Proper ad best cartridge to ogive length for rifle reloads

[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!

 

[Ruger 15151]

The answer is.... it depends. SMK's tangent bullet shape was specifically designed for the military because it needed to be able to be loaded to magazine length and not be sensitive to large bullet jump. In most rifles, accuracy isn't effected whether you load SMKs to mag length or closer to the lands. However, if you are loading bullets with a secant (narrow) ogive like VLD bullets, they are very sensitive to bullet jump and typically like to be loaded much closer to the lands. Many long rang shooters now load these bullets because of their great BC numbers. However, you generally have to single feed them because they must be loaded too long to fit in the magazines.

So..... if you are not sure which bullets and bullet jump your rifle prefers, you might considered loading SMKs to the same length as the FGMM. If the FGMM shot well in your rifle, google that load and you can have the same reloads. Just be careful to start 10% lower and work you way up looking for pressure signs along the way.

Hope that helps

 

[DrJoe1]

The answer is.... it depends. SMK's tangent bullet shape was specifically designed for the military because it need to be able to be loaded to magazine length and not be sensitive to large bullet jump. In most riffles, accuracy isn't effected whether you load SMKs to mag length or closer to the lands. However, if you are loading bullets with a secant (narrow) ogive like VLD bullets, they are very sensitive to bullet jump and typically like to be loaded much closer to the lands. Many long rang shooters now load these bullets because of their great BC numbers. However, you generally have to single feed them because they must be loaded too long to fit in the magazines.

So..... if you are not sure which bullets and bullet jump your rifle prefers, you might considered loading SMKs to the same length as the FGMM. If the FGMM shot well in your rifle, google that load and you can have the same reloads. Just be careful to start 10% lower and work you way up looking for pressure signs along the way.

Hope that helps

Yes, it does. Thanks so much!

 

[sparkyv]

Excellent advice:

The answer is.... it depends. SMK's tangent bullet shape was specifically designed for the military because it needed to be able to be loaded to magazine length and not be sensitive to large bullet jump. In most rifles, accuracy isn't effected whether you load SMKs to mag length or closer to the lands. However, if you are loading bullets with a secant (narrow) ogive like VLD bullets, they are very sensitive to bullet jump and typically like to be loaded much closer to the lands. Many long rang shooters now load these bullets because of their great BC numbers. However, you generally have to single feed them because they must be loaded too long to fit in the magazines.

So..... if you are not sure which bullets and bullet jump your rifle prefers, you might considered loading SMKs to the same length as the FGMM. If the FGMM shot well in your rifle, google that load and you can have the same reloads. Just be careful to start 10% lower and work you way up looking for pressure signs along the way.

Hope that helps

 

[lordpaxman]

@Ruger 15151 gave some great advice, but I’d still be tempted to do a lands test on the reloads once I determined what node I’d use.

 

[Demi-human]

I would try to match the factory rounds. Stay away from the lands. Until you have a firm understanding of why you want to and what could happen, don’t load into the lands.

As evidenced, the Federal shoots very well seated where it is.

Now, once your work up is under way, yes working towards the lands via seating depth is a test that can be done.
The course tuning is the powder charge, the fine tuning of seating comes after a nice repeatable charge weight node is found.

Sometimes the C.O.A.L. is dictated by the magazine length instead of the C.B.T.O., too.


Nice rifle, enjoy it!