Rifle or scope problem?

[Dudley Do-Wrong]

I have a browning A-Bolt 300 win mag with the BOSS system. I had been shooting Remington 180 gr SP core locks. I decided to try some 150 gr SPs because I wasn't getting a good exit wound. At 50 yards, I had a good 1 in group slightly right of center target, I figured that was good enought to sight in at 100 yards, At 100 yards I was all over the place (using a good gun rest). I thought that maybe the barrel was hot so I let it cool for about 15 minutes and it was still all over the place. My scope is a Bousch and Lomb 4X16X40. I finally got 3 shots within an inch or so of center target and that was after a box and a half of shells. Any of you gun experts have any ideas?

 

[Hammack]

Check ALL mounts and ring and actions screws for tightness. It could be that the rifle just doesn't like that load. Have you shot another brand of ammo in the 150gr? Does it go back to shooting tight with the 180gr?

 

[Eddy M.]

considering the gun scope ,ect as said above something sounds like it is loose

 

[killitgrillit]

If it was the gun or scope why did it finally settle down after a box and a half of shells put thru it?????????
just wondering myself

 

[Doc_Holliday23]

hard kicking rifle could've caused the variation. perhaps the scope finally settled into the rings. I'd go shoot it some more with a cold barrel, at least 3 more times in a row to make sure its still zeroed the same. Make sure all bases and ring screws are as tight as they can be.

 

[Lead Poison]

I don't think you have a problem with the rifle or scope.

First, you're not going to get better penetration by going to the lighter 150 grain bullets! A heavier bullet of the same design will always penetrate better than a lighter bullet.

Second, Browning rifles equipped with the BOSS can be finicky if the BOSS setting isn't right for each specific bullet.

On the other hand, when adjusted correctly, most Browning BOSS rifles are usually VERY accurate once you find the right setting!

I suggest you stay with the heavier bullet, but go to a tougher bullet like Nosler Partitions or Barnes Triple Shocks. Then adjust your BOSS with them at the range. This should solve your problem.

 

[NOYDB]

You don't mention if you adjusted the BOSS settings. If you haven't fooled with it much be aware that in a cool barrel the difference at 100yds can be groups as large as a softball when it's off to overprinting or thru the same hole when it's adjusted FOR THAT SHELL (from that mfc). Keep in mind that even using the same grain bullets you may still see a difference with different brands.

Also keep in mind when tuning a BOSS that each time you change the setting, you change the point of impact. DO NOT ADJUST your scope. Adjust the BOSS until you get the tightest group, then after you lock down the BOSS setting, adjust your scope to the group.

If you have a quality rest and you're sure of your hold, fire three, let cool, then adjust. When you get in the neighborhood of the sweet spot, start using five shot groups before making additional adjustments.

One other tip, check the action screw at the rear of the trigger guard. For some reason on A-bolts that screw has a tendency to loosen and will affect grouping.

The chart on the Browning web site will give you a starting point for your BOSS setting, but remember that's just a general guide and may not be even close for your barrel and that mfc shell.

The first time setting up for a cartridge I plan on having at least four boxes on hand and to spend 3-4 hours (allowing for barrel cooling). But once it's on, it's totally repeatable, you can switch from one cartridge to another and back as long as you keep track of the settings. You still have to adjust and verify your scope as the point of impact will change. But anytime you make a change on your gun that should be done anyways.

 

[stev]

yup that boss is a bugger to adjust.Once its adjusted to your bullett its killer.Sounds like a mount issue.Id take her down and re do the whole shootin bang over again.Use lock tite on the screws.I find them bigger cal need to be lock tited on all screws.

 

[killitgrillit]

I don't think it's a scope or mount problem, it was shooting fine with 180gr bullets correct.

 

[Dudley Do-Wrong]

The gun has been inconsistent, even with the 180 gr, I thought it was just me doing something wrong. I’ve taken a lot of deer with various guns so it’s not like I’ve never done this before. When I sighted in at the beginning of this year, it was a little off at 100 yds. After about 5 or 6 shots, I had a 1 inch group just on the edge of center target. Good enough I thought. I shot one doe at 175 yds broad side, perfect heart shot. A week or 2 later, I missed another doe at about 100 yds, and then just a few weeks ago but I killed a wild dog chasing deer at 125 yds (dog was headed straight at me). Then I missed a real nice 8 pt at 100 yds. Now, reading the BOSS specifications (on Browning web page) it looks like I have set it incorrectly. When I bought the gun they told me that it should be set at “0” for 180 gr bullets. The chart says it should be set at 4, big difference.

 

[Lead Poison]

The gun has been inconsistent, even with the 180 gr, I thought it was just me doing something wrong. I’ve taken a lot of deer with various guns so it’s not like I’ve never done this before. When I sighted in at the beginning of this year, it was a little off at 100 yds. After about 5 or 6 shots, I had a 1 inch group just on the edge of center target. Good enough I thought. I shot one doe at 175 yds broad side, perfect heart shot. A week or 2 later, I missed another doe at about 100 yds, and then just a few weeks ago but I killed a wild dog chasing deer at 125 yds (dog was headed straight at me). Then I missed a real nice 8 pt at 100 yds. Now, reading the BOSS specifications (on Browning web page) it looks like I have set it incorrectly. When I bought the gun they told me that it should be set at “0” for 180 gr bullets. The chart says it should be set at 4, big difference.

I didn't realize the rifle was not shooting the 180 well any longer. If that is true, you could have a bedding screw that has loosened, loose scope mount, or a bad scope. I still don't believe there is a major problem with the rifle other than these.

Also, don't take Browning's "sweet spot" recommendation as gospel; they're a starting point only. Very often, the real "sweet spot" for individual rifles is different. The only way to find it is to shoot, shoot, shoot your rifle.

 

[Darkhorse]

Forget what the chart says. Those are only suggested starting points. The only way to find the absolutely best spot is lots and lots of shooting. On top of that my Abolt didn't really settle down until after 100 rounds had been shot through it.
In the end it took me 2 years to find the best setting. The first year I hunted with the gun I was getting sub 1 inch groups. After working with it during the off season I now get sub 1/2 groups off the bench at 100 yards.
The first 3 shots are practically in the same hole, then if you don't allow the barrel to cool the shots start to string to the left. A .300 Win. heats the barrel up fast.
My best groups measured center to center with dial calipers were under .200, the rifle shoots better than I can see with a 3.5 X 10 Leupold.
These were not factory loads. All testing was done with a prepared box of cases. Neck sized, neck turned, weighed, primer flash hole chamfered inside and out, and the bullets were seated with an inline seater.

 

[dixie]

David, I had a problem similar to yours a few years ago, turned out that the screw in the forearm was loose, I'd start there.

 

[Jack Flynn]

Cut the boss off and have it recrowned. Saves your ears and will shoot just fine I'm sure. BTW I've got some 300 mag ammo if you would like to try it. Several boxes to be exact. Anybody live close to Augusta that will be heading Davids way in the next couple of weeks. Gotta get the man some ammo to try......PM me or him if you like.....As a matter of fact it's 3 boxes of Hornady and Winchester 300 mag ammo.

 

[Lead Poison]

Cut the boss off and have it recrowned. Saves your ears and will shoot just fine I'm sure. BTW I've got some 300 mag ammo if you would like to try it. Several boxes to be exact. Anybody live close to Augusta that will be heading Davids way in the next couple of weeks. Gotta get the man some ammo to try......PM me or him if you like.....As a matter of fact it's 3 boxes of Hornady and Winchester 300 mag ammo.

Get the BOSS CR (conventional recoil). It doesn't have the awful noise caused from the ported BOSS, but is still adjustable for obtaining excellent groups.

 

[Dudley Do-Wrong]

I appreciate it Jack

 

[Darkhorse]

I agree with Jack. Cut that noisy BOSS off and send it to me and I'll dispose of it properly. Got a rifle here that's just begging for one.

 

[killerv]

It could be a number of factors, how many shots do you shoot before you let your gun rest? How long to you let it cool down, is your scope in a bind, bases loose, how often do you clean your barrell (how many shots before cleaning). Corelocks aren't know to be the most accurate rounds out there. An exit would isn't necessarily want you want out of a round in my opinion. I like for my bullets to be sticking right under the skin on the opposite side, this means the animal took all of the energy from the bullet and that's devestating. Just my opinion.