high velocity with cast.

[btroj]

I have to try it? What?

I will await the return PM and go from there. I do wat to try some Dacron, just need to find time. I have another major project arriving next week and I think shooting will be a bit on the back burner for a bit.

And yes, RE19 does seem just a shade too slow. I need to find some RE17, if I can. The bit of RE15 I have left will also get some shooting time.

[detox]

Both Varget and V140 do verywell at velocities above 2000fps using the NOE 30XCB 165gr bullet. 35grs of both powders averaged 2200fps. 40grs of both powders averaged 2500fps. Gun is a Remington VS chambered in 308 Winchester. Linotype bullets were sized .311 and jammed into rifling when chambered. All bullets hand dipped in Lee Alox.


4895 and 335 did not do very well above 2000fps

Here is my best group @100yards. Both Varget and V140 averaged under 1.25" for all shots. I will test these rounds again and post pictures of 10 shot groups all together

[detox]

Here is one more picture

[geargnasher]

Detox, that's excellent! I'd love to see a chamber cast of your rifle to see how the bullet nose and chamber mate. I have a similar rifle and it has .100 freebore followed by a 3-degree-per-side leade into the lands, and I have been meaning to try the straight-taper of the AM 31-190X in it to see if the mis-match improves things vs. the matched, straight taper of the XCB which didn't work so well. Based on your results above, it just might work and now I'm more encouraged to try the 190X in my .308. I'm thinking at HV there needs to be a little bit of mismatch to the angles to allow a little slack for things to center on their own, rather than force them in there from a dead-nutz, full-contact fit which can never really be made perfect just by closing the bolt.

I'm having good luck at HV using a bullet with a couple of different tapers to the nose which allows a good "self-alignment" in a variety of chambers, it's a 45 2.1-designed bullet and he has explained how it works. It works particularly well in straight-taper or worn throats with little freebore, kind of the opposite of what I think you're doing with the straight-taper bullet and freebore+sharp taper throat if your throat is cut like I suspect.

You're going to prove a bunch of us wrong about straight linotype shooting straight at HV, aren't you? Good for you for showing there's more than one way to go about this.

Gear

[detox]

Here is chamber pound cast. The factory 308 NATO on left has .150 length free bore and .3118 diameter. The cast on right is my new Minimum SAMMI 308 with .090 free bore and .310 diameter. The NOE 30XCB Bullet prefers the larger 308 NATO with longer .150 leade and worn tapered throat (Remington VS).

The longer .150 free bore or leade and gentle throat taper is what helps guide the bullet strait. Bullets are sized .3115 to fit snug in free bore.

I will shoot for 2600-2700fps next time out

[leftiye]

I would not go to the trouble to control that one variable. There are many variables that effect neck tension. Brass wall thickness, bullet diameter, internal neck brass roughness, sized neck diameter, bullet straightness, brass hardness.... To me it is easier to control the easy to control factors and use bullet seating feel to screen out the bad actors.

Tim

One could, and many would, control all of those factors. It is the way we pursue accuracy. Pull being one of the harder factors to measure, only thumb tight seating will remove its effect.

[Bullshop Junior]

http://home.comcast.net/~jesse99/tension.html

[leftiye]

Here is a thought. It may exist, and I may not have seen it, but I am gonna flap my thumbs anyway.

I have seen several post, mostly from r5r about feeling how much pressure it takes to seat the bullet, and separating them by lot on how the bullet seats.

What if we add a pressure gauge to the seating die to regulate how much pressure it used. You could defiantly be more accurate with a gauge then my feel I would think.

Or what if we ran an expander ball (that didn't expand the brass, or very little) through each case and had an electronic pull type scale (a recording type scale so we don't have troubles reading a spring type scale) attached to the press handle? I am thinking this would do it.

P.S. I hadn't seen your above reference (post 90) yet when I typed this.

[Bullshop Junior]

There are lots of ways it could be done. I don't know if it is worth the effort, although I had never even though of case neck tension being a factor in accuracy before.

[geargnasher]

Detox, thank you for the pic and explanation. Looks like the leade tapers are mismatched by well over 1.5 degrees per side, and longer freebore helps. Mismatching the tapers helps make the swaging less sudden. Have you hardness-tested your linotype? Hope you don't mind all the questions, I'm just really interested in dissecting all the fine details of how you got a NATO chamber, in I'm assuming ten-inch twist rate, to shoot 2500 fps with just over MOA accuracy, because that's REALLY tough to do and a couple of us have done it at 2400 fps, I'd like to see what we did differently and what we did the same.

I'm assuming you have the 26" Varmint-contour, 1-in-10" barrel on your VS?

Gear

[leftiye]

Detox, that's excellent! I'd love to see a chamber cast of your rifle to see how the bullet nose and chamber mate. I have a similar rifle and it has .100 freebore followed by a 3-degree-per-side leade into the lands, and I have been meaning to try the straight-taper of the AM 31-190X in it to see if the mis-match improves things vs. the matched, straight taper of the XCB which didn't work so well. Based on your results above, it just might work and now I'm more encouraged to try the 190X in my .308. I'm thinking at HV there needs to be a little bit of mismatch to the angles to allow a little slack for things to center on their own, rather than force them in there from a dead-nutz, full-contact fit which can never really be made perfect just by closing the bolt.

I'm having good luck at HV using a bullet with a couple of different tapers to the nose which allows a good "self-alignment" in a variety of chambers, it's a 45 2.1-designed bullet and he has explained how it works. It works particularly well in straight-taper or worn throats with little freebore, kind of the opposite of what I think you're doing with the straight-taper bullet and freebore+sharp taper throat if your throat is cut like I suspect.

You're going to prove a bunch of us wrong about straight linotype shooting straight at HV, aren't you? Good for you for showing there's more than one way to go about this. Gear

Gear, it might also be about the lower impact of the smaller contact area of the mismatched angles. It might engrave a small area enough to guide the rest while engraving, whereas a total fit might not engrave before sliding one way or another. Deformation?

[dtknowles]

One could, and many would, control all of those factors. It is the way we pursue accuracy. Pull being one of the harder factors to measure, only thumb tight seating will remove its effect.

I work to minimize the variation in all those factors in pursuit of accuracy but personally testing the hardness of my brass is not something I am getting into. I have tried to track down why some bullets require more or less force to seat than others. One factor was not getting the bullet started quite straight, gladly I will reject those rounds. Another was thin case necks. After just one cycle all those cases are now segregated.

I believe that if it take more or less force to seat the bullet then the force to pull the bullet will vary in an unacceptable manner.

I have loaded and tested ammo with almost no neck tension (thumb seating) I loaded these with long overall length so the bullets would hit the lands and be pushed back into the neck. I would not call this jam because the contact force is very small. This worked ok, not magic, groups much like others for good loads in this rifle.

Tim

[geargnasher]

Getting and keeping the bullet absolutely straight as it goes into the barrel seems to be the principle obstacle to HV accuracy when all the other factors are ironed out. It's very difficult to do what Runfiverun and Detox are doing with their .308s where there is more or less dependence on pre-aligning the bullet straight in the throat and lots of room (I assume) around the case neck for the base of the bullet to wiggle/bend/rivet etc. yet the nose is presumably tough enough and tight enough to be held straight. They are doing it, though, or the groups would be more like 5-6" or worse. The proof of a straight bullet start (and finish) is in the group sizes they're getting.

Gear

[RickinTN]

Gear, and others.
I have limited experience on the matter but so far I think I agree with you on the mis-matched taper of the bullet nose. It seems it would be easier on the transition from static to dynamic fit and engrave gradually instead of all at once thus somewhat relieving the tendency of the bullet to compress. My question would be....Is it better to have the nose of the bullet engrave from the front of the nose back? or form the back of the nose forward? I think I know that ideally a bore-ride bullet engraves the leade slightly at the very front of the bore-ride section and serves to align the bullet. In a situation of engraving from the back of the nose forward this alignment would be sacrificed at least in static state and alignment to the bore would have to rely on other areas. The issue I see with engraving from the back of the nose forward is that the nose of the bullet, at least part of it, is temporarily unsupported until complete engraving is accomplished. I hope my question makes sense. Any thoughts?
Thanks,
Rick

[Bjornb]

Detox, thank you for the pic and explanation. Looks like the leade tapers are mismatched by well over 1.5 degrees per side, and longer freebore helps. Mismatching the tapers helps make the swaging less sudden. Have you hardness-tested your linotype? Hope you don't mind all the questions, I'm just really interested in dissecting all the fine details of how you got a NATO chamber, in I'm assuming ten-inch twist rate, to shoot 2500 fps with just over MOA accuracy, because that's REALLY tough to do and a couple of us have done it at 2400 fps, I'd like to see what we did differently and what we did the same.

I'm assuming you have the 26" Varmint-contour, 1-in-10" barrel on your VS?

Gear

Gear,
over on the test thread Detox mentioned that his 308 had a 1:12 twist.

[geargnasher]

Gear, and others.
I have limited experience on the matter but so far I think I agree with you on the mis-matched taper of the bullet nose. It seems it would be easier on the transition from static to dynamic fit and engrave gradually instead of all at once thus somewhat relieving the tendency of the bullet to compress. My question would be....Is it better to have the nose of the bullet engrave from the front of the nose back? or form the back of the nose forward? I think I know that ideally a bore-ride bullet engraves the leade slightly at the very front of the bore-ride section and serves to align the bullet. In a situation of engraving from the back of the nose forward this alignment would be sacrificed at least in static state and alignment to the bore would have to rely on other areas. The issue I see with engraving from the back of the nose forward is that the nose of the bullet, at least part of it, is temporarily unsupported until complete engraving is accomplished. I hope my question makes sense. Any thoughts?
Thanks,
Rick

That's the million-dollar question, isn't it? I've had the best results so far using bullets that are a shallower taper than the leade angle, for what it's worth.

You can "engrave" the nose all you want, but those little lands aren't going to continue to support it straight without sinking in to one side of the nose if the bullet base is jammed crooked from the back just as soon as the powder lights. Harder, way harder bullets seem to be needed for getting good groups at even just above the typical we've seen. The bore-rider concept just doesn't seem to work out very well at extremely HV from what I've seen.

Gear

[btroj]

I think excessive land contact is bad. I want enough to keep the bullet aligned at ignition but I want the bullet to be able to easily engrave the rifling. I want bullet movement early in the ignition so it is engraving before pressure rises too much. A tapered nose allows the engraving to be not only gradual but to also increase in length of contact. Move the bullet 1/4 inch and it is engraved well and still centered.

Im no expert but I think this is part of why the 30 Sil shoots well at higher velocity.

[geargnasher]

Gear,
over on the test thread Detox mentioned that his 308 had a 1:12 twist.

Right. I was going off of some internet misinformation. Remington states 1:12 for #84345 and 26" (probably fluted) barrel for the .308 model.

Gear

[btroj]

Internet misinformation? Say it isnt so!

Those are some very nice groups for 2200 fps.

[dtknowles]

I am sure I missed something quite a while back but bare with me. How come all this discussion is about long nose bullets with only a single or maybe two grooves? What is the reason for not using Loverin style bullets or Pope style. I am working on high velocity with gas checks and also 2000 fps with plain base. I am following this because a lot of the same details apply to both but I don't understand why to use a long nose short shank bullet. As an aside, why isn't the neck longer on the 30XCB?

Tim