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Humbling experiance the other day. Maybe someone else can learn from this!

 
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  #8  
Old 12-13-2008, 04:19 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

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Originally Posted by meichele View Post
I may be seating ALL my bullets long and just shove them into the lands during chambering to avoid this problem and just work up loads with them into the lands. Not sure if I will do this or just reset my die for new bullets. More experiments are in order.

Later
"Shoving them into the lands during chambering" is called "jam fit seating", and is a technique favored by some benchresters. It often yields the best accuracy, but I've abandoned it for PD loads after having too many bullets stick in the chamber, filling receiver with powder after extracting a loaded round.

I would never use this technique for big game loads.

Last edited by LewisH; 12-13-2008 at 04:25 PM. Reason: typo
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Old 12-13-2008, 04:53 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

I had a similar experience a few months back in my 22-250. Though i didn't have any pressure problems, my accuracy went to Sh** to say the least. At the time I was measuring COAL from head to tip..so when I ran out of 50g. v-max, I went and bought more, loaded to the same "COAL" a went shooting...that's when the above happened.

So after some head scratching, I go out and buy a bullet comparator and start checking Head to Ogive lengths from the old lot of reloads to the new. What I found was, even though COAL was the same the head to ogive measurement was different my a margin of .020!

Moral of the story...use a bullet comparator when measuring OAL. That way you always measure of the part that's parked in or in front of the lands..

Nate

Last edited by mrdeeds; 12-13-2008 at 05:00 PM. Reason: spelling
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  #10  
Old 12-14-2008, 02:10 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

I saw you said they were Accubonds. I live in Or and business takes me to bend quite often and while there I stop by the Shooters Pro Shop at Nosler. I usally by the seconds for shooting (they have over runs of first for winchester quite often. Different color tips (red)).

I was getting unexplained vertical at 600 yrds so I started measuring the bullets Base to Ogive with a stoney point comparater. I found them to vary wildely even within lots! I now sperate them by weight and base to ogive. You can pick up seconds for $13.25 per 50 for 160 7mm AB. This allows me to be selective with weight and measurement.

When this came up i talked with the old guy that worked in the store. He was a long range guy and he was supprised by the variance and was heading home to measure his..He was getting vertical problems as well.

What i found is there tolerances are based of hunting situations not Benchrest. The average guy would never know the difference.

Another side note. When you buy Nosler brass. They say its weight sorted which it is but not weight sorted between lots. Its weight sorted PER BOX. So if you want a 100 peices you take the risk of the two boxes being different weights.

Willys
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Old 12-14-2008, 04:23 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

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Originally Posted by gbp View Post
was there a difference in ambiant temperature? or was the cartridge allowed to rest in a hot chamber for an extended time?
I do not let cartridges sit in a hot chamber.

Ambient temps were within 5 degrees.

NOTE: The original bullets at my OACL measurment were .020" off the lands. The new ones, at the same OACL were .002"
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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Old 12-14-2008, 04:58 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

I've seen where new "lots" of bullets can have longer base to ogive measurements. BUT, I don't think that .018" diff in seating depth is gonna crank up that kind of pressure and velocity diff. Maybe if the bullet was actually jammed in the lands? I guess the way to find out if that really was the diff would be to just seat the new bullet .018" deeper.....but I think something else is at play here.
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Old 12-14-2008, 07:03 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

Quote:
Originally Posted by kraky1 View Post
I've seen where new "lots" of bullets can have longer base to ogive measurements. BUT, I don't think that .018" diff in seating depth is gonna crank up that kind of pressure and velocity diff. Maybe if the bullet was actually jammed in the lands? I guess the way to find out if that really was the diff would be to just seat the new bullet .018" deeper.....but I think something else is at play here.
Bear in mind I am shooting a big tempermental case at MAX loads. It doesnt take much to send them over the edge.

I did however seat them back .020" and the velocity went down conciderably. The velocity with the new lot is still higher than the last one but MOST of the velocity spike was from being right off the lands.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #14  
Old 12-14-2008, 08:26 PM
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Re: Humbling experiance the other day. Maybe someone else can learn from this!

I had an experience once with my 30-378. I was also shooting 200 ab's with max loads. Everything was going fine with probably 20 rounds down the barrel. It was winter and I was letting the barrel cool. I could shoot 2-3 shots and then let it sit.
Anyhow all of a sudden the chrono showed a quick gain of about 40 fps and an ejector mark appeared. Well maybe my scale hung up a bit and I got a bit more powder in that one. The next one jumped about 80 fps and the bolt was really sticky. I stopped there and pulled the last 6 rounds down when I got home.
Only thing I can think of that might have happened is my barrel fouled out and that big long AB just didn't want to go down the tube as ez as the earlier shots.
Obviously this wasn't what happened to you but it is the kind of thing you can run into when playing with the big overbore cases. When you got so much case and velocity you should be happy to stop 50-100 fps shy of max loads but so many of us like to keep the pedal to the metal!
For me it was another lesson about valid hunting loads. We all know that sometimes we can't keep our barrel as clean in the field as at the range. Temp changes, moisture, dust....you name it can all come into play. (Like 4 straight days of Alska rain on one trip!) Finding loads at the range that run redline are kind of useless out there in the field.

Last edited by kraky2; 12-14-2008 at 08:30 PM.
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