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Bulseyetom
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Accuracy difference between breech seated & fixed
Apr 24th, 2019 at 1:51pm
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I am quite impressed with the groups pictured here of breech seated bullets shot off of a bench.  It appears that breech seating when everything is worked out is definitely more accurate than fixed ammo, but in the real world how much does a group increase when with the same rifle a well tuned fixed load is fired?  I relize in competition every edge is required but was curious as to how much is lost by fixed ammo.  Tom
  
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calledflyer
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Re: Accuracy difference between breech seated & fixed
Reply #1 - Apr 24th, 2019 at 2:06pm
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In a good rifle, with it's best fixed load compared to a breech seated round, very little is lost. That said, the b.s. is the better way to go in competition, where it can be done.
If you were hunting, it'd be silly to b.s. And, for serious, but non-match shooting choose what you like.
  

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Schuetzendave
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Re: Accuracy difference between breech seated & fixed
Reply #2 - Apr 24th, 2019 at 2:14pm
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With breech seating; it is possible to achieve 1/2 MOA group accuracy with five shots.

Fixed ammunition with cast bullets generally achieves 1 MOA to 2 MOA accuracy.

This target averaging .452" for the five shot groups was shot with plain base cast bullets that were breech seated at 100 yards.

But to do so you need to be able to call the wind and mirage plus fine tune your rifle to find the right powder load; to find it's best sweet spot, which has the minimal barrel vibrations.

Generally there is a sweet spot about every 0.3 grains of powder so testing full grain and half grain loads will not find that (powder) sweet spot.

My rifle has a free floated barrel so I do not need to determine the point to rest my barrel on the front rest to minimize barrel vibrations (i.e. barrel sweet spot).
I shoot off the free floating forearm.

« Last Edit: Apr 24th, 2019 at 9:12pm by Schuetzendave »  
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Bulseyetom
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Re: Accuracy difference between breech seated & fixed
Reply #3 - Apr 24th, 2019 at 3:37pm
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Having shot short range benchrest at 100 yards with a 22ppc and 6ppc for several years I know the work that goes into shooting 100 yard groups in the 3's like those shown!  All I can say is Wow!  Cheesy  Tom
  
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Re: Accuracy difference between breech seated & fixed
Reply #4 - Apr 24th, 2019 at 3:41pm
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Dave, how often do you clean the barrel in a match?  Do you have a separate target for sighters?  Tom
  
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Schuetzendave
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Re: Accuracy difference between breech seated & fixed
Reply #5 - Apr 24th, 2019 at 4:24pm
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Yes in ISSA and ASSRA and WSU events you have a separate target to sight in.

If I have time I clean my rifle between events.

However with Alberta Schuetzen Lube I can easily fire over 100 shots without leading or fouling that will affect my accuracy.

With a clean barrel I fire four shots into the berm to foul the bore before I try to sight the rifle.
« Last Edit: Apr 26th, 2019 at 5:06am by Schuetzendave »  
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40_Rod
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Re: Accuracy difference between breech seated & fixed
Reply #6 - Apr 28th, 2019 at 10:02am
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The last guy who I remember doing really accurate gun smithing for fixed ammunition was Egan. He chambered rifles for his molds and some of those rifles were very accurate.

40 Rod
  
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JS47
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Re: Accuracy difference between breech seated & fixed
Reply #7 - Apr 28th, 2019 at 11:07pm
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What breech seating does is insure that the bullet is started straight into the rifling by eliminating any variations in the cases. With a minimum dimension bench rest chamber and cases that have been turned to fit that chamber you can shoot fixed ammunition as well as Tony Boyer if you can shoot to the conditions. Breech seating is just a whole lot easier if you're not up against a short time constraint.

JS
  

"I'll be happy to contribute to the wolf recovery program, 180 grains at a time"  Unknown western rancher
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Re: Accuracy difference between breech seated & fixed
Reply #8 - Apr 29th, 2019 at 12:43pm
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I suspect that if you have a chamber with the right dimensions and a bullet that works perfectly with it, then there might not be much difference, but in all of my .32-40 & .38-55 rifles it was pretty easy to get them shooting really well with breech seated bullets. 

The bullet still has to fit well, but I think breech seating is the easiest way to extract the most accuracy.

Chris.
  
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