The BOSS and Velocity

[EchoM70]

I've been toying around with a new rifle recently... A Browning A-bolt II 30-06
w/ BOSS. I noticed tonight that the barrel was only 22'' measured from
chamber to end of BOSS. Where the muzzle brake ports start is around 20''. I looked up the specs on this model and it's supposedly a 22" barrel, so I'm guessing they're measuring to the tip of the BOSS?

Anyways, my question is does the BOSS affect muzzle velocity? Seeing as it is ported at around 20" does that mean velocity would be equal to a 30-06 with 20" barrel? Furthermore If I install the conventional recoil BOSS (non-ported) would performance increase to that of a full 22" barrel? I've tried looking around the web for these answers but came up empty. As always any and all input is appreciated, Thanks.

 

[Ridgerunner665]

I don't know anything about the BOSS...but I thought I'd mention that barrels are measured from the end of the threads that screw into the receiver...meaning the barrel is about an inch or so longer than a measurement from the receiver up will tell you. I'd say the length of the threads varies some depending on manufacturer.

You may have known that already...but I couldn't really tell from your post and was just offering it for the sake of useful knowledge (I don't have much of that to offer...so I try to use it at every opportunity, LOL)

 

[jogar80]

You usually get a very small increase in velocity when you add a brake to the barrel (Assuming you dont cut the barrel down at all, of course). Your velocities are probably better than a typical 20", but less than a 22". Call it a 21" and be happy, lol.... it's only about 40fps difference anyway

 

[TaxPhd]

Why would a brake increase the velocity?

 

[rcmodel]

Barrel length is measured from the end of the rifling at the muzzle crown to the breach face of the bolt.

Stick a cleaning rod down the barrel without the boss on it and measure it.

A Boss with holes, or a Boss without the holes will not add velocity, because the inside bore of it is over bullet dia and the bullet never touches it after it leaves the muzzle crown at the end of the rifling.

With no bore pressure behind the bullet after it leaves the crown, velocity cannot increase.

rc

 

[jogar80]

With no bore pressure behind the bullet after it leaves the crown, velocity cannot increase.

rc

Gotta disagree with you on this one RC. I know what you mean, but the gas still has to expand beyond the Brake before it completely equalizes. I only offer this because I a witnessed a 25 fps increase after adding a bake... same ammo, same gun. I can't explain it any other way, unless I unknowingly did something different.

 

[Ridgerunner665]

Temperature could cause a 25 fps increase...among other things...clean barrel vs. dirty, different lot of ammo or powder or bullets or primers, barrel wear....LOTS of things could explain that.

The gas still has to expand...thats true, and being "gas", it will sneak right around the bullet and go on its merry way once the bullet leaves the crown.

Most common rifle rounds still have 8,000 to 12,000 psi when the bullet exits the bore...the gas has less mass, so once it gets an opening....it will leave that bullet behind because it can accelerate faster.

 

[EchoM70]

I wasn't sure if the conventional recoil device (non-ported) would still push the bullet on out... but it makes sense seeing as the bullet has to have contact with the barrel in order to continue to build pressure.

I measured the barrel without the boss from bolt face to muzzle crown and it was 20in... that's kinda annoying considering Browning lists the barrel length as 22in.

 

[Robert101]

I'm not disagreeing with any scientific data, but it seems that a 25 fps increase may not be an increase at all. Items that come to mind are: 1) load differential, 2) heat (maybe they got hotter) on rounds, 3) barrel use due to prior shooting, 4) variance in bullet diameter, 5) variance in chronograph readings from barametric pressure and temperature. I'm only guessing.

 

[Maverick223]

Anyways, my question is does the BOSS affect muzzle velocity? Seeing as it is ported at around 20" does that mean velocity would be equal to a 30-06 with 20" barrel? Furthermore If I install the conventional recoil BOSS (non-ported) would performance increase to that of a full 22" barrel?

No, at least not in any discernible way. Yes, a 20in. bbl will have the same performance with or without a muzzle device [that doesn't capture gases, AKA: a suppressor], doesn't matter if the muzzle device (be it a brake or a flash suppressor) has any holes in it or not.

That said, I would install the non-ported, BOSS-CR, version unless the recoil is a problem. You'll find that there is significantly less rear-projected blast and less perceived noise (which doesn't negate the need for hearing protection), so you might find shooting it to be a more enjoyable (I certainly do).

 

[Ridgerunner665]

I'd be sorta mad about the 22" being only 20" myself...I hate to say it, but that's a bummer.

Sent from my DROID RAZR MAXX!

 

[rcmodel]

I a witnessed a 25 fps increase after adding a bake... same ammo, same gun.

I'd say the sun got higher in the sky and the day got warmer while you were putting the brake on then.

rc

 

[EchoM70]

That said, I would install the non-ported, BOSS-CR, version unless the recoil is a problem. You'll find that there is significantly less rear-projected blast and less perceived noise (which doesn't negate the need for hearing protection), so you might find shooting it to be a more enjoyable (I certainly do).

I'll pretty much keep the BOSS-CR installed and toss the other one in a drawer and forget about it. After owning a braked rifle I said I would never own another one but I got such a deal on this one I couldn't pass it up, seeing as I could swap it out for a non-ported version it wasn't too big of an issue. It really annoys me how Browning lists the barrel as 22" instead of 20"... seems dishonest.

 

[Maverick223]

seems dishonest.

Agreed, and it makes a real difference in a .30-06Spd. The good news is Browning barrels are usually on the fast side, but I'd still want my 2in.!

 

[rcmodel]

To be fair, Browning has been known to change specs between model years on the A-Bolt and other guns.

What was made in 20" when yours was made in whatever year might now be made in 22" in 2012.

rc

 

[EchoM70]

RC, This A-bolt II was made in 2011, and purchased in early 2012. So it's a current model I can assure you, unless Browning just very recently changed specs.

Regardless I'm sure it will make a great deer rifle and I'm fretting over over nothing. Still it really bugs me why they would do that.... Why wouldn't they just make the barrel 22in and OAL 24in? It's mentioned nowhere on the site that I could find that BOSS equipped barrels are shorter to keep OAL the same.

EDIT:

After searching some more on Brownings website I found this:

Question:
On comparable models, what is the difference in the barrel length between BOSS and non-BOSS barrels?

Answer:
There is no difference in the overall barrel length. The BOSS-equipped rifle has 2" less of actual barrel length. Our testing revealed, however, that there was negligible or no velocity loss.

-------------------------

I wonder what they consider negligible velocity loss? Guess I'll have to find someone with a chrono just to see for myself.

So anyone thinking about buying a BOSS equipped Browning rifle keep in mind the actual barrel is 2" less than listed in the specs.

 

[rcmodel]

All I can suggest is to call Browning and ask them what it should be.

If its advertised as 22", and it's 20", then ask them how come it's 20".

rc

 

[Maverick223]

Our testing revealed, however, that there was negligible or no velocity loss.

Then they haven't done enough testing! This is utter BS. Don't get me wrong, I think they make a fine rifle, and I wouldn't loose any sleep over it, but that statement is just a flat out lie! Two inches can make a decent difference in velocity depending on the chambering. The .30-06Spd. isn't too bad (but far from my definition of "negligible"), but a 7mmWSM or the like will see a big hit in a 20-21in. bbl.

 

[EchoM70]

Just got out today and was able to shot some rounds through a buddy's chronograph just to see the velocity with the BOSS equipped Browning A-Bolt. To my surprise after 20 rounds my average FPS was around 2890-2900. This was 150gr Hornady SST custom. The lowest velocity was 2877 and the highest was 2909. This is right on with the velocity I would expect out of a 22" barrel.

I was told The boss equipped rifles are designed with tighter chambers, which enabled better/faster pressure build-up. Which in turn creates 22" velocity levels out of a 20" barrel. This is second hand knowledge and my buddy has been known to not know what he is talking about sometimes, so who knows.

Anyways, the numbers don't lie and I am very pleased with the results.

 

[Maverick223]

I am very pleased with the results

That's all that matters.

I may be wrong (it's been known to happen), but I seriously doubt that they cut the chambers differently for the BOSS equipped rifles. Browning's do tend to put out a bbl that is on the fast side (which may, at least in part, have to do with a tighter than average chamber), so that may be part of the origins of the legend.

 

[EchoM70]

Browning's do tend to put out a bbl that is on the fast side (which may, at least in part, have to do with a tighter than average chamber), so that may be part of the origins of the legend.

I remember you mentioning that... I need a 22" barreled A-bolt II in .30/06 as a side by side to see if they're is a noticeable velocity increase, It would be interesting to see how they compare.

I'm very pleased with the results.

That's all that matters.

Yes, it is! I was afraid for a minute there that I was going to be stuck with a long action .308.

This is actually my first Browning rifle and besides the velocity concern it's been a great rifle. Slick action... well at first it was hard to lift, but per RC's advice and a little grease it's smooth as silk. It's also scary accurate, definitely will give my Tikka a run for it's money. Overall, I'm very impressed with Browning and would definitely recommend them to someone on the fence. Now, if only it was deer season.

 

[Maverick223]

Perhaps someone will come along and let us know what theirs chronos at (unfortunately the only Browning chambered for '06 that I own is a 1895 with a 24in. bbl, so I'm of no help in that regard); of course barrels and loads (from lot to lot) will vary, but it would still be interesting to see what the results are.

 

[Silent Sam]

Much ado about nothing. No two barrels are identical. Any meaningful comparison would require a lot of barrels and loads. You can speculate what velocity would be with your barrel and load at any given length. An exercise in futility. Ballistically 50 fps doesn't make much difference in the real world and definitely falls into the "negligible" category. Accuracy and consistency are much more important.

 

[denton]

The correct definition of barrel length is from the crown to the rear face of the barrel. That is the common and clear meaning of barrel length. This is not what Browning does. They include the BOSS in the length of the barrel.

I discovered the exact same thing on a new A Bolt I bought, and Browning and I did quite a rain dance over it. Bluntly put, what they do is dishonest and misleading. According to FTC regulations, it's false advertising. I even sent them a copy of the applicable regulations, with the key portions highlighted. For a short time after, they did start noting on their web page that the advertised barrel length includes the BOSS, but that didn't last long. If they don't conceal this fact, it hurts sales.

2" less of barrel makes no difference? In a fat pig's eye! It reduces muzzle velocity and increases recoil and muzzle blast.

The box is marked 22" barrel, which is what I ordered and paid for, and not what I got.

 

[Patocazador]

To get back on the subject of a BOSS, I had a BOSS-type muzzle brake placed on my custom .338-06 Ackley Imp. Regardless of any velocity differences (who cares?), I didn't see ANY improvement in accuracy no matter where I turned the blamed thing to. Some settings produced smaller groups than others but none of the 'dialings' produced better groups than the rifle with no brake attached. I had it put on to get better harmonics in the barrel and thus produce tighter groups. This did not happen in my case.