Mellow out. Guess I should used a smiley face. mtmuley
Threading and chopping a barrel?
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Ok, mellowing out....
Blue Steel
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Maybe everyone could be right:
www.gunsandammo.com
>>>>So, how many fps do you lose shortening a barrel? It depends on where you started. Going from 26 inches down to 20 inches actually picked up speed, not lost it. In the regular zone, between 20 and 16, the velocity loss could be anything from 12 to 50 fps. When we started down into the SBR zone, we sometimes saw velocity losses of more than 100 fps just from a 1-inch change in length. The short answer to the question of how much velocity do you lose per inch? It depends.<<<<
www.remington.com
>>>... traditional rifle cartridges like .30-06 Springfield or .270 Winchester were originally designed around longer barrel lengths, often 22 to 24 inches. Shortening those barrels can reduce velocity noticeably.
But modern cartridge development has changed the game. Many newer cartridges and loads are designed to perform efficiently in shorter barrels, using optimized powders that burn faster and more completely. This allows hunters and shooters to maintain impressive ballistic performance without carrying excessively long rifles.<<<
Barrel Length vs. Velocity - Guns and Ammo
I'm destroying a perfectly good barrel in the name of science. And not just a perfectly good barrel — an expensive one."How much velocity do I lose if I shorten the barrel on my AR?"The answer ranges from
www.gunsandammo.com
>>>>So, how many fps do you lose shortening a barrel? It depends on where you started. Going from 26 inches down to 20 inches actually picked up speed, not lost it. In the regular zone, between 20 and 16, the velocity loss could be anything from 12 to 50 fps. When we started down into the SBR zone, we sometimes saw velocity losses of more than 100 fps just from a 1-inch change in length. The short answer to the question of how much velocity do you lose per inch? It depends.<<<<
Does Barrel Length Really Matter? Understanding Velocity, Accuracy, and Performance
Does barrel length really matter? Learn how it impacts velocity, accuracy, and handling—and how to choose the right setup for your shooting style and performance goals.
>>>... traditional rifle cartridges like .30-06 Springfield or .270 Winchester were originally designed around longer barrel lengths, often 22 to 24 inches. Shortening those barrels can reduce velocity noticeably.
But modern cartridge development has changed the game. Many newer cartridges and loads are designed to perform efficiently in shorter barrels, using optimized powders that burn faster and more completely. This allows hunters and shooters to maintain impressive ballistic performance without carrying excessively long rifles.<<<
Wind Gypsy
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How short do people think a barrel really needs to get to go from 3000 FPS to 2100 FPS (30% reduction)? It isn't anything that doesn't require an ATF tax stamp. Have to get to sub 10"?
Also, lot of people worried about velocity that shoot factory ammo that can easily vary over 100 FPS between lots and they'd never know.
Also, lot of people worried about velocity that shoot factory ammo that can easily vary over 100 FPS between lots and they'd never know.
Dakotakid
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Can you mic your barrel at where you plan to chop? I can give you diameter of mine at the suppressor.
I don’t have those tools. I told the smith to chop it and thread it At 20”
Ajax2744
Well-known member
I’ve personally threaded hundreds of barrels, specifically for suppressor use. And while 1/2x28 threads can technically be used on a .30 cal, the minor diameter of the threads will cut to ~.450”. That leaves about .070” wall thickness between the bottom of the threads and the bore. When you throw a 6”+ can on the end there can be enough leverage to actually bend/snap the barrel at the threads if the can hits something or the gun is dropped/stepped on. I’ve also seen 1/2x28 threads swell from higher pressure of .30 mag cartridges. For .30 cal 9/16 threads or even better 5/8x24 threads are preferred if the barrel OD is big enough.
Your smith is correct and for suppressor use a shoulder for the suppressor or mounting attachment to seat against is highly recommended for a handful or reasons.
As for velocity drop it is not always so cut and dry. I just shot Sunday and my 6.5creed with a 20” barrel and a 5” suppressor was shooting ~75fps under factory rating. My .270win w/ a 20” barrel and 7” suppressor averaged 2fps faster than factory rating of the ammo out of a 24” barrel. And my 6.5prc with a 18.5” barrel and 5” suppressor lost ~about 100fps. So depending on the load, caliber, and firearms they lost anywhere from 0-18fps per inch of barrel lost. I have seen greater velocity lost just depending on specific loads but this was just my most recent testing.
Your smith is correct and for suppressor use a shoulder for the suppressor or mounting attachment to seat against is highly recommended for a handful or reasons.
As for velocity drop it is not always so cut and dry. I just shot Sunday and my 6.5creed with a 20” barrel and a 5” suppressor was shooting ~75fps under factory rating. My .270win w/ a 20” barrel and 7” suppressor averaged 2fps faster than factory rating of the ammo out of a 24” barrel. And my 6.5prc with a 18.5” barrel and 5” suppressor lost ~about 100fps. So depending on the load, caliber, and firearms they lost anywhere from 0-18fps per inch of barrel lost. I have seen greater velocity lost just depending on specific loads but this was just my most recent testing.
There’s a guy over on another sight that builds some big rifle cartridges on pistol setups. 15” 300 rum pushing 230 Bergers 2800fps
Are you comparing your 20” rifle to actual 24” velocities or just what velocity is on the box of ammo?
Ajax2744
Well-known member
I’ve compared velocities before on a barrel before and after chopping but my numbers Sunday I just needed to get velocities for some dope cards for a couple new hunting rifles so I my comparison was based off the box “factory” rating. Based on previous testing using handloads I have generally seen 0-50fps/inch loss depending on rifle. 25fps/inch is generally a decent rule to follow but again it has varied on different setups.
Were those 50fps/inch loss one shot comparisons or multiple? Just wondering if most of that 50fps was the extreme spread and you just caught the extremes. Not saying it doesn’t happen I’ve just never personally had it happen
Ajax2744
Well-known member
That was an average loss over 20 shots. It was in a short barreled (20”) 26 nosler I had. The groups started opening up and needed a rebarrel so I chopped it and threaded it to experiment and use up some reloads before I rebarreled it to 7prc. So yes it was an extreme example on an highly overbored cartridge but I technically have seen it haha. But I still say 25fps/inch is a pretty decent general rule to follow
Yep I believe it with such an over bore cartridge.
bluegrassdan
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When you look at the wall thickness on a sporter profile barrel in .30 caliber after threading to 1/2-28 you will understand why most of us won't thread that size barrel without adding an adapter with a recoil shoulder. Single point threading puts a ton of tool pressure on the barrel through the threading tool. When you have a thin wall between the OD and the bore, that tool pressure translates directly to the inner surface of the bore. While you may not see the reverse of the threads in the bore, there is a good chance that you have created a slightly tighter spot in the bore under the threads or, in some types of barrels (hammer forged and Button rifled) even after stress relief, there is still stress in the steel and that can be released when you cut down the muzzle to the correct OD for threading. That can make the bore open up at that point and create a loose spot. Either of these problems can occur- not always mind you, but I have measured it many times and the accuracy suffers. By threading the barrel OD as is- not reducing it first, then adding a collar at the next higher OD, usually 5/8-24, you avoid that problem altogether. Its not ideal, but it works and in my mind there is much less chance of bending that section of the barrel should you drop the rifle with suppressor attached- yes I have had several come through the shop after that happened and it required me to shorten the barrel again.
