I'm loading for an 8x60mm Mauser and came up with an odd condition. Worked up a load with 200 grain slugs, checking velocity with a Chrony, when, as I just go past "factory" velocity I encounter heavy bolt lift. No badly flattened primers, no stretching or brassing on the cartridge cases. The brass is RWS, bullets are Norma and Woodleigh, powder charge s are 48.5 gr IMR 4895 in RWS brass. A charge of 49.2 gr of N203 in Norma brass meets the factory velocity with no significant pressure signs. Accuracy is good, but I am a little stymied as I've never seen this occur before. Any thought??

had a similar experience with a 45-70 switched
to a different make of brass problem went away

Because it is an 8mm there is just a chance that the actual groove and bore diameter are a bit tighter than your bullets outer diameter. So pressure is there as velocity is only one indicator, and the other signs are those of which you speak. I must also agree that changing brass might allow a lessening of pressure. BTY, ? can a fired case accept a bullet?

quote:

Originally posted by sierra2:
I'm loading for an 8x60mm Mauser and came up with an odd condition. Worked up a load with 200 grain slugs, checking velocity with a Chrony, when, as I just go past "factory" velocity I encounter heavy bolt lift. No badly flattened primers, no stretching or brassing on the cartridge cases. The brass is RWS, bullets are Norma and Woodleigh, powder charge s are 48.5 gr IMR 4895 in RWS brass. A charge of 49.2 gr of N203 in Norma brass meets the factory velocity with no significant pressure signs. Accuracy is good, but I am a little stymied as I've never seen this occur before. Any thought??

Heavy bolt lift is a sign of high pressure=not good.

Don

I guess I have trouble understanding the method of working up a load to "factory" velocity. Not sure what you mean.

First FACTORY velocity or even velocity from loading manuals does not equate to a velocity from any given rifle.

Just because N203 in a norma case will give you "X" velocity without pressure has no bearing on if a completely different powder and case will allow you to reach the same velocity without pressure signs. Not all powders will allow you to safely reach the same velocity in all cases. If they did then you would only need one powder.

Heavy bolt lift is normally a sign of excess pressure. You don't have to have all the signs to have pressure. Simply a little heavier web might hide the head or primer pocket expansion doesn't mean pressure isn't there. Look for any signs not all signs.

I could also be completely confused as to the conclusion you are trying to draw.

I have to agree with Paul and Don. There is nothing that guarantees you can reach factory (or any other) velocity with a given powder/primer/brass/bullet/chamber/temperature (etc) combination.

If you get a hard bolt lift, you have to assume high pressure.

- mike

Many post-WWII 8x60 I or J rifles will be .318" instead of .323". Hence, if you are using .323" bullets you can guess as to the potential problem. If it is a 8x60 S or JS then the .323" bullets would be OK. However, looking for primer condition in such a rifle as a determinant of excessive pressure might not yield much as the 8x60 is a 49,000 PSI cartridge and primers may not show any flattening until over 70,000 PSI. Hard bolt lift or sticky extraction are indicators that should not be ignored.

Two things come to my mind on this. One, I think you should slug the bore to determine if it is .318" or .323".
Second, I'm thinking you'd be better off with a slower burning powder. I'm not familiar with the Norma powders as I don't use them, but I do use a lot of the 4895s and I'm of the thought that it might be just a bit too fast burning for the bullet weight you're using. You might consider IMR-4350 with bullets that heavy.
One thing to consider is, at least in my rifles, IMR-4895 as made by IMR is a bit faster burning than the version that was made by Du Pont. Anyway, that's my take on your problem.
Paul B.

Also check your case brass length. Might need triming.

I had a heavy bolt lift on a known good load and it was the brass had stretched and the neck was wedged in the throat . I trimed the brass problem solved

Thanks for the swift replies, guys. This is a Sako FN Mauser chambered for the "true" 8x60mm, 0.318 bore, and all bullets used are 0.318, which are hard to find. Nope, not using .323 bullets, I keep the two sets of slugs widely separated for safety, like keeping .270 WCF and .280 Rem apart. I concur about the heavy bolt lift meaning pressure, look out. Extraction is smooth too, and as I've never encountered this variation of pressure signs, I was quite curious if anyone else has seen the same.. It seems odd that the RWS and Norma brass measure the same (except for weight), so I am backing off and shifting to strictly Norma powders and RL19.
For those not familiar with Norma powders, they do give high velocity with low pressure, same as the RL series, only now Norma is becoming hard to find. My guess is that Alliant is running them out of the US market, since their powders come from the same manufacturer.

Quickload says pressure should be in the low 50K. If you are SURE your bullets are not .323", then I don't know it could be.

As far as Norma powders, Grafs stocks the full line. HTH, Dutch.

The 8x60 has con good case taper which increases bolt thrust at the high end. This equates to feeling harder bolt lift sooner. Also simply because you equal factory velocity with 4895 does not mean you are equaling factory pressure. I'd bet you are exceding factory pressure. You might want to switch to a slower powder like 4350, RL 19 or H4831SC (my choice) with that 200 gr bullet.

Larry Gibson

quote:

Originally posted by sierra2:
I'm loading for an 8x60mm Mauser and came up with an odd condition. Worked up a load with 200 grain slugs, checking velocity with a Chrony, when, as I just go past "factory" velocity I encounter heavy bolt lift. ...

Hey Sierra 2, As the others have pretty much said, you are "Over Pressure" for those specific components in that rifle.

As a side note, it seems you might somehow mistakenly believe that when you see a specific "Velocity" that you can directly relate that to an arbitrary Pressure from a Load Manual. A lot of folks have done the exact same thing, and a lot still believe that is true, but, it is not true.

Velocity DOES NOT equate to a specific Pressure due to all the variables in the Bore and the individual variations in each component which creates your Cartridge.

Best of luck to you and back off that Load.

quote:

Originally posted by sierra2:
I'm loading for an 8x60mm Mauser and came up with an odd condition. Worked up a load with 200 grain slugs, checking velocity with a Chrony, when, as I just go past "factory" velocity I encounter heavy bolt lift. No badly flattened primers, no stretching or brassing on the cartridge cases. The brass is RWS, bullets are Norma and Woodleigh, powder charge s are 48.5 gr IMR 4895 in RWS brass. A charge of 49.2 gr of N203 in Norma brass meets the factory velocity with no significant pressure signs. Accuracy is good, but I am a little stymied as I've never seen this occur before. Any thought??

What is the velocity of the "factory load" you are measuring by? I used to load the 8X60RS for a double rifle with the 200-grain Nosler partition and 54.7 grains of H205 in RWS 7X65R cases necked up and trimmed at 59mm. MV of this load was 2620 FPS, with no signs of pressure that would have been too high for my double. This load put both barrels into 2.5" at 100 meters.

Now that powder is gone, and I have NOT found a replacement for it that gives equal velocities at acceptable pressures for an old double. (Otherwise, I could get the same performance with a similar charge of IMR 4350.

I am now using 58 grains of RE22 with the same bullet. The MV is 2450 FPS, 170 FPS less. But the pressure and regulation is still "acceptable".

You might try making some cases from WW .30/'06 brass, to see if it will permit higher velocities without expanding the primer pockets.