First: If I had the guy that made it POSSIBLE for me to strike two keys at the speed of light, and errase an entire half an hour's work of posting in a flash, I'd choke the .... I don't know how, or what I do it ... but I did it again. Blink, flash, gone. Ah, nutz. Moving along. Let's do this all over again.

I thought I might do a high speed video for you, in the shop this morning. It didn't work. Not nearly enough light. I'll work on that.

I decided to, instead; continue with the research into Spitzer bullets for the 7.62 mm project, before I started machining. I wanted to have something to show you. I got some interesting results.



I started by shooting the 126.18 grain boat-tail Spitzer @ 833 fps for 194.46 fpe.



I pressed the Clay Gopher into service. After being locked up in the War Wagon for months of bad weather, he was (once again) eager to help.



Here's the entry of the second test velocity ... but they were the same.



The 833 velocity was just correct to completely penetrate the clay, and be caught while exiting! Yeah.



And look how this long pointed slug piled up. Wow.



It went from nearly an inch long to just about 3/8 of an inch in length.



And the expansion was amazing. From .313" to .564" (that's 56 caliber!)



I decided to wind it up a bit more ... and shot the same slug @ 867 fps for 210.66 fpe. (Heavier slugs will still make more - I've run the spitzers to 255 or so), but I was interested in velocity reaction of the smaller slug in this testing.



This slug expanded, turned, exited, and was lost in the depths of the bullet trap.

Better post before the dread mystery key shows up again!

Yeah! It worked.

The Gopher will be fine. It was just a flesh wound!

Gary



Edited 2 time(s). Last edit at 03/12/2010 09:12PM by barnespneumatic.

That is a good classic mushrooming of the slug. Great expansion and still has a good bullet shank for deep penetration. Great work Gary!

Thanks Peter.

It's great to see that at least one guy retains the ability to type!

Gary

OK, thats pretty awesome for sure. Spitzer bullet must retain a lot of velocity downrange.

ALSO, GB, do you use some type of MICRO GROOVE rifling in your barrels? All those rifling marks on the slug reminds me of a projectile shot out of a MARLIN rifle. NICE.

Hi Cedric,

That's 18 groove rifling, with each land having two knives on it for cutting the rifling. Lots of control over the slug.



Gary

Now that is VERY intesting Gary.... I shot a spitzer or two (.308) into wet phone books at 100 yards and they went straight through...I guess you never know until you actually put them into the real thing. I happen to like spitzers a lot (they look like real bullets) so I will keep testing them....

Cheers
Neil

Hi Neil,

Were they stable for you? If they are very long, you have to have a faster rifling twist.

Gary

Hi Gary

They shoot pretty well at 100 yards, though they seem to hit the target a little askew in some cases:

I thought that the driving bands for these spitzers were too far back, leaving the nose end to flop around in the bore, but when I did the swimming pool test I found the slighty bulbous "upper body" engaged the rifling quite well:

I shot 1 goat with these but poor shot placement meant I needed a follow-up shot. They will be deadly killers with head, neck or spinal shots I imagine, but if you want bleeding from chest shots (as I understand hunters do) these will likely make too clean a pass through for that.

Cheers
Neil

Interesting - thanks for the pics Neil.

Those are almost "Round Nose" compared to how streamlined and needle nosed my Spitzers are. Must make a difference in the "pile up". That's also an enormous amount of bearing surface to engrave. Accuracy and velocity are the tests though. If they work, they work. If your dear old white haired granny made the mold for you ... then it's perfect!

If you bought it, then the length of the slug, in ration to the bore, is most likely long for your twist rate. That's giving you the wobble to the slugs as seen in the holes.

Have you tried sizing them down smaller? The grooves in the lead indicate that you have way more than you need to spin them. You can't get them to spin any faster, but you can get them there perhaps faster (before more wobble sets in). It's all in the magic of breech pressure, rifling resistance.

Gary

I really need a swimming pool for testing slugs ...

Yeah Gary, a pool. That's EXACTLY what you need.

Having grown up as an unpaid slave to a swimming pool, I can categorically say that only women are higher maintence.

What you really need is a friendly neighbor with a pool. Of course, it would have to be a VERY understanding neighbor if every time you showed up to swim, you were toting along a rifle.

That is one tough critter!

The concept of "friendly neighbor" is an Oxy-Moroon.

Gary

Gary I might try sizing them down, though I think Jerry has observed that these guns like to shoot slightly oversized slugs...
I'll see if my pal has a smaller sizing die.
Regards
Neil

Yes - but the size is relative to the design of the slug. You have a mile of bearing surface on that slug. Totally different from if you were shooting a "ringed" slug, or a ball. Your slug, a ball, and a slug like mine .... would all three need to be different sizes in that barrel.

Gary

I agree, the slugs we've made and that were used in that gun and showed a preference for over-size, were 113-115gr round nose and flat tip slugs. Every single user who shot the exactly .308 slugs and also the .310 slugs reported that the .310s were far more accurate despite the bore being exactly .308 across the grooves according to the manufacturer. Now, those slugs ahve similar lengths from base to full diameter and the barrels do have ledes cut in them. It is unknown to me if the slug length vs. lede cut is the predominant factor or if the diameter of the slugs and how tightly it fit the bore was the deciding factor. All I know is that for those 2 slugs, .310 is a far better choice than the manufacturer recommended .308 commercial slugs. The customers who came to me did not do so because they were delighted with the performance of the cheaper Hunters Supply recommended slugs! They also did not have any hesitation in describing that our slugs at .308 were not good enough! I sent them some .310 slugs and got back raves about better accuracy along with money transfers to buy more slugs just like the ones I had sent! Opinion backed up with cash is pretty convincing in my book!

All that said, any other design, including the other heavier designs for that barrel remain at least a bit undetermined regarding best diameter. My thoughts are that it is more difficult to get a spitzer design accurate in an airgun because the opportunity to get it loaded past the lede crooked is greater.

Another issue regarding size, will be the hardness of the alloy. Commercial box slugs are generally made for firearms, and use a much harder lead. They can be shot a bit smaller (less lead engraved). The soft cast slugs can ride deeper in the rifling - even bore scrounge - and work very well. Could be a factor - I don't know.

The chambers of barrels can be cut different ways. Tapered or abrupt.

Any Spitzer is going to be long, per it's weight, per caliber. It's going to need a faster twist. You can shoot the same weight, in a short stocky slug, and not need the fast twist. But, the BC of the slug will not be nearly as good.

Gary

Boy Gary, that soft lead really piles up! Now, before we equate that gopher with the real thing, we should remember that the electrical putty is denser than tissue. I'd bet that 4in of putty is equal to a broadside of a whitetail chest. Heck, you did find that first slug just under the skin on the far side of gopher! We've both seen that before.

Do these results have any relation to the Splatology data you described years ago, or is that strictly ground ball and steel target?

Neil, good shooting! I'd bet that slug doesn't even check up as it passes thru a goat sideways! You're right about liking to have a good blood trail after a shot. It's surprising how far an adrenaline pumped animal can travel in even a few seconds with a perfect hit. Of course, a lot of the action occurs just before dusk meaning the tracking happens in the dark with a flashlight. Tough, unless you have Gary "Willow Blossom" tracking beside you.

Thanks for the peak into the testing!

Kent

"Thank yah' Clark"



But shucks ... anybody would trip over a drop of blood on the underside of a leaf, in the dark ...

Gary

Hehe, well thanks guys, I have taken on board all views and will duly do a shoot-off between .308 sized spitzers, and my current sizing, which is about .3095 I think. I will test at 100 yards and chrony for speed. As long as the weather co-operates, which we all know is a lottery these days
Regards
Neil

Hi Neil,

I'll make a bet. Now, IF you use that exact slug ... those rifling marks indicate that you will have just as much control at .308 as you do at .3095".

The question of velocity isn't as easy. Since the slug is heavy per caliber, it's already providing a natural resistance to building breech pressure. The rest of the resistance to initially moving down the bore, is being provided by the sizing (resistance to being cut by the rifling). IF the slug were lighter, (and you'd size it smaller) I think there could be a danger of the slug moving down the bore with the first breath of air. Because it would move before breech pressure rose very much at all. And, though the slug were smaller in diameter, you'd actually loose velocity. HOWEVER: Here's my guess ...

You'll have enough back pressure still (because of slug weight and rifling resistance) ... and you'll actually pick up velocity. You'll have plenty of accuracy retained (because you are over-cutting the slug now). And, you might have just a bit less wobble @ 100 yds. - because the slug will get there a bit faster (before as much wobble has set in). Remember - you can't spin it faster with velocity ... you can just get it there faster with velocity.

That's my bet. Let me know. If I'm right on everything ... let's see ... what do I get? Maybe I can tag along on a goat hunt on my next trip to New Zealand. haha.

Gary

barnespneumatic Wrote:
-------------------------------------------------------
> Hi Neil,
>
> I'll make a bet. Now, IF you use that exact slug
> ... those rifling marks indicate that you will
> have just as much control at .308 as you do at
> .3095".
>
> The question of velocity isn't as easy. Since the
> slug is heavy per caliber, it's already providing
> a natural resistance to building breech pressure.
> The rest of the resistance to initially moving
> down the bore, is being provided by the sizing
> (resistance to being cut by the rifling). IF the
> slug were lighter, (and you'd size it smaller) I
> think there could be a danger of the slug moving
> down the bore with the first breath of air.
> Because it would move before breech pressure rose
> very much at all. And, though the slug were
> smaller in diameter, you'd actually loose
> velocity. HOWEVER: Here's my guess ...
>
> You'll have enough back pressure still (because of
> slug weight and rifling resistance) ... and you'll
> actually pick up velocity. You'll have plenty of
> accuracy retained (because you are over-cutting
> the slug now). And, you might have just a bit
> less wobble @ 100 yds. - because the slug will get
> there a bit faster (before as much wobble has set
> in). Remember - you can't spin it faster with
> velocity ... you can just get it there faster with
> velocity.
>
> That's my bet. Let me know. If I'm right on
> everything ... let's see ... what do I get? Maybe
> I can tag along on a goat hunt on my next trip to
> New Zealand. haha.
>
> Gary
Hehe, Gary, the bet is on!! You win, you get the goat hunt. I win, I get a guided tour of your workshop and one of Kelly's special breakfasts....
I'll use exactly the same spitzer sized down to .308.
I'm looking forward to this, but I can't help but think there is a good deal of logic in what you say (particularly given that previous sizing down reservations centred around short slugs) and that I may well lose this particular bet
I will report in in due course
Regards
Neil

Good luck!

Gary

How do I win plane fare to New Zealand?

That is very interesting Gary! I've never had someone exlpained so clearly how the bullet react in the airgun's bore like that before. Good stuff for learning.

I'm having trouble wrapping my head around "Remember - you can't spin it faster with velocity ... you can just get it there faster with velocity. " Does this mean that bullet stabilization is a matter solely of rate of twist and independent of velocity. Seems that the gyroscopic stabilization would be greater at greater velocity exactly because the bullet is spinning faster as well as traveling faster...?

Jerry, I know they're not spritzers but the 25s you are making for the Condor's is a very long slug in the heavies. What's your feed back on key holing with those barrels that are twisted for much shorter commercial pellets?

Kent

Hi Kent,

This is such an interesting issue, and so universally misunderstood ... I'm going to start a new thread. Thanks for picking it up. I wondered if someone would.

Oh ... BTW ... got the injections this am. It went well. I'm supposed to take it easy today. Just going to dig a 100 yard ditch, bury a 24" diameter pipe ... make an underground range ... ... (yes - I'm kidding)

Gary