custom barrel question

H

hilblly

Guest
Hi All
I have a barrel, or more accurately a chamber question.
When you have a barrel made, how many thousand over saami specs do you usually have the chamber made.
I am considering a new barrel for my 270 win. The factory chamber is, I'm sure, way over, and I figure if I'm going to get it rebarreled I might as well do it right.
Thanks in advance for any suggestions
Mike
 
SAAMI spec. is given as a max. and min. Factory chambers are supposed to fall between these sizes. Within the field of accuracy it is generally true that a chamber that is a closer fit to the ammunition to be fired in it will yield greater accuracy, all things being equal, than one that has more clearance. This is because the closer fit provides better alignment for the bullet to the bore. There are other advantages, but that is all we need consider for the moment. What you propose is to go in the wrong direction. Call one of the gunsmiths that advertises on this web site and ask his advice, and then take it. You will save your self a lot of trouble.
 
I buck the trends, therefore I have my barrels chambered UNDER SAAMI minimum for length or 'headspace' and as much as .004 OVER SAAMI in diameter at the base. I see no value in using minimum diameter...... BUT I USE CUSTOM SIZING DIES.

For one who's using factory dies I'll go out on a limb and suggest that you use a "Min SAAMI Spec" reamer for your chamber and have it cut to minimum headspace. You'll stand a pretty good chance of getting acceptable results using factory sizing dies.

hth

al
 
hilblly said:
Hi All
I have a barrel, or more accurately a chamber question.
When you have a barrel made, how many thousand over saami specs do you usually have the chamber made.
I am considering a new barrel for my 270 win. The factory chamber is, I'm sure, way over, and I figure if I'm going to get it rebarreled I might as well do it right.
Thanks in advance for any suggestions
Mike
Click to expand...

Mike,

A chamber is cut with a reamer that is a fixed size. Your question makes me think you think a chamber is cut with a single point tool? or are you asking about headspace? (depth of the cut)

Your gunsmith will have a reamer within specs, and the chamber cut with that reamer, will be that size. If you want a specific dimension chamber, you can have a reamer made to those specs. I see no reason to do this for a .270

Benchrest shooters will have a reamer made specific for their loaded cartridge dimensions, with a little clearance...or not.. in alinwa's case, but anyhow it's not very important for a hunting rifle.

Ben
 
If you a talking about a bolt action rifle, then the chamber width can be anywhere from min to max - it will form itself to the chamger dimensions on the first round fired. From then on - only do neck sizing and NOT full length resizing. If you are cutting a chamber, I would go for the neck to be slightly under or at min sammi, then skim cut neck turn the cartridges. You only have to do it once. This would be the 'most bang for the buck' approach, but obviously you have to reload.

If you plan is only factory loads then try to find out the sammi cartridge case max and go for that.
 
Thanks for the info folks

Answer to a couple of questions
I reload now using neck sizing only. I would like to FL size with the Redding S dies but the point is mute if the chamber is way over. As for the headspace. The bolt shows some resistance at +.007. The chamber: I have mic'd cases at the base of the shoulder and after a couple of firings the brass is .010 over new brass. Are these numbers excessive?
I sort my brass using the RCBS precision Mic. I neck size about 60% of the neck. I should probably start neck turning to get consistent bullet tension.
My intention is to get a bench gun built or buy a used on in the next couple of months, but would still like to see the 270 be a tack driver.
I enjoy long range shooting at the range and varmint hunting.
Any more suggestion would be gladly and graciously accepted.
I am going to take Allen's advice and talk to a smith this next week
Thanks again
Mike
 
Try the Norma 270 brass, with 140 Berger VLD's touching the lands.

Run all the brass through a FL resizer before loading. Chamfer the necks in and out.
 
New Barrel

I would find the best benchrest gunsmith could, tell him what you want and let him order the barrel, ream it and thread it into your action setting the head space in the process.
IMHO somethings are worth paying someone else to do.
I'm having a new bbl. put on my 257 Wby, as my gunsmith also shoots this round he has some high end tooling for it. $500 including the Kreiger Barrel. Seems like cheap insurance.
Give Clarence Hammonds in Red Lion, PA a call.
 
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