Test of Mosin Nagant barrel length reduction

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czharry
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Test of Mosin Nagant barrel length reduction

Post by czharry » Wed Apr 03, 2013 1:08 am

A USF student did a thesis on the affect of reducing the barrel length of a MN. It's a PDF, and pretty interesting.
Test of MN barrel reduction on report and accuracy
Found this online, done by a college student in Florida. Interesting read with numerous photos. Looks to be a thesis for college.
He performed tests on a Mosin, reducing barrel length in 2" steps, with recrowning each time, from 28.75" down to 16.75".
He admits certain variables, but to me his target photos clearly show when the barrel got down into the 24-25" range the accuracy increased, with not much reduction in bullet speed or power, although the muzzle blast level did increase a bit.
Take a look.
http://honors.usf.edu/documents/Thesis/U82488180.pdf
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Re: Test of Mosin Nagant barrel length reduction

Post by jjk308 » Fri Apr 05, 2013 9:52 am

Not necessarily true. Barrel length affects the barrel vibration frequency and amplitude on firing so stock fitting would have a very large impact on the change in accuracy. The tests account for this by removing all the stock around the barrel, but in the real world this isn't possible. Military rifles have the additional complication of bayonet mounting.

Mauser reduced vibration and increased accuracy with a thicker barrel, with steps so the weight could be kept down and expansion in length easily handled in the stock.

100 to 150 fps velocity reduction for every 5 inches is a good rule of thumb.
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czharry
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Re: Test of Mosin Nagant barrel length reduction

Post by czharry » Fri Apr 05, 2013 12:15 pm

I just took a look at the muzzle end of my 91/30. No bayonet mount. I'm somewhat familiar with barrel harmonics, but also take into account of hunting rifles that have short forends and long barrel lengths. I forget if this barrel is stepped, but I've seen it in some of my milsurps.
It was a good effort.
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