Short Chambered Barrel (308 Winchester)

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  • Last Post 14 September 2014
OU812 posted this 30 June 2014

I just ordered one of Brownells Short Chambered Shilen chrome molly barrels on sale with free shipping. It has the Remington Varmint contour, 1/10 twist, 308 Winchester caliber. Which reamer should I order to achieve a smaller .3095 diameter lead while still retaining the standard 308 Winchester chamber and neck size. Would the 308 Obermyer version work. This is my first post. Thanks, Keith  

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OU812 posted this 30 June 2014

Edit: Trying to achieve a smaller .3085 lead

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OU812 posted this 30 June 2014

For some reason I cannot edit original post. Here is picture of Obermeyer reamer http://s1225.photobucket.com/user/aviserated1/media/308OBERMEYERMATCHGR_zpsfbf7f552.jpg.html>

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RicinYakima posted this 30 June 2014

FWIW, my experience is that everything is cut except the shoulder. Lead is probably already SAMMI spec. Sorry for the bad news, Ric

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Ken Campbell Iowa posted this 30 June 2014

ppg will grind a reamer to your specs at no additional charge. i prefer separate throater, both bushed, so you can throat to your preferred bullet. more money however.

your drawing shows throat taper of 5 degrees included ... in my fondest dreams i would use a throat of 1/2 to 3/4 degree included for cast bullets. i am now using a throater with 3 degrees included and it does not give the engraving i want. just my opinion, proceed carefully ( g )

ken

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OU812 posted this 30 June 2014

I called Shilen and they told me that lead was not cut on these. I will use my bore scope to inspect. Brownells has a good return policy BTW

What is SAMMI spec .3100? This smaller than my factory Remington's 308 Nato spec of .3120” and .150 length lead.

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RicinYakima posted this 30 June 2014

SAMMI spec is 0.310” (plus 0.002") throat with a 1 degree 45 minute angle to bore. Again plus 0.002". http://www.saami.org/pubresources/ccdrawings/Rifle/308%20Winchester.pdf

Ric

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OU812 posted this 30 June 2014

I will let you guys know what the lead or throat measures when I receive barrel. Thanks for your help.

BTW looking at some of the match results, I noticed that the custom tighter necked 30BR guns shoot only a tad better than a factory Savage. My factory Remington 700 VS with it's huge .3120 throat will group 1” with carefully loaded concentric ammo. I size the large .314 lino bullet down to .3115. Bullet is the LEE (Harris Design) CTL312-160-2R

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OU812 posted this 30 June 2014

Here's a picture of bullet and sample target. Velocity is about 1950fps and seems even more accurate the faster bullet is pushed. I will try more velocity next time at range.

http://s1225.photobucket.com/user/aviserated1/media/DSCF7887_zps076b120b.jpg.html>

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OU812 posted this 08 July 2014

Today I received the new 26” Shilen short chambered barrel.  The short throat or lead is cut to .3080” diameter. Later I will post picture of chamber cast. Crown is cut and finished to 11 degree angle. Barrel rifling is not lapped, looks lots better than my factory Remington barrel.

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OU812 posted this 08 July 2014

Length of lead measures slightly under .100” and diameter of lead is close to groove diameter (about.3080- .3083"). So the  small diameter lead can be cut larger if wanted. The case neck diameter appears to measure SAMMI 308 Winchester (about .345"). This short cut chamber is very similar to the 308 Obermyer.

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Ken Campbell Iowa posted this 09 July 2014

to dabble just a moment in perversion ... i always thought it would be interesting to take a short-chambered barrel and create a cartridge case to fit it ... in this example you would wind up with roughly a rem. 30 BR brass ...with a neidner type throat ( ie:: none ... needs a bore rider long nose bullet ) ..

of course you could still use a throater for the usual molds ..

perversion OFF

ken

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OU812 posted this 09 July 2014

Guys, Can I adjust headspace using thicker recoil lug? Factory recoil lug thickness is .186". Bolt will JUST close on GO gauge using a .200 thick recoil lug. All I will have to do is use a Uni Throater to cut throat without cutting shoulder back. Will this work?

I am looking for good universal throat. Any ideas on what throat deminsions should be for both cast and jacketed? .

Also, what is the best way to finish barrel to a Black matte finsh?

Safe and Sound

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?v=47dtFZ8CFo8&list=RD47dtFZ8CFo8#t=0     ...  

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TomG posted this 09 July 2014

OU,

While you haven't said what receiver you are installing this barrel on, I'm assuming it's a Remington 700. 

Yes, you can adjust headspace clearance using the thickness of the recoil plate but you cannot ignore the bolt nose to end of the barrel clearance. This is a safety thing and you will be increasing it even further when you use a thicker recoil plate.

While you may want to save money, if it were mine, I'd do it right and set up the proper clearance on the bolt nose, both radially and longitudinally and then chamber the barrel deeper with a chamber reamer as short chambered barrels are designed to be done. In other words do it right.

You must realize that the bolt nose clearance on a Rem. 700 regulates the amount of case head that is sticking out of the back of the chamber unsupported. Right now with a short chambered barrel it's probably excessive and dangerous. It will be worse if you put a thicker recoil plate in there. What you are suggesting is unsafe. If you don't control these dimensions, you can blow a case head out and get hurt not to mention wreck your gun.

I usually set the clearance dimension of the end of the bolt to the end of the barrel to .010” for maximum support and safety. You can make it smaller but there is always the chance that some debris or a bristle from a cleaning brush can get in there and stop the bolt from closing. I would not let the bolt nose clearance go over .020 ever. A simple way of measuring bolt nose clearance is to take some grease and smear a dab onto the end of the bolt nose. Stick a #9 lead shot to the end of the bolt nose. Install the barrel onto the receiver and close the bolt. You will squash the pellet down to the clearance and can then mike it.  Then adjust from there in the lathe. Make sure you really lube the bolt lugs and bolt recesses in the receiver so that you don't gall them up closing on the lead. You can mess them up if you don't as they aren't designed to smash lead.

I usually set up the bolt nose radial clearance to .010 per side to keep the gap as close as practical and increase safety. This extension that is built onto the end of Remington barrels ( “the three rings of steel", to use their jargon ) is to contain the blast if a case head ruptures.  Again, consider safety and do it right in the first place.

Notice I'm saying how I do it. Not how you should do it. You can choose any dimension you like but think safety first before saving a few bucks and taking the chance of having a cobbled up job. While you can see that installing a barrel is not rocket science, there are some things about it that require some careful thought before doing. 

If you want a matte barrel finish, you can sand blast the barrel and then apply the finish. Here's an area where you can save some money. Blast it or sand it down and then spray it with a flat black paint. If you cure it in your wife's oven it will bake on pretty hard and last a reasonable length of time.

Tom G

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OU812 posted this 09 July 2014

Bolt nose clearance appears to be  too much (.030) using the .014” thicker .200 recoil lug. The factory .186 recoil lug should bring bolt nose clearance in spec of .010-.020. I will cut chamber deeper to bring head space in spec. Here is resized IMI case setting in short cut chamber.    

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Ken Campbell Iowa posted this 09 July 2014

dang ! so close ... i set up match rifles so the bolt feels the brass about half way on closing. however, the 0.030 nose clearance is slightly too much ... not for mild cast bullet shooting, but we have to error on the safe side ... such as someone sticking an overload in there when you are not looking ... then you want that famous m700 ” three rings of steel ” between the gas and the shooter.

just for trivia, i set bolt NOSE clearane-to-barrel at 0.004 MINIMUM for a match rig.

thanks for your posts; i have never cut a short chambered barrel, i didn't realize they were that close.

for throat lead angle, i wouldn't compromise for j bullets, they can take care of themselves ( dangit ! ) .. i would go with 1/2 to 3/4 degree INCLUDED ) .. heh, be gentle to our soft-hearted little friends ...

oh, if you hand throat it yourself, go slightly ( 0.010 ) short; when you lap the throat it will remove some little burrs that can mislead ( mis- leade ? heh ) you.

ken

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OU812 posted this 09 July 2014

Ken Campbell Iowa wrote: for throat lead angle, i wouldn't compromise for j bullets, they can take care of themselves ( dangit ! ) .. i would go with 1/2 to 3/4 degree INCLUDED ) .. heh, be gentle to our soft-hearted little friends ...

oh, if you hand throat it yourself, go slightly ( 0.010 ) short; when you lap the throat it will remove some little burrs that can mislead ( mis- leade ? heh ) you.

ken Would a freebore length of .090” and a tighter leade diameter .3085” be best for accuracy? Or will the SAMMI 308 Winchester with .310 diameter leade work just as good

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OU812 posted this 10 July 2014

I have read that a bullet with a long bore ride section such as the RCBS SIL 165 or 311299 requires a more steep throat angle past lead to work best. What style of bullet requires a 1/2 or 3/4 degree included angle?

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Ken Campbell Iowa posted this 10 July 2014

heh, the best throating for cast bullets seems to be still controversial. probably because no one design has proven to be the ONLY good one.

it seems that whatever the details, the more support for the greatest length of bullet possible gives the best result. so the bullet and throat design should work together. the bullet should look a lot like the throat.

the easiest to imagine in your mind is the tapered bullet in a matching tapered throat. if the length of the contact patch of the bullet is one inch, it takes an angle of about 1/2 degree included to give full support .

imho, the popular long bore riding nose type bullets are so popular because they are easy to get 2-3 moa in a decent factory chamber. ~2 moa is completely good enough for most field shooting. to obtain groups half of that and better requires much more planning and specialization. some say luck. ( g ) .

ken

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OU812 posted this 10 July 2014

Thanks Ken. I have a couple of  the Lee tapered design bullets that shoot pretty good in my factory 308 Remington (see 9th post above). How would I measure tapered angle section of these bullets to see what angle they already have? They appear to have 1 degree total or 1/2 degree per side.

. These are fat bullets measuring .314 at bands as cast using linotype alloy. Area in front of band measures .310 then tapers down to .300. Total length  on surface from .310 to .300 is  .340 long. Can angle be figured with this measurement? 

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OU812 posted this 10 July 2014

I emailed Lee asking what the taper was. Here is their reply: . C312-155-2R- 1.62° INCLUDED CTL312-160-2R- 1.13° INCLUDED

Lee Precision, Inc. 4275 Highway U Hartford, WI 53027 phone: 262-673-3075

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