chasing a rainbow: mauser project

here's an update on my mauser project. the money issue has reared its ugly head, so my vision for this project has been altered, at least for the forseeable future. i've decided to see if i can turn this beast into a dedicated brush gun for this fall's black hills hunt, in addition to being a test-bed for experiments.

at the start, the gun weighed 11.75 pounds w/ its 29" barrel, full length stock, scope, etc. and chambered to 8x57:

a fresh crown to establish baseline accuracy:

this group was average for the gun in a sporterized-as-issue condition. you can see in the photo the flyer the gun dropped... this was a shot #3 flyer, and happened in every group. the 5-shot average was 4.6", and if i discounted shot 3 in every group, it would average 1.8".

removing the handguard and front barrel band improved accuracy a little, but not near as much as i had expected. the gun still showed a tendency to drop shot #3. averages were 4 shots in 1.7" (a .1" improvement) and 5 in 4.2" (a .4" improvement):

through the 29" barrel i averaged 2479 f/s, a sd of 17, and an extreme spread of 64.

also, the guns (in)ability to shoot well led me to believe that the bedding is poor, and the barrel could probably stand to be floated. however, i also hypothesized that in the 8x57, a 29" barrel was absolutely uncalled for. the cartridge's (lackluster) performance in this gun led me to believe that i could probably make everything better across the board by shortening the barrel. i figured the shorter barrel would eliminate some of the whip that was probably magnifying problems w/ the bedding, and i also figured i'd lose nothing, performance-wise, by going to the shorter barrel. so, off to the gunsmith... while the gun was there, i lopped the muzzle end of the stock off to closely approximate a savage youth gun dimension since this barrel will ultimately wind up at 19", and i wanted to get an idea of how the proportion looks before i order a 'real' stock:

cutting the barrel to 24" saved me 5 ounces on the barrelled action. removing the handguard and both barrel bands accounted for 4 more ounces, and cutting the stock off accounted for 9 more ounces.

now we get to the interesting stuff. the 5" shorter barrel averages 2460 f/s (loss of 19 f/s), 15 sd (improved by 2), and 36 es (improved by 28). the groups improved too... now i get an average of 4-shots in 1.4" (improved by .4" over the start), and 5 in 2.3" (improved by 2.3"):

the gun still throws the 3rd shot, but note the shot now flies high. i think this emphatically underscores the idea of barrel whip, and my idea that the shorter barrel will be remarkably more accurate.

so... what's next? well, i am going to test firelapping next. i have the first 30 loads assembled, and ready to go. after that, i will probably try to quantify glass bedding, then free floating (i like to bed before floating). the next step will be a titanium firing pin in an effort to quantify its effects, if any. the last step will be to lop the barrel off at 19" to get concrete data on how much more accurate the shorter, stiffer barrel really is. i also want to see how much performance 5 more inches of barrel will cost. i think the next cut will hurt a little more. i am down to 1 case of matching lot # ammo on this thing, but i think i can make it go (for my averages, i shoot 7 groups of 5 per outing).

the ultimate goal is going to be to come in at a max weight of 8 pounds, and shoot no worse than 1.75" for 5 shots (at 2.3 right now). bear in mind that this is an 83 year old military surplus gun and will be used in the black hills of s.d. where a long shot will stretch 30 or so yards.

we'll see what the next step brings...

I`m interested in the forearm pressure as well.Dakota when I refinished the stock on my 270 I free floated the barrel.The accuracy went to crap.After a dab of epoxy and a lot of tinkering at the tip of my stock I got it to shoot like it always had.Good learning experience for me.I never thought something like that would have so much effect on barrel harmonics but it did..

That oughta be a good brush rifle for sure Dakota.What bullet are you using in it?

That's a 5-Star post dakotasin!  Lots of good information.

Things I thought especially interesting were:

1.  5 inches of barrel removal equated to only about 20 FPS velocity loss

2.  5 inches of barrel removal equated to better groups.  I'm thinking along the same lines as BEAR that there might've been a rough spot near the muzzle and you removed it somewhere in the 5 inches of barrel you took off!

Should be interesting to see what bedding/free-floating will do. 

Do have to ask what kind of ammo you using?  Handloads?  Mil-Surp?  Just curious as to how you're keeping ammo consistent with these tests.  Knowing you however, I'm sure you've got that base well covered.

Can't wait to hear more! 

I know with a heavy test barrel in a mechanical benchrest, if you shoot a group, then just lay you finger on the barrel as the next group is shot, the group will move up to an eigth of an inch. This is with no pressure, just the finger touching, affecting the harmonics. Weirdly enough, in an enclosed firing test range, you can shoot a group, open and close the door, and the group will move again. That is just from the pressure change in the room. Between this type of variables, along with case neck tension, and seating depth, it's a wonder we ever get any of these firearms to shoot decently!

GREAT post dakota,... very good information here !

I've got a 7.7 Jap Arisaka that I'm going to start working with again,.. I started 2 years ago but it got pushed to the side for some other project. I also started with the muzzel,.. took off about 4 inches but needs to be re-crowned. It's now in a Fajen stock and I need to pillar bed it.

After reading your post,... I've got some jucies flowing again to get back to her. Thanks for the incentive I needed.

the sierra should shoot mucho good-o, too.

nice to see the s&b factory stuff is shooting pretty well. every time i have tried it, though - even in rifles that i KNOW are consistent with a given variety of loads - fliers erupted. you might want to try a different brand - mil-surp or commercial - before doing much more tuning.

chamberings include 65.x55, 7.62x54r and .303 british.