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.308 winchester VS 7MM-08

jplookster
I find myself with a extra ar-10 upper that does not shoot as accurately as I demand. Thinking of haveing it rebarreled but thought it would be nice to do it in 7mm-308. A little less recoil will be a plus as well as a little better velocity.

Is the 7mm-308 capable of as good accuracy as the .308 Winchester??

TIA
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Comments

12 comments

Date Votes
  • quickmajik
    many seem to think, and have proved that the 7mm-08 can be an all around better round then the .308 in about everyway.. the improvements you'd have if you dont reload would probably be minimal when it comes to small groups because there are far more factory loads custom tailored for accuracy in .308win. then there are for the7mm-08.

    Thats just my two cents.
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  • ern98
    7mm-08 is a fine cartridge and would be a great choice. Another thought, how about 260Rem? 6.5cal has some really fine bullets available for longer range accuracy shooting.....
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  • sandwarrior
    jplookster,

    It's a trade-off for which round is better. The 7mm-08 has a better BC for weight than does the .308. Same with the .260. The .260 and 7mm-08 have better bullets for long range shooting.

    All that said, there isn't a whole lot of difference in trajectory between the .308 and 7mm-08 and .260 Rem out to 300 yds. in like sized bullets. It's when you go beyond 300 yds that the higher BC bullets of the 7mm and 6.5mm really start to shine. So you're not really gaining anything if you don't shoot beyond 300 yds. All the cartridges/calibers mentioned have a lot of very accurate bullets to shoot. And it's true that there is slightly less recoil in the 7mm. Same with the .260.

    FWIW, I personally favor the 7mm over the .308. Same with the .260. But unless you shoot long range it isn't going to matter a whole bunch if you get the new barrel or stay with the old barrel.
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  • jplookster
    Thank you all!

    This was some very good stuff.
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  • nononsense
    jplookster,

    "I find myself with a extra ar-10 upper that does not shoot as accurately as I demand."

    Your statement doesn't really give us any information to work with since there are a bunch of factors that can contribute to lesser accuracy. Simply re-barreling might not solve the problem because of problems that don't involve just the barrel. Personally, I'd pack it off to a top AR gunsmith and have them do an assessment. You will need to give them detailed information about how you use this upper. Yes, they will charge you for this service but it might save you from the much larger cost of re-barreling without gaining any accuracy.

    The .308 Win. has demonstrated the potential of being a top accuracy achiever in competition and the hunting field. Inaccuracy stems from all of the other variables that get thrown into the mix, not just from the cartridge selected. The .30 caliber component selection for accuracy in hunting and target shooting is huge because there has been so much effort put into it from the demand by shooters and competitors.

    If this is a matter of wanting something different then by all means pick a new cartridge. But pay attention to who you get to have do the work and to the selection of the barrel itself. A great barrel put on by an amateur can suffer. Conversely, the best efforts by a great gunsmith will be limited by poor quality barrels.

    Best.
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  • tsr1965
    You might want to go back and do a search in the forums for AR-10's and DPMS LR-308. There are as nononsense describes. several factors that contribute to accuracy or in accuracy. Two of which are trigger pull, and twist rate of your barrel, and was your barrel properly broken in, and has it been cleaned since?

    I know that my DPMS LR-308, likes its 178/180 grain bullets better than the 150, and 165/168 grain bullets. It has a 1 in 10 twist rate. It should be a 1 in 11 or 12 for better results with the 150's. I also did install a Jard trigger in mine, as I plan on using it for just target shooting, and hunting from an elevated, inclosed blind.

    Best
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  • jplookster
    Very good points.

    I strongly suspect that the issue with this barrel is incorrect headspace as it was purchased used without a bolt carrier assembly. I purchased a new one for it and it shoots very poorly at 3 inchs at 50 meters with the new bolt. When I swap to another bolt assembly I have it will shoot at 2 inchs at 100 meters(This bolt is already dedicated to a 1/2 inch rifle).
    I think on match uppers the bolt is used during the headspaceing process to set the barrel extension and then the gasport hole is drilled. I think it doubtfull that any smith that does not have access to many many bolts will be able to correct a headspace issue on this upper/barrel. That probably leaves Armalite and I'm not sure they have time or inclination. Its a shame too cause this is a Lothar Walther barrel.

    The barrel manufacturer I have selected to rebarrel the upper requires the bolt that will be used with the barrel so that it can be headspaced properly before drilling the gas port. So I can use the new bolt I have now and should get correct headspace. Kreiger should be able to do it right. As long as I'm there I thought I'd try a diff caliber in this platform.
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  • nononsense
    jplookster,

    All valid observations.

    If you have any interest in using that LW barrel you could call:

    John Holliger at http://www.whiteoakprecision.com/index.htm

    Or

    Derrick and Marty at http://accuracyspeaks.com/public_html/index.html

    They might be able to shine some light on the diagnosis for your upper.

    John Krieger makes exceptional cut-rifled barrels and he stands by his products. Nice person also.

    Best.
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  • jplookster
    My other brief thought was just sell it on gunbroker as is and plead ignorance. An identical upper and carrier to mine just went for $1510 last week.

    But then I would not sleep well.
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  • sandwarrior
    jplookster,

    I did need to mention in my first post that you need to find the accuracy problem. But, I didn't so I will now.

    The headspace problem would be indicated on the ejected cases. You could also call the people that nn mentioned. They would probably be able to straighten out a headspace problem for about 1/3 of the cost of an entire new barrel and fitting. More to the point hopefully, they can find where the inaccuracy is coming from. That probably won't cost a third of what re-headspacing might cost.

    Bottom line on this is don't just rebarrel to a 7mm-08 or .260 thinking that alone will solve the problem. If you solve the accuracy problem along with re-barreling to one of those calibers because you wanted to then that's a good deal.

    (edit:)

    Also, Armalite is VERY inclined to do the work for you. I had a good talk with one of their better gunsmiths regarding my AR30. The talk was productive and a timeline was given as to when it could be done. That was before the election though, so honestly, they are like most in that they are backed up a ways.

    -good luck to you.
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  • jplookster
    What would I look for in an used case that will indicate improper headspace??
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  • tsr1965
    jplookster,

    You would look for more head expansion and a brite ring by the webof the case head, and backed out primer, that is either flattened or cratered. With that case moving during lift off, that would cause the problem also.
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