7mm Mashburn Super 175 PTs and RL33

[SJB358]

Well, I decided to try the 7mm MSM out with some RL33. It digests those heavy charges of slow burning powder so darned well.



Thats 84 grains of RL33 in the case...





I did some shooting a few weeks ago with 81, 82, 83 and 84 grains of RL33, reformed Hornady cases.

81



82



83



84



So initial accuracy wasn't too bad. Speeds were pretty consistent across the board yesterday as I crept upwards. I am not including the groups with RL33 as they were LARGE with the MagnetoSpeed on the muzzle.



So, I am not sure if I am going to stick with my H1000 load, or pursue the RL33 at around 3100.. That 175 PT at 3100 would be some BAD medicine up on the elk mountain!..

Also, which way would you all go for tuning the 175 PT? Towards or away from the rifling? Just asking as I am thinking of lengthening back out to get back around .010" or so. The current seating depth works excellent for the H1000..

 

[Dwh7271]

I'd go toward.
Had to on the 338-06 and it tightened right up

 

[JD338]

Scotty,

Usually seating the bullet deeper will walk the group in but getting closer to the lands with a PT is always a sure bet.
If loaded to the Max magazine COL, how far are you from the lands?

JD338

 

[SJB358]

Scotty,

Usually seating the bullet deeper will walk the group in but getting closer to the lands with a PT is always a sure bet.
If loaded to the Max magazine COL, how far are you from the lands?

JD338

Jim, I am not 100% sure, as the rifle was chambered for a 160 AB at 3.605" COAL. I know I have plenty of room to move out towards the rifling and still have plenty of room in the mag.

Dewey, I will remeasure when I can next weekend and try to get some lengths if possible.

 

[DrMike]

I like the PT up near the lands. Man, that MSM is a beast. Gotta' deliver a whomp to whatever is shot with that cartridge.

 

[SJB358]

I like the PT up near the lands. Man, that MSM is a beast. Gotta' deliver a whomp to whatever is shot with that cartridge.

Me too Mike. I think I will try it stretched out some and see what happens. Got nothing to lose and a little bit of speed to gain...

 

[TXbaldhunter]

Nearly the same velocities I got with 76.5grs of Reloader-22 on some test loads in my 7STW.Have you tried Reloader-22? It makes my 7mag and 7STW really accurate and easy to load for.

 

[BF375]

Looks like RL33 is another powder that will work well in the Mashburn. Interesting that charges seem to be 8-10 gr heavier than H1000 with the 175,depending how hard you want to lean on things.

I bet 33 would be really good with those big long 195 Bergers and similar bullets.

I started loading 73-74 gr H1000 in mine for 3075 with my original lot. Recent lots lost about 100 fps. and velocities were 2980 or so. This is one nice thing about the Mashburn...you can lose 100 fps and you are still at the velocity level of a hot loaded 7 Rem Mag maxed out.

Great case design.

 

[OU812]

Scotty looks like a great start. If it were me I'm not sure I would tweek seating just yet, at least not until I tried some powder charges of .2 increments. Those 175 partitions will wreck an elks day.

 

[IdahoCTD]

Kirby Allen did some testing with R-33 and found the ES/SD was best within about .010" off the rifling. I shoot my 30-338 Norma Imp at .007" off and it is so accurate it is scary. Granted that is with 230 Bergers but I would try .005 to .010" off to start with and move away from there. I would think R-26 would work well for that case as well.

 

[SJB358]

Kirby Allen did some testing with R-33 and found the ES/SD was best within about .010" off the rifling. I shoot my 30-338 Norma Imp at .007" off and it is so accurate it is scary. Granted that is with 230 Bergers but I would try .005 to .010" off to start with and move away from there. I would think R-26 would work well for that case as well.

Great info Nathan. I'll move them up and give them a try up close. Figure I'll try a couple seating depths with the 83 grain charge. If nothing seems to pop up, I've got a good backup load running H1000 at 3050'ish. I'm not sweating it too much. I do have some 26 as well, but unless it's real accurate I'm not sure if it'd beat H1000 speed wise.

 

[SJB358]

Those 175 partitions will wreck an elks day.

That is the ultimate plan Bill. If I can get them to come together I'd like to run them. At 3100 they really carry the freight...

 

[IdahoCTD]

Anything slower than H-1000 should get higher velocity in that case. R-26 is slower and tends to get good velocity (Retumbo too for that matter). H-1000 is a really good powder and usually gets phenomenal accuracy but most of the time it's not the fastest. People just use it for the accuracy and consistency. R-33 gets amazing velocity in slightly overbore cases but isn't always as consistent or as accurate as H-1000. It's close most of the time though. If a person isn't worried about shooting long range then the additional velocity is a good thing as the slight loss of consistency isn't missed nearly as much at limited distances. The accuracy can be so close between the two that most people would never notice it. I also bet N-570 would rock in that case but it's expensive and not very easy to find. VV went almost 3 years between making batches of N-570 in the great component crisis.

One example is my 338 Edge. With 89grs of H-1000 it shoots in the .1's at 2820fps and ES's under 10. With 99grs of R-33 it shoots 2990fps in the .1's but extreme spreads are up near 20fps. With the velocity comes a pretty good rise in recoil though and the R-33 load is definitely a hotter load but the Bertram brass I shoot takes it.

 

[BF375]

Anything slower than H-1000 should get higher velocity in that case. R-26 is slower and tends to get good velocity (Retumbo too for that matter). H-1000 is a really good powder and usually gets phenomenal accuracy but most of the time it's not the fastest. People just use it for the accuracy and consistency. R-33 gets amazing velocity in slightly overbore cases but isn't always as consistent or as accurate as H-1000. It's close most of the time though. If a person isn't worried about shooting long range then the additional velocity is a good thing as the slight loss of consistency isn't missed nearly as much at limited distances. The accuracy can be so close between the two that most people would never notice it. I also bet N-570 would rock in that case but it's expensive and not very easy to find. VV went almost 3 years between making batches of N-570 in the great component crisis.

It's true that slower powders will give a bit more velocity than H1000.

When a friend and I built our Mashburns 5-6 years ago we worked with RL25,7828,and Retumbo, in addition to H1000. All delivered fine accuracy (both Krieger barrels,24"). Either Retumbo or RL25 delivered 3250 with 160 gr bullets;one experimental load with Retumbo gave over 3300 fps with the 160 AB,but I considered that over the top.

My goal for the cartridge was always 3200 fps with the 160,and 3050-3100 with a 175. Any of these powders would deliver that and more but since we were working with a wildcat whose velocities were established some 50-60 years ago,we felt those velocities would keep us on the safe side.I personally think that 3250 with the 160 has the cartridge pretty well maxed out for safe, trouble free hunting loads

So, I settled on H1000,and 75.5 gr H1000 gives me right on 3200 fps with the 160 NPT, 162 Amax, and 160 BBC.I can use all three bullets pretty interchangeably to normal hunting distances. Accuracy with the 160 NPT and 162 Amax is good to 600 yards.

As Scotty is showing here,new powders like R33 may be capable of even more. If I were running bullets like the 195 Berger or 180 Scenar, etc etc, I'd be inclined to give R33 a good run. Another friend from NM is using the 195 Berger with H1000 but his barrel is 27" I believe. His velocities are in the vicinity of 2960 or so.

 

[IdahoCTD]

I don't doubt his velocity would crack 3000fps with R-33 and 195's. R-33 shines with the heaviest for caliber bullets too. I really think R-33 is best in the cases where H-1000 isn't really practical (meaning it's not slow enough). So something a little more overbore like a 28 Nosler, 7RUM, 300RUM (or my 30-338 Norma Imp), etc.

I don't shoot it in my 6.5-300wm but that is only because my Retumbo load is so accurate it's scary. R-33 gives 70-80fps more velocity and is close to the same accuracy but I will almost always give up a bit of velocity for accuracy. Last year the Retumbo load shot a 3 shot group at 950yds that was 1 7/8" high by 2 3/4" wide. Needless to say I don't waste barrel life looking for a better load.

 

[SJB358]

Great intel fellas. Appreciate all the comments. Looking forward to trying R33 a little more. Shouldn't take much to see if it'll shoot. I do love the cartridge though and with a realistic 600 max range for me, I'd love to see that 175 whooping along at 3100... Thinking it could hunt this year too!

 

[gerry]

You have a couple of great loads with H 1000 don't you? I seem to remember your 160 gr AB being a great load but can't remember if you had a good load with the 175 gr PT or not. I do like that long neck on the good old 7mm Mashburn, much better than a lot of new rounds with short necks.

 

[preacher]

I found both R26 and R33 to be the easiest load workups I ever did in a 7mm Rem mag. I like the R26 with the 160 and R33 with the 175. A good Fed 215M sets them off perfectly, even in compressed loads. I like both powders immensely! Some day... I too could end up with a Mashburn Super mag when I get tired of playing with this Rem mag, ha

 

[BF375]

Preacher if you think the 7 Rem Mag is "easy" wait until you get a Mashburn... :wink:

 

[SJB358]

Preacher if you think the 7 Rem Mag is "easy" wait until you get a Mashburn... :wink:

Amen... Easiest big capacity mag I've messed with. Pretty easy to make one of them as well with a good 7mm Rem already too 8)