22-250 re-barrel chamber questions

[benchracer]

I am getting ready to re-barrel my 22-250. The barrel that is on it is an Adams & Bennett F34 contour 1:14 twist. It never shot as well as I felt it should and I am pretty sure that the limiting factor is the barrel.


I am will have a 26" Shilen 1:12 twist #4 contour barrel installed. I think the change in twist and upgrade in barrel quality will go a long way toward getting the accuracy edge I am after.


However, one of the things I noticed about my first barrel was how long the chamber throat seemed to be. With 52g AMAX and 50g VMAX bullets, I was getting my best accuracy with a COAL of 2.435", with the actual length to the rifling being in the neighborhood of 2.5"( I don't remember exactly and don't have my notes in front of me. Somewhere between 2.475 and 2.515).


While all of my rifles, regardless of caliber or chambering, have shot most accurately with quite a bit of jump to the rifling, the length to the rifling of my 22-250 always seemed to me like it was a bit excessive.


Am I right that the chamber throat on my 22-250 is excessively long? If so, should I be looking for a different spec reamer or more care in machining the chamber?

 

[rifle 57]

Do you have your own reamer already ? If you do what is the freebore lenth of it . If it has to long of a throat you can have it reground a little shorter. I would not want any more than .025 to .050 free bore with 50 to 55 grn bullets.

 

[benchracer]

I don't have my own reamer. AFAIK, the gunsmith that did the work for me cut the chamber with a standard reamer. I am not pointing fingers at the gunsmith. He has done a lot of great work for me.

I am just trying to figure out what needs to be done to avoid having the same problem with my next barrel. Not sure if my situation is normal for a standard 22-250 reamer or not. Maybe it is just an issue that I need to discuss with the smith who puts on my next barrel.

 

[Hired Gun]

I shoot 50 grain bullets in my 22-250. I use Hornady SPSX and V-Max's mostly and 50 grain Balistic tips from time to time. I haven't been able to touch the rifling for the last 5000 rounds. I just seat them as long as will feed from my Ruger. They must be jumping a mile but still manages to shoot .3" 5 shot groups. I think bedding, barrel and crown quality are bigger factors than the distance to the lands.

If you are putting good money into a barrel job why not use the best barrel you can get? I am frequently asked who is my favorite. I don't really have any favorites but certainly have a short list of those i would rather not use and you have named both of them.

 

[benchracer]

I have never been able to touch the rifling with bullets that I have the twist to stabilize. That, in and of itself, never really bothered me. I am not one obsessed with loading everything to "jam" length in the rifling. In fact, not one of my rifles has shot better touching the rifling. All of my rifles produce their best accuracy from .030 to .080 off the lands.

I worked up loads using 50g VMAX and 52g AMAX bullets. I also tried 55g Blitzkings and Hornady 60g soft points. Neither of those showed promise. The 50 and 52g bullets did OK and I was eventually able to get them down to around .6 for five shots @ 100 yards and around 2.5" at 300 yards.

The groups are not bad, but I would really like to do better with this rifle and I don't believe that is possible with the current barrel. The gunsmith did a first class job of installing and crowning the barrel. No problems there. I don't know enough about machining to evaluate the reamer used, so I am not sure if that is the cause of the freebore, if the freebore is the problem, or if the amount of freebore is normal for a 22-250.

Bedding is not the problem. The rifle is not stringing vertically or horizontally. Nor is it shooting the "double groups" that are a classic sign of bedding problems. It is shooting nice round groups. They are just not tight enough for me.

Hired Gun, I believe you correctly identified the problem when you mentioned barrel quality. The A & B barrel is obviously not a great barrel, but it suited my purposes when I initially had the rifle put together. It had some problems wth point of impact shifts related to fouling early on. I fire lapped the barrel (using only the three finest grits so as not to move the throat) to deal with that issue and it went away. The barrel has since shot just OK and just doesn't show the potential to do any better.

Personally, I have had very good luck with Shilen barrels and believe them to be quality products. FWIW, I have a 6.5-284 with a Krieger barrel that shoots very well. However, my Shilen barrelled 6.5x55 shoots right with it in the accuracy department.

I believe that the Shilen barrel that I intend to have installed will do a lot better than the A & B did. I feel it is of good enough quality to achieve my accuracy goals. My concern is making sure that enough attention is paid to the machining to ensure that the quality of the barrel does not go to waste.

That is the reason for my concern over chamber dimensions. Not knowing what is considered normal for a 22-250, I really don't know how to evaluate that.

Maybe a call to PT&G would be in order here...

 

[shortgrass]

www.saami.org will get you to a print of a SAAMI chamber

 

[Hired Gun]

Megun from PT&G will email you the chamber print if you have the number off the reamer. She is my main man there and then we use Dave if I ever stump her.

 

[benchracer]

Thank you, shortgrass, for the link to the saami chamber prints. Interesting stuff. If I am reading the prints correctly, it appears that there are two common chamber leade angles for .224 cartridges:

1*, 30'

• .218 Bee
• .220 Swift
• .225 Winchester

3*, 10', 36"

• .222 Remington
• .222 Remington Magnum
• .223 Remington

The oddballs are the .22 Hornet @ 3* of chamber leade and the 22-250 @ 2* of chamber leade.

While I don't know how to compute the exact amount of freebore that these chambers would yield, I can at least generalize by comparison.

The 22-250 would have more freebore than the Hornet or any of the .222/.223 family, but less freebore than the Bee, Swift, or .225 Winchester. The amount of freebore would be much closer to the latter group of cartridges than to the former.

Judging by what I know about my rifle's length to the rifling, I would say that the freebore in my rifle's barrel is likely longer than a SAAMI chamber would be.

If I accept the idea that a "normal" SAAMI chamber would have between .025 and .050 of freebore, that would mean that my chamber has been cut with between .075 and .140 of excessive freebore.

Since my rifle has shown no symptoms of excessive headspace, I am inclined to believe that the leade angle on the chambering reamer was out of spec. I know my gunsmith rents his reamers (like many smiths do), so I wonder if the problem with leade angle would have something to do with an earlier repair/resharpening of the reamer.

To anyone who actually knows something about machining, am I in the ballpark on this?

 

[shortgrass]

Hmmmmm,,,,,, rental reamers... Only the company that made the reamer or re-shapened it will know for sure. The company that is renting it out,,,, well maybe,,, maybe not. That is why I buy/own every reamer I have (I now have 50+). I can specify what I want, and I know what I'm getting. If you want precision, that's how you get it! I might be stepping on some toes here, but, of the other "precision gunsmiths/builders" I know, none 'rent' reamers. That's one of the things that contributes to the 'overhead' in this business, tooling. There's no free lunch! When judging throat/lead length in a used barrel round count needs to be taken into consideration, especially with rounds like your .22/250

 

[Hired Gun]

I agree. Never have, never will rent or even borrow a reamer. I run a high pressure flush system and it keeps them in tip top shape.

 

[benchracer]

Thank you, shortgrass, for your insight.

The throat length on my rifle was established when I began load development for it after break-in. The round count at the time was well below 100.

Your stance regarding not renting chamber reamers makes good sense for someone whose interests emphasize precision.

Given the fact that I am after a higher accuracy standard this time around and plan to use a better quality barrel than I started out with, paying attention to the reamer that will be used looks like kind of a no-brainer and worthy of honest discussion with my smith.

 

[Trickymissfit]

I have a couple barrels that are 1:12 twist, and one in 1:14 twist for 22-250's. I would never consider a 1:14 twist barrel again! 60 grain an lighter bullets in most cases work well with a 1:12 twist rate, but if I were to order in another barrel it's be either a 1:11 or a 1:8. Here's my thoughts on this:

* the 1:12 twist will just barely stabalize the new Hornaday 53 grain Vmax bullets with a .29 B/C. Easilly handles B/C's of .27. But sooner or later we want to try the 60 grain + bullets with the higer B/C's. That's where the 1:11 will help you out to about .32 B/C (most guess at the exact numbers), but moving to a 1:8 (or even a 1:9) barrel will be a huge jump. Then you can shoot the higher B/C bullets at will (maybe even a 75 grain bullet)

Being as we are going to get a new barrel in 22-250, I'd simply send the action to PacNor, and let them do all the work. They're cheap when you look at the complete package. I'd also order it in in 22-250AI with a fast twist barrel. Throat it for 75 grain bullets. Dies are easy to come by, and brass life is much longer. Make your case from firing factory loaded 22-250 ammo, or better yet use necked down .243 brass cut back to the max length of your chamber minus .020". I shoot a similar round chambered in 6mm (6mm/250AI). Will push a 105 grain AMAX to almost 3100fps with groups in the mid twos.
gary

 

[TracySes23]

* the 1:12 twist will just barely stabalize the new Hornaday 53 grain Vmax bullets with a .29 B/C. Easilly handles B/C's of .27. But sooner or later we want to try the 60 grain + bullets with the higer B/C's. That's where the 1:11 will help you out to about .32 B/C (most guess at the exact numbers), but moving to a 1:8 (or even a 1:9) barrel will be a huge jump. Then you can shoot the higher B/C bullets at will (maybe even a 75 grain bullet)
gary

Neither Berger, Nosler, Sierra or Hornady makes a 60 grain bullet with a B.C. higher than the Hornady 53 grain V-Max. Some come close, but the 53 grain V-Max appears to be higher than all of them. Actually this shocks me.
Maybe my research wasn't extensive enough.

Spence