Base to ogive very long

[nyyankeedr]

I measured my base to ogive length for my 308 Winchester action and is coming out to between 2.302 to 2.357 for 3 different 150-165 gr FMJ bullets. This is a huge distance to my rifling as this measurement barely allows the bullet to be seated in the neck by only a few mm. Base to ogive of the factory loads, 150 gr Hornady SST for example, is 2.126. This seems like a problem. Clearly, no way for me to get anywhere near my ogive length unless I exceed overall case length. Do I just not worry about this much space for the projectile to jump? I am shooting a Remington 700 SPS Tactical with heavy 10:1 barrel. Thoughts on what to do?

 

[GlennK]

I am a little confused on what you are measuring. Factory base to ogive will most likely be jumping a bullet in most barrels. Is this a factory or smithed barrel and how are you measuring your lands? Different projectiles have different base to ogive measurements depending on the bullet radius....they will not be the same touch number.

 

[Dusty Stevens]

Jump it and see what happens

 

[Ned Ludd]

Assuming you intend to feed from a magazine, determine for the various bullets the longest COAL you can safely and reliably feed from the mag, set that as your maximum CBTO reference point, then test seating depth only in the direction of further increasing the distance from the lands (i.e. CBTO will only decrease from the reference point). You may need to test a wider seating depth range in this scenario than you ordinarily might, but you should nonetheless be able to optimize seating depth, even with the substantial jump. Just keep an eye out for pressure signs as you move the bullet farther and farther off the lands as that will reduce the effective case volume and increase pressure at a given charge weight.

 

[Doghed]

I'm shooting a similar rifle. Rem 700 VLS 308. When I started reloading for that rifle I measured the freebore and realized that in order for the 175 SMK's to touch the lands there would be little to none of the bullet bearing surface being gripped by the neck. I kind of expected this especially from a factory 308 chamber as it has to be able to accommodate many different projectiles. I don't worry about the big jump. I seat to just over SAAMI (2.800) to 2.810 OAL. Works great. I figure eventually it will be time to set the barrel back and I will have it chambered specifically for the 175 or similar projectile then I can start playing with seating depth and jump/jam.

 

[CharlieNC]

It is often suggested to evaluate seating depth in small increments, eg .002-.005, from the jamb to find best accuracy. I had a situation similar to yours and was also unhappy with the results so I ran the trial suggested by Berger with jumps of .005, 040,.080,.120 and found major improvement at much longer jumps than most would generally consider. And this for vld bullets that everybody knows should be jambed! Try it to find a better starting point for fine tuning.

 

[STOMP442]

The Remington 308s have a notoriously long free bore. I have messed with three or four of them over the last few months. I could barely reach the lands with 185 Bergers and still keep some bullet in the neck. I always like to get a length to lands measurement just for reference but since these were hunting rifles I just set everything to fit the mag. Some rifles shot fantastic and didn't seem to mind the jump with a variety of bullets. Others were very temperamental and was a pain to find the bullet/powder combo they liked. Could be the large jump or just the win some loose some factory Remington barrel quality. Hard to say.

 

[nyyankeedr]

I am a little confused on what you are measuring. Factory base to ogive will most likely be jumping a bullet in most barrels. Is this a factory or smithed barrel and how are you measuring your lands? Different projectiles have different base to ogive measurements depending on the bullet radius....they will not be the same touch number.

Measuring with the Hornady L-n-L OAL length gauge using a 308 modified cartridge. I understand that different factory rounds will give different measurements. I was only including a range to show that no matter which I use, I get a significantly longer measurement than many suggest is ideal for best accuracy. In other words, the throat is so long, is there something I need to do or can do to improve that? or should I just not worry about it as so many have suggested here?

 

[GlennK]

It sounds like you will be stuck with the long freebore and jumping the bullets, which may shoot just fine. As suggested above, If you are using a magazine, start your load development with seating that will feed from it. Many, including myself, have developed a load only to find out it is too long to run from the magazine.

 

[JFrank]

Measuring with the Hornady L-n-L OAL length gauge using a 308 modified cartridge. I understand that different factory rounds will give different measurements. I was only including a range to show that no matter which I use, I get a significantly longer measurement than many suggest is ideal for best accuracy. In other words, the throat is so long, is there something I need to do or can do to improve that? or should I just not worry about it as so many have suggested here?

Where did you get the modified case?

 

[nyyankeedr]

Where did you get the modified case?

Cabelas/Bass Pro shop.

 

[JFrank]

Cabelas/Bass Pro shop.

Ok ‘just being sure.

 

[338 dude]

Have a case made from your fired brass it will give you a much more accurate measurement

 

[Coyotefurharvester]

^^^^This ^^^^^

 

[3Sigma]

Par for the course with a Rem 700 SPS Tac. I have the same rifle. My only suggestion is to use jump tolerant bullets. It can shoot. Here's a target from my break-in rounds this spring using the load setup from my Savage 10. This is set to FGMM Cartridge Base to Ogive lengths (2.215" on my Hornaday Comparitor), but on the Savage it is .003" off the lands and over .100" in this rifle.


Here are the first three groups of break-in. 175 FGMM, 147 Winchester white box, and 168 FGMM, top to bottom


TLDR, don't sweat the jump, just use tolerant bullets and tune from there.

 

[divingin]

In other words, the throat is so long, is there something I need to do or can do to improve that? or should I just not worry about it as so many have suggested here?

You can change out the barrel.

Alternatively, you can ask a smith to lop a bit off the back, rechamber, rethread, and re-shoulder the original barrel, but, given that the factory barrels aren't great to begin with, I wouldn't think that would be cost-effective.

With the factory Rem barrel, I found the Matchkings shot pretty well despite the long throat (they seem to be fairly jump-tolerant.) I gave up on shooting from the magazine, though, and single loaded everything really long (I'm just shooting paper, so no need for quick followup shots or anything like that.) How you decide to run depends on what you're trying to do with it.