Question about barrel length

[sgms18]

I built a whisper with a 16in barrel by tp555. Its a great shooting gun but with the AAC 7.62SD on the end its just too heavy. How much will my accuracy and effective range be effected if I SBR it and cut it down to say 10.5in or so?

[Alleycat]

Depends on what you're doing with it. If you only shoot subs, the answer is there will be no difference. 1050 is 1050 regardless of barrel length. If you're shooting super, It may take about 100fps off. Which will equate to about 2" @ 300 yds. I can live with that.

[sgms18]

Originally Posted by Alleycat

Depends on what you're doing with it. If you only shoot subs, the answer is there will be no difference. 1050 is 1050 regardless of barrel length. If you're shooting super, It may take about 100fps off. Which will equate to about 2" @ 300 yds. I can live with that.

Ok. I didnt think to say but yes, I only shoot subs. Will I need to up my charge to get the same velocity out of a shorter barrel?

[Alleycat]

when you get into subsonic shooting you sometimes have to think backwards. You may have to decrease your charge to get the velocity down to 1050. You will sometimes get bullet drag. 8" to 10" is optimal for subs. Everything after that is extra drag that you will have to overcome with more powder. It's not always the case, but don't be surprised if it happens. As for accuracy, shorter barrels are stiffer and everything else being equal will be more accurate. It was not true before scopes due to sight radius of irons.

[mak91]

I agree that you may have to decrease your load. I have 7 inch, 10 inch and 16 inch 300 whisper uppers. With subs the 7 inch and 16 run pretty close in fps and the 10 inch runs about 100 fps faster with about 5 different powders that I've tried.

[sgms18]

Originally Posted by mak91

I agree that you may have to decrease your load. I have 7 inch, 10 inch and 16 inch 300 whisper uppers. With subs the 7 inch and 16 run pretty close in fps and the 10 inch runs about 100 fps faster with about 5 different powders that I've tried.

What kinda 100yd groups you getn with a 7in bbl? I wuda never thought of goin that short but if it still shoots good thats awsome!

[alorton]

Originally Posted by Alleycat

Depends on what you're doing with it. If you only shoot subs, the answer is there will be no difference. 1050 is 1050 regardless of barrel length. If you're shooting super, It may take about 100fps off. Which will equate to about 2" @ 300 yds. I can live with that.

I would have thought taking 5.5" of barrel off would have made a larger difference than 100fps. Is this due to using such fast powders in the Whisper?

[mak91]

I've only shot these barrels off hand so I really can't say what kind of groups the shorter barrel can do yet. The powders that I've used have ranged in burn rates between 56 - (blue dot) and 69 - (sr4759). The 7 inch barrel has the gas port moved back 1.5 inches for reliable cycling.

[Alleycat]

Originally Posted by alorton

I would have thought taking 5.5" of barrel off would have made a larger difference than 100fps. Is this due to using such fast powders in the Whisper?

As a rule of thumb, it averages about 20 to 25 fps per inch in most cartridges. It's by no means certain. Guns are a lot like women. They all have the same parts, but some are just crazy.

[sgms18]

I shoot nothin but subs, whats the shortest I could go and still have an accurate reliabley cycling weapon?