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-   -   I've Almost Done It IV: A New HELP! (http://www.firearmstalk.com/forums/f21/ive-almost-done-iv-new-help-29422/)

Joshua M. Smith 07-18-2010 02:19 AM

I've Almost Done It IV: A New HELP!
 
Hello,

Yes, I skipped the "I've Almost Done It II" & III because the pun was just too good :D

In my ongoing quest to get sub-MOA 100yd groups from bulk ammo, I sort by weight and modify using D Rock's tool. I've recently switched to American Eagle 38gn HP. The bullet weight and powder charge are very consistent, but the cases are not - they seem to vary largely on the amount of priming compound, and some are therefore louder than others.

I come sooo close to sub-MOA 5 shot groups many times, and have broken it numerous occasions if I throw out a flier or two, but there always seems to be one or two that prevent the sub-MOA five shot group.

Here are two of the best groups I managed tonight, out of a total of three groups:

http://i19.photobucket.com/albums/b1...r/6615a37e.jpg

http://i19.photobucket.com/albums/b1...r/6cb3f5c5.jpg

As you can see, three are sub-MOA (with one three shot group being almost 1/2 MOA at 100yds!). However, I have vertical stringing.

I need to see if I can get some help with that.

My front rest was the rifle's bipod, and the rear rest was a squeeze sock.

I shot prone, sniper style (vs the one leg bent position I'd been taught).

I know I had a little vertical movement, but this much?

The wind was dead calm. I didn't have to adjust windage at all.

Do you suppose I'm at the mechanical limits of the gun, my own limits, the limits of the ammo due to the inconsistency of the primer charges and the whole sonic barrier thing, or all or none of the above?

My 'scope is a Mueller 4.5-14x APV. The rifle is a Savage MkII BTVS that I pillar bedded. The barrel is definitely free floating.

Torque on the action screws are 55in-lb front (this one has been modified to take a main bolt) and the rear, being stock, takes about 25in-lb or so.

Is there something I should be doing that I am not? Or am I just pressing the limits too much?

What do you all think?

Thanks,

Josh

c3shooter 07-18-2010 02:47 AM

My son, you have not yet appeased the Rimfire Gods. You do so by making a burnt offering of many different types of Match ammo, until you find the ONE that is pleasing to the patrons of YOUR rifle. :rolleyes:

FWIW, I have had fair luck with WOLF .22 LR Match, better luck with Nobel R-50, Lapua Master. Some of the Fiocchi Match is good in SOME rifles. Have a couple that like Federal Champion Target STANDARD VELOCITY. Greentag and TenEx did not impress me greatly, but your mileage may vary.

And IMHO, the .22 LR comes into its own at 50 meters. At 100, it is running out of steam.

Joshua M. Smith 07-19-2010 05:12 PM

Hello,

Thank you.

I can do sub-MOA all day with subsonic ammo, but I figured I'd see just how good I could be with supersonic bulk.

I figure with the turbulance from the shock wave, I'll have to hold that much more still.

Thanks,

Josh

c3shooter 07-20-2010 12:23 AM

Problem with supersonic .22 ammo is not that it is supersonic- it is that at some point in flight, it STOPS being supersonic. As I have had it explained to me (they used very small words and cartoons) as the bullet drops back into the subsonic world, there are two shock waves- heel and tip- and in dropping back thru those waves, cause the bullet to yaw- and Bob's yer uncle. The really good match ammo I have been running (little good that it does me) comes out of the barrel CLOSE to super, so does not drop back thru.

Either that, or the rimfire Gods are demanding sacrifice of a virgin.



Any volunteers? :)


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