 thou. There is some variance in the measurements, hence doing it over and over again. The modified case i'm using has been fired in the rifle, so should be fairly accurate, but doesn't fill me with confidence when i'm measuring 10 times and getting 3 or 4 different results over those 10 measures

Seating depth is around 0.45, so i'm good on one calibre of bullet in the neck.

I'll try seating to fit the mag as thats slightly longer than sammi, and adjust powder loads and see if i can tighten up the groups. I was hoping for a 0.2-0.3 MOA at 100, so was disappointed with only a 0.56.

Thanks again for the advice.

 

[jthyttin]

The OAL gauge i'm doing 10 measurements, and then taking the shortest and going back a further 3 thou. There is some variance in the measurements, hence doing it over and over again. The modified case i'm using has been fired in the rifle, so should be fairly accurate, but doesn't fill me with confidence when i'm measuring 10 times and getting 3 or 4 different results over those 10 measures

I use the Stoney Point gauge (which is now Hornady), my method is to ease the bullet very slowly towards rifling. Then I will mark the rod with piece of tape, point the barrel down (100% vertical), drop the rod 2 or 3 times from 1cm height. The rod weighs very little so it's not driving the bullet into rifling. Second or third drop will sound different, and the rod will bounce i.e. bullet is as far as it will go. Then lock the rod. Last step is to take gauge out, point barrel up and drop a piece of lead shot into barrel. If that will not free the bullet, I will refine the process.

Just something I came up with the first few times using the gauge and been sticking to ever since. Been able to get consistent measurements. I use modified cases so the measurement won't be exact anyway, more a reference value.

 

[HandB]

Thanks for the advice and tips, it's much appreciated.

I did a load of ladder testing at Sammi spec with the same bullet, and got some good SD's of around 6.3-9, unfortunately the best group i could manage was around 0.56 moa at 100 yards and an average speed of 2725fps, which is ok, but probably won't equate well at 1000 yards. Measuring the Ogive was also near impossible as there was so much bullet inside the case lol.

Seating out to the longer length, the bullet actually seats to around the bottom of the shoulder, so don't think that would be an issue.

I'll try seating to the magazine instead, i can't remember the exact length on that, but its somewhere around Sammi spec, and i'll try loading aroun the best nodes i had with the last lot of testing, maybe i can tighten up the groups.

Blimey - a group of 0.56 MOA at 100yds is good (assuming it is a sufficient number of shots for statistical significance, such as ten shots). I own some decent rifles and have a background in target shooting and I would struggle to match that. As has been said, seating 3 thou off the lands is a bit close. I seat to 75thou off the lands in my .308s and 7mm Mauser and that works fine so maybe give that a try?

 

[Jagged77]

My 208 Amax load is 3.585” COAL and 2.868” PM - haven’t got the jump fugure off the top but it will be significant. If you’re a new reloader I wouldn’t get too worried about jump, especially if it becomes impractical. Load for safety and functionality unless the loss of accuracy is really noticeable.

 

[Dale692000]

I use the Stoney Point gauge (which is now Hornady), my method is to ease the bullet very slowly towards rifling. Then I will mark the rod with piece of tape, point the barrel down (100% vertical), drop the rod 2 or 3 times from 1cm height. The rod weighs very little so it's not driving the bullet into rifling. Second or third drop will sound different, and the rod will bounce i.e. bullet is as far as it will go. Then lock the rod. Last step is to take gauge out, point barrel up and drop a piece of lead shot into barrel. If that will not free the bullet, I will refine the process.

Just something I came up with the first few times using the gauge and been sticking to ever since. Been able to get consistent measurements. I use modified cases so the measurement won't be exact anyway, more a reference value.

That's a great idea, would never have thought to try it that way. I'll be having a go at that in the morning. Cheers for the info

 

[Dale692000]

Blimey - a group of 0.56 MOA at 100yds is good (assuming it is a sufficient number of shots for statistical significance, such as ten shots). I own some decent rifles and have a background in target shooting and I would struggle to match that. As has been said, seating 3 thou off the lands is a bit close. I seat to 75thou off the lands in my .308s and 7mm Mauser and that works fine so maybe give that a try?

I guess I'm always trying to get better groups, and I'm comparing it to my 6.5 and .223, both of which will shoot 0.3moa groups (10 shot groups) but maybe the win mag just isn't capable of getting the groups. But lots more testing to do before I give up on it.

I'll try seating 75 thou off and see how that goes.

It's just a shame I'm not allowed to shoot my win mag at my club, so I have to book range time at Devizes, and they're fully booked for the 100yards months in advance, so it's really tricky to get lots of testing in.

 

[Jagged77]

Different bullets but an example of how jump is not always a bad thing. In this case it’s at least 150 thou off the lands. 5 shot group with my .300 WM out in the fields on a miserable winters day (which may account for the flier - or it was me). Still, near enough an .5 MOA group. After years of reloading my main take home for accuracy is getting the right bullet and powder combination, everything after that is just tweaks.

 

[Rutland lad]

I guess I'm always trying to get better groups, and I'm comparing it to my 6.5 and .223, both of which will shoot 0.3moa groups (10 shot groups) but maybe the win mag just isn't capable of getting the groups. But lots more testing to do before I give up on it.

I'll try seating 75 thou off and see how that goes.

It's just a shame I'm not allowed to shoot my win mag at my club, so I have to book range time at Devizes, and they're fully booked for the 100yards months in advance, so it's really tricky to get lots of testing in.

A Winmag is capable of getting the groups. All my reloading data has been supplied by a good mate (I’m standing on the shoulders of giants) and it’s been very accurate almost from the off.
My COAL needed to be longer and the accuracy improved.
GECO cases were reloaded multiple times before binning, but as you can see below it did the business. FYI that’s a four round group, the holes in the cardex are from multiple shots of differing ammo. It was a check zero outing with a muzzle brake before a trip to Hungary on boar. And I don’t consider myself a great shot.
Now on LAPUA cases but with same 180 grain Barnes TSX.
Last trip to Scotland I shot 220 Sako Hamnerheads and 220 core bonded by a UK manufacturer. Both still accurate.
Love the WM !

 

[Griffo13]

I have mine set up at 3.505, using 168tmk and 72.5gn of N160. Just a touch over 3000fps with a 24inch barrel. This puts me at 85thou from the lands. Seems to produce the best grouping. That round has been shot out to a mile.