Velocity threshold for cast rifle boolits.

[DanWalker]

WOW! Reading some of these responses is like playing scrabble with Stephen Hawking! Just lets me know mow much I DON'T know.

[Browningshooter]

This really should be stickied!!

As someone who has learned a tremendous amount through the stickies on this forum I think it's worthy. This is more advanced info than what a newbie really needs but it. Is very useful info for those diving deeper into the mechanics and forces at play on our beloved projectiles. To all who have contributed to this thread I say... Thank you

[MBTcustom]

Well, all that has been stated is theories and laying the ground work. I want to see a thread where there is some seriouse experimentation and pictures. I would love to have a shooting lab, a high speed camera, and a borescope.
Ten shots with a setup like that would teach amazing things.

[shredder]

Well, all that has been stated is theories and laying the ground work. I want to see a thread where there is some seriouse experimentation and pictures. I would love to have a shooting lab, a high speed camera, and a borescope.
Ten shots with a setup like that would teach amazing things.

The fun part of all this is that in those microseconds during firing a lot is happening that we will never see or even perhaps truly understand. It's what keeps the interest up!

Cause or effect? Hard to be absolutely sure isn't it?

[DanWalker]

Well, all that has been stated is theories and laying the ground work. I want to see a thread where there is some seriouse experimentation and pictures. I would love to have a shooting lab, a high speed camera, and a borescope.
Ten shots with a setup like that would teach amazing things.

I'm thinking this would make a TREMENDOUS masters thesis project for some engineering student.

[Dutch4122]

As the muzzle exit pressure increases, the quality of the crown and CB must increase to maintain accuracy. The magnitude of the pressure is irrelevant.

Sorry, but I'm not buying that statement popper. I have seen drastic improvement in groups when changing only one component at high velocity; that is going to a faster burning powder. And I'm not talking about just one or two rifles here. The biggest improvement I've seen was with a 1927 Ishevesk Mosin Nagant. Switching from IMR-7828 to IMR-4350 resulted in groups shrinking from 20" groups nearly 2' high at 100 yards to 4" groups printing 8" high at 100 yards. Target velocity with both loads was 2,600 fps and the same 180 grn boolit was used in both loadings as well as same primer, brass, etc.

Now, here's where the muzzle pressure does matter. I'll use the two loads above as an example. The slower burning powder (IMR-7828) was generating muzzle pressures near 10,000 psi while the faster burning powder (IMR-4350) was generating muzzle pressures of approximately 7,500 psi.

When you're working near the limit of what your alloy can withstand pressure wise I believe that 2,500 - 3,000 psi of muzzle pressure translates to a big difference in accuracy.

[357maximum]

Sorry, but I'm not buying that statement popper. I have seen drastic improvement in groups when changing only one component at high velocity; that is going to a faster burning powder. And I'm not talking about just one or two rifles here. The biggest improvement I've seen was with a 1927 Ishevesk Mosin Nagant. Switching from IMR-7828 to IMR-4350 resulted in groups shrinking from 20" groups nearly 2' high at 100 yards to 4" groups printing 8" high at 100 yards. Target velocity with both loads was 2,600 fps and the same 180 grn boolit was used in both loadings as well as same primer, brass, etc.

Now, here's where the muzzle pressure does matter. I'll use the two loads above as an example. The slower burning powder (IMR-7828) was generating muzzle pressures near 10,000 psi while the faster burning powder (IMR-4350) was generating muzzle pressures of approximately 7,500 psi.

When you're working near the limit of what your alloy can withstand pressure wise I believe that 2,500 - 3,000 psi of muzzle pressure translates to a big difference in accuracy.

May not have asked for it....but your gonna get a big ol A.M.E.N and a X2 anyway.

Somethings just are...they do not require that you believe. The proof as always is on the chrony and the target paper. Your noisy maggot loadings along with my 91 argentine debacle are just a few times out of many that this has been proven out.

[35 shooter]

All the different theories i've read here and other places over the years keep me going back to the range,which
is a good thing,but it keeps me from sleeping which is a bad thing.
All i can say after trying to push boolits fast and keep minute of angle accurracy at 100 yards for over a year now,
the best i have come up with in a 1 in 14 twist 35 whelen with a 200 grain rcbs gcfn heat treated at 460 to 475 degrees and water dropped with powders ranging from 4759, 3031 to h4895 is 1800, 2000, 2200 2400 and 2500fps.
I have pushed to 2600 but really good accurracy stopped after the 2500fps load. Might try 4064 but looking at case capacity i think i'll run out before beating the rpm threshold with any kind of accurracy.
Larry Gibsons chart predicted speeds under 2333fps to2722fps.
I saw the chart after i had worked my loads up and i'm just saying it surprised me how close it worked out.
BTW my alloy is just ww. I'm know changes in alloy can make a difference too. Anyway looks like i've run ww as far
as i can in MY rifle. I'll probably be hunting with 1800 to 2200fps anyway but it's good to know an old lead boolit
can go a lot faster if you need it too. Gotta do some expansion tests next, cause accorrding to what i'm reading
on these forums ww won't hold together at high speeds on game anyway?

Keep the education coming guys, i'm trying to absorb it all. It's good to be 60 and learning new things.

[357maximum]

35

If you are after deer the 2300 to 2500 fps loads are more than enough. I had to alloy and waterdrop lead/ww/babbit to get over that hurdle of 2500fps @MOA myself. Then I shot some deer with a 225@2700 fps.....far too much oomph for a poor little deer. If you mix your ww 50/50 with pure lead and then waterdrop straight from the mould you will have a great deer alloy for them 2200-2500 fps loads in your whelen. Sometimes we achieve more than we need.


BTW.......I like H414, H-hybrid100V @24-2500 fps in my whelen...a mauser custom with a 14 inch twist....plenty "kill" for a deer sized animal.

Mike

[nanuk]

I remember reading an fine article by a PH in Africa, and his many years experience has told him the 2400fps of the oldies was spot on. He felt an impact velocity between 2400 and about 2000fps makes for perfect bullet performance.


that gives you a range from whiskers to a couple hunnert?

I suspect a good alloy would perform much the same way, 'specially with a nice flat nose.

if I could get 2MOA at 2400fps with my whelans, I'd be set for all my hunting.

[LynC2]

This tread has been some very interesting reading with many excellent theories and ideas, including a lot of firsthand experience. I've just recently gotten back into shooting cast boolits in rifles in the last couple years after a very long hiatus from shooting NRA high power and Palma matches. In the past I never had much luck (read about 30 years ago) pushing cast beyond about 2000 fps, but think I may give that a try in my Palma rifle which has an Obermeyer 5R barrel with a 1x13 twist. It should be interesting to try at least. Now I need to see if I have a small sizing die for the tight bore it has.
One thing that was mentioned was the often times negative effect of muzzle pressure upon accuracy with certain rifles/loads. I wonder how having a barrel magna-ported would work upon reducing the high pressure? Not that I would be the one to try it, but just curious.

[357maximum]

I wonder how having a barrel magna-ported would work upon reducing the high pressure? Not that I would be the one to try it, but just curious.

Well one of the members of our Michigan crew is working on that right now, and your brainwaves were on the right track, just as his were. Theory seems to be panning out, but needs more work in order to call it "proof". I will not get in on them tests as I am not a fan of NED's.......Noise Enhancing Devices.

[geargnasher]

LynC2, 5R rifling and porting barrels are two things I would love to hear more about. I would think that porting simply to reduce muzzle pressure could be beneficial if done right, meaning a few, small holes more like gas piston ports than a muzzle brake. 5R rifling may prove significantly better (or worse) than conventional rifling with cast boolits, I'd like to find out either way.

Gear

[Dutch4122]

Well one of the members of our Michigan crew is working on that right now, and your brainwaves were on the right track, just as his were. Theory seems to be panning out, but needs more work in order to call it "proof". I will not get in on them tests as I am not a fan of NED's.......Noise Enhancing Devices.

I think the best way to test this theory is to get a short barreled rifle in the .308/30-06 class and shoot it with loads that develop too much muzzle pressure using a powder that is 1 step too fast and creates the classic "high & wild" groups. Then port the barrel ala Marlin Guide Gun or along the lines of Gearnasher's suggestion like gas piston ports. Shoot the same loads as before and see if the groups settle down as we have seen with faster burning powders in unported barrels.

[357maximum]

Hey Matt...iffin ya need help I know how to drill a hole completely through a barrel.....I am so good at it I can do it on accident. ......just figured I would beat one of yall to the punch.

[geargnasher]

I think the best way to test this theory is to get a short barreled rifle in the .308/30-06 class and shoot it with loads that develop too much muzzle pressure using a powder that is 1 step too fast and creates the classic "high & wild" groups. Then port the barrel ala Marlin Guide Gun or along the lines of Gearnasher's suggestion like gas piston ports. Shoot the same loads as before and see if the groups settle down as we have seen with faster burning powders in unported barrels.

For this purpose I am currently in the market for a sporterized Mosin Nagant M-44 carbine with a good bore. Something reasonably priced that won't cause too much wallet pain when it comes time to drill holes in the barrel.

OK, it just so happens that I have a brand-new Savage M-11 "Hog Hunter" in .308 Winchester. It has a 20" barrel with threaded muzzle. My plan is to build a light 7mm-08 on it using a Shilen pre-finished barrel and their .312"-necked reamer. That project is a way off yet and I don't have any special attachment to this particular barrel, so in the meantime I'm going to fool with it as-is and see about some subsonic loads as well as some real streakers. The chamber is atrocious, not expecting much accuracy past about 1800 fps with it, but we'll see what happens.

Gear

[LynC2]

Well one of the members of our Michigan crew is working on that right now, and your brainwaves were on the right track, just as his were. Theory seems to be panning out, but needs more work in order to call it "proof". I will not get in on them tests as I am not a fan of NED's.......Noise Enhancing Devices.

I agree with you about the "NED's", they can make life miserable shooting next to one!

Well, that's interesting about someone is already trying the porting. Keep us updated!

[Dutch4122]

OK, it just so happens that I have a brand-new Savage M-11 "Hog Hunter" in .308 Winchester. It has a 20" barrel with threaded muzzle. My plan is to build a light 7mm-08 on it using a Shilen pre-finished barrel and their .312"-necked reamer. That project is a way off yet and I don't have any special attachment to this particular barrel, so in the meantime I'm going to fool with it as-is and see about some subsonic loads as well as some real streakers. The chamber is atrocious, not expecting much accuracy past about 1800 fps with it, but we'll see what happens.
Gear

That sounds like a good plan. Does your rifle have a muzzle break screwed on the end? Just thinking out loud here. A muzzle break may not accomplish the same as ports in the barrel for our purposes. Also, I would try a bullet weight that will give higher muzzle pressures than the 210 grn slugs I have had success with. Probably a good idea to find a 180-190 grn slug that fits well and port the barrel itself.

Michael and I talked on the phone today briefly about this project. He has a sporterized 1891 Argentine Mauser that he shortened the barrel of a few years ago. At that time a load that had previously shot like gangbusters (with the longer barrel) was a real dog after a couple of inches was removed. I suggested at that time that he go to the next fastest burning powder he had; he did, and the accuracy he wanted came back. He has offered to provide this barrel for porting. The idea is that we will go back to the original load with the slower burning powder and see if the accuracy comes back once the barrel is ported.

Now if we can just find a "reasonably priced" self taught & semi-retired gunsmith to port the barrel?

[leftiye]

Y'all are throwing the food out and drinking the broth. Faster powders cause more deformation at ignition. That's why all of the hyper velocity accurate loads use slow powder. I totally see your point, that high muzzle pressures cause issues with accuracy. But, it's been probly over a hundred years ago that they used long barrels in match guns in order to achieve lower muzzle pressures.

"When two things are necessary, it is fruitless to argue which is more important" (Reed Bradford). This is probly why my .375 H&H Encore shoots so well. Slow pressure rise, lower overall pressures (somewhat), AND low muzzle pressures. Several vents maybe on top of the barrel, or four at one place radially, starting four inches back from the muzzle could release pressure. It will be interesting to see if the vents mess up lead boolits too.

[runfiverun]

the experience iv'e had with the slower powders has shown me that when they just clean up and burn stable you are just about there as far as max velocity and accuracy.
you are generally in the 90% case full range before/when that happens.
it took me a bit of experimenting with using a weighed dacron filler to show me what the next weight step of powder would look like.
but it would sometimes mess with powder timing showing me a false accuracy node. [sometimes better sometimes worse]
other fillers reacted differently with the loads also, occasionally they would make the load act like it had a faster powder
other times it was like they were part of the powder weight [increasing velocity] or just as part of the boolits weight.

i would think a ported can on the end of the barrel would show the effects enough to decide whether to persue the issue.
my 10 twist AR-30 has a 30" barrel and the recoil reducer on the end of the barrel and it either has no affect or i have just worked the loads around it.
when i shoot the same load in my 20" ruger it has shot the lower end [2250 fps] stuff the same [accuracy wise for the rifle]
i haven't tried the higher end [2400 fps] rounds in it yet and checked either the velocity drop or the accuracy.