1:12 on a 20" barrel

[Farmallsh]

Picked up a custom Remington 700 that has a 26" 1:12 barrel made by Shilen. I want to chop it down to 20" if possible. Barrel will be threaded for a suppressor.
Anyone foresee any major problems with doing this?

 

[l115a3]

Re: 1:12 on a 20" barrel

After cut and threaded, don't forget to re-crown for maintain the accuracy.

 

[l115a3]

Re: 1:12 on a 20" barrel

Where did you live in?

 

[ORD]

Re: 1:12 on a 20" barrel

It shouldn't be a problem to cut down to 20". Just make sure that you get the work done by a competent smith who will pay attention to the details. You'll need the cut-down done, the threading done so that it is concentric to the bore, and a re-crown to ensure the best accuracy.

Also, with cutting it to 20", you will lose some muzzle velocity which, combined with the slower 1:12 twist may hamper yoru ability to run any bullets heavier than 175gr with good accuracy/stability. Barrels differ and your mileage will differ as well, but just be aware that running heavier bullets from a slower barrel can lead to stability problems which you definitely DO NOT want when you are using your can.

 

[l115a3]

Re: 1:12 on a 20" barrel

Yep, the threading process should be concentric. If not, your bullet will strike the internal baffle of your can.

 

[SingleShot85]

Re: 1:12 on a 20" barrel

you'll be fine, Remy LTR barrels are 20" and 12 twist. I had one and used my suppressor on it for years. It loved 175smk pushed 2675fps.

 

[Farmallsh]

Re: 1:12 on a 20" barrel

I'll be taking it to Shilen to have the work done. I live South of Dallas, only 25 min from them.
My other bolt gun was built by them and has a 22" barrel. Just wanted to do a shorty with this one. Maybe I should just go with a 24" instead so I can shoot the same ammo ( BH 175 grn match) through both rifles.

 

[brand692]

Re: 1:12 on a 20" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SingleShot85</div><div class="ubbcode-body">you'll be fine, Remy LTR barrels are 20" and 12 twist. I had one and used my suppressor on it for years. It loved 175smk pushed 2675fps. </div></div>

Yup. But more than likely, 175s is as heavy as you will be able to go.

 

[fcordrey]

Re: 1:12 on a 20" barrel

1:12 twist and a 20" barrel .................no problem !

Factory Rem. sps tactical comes that way .

 

[SingleShot85]

Re: 1:12 on a 20" barrel

175 is about all you can reasonably do wit a 12 twist no matter what the length is. I say go with 20", 24 does nothing for you.

 

[BobinNC]

Re: 1:12 on a 20" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SingleShot85</div><div class="ubbcode-body">175 is about all you can reasonably do wit a 12 twist no matter what the length is. I say go with 20", 24 does nothing for you. </div></div>

I would respectfully beg to differ.

Berger recommends a 1-12" twist for their 185 and 190 gr 308 cal VLD target bullets. I've driven 185 Berger LRBT through my 1-12" 20" LTR and they stayed stable out to 1Kyds.

Montana Marine has an entire thread in the "Range Report & Exterior Ballistics" forum about driving Hornady 208 gr. A-Max's from his 1-12" twisted 20.5" barrel.

Thanks,

Bob

 

[SingleShot85]

Re: 1:12 on a 20" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BobinNC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SingleShot85</div><div class="ubbcode-body">175 is about all you can reasonably do wit a 12 twist no matter what the length is. I say go with 20", 24 does nothing for you. </div></div>

I would respectfully beg to differ.

Berger recommends a 1-12" twist for their 185 and 190 gr 308 cal VLD target bullets. I've driven 185 Berger LRBT through my 1-12" 20" LTR and they stayed stable out to 1Kyds.

Montana Marine has an entire thread in the "Range Report & Exterior Ballistics" forum about driving Hornady 208 gr. A-Max's from his 1-12" twisted 20.5" barrel.

Thanks,

Bob

</div></div>

easy killer, I did say reasonably and in reference to MM post about the 208's he leaves the disclaimer that 208s may not work in all 12 twist barrels. His elevation is quite a bit different than down here is TX. My point was that 175's will be just fine. If you can push a heavier than I'm all for it.

 

[mavrick10_2000]

Re: 1:12 on a 20" barrel

You should be ok.

I'd go no higher than 175 shooting suppressed with a 1:12". There are newer optimal twist rate formulas than Greenhill, and when you're talking suppressed and a $200 tax stamp for a potential ooops I'd be real careful.

RSilvers covered this before might have been elsewhere. 1:11.25 or a 1:10 will give you a better safety margin to avoid baffle or end cap strikes.

 

[John Roache]

Re: 1:12 on a 20" barrel

There was a thread on here somewhere that wound up discussing this topic, I wish I could remember where it was, but there was a link that had a real interesting article talking about this. I specifically remember the 308, using a 168 fed GMM, starting with a 26" barrel cutting and crowning 1" at a time, there was NO decrease in velocity until it went below 18" or 19". Rem 700 SPS Tacticals are 20" 1:12 as well. If you reload, you can minimize the velocity effects of a shorter barrel with a faster burning powder. Once ALL of the powder is COMPLETELY burnt, extra length on the barrel has no effect on velocity.... just as long as All of the powder is burnt BEFORE the bullet clears the crown.

 

[LoneWolfUSMC]

Re: 1:12 on a 20" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugg25</div><div class="ubbcode-body">Once ALL of the powder is COMPLETELY burnt, extra length on the barrel has no effect on velocity.... just as long as All of the powder is burnt BEFORE the bullet clears the crown. </div></div>

This is incorrect.

Burning powder is not what moves a bullet down the barrel.

Burning powder creates incredible amounts of heat in a confined space. This causes the gasses that are produced to expand at a very fast rate. The expanding gasses push the projectile through the barrel. Once the powder is expended or there is no more oxygen for combustion, no more gas is produced. However, the gasses that are pushing the bullet will continue to expand and accelerate the bullet until the pressure of the gasses can no longer overcome the friction of the barrel.

Longer barrels will produce higher velocities until you reach unreasonable lengths for a shoulder fired rifle. Weather the velocity is within the extreme spread of the cartridge is dependent upon many factors, the least of which is the quality of ammo. So it may seem that you are not gaining any more velocity, but unless you are firing a sample of the exact same cartridges under laboratory conditions it's going to be difficult to "prove" anything. (a hacksaw and a day on the range is far from "laboratory" conditions.)

What you need to take away from this is with factory loaded match ammo, you will see little difference on the target end of things between a 26" barrel and a 20" barrel on a .308 bolt action rifle using the same barrel type and chamber.

Now if you handload and you like long range shooting, then the extra barrel length can be used to gain greater velocity dependent upon powder and projectile selection. This is why my 700 still has a 26" barrel even though my duty ammo can't make use of it.

IMHO, go short unless you have a reason not to.

 

[DAVETOOLEY]

Re: 1:12 on a 20" barrel

I shot a Remington 700,18" barrel, 308 Win, 1-12 with Sierra FB 180's subsonic all weekend. No problems. Greenhill's formula is very concervative. I've shot a custom 187 30 cal. flat base bullet out of a 1-14 twist. Best 30 cal. barrel I've ever had. Greenhill's formula says it's not supposed to work.

 

[John Roache]

Re: 1:12 on a 20" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugg25</div><div class="ubbcode-body">Once ALL of the powder is COMPLETELY burnt, extra length on the barrel has no effect on velocity.... just as long as All of the powder is burnt BEFORE the bullet clears the crown. </div></div>

This is incorrect.</div></div>

I am by NO MEANS an expert, nor do I claim to be! This is a VERY well written statement! This is exactly how I have read many times (even though I could not repeat it as well as you have

)
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">Burning powder creates incredible amounts of heat in a confined space. This causes the gasses that are produced to expand at a very fast rate. The expanding gasses push the projectile through the barrel. Once the powder is expended or there is no more oxygen for combustion, no more gas is produced. However, the gasses that are pushing the bullet will continue to expand and accelerate the bullet until the pressure of the gasses can no longer overcome the friction of the barrel.</div></div>

I do however believe, even though I could be wrong, that a faster burning powder can help compensate for a shorter barrel. With slower burning powders and shorter barrels, it is possible for the bullet to clear the crown before the powder is completely expended (I guess burnt is not the best choice of words) and still generating pressure.
Once all powder is expended, no more pressure is being generated, although the gas is expanding, which is pushing the bullet down the barrel, and actually, the pressure starts decreasing as the bullet travels down the barrel, allowing more room for the gas to expand.
This is not true if the powder is still burning, thus generating more pressure!


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">... unless you are firing a sample of the exact same cartridges under laboratory conditions it's going to be difficult to "prove" anything. (a hacksaw and a day on the range is far from "laboratory" conditions.)</div></div>
Believe me, I was NOT the one doing the test on this. I do remember that they used all GMM from the same lot so as to be consistent as possible, but I can not speak for how close to "laboratory" conditions they were!

In the end... we do agree on the OPs original question!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">What you need to take away from this is with factory loaded match ammo, you will see little difference on the target end of things between a 26" barrel and a 20" barrel on a .308 bolt action rifle using the same barrel type and chamber.

IMHO, go short unless you have a reason not to. </div></div>

 

[mavrick10_2000]

Re: 1:12 on a 20" barrel

I had my 700 SPS Varmint 26" barrel chopped to 20". Lost about 70FPS on it's fav load. Still shoots fine.

Hell of a lot handier especially when the suppressor adds 7.25" to the length. Now my overall barrel length w/suppressor is 1.25 inches longer, makes up a few FPS, had to drop the powder charge down a few tenths of a grain due to back pressure. I was running warm loads .4gr less than pressure signs on the chrony and case.

 

[LoneWolfUSMC]

Re: 1:12 on a 20" barrel

I agree. If I was running a suppressor on a .308 it would be 20" or less. It's one of the reasons I ordered my AE with a 20" barrel. It's a 1K and in rifle so no need for a long barrel. (although I am going to try to push the limits later this year.)