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Offline TomP

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BC First Shot High
« on: September 16, 2006, 10:44:59 AM »
I've finally gotten back to working up a 405 gr cast lead bullet load for my BC.  At the range this morning I fired 6 shots at 100 yards.  The first shot was 10 inches above my point of aim.  The next 5 grouped at the point of aim.

I thought maybe I just pulled the first shot.  I went home and cleaned the rifle without taking off the forend.  To clean the barrel I use solvent and a nylon brush and patches.  The bore is clean in a few passes.  I run an oiled patch through it when done cleaning.  I was about to put it away but I decided to go back to the range and fire off 6 more shots.  Before shooting I ran a dry patch through to remove any oil film.  Once again, first shot was 10 inches above the POA, next 5 in a group at the POA.  While shooting the five I shifted the sand bag under the forend to see if it made any difference in size or location of the group.  It didn't.

My load is 29 gr IMR4198 behind a 405 gr National Bullet, hard cast lead.  Is this behavior typical of cast lead bullets or is something else going on?

BTW my best groups with 5 shots are about 3 inches with this load.  Certainly has room for fine tuning.  With 520 gr lead bullets I've made 3 shot cloverleaves with this rifle at 100 yards.  I still use the open sights for now but its gettin' harder every year.

Tom P.
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Offline quickdtoo

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Re: BC First Shot High
« Reply #1 on: September 16, 2006, 10:54:28 AM »
All of my H&R/NEFs like to be shot from a dirty bore, so just foul it and then shoot for score. I know of many, many hunters that won't clean their bores once they sight in prior to hunting season unless they hunt in inclement weather, most guns shoot best fouled, up to a point, depending on bore condition.

Even tho you're running a dry patch down the bore, that's not enough to wipe all of the oil out of the bore, it takes a solvent or alcohol or something more to make sure there's no oil present. If the search was working, I'd point you to a link on shooting from a clean bore and the difference it made to make sure there was absolutely no oil or solvent in the bore, it was quite enlightening!!

Tim
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Offline E Rex B

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Re: BC First Shot High
« Reply #2 on: September 16, 2006, 01:42:53 PM »
Tom,
When I finish shooting if I just pull a dry bore snake through my Handi it seems to shoot better next time out.  I will clean with solvent and oil then do the fouling shot but not too often.
Rex
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Offline Stan in SC

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Re: BC First Shot High
« Reply #3 on: September 16, 2006, 04:14:19 PM »
Not a BC but my ultra light .243 does the exact same thing so I just quit cleaning it good unless it is going to be put away for awhile.



Stan
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Offline bearfat

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Re: BC First Shot High
« Reply #4 on: September 16, 2006, 05:51:17 PM »
I've never heard of that big a jump. Wow 10". I have one firearm that displayed a quirky 5" high jump but after a few rounds  dropped and settled down from a clean barrel. I stopped shooting those bullets and the problem stopped also.

I've read where long range snipers are fully aware of point of impact change after their first round from a clean rifle. I have a cabin with a guy who has reloaded much more than me and insists on fouling his firearms before deer hunting.

I've also seen guys at the gun club shooting the benchrest competition always take at least 1 or 2 fouling shots with clean barrels before they went for a group.
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Offline trotterlg

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Re: BC First Shot High
« Reply #5 on: September 16, 2006, 06:06:46 PM »
The heavier the recoil and the slower the bullet is the more the first shot will differ from the rest.  If it is 10 inches high then it is going a lot slower than the others.  Try loading up a little hotter round for the first shot and see if that doesn't bring down that first shot problem.  Larry
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Offline bearfat

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Re: BC First Shot High
« Reply #6 on: September 16, 2006, 06:18:35 PM »
trotterlg I have seen exactly what you say happen, more powder brought the group down in height. Not all the time but with some powder/bullet combinations.

My pea brain doesn't understand the physics of this. Can you elaborate more?
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Offline trotterlg

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Re: BC First Shot High
« Reply #7 on: September 17, 2006, 06:35:06 AM »
The slower bullets take more time to exit the barrel giving the muzzel more time to rise, making the impact point higher, kind of seems wrong, but that is how it works.  Very fast light bullets have less noticable rise, my 17 Remington with 30gr bullets actucally  shoots a little low with the first shot for some reason.  Larry
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Offline TomP

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Re: BC First Shot High
« Reply #8 on: September 18, 2006, 07:26:37 AM »
Thanks for all the replies, guys.  I suspected it had to do with cleaning the barrel but wasn't sure.  I think I will try speeding up my load a bit to see if I can tighten the groups.  I'm trying to keep around or a little above Trapdoor Springfield velocities, say, 1400 fps max with 405 gr lead bullets.

I installed an FP rear sight and replaced the globe front sight with a blade with a bead.  I figured it would be easier to aim in low light hunting conditions with a blade front sight.  Does that make sense or is it better to keep the globe sight?  I haven't hunted with it yet so I'd appreciate any wisdom on that.

Tom P.
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Offline quickdtoo

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Re: BC First Shot High
« Reply #9 on: September 18, 2006, 08:28:33 AM »
For hunting in low light, I like a firesight, not much else compares in iron sights IMO, the only thing better is a scope!! ;)

Tim
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