• If you are being asked to change your password, and unsure how to do it, follow these instructions. Click here

+P chambers

Status
Not open for further replies.
So, is it a +p or more of a +v! Seems like the wrong letter is being used unless you are actually running higher than saami pressures?
 
In this context I'm interpreting +p to be the practice of long throat chambering to keep the pressure spike down on hot or slightly more than hot loads. Not a new concept in the industry, used to success in a lot of the magnum family lines over the last 50 years.
 
I have zero hesitation using DE +P in the right application. I feel like I understand the the pros and cons. I also use N570 when it produces the desired results on a target at 600yds. If H1000 is more consistent I will happily take the lower velocity and many of my loads are H1000.

I understand that my barrel will not last 800+ rounds and my barrel will start to degrade around ~400 rounds. I am not asking for a barrel warranty. I don't care if someone else thinks ~400 rounds is unacceptable.

I tend to run normal pressures at the expense of wear and tear on the consumables (barrel). I see loads posted from time to time that seem well in excess of the normal pressure. I would rather run a +P chamber at normal pressures than a standard chamber at max pressures. In my mind, if you are matching my velocities with H1000 and a standard chamber then you are running much higher pressures and stressing all of the parts that see the pressure. I certainly see the logic of normal pressures with a standard non +P chamber.

I would not run a +P on a high round count rifle. I would not run N570. If I expect good barrel accuracy out to 1000 rounds I am also not going to run a barn burner cartridge such as 28 Nosler, 300RUM, 30-378, 338 Edge, 338 Lapua Improved, 33XC. I am going to run 6.5CM, 308WM, 338NM.

My point is that there are numerous choices that contribute to barrel life and +P is just one of them. In my mind +P makes sense for a few of my projects where I am searching for performance rather than longer barrel life.
BINGO!!!! Has been great in my 300 PRC with H-1000. And my 338 Edge. But I had no reason to do it in my 2 different 28 Noslers. I think it's exactly what jensen said, you have to be smart about which calibers you choose to do it in, and you need to be smart about how much is too much.
 
I would prefer some throat plus a 1* leade angle, much is to be said for a tight throat keeping a bullet aligned when there is wear. The only issue with .0003 over bullet dia throats would be variations in Bullet pressure ring dia and shank dia in different lots of bullets.
PO Ackley spoke of this in keeping down pressures while getting the bullet started straight into the bore. Much is to be said of Gentle engraving pressures as the bullet enters the bore, and SD goes way down.

Another worry is the reamer grind, as there is a +/-0.0005 tolerance by most reamer makers, JGS and Manson are usually very, very good!

With the Teslong bore scope, you can save pics when the barrel is new, and document the wear over time, it is a humbling thing to watch....an education costs money. After shooting a variety of powders, you will feel like some powders ought to be illegal as to how they fire crack a barrel, and VERY difficult to remove the carbon from their use.

I am shooting a 257 Weatherby with a 9T, 25" and 115g Bergers are shooting pencil eraser size groups at 3590 fps with a reamer that has .030 freebore, with the 110g Accubonds shooting bug holes at 3600-3610 fps. This gun is not supposed to shoot like this but there are 4 more barrels that do the same in our family made off the same reamer on Non Trued Rem 700s in Boyd's stocks. We did the same thing with the 7 STW, and still have the reamer...amazing results.

Heaven knows I have made some crazy wild cats in my life, +P, I am not drinking this flavor of Kool-Aid.
 
Jensen, I hope you are watching the throat with a bore scope.
I do check the throat with a borescope although the limited data and large number of variables between guns makes it hard to draw any specific conclusions.

I generally see more damage on my 30cals trying to push 220-230 bullets at 2800 to 3000fps. The efficiency with which a 338 launches a 300gr bullet is impressive and the wear and tear seems to be very reasonable given the amount of energy sent down range.

Again, +P is simply an option to ease the bullet into the shorter height lands such that pressure doesn't spike as high as the rifling engraves into the jacket of the bullet. Nothing more than a longer transition versus the taper that already exists. Ideally, you want to push on the bullet with the same safe maximum pressure all of the way down the barrel. The goal is to get the same result each and every time.
 
Are there types/styles of bullets that don't perform well in this type of chamber/throat? Example: 45-70
 
Was it just the +p throat portion of this barrel that was bad, or the whole thing fire cracked? If a guy had a 30 xc with a standard throat pushing the same size bullet the same speeds as the 300 rum +p does that void the warranty?

I get that it's your business and you can do what you want but are we going to have to check with bartlein like a suppressor manufacturer to see if the cartridge we want to run is acceptable to you? What if it was a 308+p that went in 600 rounds (nope it was a +p not our problem)?
 
Status
Not open for further replies.
Top