Stuck at low velo for .308

N

nik f.

Inactive
I am new to this forum and while I see a lot of really great info out here I haven't seen anyone address the issue I have been having with my .308 so here goes:

Last fall I bought a used Remington 700 varmint in .308 1-12". The previous owner upgraded the stock to an HS Precision PSV002. I have since added a Timney trigger set to 1.5lbs and a Millet TRS-1 set in Leupold rings.

This is my first centerfire rifle and I am blown away with how accurate it can be at 100-200yds using my reference handload of 38.1gr Varget behind a 175 Sierra MK in Lapua brass using pretty much any primer. (best day out so far was five shots 3/8" c2c)

This load gets me sub MOA all the time but it is pretty slow and I suspect that is the cause of my groups opening up once I get out past 200 yds. I have tried different powders and bullet weights but any time I try to push the velocity past 2400fps, accuracy drops way off. I am a paper hunter so I don't have any specific need for higher velocity for short range but I have access to a range out to 500yds that I would like to play around with and I think I am being limited by my accuracy fall-off.

So my question: Do need to just accept that my rifle will only shoot well with low velo loads or are there directions I can go with my load development/other things I can try? (BTW accuracy with factory ammo is also terrible!)
 
Hodgdon.com 's reloading data center lists the *starting* charge as several grains higher than your load.

which manual did you base your load off of?
 
Sierra's. See attached screenshot. Their starting load is 36.3 @ 2200fps.
 

Attachments

  • 175 smk.PNG
    175 smk.PNG
    44.1 KB · Views: 69
Huh... Sierra's max load is lower than Hodgdon's starting load.

Both use the 175gr MK HPBT. I have seen this in other manuals, but nothing this drastic.

Its almost the same story for IMR4895.

Ineteresting.
 
The guy I bought it from stated his developed load was 168 SMK, 45gr Varget but when I tried that I got some head damage from the ejector and backed right off that load.
 
Not that I don't believe the OP, but 6mmBR has posted Sierra's .308 win load data and the OP is spot on.

Huh. I have seen variation between load manuals, but never a case where the data didn't at least overlap.
 
Per Serria's Load Data 45gr is over the max charge of Varget.

And yet Hodgdon lists the 168gr MK BTHP with starting charge of 42 and a max charge of 46.

Are you seating your bullets into the lands?
 
I measured the chamber using the 175 SMK and got something around 2.94in. Apparently Remington's chamber is "lawyered up" according to some posts I've seen. So instead of running the risk of leaving too little bullet in the neck of the case I have gone with the recommended OAL of 2.80in.
 
I dont think Remington's chamber is "lawyered up." I think Remington realizes that those shooting .308 are shooting heavier bullets now than they did 20 years ago.
 
Might be. In any case I wasn't so sure of the safety of seating a bullet more than .10" longer than recommended.
 
More Twist

I'd be real concerned about a 1-12 twist stabilizing a 175 Gr. bullet . I've always thought of 1-12 as a Palma twist , 155 Gr. bullets , or lighter . Your rifle seems to be doing okay at low velocity , out to 200 yards . When you add the velocity required for long range , with the heavy bullet , I think you are going to find your rifle , wanting !
 
The problem with Sierra's manual is that it listed safe charges for the 175 gr mk with those of heavier bullets. Sierra's "max charge" for that load is certainly not the max safe charge.

You need to add several grains if you want better velocity. You will find an accuracy sweet spot as you go higher as well. And yes, seat it deeper.
 
@oneoldsap: I did too once I researched. I tried 168s (terrible), 155s (okay except for Palmas), and 150s (also okay) but the best accuracy I got was with the heavier 175s and 178s (A-max). It is a varmint barrel after all, so maybe down to the ultra-lights? 135s and 110s?

@allaroundhunter: deeper into the case or deeper into the lands?
 
nik f. said:
@oneoldsap: I did too once I researched. I tried 168s (terrible), 155s (okay except for Palmas), and 150s (also okay) but the best accuracy I got was with the heavier 175s and 178s (A-max). It is a varmint barrel after all, so maybe down to the ultra-lights? 135s and 110s?

@allaroundhunter: deeper into the case or deeper into the lands?
Click to expand...

Deeper into the lands. The Sierra's like to be set closer into the lands in my experience.
 
reynolds357 said:
I dont think Remington's chamber is "lawyered up." I think Remington realizes that those shooting .308 are shooting heavier bullets now than they did 20 years ago.
Click to expand...

No experience with the OP's rifle, but I have a Remington 700 I picked up a couple of years ago that has the longest leade known to modern man. It's so long that if I try to seat a 150 grain flat-based bullet into the lands, the base of the bullet isn't even in the case. My particular rifle has a 1983 date code, and I got it at a pawn shop. Looking at the rifling, it looks to have been shot very little. Probably someone's grandpas rifle that stayed in a closet for 30 years, the old man died and his non-shooting grandkids took it to the pawn shop. The barrel is 1:10, and it shoots 168s fairly well, but there's no question about seating the bullet out to the lands. It ain't happening. That bullet is going to jump and we just have to work with that.
 
Nik f, Remington 700s are too generous, You will run out of magazine first.. I would load to max functioning magazine length.
The load that you stated 45gr Varget and a 168SMK is a common load with Winchester Brass, and very well could show pressure with your lapua brass..
I would make sure that my scales are level and calibrated.. Start 42.0 grs with the 168s and work up until you start to see pressure. This needs to be taken
To the reloading forum at this point.. But, You can do better than 2400fps even with a 20' barrel.
 
Thanks, I can try that. Anyone have a rule as to minimum bearing surface in the neck of a case? Says Nik F.
Click to expand...

I have read that one should have at least the diameter of the bullet stuffed in the case. Thus if bullet is .308" diameter, one should have at least 1/3" of bullet shank in the case. Whether that is bearing surface only, or whether that includes the boat tail, I don't know...
 
Last edited:
Loading manuals are keyed toward safety and velocity, not accuracy; there are just too many variables. I agree that the 1 in 12 twist is not a good choice for general use in a .308 for the reasons mentioned.

Jim
 
1:12 is fine.

Sierra publishes data they get.

Hodgdon publishes data they get.

Now try to figure out Federal Gold Medal Match or Black Hills Match, a 175 SMK at over 2500 fps. They aren't useing Sierra's data.

Get a box of Fed GMM. If it shoots tight in your rifle, then you can clearly up the velocity a bit.

Jimro
 
You must log in or register to reply here.
Back
Top