7mm SAUM - case pressure - bolt head marking brass

[bartman007]

Hi All,

Just wondering if others are experiencing similar issues to me.

I'm running Berger 180's close to 3000 fps in a standard 7mm SAUM chamber.

I find the bolt lift a little heavier than normal. What is normal for me is 308Win or 6mm BRX, which opens easily!!!

When looking at the base of some cases, they are losing a little brass, as the bolt rotates to extract them. The brass is new Norma 300 reduced to 7mm.

Maybe this is due to the first firing? I haven't reused the brass yet, to know if the problem goes away.

Currently using around 60 grains of ADI 2213SC which is equivalent to H4831, in a 32" barrel.

Regards,

Bartman007

 

[wooger]

I had exactly the same issues with the same components. I settled in on 59.4 grains of 4831, which gave me 2900 fps in a 28" barrel, and this load exhibited pressure as well. Brass developed loose pockets around 5-6 firings. I backed the load off to 2800 fps and won my last match with the new load. The difference in windage was 1/4 moa at 1000, I've decided that the extra speed is unnecessary for me.

 

[bartman007]

Thanks Wooger.

Interesting finding, I wonder who else has experienced this too?

I've been told, and from results to date, just under 3000fps is a conservative speed to be running at. The primers don't flatten much, so I felt that I had a good load.

I've heard of others running well into the 3000's, however I don't know what they are experiencing with bolt lift and potential case head issues?

Hopefully other shooters have further advice. Maybe a different powder, or even lube on the base of the cases or bolt head face. Might be all it takes to eliminate the sticky lift.

Cheers.

 

[wooger]

Slower powder solved the problem for me but 4831 shot the best in my barrel.

 

[jraney]

not to steal or change the subject but i was looking at this cartridge earlier today in my hornady reloading book, and was wondering how does it compare to other short actions. are there any you would trade it for if you could? how effective is this round at long distances? any info would be great, the book gave just a short description.

thanks
j

 

[TonyR]

Try IMR7828SSC if you are getting stiff bolt lift with H4831. IMR7828SSC will lgive pretty much the same speed grain for grain but you can load more grains without pressure signs. Norma MRP and VhitaVouri N560 are another possibilities for higher speed with less pressure but more temperature sensitive.

 

[Steveb]

I don't shoot a 7 SAUM but do shoot 300 SAUM. I had the same issue with my 300 shooting Remington brass. I started using a load that was well below the max listed in the books. I ended up destroying about 1/2 my brass within 3 firings with the primer pockets opening up quickly. I had to back off the loads just to save the brass. This brass is very soft and the manufacturer doesn't seem to matter. Steve

 

[bartman007]

Thanks TonyR.

I was hoping this might be the case. I'll run some slightly slower powder, and see how that fairs.

On a different note (Steveb), how does the 300 SAUM compare when shooting the 7mm 180's to 30 cal 200+'s?

 

[Steveb]

Hi Bartman

I shoot pointed 210 Berger VLD's only. Here are my observations from this summer's matches.

Slightly more recoil but nothing to cry about. Seems to hold verticals better and be more stable in heavy winds compared to the 7mm's I have shot against. The barrel (1 in 10) doesn't foul as much also compared to others I talk to. For example, I can shoot a whole weekend match without cleaning and still hold "V" at 1000 on the last relay.

The drops are identical to a 284 shooting 180's out to 900 yards then the 1000 yard relay is about 2 clicks more. Wind drift is better.

I shot against a few 7 SAUMS / 7 WSM's and won so I would say that you are in the ballpark wind drift wise to where your bullet placement judgements are the determining factor as to the winner of the match rather than the cartridge used that day.

Also, the barrel life appears to be a lot better. I have 1800 rounds down the tube and it is still shooting very well.

Just my opinions from this year.

Steve

 

[bartman007]

Steveb,

Barrel life....I'm yet to see what I'll get. 1800 rounds is a great count to get to and certainly a reason to have a look at 30 cal. However, I've heard of enough 284W guys that exceed that count with moderate loads. I'm hoping that with moderate SAUM loads, that I too can get up around the 2000 rounds mark. Watch this space

As for primer pocket expansion, I gather the heavier 210 gn projectiles would add to the damage. For that reason alone, using the same case for the 180 gn 7mm projectiles should give me better case life, if I don't abuse them with too much powder!

After all, with the amount of effort each case requires in turning and trimming and resizing, you don't want to be doing that too often.

Cheers.

 

[1KBR]

I,m running 59.8 H4831sc which is right at 2940 fps in mine with a 29" barrel. This load is very accurate and consistant. It is warm, but not too hot. I only have a 4-5 rounds through each of my 100 cases, and primers are starting to get easier to seat, but not falling in. It holds good consistant verticle, with no big changes between foulers and the 25th shot (most I have fired between cleaning). There is a very slight ejector hole mark in the brass, but I dont think the mark is from any of the recent firings, only the 1st and 2nd shot through each case, when I was chasing more speed and when I was jamming bullets.
Barrel is a Broughton, what is your barrel?

 

[Steveb]

Hi Bart

We pulled my barrel yesterday for inspection and if appears that although the barrel is getting worn there is still lots of life let in the throat. It is badly worn for about 3" but still viable. Barrel life then estimated to be beteen 2000 and 2200 rounds we guess which is great for a short mag. This would put it on par with the straight 284.

Steve

 

[bartman007]

Hi 1KBR,

Thanks for the feedback. Concerning that after 4-5 reloads that the primers are starting to go in easier. Hopefully they don't get too much easier! I know I struggled to seat some Federals on my cases at the start. I was hoping to get 10 reloads at least out of the cases, as the 308W Lapua cases seem to last forever.

I'm using a 32" Krieger straight profile.

Steveb, good news on your barrel condition.

I wonder, if the primer pockets get too loose, maybe I can use a little Silastic to fill the gaps