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I couldn't get within 3 grains of loads with the 160 grainers that other guys were running. It's okay though half moa and 3180 from a 150 swift scirroco isn't too bad at all. I'm good on everything up to elk with that combo.

79: No doubt that will work...


Not sure i ever asked but what is your OAL of loaded cases?

I haven't played with a loaded round in a while but I think that I was loading them to like 3.57. My rifle Is throated for a 175 partition to 3.565 if I recall. I'm still off the lands with the 150s but that's where I found the accuracy.

You're long enough, that's for sure. Mmm....guess it's the barrel. Really not sure.

Redding had 7mm MSM dies...the S bushing dies...sitting on the shelf when I call them.
It took several months to get them because Redding was so far behind in there shipping schedule.
Not sure what its like now.
The 7mm MSM reamer my smith has is one of his very first.From 20 some years ago.Think it was one of the very first rifles he ever built.

dave

79: I'm sure you know all this,but barrels vary all over the map.

Some are tight, some are loose,some are rough and some are smooth. They have different numbers of lands,different throat lengths,different materials. Even how the lands are configured can affect how the bullet engages the lands and affect velocity.

All these variables can conspire together to increase or decrease resistance that the bullet encounters in traveling down the bore. Mix in different powder lots, bearing surface of different bullets,materials used,etc and it's no small wonder we see differences in the velocity from the same cartridge and bullet, and same load,from one rifle to another.And why we can even run into the pressure walls without getting the velocity we expect of a cartridge.

If we hand load enough, we have all bumped into this stuff at one time or another.

The one variable that seems to overcome all the others IMHO is case capacity,and even then we get into issues of pressures that we mostly all just take educated guesses at reading. But the point is that even though we don't alway get everything we want from a cartridge, we will generally get more than with any case that's smaller and holds less powder.

One chap (buddy) I know who had a Mashburn said that his 168 gr Barnes did not get the 3200 fps others seemed to be getting with 160 gr bullets.Velocities were barely over 3100 fps. I speculated that was because it only weighed 7 gr less than a 175 gr Partition,and maybe had even more bearing surface.

I never worked with the Barnes in the Mashburn but for yuks sometime, measure a 160 Partition.....it ain't .284.(or at least it was not the last time I measured one)...Hint.

That's pretty good stuff and your right, 3180 with that Swift is really a killer load. I actually like the expanded Swifts a little more than the ABs but both are really capable bullets.

I've tried 33 with the 175's and I'm still not sold they are gaining me anything over a load of H1000 running 50fps slower. My only need right now is getting a single jug of H1000 so I'm working with the same lot of powder. When I started with the MSM I had to buy 1lb'ers from where I could get them so a great load out of one jug turned mediocre from the next.

I've got another buddy that picked up a Simillion rechambered M70 off of here. He has yet to shoot it, but plans on running 7828 which seems like it should be just as good as H1000 or maybe better. I had plans of trying a bunch of stuff with mine but once I ran H1000 I sorta lost interest since it worked so well.

Chanlynn barrel is 26 inches and has a 1-10 twist.

The load is a 168g Berger classic hunting bullet with a Norma case and a Tula mag primer.Powder is H1000.

Measured 10 feel from the end of the barrel with my Oehler model 33 with a 10 foot spacing.4 shot groups except where noted..No errors on the chrono at all this session..

72g 3 shot
L.. 2970
H.. 3051
ES.. 81
A.. 3013
SD.. 40

73.5g
L.. 3035
H.. 3041
ES.. 16
A.. 3032
SD.. 6

74.5g
L.. 3083
H.. 3125
ES.. 42
A.. 3099
SD.. 18

75.5g
L.. 3118
H.. 3137
ES.. 19
A.. 3126
SD.. 8

76.5g
L.. 3162
H.. 3186
ES.. 24
A.. 3171
SD.. 11

77.5g 3 shots
L.. 3215
H.. 3231
ES.. 16
A.. 3221
SD.. 8

The 77.5g load has one case of the 3 fired,that has a very, very faint hint,of an ejector mark.Hard to actually tell The other two look fine.I knocked the primers out of all 3 and reprimed them.The one with the ej mark was just a little bit less effort to seat a primer with a RCBS hand priming tool.Than the other two.All 3 function through the action like butter with no tightness.
Im thinking a person could actually run the 77.5g load but just looking....im afraid they would open the primer pockets over time. Ashame as the 77.5g load shot the second best accuracy at 400 yards.

The 73.5g load at 400 and the 73g load at 100 were the best for accuracy.

The 73.5g load shot an honest 3 inch 4 shot group at 400 yards. Say 3032 fps with a SD of 6.

The hotter loads were all running MOA or a bit more at 400.
Conditions were kinda suckie.Wind was up pretty good.Still shot great..


dave

What powder charge with those 150s? I'm using the same bullet in my 7 WSM and am getting 3100+.

I'm at 69.5 grains of mrp with the 150 grainers. beartalker

bearstalker the people I know who are using 150's in the Mashburn are generally getting 3250 fps,or a bit more(not quite 3300) or about 100 fps more than 79 is getting with his rifle.

I got that velocity with 150's in the 7mm Dakota and the cartridges are very similar in velocity.

What mine will do with 150's I can't say as I have never fed it anything lighter than 160, unless I was fire forming.

You could load one case 10x in a row and fire it off, you'll soon see if/when the primer pockets will open. If you get to 10x and it is still holding primers satisfactorily, I would consider that load in that brass safe to go.

If I see a hint of an ejector mark.
Im done.
If its as hot as I think it is, you would not get to 10 reloads.
And I do, do that ...ie firing the same case over and over again, to check the primer pocket.

dave

Well I've got a 7 Mashburn FL die now and it looks like I'll be able to use my Hornady seater so once I get a reamer, I'll be in the game. I sized one piece of once fired Hornady 300mag brass and had significant puckering and cracks in the shoulder. I didn't anneal and will try that, but it looks like I might want to make up a intermediate form die. Does anyone have any pics of the brass as they come out of the form die(s)? I'd like to get an idea of how the shape progresses.

gzig: Don't use once fired cases to form your Mashburn brass.Start with new brass.

On the left is a new 300 WM case that has been passed through a Form/Trim die before being fire formed. A Pass through a FL Mashburn die should result in the same thing and no case wrinkles/buckling.

The next two cases are live fired 7mm Mashburn Super,fully formed. There is not much progression, other than a bit less taper for the Mashburn case.

Thanks for the pic Bob. I don't have any virgin brass at the moment but I did anneal a couple R-P cases and they came out OK. I'll get some new brass to start with when the time comes. Do you or any others have a favorite brand? Any that form better or are more uniform than the others?

gzig: I only use WW. Others I know use Norma and Hornady as well.

Those using Norma have had a donut issue but resolved it quickly. I have not run into it with WW. Hornady is fine too.

Honestly they all work.

Annealing helps with any of them. Will prolong case life.

Tried to run a new piece of brass through my FL dies and it didn't quite form it enough to get it to chamber. Guess Im going to have to invest in a forming die since the 100 pieces I formed with Dobers dies have just over 700 rounds on them so they are almost on their last leg.

Laker: Are you camming over with the FL die?

Set it up to contact the top of the shell holder with the ram fully up. Then, turn the die down another 1/2 turn (maybe a bit more). Run the case in and until you feel contact and then lean on the handle and you will feel it "bump" down further.

They should chamber fine.

It had been a couple of years recently since I had to make any new brass, and I forgot to do this myself. Got to the range with a bunch of COW loads and nothing chambered.

I knew right away what I had done, so took them home and cammed them all over. They now fit fine.

I tried that Bob but it still wasn't quite enough. I may have to play with it some more. I still may end up buying the die anyways. Wife has basically taken my mashburn now anyways so I might be building myself another one this spring