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2399 Views 11 Replies 6 Participants Last post by  gunboat
Things seem to have gone quite on 8x58RD rolling blocks so just to stir the pot has anyone done any load development since the post on Norma loads, pressures, etc. etc.
Would be very interested as my cases should be here this week and will start to work up a few loads.
And would like to pick the more experienxed 8x58RD shooter brains on this forum.
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I have been working up some loads with a 205 gr cast bullet.
It is still a work in progress, so I won't bore you with all the details.
I have tried several powders and am getting the best results with Unique.
I am trying to stay close to the 28.6Kpsi suggested as maximum in the post in the sticky at the top of the forum.
I have been able to finally get consistent ignition and velocities, but my bullets were a little too soft and accuracy was not acceptable.
I have cast some harder bullets and should be posting the load developement observations and data soon.
There is a lot more information than I can put into a quick reply, but consider using Unique under a cast bullet and work the load up to just under 1500fps to start. You should be OK to start with 12grs. Unique and a bullet somewhere close to 200 grs.
From what I have seen so far, I don't think that the 8x58RD rolling block rifles are likely to shoot sub-moa with any safe load, but I believe that 1-2 moa is do-able.

I expected a little more response, myself. I'm very curious to hear what other folks have been doing and what has worked.
As a follow up to my earlier post, I shot the gun today with bullets cast from 50/50 lino/ww. The groups shrank down to about 2moa, average. I had a couple of 3 or 4 shot groups less than 1moa, with flyers to open them up. I believe that the gun may be capable of near-moa accuracy, however, I have reached the limit of how well I can use open sights.
I have to make a decision about making or buying some sort of aperature sight.
There are two factors to consider.
First, I am hesitant about modifying the gun by drilling holes to mount another sight.
Second, a decent tang sight will require the expenditure of significant funds, which I do not have handy.

It has occured to me, that I could machine a scope base that would clamp on the barrel and mount a long eye relief scope.

I'm open to suggestions regarding the sights.

As to using slower burning powders, I've had so much trouble getting good ignition, even with Unique, that I pretty much rejected the idea. Besides, with the current cost of powder, it seems like and expensive way to get a load with filler. Is there any reliable data regarding pressures with slower powders?

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I am surprised that you would have any trouble at all getting Unique to ignite consistantly with any of the standard rifle primers, such as Remington, Winchester, CCI, etc. I would suspect that you have not been consistant in getting the powder fully back in the case,
Thanks Niklas,
You are quite correct about the powder being in the back of the case.
When I tap the case on the bench to settle the powder to the back and then chamber it carefully, the ignition problems go away. Although many advise against using anything on top of the powder, I put a 2gr. piece of dacron fiber (quilt batting) in the case and press it down tight against the powder. The ignition of the powder is now very consistent. The extreme spread and standard deviation of the velocity immediately dropped to about 1/3 of the values without the filler.

.., that you are encountering a common problem with these guns, that is, that you have to get muzzle velocities up to a minimum velocity before bullets quit tumbling. For most suitable bullets in my gun that minimum has been 1300-1350 fps.
I have checked my targets at 25,50 and 100 yards and see no sign of the bullets starting to tumble. My velocities are just inder 1500 fps.

For some bullets I have yet to find a load that does not give tumbling bullets -- granted, these poorly performing bullets are undersized, being 0,321-0,323, that is, 32-40 or 8X57 Mauser caset bullets. I have yet to try any mantled bullets.
I measured the bore of my rolling block at the muzzzle and found it to be .329" . I am using a Lee bullet mould designed for the 8x56 Hungarian. It casts a 205gr. round nose, gas checked bullet at .330" to .333", depending on alloy. I am sizing thesse to .329 with the Lee push through sizer and lubing with Lee Liquid Alox. These bullets shoot much better when cast of a hard alloy than a soft alloy. I would be very interested to know how many of these rifles have a .329" rather than .323" bore. I think that you could maybe get away with an undersized jacketed bullet, but this is not an option when using cast bullets.

I have been using Reloader 22 for at least 20 years in 7X57 and 7X57R. There are lots of data for those "twins" and especially for even larger capacity cartriges. Some of those loads were full case, compressed and never had a problem with ignition. A simple extrapolation from cartridges like 7X57 to 8X58RD, based on difference in case volumes indicates that moderate loads of Reloader 22 will have chamber pressures below 30.000 psi. I go even a bit lower than this in a rather tight chambered 8X58RD with 210 grain cast GC bullets. Velocities are quite low, about 1750 FPS from 33 inch barrels, cases fall out of chamber, groups are as good as I can shoot with the military sights, that is about 3-4 inches at 150 meters.

FYI, burn rate for Reloader 22 is very close to that of Norma MRP.

I think the reason you are not getting more responses is that what most (all?) of us know has already been posted on threads extant on this board.

Thanks for the information on Reloader22 powder. I still question the economy of using powder as a filler, considering the recent price increases on powder.

If anyone has had good results with XMP5744, I would be interested. I tried it once but found that it was very dirty, leaving the case necks and bore coated with heavy residue.

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I will be very interested to hear your results with the 5744 and cast boolits.

I doubt that I will get much more serious shooting done this year. The temps in New England don't agree with me at all in the winter, for shooting. Anything less than 40 degrees and I can't feel my fingers, anything over is likely to be uncommon for a few months.
The break will give me time to stock up on boolits anyhow. I want to try water dropping some WW to save my stock of lino. I'm starting to get neck splits after four loadings because the CH4D dies are working the case necks too much. I think that I will spring for a set of Lee custom collet sizing dies. I also see some merit in mounting a tang sight on the roller but they certainly aren't giving those away!

I hope that Bertram gets the problems with the brass straightened out. I'm perfectly satisfied with the reformed 8x56 Hungarian cases for the 8x58RD, myself but there are a couple of other calibers that they make that interest me.

Does your RB have a very long throat? Mine is so long that only the gascheck would be in the case if I seated out to touch the rifling. I seem to need a very hard boolit to survive the 1/2" jump to the rifling.

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