Many of you might know that I picked up an absolute doll of a 257 Roberts a few weeks back.


So, I gather a bunch of load data off of loaddata.com. I compile it all into a spread sheet to find out what the max charge weights for 100 gr bullets will be with various powders.

I pick up 600 Nosler 100 gr e-tips seconds to focus on first. The other day, I run a pressure/accuracy ladder with 3-shot groups. My CED M2 chrono is down and out, waiting for a replacement sensor to come in. I feel like I'm walking in the dark on the edge of a precipice with out a chrono.

I'm new to M70's and any pressure signs they exhibit. I know what to watch for with M700's and their clones.

At the range, I 'm running the ladders and see zero pressure signs and I'm several charges from my top loads (.5 gr incremenets) and all of a sudden the bolt lifts hard, the cartridge comes out and I see the primer is gone. It's sitting on the follower. Gang, I've been loading for over 36 years and have never seen this.

My question is this: are their any particular pressure signs to watch for with a pre-64 M70?

Alan

quote:

are their any particular pressure signs to watch for with a pre-64 M70?

I've only owned one.....a Gopher Special in .270....and I loaded it just like any other modern bolt rifle and watch for the same signs...

It's the case....not the gun!

BTW....that's an awesome looking gun!

Not sure what your chrony will tell you that your brass won't but thats all been covered at great length on these pages.
I agree with Vapo that it is a brass issue at least that piece.
Do what you feel comfortable with but if it was me I would shoot that load again and if it gave a repeat performance then you have a pressure problem and back down. Also I'm assuming that no other loadings leading up to this showed ANY pressure signs on the brass.
Watch your brass and primers carefully it will tell you what you need to know about pressure, your chrony will tell you the speed of your load in your rifle nothing more.

quote:

Originally posted by GSSP:
...all of a sudden the bolt lifts hard, the cartridge comes out and I see the primer is gone. It's sitting on the follower. Gang, I've been loading for over 36 years and have never seen this. ...

Well..., that would be a Pressure Indicator in one of my rifles. But, perhaps it isn't in a P-64 M70.

So what did the CHE & PRE tell you as you were Developing your Load? Did you see a gradual increase in the numbers, or did it just jump up all at once?

As usual, a chronograph doesn't tell a person spit about Pressure.

What did the primers on the shots previous look like? Were any of them of the same powder charge? What did .5 gr less look like? Primers flat, or cratered? What did the other extracted cases look like?

Is this all fresh brass, fired in another rifle X times, or "range brass"?

What did the neck tension feel like? Maybe some "hard" brass? Can you pull one of the leftovers and measure the powder charge, and look for gouging on the bullet body from the case neck? I assume casemouths were all chamfered?

What was the load that blew the primer?

Hot Core,

I got lazy with the Pre/Che that day and was not using it. My bad!

I was running a charge of H4831sc from 46 to 49.5 gr. It blew at 49 gr. No, I have no plans to repeat it again.

When I use a chrono when working up to find max powder charges, I'm looking for consistent increases in velocity then incrementally smaller velocity increases. To me, that can be a sign the ceiling is near. Especially when hitting or going over the max, my experience dictates the groups start to enlarge too.

Previous primers were flat but zero cratering "with any charge"! Their were zero extractor/ejector marks until that one. The brass had been fired 3x and was new, purchased by me.

Neck tension is tight. New Forster FL die tight! I've got another die off to Forster to have it honed out to my specs but it's not back yet. I've pulled enough bullets to 1) measure powder charges and 2) to see their are neck marks on the pulled bullets but not gouging. I do chamfer each neck prior to seating.

Alan

The Hodgdon website lists 49.0 grs as a "max" charge with a 100 gr Speer bullet and H4831. The 5th edition of the Nosler manual lists 45.5 grs of IMR 4831 as max with a 100 gr bullet. It has been my experience that you can usually get more IMR 4831 in a case than you can H4831, for equal pressures. The Hodgdon website numbers also seem to bear this out as they list a higher "max" for the IMR 4831 than they do the H4831 with that 100 gr Speer bullet.

I have not tried those Noslers in my Roberts or my Wby mag, but I can only "speculate" that the pressure comes on quicker on those Nosler's than with a 100 gr Speer. If you're getting flattening primers at .5 grs less, or at 48.5 grs, then 49.0 may have gone too far.

You could have an accumulation of issues, powder charge too high (see comments below), weakened brass, high neck tension, and a minimum spec tight chamber in that beautiful custom rifle.

I know quite a few manuals seem to list lower pressure limits on 257 Roberts loads than for similar cartridges. Much of this has been debated back and forth over the years. Some say it's only because of early custom's built on early Mausers, some say it's the brass, etc. Then there are the seperate "+P" loads

I have one 257 Roberts, and one AI. The standard Roberts is my daughter's rifle, and I haven't really tried to go beyond book on it. Recoil is a major concern with that application, so I was after reasonable performance and uniform groups more than max charges. I'm using IMR 4350 in that rifle with 100 gr Nosler BT's, so I realize my load doesn't help you any.

I use H4831sc in another caliber, and have read that the "sc" powder burns slightly faster than the regular or long cut version. Some of the benchrest shooters are claiming this. I have not tried the two concurrently to science that out for myself.

If you call Nosler, I'm sure they could give you a starting and max load for that powder in the Roberts. If you do have a minimum spec chamber, you may find you reach pressure max before "book" in it.

Also, as an aside,

Sierra lists H4831sc in their manual for 100 gr bullets with a max charge of 46.5 grs.

I realize this is extrapolating data from other bullets, but it can kind of give you an idea that you may be over max with your powder charge and the Nosler bullet.

Slim,

Just back from the range with the rifle. Was trying IMR 4350 and IMR 4064.

I called Nosler. They told me a couple of things about the e-tips in general

1. Because their a momometal their a "hard" bullet and need to be at least .05" off the lands. I was starting mine at .03".

2. They say to take 2 grains off the max from their Nosler #6 manual. Their book says 48gr is max for the H4831sc so 46 gr should have been max per their specs and I was at 49 gr; OUCH!

This am I was measuring right on the rim and didn't see anything more than .004" growth.

The bullets I have pulled were quite "sticky" and more than likely contributed to the pressure as well.

If I didn't say it before, I am using new WW Super +P brass.

I'm aiming to start them at least 3000 fps per John Barsness' statement about the smaller dia monometal bullets to achieve consistent expansion.

Alan

quote:

Originally posted by GSSP:
Hot Core,

I got lazy with the Pre/Che that day and was not using it. My bad!

Hey Alan, I've done that too.

quote:

When I use a chrono when working up to find max powder charges, I'm looking for consistent increases in velocity then incrementally smaller velocity increases. To me, that can be a sign the ceiling is near. Especially when hitting or going over the max, my experience dictates the groups start to enlarge too.

I may be WRONG, but I think Vapo likes that as well. As long as it works for you, then it is a good thing to do.

Perhaps it was the Cartridges I was using when I chronograped lots of Loads many years ago, but by the time "mine" showed erratic Velocities, normally the Primer Pockets were already looser than I prefer.

quote:

Previous primers were flat but zero cratering "with any charge"! Their were zero extractor/ejector marks until that one. The brass had been fired 3x and was new, purchased by me.

As usual, I tend to go toward a very slow approach. You mentioned 0.5gr increments previously. In this size Case, I typically go with 0.2gr increments. And I tend to use 0.3gr in 30-06 size cases and 0.5 in Belted Mag Cases. That doesn't mean I'm criticising your approach, just saying I typically go "up" on Load Development a bit slower.
-----

That info you got from Nosler about starting 0.050" Off-the-Lands with their E-Tips is the first time I've seen(or heard) about that. Same about Reducing the MAX Load shown in the Manual. That will be excellent info to pass along to other folks as you see them discuss their Load Development with them.

A buddy has a Short Action M700 257Roberts in Blue Steel. It is the "second time" he has owned it(which is a long story). But he has had just excellent on-game performance with his - as you should yours.

Oh yes, I mention it because he sent his to John Lewis to have a Weather Proof Finish put on the steel. Can't remember which finish it is at the moment, but it has protected the outer steel surfaces from any Rust, and he uses it a whole lot.

Best of luck with the rifle.

quote:

quote:
When I use a chrono when working up to find max powder charges, I'm looking for consistent increases in velocity then incrementally smaller velocity increases. To me, that can be a sign the ceiling is near. Especially when hitting or going over the max, my experience dictates the groups start to enlarge too.

I may be WRONG, but I think Vapo likes that as well.

Well....for clarification....I use a chronograph for information that I would otherwise not have. However it never is used as a pressure indicator except that we know when we're reaching velocities near factory published maximums we should expect to soon see other pressure signs and at times when I encounter pressure signs and the velocity is sub-par, I switch powders. It's a piece of information I like to have!

That's interesting about those E-tips. Kind of mirrors the characteristics of the Barnes X bullets too.

My daughter's rifle prefers 42.5 grs of IMR 4350, and a Winchester primer with the 100 gr BT's. I think book max for that load is 43.5 grs. Her's is a custom barrel with a minimum chamber set with a tight headspace. I must confess I have not chronographed that load, but pressure signs are fine.

So by Nosler's figuring, you should come in to max around 41.5 to 42.0 grs. Hopefully you're starting off around 38 or 39 grs?

Before I had my Roberts AI'd, it preferred IMR 4064 and 115 Nosler BT's. That was it's favorite powder with the 100's, and the 120 Partitions too. Maybe IMR 4064 will "do it" for you too?

Also, not wanting to start a whole new debate on Roberts loads and pressures...

The "+P" brass usually has less case capacity than standard Roberts brass due to thicker web and case body. This can make pressures come on quicker too.

As always, start low and work up. I usually go in .5 gr increments myself when I do an initial ladder test. I think in your circumstance, I would go with a "starting load" at either 37.5 or 38.0 grs and work up from there.

GSSP, I have a Bob being built as we speak. I hope it turns out as nice as yours. I've done alot of manual research on the Bob lately. The manuals vary greatly. My speer manual states that they increased their loads from the traditional pressure limits and my hornady manual specifically warns that their load data was put together using +P cases and is different than "regular" cases. From memory, 49g of H4831 seems high for +P cases. The 2008 Hodgdon manual that I keep here at the office list 49g H4831 as max load w/ a 100g speer, but does NOT reference +P cases. The 2010 Hodgdon manual still list 49g H4831 as max load, but indicates the use of remington brass. My research indicates that remington does NOT make +P brass for the Bob. Any way you look at it, blown primers indicate the pressure is too high. I would get your chrono working and start w/ 43g of H4831 and work up to 3000/3050 fps.

GSSP, also thought a/b your bullet choice and think maybe you should start your load workup at 40g---just to be safe.

Aliveincc,

Appreciate the thoughts. I've already run the H4831sc from 44 to 46 gr successfully; hitting 3125 fps. 45.5 gr gave me a 1.1" group. Something to explore further with different primers and/or seating depths.

Alan

quote:

Originally posted by GSSP:
When I use a chrono when working up to find max powder charges, I'm looking for consistent increases in velocity then incrementally smaller velocity increases. To me, that can be a sign the ceiling is near. Especially when hitting or going over the max, my experience dictates the groups start to enlarge too.

Alan

I dont think thats very safe since I cant find a reason that any given combination will show those signs at the right pressures.

quote:

Originally posted by 900 SS:

quote:

Originally posted by GSSP:
When I use a chrono when working up to find max powder charges, I'm looking for consistent increases in velocity then incrementally smaller velocity increases. To me, that can be a sign the ceiling is near. Especially when hitting or going over the max, my experience dictates the groups start to enlarge too.

Alan

I dont think thats very safe since I cant find a reason that any given combination will show those signs at the right pressures.

Watching my velocity increases is just one of many items in my little tool box of things I use to watch for pressure indicators. Not the only one.

If I only depended upon primer signs, I'd more than likely pop a primer every time I work up a load; especially with this rifle. The same with hard bolt lift, or using just one set of loading data or group size increase/decrease, etc. I watch "ALL" my pressure signs to tell me what is going on with the pressure in the respective rifle.

Please, don't anyone pigeon hole me into depending on only velocity to determine pressure.

Alan

The M70 has no particular signs of excessive pressure, other than those of all other bolt-actions. Most of the signs that pop up are due to the individual rifle...ie my .300 Mag has an enlarged firing-pin hole so shows cratered primers before the loads get very hot.
It might help a little to know what powder you're using. Also when you bought the bullets, did you get them in a bulk box, or were they in a smaller conainer.
I ask because I was doing a work-up on two 7 m/m Mags, once. The ammo was to be quite similar, so I'd load the ammo together, mark each case, box them in two different boxes, then take them to the range. I'd switch rifles as they heated. Anyway...the problem. I ran out of bullets, so went to the store and bought more. The first day was great!! That night I opened the second box, and loaded up more test loads.
The first shot was a dupe of the last load fired the day before. The gun, an M700, locked up tight. Of course that ended the range session! There was no use in tying two rifles up, until we found the problem. It turned out the bullet was a different batch, made after a new die had been installed at the factory. The ogive was SLIGHTLY different. I had seated the bullet to the prescribed OAL, but it changed the amount of "jump." When the bullets were set on end, side by side, you could see the difference.
I'm going to assume that the same powder-can was used, the bullets were from the same box, the primers were from the same carton, and weren't disturbed during the loading so you had to readjust a die or the scales.....
You seem to be a very careful reloader as you don't take just one indicator as gospel, so you know the the signs on a primer don't mean much. You could have been working with a LOT of pressure, and it wouldn't take much to go "around the bend." I'd like to know the powder, though, so I can compare with my Bob.
Have fun,
Gene

Gene,

The charge is listed in my second post, 49 gr of H4831sc.

Alan