7mm powder question.

[leadhead]

What is the best powders you guys have found to work with the 7mm Mauser?
I've been using 2400 and I can't get any of my 7mm's to shoot worth a damn.
My buddy told me to go to 4227. He said it works wonders in his 7's
Any info would be great. Thanks.

[405grain]

What bullet are you using? I've been shooting both the rcbs 7-145-Sil and the 7-168-Sp. The 145 grain is pretty good, but the 168 grain is more accurate. It's been my experience that 7x57's generally prefer longer, heavier bullets. I have been using shooters world buffalo rifle (which is virtually the same as 5744) with good results. When I want the best accuracy I use IMR-3031 with a 1 grain dacron filler to keep the powder back against the primer. IMR-4227 might be worth trying.

[racepres]

+1 on Heavy= Longer and Fatter.. If I am trying to make a lighter boolit, or a not fat enough boolit, work, I am likely to use RedDot..
4227 is pretty darn hard to beat, but 4198 is showing Promise..

[leadhead]

I have the NOE 170 gr mold.

[Thumbcocker]

3031 is showing promise very early on.

[atr]

+1 on Heavy= Longer and Fatter..

yes!
and 2400 works very well in my 7x57 loads with RRB
atr

[405grain]

OK, two things: I went on the NOE website and there appear to be four different 7mm bullets around 170 grains. Both the 287-171-RF-AP2 and the 288-173-FN-BZ3 are bore riding designs. The 287-173-FN-AP5 and the 288-173-FN-BZ3 are flat nose designs that look better suited to cartridges like 7-30 Waters. Though the flat nose bullets could be loaded in the 7x57, in order to chamber they might have to be seated low enough that the gas check and part of the bullet shank would be below the case shoulder. Hot high pressure gas can cause accuracy destroying erosion on the rear driving bands if a cast bullet is seated too deeply. (this is a general assessment, sometimes people get good accuracy even with deep seated bullets).

The 287-171-RF-AP2 and the 288-173-FN-BZ3 are both of the bore riding design. These would be more appropriate for the case neck length of the 7x57 Mauser. IMHO bore riding and Loverin design bullets are the most accurate types of cast rifle bullets. In theory, the neck of a bore rider will insure perfect alignment of the bullet with the rifles bore. If you're having accuracy issues with a bore riding design the first thing I'd suspect would be that the diameter of the bullet doesn't match the rifles bore. If you end up needing a larger diameter bullet to fit your bore, powder coating might be one possible solution.

2nd thing: Have you slugged your barrel to determine the proper diameter of the bullet. If you're shooting a Mil-Surp Mauser, the barrel may be a little oversized either from wear or manufacturing tolerance. Further, military Mauser's were issued with a cleaning rod (sometimes brass, but usually steel). Decades of soldiers cleaning their rifles from the muzzle end could have worn the rifling up by the muzzle. Check for this because if the rifling and crown at the muzzle is worn it will effect accuracy. Post more details such as the rifle that you're using, what you're sizing the bullets to, etc., and I'm sure that other members will be able to post even more tips that might help you with your accuracy problem.

[leadhead]

The NOE bullet is 293-170-FN and the flat nose isn't very big. The bore dia. is .287 and I size to .288
The rifle is a Chilean Mauser model 1912 and is in very good condition. The crown is perfect, and the
bore does not appear to be worn and very shiny with no pitting of any kind.

[405grain]

The only 293 bullet that NOE lists in their catalog is the 293-181-FN-AQ3. No worries. The main reason that I wanted to see what you're casting was to see if the bullet shank & gas check were being seated below the case neck. So long as you keep the gas check at or above the shoulder of the case, that removes one of the variables in the accuracy department. With small charges of powder in the 7x57, working in the 1300 to 1600 fps range, faster powders usually give the best results. When moving up to "mid-range" cast loads in the 1700 to 1900 fps range with this caliber, fast rifle powders usually work best. For your loads powders like Unique, Red Dot, and 2400 might be a good choice for accurate reduced velocity loads. For general purpose loads in the 1700 to 1900 range powders like IMR-4227, IMR-4198, Reloader #7, AA 5744 might work well.

The use of IMR-3031 has lots of potential and is my most accurate load, but requires a little extra work. I like to use the heaviest bullets that I have with this powder, and keep the velocity around 1850 fps. Because this is a relatively slowish powder for cast bullets in this velocity range, it doesn't have good load density. This could lead to erratic ignition which could effect accuracy. For this reason, I use a 1 grain tuft of filler to keep the powder charge back against the cases flash hole. When I make up cartridges with this charge it is for accuracy shooting, so the bullets are both visually and weight sorted. The selected bullets are all within 0.2 grains of each other.

I like the model 1895 Chilean Mauser. It's my favorite action to build small ring sporter actions on. One of the things that can cause inaccuracy with any of the small ring actions is their glacial lock time. The interval between the sear releasing the cocking piece and the firing pin setting off the primer may be only a few thousandths of a second, but it is usually twice as long as more modern firearms. There are two things that can be done to eliminate this as a cause of inaccuracy. First remove and disassemble the bolt. It's surprising how many times a rifle that's clean and shiny on the outside has a fire control group that's a ball of rust and crud on the inside. If the firing pin and spring are coated in goo, clean them up. If the inside of the bolt has dried on cosmoline and dirt in it, clean that out. Things like these could cause the lock time to differ from shot to shot as there would be drag on the firing pin. If the firing pin spring looks weak, or is covered in rust pits, it might be a good idea to replace it with a Wolff aftermarket firing pin spring. This will also help quicken the lock time.

Another thing to check is that both the action screws are snug. They don't need to be gorilla death tight; but check to make sure that one of them hasn't come loose. There are many reasons that a good rifle might not be shooting it's best. The things that I'm suggesting are just some of the low hanging fruit.

[Bad Ass Wallace]

3031 is showing promise very early on.

I use 29.0gn of 3031 with an RCBS 145gn silly-wet boolit.

https://i.imgur.com/LuRm5kSl.jpg

[leadhead]

Thank you 405grain. That is a very informative post. I've been collecting military rifles for over 40 years, and have really
enjoyed taking them apart and cleaning them inside and out. I shot handgun silhouette for 22 years all with cast bullets.
I've been casting bullets for 50 years. Most all my military rifles will shoot very accurately out to 200 yards. Don't have a
range longer than that. Thanks again, and I will be trying some of your suggestions.

[Rapier]

I shoot the 7 TCU with the 145 RCBS with 15gr of H-4227 under a compressed charge of spherical buffer. This load comes from the. Handloader Magazine Annual. In my XP-100 with a scope it shoots 1/2" at 100. Same aprox velocity with a premium 1-9 twist barrel. Doubt the problem is the powder.

Just a bit to refresh; a bore rider design (RCBS Silhouette) works well if the barrel land diameter (the bore) supports the forward diameter and at the same time, the base size fits the groove diameter (the caliber). The groove diameter can be perfect, but if the front is not supported by the lands, then, you can get front end wobble....Many cast shooters in competition, size the front then the base, two different sizings to fit both diameters.

With a military rifle, a steel cleaning rod, I would suspect the real rod to steel barrel wear is in the lands, not the grooves.
So if shooting a bore rider, both measurements are necessary and must fit the bullet.

If you have shallow lands, say just for example, .0025 per side, and the bullet is setup for .004 per side lands, you may have wobble, a worn throat can exacerbate the situation. You can check your Mauser barrel easily, by sticking a 145 in the muzzle, nose first, if it just drops in, that is not so good, it should be tight.
You might try a different style bullet if your land diameter is larger than the front diameter of the bullet. Might need to change to a style that has a much longer bearing surface to the diameter, just for example, the Thompson design with multiple lube grooves.

[Cree]

Some years back, when I knew even less about boolits, fit, and all the “usual” suspects we talk about here, I sallied forth with some unknown Gunbroker boolits (about 175 grains GC) and simply loaded them to jacketed minimums and shot what I had, which, at the time, was IMR 4064, 4350, and some 3031. I settled on a modest snort of 4350, and likely proved God loves even the most ignorant among us. It certainly wasn’t an incredibly accurate load - maybe 4 inches at 100 yards? But considering I knew nothing about fit, alloys, cleaning the copper from the barrel, and so on, the fact it grouped at all, and I actually felt good enough to deer hunt with the load (killed a late season freezer filler with it), maybe there’s some gold there for you.

It’s worth noting that load - and I no longer have that data - shot well enough in the Model 98 with the .284 bore, not the .287 of the Spanish 7x57 I had (wonder why?), but that particular gun really shines with the “right” amount of 4350 in any of the heavier jacketed or cast projectiles.

(Wanted to add, so I edited…)

In an Arisaka I had rebarreled to 7x57, with a batch of Maplewood’s boolits sized to .287, my notes show 18.6 grains of 2400 shot consistently 1-2 inches at 100. I’m not sure what charge you’re using, but many of us who use Harris’ “The Load” sort of data regarding 16 grains of 2400 have seen tighter groups with slightly heavier charges. My .308 is the only one of my cast rifles that actually prefers a true charge of 16 grains as optimal.

[charlie b]

Note that Harris does recommend tweaking the 16gn load for your particular cartridge/gun.

"Local military collector-shooters have standardized on 16 grains of #2400 as the "universal" prescription. It gives around 1500 f.p.s. with a 150-180 grain cast bullet in almost any military caliber. We use 16 grains of #2400 as our reference standard, just as high power competitors use 168 Sierra Match Kings and 4895....

Sixteen Grains of #2400 is the Universal Load

The same 16 grain charge of #2400 is universal for all calibers as a starting load. It is mild and accurate in any larger military case from a 30-40 Krag or .303 British up through a 30-06 or 7.9x57, with standard weight bullets of suitable diameter for the caliber. This is my recommendation for anybody trying cast bullets loads for the first time in a military rifle without prior load development. I say this because #2400 is not "position sensitive", requires no fiber fillers to ensure uniform ignition, and actually groups better when you stripper-clip load the rifle and bang them off, rather than tipping the muzzle up to position the powder charge. "

[leadhead]

Well, I switched over to 4227 and at 18-19 grs with a Lyman 287-308 bullet sized .286 it will put
9 out of 10 hits on a 8" steel plate at 200 yards. I think that's pretty darn good for an 80 year old.