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charlie52usaf

chamber issues.

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hello everyone. been a long time coming back. I have an issue with the LR308 I just built. I have the DPMS 18inch SASS barrel installed on my DPMS upper. I plan on hog hunting next year in Texas with my son in law, so I decided to set up for reloading for it. I have had this barrel for 5 or 6 years and just assembled it this year. I have used a Hornady oal gauge to set my jump to the rifling. my headspace is good, did have to ream chamber lightly to close on bolt, but only took a few turns and it was done. when I pushed the bullet out to touch the rifling with the shell fully seated I noticed the bullet was almost completely out of the case. I measured that as per instructions. I then loaded a bullet into a shell (dummy) and set it to the correct col for that bullet and crimped it around the cannelure when it was to it's correct col.i then compared both measurements and with that bullet (Hornady 150gr sp) I would have had a jump of .154 thousands to the rifling. if I used the oal measurement the bullet would have been almost completely out of the shell. I then took a Hornady 165gr sst and did the same measurements. that bullet would have had to jump .104 thousands to the rifling. to me that is way out of line. I am trying to set the jump as close as possible to test for accuracy, but with these measurements that is not possible. I have set up 223 AR-15 the same way with no issues at all, so I don't  believe that I am measuring wrong. and I do know how to use calipers and such. DPMS told me to take it to a qualified gunsmith. I am not a certified gunsmith , but I have built 2 AR-15's with no issues and I know how to put them together. I carried them and worked on them in the Air Force, so it's not that I lack the knowledge. so my question is, do I have a bad barrel altogether or am I dumber than I thought. if I can do 2 AR-15's right than the 308 should be not different. so if anyone would like to chime in please do. I would hate to buy another barrel because of something I over looked. thanks everyone

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Most finish reamers have a "throating"  portion  ground into the reamer.

  Look closley at your reamer, from the front of the case mouth to the end of the reamer.   I'll bet you find that your reamer was ground with a long throat.

    If this is so, as I expect, there is nothing to be done but possibly use something like a Barnes tripleshock, that likes a long jump.

    Its not that your bbl is bad, but you used the wrong reamer.   One ground for heavy , possibly target , bullets.

   Respectfully

   Terry

Edited by Tripledeuce

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Factory barrels have a long throat on them. When I measured mine I was surprised at how long it was and it still shoots sub moa when I do my part. I just load to the max length the mags will let me get away with which is around 2.192" base to ogive. I'm going to measure my dummy round again so you can compare, its a DPMS barrel edit to come. 

 

 

I'm back this is with hornady 168gr A max: base to ogive 2.338" jammed and overall length came in at 2.970" 

 

Hope this helps.

Edited by seasprite

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Ok, I have looked at my reamer and it does appear to have a long throat. this is a Manson live pilot finish reamer that I go from Brownell's. There was nothing in the catalog saying anything about it being for heavy or target bullets. and I think they had special reamers listed for that. Now then, if that is the case could I have removed that much matter with only 3 complete turns with the reamer? Each time I did the reaming I just did one complete turn as I read to do, and then check headspace. I did that only 3 times before the bolt closed on the go gauge. turn one revolution, remove, clean completely and check headspace. And why would it be so different with the same manufacturer and style of reamer between 308 and 223? My 223 reamer was out of the same area of the catalog and is  listed on page 476, right side of page, middle under Manson precision reamers in their catalog # 67 and I had no problems with my 223 chambers. Thanks for everyone's help. I will try other bullets and go out and test I guess and see what happens. I have worked with engines most of my time once I got out of the Air Force and I guess I am use to sizes that can only vary by 1/2 thousand to 2 & 1/2 thousand. So these measurements on my 308 seem excessive to me. by the way the part number on the Mason reamer from Brownell's is 513-000-086. and again thank you all for your input.

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    One thing you have to remember & I'm sure you know , is , the 308AR's are a different animal than the .223/5.56 . Might be because its a .308 & the power of the cartridge may have different characteristics . 
    Did you check head space before you Reamed the Chamber ? By all means test live ammo in different configurations & see how it works out , I'm curious & would appreciate the results .

     It is very time consuming working up a load , I just spent about a year setting some up for my 20' & 16 " 308AR's .

Edited by survivalshop

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   The answer to the question, Could I remove that much metal with just 3 turns, is YES!!!

  It takes very little to remove the rifiling from a bbl.

    And, reamers are mostly ground to SAAMI specs.   Except special order reamers, wildcats, and that sort of thing.

    I'v got 3 308/7,62 reamers.  one is ground with almost NO leade, one is a short throat, and one is a standard 308/7,62.

    I just looked.  The "standard" reamer does seem to have a long throat.   Not like Weatherbys, with .625 thou, freebore, but long

    Respectfully

    Terry

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To Survivalshop, yes I checked headspace. I used my go gauge and the first 2 times the bolt would not close on it, then on 3rd time bolt locks up real nice. I was real careful with the reamer and followed instructions on it's use. then made sure barrel was thoroughly clean before checking with gauge again. the bolt turns and locks easy, but there is no extra slop in it. to all that have replied, thank you. I think I shall buy a box of ammo for it and try it with that first. this way I have known data from a manufacturer. if it works good that way, i'll load of some rounds and go from there. I admit, that I am no expert and have lots to learn. I just want to be safe for one and also to be able to do some precision shooting and hunting with this rifle and I want to know that I can depend on it to work correctly. the 223's are no issue, but this is new for me and I would like to keep all my body parts. I know that AR15's are mil-spec and the 308's are not and there is a certain amount of latitude with the manufacturers. and since I will be using magazines and I can only load to magazine length, the bullet jump surprised me. so much to learn. thank you all once again. I will try to work tis out and get back to you all with the results.

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