How much Bullet in the Case Mouth

[DirtySteve]

OK, I was attempting to use my Uni-throater to lengthen the throat in my 308. I cut way more than I intended to. (New barrel already ordered) Any way I am going to try to shoot it tomorrow with a few test rounds. They are 210 VLD's with about .15" in the case mouth. Well not counting the boat tail...15" of bearing surface touching the case mouth.. I can not remember what jump that will give I was slightly miffed at my faux pas...

I had used it before successfully but just did not take enough time to do this right..

Any way take this as a warning..They cut quickly..

 

[JEFFPPC]

You will know the answer after you shoot it. Let us know. Might require careful handling of your ammo. In a ppc or br case with lighter bullets no problem, I have done lt often. Might depend on the amount of neck tension.

 

[Straightshooter1]

OK, I was attempting to use my Uni-throater to lengthen the throat in my 308. I cut way more than I intended to. (New barrel already ordered) Any way I am going to try to shoot it tomorrow with a few test rounds. They are 210 VLD's with about .15" in the case mouth. Well not counting the boat tail...15" of bearing surface touching the case mouth.. I can not remember what jump that will give I was slightly miffed at my faux pas...

I had used it before successfully but just did not take enough time to do this right..

Any way take this as a warning..They cut quickly..

I've had ~.150 (maybe .010 more, if I happen to recall correctly) and they did just fine in my .308. Though they did not fit into my mag at the time and I had to hand feed them. So I'm pretty sure you're would do just fine as long as you hand feed them. If they fit in your mag, you might test a couple to see if there's any problem with them feeding or if the feeding knocks the concentricity too far out.

 

[JohnKielly]

Might depend on how snug your throat is.

 

[bainp]

I have gone as small as 0.060" of the bearing surface in the case. You really do need to handle your ammunition pretty carefully though, with this little bearing length in the case. Often the chambering reamer will cut an extra 0.025" of neck in your chamber over the normal maximum length of you case. You could let the case grow in length a little to get a little more hold on your bullet. If you went down this route, it would be a good idea to drill out the primer pocket of one of your fired cases and put your bore scope through the case to see how much clearance between the end of the case neck and the end of the chamber neck there is.

 

[XTR]

Personally I think you’ve got it about perfect. I think about half a bullet diameter is where you want to be.

I had one barrel that I throated for 200 hybrids just before I bought a few thousand 200.20x When they first came out. Shot them with about .080 beari surface in the neck. Best shooting setup I’ve ever had, but it was right on the edge.

 

[DirtySteve]

I should have mentioned it is a single shot action. So magazine length is not a factor.

I was surprised to see bumping up to the 215 hybrid was less helpful. They have a long boat tail.

I will try some this afternoon. But a new Bartlien is OTW.

 

[DirtySteve]

I have gone as small as 0.060" of the bearing surface in the case. You really do need to handle your ammunition pretty carefully though, with this little bearing length in the case. Often the chambering reamer will cut an extra 0.025" of neck in your chamber over the normal maximum length of you case. You could let the case grow in length a little to get a little more hold on your bullet. If you went down this route, it would be a good idea to drill out the primer pocket of one of your fired cases and put your bore scope through the case to see how much clearance between the end of the case neck and the end of the chamber neck there is.

I will give this a try. I have a Teslong.

 

[jepp2]

For my smaller diameters, I prefer nearly a bullet diameter. On my 204 R, one cold morning I was shooting it with half a diameter of bullet seating depth to get close to the lands. When I fired one, I didn't hear a report. I opened the action to find powder spilling everywhere. The primer had fired on that cold morning, but the powder hadn't ignited. The primer had just enough kick to seat the bullet in the lands.

I now carry a supply of various diameter brass rods with me. They are 36 inches long, and if you ever lodge a bullet in the barrel, just drop the correct size repeatedly down the muzzle with the rifle standing upright. It will bump the bullet right out. No hammering necessary.

On the 308 diameter, I would go less than a full bullet diameter, but it will somewhat depend on the neck tension you are running. If just target shooting, you might consider a soft seat into the lands. Might give you more consistent powder ignition and improve your accuracy.

 

[338 dude]

OK, I was attempting to use my Uni-throater to lengthen the throat in my 308. I cut way more than I intended to. (New barrel already ordered) Any way I am going to try to shoot it tomorrow with a few test rounds. They are 210 VLD's with about .15" in the case mouth. Well not counting the boat tail...15" of bearing surface touching the case mouth.. I can not remember what jump that will give I was slightly miffed at my faux pas...

I had used it before successfully but just did not take enough time to do this right..

Any way take this as a warning..They cut quickly..

I’ve always heard as a rule of thumb leave one caliber in the neck so I guess .308

 

[DocBII]

Steve,

I've used 0.050 on regular 210 JLKs in a factory Remington .308 without problems. Even managed to get them to 2700f/s with all the powder they held, but the brass didn't last long.

HTH,
DocBII

 

[DirtySteve]

Well my testing my be put off for a day or two. I need to pick up my coyote rifle from the smith this afternoon. But if I can get home in time I will shoot a few. Starting to get dark here early in the evenings.

 

[Lucky Shooter]

I'm glad you posted this Steve, been wondering about this also.

The old practice of "one caliber" of bullet bearing surface has been
around for a long time but can't always be possible.

The entire neck of the 223 Rem is shorter than .224", this isn't the
only round with the neck shorter than the bullet diameter.

Some chambers with free bore also don't allow the prescribed
bearing surface if the bullet is seated to the lands.

I'm looking forward to this thread and in the meanwhile, as the man
said, test it for yourself.

A. Weldy

 

[NorCalMikie]

All of my chambers (except the gas guns) are cut with ZERO freebore. I start off with "full neck contact" and the lightest bullets I can find, jammed into the lands.
From there, I'll go to heavier bullets "as the throat wears" to keep the jam into the lands. I prefer as much bullet/neck contact as I can get.
I learned about the "free bore" thing a while back. Started off with an "off the shelf" 6BR barrel. Found out in short order that long free bore goes away real fast and that "sweet spot" you liked was a thing of the past. From there, ZERO free bore from the start. Seat my bullets where "I" want them and go heavier as the throat wears.

I'll add, I bench shoot "only" with my bolt guns so I know what to expect if I pull a loaded round and dump the action full of powder.
Gas guns? The term "A Mad Minute" comes to mind. Want a little "recoil"? Bring out the M1A and burn off a 100 or so rounds. That'll get your attention.
May not be able to raise your arm for a day or two but damn it's fun.

 

[mike a]

I’m starting to think less is better. Neck tension is a lot easier to control when you don’t have to push that bullet way in. With a really straight sizing die and a Wilson seater you can get that bullet in really straight. If the bullet were in straight just enough to not let powder spill out would it matter?

 

[Ned Ludd]

The standard I've always seen tossed about on shooting forums is that you'd like to have at least 1/2 caliber of bearing surface in the neck. I recently had a couple rifles re-barreled with a reamer that cuts 0.220" freebore. My idea when I had the reamer designed was to make the freebore as long as I could, yet still seat the 200.20Xs without jeopardizing the possibility that they would still shoot well. This would also allow loading some of the heavier (longer) .308 bullets more optimally; i.e. without having them seated so far down in the case. I used some QuickLoad data and made a few dummy rounds to come up with the 0.220" freebore, which leaves ~0.125" bullet shank in the neck with the 200.20X. So far, they are shooting just fine.

It's worth re-iterating DirtySteve's observation about the Uni-Throater, and how easily they cut. When extending the freebore using such a tool, it's important to remember that it is only cutting a very tiny thickness of metal from the bore/lands/grooves. It takes very little effort to remove such a small amount of metal, and so great care is required when using the Uni-Throater so as not to cut much deeper than intended. The tool does a great job, but a very conservative approach is warranted...so make the cut in very small increments and measure often.

 

[XTR]

I’ve moved the freebore in a lot of chambers with my Unithroater(s). Usually go in .005 [one line] at a time till I’m certain that I know where I am, then maybe jump in .010 to .015 between measurements. Only ever overshot one, and I was rushing because the faMiley had come home in the middle of what I was doing. Take your time.

 

[Field_2_Fork]

I have gone as small as 0.060" of the bearing surface in the case. You really do need to handle your ammunition pretty carefully though, with this little bearing length in the case. Often the chambering reamer will cut an extra 0.025" of neck in your chamber over the normal maximum length of you case. You could let the case grow in length a little to get a little more hold on your bullet. If you went down this route, it would be a good idea to drill out the primer pocket of one of your fired cases and put your bore scope through the case to see how much clearance between the end of the case neck and the end of the chamber neck there is.

Can you not get the same look by inserting the Teslong from the muzzle end? That's what I do. Maybe I'm missing something.

 

[Field_2_Fork]

I will give this a try. I have a Teslong.

Would inserting the Teslong from the muzzle not give the same view? I don't see the need and hassle to cut up a case.

 

[PhilKeil]

Steve
on my 338 i have about .150 in the case not counting the boat tail. it is shooting very well. no issue and i do single load.