7x64 RWS 173 Grain

[mchughcb]

Not that much. Maybe 150fps according to the handbook. But that's it.

[Gun Barrel Ecologist]

... why would a reloading manual list a 52 grain max for 2750fps and we are only getting 2318?
Thankyou in advance
Allan.

Because Nick Harvey is extrapolating from a range of other sources, and in the case of the 7mm's, possibly even other cartridges (*cough* .280 Rem *cough*)

Just looked in the DEVA manual, and whilst I can find your bullet, of US made powders, data is only provided for Hodgden and IMR powders.

Quick glance in McDonald et al reveals loads with R19 for both the 7x65R and .280 Rem with the 175g PP;
starting: 48 for 2400, max 51 for 2490 for the former and a starting load of 45.5 for 2300 and max of 52 for 2600 for the latter.

The TMR should have less bearing surface than the PP which might explain some velocity difference but my money is still on Harvey just fudging the figures at the upper end

[9.3x64]

... why would a reloading manual list a 52 grain max for 2750fps and we are only getting 2318?
Thankyou in advance
Allan.

Because Nick Harvey is extrapolating from a range of other sources, and in the case of the 7mm's, possibly even other cartridges (*cough* .280 Rem *cough*)

Just looked in the DEVA manual, and whilst I can find your bullet, of US made powders, data is only provided for Hodgden and IMR powders.

Quick glance in McDonald et al reveals loads with R19 for both the 7x65R and .280 Rem with the 175g PP;
starting: 48 for 2400, max 51 for 2490 for the former and a starting load of 45.5 for 2300 and max of 52 for 2600 for the latter.

The TMR should have less bearing surface than the PP which might explain some velocity difference but my money is still on Harvey just fudging the figures at the upper end

Thanks GBE.
It certainly seems very low for a powder that has such a good reputation in the 7x64 for accuracy and velocity.
Factory loads are doing 2623 fps.
I am over 300 fps below that.
Doesnt make sense to me.

[Gun Barrel Ecologist]

I recently looked over your past threads for loading this round - it just seems to be a PITA for both yourself, Oscar and Secondtry to get anywhere near RWS factory velocity without ignoring ADI / Nick Harvey maximums and working your way up with a chrony and quickload, and perhaps a drop tube if you run 2217

Dug out my PDF of DEVA and extracted these; not sure how much help other than looking at differences in velocity between bullet types in 173 to 177g

Deva 7x64 1.jpg

Deva 7x64 2.jpg

Deva 7x64 3.jpg

[Saugmann]

Thanks for posting your experience.

I'm having sort of the same experience with my 7x64 and load manuals, but QuickLoad seems more on the money.

I will say that manuals often have loads fired in barrels a lot longer than a standard Blaser barrel. 26" is not uncommon. That will make a difference for some calibers.

Please also bear in mind that it's likely that a manual max load is the load that produces maximum pressure for the combination.

Considering variations in temperature, powder batches etc. the manual max load is probably not one you should "aim for" (pun intended).

With my 7x64 and 168 grain Berger hunting VLD I started to see light pressure signs before reaching the max load.

My OCW test got me to a load below the ones with pressure signs and a reasonable MV. I will add that the load MV (measured with a magneto speed) was a little under the MV indicated by QuickLoad. Just a little and the difference might be caused by my sound moderator.

I will post more details in a separate note, but I got around 2500 fps with the 168 grain hunting VLD.

I'm not sure you can extrapolate this performance to your bullet as the VLDs have a very different design compared to your bullet.

I hope this helps.

I'm travelling this week, but will try to remember to run your load in QuickLoad to see what the programme suggests.

[9.3x64]

I recently looked over your past threads for loading this round - it just seems to be a PITA for both yourself, Oscar and Secondtry to get anywhere near RWS factory velocity without ignoring ADI / Nick Harvey maximums and working your way up with a chrony and quickload, and perhaps a drop tube if you run 2217

Dug out my PDF of DEVA and extracted these; not sure how much help other than looking at differences in velocity between bullet types in 173 to 177g

Deva 7x64 1.jpg

Deva 7x64 2.jpg

Deva 7x64 3.jpg

The velocity in the above is around the 2700 fps mark, which is what most manuals quote for 175 grain projectiles.

[9.3x64]

Thanks for posting your experience.

I'm having sort of the same experience with my 7x64 and load manuals, but QuickLoad seems more on the money.

I will say that manuals often have loads fired in barrels a lot longer than a standard Blaser barrel. 26" is not uncommon. That will make a difference for some calibers.

Please also bear in mind that it's likely that a manual max load is the load that produces maximum pressure for the combination.

Considering variations in temperature, powder batches etc. the manual max load is probably not one you should "aim for" (pun intended).

With my 7x64 and 168 grain Berger hunting VLD I started to see light pressure signs before reaching the max load.

My OCW test got me to a load below the ones with pressure signs and a reasonable MV. I will add that the load MV (measured with a magneto speed) was a little under the MV indicated by QuickLoad. Just a little and the difference might be caused by my sound moderator.

I will post more details in a separate note, but I got around 2500 fps with the 168 grain hunting VLD.

I'm not sure you can extrapolate this performance to your bullet as the VLDs have a very different design compared to your bullet.

I hope this helps.

I'm travelling this week, but will try to remember to run your load in QuickLoad to see what the programme suggests.

Thankyou Saugmann.
The velocity quoted for the RWS load I mention is out of my barrel. 2623 fps four shot average.
I would really appreciate your offer to run my numbers in quick load to maybe gauge whether I can try another .5-1 more grains.
I am not seeing any pressure signs at 54.5 grains but max is apparently 52 grains.
I just cant understand how 52 grains could be max and only produce 2318 fps.
Is it possible that the Blaser 7x64 chambers are on the larger side of specifications and possibly reduce pressure and hence velocity.
As GBE mentions above their are a few of us with similar results with the 7x64.

[Vaughan]

I'm not sure if this QL data is helpful or if I've put your data in correctly and I've NEVER loaded this caliber so I could have screwed this up so please be careful with this data!

If you want specific changes, I'm happy to rerun this.....

Hope it helps anyway...

[9.3x64]

I'm not sure if this QL data is helpful or if I've put your data in correctly and I've NEVER loaded this caliber so I could have screwed this up so please be careful with this data!

If you want specific changes, I'm happy to rerun this.....

Hope it helps anyway...

Thankyou Vaughan, very good of you.

[Scotch_egg]

I have been keeping an eye on this topic. I have an R93 7x64 I am about to start load development. I have found that the factory max are very conservative with loads in excess of 10% above max being used by people.

[9.3x64]

I have been keeping an eye on this topic. I have an R93 7x64 I am about to start load development. I have found that the factory max are very conservative with loads in excess of 10% above max being used by people.

Yes I have noticed the same trend.
I am no dare devil and certainly do not want to do anything irresponsible.
However I am finding it hard to believe 52 grains of RL 19 is max.

[Corjack]

This is a really good thread guys. I had not been following it. Good job everyone.

[stokesrj]

I think there are a couple of factors at work here that result in very conservative load data.First the CIP max allowed pressure is 60,191 PSI while the SAMMI max allowed pressure is only 55,000 PSI. Additionally there are two bore diameters used for the 7X64 cartridge, the European original .285" and the US 7mm bore diameter of .284".
I think the anemic 55,000 PSI is guard-banded by the possibility of shooting .285 bullets through a .284 bore. When these two things are combined you get load data that is well under what the gun, brass, and primer can handle, kind of like what we are seeing. That's my take on it anyway.

[9.3x64]

I think there are a couple of factors at work here that result in very conservative load data.First the CIP max allowed pressure is 60,191 PSI while the SAMMI max allowed pressure is only 55,000 PSI. Additionally there are two bore diameters used for the 7X64 cartridge, the European original .285" and the US 7mm bore diameter of .284".
I think the anemic 55,000 PSI is guard-banded by the possibility of shooting .285 bullets through a .284 bore. When these two things are combined you get load data that is well under what the gun, brass, and primer can handle, kind of like what we are seeing. That's my take on it anyway.

Thanks Bob, I was hopeing you might throw your opinion in.
When I get time I am going to slowly work up in small increments and check very closely for pressure signs and case head measured expansion.
The sort of results I have expirienced make you wonder about safe starting loads in some manuals.
I notice quickload puts a very clear warning on its data re safe starting loads.
I can see why some of you guys get so interested in your reloading, it is absolutely fascinating when you get a chronograph.
I think I have been well and truly bitten by the reloading bug now.
I am so glad I got a magneto speed for Christmas.

[secondtry]

I'm not really surprised by the discrepancy between book figures and your results. As GBE said, all sorts of sources have been used for book loads for various calibres in the past, ranging from guesstimates to what someone else might or might not have done.

The less popular the calibre, the less likely there is to be much meaningful research. Add these issues to the technical aspects described by Bob, and discrepancies are very likely.

Now that you have the tools and the knowledge, I would simply keep working up in .5gn steps.

I have very little experience with RL 19, but it seemed very bulky to me and also did not deliver it's reputed speed in my application. You may run out of case room before you run into excessive pressure.

It is also worth remembering that while we are all happily stuffing in more fuel with some of these calibres and chambers, NOT all data is conservative. I have on a couple of occasions run into combinations that simply would not accept any thing like max loads, one running well at over 10% below the max listed in a couple of manuals.