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Bedding a Browning A-bolt with BOSS

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Unread 02-24-2011, 08:30 PM
Junior Member
Join Date: Nov 2010
Posts: 15
Re: Bedding a Browning A-bolt with BOSS

Shot some more on Monday with a tripod to make sure the lead sled I was using wasn't impacting my shooting. Same results as before, excellent vertical spread at around 0.5" and horrible horizontal spread at 1-2". I'm going to buy a Sightron SIII 6-24 scope but I'm waiting for their new reticle to become available. Which isn't for another month. So I'll have to wait until then to replace my scope to see if their is a problem with it.
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Unread 02-24-2011, 09:17 PM
Platinum Member
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: Bedding a Browning A-bolt with BOSS

Have you already done a complete load workup from scratch on this rifle? e.g. ladder test from min to max load at .5 grain or less increments?

When I re-read your post, it sounded like you've only fired a few groups with one powder charge. Even if it was your best load before bedding, you may well have changed the harmonics of your rifle.

I also recall reading an article once that described a situation/technique whereby you could hone in on an accuracy node by manipulating seating depth/jump to the lands ever so slightly and that moving in or out would change the group formation from horizontal to vertical and at some point in between you would get your tightest group.

I've never exactly reproduced that (perhaps not thorough enough), but I've seen something similar.

Good luck.
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Unread 02-25-2011, 12:15 AM
Junior Member
Join Date: Nov 2010
Posts: 15
Re: Bedding a Browning A-bolt with BOSS

Supposedly the point of having a Browning with a BOSS is to eliminate the need for ladder testing with different charges. You can adjust the BOSS to match the harmonics instead. I have adjusted the BOSS and it does impact the vertical spread but hasn't improved the horizontal. However maybe I'll change my load up as you suggest and see what happens.

I plan on purchasing a headspace bump gage and a Hornady overall length gage to set the bullet depth more accurately. There are so many things to adjust when reloading and shooting long range. I'm trying to systematically eliminate each one. It just baffles me why harmonics and reloading techniques, etc would only improve the vertical spread but not horizontal spread. It seems both would be impacted by adjusting these factors. That is why I suspect my scope. It is a used Pentax lightseeker and I don't have a long history with it. I'll keep working at it and let you know if a new scope helps once Sightron starts shipping their new scope.
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Unread 02-25-2011, 12:42 AM
Platinum Member
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: Bedding a Browning A-bolt with BOSS

Sure... scope, bases, action screws, anything touching the barrel...

...and load workup with seating depth being one of several key variables.

BOSS sounds good on paper. I've just never spent enough time with it to convince myself that it works although I see a lot of testimonials.

Let us know what you find.

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Unread 05-30-2011, 07:37 PM
Bronze Member
Join Date: Aug 2009
Location: Chuckey TN
Posts: 98
Re: Bedding a Browning A-bolt with BOSS

Any luck on the load development?

Also, would you care to post a picture of your bedding job? I'm wanting to bed my A-Bolt as well and wanted to see an example before I tore into it. Did you remove the trigger to do it?

I sure hope this thread isn't too old...
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Unread 06-01-2011, 08:53 AM
Silver Member
Join Date: May 2003
Location: The Big Country
Posts: 250
Re: Bedding a Browning A-bolt with BOSS

A good bedding job can't hurt, but if you are not methodically adjusting the BOSS to find the best setting for your load, you might as well have it cut off.

They do work as advertised, but every time you change the load, you may have to find the optimum setting again.

I would recommend that you work up a load to the velocity/SD you want with the BOSS set in the factory recommended sweet spot, then start adjusting the BOSS WITH NO CHANGE TO THE LOAD, perhaps in increments of five or 10 at a time on the graduated scale:

Fire a group and let the barrel cool.
Adjust the BOSS 5 on the scale.
Fire a group. If the group is better, adjust five more in the same direction and fire another group. Continue doing this until the group starts to open again and then back up to the adjustment that gave you the smallest group.

If after your 1st adjustment your groups are worse, make an adjustment in the opposite direction and proceed with the above method.

Most people that say the BOSS doesn't work for them have not tried graduated methodical adjustment or they keep changing loads, which changes the barrel harmonics and necessitates adjusting the BOSS again.

The devices do work, but you need to stay with the same load, be methodical exercise some patience until you start seeing a change in groups.

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Unread 07-18-2011, 11:04 PM
Silver Member
Join Date: Jan 2002
Location: Okotoks, Alberta
Posts: 134
Re: Bedding a Browning A-bolt with BOSS

I've put hundreds of round through a BOSS equiped Stainless Stalker trying to find the optimum method for tuning these beauties.

The best method I've found so far is to:
  1. Set the BOSS to a recommended setting, or one that is close according to the manual. Approximate if you have to.
  2. Stay with the factory COL, I've tried different lengths but ended up chasing my tail by changing the COL, then ending up messing it up by following that change with a tweak to the BOSS.
  3. Follow any ladder style load development method to determine that point of powder charge insensitivity where if you vary the powder charge by (e.g.) 0.2 grains the center of a group doesn't change.
  4. Adjust the BOSS to tighten up the groups. This takes the place of varying the bullet depth step which would normally follow on a non-BOSS equiped rifle. This is fine work. If you change the setting any more than 2 increments per group you risk jumping over a good group. Also tracking your groups in a log book really helps.
When you run your test groups ALWAYS allow cooling time between each shot. I've found that by the time the 3rd shot is taken, the barrel has heated up and walks off-target - took me many range trips to figure that one out. But it makes sense as these are hunting rifles first, designed for a limited number of shots in a string before things change. That's a desgin trade-off, rapid fire accuracy vs weight.

Lastly, the stocks are so soft that they CANNOT be muscled into position on a bi-pod - this will cause horizontal stringing. Allow the rifle to naturally find the target and use a light grip.

338 Edge

Last edited by Jay Kyle; 07-18-2011 at 11:07 PM.
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