Bertrum vs Rocky Mountain Brass

[klw]

Bertrum brass is better than nothing, I think, but not much better. Rocky Mountain brass is machined. Know relatively little about it. Anyone know which of these two would last longer, i.e. which could withstand more reloads?

[powderburnerr]

Rocky Mtn ctg is super quality custom brass , send a chamber cast along with a sample bullet and you will not have to resize the brass ever , it will come back to you like the old everlasting brass ..

some bertram is good stuff, but the 50 cal stuff I had, I had to turn the heads and thin the heads to get them to work a lot of extra work and very hard with out a lathe inside volume also varied a lot ie capacity.... just my humble opinion.......Dean

[Bent Ramrod]

Bertram has gotten better over the years. In the past, it was infamous for poor metallurgy. I had 8 cases out of 20 in .43 Spanish split on the first firing, with black powder.

Their .25-21 and -25 was better endurancewise although, as Powderburnerr said, they are all over the place on rim diameters, base diameters and lengths. The .25-25 lengths are all too short, and if they do finally split, it's along the sides, so they cannot be trimmed to .25-21. I got a box of .405 Bertram brass, once fired, which was scaly on the outer surface. Nonetheless, it has held up very well even though I formed the cases to .35 WCF and shot many cast boolits and then more than a few full-house loads out of it.

My only experience with RMC brass is in the .22-15-60. It is very well made, evenly machined and all dimensions consistent. It does seem to get quite brittle after perhaps 8 to 10 full-length resizings, whereas the Bertram, if it survives the first few firings, seems to do somewhat better. With the Bertram, after a while maybe you begin to lose a case every time (or every other time) they go through the loading cycle; with the RMC, there comes a time when they all begin to crack open, generally upon expansion after full-length sizing. The RMC cases are turned, and this behavior may be characteristic of turned vs drawn brass. The RMC stuff doesn't seem to be helped much by annealing, either. But this is my only experience with RMC brass.

[Buckshot]

.............I've never had a issue with my Bertram brass. First I had was 577-450 for which I paid $108/20 (Huntington). This was before Midway started carrying it and I could buy it wholesale with my FFL. As a consequence I decided I would anneal it every third firing. I've since gone to every 5th firing. I have 120 Bertram 577-450 cases (in batches of 20) and the most experienced batch has 34 firings. Havn't lost one yet. They are about 16 years old.

The other Bertram brass I have is 100 cases of 43 Spanish and 140 cases of 43 Mauser. These cases have between 14 and 18 firings apiece and I anneal every 8th firing. I guess the cases are between 10 and 14 years old.

Three of us went together and bought a batch of Red Willow Armory (turned) 577-450 brass and 2 guys had a total of 6 split casenecks just as they set in the boxes. New, as receieved, never fired! RWA said to send them back and they replaced them. The same 2 guys had a total of 10 split necks at the first firing. RWA said to send them all back and they'd replace the entire batch. I never shot mine as I was using Bertrams but I also sent mine back.

That was maybe 8-9 years ago and I have yet to shoot my replacements! The other 2 guys ended up with further issues, but not as bad as before but still discouraging.

The main issue with turned brass is grain structure in the metal. It's not just RWA, but also the NDFS (Devon/England) turned brass 577-450 and 577 Snider has problems with this. You can't get away from it without annealing after EVERY firing. Or at least with the NDFS brass you can't.

At the mill where the alloy is formed into bars, it's rolled or extruded and the grain structure flows with the form the material is forced to take. It's then annealed so there isn't any stresses. When the brass is machined, the grain structure is cut. It flows lengthwise of the rod, so you can picture it as paper tightly rolled to the OD of the rod, with the layers of paper forming the grain. Or possibly like a bundle of spagetti?

As the outside taper of the case is machined it severs multitudes of the grain boundries, and likewise does the internal machining.

On the other hand, drawn cases begin (as I'm sure you know) as coin blanks punched from a sheet. The sheet is rolled which orients the grain. and when blanked only the outer periphery is cut. Then through several dies it's drawn into a longer and longer cup. While the metal is in fact thretched and forced to move, the grain structure remains intact and in the same relationship with each other.

Another example is threads which are cut into a bolt vs threads that are rolled. Cutting does the same thing as turning brass cases from solid, ie: the grain structure is intrupted multiple times. Threads that are roll formed streatch and also compress the grain structure of the material but does not interupt it in any way. In threads of the same pitch and material the rolled threads are much stronger then cut threads.

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