Discussion in 'Handloading and Reloading' started by docsleepy, Apr 7, 2013.
Metal temperature is a possibility, although the data that I've gotten so far doesn't seem to support it. Not much difference between days of widely varying temperatures
I don't really think that I have any Flinch. The gun is fully in a benchrest. My other guns are Mosin-Nagant's. With either, I can hit clay pigeons at 200 yards reliably. What is odd to me is that the Mosin-Nagant, highly modified, does not have the cold barrel effect at all. Nor does my 6PPC.
I usually wait one or two minutes between shots. These rounds are each hand loaded into the chamber.
As a primer ignites and fires the bullet it creates a harmonic through the steel of the barrel. The cold steel or clean cold steel will react differently than after the first shot.
Like some had said, if your rifle puts the first round consistently high, but centered, you can either compensate for it or ignore it. Most of my first shots through a clean cold bore, I aim off target as to me it is a fouler. Unless in a hunting situation, in which case I compensate by holding where I expect the cold bore shot to go.
New Scope Trial
OK, here is the first, second and third shots after changing out scope to identical 4-16X scope. These are done at 50 yards (the farthest I dared attempting boresighted shots). Visually boresighted and let 'er rip.
New scope with ring screws loctited.
Front rest identical Rock BR.
Used some of remaining batch of annealed, full length sized, handloaded rounds.
Rear Rest identical
Position held steady well within 1/4", firm hold as usual for this firearm.
Barrel dirty, not cleaned since last shots, outside temp approx 80 F or hotter, done in shade as usual.
Didn't think to chrono (sorry!)
First shot is obviously high (remember this is 50 yards not 100 as previous).
2nd and Third shots are right on each other.
So I'm beginning to wonder if the threads on the barrel are shifting or something with the first shot. This is a stock standard Savage receiver, never blueprinted.
Today ill try to chrono first and following shots. Wonder if the rifling has a bend or something else odd.
It's unusual for a rifle that doesn't need a gunsmith's attention.
I've ordered a Shilen, Chrome-moly match, blued
7m08 standard chamber (I neck down .308 cases so I'll have about .004" total clearance, which will be reasonable for a hunting rifle/target rifle)
22" total length (selected to maximize stiffness, and the sporter was 22")
S8 Bull Barrel (just like my 6PPC). 1.05 all the way
9" twist (which will allow for heavier bullets or slower speeds)
The last Shilen I got went onto my 6PPC and although it is not a world-beater, it was absolutely reliable.
I'll try to chrono today, dunno if it will work, because I have to get the FIRST SHOT.
As you can see from some of the groups, firing every 2 minutes gives touching shots....so barrel heating is a minimal effect.
This rifle was bedded, and I rechecked it recently.
Much hotter in Florida, 85 deg F. GNATS!!!!
As you can see, once again the first shot of high, this case by 1 inch.
The 3rd shot is the low one, I can't explain that.
There are nine shots total and as you can see, the rifle groups pretty well when it is not the 1st shot. The 2nd shot is somewhere in that glob of holes.
VELOCITIES: I dont' have the diffusers, so my chrony is very picky. It malfunctioned on most shots.
1st shot was 2914 fps
4th shot was 2902 fps (in the glob)
8th shot was 2992 (in the glob)
9th shot was 3023 (not sure where it went)
So yes, the first shot is somewhat slower. If that held up, I might could have some rounds with 1 extra grain of powder?
But the shilen barrel is on order now. 9" twist, bull barrel, 22" (short, thick), chrome-moly.
Oh -- one commenter wondered if my rifle "settles" in the rear bag after the first shot. I would consider that a possibilty -- except I do NOT see this with my 6PPC in the exact same front/rear rest.
Sorry for the abrupt answer. It was more to combat the idea that it's perfectly acceptable for the "cold bore" shot to be outside of the group. I don't believe it to be acceptable at all, and every rifle that I've owned which exhibited that behavior was rectified by handing it to a qualified gunsmith and working the problem together.
The important thing to do is log this behavior, if you aren't already. Then subsequently log any action applied to rectify it. By this method you can close in on the problem through the process of elimination. It helps to have other highly qualified shooters at your disposal during this process in order to eliminate yourself as a variable.
Personally, I would pop the barrel off and true up the action. If I'm removing the barrel and truing the action, then it also holds true that I'm putting a new barrel on. If those two things are happening, then it might warrant a new bedding job as well. Any rifle I've had which was exhibiting the symptoms you have documented here, was wearing a factory barrel. Upon rebarreling/truing/bedding... the problem no longer existed. As a result, it's very difficult for me to be able to point at a single root cause. I rarely expend any effort "forcing" a factory tube to shoot. If it doesn't shoot, it gets ripped off and I don't think for a second about it.
I'm sorry if that's not much help, but you may find it to be a reality of your situation. I am thankful that you're documenting your experiences here though... because I believe that when you solve it, you will have effectively proven that no one should be forced to live with a cold bore shot that drops any differently than the rest.
Since I'm not made of money, I go at things a little bit on a smaller scale. The only action that I've ever had trued, was a Savage action that shot well before it was trued, and did about the same after. That particular action got oodles better when a Shilen bull barrel went on it, and even a bit more when the trigger was changed out. It shoots the same first, last and middle.
I have records on this gun since I put it together about a year ago. It got significantly smaller groups with I made one improvement a month or so back (that I haven't revealed yet in these writings). It had always seemed to have something "wrong" with the zero wandering or cold shot or something but I couldn't put my finger on it with so many other variables enlarging the groups. Learning how to do repeatable neck annealings removed a very obvious zero-drops-each-reload issue, and then my undisclosed improvement took the groups down to "touching" shots. This sporter 7mm08 barrel had never done that before. At was then that the cold-shot-error became blatantly obvious and since I couldn't figure it out, after several weeks I went to THR for advice. Thus the scope change, bedding check, etc etc. Still no fix. So now, will change the barrel. That I can do myself (as I did the 6PPC, and this 7mm08 as well) since it is a Savage.
I also have a Mosin Nagant that I've been working on and now have it shooting groups <1" ("touching") at 100 yards. What got me going was that it has NO cold-bore difference, and I wondered why a 74 year-old gun was outperforming a modern hunting rifle....
I don't understand. Why would you shoot a mosin at 100yds when the target is still well within bayonet range?
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