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Hello,
    I was shooting my .257 Roberts today, and another fellow had a .257 Imp with a custom Lilja barrel. In terms of velocity, his loads were leaving mine in the dust! <!--emo&:0--><img src="http://beartoothbullets.com/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'><!--endemo-->  He had a 24" barrel, mine is a 22".
    My question is, do you think his gains were due more to barrel length or to the cartridge? His loads were generating over 300 fps more than mine! I would be highly interested if anyone has had a factory rifle rechambered and has chronographed before and after to determine actual gains. Also, were there any special problems you encountered in the process?
      One of the issues I've had with my rifle is reliable feeding, so I borrowed a couple of his improved cases to check this in my rifle. They actually fed more smoothly than factory cases! For the price of a rechamber and a set of dies...
                              IDShooter
 

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First of all...I think the .257 Roberts Improved is the best wildcat that Parker ever came up with. The first rifle I ever put together, back in the 50's, was one on a small ring Mauser.
There are other advantages to the Imp. Roberts than just an increase in velocity....The sharp shoulders on the case cause hot gas to intersect inside the case rather than in the barrel leades, the flatter sidewalls reduce bolt thrust, more case capacity for slower burn powder with heavy bullets, etc.
The basic problem with factory 257 R, until the +p loads, was the cartridge was down-loaded due to some of the older Mausers of the time. To offset this, the factories should have come out with the Improved on today's modern rifles. I highly recommend the conversion. If you do, use Winchester brass when you fire form your cases.
Best Regards, James
 

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Great info on the Roberts Jim.

ID,

It could very well be the case with the barrel lengths. Also one has to consider the barrel quality and configuration.

Were they factory loads or handloads?

Did you fire your loads in his rifle or vice versa? If not, you really can't know for sure. Not a good idea if they are max handloads anyway. If they are handloads, it's possible he is loading to higher pressure than you are. You can't know for sure without test equipment.

The difference in throat depths may be quite different between barrels. Is he loading to the same OAL as you?

Rifling configuration also can play a role. Land widths and numbers differ. A custom barrel like the Lilja's can have a much smoother internal finish also. You can also spec the number of lands you want in your custom blank.

I know from experience with Custom and factory Contender barrels that say a Shilen blank, used by SSK will tend to get higher performance out of one of his rounds than a factory barrel rechamber of one in some cases. Same applies to a Bellm rechamber of one of his rounds especially the 308 Bellm. The factory barrels with 8 lands and grooves for more bullet jacket displacement tend to cause higher pressure and the need to back off somewhat lower than say a full custom barrel or older 6 groove factory one with a better internal finish and less lands and wider grooves.

So you see there are many variables to consider.

Regards
 

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Discussion Starter #4
Thanks for the advice, gentlemen! Contender, I know there are so many variables it's hard to say why he was getting such high velocities. He paid more for his barrel than my rifle AND scope cost!! So I'm sure we are comparing apples to oranges when I hold my rifle against his. We were both shooting handloads; I was using the hottest published +P data I can find. I believe I could go higher, but I don't have the proper measuring equipment to feel safe doing that so I don't.
   One of the reasons I would like to hear from someone who has simply rechambered an existing rifle is BECAUSE of the great number of variables when you are comparing one rifle to a very different rifle.
     James, all the reasons that you mention besides a velocity gain are super, and you may have convinced me to proceed even if I can't have a real clear idea of potential velocity gains.
     Now, if I can only pry my wallet open... <!--emo&;)--><img src="http://beartoothbullets.com/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'><!--endemo-->
                                        IDShooter
 

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All of Contenders's points are excellent! The real reason that Parker came up with the design was to burn more slow powder with the heavier bullets. Another point I would think about when you have the conversion done....Seat your bullet out as long as your mag box will allow with the heaviest bullet you plan to use. Have the smith throat the chamber for that length. The ideal situation is to have the base of the bullet at the junction of the case neck and case shoulder. Most of the factory loaded .257 Roberts have the bulle seated deep. This setup will give you max case capacity for whatever you would want to load.
Best Regards, James
 

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I have an original 1949 FN Mauser sporter that has had the chamber improved to 257AI. The barrel is a Kruptt steel with a 1in 11" twist. This rifle will not stabilise 100gn projectiles but shoots surpurbly with the 90gn HPBT Sierra Gameking.

Current loads are chronographed at 3268fps av. with groups averaging .6 - .7 consistantly. I have had the oppertunity to shoot wild pigs and small dear both with this rifle and a 243 Win and the step up to 25 cal on this type of game is certainly worthwile.
 

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I don't know about the .257 AI, but last year I rechambered a Ruger #1 in .280 to the .280 AI and have gained a signifacnt velocity jump. IMHO it's worth rechambering to the AI.:cool:

Snake
 
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