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Stabilizing heavy projectiles from a SVI AET barrel


ChrisRR

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For my current 5.4" SVI I seem to have no accuracy/stablization issues with lighter/faster projectiles (165-175gr) and more key-holing encountered when experimenting with 180gr-200gr projectiles (170 PF floor).  Soooo, for my *next* SVI 40 cal I am wondering the following-

 

How well heavy 40 cal projectiles (200gr) can be stabilized from an SVI AET barrel given the low rate of final twist (1:24 I believe). Particularly given the projectile L/D ratio is going to be higher due to the generally longer 200gr projectile?

 

Given it does not appear that AET barrels with higher rates of final twist are available would perhaps a standard SVI barrel (1:16 twist?) be more suited to heavy projectiles due to the additional gyroscopic stabilization imparted?  

 

 

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What is the bullet length?

 

Have you been able to determine what sort of velocity you are getting?

 

For a 170 power factor, you need at least 850 fps.

 

Keyholing normally is from low velocity or too little twist (as you suspect).  

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Yeah, I still suspect the twist as in the test loads the 180s were running 950fps average.  The 200gr were running ~920fps.  

 

The 180gr is 15.40mm, the 200 gr 17.20mm in length.

 

I'm sure the designers of the AET barrel know what they are doing but I wonder and am not aware of what its projectile/velocity limitations at 1:24 twist. I wonder why 1:16 final twist was not used...?

 

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8 hours ago, ChrisRR said:

Yeah, I still suspect the twist as in the test loads the 180s were running 950fps average.  The 200gr were running ~920fps.  

 

The 180gr is 15.40mm, the 200 gr 17.20mm in length.

 

I'm sure the designers of the AET barrel know what they are doing but I wonder and am not aware of what its projectile/velocity limitations at 1:24 twist. I wonder why 1:16 final twist was not used...?

 

What kind of bullet?

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I wasn't certain if that was measured or estimated in your earlier post.

 

If we believe the stability factor, they should be good.  Still, the actual results beat theory any day.
 

RPM's for the 180's and 200's are only about 2,000 apart.

 

Even though the numbers indicate the 200 should be stable, the 1:16" twist barrel may be the cure.

 

 

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When I talked to Scheumann about barrels and twists, I was told the AET barrels were designed for jacketed bullets and I'd see no benefit with lead bullets.  In fact, I was warned away from lead bullets.  So maybe it isn't just the twist that might be the problem.

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When I talked to Scheumann about barrels and twists, I was told the AET barrels were designed for jacketed bullets and I'd see no benefit with lead bullets.  In fact, I was warned away from lead bullets.  So maybe it isn't just the twist that might be the problem.


The AET barrel shoots coated lead well.

I've never tried bare lead and don't plan to.

In terms of the benefits or not, I haven't done a proper experiment. But if someone has a ransom rest...
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On 12/30/2017 at 2:30 PM, ChrisRR said:

Coated lead of the RNFP design (hardline industries mold). Flat base, no bevel.

Still shooting the SVI Ranger?

Ahh, OK.  Just making sure you weren't shooting plated.  Only one of mine ever shot a decent group with Berry's.

 

And no Sir.  Moved on to CKARMS.  

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