New 10" barrel, bullet stability problems

[snipecatcher]

The current barrel has 155 rounds through it, and this has all been with A) 20 pieces of FC brass formed by Hoser, or B) 15 pieces of virgin LC brass formed by me. I just recently chunked the FC brass as the primer pockets were getting inconsistent. I picked up the 1680 today and I'm going to try some loads with it either tomorrow or Thursday. If that doesn't work, I'm taking the barrel to a local machinist who is going to borescope and pin-gauge the barrel. If there is nothing wrong there, I'm going to have him cut off the threaded portion and put a target crown on one of the barrels to determine if there is something wrong with the crown/thin walled threaded portion. By the end of this week, I should know what the problem is.

As to the question about the 150's, I've put some 155 Matchkings through it and they are not stable. 110 V-max's are. I haven't tried 125's, but don't think it will matter because there is definitely something wrong here. It SHOULD be stabilizing at least the 220 round nose bullets and the 175 Matchkings without a problem. I'll keep the thread updated as I find out more.

-Dan

[TCCrewchief76]

With the problems you are having with both Subs and Supers, I'd say it's time to slug the barrel. I honestly cannot think of anything else besides an oversized barrel at this point. An oversized barrel will cause tumbling with both Subs and Supers. Slugging will also let you feel the consistency of the rifling as the slug is pushed down the bore.

Kevin

[MadDog]

I had an SSK upper that was shooting the same way. I tried multiple loads with multiple powders at various speeds. 240gr SMKs and 220gr SMKs were not stable and were all over the target. 190gr SMKs appeared stable but would not group better than about 2" at 100 yards.

I never tried any lighter bullets because I was not interested in shooting them. Never tried supersonic loads for the same reason.

I tried Corbon and SSK ammo with the same results.

The barrel was 10" long threaded 5/8 - 24 with a 3 position gas block. It was a 1 in 8 twist that I verified.

I talked to JD about it several times to no satisfaction and finally decided to send it to someone else for a new barrel. I considered sending it back to SSK and trying to make them fix it but was not confident that it would be worth the trouble and that it would be better in the end.

I really don't know what the problem was.

Good luck with your rifle. I am hoping to have my upper back soon with a new barrel.

Joe

[snipecatcher]

My last bit of hope was 1680 powder. I tried it this morning and I'm still getting understabilized bullets, of course. It's also too slow for my rifle. I had a couple cases that were covered in soot all the way to the case-head, which I attribute to them being yanked out of the chamber too early. I don't have a problem at all with this, because the faster powders that it runs best with will be quieter, if I can ever shoot the rifle with a suppressor. I'll be taking both barrels to my machinist friend on Saturday morning to try and find what's wrong with them. I've never looked through a bore-scope, and I'm looking forward to it!
-Dan

[Hoser]

Powder will make zero difference in bullet stability. Bullet speed/RPM is stabilizes a bullet.

The longer/heavier a bullet is and the slower you drive it, the faster the twist you have to have. What powder you use to get it to that magic RPM does not matter.

The borescope results should be interesting.

[i8asquirrel]

what distance are yoiu firing at?
I was having trouble with 200 nosler BT. full Keyholes at 100yds. I tried 190 gr Hornady SPBT and had wonderfull luck. ( lenght of bullet ,center of gravity?) anyway you might try some different OGive style bullets , Good luck

[snipecatcher]

I've tried a fairly exhaustive list of bullets/speeds mostly at 100 yards, a couple at 50 yards. I get the same results with both barrels. There is something wrong here. If I didn't have a bolt-action before this that ran well, I would probably be turned off by the whole idea of the 300 BLK and give up. But I KNOW that it can and does run fine when everything is right, so I'm going to stick with it. The machinist I'm going to tomorrow suggested that there may be a tight spot in the bore that is swaging the bullets down just enough to give them problems as they leave the muzzle. We shall see.

[TCCrewchief76]

What does the resistance feel like when you run a patch down the bore?

[alorton]

I'm looking forward to seeing what you find out. I've read through the thread and I'm stumped, especially since there are problems with two different barrels.

[Hoser]

Originally Posted by snipecatcher

I get the same results with both barrels.

By any chance were both these barrels made from the same blank?