New 10" barrel, bullet stability problems

[snipecatcher]

Thanks for the advice, and I wish I would have thought of that yesterday. I drove 2 hours to a place on private property where I can shoot however I want. I was shooting into a mound of sand. I didn't even think to try and find one of the 240's, which was stupid, as I doubt they could have gone far going sideways. I may try to work something out with a guy I know down here to fire a bullet into a mound of sand and dig it out. I'm leery of shooting a 310 bullet out of a 308 bore, especially with this cartridge. I know people do it with the 7.62x39, but the risk of going over-pressure, or sticking a bullet is too high for me.
-Dan

[snipecatcher]

I slugged the bore, but I'm not sure what it's telling me. From land to land, it's .306. From groove to groove, it's .308. This seems normal to me. Everything looks uniform all the way around. I'm ordering some 150 grain round nose Sierra Pro-hunters to try. I think these are the heaviest bullets I'll be able to use in this rifle.
-Dan

[pud-knocker]

Originally Posted by snipecatcher

I slugged the bore, but I'm not sure what it's telling me. From land to land, it's .306. From groove to groove, it's .308. This seems normal to me. Everything looks uniform all the way around. I'm ordering some 150 grain round nose Sierra Pro-hunters to try. I think these are the heaviest bullets I'll be able to use in this rifle.
-Dan

.306/.308 ????

sounds like a pistol barrel land/groove ratio, a shot-out pistol barrel.

.299 to .300/.308 is what I would think you would want in a .308 rifle barrel.

[snipecatcher]

That's the best I can come up with.

Looking back at all of my data:

175's need to be going 1500 fps to be stable.
110's are stable down to 950 or so.

Plugging these numbers into JBM's stability calculator, I theoretically have about a 10 twist barrel. This is figuring in at least a 2.2 stability factor, which I've read is necessary when shooting subsonic.

[Titleiiredneck]

If you would like to catch your bullets you can shoot into 6" of wet media "phonebooks are best I have found" Try a 200+ grain projectile should work fine, if it penetrates you may need 2 more books "I live in a small area so I needed 4 to start with" I have used this method on subsonic 45 9mm 357m and 45lc in the past and it worked well. You will want to use a bthp as the plactic tip types may deform too much.

To test get a 5gal bucket of water, soak books and place them in a milk carton or wood frame. Books need to soak for about 5 minutes or less otherwise the glue may unbind. If you cant get phonebooks you can always go by wallyworld and buy a few packs of printer paper, that should work as well.

[TCCrewchief76]

Originally Posted by pud-knocker

.306/.308 ????

sounds like a pistol barrel land/groove ratio, a shot-out pistol barrel.

.299 to .300/.308 is what I would think you would want in a .308 rifle barrel.

That sounds like Marlin Microgrooving to me. Those lands should be measuring around .300", plus or minus a thou. That bullet is just being slid down the barrel with wreckless abandon. I'm surprised that thing even hits paper being a "smoothbore" and all...
If you think about it, those lands are only .001" high. Time to get a barrel replaced.

Kevin

[fasttwist]

Well, at least you found your problem. I would like to see the jacket of the bullet that came out of that barrel.

[BWE Firearms]

Who is the barrel manufacturer? If your measurements are correct your barrel is way out of spec for a .308 dia. barrel. I want to make sure I never use that brand of barrel in any of my work.

[snipecatcher]

Going to get a couple bags of sand and headed out to the range. I'll catch a few bullets and see what they look like. Barrel is a Douglas.

[snipecatcher]

Bullets were going into the sand and then turning sideways, so half of the bullet is "sanded" rough, impossible to see rifling. It's tough to get any data out of the 4 bullets I recovered. I called Douglas Barrels today and they said to send it in. I'll ship it out today, so no new info for at least a couple weeks when I hear back from them, unless Hoser gets a chance to mess around with the barrel I sent him.
-Dan