design and alloy

[Ian]

Ian, have you tried any with pc? In all my playing, the pc completely eliminated any leading and took that issue out of the consideration.

I have played with it a bunch, below 1050 fps. The only loads I've shot at full J velocities are 200 Lees in my .35 Remington, with gas checks and with/without lube in the grooves. I got better external numbers with lube, so that's what I went with. I used PC because I wanted a relatively soft hunting bullet for Red Deer (10.5 bhn 50/50 air cooled alloy) and still wanted to push 2200 fps. I'm going to do a lot more HV work with PC in the future.

 

[VZerone]

Here's one to think about Ian. When Joe had that 6.5 Grendel AR 15 (he regrets selling it too!) he sat and studied cast bullets for it. He wasn't going to own a rifle he couldn't shoot with cast. He came upon the SAECO 140 grain 6.5 bullet, the one that Rick use to have as an avata???, and said it looked like it was designed for that cartridge/chamber. The problemw as freebore, or lack of it. That SAECO is a bore rider and the 6.5 Grendel has a short neck, so the base was just a tad long and some of the full bearing ban on the front had to be exposed into the throat. Well that was exactly about 1/16th of an inch. The nose resided in the bore. The nose was a "snug" fit in the bore. To top it off the OAl had to match the magazine requirements. All of it did. Now here he was shooting a plain Jane bore rider with fantastic groups to the mid 2000's. There were no tricks or hokus pokus, no buffer. He didn't even do a pound cast on that throat. Before he committed to buy the SAECO mould he took some of 45 2.1's 6.5 Kurtz bullets which he had the mould for and sized the nose down enough to get the bullet to work like mentioned above for the SAECO bullet. The testing of that was very lack luster, he stepped out of the back door of his shot and aimed at a letter on the no trespassing sign in his yard over 50 yards away and shot five shots standing BANG BANG BANG BANG BANG and it was a 3/4 inch group. My mouth dropped as for one he's no standing up rifle shooter by anymeans and for a modified basically Loverin style 6.5 Kurtz to shoot that well was something to me. Why he never persued that modified 6.5 Kurtz further then that day I don't know. He bought the SAECO 6.5. Still has that mould, but guess what? It won't shoot at all in any of his other 6.5 cailber rifles. The alloy by the way was 50/50 both AC'ed and WQ'ed.

 

[Rick]

A record, only took 43 posts for thread drift.

Yes, the bullets in my avatar are the SAECO 6.5 140.

I bought that SAECO 4 cav for my 6.5 BR with a Shilen match chamber/barrel. The front driving band was too long for the chamber and the bullet had to be seated really deep. I was nose first sized just the front edge of the front driving band in a SAECO sizer die to fit into the chamber further and it worked ok. The RCBS 6.5 140 gr. is fairly close to the same bullet except shorter driving bands and it outshot the SAECO in this gun. Both bullets were CWW +2% Sn heat treated to 18 BHN.

Left: SAECO, nose diameter .2566" Bullet length 1.112"
Right: RCBS, nose diameter .2561" bullet length 1.070"
(Nose Measurements an average of several bullets)



Back to your regularly scheduled discussions.

 

[Ian]

It seems the biggest question is still how do we know what bullet shape to select, what alloy to use when, and what powder to use.

I can affirm that there are multiple ways to do this. Fiver and I both got about 1 MOA @2400 fps out of 10-twist, 20" barreled, .308s, with similar throats....He used (IIRC) 94-6-2 alloy and a two-diameter, AM31-165A bullet cast carefully and sized carefully to snuggle the lands and scuff the throat freebore, and I don't remember the powder. I used water-quenched, aged 97-2-1 alloy and the two-taper, MP 30-silhouette bullet seated off the lands about .015", sized .310" to fit the throat entrance, and H-414 powder. Two completely different ways of getting "there", but we both got to the same place. I had to cheat on the last 150 fps and use buffer and thick-necked brass to hold MOA, he did not. I think I could have gotten away without buffer or custom brass if I'd dropped back to 4831 or something along those lines, but I was happy where I was at and moved on to other projects.

 

[VZerone]

Ian I've used from fast powder (4198) to slow powder (RL22 and surplus) to achieve HV with good accuracy. This was from 2400 fps up to 3100 fps. Mostly with the 30 Sil bullet. I won't necessarily say you have to use a slow powder to shoot HV cast. Let's just say it's easier!

 

[fiver]

I used 4831-sc and a filler along the way.

I think the best way to choose an alloy and design is to base it on your throat shape.
had I tried what I did with the 165 the same way I approached the rcbs 165 silhouette I think I would have failed pretty,,, well maybe not miserably, but it sure would have taken me a lot longer to get there.
I wasn't going to get there for sure with that long bore rider.

 

[VZerone]

Ian, since 45 2.1 is having trouble trying to post on this forum, he wanted me to tell you that you are wrong about him designing the 30 Sil strictly for bolt action rifles. He said to tell you he's beeing shooting 30 caliber semi-auto rifles since 83. I knew this, but it was his place to tell you.

 

[bns454]

After reading these 40 some posts I realize I dont understand alot of what I thought I was learning in the past 2 tears.Can I ask some basic beginner type questions here,or start a new thread.

 

[Brad]

Ask away.
If you feel it deserves a separate thread then you certainly can begin one.
Sharing info is what we are about, it is how we learn.

 

[fiver]

yep ask that's what this thread was started for.

 

[Rick]

I see no problem, sharing info and asking questions is the purpose of the forum. Please feel free to ask away. And remember the very most experienced here was once brand new and still has much to learn.

 

[fiver]

<<< aand still has much to learn.

 

[bns454]

Ok,Thanks. When you talk about the nose of a bullet engraving.I picture it as say the last 30% or the tip.Your pictures show the engraving in the middle of the bullet.Is everything the sits out of the case the nose ?No matter what I cant make my nose to engrave in my definition of nose.

 

[Brad]

I learned more in the last 5 years of casting than I did in the previous 25 years.

Much of that was from people here. Rick, Ben, fiver, and Ian all pushed me to become more.

 

[Brad]

Ok,Thanks. When you talk about the nose of a bullet engraving.I picture it as say the last 30% or the tip.Your pictures show the engraving in the middle of the bullet.Is everything the sits out of the case the nose ?No matter what I cant make my nose to engrave in my definition of nose.

I view the nose of a cast bullet to be anything forward of the full diameter section.

 

[fiver]

on a 2 diameter rifle bullet everything in front of the front drive band is the nose.
for something like a rnfp bullet for a lever gun everything in front of the case is the nose.
on something like the XCB the nose is somewhat hard to define, but pretty much ahead of the top lube groove would be referred to as the nose.

 

[bns454]

Ok,that helps.I understand what riveting is,but is it caused by too much neck clearance or too much engraving on a nose at the start of ignition.

 

[Rick]

Or too much pressure for the alloy. When the pressure starts to rise the bullet base tries to move first, if the nose can't get going the base can rivet. Just one example.

 

[Brad]

Both.
It isn't just neck clearance, it is also an overly large throat, empty at the end of the neck because the chamber was cut too long in that area. Riveting can occur into any space the bullet finds.
It also can occur with no engraving at ignition. The bullet still needs time and energy to engrave the rifling. A bullet with a large initial contact means more effort is required to engrave. A bullet with a more gradual contact with the rifling means the energy and time is spread out and less riveting may occur.

 

[fiver]

both can cause it.
if you have the nose pressed against the rifling and whack it with pressure the bullet pushes forward while being held in place at the same time.

don't be confused by thinking you don't want engraving on the nose you absolutely want the nose to be engraved.
evenly and firmly by all the rifling.