Gunsmithing Heat/Fire Wedge

[BigDaddy0381]

Is there a difference in barrel life when using flat base bullet as to boat tail bullets? There has always been some theory that boat tail bullets burn out a barrel faster as a heat / Fire wedge happens at the base of the bullet when fired, where a flat base doesn’t have this problem.

 

[Outsydlooknin75]

Re: Heat/Fire Wedge

It only matters if you are shooting over a large body of water.

 

[svt_tactical]

Re: Heat/Fire Wedge

What about the extra wear that bullets with longer bullet surface to rifling have than those with less. for example a bullet that contacts the rifling for .5" vs a bullet that only contacts it for .4", same weight but there is more area to wear?

 

[Lindy]

Re: Heat/Fire Wedge

Unless you're shooting one of the hot magnums like the .300 WM or similar, how hot the barrel gets during extended strings of rapid fire will have a lot more effect on barrel life than bullet type.

Given that a .308 barrel may go 10,000 rounds before accuracy significantly degrades, the cost of replacing a barrel is completely dwarfed by the cost of the ammo to get it to the point of replacement, even if you reload.

 

[8shots]

Re: Heat/Fire Wedge

BD, that explains a lot. I inherited a 300 H&H from my dad, accurate as anything. Maybe he had pushed about 5000 rounds of flat based bullets through it. I loaded some boat tails, and it was'nt 100 rounds and the barrel was cooked. I had to replace the barrel.

 

[LRI]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Unless you're shooting one of the hot magnums like the .300 WM or similar, how hot the barrel gets during extended strings of rapid fire will have a lot more effect on barrel life than bullet type.

Given that a .308 barrel may go 10,000 rounds before accuracy significantly degrades, the cost of replacing a barrel is completely dwarfed by the cost of the ammo to get it to the point of replacement, even if you reload.
</div></div>


If your getting 10,000 rounds out of a 308 with exceptional accuracy I want your barrel maker's contact # (please!)

Most palma shooters change tubes somewhere between 2 and 3 thousand.

Anything's possible I guess but I've never seen a 308 go to 10k and retain accuracy.

 

[subgunr]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Unless you're shooting one of the hot magnums like the .300 WM or similar, how hot the barrel gets during extended strings of rapid fire will have a lot more effect on barrel life than bullet type.

Given that a .308 barrel may go 10,000 rounds before accuracy significantly degrades, the cost of replacing a barrel is completely dwarfed by the cost of the ammo to get it to the point of replacement, even if you reload.
</div></div>


If your getting 10,000 rounds out of a 308 with exceptional accuracy I want your barrel maker's contact # (please!)

Most palma shooters change tubes somewhere between 2 and 3 thousand.

Anything's possible I guess but I've never seen a 308 go to 10k and retain accuracy. </div></div>

Mesofine Barrels
1-877-DRE-AMIN

 

[John L]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 8shots</div><div class="ubbcode-body">BD, that explains a lot. I inherited a 300 H&H from my dad, accurate as anything. Maybe he had pushed about 5000 rounds of flat based bullets through it. I loaded some boat tails, and it was'nt 100 rounds and the barrel was cooked. I had to replace the barrel. </div></div>

If the barrel of your 300 H&H already had 5000 rds. down it, the 100 rounds of boatail ammo did nothing to it. It was already toast. The old wivestail about a gas/heat wedge forming behind a boatail bullet while it is in the barrel is exactly that, a wivestail. The pressure at any given point in the barrel is exactly the same as anywhere else. It is like saying the pressure inside the tank on your compressor is higher in the corners than the center. If boatail bullets ate up a barrel in 100 rounds do you think anyone would use them?

 

[BigDaddy0381]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: John L</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 8shots</div><div class="ubbcode-body">BD, that explains a lot. I inherited a 300 H&H from my dad, accurate as anything. Maybe he had pushed about 5000 rounds of flat based bullets through it. I loaded some boat tails, and it was'nt 100 rounds and the barrel was cooked. I had to replace the barrel. </div></div>

If the barrel of your 300 H&H already had 5000 rds. down it, the 100 rounds of boatail ammo did nothing to it. It was already toast. The old wivestail about a gas/heat wedge forming behind a boatail bullet while it is in the barrel is exactly that, a wivestail. The pressure at any given point in the barrel is exactly the same as anywhere else. It is like saying the pressure inside the tank on your compressor is higher in the corners than the center. If boatail bullets ate up a barrel in 100 rounds do you think anyone would use them? </div></div>
I agree thats alot of shooting but could the BT's play a part in in the barrel being worn out prematurly? if he stayed with FB could he got more shoots out of it?

 

[8shots]

Re: Heat/Fire Wedge

BD, my thinking exactly. That rifle was a tackdriver and could shoot, untill these BT was used. So I still think you got a point.

 

[John L]

Re: Heat/Fire Wedge

BD & 8shots,
Could 8 shots got more accurate rounds down the barrel if he stayed with the flat base bullets? I dont know maybe yes maybe no. Carbon steel barrels have been known to give up the ghost rather suddenly. My AR barrels are normally replaced between 3K to 4K rounds depending on the round count at the end of the year. I wont start a new season with a barrel past 2800. Let me state this now that when I change a barrel out it is still in pretty damn good shape and will still be a very good shooter up close. It will start showing an accuracy loss at 600yds first. I usually have another upper made and use the old one for practice until the barrel is complete toast. All of the rounds fired will have been boatail bullets. I really would have liked to have been able to look down 8shots barrel with a borescope, something tells me it would have been interesting.

 

[LRI]

Re: Heat/Fire Wedge

A flat base bullet is (in benchrest circles) more accurate than a boat tail.

The reason is stability and center of gravity. A flat bullet doesn't "wiggle" as long as a boat tail does before settling down.

The trade off is long range performance. Boat tails are less prone to bleeding off velocity and they have a slightly smaller cross section, so they get through the wind a bit better. This pays off in longer distances and they generally outperform the flat bullets in those conditions.

A general rule of thumb:

300 yards and below: Flat base.

300 and beyond: Boat tail.

Hope this helped.

C

 

[Unknown]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Unless you're shooting one of the hot magnums like the .300 WM or similar, how hot the barrel gets during extended strings of rapid fire will have a lot more effect on barrel life than bullet type.

Given that a .308 barrel may go 10,000 rounds before accuracy significantly degrades, the cost of replacing a barrel is completely dwarfed by the cost of the ammo to get it to the point of replacement, even if you reload.
</div></div>


If your getting 10,000 rounds out of a 308 with exceptional accuracy I want your barrel maker's contact # (please!)

Most palma shooters change tubes somewhere between 2 and 3 thousand.

Anything's possible I guess but I've never seen a 308 go to 10k and retain accuracy. </div></div>

Years ago I had a Springfield Armory M1A with a GI weight national match barrel. It shot 1-1.25moa groups for over 12,000 rounds, closer to 15000 actually. Then one day, the groups popped open to 3moa without anything between great and horrible accuracy. I'm certain that the barrel I had was a fluke. The best I have done since then with a 300 win mag is 950 rounds, with 308's, around 2000, just like everyone says. I'm guessing the barrel that lasted so long was a chrome bore..

 

[Lindy]

Re: Heat/Fire Wedge

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">If your getting 10,000 rounds out of a 308 with exceptional accuracy I want your barrel maker's contact # (please!)</div></div>

I guess that will depend on what "exceptional accuracy" means.

I am not a Palma shooter, but I know some. I've seen them swap barrels in the parking lot at a match. That practice strikes me as someone who is probably blaming his equipment for his own failures.

But I've seen .308s with match-grade barrels - not factory tomato-stake grade barrels - going well beyond 10,000 rounds, still shooting well below a minute of angle at 100 yards.

I've got about 6500-7000 rounds through the current barrel on my AI. It's still doing around 0.6" 5-round groups at 100 yards when I drive it correctly.

In one recent outing, I shot 21 rounds at 21 individual one-inch dots. All of the shots hit the dots. Some of those shots were fired in very short time periods - in one instance 6 seconds starting from standing, with the rifle on the ground and no round in the chamber.

(Do a search on the Sniper's Hide Dot Drill, or consult Lesson 23 in the Sniper's Hide Online Training)

Works for me.

 

[crumpmd]

Re: Heat/Fire Wedge

I shot my tomato stake barrel to over 7000 rounds before I decided I was able to drive the gun better than the barrel was shooting. I bought a Surgeon scalpel and proved it to myself and sent the rifle off for action blueprinting and rebarreled with a Kreiger(Phone: 262-628-8558). I am 50 and I expect it is the last 308 barrel I will put on that rifle. I am sure it will go >10K rounds. The Kreiger on my scalpel has nearly 3K now and is as good as the day I got it (it is 6.5X47L).