throat loss

bruce moulds · Post by **bruce moulds** » Wed Jul 13, 2011 10:03 pm

does 22 shots per 0.001" throat loss sound excessive for a 284 win not loaded hot?
this is for about 900 shots.
bruce moulds.

johnk · Post by **johnk** » Thu Jul 14, 2011 7:40 am

Sounds like you might need to check your measuring gear for issues.

Recently, I had strange results, which I finally put down to a ding on the case mouth that was preventing the case from fully entering the chamber. I was using a new Stomey Point & an old case because my normal one went temporarily MIA after the January floods.

Post by **AlanF** » Thu Jul 14, 2011 8:58 am

bruce moulds wrote:does 22 shots per 0.001" throat loss sound excessive for a 284 win not loaded hot?
this is for about 900 shots.
bruce moulds.

That's about 5 thou per 100 shots - actually more than your average 6.5-284. Did you check it somewhere in the middle of the 900 rounds. Maybe most of it happened at the very start.

Alan

bruce moulds · Post by **bruce moulds** » Thu Jul 14, 2011 6:03 pm

a loss of 0.040 in 906 shots. checked & rechecked.
maybe my maths are wrong.
the loss is getting faster as more shots are fired.
bruce.

Post by **AlanF** » Thu Jul 14, 2011 6:07 pm

bruce moulds wrote:...the loss is getting faster as more shots are fired.
bruce.

Have you changed powder or primers?

dave · Post by **dave** » Thu Jul 14, 2011 7:50 pm

barrel temperature,rate of fire, load intensity, calibre,barrel type-size/profile,rifling type etc, would all be factors in my opinion.

too many variables to consider when trying to come up with a set ratio of throat erosion. IMHO.

but i do agree, it can be a worry when trying to maximise barrel life and prolong accuracy.

cheers
dave g

ratshot · Post by **ratshot** » Thu Jul 14, 2011 8:04 pm

barrel wear has a lot to do with the composition of the steel , some S/S threads and chambers real easy , good for cutters and reamers, but not for barrel wear.

BATattack · Post by **BATattack** » Thu Jul 14, 2011 9:33 pm

im getting about .001 per 100 out of my 6.5x47 so far with 1100 through it. them .284s are barrel burners :wink:

!!!

RDavies · Post by **RDavies** » Fri Jul 15, 2011 7:18 am

I had one 284 barrel which was soft, machined very well and was very accurate, but eroded very quickly, similar throat loss to yours. Other barrels no where near as soft.
I have heard a few times the gunsmith saying, this barrel was lovely to machine, cut like butter, but as Ratshot said, didnt last long. These soft barrels were accurate, consistant and had a wide tune though?????
What brand is yours?

Steve 2141 · Post by **Steve 2141** » Fri Jul 15, 2011 3:11 pm

I had an improved 6br in a maddco 8" twist that shot extremely well, driving berger 105vld pills at 3050 ftps. I checked the lands every 200 or so rounds and adjusted the load, usually at thou or two, to maintain the same amount of jam

To shorten a long story, at around 2800 cycles I was loosing 0.001” of throat/lands per shot

cheers

RDavies · Post by **RDavies** » Sat Jul 16, 2011 5:27 am

So your thoat moved 2.8" after 2800 shots, that is one soft barrel.

Steve 2141 · Post by **Steve 2141** » Sat Jul 16, 2011 7:42 am

RDavies wrote:So your thoat moved 2.8" after 2800 shots, that is one soft barrel.

No, up to the 2800 cycle mark it the barrel had 0.034” throat loss, then it started to wear at that accelerated rate. In all the lands moved a total of 0.096

cheers

dave · Post by **dave** » Sat Jul 16, 2011 4:17 pm

barrels can behave similarly or be totally different in their characteristics. ie wear,fouling, accuracy etc etc.

my tobler 7mm (280ackley) now has around or just over 2000 rounds through it.
when new, projectiles left very noticeable land mark impressions.
at the same seating depth, 11 years later, land marks are still there but much less noticeable.

possibly the use of moly, increased leade angle and diligent care and cleaning may have also assisted in minimising wear????

all that matters, is that the shooter is still the weak link in the accuracy chain.

cheers
dave g

bruce moulds · Post by **bruce moulds** » Sun Jul 17, 2011 1:39 pm

my last barrel lost 0.060 for 1200 shots. both are 284 win krieger.
the previous one ran on 51 gn 2209, and the current one on 53 gn 2213sc.
when the 53 gn load is moved up a node to 55.2 is when the fouling appears.
both barrels have lost very little rifling in their early stages, getting faster as the shot count goes up.
possibly a longer neck would help. this raises interest in the 280 ackley.
a friend who shoots a 7mm saum reports similar throat loss using 2217 which reportedly burns cooler than many powders, even though he uses more of it.
recently seen on 6br is a 7mm cartridge with the saum body, but formed from 300 wsm brass, giving it a long neck. interesting ramifications.
bruce moulds.

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