24" barrel...is it possible?

[SDB777]

Having just purchased a 24" T/C Encore 1:10tw barrel in 300Whisper for some light load hunting applications, just wanted to know if the longer barrel can do the subsonic loads also.

Most of the load data I've seen is for much shorter tubes, so is it possible to leave the barrel this lenght and get a few different projectiles into the subsonic velocity range?(Really rather not cut this down until the day I can convince "the-one-that-must-be-obeyed" that a Form 4/supressor is a good idea)
Or is the longer tube going to reduce velocity?(By way of bore/bullet friction)


I have AA#7, H110, AA#1680 on hand, as well as some 150grNoslerBT, 168grNoslerBT, 175grBergerHuntingVLD's, and a small quantity of 190grSMK. Not thinking I'll be able to do much with 150gr/168gr NoslerBT in the subsonic range, but the 175gr Berger/190gr SMK might be enough weight.....(Will any of the previously mentioned combo's work?)



Scott (someone always has to be obeyed here) B

[amafrank]

The longer barrel will work for subsonics but you'lll have to work up a load for that particular barrel.

Frank

[Expatriot]

You will run a HIGH risk of sticking bullets in the bore.

This is both NOT FUN and DANGEROUS. This rifle had a 20" barrel.

[SDB777]

Just how much should I bump up a loading of AA#9(8.1grs) that is fired from a 14" barrel at 1035fps? With the extra 10" of barrel, is there a formula to be had that could approximate the velocity loss due to bore friction?
*Sure is a good reason to use QuickLoad*, but I'm pretty cheap when it comes to buying programs on the 'net.



Was 'itching' to go shooting today, but with a hot turkey coming out of the oven, and a ham....well, you got to do what you got to do! Then it rained all afternoon....good time for a nap!




Scott (start high and work down....) B

[dksd39]

well since you mentioned quickload...it shows you needing to reduce the load as 8.1 will be supersonic. The 24" barrel is allowing a better burn.

[SDB777]

Got the supersonic hunting loads zero'd, so I fired a few 5 shot groups at 75 yards from my portable bench. Chrono died as soon as the first projectile ran through the screens, so I wouldn't even guess if the number was correct. And with no spare battery....I won't forget spares the next time out, as I'll be testing something subsonic! The group measured signature in photo is C-T-C






The Glenn Hills cast bullets were seated right at 2.125" COAL and the Noslers were seated to 2.100". I was just trying to find somewhere to start with seating depth and figured maybe a little adjustment for tweaking would be necessary...but I think I'll leave well enough alone for these short range hunting loads and move on to some shoot-for-fun plinking subsonics.
Could not recover any of the projectiles in the shale-pit I was shooting in to look at expansion. Certainly would like to have seen what those cast bullets looked like after hitting that shale.... Think I'll start collecting some newspapers from Sunday delivery and soak them down and shoot into them.


Just thought I'd share two of the better groups.





Scott (wanna go shootin' today too) B

[jimpa]

FWIW I had a decent 3/4' group w/ 220smk,,,then moved the bullet out just shy of the lands = group opened up to 3 1/2 inches. I think that the volume of the case is more important that position of the bullet .
Pushed the bullets deeper and went to 240smk and 9.5 of 296,,,guessing about 85-90% full, shoots real good, puts 3 in 5/8" at 100 Yds.

[alorton]

Originally Posted by dksd39

well since you mentioned quickload...it shows you needing to reduce the load as 8.1 will be supersonic. The 24" barrel is allowing a better burn.

Most subsonic loads from a 10.5" Whisper will shoot slower in a 16" barrel so I would definitely not reduce the load. The Whisper has such a low powder volume with the larger subsonic bullets that it just runs out of gas. It is set up really well for a 8"-12" barrel and a 16" is really on the long side for subsonics.

If you must shoot subs from the long barrel look at Sierra's tables and start with a known supersonic load and chronograph it. Work down slowly as when you get to the powder charge where the barrel starts slowing the bullets down velocity will drop quickly. Make sure that every bullet fires (check the bore after the shot) because you do not want to fire another round into a stuck bullet.

[pud-knocker]

Originally Posted by dksd39

well since you mentioned quickload...it shows you needing to reduce the load as 8.1 will be supersonic. The 24" barrel is allowing a better burn.

I don't think quickload is a good representation of what happens in a 24" barrel with the Whisper, or takes all of the mechanics of the round into account. I have a 24" bolt gun that was built for running super sonics, but....

I played around with loading up some light (110gr to 125gr) subsonics for backyard rabbit plinkers out of my 24" bolt gun. Keeping the velocity at roughly 1,000fps, once you get below about 150gr bullet weight the pressure drops enough that with the 110 or 125 bullets the brass doesn't grow or seal to the chamber, it's not noticable in a 16" AR but in the 24" bolt-gun there is enough barrel back-pressure that you get a face full of powder, like a dangerous shot of powder to the face.

From what I've seen the Quickload data was 2 to 2.5 grains off from real life in the 24". And there's no way it can take variables like chamber seal or gas loss into account, for that reason I've all but quit using it for the Whisper and other wildcats.

[BWE Firearms]

Originally Posted by alorton;

Make sure that every bullet fires (check the bore after the shot) because you do not want to fire another round into a stuck bullet.

alorton,

You mean like this.