Seating out heavy monolithic bullets in 7mm-08

Discussion in 'Reloading' started by 180pilot, Mar 12, 2012.

  1. 180pilot

    180pilot Member

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    I have purchased a Savage Axis 7mm-08, which with just a magazine and composite trigger guard change, becomes a long action. Because I need to use 150 gr. Barnes TSX bullets and their long length, I've also purchased a PTC 7mm UNI Throater. My question is, has anyone else experimented with throating barrel lead and seating out long bullets, so start of boat tail is even with start of cartridge shoulder? How much more of a powder like 4350 or Reloader 17 can be used, then shown in reloading manuals? What velocity increase? Pressure problems? Accuracy??? This rifle only has a 22" tube, so will that restrict any increase? BTW the parts to convert Axis to long, cost me under $ 50.00 from Savage. I checked the factory throat with Hornady OAL, and when bullet touches lands, it is right at the COAL 2.80" of my reloading manuals. That puts about a 1/4" of bullet into body of case. ( includes boat tail). With bullet seated out with only boat tail below neck/shoulder junction, it measures 3.00" I need to still measure more accurately from ogives, but appears I would need to ream about 0.200" + whatever jump I want.
     
  2. rscott5028

    rscott5028 Well-Known Member

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    I've never attempted what you're about to do. But, here are some things to consider.

    Once you take metal off, you can't put it back. Triple check all of your measurements to be sure they're accurate and repeatable.

    The lead angle on the PTG throater may well be different from your factory chamber. So, go about half or less. Then, clean everything and measure again using your bullet. Then, cut a little and measure again. You basically want to sneak up on the final depth and use lots of cutting fluid. If you get greedy, you may be in trouble.

    Hopefully, it will shoot these bullets to your liking once you're done. Otherwise, you may need a new barrel. Because it may well not like any bullets at that point.

    -- richard
     

  3. yawn

    yawn Well-Known Member

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    Im just a little curious as to why you have to use a 150gr in a 7mm08? given that the tsx generally work best in light weights for cal.
     
  4. 180pilot

    180pilot Member

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    150 has slightly better B.C. and I have a boat load of them. Plus, I have an interest in the 168 Berger VLD, a longy too. Would try to cut my throat to use both.
    Does your statement have to do with the effect of diminishing returns on limited length of 2.80" COAL, which curtails velocity of longer bullets by taking up powder space? Or specific performance of both 140 and 150 TSX at same velocity ?
    I bought this to rebarrel or rechamber to .280 A.I., so, just an experiment at moment. Uni Throater has micro adjustments for depth. If I screw up .280 A.I. will clean it up...
     
  5. yawn

    yawn Well-Known Member

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    I was thinking more terminal performance than internal balistics.Iv used them in 6 and 7mm for a few years now and lighter and faster simply kills better so I prefer a 120gr in 7mm08 and I use 140gr in a 280ai. While they are my prefered bullet I lean more towards balistic tips or Amax past 400yds so any small gain in bc by using a heavier over a lighter tsx is a backward step if you have give up to much velocity .Im making an asumption here that this is for a hunting aplication?
     
  6. rscott5028

    rscott5028 Well-Known Member

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    Well, that's a good point depending on the situation.

    IMO - Barnes requires a good bit more impact velocity to get good expansion relative to Bergers. So, you first need to step down in weight due to the construction materials. Then, you may need to step down again to get additional velocity.

    That said, Barnes have excellent terminal peformance when they have sufficent velocity.

    But, I think it's a great experiment if he's willing to rechamber and/or scrap the barrel. I'm not a big fan of rechambering factory barrels.

    -- richard
     
  7. handirifle

    handirifle Active Member

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    I wrote Barnes regarding that same fact, and their response was that the newer tipped TSX bullets open at 1800fps vs the TSX at 2100. The even newer LRX series are designed to open at 1600fps. While not a VLD the newer LRX series havehigh BC's. In the 30 cal they have a 175gr with .508 and the 200gr with .548.

    Living in CA, monolithic's are a requirement, so limiting my range was an aggravation I did not want to have to deal with.

    That said, I haven't taken game with the TTSX yet, but hope to this fall.
     
  8. rscott5028

    rscott5028 Well-Known Member

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    Rest assured TTSX's will do the deed.

    In fact, the 150's may well be fine in the OP's rifle notwithstanding limiting velocity due to the case capacity issue.

    My point is simply that making the throat longer to fit this bullet may end up being a home run or strike out. But, the OP indicated he's willing to rechamber if it doesn't pan out.

    -- richard
     
  9. 180pilot

    180pilot Member

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    My interest is,.. has short action magazine and 2.80" limit hamstringed the heavier long bullets in the 7mm-08 by reduction in powder charges? But then barrel length may have more to do with it, in my Sierra Manual a, 26" 7mm-08 shows 2700 fps with 150 gr. with 44.2 grains of 4350 and the .280 Rem with 22" barrel, same bullet, needs 51.3 grs. 4350 to get 2700.... Or put all the variables of two different rifles in a bag and shake them up......? Soon as I get some clean .308 brass sized just enough to loosely hold 7mm bullet, I'll have to see about how much powder will go behind a seated out bullet, without compressing it...Right Now new Rifle has to go back to factory.. deep reaming cuts in both lands and grooves are more then anyone should accept from Savage..
     

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  10. 180pilot

    180pilot Member

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    Of interest is the slight difference in lengths of some bullets below the 139 gr. SST, 154 gr.SST and 150 gr. TSX:

    And the fact the 150 gr. TSX seated to just have boat tail in case body, will still work in short Axis magazine, and that bullet seated out, well, looks really nasty......However just found out about 11.5:1 twist,,why, why me!!!
     

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  11. 180pilot

    180pilot Member

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    .....Wait again,....Axis in 7mm -08 may be back to 9.5 to 1, have to measure when I get it back.