Twist rate in 7X57

[hornady]

I have several Mausers two are in 7 X 57 one long and one short rifle. The long shoots my Lyman cast 135-grain cast bullets great. However the short rifle has become maddening. I have done every trick in the book and can not get the bullet to stabilize in the short rifle. I finally gave up and ordered the Lyman 160 Grain bullet mold. It should be here Tuesday, some how it was in stock at Mid-South.
 My question is do these two rifles have different twist rates, I have read the 7X57 likes a heavier cast bullet. Both rifles have good bores and crowns, bullets are sized to the gun they are shot in. I have used several different powders, seating depths, and used alloys from WW to Lyno. I checked the head space it is good and I I use the Lyman M-Die on all my cast rifle brass. I know the 7X57 will never be a tack driver, and have read others with different caliber’s say they came across that one rifle that just will not shoot cast bullets. This may be mine. Or am I over looking something.   

[Kmrere42]

Hi,


Thought I'd give a hand.  The twist rate for a military mauser is around 8.66" This is rather sharp for a lead bullet with a short shank.  Also military bores really tend to be oversize with long throats to handle the original RN loading. 

Slug and mike the bore at both ends and see if the bore tapers open and if there are any constrictions.



Paul

[gcrank1]

I had to use an overgroove dia. bullet to better fit the throat of the 7mm I had. I kept the velo below about 1450fps and could shoot about as well as the mil-sights allowed even though I had to use more elev. for a given distance.

[hornady]

Up date the 160-grain mold came. And made no noticeable difference. This Mauser just will not shoot cast bullets. I load up Hornady 154 Grain jacketed and it’s a good shooting rifle. Funny thing about it, I load cast 135 and now the 160 grain in the long 7X57 and they shoot great in that rifle.  I cast and load for three other Mausers one in 308 and two 3006, all three do very well with my cast bullets from my Lyman 170 grain and my RCBS 180 grain bullets.

[gcrank1]

Bummer.....
I suppose your rifling could be worn to the point that it just wont hang on to a cast bullet; Ive been there and had to reduce velo so far it was my small game load (32-20 equiv.). But, I gotta ask, What does that bullet do when you take a fire-formed in that gun case, roll back any residual crimp, and try to fit it in? If it just falls in it is too small a dia. for that throat.
Have you slugged the bore at the breech end only?
Are you aware of The Cast Bullet Association?

[Lloyd Smale]

some 757s have very long throats. Most like heavy long bullets seated as far out as you can and rifling is some can be shallow or even worn shallow so harder alloys will grab the rifling a bit better and shoot better because of it.