Anyone using a 9.3x57

[Noel]

Thank you for additional info Noel, as that did make a huge difference in how the numbers played out. Chasing the rifling was definetely the way to go to achieve those velocities, however, you would be at max pressures for sure.

I must apologize, as I did not mean to imply anything except for concern over the pressures. When I plugged the numbers in originally, I seated the bullet caliber deep, thus the source of the high pressure number.

No worries.

I still haven't looked at the charge I used from my notes but will. It had .250" freebore even with the long COL I was using. It would be interesting to see what the pressure was.

I have no doubt the load it at the upper end of the scale. That was my goal for that specific load. I was shooting it on a hot, humid day when I tested the load and it functioned very nicely.

 

[Why not?]

Thank you for additional info Noel, as that did make a huge difference in how the numbers played out. Chasing the rifling was definetely the way to go to achieve those velocities, however, you would be at max pressures for sure.

I must apologize, as I did not mean to imply anything except for concern over the pressures. When I plugged the numbers in originally, I seated the bullet caliber deep, thus the source of the high pressure number.

HSM_miner, I am not 100% certain on this, and perhaps you could tell us what your IB program shows. Does the seating depth make a lot of difference if the long freebore is there, since the freebore effectually increases the case capacity of the cartridge.

IOW, if the freebore in the chamber is half an inch before engagement of rifling, can you see what the pressures would be if the bullet was seated to the base od the neck (one cal), or seateed into the case say 1/4 of an inch further?

My guess is that it really won't make much difference.

Ted

 

[Pat Brennan]

I'm guessing that significant freebore also affects the pressure curve significantly, a la Weatherby.

 

[josquin]

…basically with the open sights, if you want speed you will need a taller front sight. IIRC at just over 2000 fps the 232 grainers shot to POA at 100 yards, faster went progressively higher...

I recently acquired a Model 46 and plan to try some 250 gr. I'll also get an NEI mould and start casting as factory bullets are pretty pricey for practice (unless you live in the US and can buy from Midway, of course. )

As to the POA, I'm going to get one of the New England Custom Gun adjustable front sights and the ramp. The front sight on mine measures about .471 above the barrel; an extra-low ramp (.300) and low front sight (.177) should be just a bit higher than that at the lowest setting and apparently it allows about .060" of added elevation, so I'm hoping I will be OK. I may also consider adding a little weight to the stock when I glass-bed the action. It's a wonderfully trim little rifle and lines up perfectly along the sights when I bring it to my shoulder, but I suspect the recoil will be a bit stiff, although not brutal. Another 6 oz or so, distributed between the hands, might improve things a little, as well as making it easier to hold steady.

How did RL 15 do for you, accuracy-wise? I already have quite a bit of it for my .303s so I'd like to try that first.

Stuart

 

[Noel]

Stuart, I used that same front sight on my 338-06 and quite liked it. I ended up ordering a hood like the Husqvarna and CZ's wear to protect it.

RL15 will likely be an alright choice. you will run out of case before you get much speed tho. As Ted mentioned the BL-C2 and fast powders in that area will give you the most out of the compact package. Let us know how it works out so I can ad it to my notes.
THanks!

 

[HSM_miner]

HSM_miner, I am not 100% certain on this, and perhaps you could tell us what your IB program shows. Does the seating depth make a lot of difference if the long freebore is there, since the freebore effectually increases the case capacity of the cartridge.

IOW, if the freebore in the chamber is half an inch before engagement of rifling, can you see what the pressures would be if the bullet was seated to the base od the neck (one cal), or seateed into the case say 1/4 of an inch further?

My guess is that it really won't make much difference.

Ted

Decreasing seating depth makes a difference in lowering pressure as long as the COL does not put the bullet into the lands of the rifling. So in essence, some freebore is required before pressures move in an upward direction. Interestly, bullet seating that was less than .366" yeilded the highest velocities, as Noel found out.

Lets see if I read that correctly, that would be a bullet seat to one cal vs a bullet seated to one cal + .250"? If that is correct, then my answer would be a general one. Using two different powders as reference, there was about a 4 grain drop in both powders, while maintaining roughly the same pressure with bullet seating to one cal +.250". Velocity seemed to drop 100-170 f/s with the deeper seating depth as well.

 

[303carbine]

The oodball calibers always had an appeal to me,7x57,8x57,9x57,I believe there is a 9.3x62 or something similar.
The 06 and 308's are rather "boring" compared to the European stuff. Don't get me wrong, boring works but has no pizzazz.

 

[Why not?]

Decreasing seating depth makes a difference in lowering pressure as long as the COL does not put the bullet into the lands of the rifling. So in essence, some freebore is required before pressures move in an upward direction. Interestly, bullet seating that was less than .366" yeilded the highest velocities, as Noel found out.

Lets see if I read that correctly, that would be a bullet seat to one cal vs a bullet seated to one cal + .250"? If that is correct, then my answer would be a general one. Using two different powders as reference, there was about a 4 grain drop in both powders, while maintaining roughly the same pressure with bullet seating to one cal +.250". Velocity seemed to drop 100-170 f/s with the deeper seating depth as well.

Thanks very much for your help, and sure that all makes sense, however that was not quite my question. You are reading me correctly, except everything else stays the same, with no reduction in powder charge. Only the seating depth changes.

I am wondering if you can plug that into your Internal Ballsitics Program and see if there is any significant difference in pressure between the loads. Again, my guess is that there will be little difference, as long as the lands are not engaged with either load.

This is assuming from your earlier posts that you have an IB program that generated the concerns you posted regarding Noels' loads, or were you just guessing on the

running at pressures over 55000 CUP.

Thanks again,
Ted

 

[HSM_miner]

Thanks very much for your help, and sure that all makes sense, however that was not quite my question. You are reading me correctly, except everything else stays the same, with no reduction in powder charge. Only the seating depth changes.

I am wondering if you can plug that into your Internal Ballsitics Program and see if there is any significant difference in pressure between the loads. Again, my guess is that there will be little difference, as long as the lands are not engaged with either load.

Yes there is significant difference. As COL decreases, the pressures generated increase significantly!!!

This is assuming from your earlier posts that you have an IB program that generated the concerns you posted regarding Noels' loads, or were you just guessing on the Thanks again,
Ted

Yes & no...meaning that IB programs give results that are at best "guesses" in themselves. Most require fine tuning of cartridge parameters and actual chronograph results to give accurate results. That said, I erroneously assumed in Noel's case that he had seated to .366", where he did not. What he did was extend the cartridge to the MAXIMUM COL that his magazine allowed to feed reliably. COL has significant effect on pressure, and to a smaller extent effect on velocity. The general relationship is as follows:
i) Increasing COL decreases pressure while slightly increasing velocity
ii) Decreasing COL increases pressure while slightly decreasing velocity

This is why bullet seat depth is so important.

 

[Why not?]

Yes there is significant difference. As COL decreases, the pressures generated increase significantly!!!



Yes & no...meaning that IB programs give results that are at best "guesses" in themselves. Most require fine tuning of cartridge parameters and actual chronograph results to give accurate results. That said, I erroneously assumed in Noel's case that he had seated to .366", where he did not. What he did was extend the cartridge to the MAXIMUM COL that his magazine allowed to feed reliably. COL has significant effect on pressure, and to a smaller extent effect on velocity. The general relationship is as follows:
i) Increasing COL decreases pressure while slightly increasing velocity
ii) Decreasing COL increases pressure while slightly decreasing velocity

This is why bullet seat depth is so important.

Of course seating the bullet deeper increases pressure because the case capacity has been reduced, and the converse the opposite. However, in the case of a chamber with considerable freebore, the case capacity is effectually increased greatly, to the capacity of the case, plus the volume behind the base of the bullet when it engages the rifling. Agreed? That is how Mr. Weatherby worked his velocity magic for so many years, with some freebores being as long as .700 inch.

This is also the reason case volumes for IB programs, whether they be Homer Powley's old slide rule or today's Quickload computer program, require the case capacity to be calculated below the base of the seated bullet. I am "guessing" that since the real capacity of these two instances in question is essentially the same, because the bullet engages the rifling in the same place in each instance, that the peak pressure will not be much different. The pressure curves will be different shapes, but max pressure nearly the same.

In spite of the results of IB programs only being, in your words, "best guesses in themselves", can you input your IB program, whatever one you are using, and see what difference is actually predicted for this case, only changing a single parameter, the difference in seating depth of 1/4 inch?

My "guess" is that the result will be very little difference in maximim pressure, and essentially none in velocity since the expansion ratio is so high for this cartridge.

Sure a lot of guessing going on here, even by the IB program.

Ted

 

[Why not?]

HMS_miner, really not trying to annoy you, so let's try this again from a different angle.

1) Is it true that there is little pressure developed before the bullet engages the rifling, since the bullet sort of "floats" (for lack of a better word) through the freebore?

I can pull a bullet out of a case with a pair of pliers, so it surely can't take much pressure to initially move the bullet from its seated position in the case to the rifling, as the only resistance is the inertia of the bullet itself before it begins the be engraved by the rifling.

2) If the above is true, why should seating depth affect pressure much before the bullet engages the rifling?

Trust I am conveying my question better.

With apologies to everyone for the serious hijack. This should probably be another thread.

Ted

 

[HSM_miner]

No worries....I am following your line of thinking (I think)

When I was developing a load for my 6.5x55, I seated my bullet to the cannelure on my starting load. Man, did I ever have pressure signs...flattened primer....expanded case heads. This should have been a light load. So I pulled all my bullets, and seated to .264" (one cal deep). This time when I shot, I have no pressure signs. Now as for the why seating depth affects pressure so much I am not sure I can not properly say, except that my real life experience reflects what the IB model predicts. I am sure there are people around here who can tell us the why and make it look easy.