shot my #5 rolling block

[kcrist]

Greetings all, first let me say thank you for the load data in Castpics, very helpful.
I have a #5 rolling block in 7mm Mauser and shot it for the first time yesterday. I used a greatly reduced load of 760 and had some questions.
First, the cases were very black like I was shooting black powder, is this normal? Second there were no notes about using Dacron or anything like a wad to take up the space in the case so I didn't use any. Any suggestions? I am shooting the 7mm, 145grn sil. cast in a RCBS mould with gas checks.

[atr]

Kcrist,
I have the same rifle,,,
if the cases were black, especially around the throat and shoulder that is a sign that the brass is not expanding adequately to seal the gasses. The dacron might also be adding to the darkening.
I dont use 760 as a powder, I dont think its the best powder for reduced loads. I suggest IMR 4895

[Ed in North Texas]

Greetings all, first let me say thank you for the load data in Castpics, very helpful.
I have a #5 rolling block in 7mm Mauser and shot it for the first time yesterday. I used a greatly reduced load of 760 and had some questions.
First, the cases were very black like I was shooting black powder, is this normal? Second there were no notes about using Dacron or anything like a wad to take up the space in the case so I didn't use any. Any suggestions? I am shooting the 7mm, 145grn sil. cast in a RCBS mould with gas checks.

I can't recollect 760 being position sensitive (irregular ignition if not held back against the primer by a wad or tilting the rifle up to shift the powder back in the case), but it might be. You say you were using a greatly reduced load. I would agree with ATR (prior poster) that the black on the cartridge case indicates your load was not causing the case to expand to close the chamber to slight gas blowback (obturate).

Checking LoadData for the 145 gr RCBS, the powders listed are 2400, 4227, 4198 and RL-7. In 145 gr with 760, but not the RCBS Sil, the Speer BT has a recommended load of 47 grains of 760 (2555 fps), the Speer FB Spitz at 49 grains (2783 - near max) and 50 grains (2820 - Max), and another listing of 44 grains with any of the Speer 145 gr Jackets as a starting load, with 48 grains as a max load (these last with CCI LR Magnum primers).

Needless to say these J-word loads are NOT recommended for the #5 RB. But there are 6 loads listed for 145 gr and 760, but over 80* loads listed total for the 145 gr projectile. So it is reasonable to say that 760 is not the best powder for the 7x57 with a 145 gr projectile, and (because it is not listed at all with your boolit) not even recommended for the RCBS 145 gr Sil boolit.

* Because they list loads by source (e.g. Lyman, RCBS manuals and Handloader Mag articles), there certainly will be some duplication of loads in this total.

[leadman]

Ball powders are not the best for reduced loads. H4895 can be reduced 60% from the max load listed on Hodgdon's website.
Hodgdon's website has listings for Hodgdon, IMR, and Winchester powders.
Lyman's Cast Bullet Manual #4 has a listing for 748, but not 760. The powders listed are Unique, SR-7625, SR-4759, IMR4227, AA5744, AA 1680, Reloader 7, IMR-3031, AA 2230, W 748.

Strongly suggest you use a different powder.

[shaggist]

It is my understanding that the Model 5s, chambered for the 7 x 57 cartridge, were made substantially more robust than the earlier black powder RBs. If this is the case for your gun, why the extreme concern about downloading the cartridge to BP levels? Am I missing something here?

[MtGun44]

I have had amazing accuracy with 35.0 IMR 4064 under a Hornady 175 JRN. Like 1"
to 1.5" at 100 yds. Moderate load, shoots to sights. My bore is so worn as to make
me avoid boolits, the rifling is best described as 'vestigal'. One day I'll try, but it not
my top priority.

I strongly recommend that you ONLY neck size the brass fired in this chamber and
watch CLOSELY for signs of case separation. The RB action has near zero camming closed
capability, so the chambers are oversized to ensure that dirty ammo will chamber properly.
No problem for 1st shot, but the cases stretch so much that if you FL resize the case may
well separate on the second firing. Do not mix this brass in to load for any other rifle. Once
fired in the 7x57 RB it needs to be permanently dedicated to that rifle.

The RB is a fine action but will NOT survive a badly blown case. If the pressure is released
into the interior of the action, the sides blow out and release the pins, letting the block blow
back HARD. Great guns, but watch your brass condition. A partially separated case will still
seal pretty well and is not catastrophic, but if you do manage to rupture a case in a
major way - expect totaly destruction of the action, unlike the way most bolt guns deal with
this same failure.

Bill

[kcrist]

Thanks to all you gents who do their best to have people avoid killing or maiming themselves. The 760 load data I got was off the Castpics site on their Cast Bullet Load Data. It says the Load Source was CastData R1. The start charge was 27 gns. of 760 and I loaded the rounds at 25gns. I will try loading additional rounds with 748 and IMR4895 and RL7 to see how those work. This rifle does indeed have a oversize chamber as a field guage dropped right in so that is why I am approaching this very slowly and cautiously. Thanks again!

[Ed in North Texas]

Do not mix this brass in to load for any other rifle. Once
fired in the 7x57 RB it needs to be permanently dedicated to that rifle.

Bill

Because I have other 7x57mm rifles, my solution to this problem was to buy 100 once fired .270 cases to be turned into 7x57 for the RB. While I grew up reading Jack O'Connor in Outdoor Life, I never picked up a yearning for a .270 and don't own one. Makes keeping the RB cases separate easy. Finally put the case forming/trim die I bought 40 years ago to work.

Ed

[L Ross]

kcrist, Indeed you need to form your brass specifically to these rifles as they are chambered for 7 m/m Spanish Mauser. I anneal, inside lube, and expand to 30 cal. Then neck size just enough to chamber. Then expand the small part of the double stepped neck to .285" then load a .287" 160 gr. cast bullet over 16.0 gr of IMR-4227. After fireforming you should only neck size enough of the neck to hold a bullet. Leave the 30 cal. double step in the neck and the shoulder sould be pushed forward enough to properly headspace. Good luck and shooting.

Duke

[Buckshot]

...............I have a M1897 in 7mm. Shoots cast like a house afire.

http://www.fototime.com/51033A5247B82E1/standard.jpg

These 2 targets were shot with it using the indicated surplus powders and the RCBS 7mm-168 cast boolit. The slug with lube and GC weighed 172grs so the velocities are pretty much at the original 7x57 design with a 175gr slug. Fired at 50 yards, original sights.

I have no problems with the chamber on my rifle other then the caseneck. After firing the neck expands enough to almost allow a 30 cal slug to drop through [smilie=1: I neck size only, and as a rule do not shoot cast to those velocities. I normally use 42 grs of either of those powders + dacron and the mentioned slug. The velocity runds 1750 fps. I anneal and full length size the cases every 5th firing.

.................Buckshot

[Ed in North Texas]

...............I have a M1897 in 7mm. Shoots cast like a house afire.

Nice shooting.

I have no problems with the chamber on my rifle other then the caseneck. After firing the neck expands enough to almost allow a 30 cal slug to drop through [smilie=1: I neck size only, and as a rule do not shoot cast to those velocities. I normally use 42 grs of either of those powders + dacron and the mentioned slug. The velocity runds 1750 fps. I anneal and full length size the cases every 5th firing.

.................Buckshot

Have to ask: If you are neck sizing, why are you full length sizing every 5th firing? Is there some "growth" in the case body after that many firings? Some other reason?

[Buckshot]

Have to ask: If you are neck sizing, why are you full length sizing every 5th firing? Is there some "growth" in the case body after that many firings? Some other reason?

..............The cases simply get harder to chamber. Succesive moderate pressure loads finally get the casebody close to fitting a bit too well for easy chambering (AND extracting) is my guess.

...............Buckshot

[Ed in North Texas]

..............The cases simply get harder to chamber. Succesive moderate pressure loads finally get the casebody close to fitting a bit too well for easy chambering (AND extracting) is my guess.

...............Buckshot

Thanks. That was my guess, but better to ask. I believe in the idea that the only stupid question is the one you don't ask.

[curator]

I found that indexing the cases on my 7mm RB allowed several more loadings before they became difficult to chamber. Apparently my (and several others I have seen) breech block does not lock up at an exact right angle to the bore/chamber. I discoverd this when trimming fired cases with the Lee trimmer.

[ShootingLooney]

WARNING: A bad as it is to go OVER MAXIMUM loads, it can be just as dangerous to go UNDER MINIMUM loads.
You can set yourself up to a catastrophic failure, as there is too much air space in the cartridge, and you get too "quick" a burn which can give you a verticle pressure curve.
Once, while working in a gun store, I saw a beautiful Weatherby blown up, and it turned out the guy was using too little powder to reduce recoil.
You may want to avail yourself of a copy of the Lyman Cast Bullit Handbook, and/or the 49th Edition Reloading Manual, for safetys' sake.