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Posted: 12/3/2012 7:26:49 PM EDT
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Remington 700 SPS varmint 308 Win
New rifle... I've only ran 34 rounds down the bore, and have been having a helluva time getting it to group. I measured the throat with an OAL gauge/comparator, and it's crazy deep. With 155gr SMKs seated to max length I've got .233 bullet jump (?). 168 SMKs net 'only' .150 jump. WTF? Is this typical of Remington barrels? |
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With 155gr SMKs seated to max length I've got .233 bullet jump (?). 168 SMKs net 'only' .150 jump. WTF? Is this typical of Remington barrels?
What do you mean by "Max Length"? SAAMI max or max to fit your mag. If SAAMI or book max, ignore it as it means nothing to you and your rifle. Seat longer if your mag will allow. If mag length, then that's the jump you are stuck with and, yes, long throats are common in stock production rifles. Keeps the pressures down on SAAMI spec ammo. A long jump can be just as accurate as short jump, Think Weatherby , 5.56, 6.8SPC etc. Here is a study done by Barnes. Note, more than one OAL sweet spot. One out long with little jump and another short with a lot of jump. Scroll down to "from the lab". http://www.barnesbullets.com/resources/newsletters/september-2007-barnes-bullet-n/ |
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Weatherby magnums have long jump to keep peek pressure under control. This does not include Weatherby rifles that are chambered in "standard" calibers such as 7mm Remington Magnum. They may still have the long jump but it's not necessary for pressure control.
As the others have stated, you can seat your bullets out more if your magazine is not a limiting factor but also as they stated you should be able to get decent accuracy even with the jump. I have 2 Fin model 39 Mosin Nagants. It is impossible to seat the bullets far enough out to limit jump. These milsurp rifles are well known for having very deep throats. However both of these 1940's made rifles will shoot close to MOA with my hand loads. You need to measure your rifle for ZERO jump then work backwards from there. |
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Illustrative comparison of zero (to lands) and max length (magazine). .125 jump as measured with comparator
http://i1341.photobucket.com/albums/o756/todd_adams1/DSCF2834.jpg |
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Quoted:
Have you checked the crown. Most of the ones I've seen from the factory leave a LOT to be desired. If it doesn't leave the barrel cleanly and consistantly then most anything you do at the other end is for naught. YMMV Good point on the crown. Here is a good crown pattern on a custom match .308 rifle. 
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Not only check the crown, but check in the bore down to about an inch.
Rem had a problem a few years ago of not having the pilot on the crown tool perfectly aligned with the bore. I had 3 Rems that had a problem at the crown, one land was wiped away, and down about 3/4 an inch, on the oppisite land had a gouge across it. I ended up cutting an inch from the muzzle and recrowning. You can check deeper with a piece of cotton pushed down the bore about an inch and shining a bright light on it, I use a 10X loupe to see better. |
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It is typical for recent production Remingtons to have very long throats, as stated it helps keep pressure down, which helps prevent catastrophic failures, which helps to prevent liability.
I don't know what I'm giving up not loading anywhere near the lands, but at mag length with Hornady 155 & 168 Amaxs, 178 BTHPs, SMK 155 Palmas, and Nosler CC 168s factory ammo and/or developed loads I have found consistently MOA or less (some significantly) loads with each. 168SMK in FGMM and handloaded just never came together for some reason, not bad, just not as good. My results do not seem a-typical but there's always a chance you got a lemon, but before throwing in the towel, try some different loads/bullets, I suspect you'll find something. Also though you have probably checked always a good idea to inspect base, rings, and scope when a rifle isn't performing. And if its in the factory stock try to keep the pressure back towards the action, that thing flexes like crazy. Good luck |
On some Round Nose Corelok bullets the ogive extends farther out. Much farther than Pointed Soft points or Match ammo. Thus the reason for the extended factory throat. You can eather load your match ammo longer to touch the rifling and fire single shot or you can load up a bunch of Round Nose Corelok bullets to fit your magazine and touch rifling. You will be surprised at how well the ugly Round Nose Coreloks shoot. I like the 180 grain versions
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Quoted:
Illustrative comparison of zero (to lands) and max length (magazine). .125 jump as measured with comparator http://i1341.photobucket.com/albums/o756/todd_adams1/DSCF2834.jpg Well, there ya go. Use the Max length that fits in the mag and work up an accurate load with different powders, bullets, primers, reduced OAL and charge weights. IMO, OAL/COAL is far down the list as far as what affect accuracy. |
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