7mag Magic!

[Dean2]

What kinds of loads were you using? I've run 72.5 gr of H4831sc in mine behind 140gr accubonds for 3420fps out of a 24" Stainless Remington barrel.

Do what you like but that is at least 7 grains, or 11%, and 350 FPS over any published load data for any cup and core bullet. Have you ever bothered to measure your case head/belt expansion.

From Hornady's web site:

One of the first rules of handloading is to always follow the approved reload data. The cautious reloader gradually works up to approved maximum loads to ensure his particular gun does not show pressure signs. Generally this is visual observation of the fired shell case head and primer. There is another slick way to check for pressure signs if you are interested.

Using a blade micrometer that measures in ten thousandths (.0001″), new, unfired cases can be gauged before and after firing to determine reasonably accurate maximum loads. Micrometers measuring in thousandths (.001″) are insufficiently accurate to perform these measurements, and should not be used. Previously fired cases cannot be used accurately due to various levels of brass hardening. Measurement is taken just ahead of the extractor groove on the case head and must be taken at the same place on the case before and after firing. By placing a small mark on the case head – entering the cartridge in the chamber with mark at 12 o'clock – a consistently accurate measurement can be taken with each firing.

Lower pressure rounds, like the .30-30 Winchester, usually yield maximum pressures at .0003″-.0004″ expansion. Modern cartridges, like the .223 Remington, will show maximum pressure at .0004″-.0005″, while .308 Winchester, .270 Winchester, etc., typically yield .0005″-.0006″ expansion at max pressure. Magnums, like the .300 Winchester Magnum, show maximums at .0006"-.0007" expansion, and should be measured on the belt.

In conjunction with these measurements, case head signs of pressure should be monitored as well. These signs include very flat primers, slightly cratered primers, ejector marks on the case head, and stiff extraction. All these case head signs indicate high pressure, and loads should be reduced until these signs disappear.

As always, start with the beginning load listed, and cautiously work up to the maximum shown for that set of components, using the methods listed herein.

 

[Reemty J]

Is N560 any easier to purchase than RL26?

 

[RockyMtnMT]

What kinds of loads were you using? I've run 72.5 gr of H4831sc in mine behind 140gr accubonds for 3420fps out of a 24" Stainless Remington barrel.

Rl23 has been a go to in the past. Similar to your load for velocity.

 

[RockyMtnMT]

Is N560 any easier to purchase than RL26?

Yes

 

[Buckys]

The guys at Gordon's Reloading Tool have been doing some pressure testing with the Hammers. Initial testing sxs with various lead core bullets of similar weight, loaded to touching the lands show nearly the same initial start pressure. According to them this is unusual for a mono bullet. Once the bullet is fully engraved and heading down the barrel the pressure drops off faster than a typical cup and core. More testing to be done to try and figure out exactly how the Hammer Bullets relate to engraving pressure. I did run this load past them and the consensus is that it is stout but not alarming.

I would be interested to find out what they come up with. Any communication with GRT on when they might be ready to publish updated models for Hammers?

 

[Mike6158]

****, I don't see how that's possible. I'm running the 146 hammer at 3400 out of my 7 RUM with ADG brass. I'm on the ragged edge of pressure. Some case show a faint ejector mark and others dont. Granted, it's with N570, not RL26. I can't use RL26. It's too temp sensitive for this Texas heat.

I guess I'll stick with H1000 then (7mm Rem Mag not RUM).

 

[RockyMtnMT]

I would be interested to find out what they come up with. Any communication with GRT on when they might be ready to publish updated models for Hammers?

No date. All I can say is first round of testing is done. Basically they are testing the range of 7mm Hammer Hunters. This should provide data correlating number of drive bands and start pressure as well as pressure curve. Once done GRT should be a good predictive tool for loading Hammers.

The good news is Hammers will show a bit less pressure than conventional lead core bullets of similar weight. So using published start loads for similar weight conventional bullets will be nice and mild to work up from. Between Nosler and Hodgdon data we can usually find a start load for a given Hammer Bullet and a suitable powder. Sometimes we will reference Alliant data or others to find a start point for a particular cartridge and powder choice.

 

[VinceMule]

I have been in two ballistics labs. They have different barrels/guns to pressure test with. Each gun/barrel has a different bore dia, and different throat lengths, with their lot number of powder, primers, and bullets. Bullets shot may have different pressure rings and this can vary over time as bullet-making dies wear, the bullets get larger in dia.

So, the info in loading manuals is meant to be a guide as to max loads in THEIR barrels and components. A reloader has to know this simple TRUTH!

Brass starts showing signs of serious failure around 70,000 CUP, I don't need pressure testing equipment. Also, educate yourself on which actions and designs are the strongest.

 

[RockyMtnMT]

@Blackdirt Cowboy I want to add that we have never been able to get out of the 7 rum what you would think should be possible. The 300 rum is a fantastic cartridge and the 7 rum has been underwhelming for us. It doesn't make sense to me.

 

[Dean2]

I have been in two ballistics labs. They have different barrels/guns to pressure test with. Each gun/barrel has a different bore dia, and different throat lengths, with their lot number of powder, primers, and bullets. Bullets shot may have different pressure rings and this can vary over time as bullet-making dies wear, the bullets get larger in dia.

So, the info in loading manuals is meant to be a guide as to max loads in THEIR barrels and components. A reloader has to know this simple TRUTH!

I agree. I also know Barnes monometal have published loads that are both faster and use more powder than cup and core. I also, from what I have read, believe you can push Hammers a bunch faster than cup and Core, safely. What I do not believe is that you can SAFELY get a 140 grain cup and core bullet like an Accubond, to go 3450 fps, 350 fps faster than any published data anywhere. I have seen variation in the 50 to 100 fps around the max published loads before case head expansion hits the limit, I have NEVER seen 350 FPS, nearly 12%, faster. Even an STW can barely hit that velocity with that bullet.

 

[Longtine88]

If I don't have RL 26 for a load I use N560

Or N565. They has been several runs of N565 in the last week. And N565 is more temp stable. It will be in between the RL26 and H1000

 

[Longtine88]

@Blackdirt Cowboy I want to add that we have never been able to get out of the 7 rum what you would think should be possible. The 300 rum is a fantastic cartridge and the 7 rum has been underwhelming for us. It doesn't make sense to me.

Rocky what about a 28 Nosler with it? I'm guessing warp speeds? Heck I may try that when I get home later

 

[RockyMtnMT]

Rocky what about a 28 Nosler with it? I'm guessing warp speeds? Heck I may try that when I get home later

We have loaded quite a few 28n's. The 143g Hammer Hunter is my favorite combo. With n570 we typically get a bit over 3600 fps. Other powders have always been about 100 fps slower.

That is why this load development with the 7 mag is so extraordinary. It puts it squarely in the performance of the 28n!

 

[shinbone]

Just throwing out a couple of related data points; for a 130gn Absolute Hammer in a 28 Nosler with a 26" barrel, my max velocity for various powders were:

N560- 3879
7828SSC - 3709
N565 - 3771
RL26 - 3775
H1000 - 3740
Retumbo - 3583
N570 - 3762

For a 28 Nosler, I would guess that a 130gn AH would be close to the "king of speed" without going to a super light bullet.