Best cartridge base to ogive length for rifle loads

[DrJoe1]

Hi All,
I am new to the forum and working on my first reloads in .300 Win Mag for an AI AXMC and aiming for accuracy. I have the rifle zeroed using commercial Federal Gold Match 190g SMK. The Federal rounds are 3.330" in C.O.A.L. and have a cartridge base to ogive distance of 2.743". My rifle chamber's C.O.A.L. is 3.506" and when sized using a dummy round that is just to the lands, the cartridge to ogive distance is 2.907". So, the question is "Do I size my reloads to equal the Federal Gold Match cartridge to ogive length, or do I size the reloads slightly shorter than the cartridge to ogive length that exactly fits the actual chamber? Or do I try a series of cartridge to ogive lengths, each incrementally shorter starting at 2.907" until I reach the Federal length, and go with whichever works best? The rifle runs perfectly and accurately with the Gold Match factory ammo (<0.5 MOA at 100yds). Appreciate the help before loading powder and seating the bullets. Thanks!

 

[RegionRat]

Okay, I see your question hasn't been answered. I am a little surprised as I am sure many are sort of locked down in the quarantine and should find themselves with more time to answer than normal...

Read this article, and the other ones it leads to. It will answer your current question and the ones you haven't asked yet.

https://precisionrifleblog.com/2020/04/15/18-shot-bullet-jump-challenge/

Yes, you will need to try to first match the factory performance as a baseline, then see if you can do better.

When you know your equipment and skills are up to the point where you can tell the difference between the factory and your loads, then start on the things you learned from the linked articles.

Many times, jump values can show multiple node where good performance in terms of group size is found. The point in the article is that you will decide for yourself which one to chase, and not to be afraid of using the longer jump values just because the herd is all running short ones.

There really isn't anything new about chasing lands, or having lots of freebore jump. The Weatherby Magnum factory guns were known for having long jumps and were above average for off the shelf accuracy in belted magnums. Another point is that chasing lands as the wear can mean a narrower node dimension when compared to a longer one. You will have to decide which one you like when you have mapped them out.

Good Luck and ask more questions when you need to.

 

[piie]

The factory ammo is always going to be loaded “short” in order to ensure they can fit in a magazine. If you are not hunting, or have a custom rifle, then your optimal COAL will most like be longer, but ultimately limited by physical dimensions like the length of bullet/bearing surface

 

[dgeesaman]

Or do I try a series of cartridge to ogive lengths, each incrementally shorter starting at 2.907" until I reach the Federal length, and go with whichever works best?

I like this plan.

David

 

[338 dude]

Your results will be dependent on your chamber and your rifle Also the bullet that you were shooting is very important in my 300 WinMag I shoot the burger 185 juggernaut and found best results .020 off the lands

 

[spclark]

I’ve found 0.020” off the lands works good enough for my score shooting (match sights, sling-supported, shooting prone off a mat on the ground) with the Bergers I’ve been using for nearly ten years now, and the SMK’s I’d used before.

So I’d start there, then see if you need to change anything.

Shooting a 300WM doesn’t lend itself to extensive load-testing protocols, either because of recoil (I had one once, for about four months), because of costs for components, because of fairly limited barrel longevity... more likely all three ganging up on you over time.

If you’re happy with what the FGM stuff gives you in your rifle, strive to duplicate that. Going much deeper’s probably not going to yield a better long-term solution unless you’re really lucky.

 

[coldboreshot]

The factory ammo is always going to be loaded “short” in order to ensure they can fit in a magazine. If you are not hunting, or have a custom rifle, then your optimal COAL will most like be longer, but ultimately limited by physical dimensions like the length of bullet/bearing surface

+1, and the length of the magazine.

 

[Webster]

Okay, I see your question hasn't been answered. I am a little surprised as I am sure many are sort of locked down in the quarantine and should find themselves with more time to answer than normal...

Read this article, and the other ones it leads to. It will answer your current question and the ones you haven't asked yet.

https://precisionrifleblog.com/2020/04/15/18-shot-bullet-jump-challenge/

Yes, you will need to try to first match the factory performance as a baseline, then see if you can do better.

When you know your equipment and skills are up to the point where you can tell the difference between the factory and your loads, then start on the things you learned from the linked articles.

Many times, jump values can show multiple node where good performance in terms of group size is found. The point in the article is that you will decide for yourself which one to chase, and not to be afraid of using the longer jump values just because the herd is all running short ones.

There really isn't anything new about chasing lands, or having lots of freebore jump. The Weatherby Magnum factory guns were known for having long jumps and were above average for off the shelf accuracy in belted magnums. Another point is that chasing lands as the wear can mean a narrower node dimension when compared to a longer one. You will have to decide which one you like when you have mapped them out.

Good Luck and ask more questions when you need to.

I never jam a bullet on my Varmint rifle. If you have to extract a loaded round in the field or firing line you will dump powder into the chamber and trigger area. Almost impossible to clean and continue firing at the firing line. If the range officer calls a cease fire you have to open the bolt.

 

[Ackman]

I never jam a bullet on my Varmint rifle. If you have to extract a loaded round in the field or firing line you will dump powder into the chamber and trigger area. Almost impossible to clean and continue firing at the firing line. If the range officer calls a cease fire you have to open the bolt.

Yes. Out varmint shooting, unchambering a round isn't too uncommon. Do that with bullets jammed and it's not if, but when one will stick. Pretty much ends shooting with that rifle unless there happens to be a complete cleaning setup brought along. Still a pita getting the powder out. I've learned this the hard way, a couple times.

 

[Steve Ladino]

190 SMK , 69.3grains IMR 4350, Fed. 215 Mag. G M Primer, FF Federal 08 brass, .010 off lands, = <.350" c/c @ 100 yds. This works for me in a 9 twist.

 

[Richard Coody]

Hi All,
I am new to the forum and working on my first reloads in .300 Win Mag for an AI AXMC and aiming for accuracy. I have the rifle zeroed using commercial Federal Gold Match 190g SMK. The Federal rounds are 3.330" in C.O.A.L. and have a cartridge base to ogive distance of 2.743". My rifle chamber's C.O.A.L. is 3.506" and when sized using a dummy round that is just to the lands, the cartridge to ogive distance is 2.907". So, the question is "Do I size my reloads to equal the Federal Gold Match cartridge to ogive length, or do I size the reloads slightly shorter than the cartridge to ogive length that exactly fits the actual chamber? Or do I try a series of cartridge to ogive lengths, each incrementally shorter starting at 2.907" until I reach the Federal length, and go with whichever works best? The rifle runs perfectly and accurately with the Gold Match factory ammo (<0.5 MOA at 100yds). Appreciate the help before loading powder and seating the bullets. Thanks!

Only seating test in your rifle will tell you your best seating depth.

Sizing brass for belted magnums requires a little extra care. Headspace off the shoulder not.the belt. If.you don't understand what I am talking about then you need to do a little research.