Barrel countour?

[mefizto]

Greetings all,

I am making some progress in gathering information or .20 Vartarg build, and one of the remaining issues is a barrel contour. The intended build will not be "mountain" or "walking" gun, unless one considers walking from a car/house to a shooting place, so weight is not much of a concern. At the same time, there is not a reason to have it overbuilt.

I am looking at Pac Nor, https://pac-nor.com/contours/, and guestimating based on the volume, the weight of #5 is about 4.5 lb, # 6 is about 5 lb, and Varminter about 5.5 lb. Shortening the barrel to between 22-24 inch, threading and chambering will cut of about 0.25-0.30 lb.

Adding the weight of an action 1.8 lb, light stock and scope should be about 9-10 lb.

Any comments?

Kindest regards,

M

 

[Jwhip]

Sounds great. I don't think you can go wrong. Personal preference really, I've always been a heavy rifle guy. I just built a 20 Prac with a 26" McGowen #7, which I'm fairly certain is almost identical to the Pac-Nor #7. Savage Target action, which by the way is HEAVY- 2.5 lb +, walnut target stock - glass bedded, and a 20x Redfield target scope. The rifle came out to 13 pounds exactly. That may not help much but I would guess you may be a little lighter than your prediction, but it will definitely be close.

 

[SmokinJoe]

Easiest availability is usually a Remington Sendero contour which is medium heavy, then M24 contour which is similar to LV. Check Bugholes.com, they have quite a few different barrels in stock.

 

[Sniper338]

I have a 20 vt with a heavy varmint contour. ID NEVER GO THAT HEAVY AGAIN WITH A 20 CAL.. bought it used tho.

 

[Rick in Oregon]

Every one of my Cooper varminters and my M700's all wear what could be called "varmint weight" barrels. Without actually getting out my calipers, I'd say duplicate the contour Cooper uses, as virtually every one of mine will shoot my handloads under 1/4" all day.

I'm not a light contour barrel guy either, as all my rat rifles get high volume shooting off the bench, and occasional bipod use for chucks.

 

[B23]

Also, I personally find heavier guns easier to shoot. The more weight the gun has the less it moves around which for me makes my overall shooting better. I'd have to look at my list but if I recall the majority of my rifles fall in the 10-12 lb range.

 

[mefizto]

Greetings all,

thank you for your replies.

It appears that with one exception, the preference is for heavier barrels and, consequently, a rifle. Than corresponds well with my experience, my AR is about 9.8 lb, and I have no problem shooting it off-hand.

Hi Rick in Oregon,

I will try to find Cooper's contour.

Kindest regards,

M

 

[Yote Hunter]

A #5 contour is ideal, especially for a sub 24” barrel. Behaves like a heavy barrel with that tiny 20 cal hole in it. No need for more in my opinion. I have a 23” barrel Vartarg in a #5 contour and couldn’t be happier. Only thing I would do different is a 10 or 11 twist instead of a 12 twist.

 

[ricco1949]

I've done VT's in Sendero and LV tapers.......all with long range BR stocks.

I prefer the LV taper.

I make sure the rifle will meet LR light gun 17# specs with scope and accessories assuming the rifle may some day be used in LR BR competition with a barrel change.

I've never found the extra weight to be a burden in a colony rodent exterminator........

 

[mefizto]

Greetings all,

per Rick's in Oregon suggestion, I found a contour for Cooper barrels and Krieger makes one. So it has been ordered with 1 in 11 twist.

Now on to research re reamer.

Kindest regards,

M

 

[Evan]

Mine is a Hart 1:9 twist HV finished at 26" and it provides more speed than I expected and I think hits a nice spot. Rifle is basically a full BR rifle with a laminate stock and weighs in at 15 pounds.

55gn Bergers at 3250fps, 3400 if you want to throw away brass after 1 firing. 3600fps with 40 vmax. Longer barrels always go faster, even with tiny little cartridges like the 20 Vartarg.

http://forum.accurateshooter.com/threads/my-20-vartarg-custom.3969176/

 

[mefizto]

Hi Evan,

I had already found your thread when looking for a reamer references. I intend to shoot lighter bullets, 35-39 gr, and the recommendation seems to be for zero free-bore. Since I have a reference to JGS, I will call them to see if/how much would they charge me for the modification.

How does the reamer work for Lapua dimension cases?

Kindest regards,

M

 

[Evan]

Hi Evan,

I had already found your thread when looking for a reamer references. I intend to shoot lighter bullets, 35-39 gr, and the recommendation seems to be for zero free-bore. Since I have a reference to JGS, I will call them to see if/how much would they charge me for the modification.

How does the reamer work for Lapua dimension cases?

Kindest regards,

M

It works very well. I think that is another reason I can push the speed so high - the chamber is well matched to the brass.

If you want a true no-turn neck, I'd be tempted to go up .001 to a 0.235 over my reamer. It works fine unturned, but it always made me just a tiny bit nervous to only have 0.0025-0.003" of total clearance. I like to skim my necks to clean them up a little, so 0.234 worked out great for me.

The 0.200" line on the print is the important one for Lapua brass. The old Remington 221 brass was smaller than ideal for the SAAMI specified 0.377" chamber dimension for cartridges with this casehead and the brass often measured 0.373" or thereabouts. Todd Kindler tightened up that dimension on his original 20 Vartarg print to 0.375" to better suit the Remington 221 brass (the only brass available at the time, I believe). Lapua 221 brass is sized properly for a SAAMI chamber and typically measures right around 0.375" at the 0.200" line - this is why you can often chamber and shoot the Lapua brass in an original 20 Vartarg chamber, but extraction is sticky and you get a "click" - there is no room for springback after firing and the cam has to pull the jammed case out.

 

[mefizto]

Hi Evan,

thank you for the reply. Just a clarification - I have measured several Lapua cases and they are consistently 0.375 at the 0.200 line; I have resized several .223 cases by a Redding die to 0.374, so the reamer's dimension of 0.3769 should be satisfactory.

The Lapua cases are consistently 0.248 at the neck. Will the dimension shrink upon bullet seating to fit the reamer's 0.234?

Kindest regards,

M

 

[Evan]

Hi Evan,

thank you for the reply. Just a clarification - I have measured several Lapua cases and they are consistently 0.375 at the 0.200 line; I have resized several .223 cases by a Redding die to 0.374, so the reamer's dimension of 0.3769 should be satisfactory.

The Lapua cases are consistently 0.248 at the neck. Will the dimension shrink upon bullet seating to fit the reamer's 0.234?

Kindest regards,

M

Yeah, 0.374 is maybe a hair small for 0.3769, but it is certainly not excessive like the 0.372 you get with original Remington 221 brass.

So when you size the 221 brass in a 20 Vartarg die and seat a bullet, you'll end up with a loaded round of ~0.231-0.232 with Lapua brass so a 0.234 neck is fine, but the pieces that come out thicker are a bit close for my comfort.

 

[mefizto]

Hi Evan,

thank you for the reply. Sorry to be obtuse, but are you suggesting that given the 0.200 reference dimension of 0.374-0.375, the reamer 0.3769 is too large?

Regarding the VarTarg neck, please see my new thread. I have been reading about the reamers, and it appears to be a lot of contradictory information, so I would prefer a wider audience to make me understood so that I do not make a $200 + error.

Kindest regards,

M

 

[Evan]

Hi Evan,

thank you for the reply. Sorry to be obtuse, but are you suggesting that given the 0.200 reference dimension of 0.374-0.375, the reamer 0.3769 is too large?

Regarding the VarTarg neck, please see my new thread. I have been reading about the reamers, and it appears to be a lot of contradictory information, so I would prefer a wider audience to make me understood so that I do not make a $200 + error.

Kindest regards,

M

No that measurement is just fine. I feel like 0.374 in a 0.3769 chamber may be approaching less-optimal, but it is definitely still ok. I think 0.3769 is optimal for 0.375. I wouldn't go any tighter or you'll have trouble with smooth extraction.


From this thread: http://forum.accurateshooter.com/th...t-30-br-reamer-exposed.3933398/#post-37884247

The .200" DATUM (ahead of the bolt-face) should be .4715" > . . . if one wanted, it could be .4729", which would not be bad - way better than too 'tight'.
The chamber needs to be, at least, .0025"> larger than the virgin brass, and the re-size die needs to be smaller than the virgin brass: enough to accommodate some spring-back. Too tight a fit between the virgin brass/chamber (at the web), and/or, re-size die diameter > than virgin brass, or, a combination there of, is the primary cause of the 'dreaded click'. Someone will word this better.
Since Y2K, my reamers, at the .200 DATUM, have been ordered @ 0.003" (-0.00"/plus the tolerance) larger than the new brass of choice. I always purchase brass before ordering a reamer, & have no regrets.RG

That gives you a bit more context for what I'm saying. Randy would probably agree that 0.3769 is optimal for 0.374-0.375 brass too.

 

[mefizto]

Hi Evan,

thank you very much, this is a big help.

Kindest regards,

M

 

[searcher]

Greetings all,

I am making some progress in gathering information or .20 Vartarg build, and one of the remaining issues is a barrel contour. The intended build will not be "mountain" or "walking" gun, unless one considers walking from a car/house to a shooting place, so weight is not much of a concern. At the same time, there is not a reason to have it overbuilt.

I am looking at Pac Nor, https://pac-nor.com/contours/, and guestimating based on the volume, the weight of #5 is about 4.5 lb, # 6 is about 5 lb, and Varminter about 5.5 lb. Shortening the barrel to between 22-24 inch, threading and chambering will cut of about 0.25-0.30 lb.

Adding the weight of an action 1.8 lb, light stock and scope should be about 9-10 lb.

Any comments?

Kindest regards,

M

Assuming your action has a long enough tenon to adequately support it - I'd go with the heaviest diameter barrel you feel comfortable with (Sendero weight as a minimum for me on a varmint rig) and can fit into your stock. I only wish more of my varmint rigs had heavier barrels than they do - for I don't carry them but from the truck to the shooting table. In time - they all will. My opinion is based on my use - that of high-volume ground squirrel shooting and coyotes, usually at distance. With the big barrels, I can get 20 to 30 rounds off in short order before giving it a short rest. Wimpy barrels tend to wear out much faster with that kind of shooting. I'd also keep them long enough to wring every FPS you can get out of it.

 

[Knifeman]

I built a 20 Vartarg with a Pacnor 24” Remington Varmint contour. For coyote and ground hog hunting. BIG Mistake!!! With scope and wicked light it weighs a bunch. I carry it huntin but HATE it. The next Vartarg I build WILL not have a heavy barrel. JMO.