Hallo

I`m new here in this forum. I`m an engineer for weapon development from Germany and I need some help.
I have tested the accuracy of some Sauer 202 rifles in caliber .416 Rem Mag and the groups (5 rounds) are about 2� or more. I have checked everything. The guns and the barrels are ok. The ammo was factory ammo and handloads with Barnes-X, Swift A-Frame, Speer Mag Tip and Solids.
I have calculated the twist length with the Greenhill formular and I get a twist length of 19� - 20� but all barrels on the market have a twist length of 14�.
Could this be the Problem ????

Best

MIKE

I have owned more than a dozen .416's and all have shot better than your 2" group with proper handloads using the bullet you mention. If your are sure the barrel and action are fitted properly then I would chect the bedding this is usually the problem I have found.
Good Luck
George

The beeding can`t be a problem at the Sauer 202. It has a front and rear stock witch is mounted on an milled base. The barrel is absolutly free floating. The inner diameter get`s a little bit smaller at the muzzle which should be the best for accuracy.
I have also measured the bullets. The bullets have an diameter of 10,55 - 10,56mm.
The barrel has about 10,57 - 10,58mm.

The CIP says:
Groove minimum = 10.57mm
bullet maximum = 10,57mm

With the tolerances I always get a small gas gab between the bullet and the barrel.
That could also be the problem.

Best

MIKE

How about the crown on the barrel?

The crown of all rifles is ok.
The mistake are not the rifles. I have made some tests at Norma with a special test barrel and it shows the same problem.
The bullet manufacturer told me, that 2 inch groups are within there tolerance when testing their bullets in the test barrel.
At Sauer the absolutly maximum group which is alowed is about 1,5 inch (40mm).

Best

MIKE

I haven't seen a 416 shoot worse than 1.5, rem, taylor, or rigby, or even heard of one...

but...

are you shooting from a firm, strong cradle or bench shooting? This is a rather hard kickign gun, if you aren't used to it.

Tell us about your shooting setup? vise? Scope? Sights? whatchadoing?

jeffe

I have used out factory bench and some scopes (Zeiss, Schmidt+Bender, Leupold).
I have always made 5 round groups.
Also with cooling after every round.

Are the US barrel dimensions a little bit different from our European ? Is this possible ?

The twist lenght is also an interessting thing. Some minutes before, I have calculated the twist length with Quick Load (an special ballistic software). The result was an necessary twist lenght of 20 - 23 inch.
I`m very diffused why everone is useing 14 inch ? Perhaps for a better stability in the target (big animal body) ????

Best

MIKE

Mike the CIP might be the problem in this case. In the US system the bore groove size for .416 bore is .416. you might consider slugging the bore of your Sig with a soft cast lead bullet & measuring the slug. 44 caliber bullets work well for this.

We just had a discussion about the bore size of the .404 Ne. The CIP sytem is a groove size of .418 while the English system .404 groove size is .423.

Welcome to the AR forums.

[ 03-03-2003, 02:00: Message edited by: D Humbarger ]