6 Creedmoor chamber oversized?
- Thread starter cc737
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Sorry, I wouldn't use a piece of brass for accurate measurement of much of anything, too variable. Get a chamber cast done. - dan
Well - The salient question is whether the slightly oversize chamber is safe. I would like to point out that swedish mauser ammo made with north american brass is undersize by something like 5 to 10 thou, with no ill effect. The venerable Lee Enfield uses brass that is even more undersize, and has done so for over 100 years.
So, its hard to conceive that the chamber being a thou or two oversize is unsafe.
So, its hard to conceive that the chamber being a thou or two oversize is unsafe.
It isnt. Just hard on brass. Possibly less accurate, though I have seen old LE's that managed amazing accuracy considering the state of their chambers. - dan
Mystic Precision
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Would you want a custom rifle with all its included costs and have a chamber at or beyond max spec? Max chamber spec should be around 0.4735"... thus brass should be typically 1 thou narrower when fired.
would you want to deal with the hassle of very fat brass and how to size or maintain the very expensive brass?
I doubt this is a 'working' rifle and I assume the OP would like to reload... but I could be wrong.
As for safety, how many firings would a case head survive with this level of expansion and thus sizing? I usually toss my cases if they have ever grown several thou after firing. A few thou wider then SAAMI max... yeah, they go in the trash.
Similar to the GLOCK chambers... brass is 'fine' but would you want to reload that stuff?
Jerry
Mystic Precision
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PS, incase others didn't see, OP is running Small Primer Lapua brass and a reasonable load. If that type of brass is expanding that much with a typical load, that case is not well supported during the firing process. I would be concerned from the accuracy issues alone let alone everything else.
Mystic - The OP, in his original post was wondering if the chamber is unsafe. Hence my answer. Once the brass is fired to its slightly oversize state, subsequent neck sizings, or even partial resizings wont work the brass excessively. Who knows, the extra case volume may come in handy.
If the OP is looking for a reason to question the quality of the work done, rather than safety, he should address it in some other way, as you have outlined.
If the OP is looking for a reason to question the quality of the work done, rather than safety, he should address it in some other way, as you have outlined.
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This 6cm was built to shoot in F-class
I have so far used only Lapua brass, with my 6br and 260 I usually reload 10 to 12 times, every 3 time use an AMP annealer.
As Bob Pitcairn told me your brass is still good and now your brass cost per shot cost is now less than 10 percent, say 12 cents. you could shoot another 6 times and your per shot cost is now 8 cents
it's not worth the risk of a failure of one piece of brass in competion
I have so far used only Lapua brass, with my 6br and 260 I usually reload 10 to 12 times, every 3 time use an AMP annealer.
As Bob Pitcairn told me your brass is still good and now your brass cost per shot cost is now less than 10 percent, say 12 cents. you could shoot another 6 times and your per shot cost is now 8 cents
it's not worth the risk of a failure of one piece of brass in competion
Just so anyone reading the post knows the Op has been contacted a few times about the concerns on his brass life in our chamber that i did at Insite Arms. His barrel was number 192 in the 6CM configuration and it was done same as the previous 191 barrels and no issues have ever been presented to us on the reamer as we have it spec'd from any other customers concerning brass life or safety of the chamber. We have told the OP we can refund no issue if he thinks brass life wont be what he requires for his use. As to the safety and chamber job quality or accuracy there is zero issues with any we have produced on this reamer . On our chambers Hornady 108 factory come out once fired at .472 to .473 and the federal of which i have ran for 2 seasons comes out at .474 to .475 as its 3100 plus on a 30 degree day. Hornady is in the 2970 ish range and will print sub 3/8 groups as the norm. Thanks. Harley
Mystic Precision
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if the barrel is shooting accurately and you have already fireformed your brass to that chamber, just have a sizing die honed to the larger dimensions so you do not overwork your brass.... or easier, set back the barrel an 1" + and fix it permanently/properly
For F class, you aren't going to have that barrel for long so ensure it is marked or destroyed once you are done with it.
I would also have a hard look at the lock up of the action.... our guns can/should handle a crap ton of pressure without allowing brass to over expand. now this is not safe practise nor an endorsement to go beserk with your loadings (safety ALWAYS matters) but most F class rifles are built to a level of lock up that it can handle these conditions.
I am sure you have heard the many stories of F TR and Lapua SR brass.....
Jerry
Speaking with 25 or 30 guys i know ran our reamer spec on stuff over the past few years it seems lapua and hornady being the 2 most used brass types used everyone reports 10 plus reloadings at 3000 fps and a few at 3050 ish on 42.5 h4350 and some at 43 gr of h4831SC are the common charges based on the barrels we run. Of course every one knows this is just data and one cant say 1 is safe in another set up or that the pressure is safe to load on another set up. That would be stupid. Whats moderate in 1 gun can be dangerous in another as they are to many factors that change stuff dramatically. From bullets to barrels to actions to much comes in to effect on pressure.
