Short Barrel Loads?

[tinkerfive]

Another board member has me thinking about that 19" 7MM Mauser barrel that I bought a while ago.

Then earlier today I realized that I have an 18" cut down 7MM Mauser barrel too.

 

I was wondering if anyone else who's built one of these and reloads has been able to figure out

a load that gets the most out of the 19" barrel while at the same time keeps muzzle blast to a

minimum?

 

If you've ever fired 7.62 X 54R from the 38 or 44 Vs the 91, I think you'd understand what I

would like to avoid.

 

Tinker

[Jimro]

Hmm, well I'd start by trying fast powders like IMR 3031 or Win 748. A quick powder under a medium bullet loaded for accuracy seems like the best bet for a handy deer rifle.

 

I don't remember whether your action is a 98 or not, but as always load up with caution.

 

IMR lists this as their max load out of a 24" bbl.

 

145gr SPR SP; 38.0gr IMR 3031; 2530fps; 46,000 CUP; Case Rem, Primer Rem 9 1/2

 

If you lose 25fps per inch of bbl length you are looking at 2380fps out of an 18" bbl altho in the load workup I'd just quit when the group gets tight. Accuracy is more deadly than velocity

 

This is just my best guess, so as always take it with a grain of salt

 

Jimro

[gun nutty]

My understanding is that , for "high velocity" cartidges, the same loads that give optimal velocity for a long barrel will also give optimal velocity in shorter barrels.

 

One issue with optimal loads is report and muzzle flash. And let's not forget recoil due to the lightened firearm.

 

Switching to a faster burning powder may not increase velocity, but it helps in mitigating the above three factors above.

 

I used to be very concerned about maximum velocity; now I mostly focus on target performance.

 

I'm a BIG fan of RL7 and 4198. VARGET and 4895 might also be good candidates. All should reduce blast and report.

[Doble Troble]

I use Accurate Arm's version of 4895 - AA2495 'cause its a few $ less than the IMR and I'm cheap.

 

This shoots the 7 x 57 really well in the short barrel with minimal flash and no unburnt powder. Another reason I like this powder is because its really clean.

 

I use 41.6 gr of it with the bulk 140 gr Remington Coreloks from Midway that also USED to be cheap before the recent price escalations (they're still relatively cheap). This load does ~ 2600 fps out of these barrels. It's been a good load with multiple rifles made with these barrels.

 

I've been experimenting with OAL and find a bit of accuracy improvement when seating these to 3.110", rather than to the cannulature which puts them at about exactly 3.000". The chamber on my 1891 takes these bullets at 3.120" into the lands. I tried seating some at 3.120" and got some fliers - probably due to variable ramming into the lands - so backing off a bit was important to me.

 

In addition to the long throat, another thing to keep in mind with these barrels is that they're relatively fast twist - I think I read somewhere 1 in 7.5" (I haven't verified this).

 

I've got another Mauser carbine, an FR-8 in 308. It really likes 4198. It's very accurate with that powder but velocity suffers.