Stability issues 300 blackout lee 309-230 mold milled out lube grooves

[DrewSeeg]

As the title says ... The boollet that is smooth is key holing and not hitting a 3 foot target at 50 while the other hits a plate with a red dot. I used an end mill to test a smooth boollet vs only removing the boat tail on the lee 309-230-5r mold. The only difference is that the smooth boollet has to be seated slightly further in due to rubbing on the throat while chambering (maybe need to size smaller?). Any ideas why one is so bad while the other isn't? Newer to the forum and casting for the blackout. Thanks for any input.

Running LC brass with 7 1/2 primers under 9gr of H110 sized to .311... Both cycle my gun with a suppressor 10.5 inch 1 in 8 twist barrel.

[osteodoc08]

That's a pretty big weight for 1:8 twist. A lot of the newer guns are 1:6 or even 1:5 to stabilize the heavies.

[runfiverun]

push the smooth one harder.

[DrewSeeg]

Might be the issue ... Forgot to mention the smooth one is 240gr while the grooved is 230gr. Thanks

And might try 10gr of h110 ... Didn't have pressure signs so should be OK ... Don't have a chrony either but trying too keep these subs.

[yondering]

Interesting; I'm not sure why you'd have stability issues with one but not the other, unless the body was bored off-center when you removed the lube grooves. What do you mean about using an end mill to test a smooth bullet? Did you ream the hole with an end mill? How well did you dial in the hole before hand, and did you do it at both front and rear driving bands to make sure the mold was straight relative to the quill axis?

I have to wonder if you ended up with a bullet body that is not in line with the nose; that would do it. Or, are the bullets so far oversized that they aren't concentric with the nose after sizing? End mills often cut oversized, and don't make very good reamers.

The increase in weight shouldn't have any effect; stability is dependent on length, not weight, and you didn't change that.

A 1:8 twist is fine. My 9" barrel is the same, and I use pretty much the same load (different primer) with the same bullet. 9.0gr of H110 in mine just starts to push them supersonic, so I usually keep it to 8.8-ish grains. You won't encounter pressure signs at 10.0gr, but most likely will have a supersonic load. A full grain increase in a load like that is quite a lot.

[243winxb]

Removing the lube grooves and boatail cause lead displaced by the lands to go to the base of the bullet. The deformation of the base hurts accuracy.

[runfiverun]

243 I'd agree with you.
but the last time I said that happened I got told I was an idiot.

[skeet1]

Instead of removing the boat tail I just gas check the bullet and have no leading problems. A regular .30 gas check just fits on the base of that bullet and thus makes it a flat base. I lube with Carnuba Red and it shoots very well.

Ken

[243winxb]

243 I'd agree with you.
but the last time I said that happened I got told I was an idiot. Well, its worse if using very soft alloys.

[leadman]

I would also think something did not go right in the machining. I have an RCBS Casemaster that I can check cases and bullets/boolits for out of round conditions.
I took the boat tail out of one cavity of my same Lee mold and it still shoots the same (not very well). The Lyman 314299 shoots much better for me.

[popper]

PC or painted? You have ~1" of Pb pushed to the base which will effect accuracy but the keyhole sounds like a different problem. The coating(?) thickness appears difference on your example - why you need to seat deeper? Extra friction from no LG may require a bit more powder. That is a bore rider and the nose might be getting damaged when cycling or as noted above, during sizing. Sizing smaller definitely won't help - nose sizing may. Or you could just shoot the ones with grooves.

[jcren]

If it is lead displacing to the base of the boolit, try some of the plain-base pop can gas checks. I got some from a member for like $16 for 1,000 and they help accuracy with plain base loads in 30-06.

[buckshotshoey]

Removing the lube grooves and boatail cause lead displaced by the lands to go to the base of the bullet. The deformation of the base hurts accuracy.

Im lost. Where did it say he removed the lube grooves? How?

Milling off the boat tail I understand. I take it by when you say "lead displaced", you mean changing center of gravity?
What exactly is he doing here?

[44man]

Displaced lead will form fins on the base to interfere with gas at the muzzle.
Be a good idea to check run out of the rounds too. It gets worse with a crooked start.

[runfiverun]

trailing edge failure.

I think this is just a case of more boolit weight slowing down an already marginally stabilized boolit.
I shoot the regular version in my 7 twist 300 at slower than slow and have it so close to the ragged edge that just a colder primer will push the accuracy right out the window.

[yondering]

243 I'd agree with you.
but the last time I said that happened I got told I was an idiot.

Not told you were an idiot, but pointed out that you were confusing theory with fact. You didn't have any evidence to support your theory, and I posted plenty of pictures showing it didn't work out that way in reality. I criticized you for continuing to push your theory despite evidence to the contrary.




The OP's load shouldn't be going slow enough to have a stability problem, and I know for a fact that the same load will push bullets up to 270gr over 900 fps in my barrel. I doubt his is much slower than that, if any, and 10 gr of weight shouldn't have made the difference between good accuracy and keyholing. Boring out the bullet body crooked, on the other hand, has a very good chance of causing keyholing.

[DrewSeeg]

Wow thanks for all the comments ... I definitely have a few things to think about! Yondering it could be (probably is) out of round ... Let's just say I have an end mill 5/16 (.3125) and something that turns making a hole! Essentially what I was doing was trying to make this boolit larger .... As 243 pointed out the front driving band was .305 (as shown in the schematic), so there is only a very small area that would touch the bore, which is the band right before the boat tale. But now after haphazardly milling out of the lube grooves, that front driving band is .311 and needs to be seated deeper to not get shaved while chambering. Originally, I could not get these bad boys to stabilize from the unaltered mold. Will probably stick with the one that is only the boat tale fix... But am still curious on what is going on here. Also, they are PC with a HF gun.

[243winxb]

http://www.bergerbullets.com/twist-rate-calculator/
Originally, I could not get these bad boys to stabilize from the unaltered mold. Stabilizing should not be the problem from running data in the calculator??

How is the muzzle's crown. Look ok or ? Is the bullet hitting anything on exit?
suppressor

Try a harder alloy? If to soft, the bullets could be skidding with that fast 8 twist.

[yondering]

DrewSeeg, the problem with using an end mill to bore a hole is they tend to cut oversize. If your end mill was .312", you may have a .312" hole, or it may be as big as .318-.320", depending on the end mill and the fixturing. If the bullets are grossly oversize, some sizing methods will size them straight, but some will size unevenly. How are you sizing? Maybe post a pic of your sized bullets? Also, is there any flash on the bullet base after sizing?

It does sound like you've just got the body out of alignment with the nose though. It would be very easy to do, and the most likely explanation for your problem. If you bore out the body in alignment with the nose (as I have on several), there is no reason to expect any stability issues with that bullet.

If you're using a drill press to do this work, next time, buy a long shank 5/16" reamer and use that instead of an end mil. The reamer will tend to follow the hole, while an end mill won't. With a reamer, run the rpm as slow as possible, and feed it fast. Shut the drill off with the reamer still in the hole, and withdraw it after the drill stops, not before. Make sure to flood the hole with WD-40 beforehand too; it's a great cutting oil for aluminum. This procedure will give you the best hole finish you can get without a mill.