Does gas tube effect barrel time calcs?

[fatelvis]

When figuring loads for optimal barrel time on Quickload, will an Ar’s or M1A’s gas tube affect the calculation over a naked barrel? If so, should I add barrel length, or subtract barrel length? Thanks

 

[DocBII]

Elvis,

I never worried about it, seemed to work correctly without any adjustments.

HTH,
DocBII

 

[fatelvis]

Thanks Doc. What about a muzzle device like a flash suppressor? Do you include the length of the device also?

 

[DocBII]

Elvis,

A one inch difference (24" vs. 25") in barrel length generated only about 50 microseconds of difference. This had about the same effect as changing the load by 0.2-0.3 grains in a 6-284 load of 45 grains. While I'm sure it has some effect, especially with a longer device, it would be hard to pick it up out of background noise.

HTH,
DocBII

 

[jelenko]

But, weren't Chris Longs nodes also about 50 microseconds?

 

[DocBII]

Jelenko,

I don't recall what the time between Chris's nodes are. I used the link in this thread to download the QL version. The values for node 6 at 24" is 1.3084 and at 25" is 1.3617. Node 5 value for 24" is 1.2282 and for 25" is 1.2788. The difference for 24" node 5 and 6 is 0.0802, for 25" it's 0.0829, both of which are greater than 0.0500. My experience has been it requires at least a grain of powder to change between node numbers for a barrel length, dependent upon the cartridge.

HTH,
DocBII