Bullet jump

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Maxwelldrake

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I have a 300 win mag. It shoots pretty good but trying to get it better. I shoot Sierra 180 gr. SBT bullets. 76 grs. H4831SC. I checked my bullet jump and it is .277". I measured my distance to the lands with a O.A.L. gauge. Came up with 3.632". I'm loading at 3.355". How can I have this much jump? Any help would be appreciated.
 
Maxwelldrake said:
I have a 300 win mag. It shoots pretty good but trying to get it better. I shoot Sierra 180 gr. SBT bullets. 76 grs. H4831SC. I checked my bullet jump and it is .277". I measured my distance to the lands with a O.A.L. gauge. Came up with 3.632". I'm loading at 3.355". How can I have this much jump? Any help would be appreciated.
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I've found that bullets like nodes. For example a particular byllet might like .020 off the lands, or .090 off the lands, or .150 off the lands, and shoot excellent at any of those seating depths, but shoot worse or even like crap somewhere in between.

Weatherby magnum cartridges (excluding the RPM's) have historically massive freebore and they typically find at least a few bullets that shoot great in them.

Jump isn't inherently a bad thing, and as long as it shoots, it shoots. You'll find that often the factory ammo in common cartridges that shoots the best is jumping 100 to 200 thousandths. It's often easier to get a load to shoot well really close to the lands, but it's far from the only place a bullet will shoot well from.

Also welcome to the forum
 
You will find that to be the case with all factory 300WM. The SAAMI reamer has about .297" of freebore and a fairly short leade after that. If my mag box is long enough I load out to the lands and shoot, shortening until I find a seating depth that shoots well. I also gain a lot of powder capacity with heavy bullets by using 3.600 actions and mag boxes. Your Sierra isn't a very long bullet, if your magazine isn't 3.600" long just start your seating depth test at magazine length -.030" and shorten from there in .010" increments until you see an area that shoots better and then starts opening up groups again, you can do finer adjustments in the range that shoots well to find your rifles specific seating depth that it likes.
 
I have several other rifles that I've never had an issue with. This one, the lands are so far out the bullet is no longer in the brass when it touches them..
Thanks for the info. I appreciate it.
 
Agree with the others, there isn't anything noteworthy about a factory chamber for a 300 Win Mag having a generous jump.

There were many historical reasons for it given, most of which were... to insure that the peak pressure wasn't going to exceed the limits.

It doesn't mean the old factory rigs won't shoot well, but yes it means you would not be seating out near the lands.
 
Maxwelldrake said:
I checked my bullet jump and it is .277". I measured my distance to the lands with a O.A.L. gauge. Came up with 3.632". I'm loading at 3.355". How can I have this much jump? Any help would be appreciated.
Click to expand...
I do not want to misconstrue your issue; are you saying 3.355" COAL is the max clearance for your rifle magazine/mag well, which allows you to load? I have three .300 WMs, all factory, that I load .020" off the lands from 190 to 215 - two of them are in the 3.55" COAL range. The other is 3.66" COAL, and all of them fit in the magazine/mag well.

 
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I might be able to load a few thousandths longer and still fit the mag., but I don't have much bullet left in the brass and I'm still .277" away from the lands
 
My 300WM's load at 3.500-3.600" also with bullets long enough to keep some in the case, short bullets I seat with a diameter in the neck and go. Usually shoot good to great. Luckily I new about the chamber before buying a 300 and knew not to get one with a short mag box. That said, I've seen some 300's shoot really well at book lengths from the short mag box. I don't recall one that shot terribly that didn't have other issues.
 
I have a Barrett MRAD (MK-22), Nightforce ATAC-R, 7-35 with Tremor 3 reticle and I load primarily the 220 grain Sierras for it. It likes the bullet COAL 3.450. I got 2,105 rounds through it.
Win brass
73.5 grains of H1000
72.5 grains Ramshot Grand

Hornady Brass / 220 Gr ELD
74.5 grains H1000

With the 180's, they are short for the .300 Win Mag, thus finding the lands might be tough. I tried it with some small packs and didn't like them. I'm usually shooting 1,100 to a mile with my Win Mag

I tried 230 ATips this weekend and they shot well. COAL 3.55 70.2 GR of H4831SC
to 1,100 yards 9 out of 10 hits in 8-10 mph winds at 5,087 ft elevation
 

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