Hi Guys

Here is a pic of two sets of 458 Lott Cartridges fired yesterday


Top row are 320 gn banded copper with 75gn RL15
Bottom Row 500gn Hornady Interbonds 75gn RL7
Primers are Federal Match grade Magnum.
I presume the deeper indentation in the top row is because the breach pressure is lower?
What do you think?

Mark

I think the pressure on the bottom row is too high and the primers are clearly flattening. I like the looks of the top row far better than I do the bottom row. IMHO.

The primers in the bottom row are clearly close if not at max pressure. Were they handloads I'd probably back off a hair and check a case fired at least five times to make sure I wasn't making loose primer pockets.

The top row appears to be a lower pressure load.

2 different brasqs makers .. this is always going to be tough to compare loads

what mike said...
top row may be fine, bottom is past my comfort level/..

pop out 1 primer each, and look at them side on .. the bottom ones will clearly have a "rim"

too hot, change powders... and if shot in a faster twist rifle, it would probably smoke a primer

I agree that the 500 gn load is too high a pressure.
Two options
1. Go for a slower powder like RL15
or
2. I think the jacket on the interbond is a very hard gilding metal. Would 500gn woodleighs be better. I have the monolithics sorted but a standard RNSP in lead copper might keep the PH's more in their comfort zone?

Mark

It may just be the artifacts in the photograph, but the primers in the top row seem to have a bit of cratering around the firing pin impression.

George

quote:

It may just be the artifacts in the photograph, but the primers in the top row seem to have a bit of cratering around the firing pin impression.

I tend to agree with George. I think both loads may be just a tad "warm". I would drop back maybe a grain or so and reshoot.

Geronimo

Hi Mark
Both rows show pressure signs but the real way to find out is chronograph the loads. The cratering is a sign of pressure as well but the flattening situation can be caused by improper headspacing in some situations. The chronograph is your best safety factor.
Take good care,
Dave

In my opinion and experience, the top row indicates relatively low pressure. Looks identical to my low pressure 458 lott loads. 75 grains of RL 15 should be a moderate load with the 320 gr bullet.

The bottom row looks ok except for 2nd from the left. I would be asking what was different about that load? 74 gr of RL7 would normally be considered about max for the average rifle. Were the powder loads measured individually or through a measure. What's the varience. I would agree that backing off a grain would be advisable for this load.

Phil

Correction to the previous post, the primers in the bottom row look normal except for the 2nd from the right.

Measure the belt on the bottom row and compare to new brass diameter. That should tell the story.

Bottom row second from right looks a little scary. When you're at max any little difference can show up.

The top row is a different manufactured brass. You may not be able to use the same load in the 2 types. The bottom row 2nd from right does seem to have more pressure signs as pointed out by PRW.
There does seem to be a slight amount of cratering on a few of the top row ctgs. Should probably back off a bit on your loads. A chronograph will let you know how your loads are doing. Weigh the 2 types of brass to see if there is a difference in the weight. There does not seem to be any other pressure signs such as a shiny spot from the ejector. Measure the area at the belt to see if there is any signs of case head expansion.
Good Shooting

HI Mark
If your up to a little experiment. Weigh some cases so they are all the same weight ( inside volume should be the same). Make up the exact same powder charge you had for the bottom row or a little bit less to be safe and use a different primer for each case. Try the Fedral 215 magnum, Winchester mag, CCI 250 etc and see what you get for primer inspection after. You might find it interesting.
Take good care and Merry Christmas
Dave

Why use RL-7 with 500gr, you use the RL-15
with heavier bullets, and you use more of it
and you get more velocity and you get
LESS PRESSURE doing it.Ed

The Hornady cases look a bit on the hot side. I'll second Ed here and recommend a slower powder for the application. RL-7 is pretty fast for a Lott.

............without a Chronograph , you may only be getting 2150 with the bottom loadsand if you back it off you may be down to 45/70 velocity ...To me the bottom row look like a factory load . ,,that is what Hornady 458 lott 500 gr factory ammo look like when fired in my CZ ........You need to use a chronograph .......

I agree- looks like factory, and for shame
probably performs the same. Most factory
stuff engineered by ..... well I'd better
not say...Ed

Gotta tell you guys something. Primer reading is nota very reliable measure of pressure. The primers may look flattened due to the guns headspace and have absolutely nothing to do with excessive pressures. Slightly enlarged or oblong firing pin holes in the bolt can cause what looks like cratering etc. Miking the belt can be erroneous if the belt dimensions are onm the loose side( i.e. Weatherby). Personally I judge pressure by using a pressure guage ( and thats a relative measurement also) or simply by reloading a case five times and checking for hard bolt lift and primer pocket loosening. If I hit either of those two signs, I quit and back-off. I do look at the primers, but keep the facts I posted above in mind. BTW MBOGO 470 is very correct in that you might be surprised at just how much cases vary in internal volume even from the same batch. Something every match shooter knows and deals with.-Rob