WSM and 20" barrels?

[300sendero]

My 20" proof shoots 215 Bergers at 2650 with H1000. Handy little bugger to pack around.

 

[rustyshackleford]

Look up the studies done by ballistician Homer Powley

Your statement reads as if you'll get full velocity and no flash from a 4-6" barrel with a WSM. We all know that ain't the case. Even going from 18-22" you'll probably pick up probably 250 ft/sec.

 

[7.62 Gunner]

Your statement reads as if you'll get full velocity and no flash from a 4-6" barrel with a WSM. We all know that ain't the case. Even going from 18-22" you'll probably pick up probably 250 ft/sec.

I did not say that
What I did say is that nearly 100% powder burn is completed in the first 6" of barrel according to people way smarter than me.
Muzzle flash is not unburned powder, that is also addressed in Powley's research done for the military in( I think it was 1963).

I can also tell you from first hand experience you won't lose 250 fps going from 22" to 18".
I cut 9" off my 25" saum barrel and lost 250 fps with the same load.

 

[JiminAZ]

OP, on the weight thing, I just had a Maverick 20" 6.5 PRC built for me by Alamo Precision. Sprung for the AnTi action, but stuck with a steel barrel, so kinda halfway to their Maverick light model. With a 20" barrel, carbon fiber doesn't save as much weight as guns with longer barrels. Pretty expensive upgrade to shave maybe another half pound. I also went for a little pic rail to mount a bipod.

My gun came in at 6 lb 12 oz from the builder. With a NF NX8 2.5-20, Seekins medium rings, a Thunderbeast CB brake, Dominus CB suppressor and Armageddon suppressor cover it weighs 9 lb 13 oz. That's ready to hunt, no ammo no bipod. I didn't exactly spare weight with my scope choice. Scope and rings were 2 lb 2 oz. The net of removing the thread protector, and adding brake, suppressor, and cover added 15 oz. The cover weighs 2.2 oz. so if I hunt without the cover I'll be just under 9 lb 11 oz no bipod no ammo.

 

[rustyshackleford]

I did not say that
What I did say is that nearly 100% powder burn is completed in the first 6" of barrel according to people way smarter than me.
Muzzle flash is not unburned powder, that is also addressed in Powley's research done for the military in( I think it was 1963).

I can also tell you from first hand experience you won't lose 250 fps going from 22" to 18".
I cut 9" off my 25" saum barrel and lost 250 fps with the same load.

So why aren't you just running a 6" barrel? Keeping it simple just cut 9 more inches off your barrel. It'll only cost you 250 ft/sec and you'll have 2" over what you need for full powder burn

 

[cohunt]

So why aren't you just running a 6" barrel? Keeping it simple just cut 9 more inches off your barrel. It'll only cost you 250 ft/sec and you'll have 2" over what you need for full powder burn

Wow

 

[JiminAZ]

So why aren't you just running a 6" barrel? Keeping it simple just cut 9 more inches off your barrel. It'll only cost you 250 ft/sec and you'll have 2" over what you need for full powder burn

Relationship of barrel length to velocity isn't linear. Guy is telling you what actually happened with his barrel.

As you go with a longer barrel, the net velocity gain drops off. Diminishing returns.

The powder is burned up in the first 6". The resulting gasses are still at a very high pressure and do the job of accelerating the bullet down the barrel. If the barrel is short enough, when the bullet exits, the gasses are still hot enough to incandesce, which is "flash", but NOT unburned powder finishing its burn.

Since the pressure is dropping as the bullet goes down the barrel, the velocity gain per inch is also dropping.

Guys running shorter barrels on suppressed guns have been goring some sacred cows in the past few years.

 

[ducky]

OP, on the weight thing, I just had a Maverick 20" 6.5 PRC built for me by Alamo Precision. Sprung for the AnTi action, but stuck with a steel barrel, so kinda halfway to their Maverick light model. With a 20" barrel,

Sounds like a great build. I'm not hung up on needing a CF barrel, I'd be willing to go with SS. I just kind of got spoiled carrying a M70 EW or Classic FWT in McMillan stocks and neither tipped the scale over 7.5 lbs ready to hunt. All my suppressed hunting rifles are around 10 lbs hunting weight.

 

[Jonoton]

Guys with direct experience cutting their long barrels down: how does the muzzle blast as perceived by the shooter increase?

Y'all about have me ready to chop a foot off my 7WSM (or more likely have a prefit spun up for my Origin action), but hunting with a suppressor might not happen for me.

 

[308ghost]

Guys with direct experience cutting their long barrels down: how does the muzzle blast as perceived by the shooter increase?

Y'all about have me ready to chop a foot off my 7WSM (or more likely have a prefit spun up for my Origin action), but hunting with a suppressor might not happen for me.

If you use a muzzle brake, the report from dirt and earth is very noticeable. You don't want to be shooting in sandy or dusty areas for long. If you mean muzzle flash, there's none I'm able to see during shooting light hours. It's quit a bit louder to shoot short but the handiness you gain from a 20-22" tube is incredible. In theory short barrels are also stiffer and less movement generally means more repeatability. I want to add a smaller suppressor than the one I have, and a folder. Making it oven shorter and easier to move around. I'm not certain what the ideal caliber is for a 20" barrel but I know the smaller in diameter you go. The more chopping the barrel effects you. I think Chopping 6" off a 6.5, 7mm and .30 Would show you that the 30 is less effected by that chop or loses less overall and the 6.5 being most affected. The other topic here is what the ideal powder for that length barrel? What's going to burn the best I that length. I chose RL16 because it's one of the fastest. Can't you feel the hot spot in a barrel with you hand after a few shots? Is it hot in the throat or middle? Typically it's the throat and or middle I'd think. Which would back up the argument for most powder burned in the first 4-6" of barrel. I remember this on a 7mm rem mag I loaded for. I used RL 22 and that hot part of the barrel was right on the chamber side of middle. Maybe 8" forward. I bet you could move that forward or backward with powder selections??

 

[7.62 Gunner]

Guys with direct experience cutting their long barrels down: how does the muzzle blast as perceived by the shooter increase?

Y'all about have me ready to chop a foot off my 7WSM (or more likely have a prefit spun up for my Origin action), but hunting with a suppressor might not happen for me.

I personally wouldn't go less than 22" without a suppressor, especially if you plan on using a brake

 

[rustyshackleford]

Relationship of barrel length to velocity isn't linear. Guy is telling you what actually happened with his barrel.

As you go with a longer barrel, the net velocity gain drops off. Diminishing returns.

The powder is burned up in the first 6". The resulting gasses are still at a very high pressure and do the job of accelerating the bullet down the barrel. If the barrel is short enough, when the bullet exits, the gasses are still hot enough to incandesce, which is "flash", but NOT unburned powder finishing its burn.

Since the pressure is dropping as the bullet goes down the barrel, the velocity gain per inch is also dropping.

Guys running shorter barrels on suppressed guns have been goring some sacred cows in the past few years.

I think my sarcasm has been missed. I wouldn't say anyone has been goring any sacred cows other than Sig with their 80 ksi cartridge. Longer barrels are faster than shorter barrel given equal pressure and barrel quality. MFG's have minimum barrel lengths for suppressors for a reason.

300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag?

Introduced by the Winchester Repeating Arms Company in 1963, the 300 Winchester Magnum (300 Win Mag) is based on the 375 H&H case shortened to fit a standard length action and necked down to 30…

rifleshooter.com

You may get acceptable performance from a 20" or shorter magnum but it won't be optimal. Your can may be warranted against mfg defects down to whatever barrel length but you are decreasing the longevity of it.

If you plotted the velocity by barrel length for any given cartridge it's going to follow a similar trend. To me the objective should be to never assemble a cartridge with a barrel length that puts your velocity in the steep part of the curve.

 

[JiminAZ]

Yeah hard to read sarcasm on a board.

In your plot above, if you want to get max velocity, you could extend the barrel beyond 24" and get even more. After all you still have >4500 psi at that point. Then, using a slower powder you could extract even more velocity from the even longer barrel.

We all have the point where we draw the line between utility and performance. Bench rest guys don't have to shag the beast over the mountain and through the woods, so they trend longer. I'm leaning shorter to accommodate the suppressor and still not have a long wand. It does what I need it to do. May not be the best answer for others though.

 

[JiminAZ]

Sounds like a great build. I'm not hung up on needing a CF barrel, I'd be willing to go with SS. I just kind of got spoiled carrying a M70 EW or Classic FWT in McMillan stocks and neither tipped the scale over 7.5 lbs ready to hunt. All my suppressed hunting rifles are around 10 lbs hunting weight.

Hey, buy whatever you like. My next one might have a CF barrel. Kind of mulling it over.......

The AnTi action sure gets you serious weight savings for a relatively small upcharge.