Raptor 1

Recently purchased a Pro hunter frame, and now in the market for a barrel. I'm planner to purchase my first rifle barrel im 7mm-08. My question, what kind of velocity increase should I experience with the Pro Hunter 28 inch barrel? Most factory published velocities with a 140 grain bullet are around 2860 fps with a 24 inch barrel. Just courious what 4 more inches of barrel will produce. Any insite on this would be apprieciated...

R1

ranger140892

You might find that it actually slows it down a bit. I was shocked when I built a 260 Rem and kept the barrel at 27". All my loads chrono'd over 150 fps slower than they should have. Later my wife wanted the barrel cut down so I cut and crowned it to 24". Now the velocity is up to normal.

Same thing happened when I built a 280 Rem and left the barrel at 26". I suspected it was that the publishedloads were worked up in 24" barrels and chamber pressure was dropping off before the bullet left the longer barrel. I contacted a couple of powder manufacturers and they concurred.

Instead of shortening that barrel, this timeI took Alliant's advice &experimented with powders that were slower than published powders. IMR 7828 and RL 25are working well with 120 & 140 gr bullets in that gun, with velocities a little faster than a normal 24" in that cartridge.
good luck

Soilarch

Well people either love or hate Chuck Hawks but read this:
http://www.chuckhawks.com/rifle_barrel.htm

Towards the end he takes agreeing estimations from both the Remington and Lyman's publications. The way I see things you can hope for 25fps per inch from this data. The 2500-300fps class is agreed upon as a 20fps loss or gain per inch. You are a little past the 2750 average so that goes in your favor. This is with 22-26 inch barrel being considered. But there's a point of diminishing returns somewhere in there so an honest guess would put you back at 20fps per inch.

This is all just theory though. Different cartridges behave differently, different powders behave differently, and some barrels are just faster or slower than others. Even if you reload you will only have control over one of these variables.

Is an extra 4" of snag and muzzle heavy weight worth an extra 3.5% velocity?

SwampCollie

Its the law of deminishing returns.

Each caliber has a "sweet spot" regarding the barrel length to max velocity ratio. After that sweet spot is passed in length, you are mearly adding friction caused by the bullet contacting the barrel, in turn slowing the bullet. Moreover, shorter barrels are typically more accurate. Think about a section of 1/2" PVC 10' long as compared to one half that....the shorter one is more rigid...less oscillation during firing. But, you don't want to get too short...or you start sacrificing speed again....its all about balance.

For a 7-08 (great choice by the way), I wouldn't want anything longer than a 24", but a 20" or a 22" is more like it.

Chris W.

With Standard calibers, I don't believe you'll see much improvement over a 26". Now,if it was amagnum or the Ultramagnum caliber, you'd probably see more of a velocity improvement.

cherokee_outfitters

1. 28" barrel will not slow down a 7mm-08, unless you have the load reduced to the point its half of what it should be. On that particular load you will gain 20 to 30 fps per inch of barrel gained.

2. In total reverse a 28" barrel is the one to watch for gaining too much pressure and velocity for the action to handle it. I had a browning 1885 with a 28" barrel that couldn't handle my loads that my ruger no.1 would shoot just fine in the 26" barrel.

3. Same goes for revolvers vs. contenters or levers gun with pistol cartridges. They hold 1/4 the powder that your 7mm-08 does and they gain an amazing amout of fps in longer barreled guns without hitting a dead space up to 28-30 barrels. You can take a pistol round and stick it in a lever gun and make it act like a 30-30 as far as ft lbs go.

4. Longer barrels hold the advantage to gaining fps without having a maximum charge of powder behind it. Barrel length will make the equivalent of shooting premium loads without the wear on the rifle and the price of purchasing premium cartridges if your not a hand loader.

Something might have been wrong with your last 2-4 inches of barrel but that's unlikely. A 26" barrel is just about perfect length for gaining that extra fps without the damaging pressure behind it. That is the reason for most of the manufactor's to start putting them back on their hunting rifles. For awhile only a few had them on their rifles. Short barrels are very nice to carry in the field but they lose when it comes to long range fps and ft lbs.

Rebel Hog

7mm-08

Ruger> 16.5"

Remington> 24"

Savage> 20"

eldeguello

As a guide only, you can figure 25 FPS/inch for standard (non-magnum) cartridges. That is, if you cut off 1", you'll lose 25 FPS; add an inch, you'll gain 25 FPS.

However, as Ranger140892 says, it doesn't always work out that way. Whether you lose or gain depends on a lot of factors, one being the case capacity, and another being the burning rate of the propellant used.

For example, generally,a .22 LR HV round attains its highest velocity in 18" of barrel, and anything beyond that slows the bullet down due to barrel friction. This is any extreme example, but illustrates that the same effect will occur eventually with ANY cartridge, if the barrel is long enough. So the question is, "How long does this barrel have to be before it begins to retard the velocity of the bullet?"

The answer, unfortunately, for any particular cartridge and load, can only be determined by shooting trials starting witha very long barrel, from which 1" would be cut after every five shots is fired over the chronograph screens, or some such procedure, (since it is difficult to lengthen the barrel after each series of shots.) You can't "cut it off a little longer".

Soilarch

How does an increase in barrel length increase chamber pressure? I was under the impression that the pressure "spike" occured long before the bullet had travelled 20+ inches. If that's correct...I don't get it.