.257 Roberts brass differences

[smoked turkey]

I have just started loading for a .257 Roberts. I have been getting the necessary dies, mould, brass, etc. I have everything and even a few j-words for testing prior to loading with my cast boolits. I purchased some new and some used mixed head stamp cases from a fella on one of the larger gun auction sites. Got the mixed brass the other day and have been preping it for my use. I am using RCBS dies and their No. 3 shellholder. I ran into an unusual problem with brass cases marked "Super Speed". They won't fit the no 3 shellholder. I found that a MU-4 shellholder I have will work with those. My Remington and WW Super cases work just fine with the No. 3 SH but are slightly too small for the MU-4. I am not sure what the MU-4 is supposed to be for and I am not sure when or where I purchased it. I put the caliper on the extractor groove just ahead of the case rim and found the Super Speed cases are all larger than specifications according to my loading manuals. The other cases are fine. All cases chambered in my Rem 700 rifle. I weighed the cases and found a large difference with the SuperSpeed weighing an average of 186 Gr. while the others weigh an average of 162 Gr for the WW Super amd 169 Gr. for the Remington. Clearly the Super Speed have more brass in them by a large margin and hence less internal volume. I have set the Super Speed aside for now and am wondering if any one has run into this situation which the cases need different shellholders in order to work? I was wondering if the larger case rims were an indication of too much pressure or if that is just the nature of the brand. The cases do not appear to be overpressured. Primer pockets look good too. I loaded an initial load of 33 Gr. of IMR 3031 with Sierra 100 gr HPs and accuracy was good and extraction was good. This is the entry load for this bullet in Speer's No. 9 manual. This was with the Remington cases. This is long winded but I wanted to explain everything. Thanks for any ideas on the case differences.

[nicholst55]

This is a known problem, and the RCBS shell holder chart used to list two different shell holder numbers. It specified which number was for what brass. There were one or two other cartridges like that, also. I'll bet if you were to call RCBS and ask them real nice, they'd probably send you the other shell holder.

[flounderman]

the original 257 was made from the 7mm mauser. you will also find +p headstamps. you need to sort your brass.

[smoked turkey]

Thanks for the quick and helpful replies. In all my years of reloading I had never run into the same caliber brass not working in the same shellholder. I plan to call RCBS as nicholst55 suggested to see what they say about shellholders for the .257 Rob. I didn't realize the tremendous differences in case weights I found with the Super Speed vs Rem. Makes me realize that I really need to sort brass as stated. Thanks to everyone. BTY any one know who made the MU-4 shellholder and what it is supposed to be for? I worked with the Super Speed but far less than ideal. It just got me by so to speak for this round. The edge is knurled if that helps to identify it.

I just got off the phone with RCBS. They told me the No.11 shellholder would probably fit the Super Speed brass. They designate it as 3/11 in their table meaning that it takes both sizes of shellholder to accomodate the various manufacturers brass. They said the no. 11 shellholder is for the 220 Swift, which I don't have. They didn't offer to send me one and I didn't ask. Just wanted to bring this topic up to date. Just shows I am never too old to learn.

[beefan]

Please keep us updated on your cast load developement.

[swheeler]

Rcbs #11

[376Steyr]

I have a "MU-x" shellholder in the shop someplace. I think it came with my C-H single stage press, and I see the C-H website lists the 257 Roberts uses their #4 shellholder.

[atr]

if the extractor groove is not to specification I would wonder if the SuperSpeed brass would cycle throught the action properly ?

[smoked turkey]

As I indicated I set the SuperSpeed brass to the side for now because I wanted to do some load development with the Remington and WW Super brass since it was most compatable with the new Rem unfired brass I have, and I don't have the No.11 shellholder. I found that the MU-4 shellholder would work but the brass fit was a little loose to my liking. I appreciate hearing that the MU-4 is probably C-H brand. I was also concerned that the brass might not function properly through my rifle due to the differences as mentioned by atr. I did run sized brass into the chamber to see if it would seat and if it would eject. It did on both counts. I would be willing to send the 15 or so SuperSpeed cases to someone if they have a No.11 shellholder and want to go forward with it. I would like to get help with postage but the brass would be a gift. The brass looks very good so I think it is perfectly ok. PM me if interested. Thanks for all the interest and help on this. I have learned a little lesson here about differences in brass and can certainly see why some advocate using only one brand of brass for load development rather than using different brands because it probably will result in some differences in performance.

[swheeler]

ST; I ran into the same thing with 7x57 some 20 years ago, believe it was DWM brass and #11 shellholder worked just fine and the brass functioned as normal through the rifle. Now if you had fifty or a hundred cases I would recommend buying the 11 shell holder, 15 pcs I would just trade them or trash them.

[smoked turkey]

swheeler: Yes I agree with you on the small quantity. Thats why I offered to gift them to someone with a no. 11 shellholder. They look good. I sized and trimmed them. They are ready for priming and loading. I found a mu-4 shellholder that got me by but I decided I didn't want to put these into the mix since I have about 100 pieces of brass that will work just fine in my no 3 shellholder. If someone is interested in playing with these and is willing to send me $5 I will flat rate ship them. Not a great deal for 15 or so pieces of brass but I hate to trash them.