dinker with this, do you believe it?

[foxhunter]

gary i am easily confused, the program deals with accuracy, where did the fps come from? the program seems to be some what one dimensional, it doesn't deal with the actual pressure of the loads from light to heavy unless you know what pressure 12.0 gr of 1680 produces and then compare it to 14 grains of 1680.
it does say a load of 12.0 grains at 50000 psi will deminish a barrels accuracy life quicker than one loaded to 50000 psi with 14 gr of the same powder.

my calculations on it indicate that 12.0 gr aa1680 with a psi of 45000 will have a accuracy life of 3074, the same pressure at 13.5 will have an accuracy life of 3620.
however the 17 v-raptor with 10.4 gr 1680 at 50000 psi only has a 1311 accuracy life, having a hard time wraping my mind logicly around that.

[GLWenzl]

No….. Actually I am good at confusing things…

I viewed the program was about barrel life, accurate barrel life to the point when accuracy tapers off???

Yes, I agree the program is all about pressure and since the program was basically useless to me and probably most everyone except for those who are privileged enough to accurately measure pressure with different loads I tried to make the best use of it that I could….

I figure to a degree pressure = velocity so I just took some loads that was very close in velocity thinking they could be similar in pressure for comparison. Didn’t for a minute think it was accurate. You said dinker and believe me I did! Even gave me some play time to dinker with the new excel stuff I have been trying to learn!!!

I did however go to Ramshots load data to see what kind of pressure a 20 BR would run with the same loads I am using although I realize it could vary a bunch from riffle to riffle…

Then I noticed how powder charges seemed to have a sweet spot in the middle of the road. Like you it made me wonder what was going on… I was surprised to see barrel life start low life with low charges and climb higher then back lower… Yes maybe the program has an error in it but I am in no position to prove it wrong so I tried to see what I am missing…. Every powder I tried had a shorter barrel life with lower charges made me think is it unburned powder going down the tube cause more barrel wear… Pressure spikes with lower loads??? Maybe a longer burning time??? (I remember with my 14” 17 AH had a much bigger fireball coming out of the muzzle at night with the lower end loads than the higher end loads)…

Anyway I figured someone with some powder and pressure savvy could explain it for us….. Sorry for the cornfusion

[bohica2xo]

That program looks good - for calculating the number of sheets on a toilet paper roll...

I have a little 7mm that runs just fine on 20 to 25 grains of RL7. According to that program, it is good for FOUR shots. Uh huh. Nothing could be easier on a barrel than that little 7mm. The program predicts 2710 shots @ 45 grains of the same powder...

221 Fireball. 50 grain bullets. 16 grains of 4198. 392 shots? Really. But 21 grains of BLc2 will shoot thousands of accurate shots in the same case...

50BMG loads indicate a barrel life of 759 shots, with a load I know wins match after match in the same barrel.



Seems to be a lot of error at either end of the scale. The program mighr be ok for a 6mm rem or a 222, but it will be way off on small capacity stuff, and not so great on the big stuff either.

B.

[foxhunter]

i'm sure glad it wasn't just me that notice the double standards.

[sicero]

With this information in mind. I have a bunch of prairie dog rifles that will need new custom barrels this spring. I will tell the wife so she can get them ordered. All kidding aside, I think they have statistics on military rifles with 10, 20 and 30 thousand rounds thru them. Kenny

[georgeld]

Some of you numbers players run this one and see if it agree's with what actually did.

sako vixen .222mag original from new.

just over 6100 shots it stopped hitting anything and went to scattering at least six inch groups.

Only load ever fired in it was: 55gr Rems, 25.0gr 4895=3000fps

So far, that's the only barrel I've shot out. Replaced it in a hurry with the elcheapo A&B from Midway for $70/blank. Puts them all in one hole about 3/8" or less, best has been .230" with less than 200rnds thru it still while developing a load. That was: 23gr AA2200 w/40gr V/max =2960fps

[bohica2xo]

George:

According to that program, just over 3500 rounds your barrel was junk. Too bad you wasted all of those components shooting that worn out barrel... LOL

Military barrel life is a big subject of debate currently. They threw a lot of money at research for a "shot counter" to be built into the M4 rifle. It is well known that you can blow up (split into a big flower, blow the handguards clear off the weapon) the skinny M4 barrel after about 8~10k rounds. Actually, I can blow one up at less than that with GI ammo.

They fixed the problem by putting some more metal back into the barrel. The failure mode was not what they thought it was (told the dummies so 5 years ago!), and the shot counter has been shelved for now. Currently they consider barrel life to be 5000 rounds, or when the erosion gauge says it is junk. 4 MOA is about what you get from a new barrel with M855 ammo. With some full auto fire and about 3000 rounds downrange, many will still deliver 4 MOA. Cleaned with a segmented steel rod, dropped on the dirt once per day...

I have no doubt that a bolt gun barrel in a similar caliber with good maintence will go 6k rounds below 1 MOA. Bear in mind that your six inch groups were still acceptable for an M16 or M4.


B.

[georgeld]

That's what I was wondering, thanks.

sure a lot of prairie dogs wished I'd tossed it out at that count.
Until almost 6000 shots it never made a group on paper bigger than a dime, ever.
But, seldom shot paper as there was too many p/dog's needing a cure. When it got where I couldn't hit them at 80yds, even the big fat one's hopping up and down chirping at me, daring me to try another shot. Knew something was wrong. That was the Sako tube, bedded hard full length.

Free floated on gunsmith's advice and got it down to about 3" for close to 400 rnds til it got wild again in the middle of fur season. was only down three weeks to rebarrel, restock and reglass it to .223 and develope a load. Within the first two weeks it nailed 12 coyotes. By then they were starting to get ratty so I stopped and started working on p/dog's again.

Funny thing about that Sako barrel. from the day it was brand new it had three or four buldge's along the bore. We saw that before I ever shipped it home from Germany., The gun club said just take it, can't get another one before I shipped out for home myself. SO I did.
I've still got the barrel as it came off the gun.
Have thought IF I could find someone to reline it for .17 and pick up another action I'd do it. but, haven't found anyone willing to reline it and I don't have equipment to do it. Doubt I could follow the bore either.