Bullet stabilization

[800X]

Hey guys,

Totally new to the 300 whisper. I have a 16" AR upper from Model 1. The first thing is, yes, I too had to move my gas block back to get the upper to cycle with subsonic ammo. Rather frustrating since I was assured on the phone that the upper was set up specifically for this. If I didn't have my own lathe I would have been very sad.

Anyway I happen to have access to an indoor range but its only 50'. So I find that my bullets are not stabile and making keyholes once in a while. This is mostly with the CorBon factory stuff, but also now with my first handloads. I have been using AA #9 and slowly creeping up the charge hoping a little extra speed will help stabilize. Now I have broken the sound barrier and still have problems.

So this benchrest guy tells me that the boattail Sierra 220 is made for long range and MAY not be 100% stabile at a measly 50'. This sound strange but possible. Before I waste anymore of my precious 220 MKs and can get to the range (its a PITA right now) could anyone shed some light on this issue for me?

Thanks in advance!

[Quarterbore]

As strange as that may sound I have heard this before. I am no expert on the topic but it was under very similar characteristics as we were shootig over a chrono for a 1000-yrd BR gun and shooting at short range. We saw the keyholes but the load shot great at 1000-yrds...

It does go against logic that the bullet is flopping at short range but I did see it once...

[jripper]

I have heard stories of this with the .50 BMG round also. I can not verify any of the rumors, but I have heard that you need at least 300 yards to fully stablize the bullet.

I have had problems with my .300 stablizing 240 sierras at 25 yards. I even pushed them up to 1200 fps and they still keyholed. My gun is supposed to have the 1 in 8 twist.

This is an interesting theory, and I will have to try some extended range firing to see if there is any difference.

The 220 corbon load does stablize at 25 yards in my gun.

The other thing you might try is using a slower powder. My own personal theory on that is that a slower powder may affect the bullet differently in the barrel, and may stabilize the bullet better. I have not tried this myself yet, but am planning on it.

I suppose that you should also look at what is on the end of your barrel. I have an A2 flash hider. A muzzle break or silencer may affect these bullets differently, as if they are, as I suspect, barely stable, a small variance as they are leaving the bore could throw them into a tumble.

Also, the trueness (I hope that's a word) of the break/flash hider hole, to the hole in the bore, will make a difference.

In regular rifle stuff, this probably would not been seen until you are at longer ranges, but with the slow speeds of the long heavy bullets, it may not take much to throw them off.

An interesting question is, even though they are keyholing, are they holding a good group?

I doubt if they are not grouping at short range, they probably will not group farther out.

However, if they are holding a decent group, but keyholing, they may be hope.

These are awfully heavy, long bullets at very slow velocities. It may take a little voodoo to get them to work right.

Joel

[jripper]

I just thought of another example of something similar. If you have ever seen an arrow being shot from a bow in slow motion, it has a very similar wobble when immediately leaving a bow. I remeber watching Byron Ferguson on the outdoor network doing trick archery shots. In one case, he was shooting an arrow through a wedding ring. I remeber him mentioning that he could not shoot too close, as the arrow had not stablized yet, and had to be a certain distance so that it had quit wobbling, and could make the shot.

I wish some physicist or ballistics expert would write in and tell us for sure, as it sure is a strange area in which there is lots of here say and rumor, but no concrete evidence.