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Thread: 6.5 mauser tight chambering.

  1. #1

    Default 6.5 mauser tight chambering.

    I was loading 50 rounds on the weekend with 25 new RP cases and 25 previously fired NNy cases. I full-length resized but at the range the rounds were very tight to chamber. The RP were ok but much tighter than normal, the NNy require a shwartzenegger wrist to chamber. I checked bullet seating depth and it is not a problem. All cases were trimmed. A couple of fired RP cases chamber no problem. I didn't fire the nny as they were so tight, i was concerned. What gives, did I set up my dies incorrectly? shoulder not back enough? I though I had been diligent.

    Thanks for any thoughts

  2. #2
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    Default

    Some chambers are tight or short in the base to shoulder dim. That's a good thing. If your f/l die wasn't touching the shell holder, screw it down more or until it contact the shell holder. Most likely it is the base to shoulder dimension (headspace) as a slightly over sized body would still chamber when tight. Were the previously fired cases fired in that gun? If so I find it hard to believe they wont chamber. Maybe the cases are getting bulged in the seating die, maybe a crimp is being applied with the seating. What ever it is it is happening to all, right? DO the cases chamber before running though the die? Take a caliper and measure all around the case including the neck diameter at the mouth with a loaded round. What is the rifle here? Generally a military rifle will not be a tight chamber. I do think it's a little snug for general use.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  3. #3

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    I had a problem like this, turns out I was collapsing the case a bit seating the bullet, due to me not adjusting the bullet seater die correctly and engaging the crimp part of the die. Hope that helps.

  4. #4

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    Thanks for the replies

    Rifle is a M77 the RP cases are new the NNY previously fired in another rifle. All case sized and trimmed. All cases are afffected the same way. I ran some of the nny loaded cases through my 1896 mauser and they are similarly stiff. A couple of the fired cases from the RP batch cycle just fine but have circular marks around the neck and shoulder that i have not seen previously.

    A quick measuring shortly after my range session revealed nothing. I will check all of your suggestions on the weekend. What would happen if i engage the crimp accidentally, although it doesn't look as if I hve.

    Cheers

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    Quote Originally Posted by 35gibber View Post
    Thanks for the replies

    Rifle is a M77 the RP cases are new the NNY previously fired in another rifle. All case sized and trimmed. All cases are afffected the same way. I ran some of the nny loaded cases through my 1896 mauser and they are similarly stiff. A couple of the fired cases from the RP batch cycle just fine but have circular marks around the neck and shoulder that i have not seen previously.

    A quick measuring shortly after my range session revealed nothing. I will check all of your suggestions on the weekend. What would happen if i engage the crimp accidentally, although it doesn't look as if I hve.

    Cheers
    When you say all cases were sized...how much? Full length sized with the die touching the shell holder?

    If the seating die is accidently putting a crimp on the case, (while seating the bullet) it will likely bulge the case around the neck area. Back off the body of the seater another turn and screw down the seater stem to get the correct over all length. The marks on the neck and shoulder are where contact is made in the chamber. On the shoulder is ok, that is the point of headspace, (about mid shoulder) but the mark on the neck is bad news, there should be not contact marks on the neck. Makes me think the neck dims are too tight or the case neck is bulged. Another thing to check is that you are loading .264" diameter bullets. Sorry, it happens, you could probably seat 277" bullets in that case. I know a guy who loaded and fired .284" bullets in his old Remington 721, 270 Win caliber. He fired four of them before he got tired of beating the bolt open.

    Is this the first time fireing this rifle? Maybe the chamber dims are off. I would expect cases fired in another rifle to be tight but not new unfired R-P cases. Don't shoot it if this problem cannot be found in the die adjustment or cases because a very tight neck can crimp the bullet in the case as the round is forced into the chamber and could boost pressures extremely high.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  6. #6
    New member George's Avatar
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    Default tight fit

    I'll echo Murphy's last paragraph! Tight headspace fit is one thing and can be a very good thing... it can usually be corrected in the sizing operation... much, much better than the opposite problem of too much headspace

    BUT tight in the neck area is a big red flag. If it is caused by over crimping or a wrinkle in the neck brass when seating a bullet it's just a nuisance to correct. If it indicates under-sized chamber neck dimension or wrong bullet???.... big problem. Another possibility is short chamber length compared to standard length brass. Look for signs of shiny areas on the neck RIM/MOUTH edge that could be contacting the end of the chamber. Or better yet check the chamber length (with chamber length gauge) against the case length. Crimping a bullet in by chambering an over-length case can also cause high pressure problems.

  7. #7

    Default Nny Cases ?

    What are NNY cases ? Ive never come across that in my area.

  8. #8

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    I had a 358 Win built a few years ago by a well known gunsmith. No matter how much I full length sized the cases, they were tight chambering. Took the gun back to the smith and he checked headspace, perfect. He had me bring in my dies and a few shells, we sized them in his shop, still tight. To keep the story short, it was the dies. Switched to redding dies and the problem was gone, end of story.

  9. #9

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    Well,after measuring, the cases seem to be bulged ever so slightly in the middle of the case causing some marks on the brass and .......difficult chambering. I checked all suggestions neck is fine case length, bullet diameter etc. The rifle has been loaded for a number of times and has chambered and extracted faultlessly. I will set up my dies again on the weekend and hope it was a fault there. Incidentally NNY brass is I believe cheap Eastern european stuff. Seems to be of ok quality although i was just intending to use it for low pressure practice rounds. Cheers

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