Chambering With Resistance

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  • Last Post 08 March 2018
OU812 posted this 05 March 2018

Grease the locking lugs well.

I seem to shoot my best groups when ever the bolt needs to be forced closed. I know the bullet must fit snug without being pushed back too far into case, but consistent resistant bolt closing is important. As the throat erodes bolt closing will get easier. So seat the bullet longer to compensate and chamber pressures will have less spread or be more equal. smile

BTW I was really surprised to learn how quickly throat will erode. Especially when shooting lots of rounds and getting barrel hot.

I once read that antimony is very abrasive...? Or is the cleaning rod more abrasive?

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45 2.1 posted this 05 March 2018

You've learned why it isn't a good idea to use high antimony alloys. Antimony is very abrasive.... cleaning rods can do a number on throats or crowns dependent on just how they are used. There are a lot of ways around that!

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Ken Campbell Iowa posted this 05 March 2018

throat advancement ... i have mill sectioned a few p dog barrels ... pretty scary:

the throat doesn't wear evenly, like a perfect funnel ... it is more of a spiral groove/ditch, so setting a barrel back 0.1 inch at a time probably won't be like new . ( although some better ) .  which is why buying worn out barrels on ebay is a gamble ... sporters may not have enough receiver diameter metal left to easily set back ; varmint weights usually do.

those dang metal jacket bullets can still shoot 1.5 moa through a 2 inch long scaly non-concentric  worn out throat ...... depressing .

just some thoughts ... ken

 

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OU812 posted this 06 March 2018

Lilja started making 3 groove barrels because varmint shooters (hot barrel) were complaining of their six groove 22 centerfire throats wearing out too quickly. Lilja states "the throat of a 3 grove barrel will last a little longer than a 6 groove barrel and accuracy is about the same."

Uneven throat wear is not good. What causes it ?

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John Alexander posted this 07 March 2018

This may be an improvement for jacketed bullets but not so much for cast.

To the extent that deformation of the bullet by the side force needed to start rotation is a problem, it would be more of a problem for three as opposed to  6 or 8 lands if all else were equal (depth of groove etc.)  

On the other hand if the configuration of the rifling in a three groove barrel resulted in more bore diameter and less land diameter as a percentage of the circumference. It might provide more support i. e. guidance for bore riding bullets as two groove Springfield barrels are sometimes alleged to do.

Wouldn't it be nice if we had done more basic research over the years so we could use those resulting basic facts to answer such questions instead of fiddle farting around for a 100 years wasting our time by weighing bullets and varying loads by one tenth of a grain of powder between test loads.

John

 

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RicinYakima posted this 07 March 2018

John, Attached are two pictures; one is a target 10 shots at 100 yards with Lyman 48 from my Newton first model in .30 US Gov. The second picture is the bore profile; Newton - Pope.

Since the CBA doesn't have an iron sight sporter class, I can't shoot it in competition. And I am not going to drill and tap the receiver!

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RicinYakima posted this 07 March 2018

OU812, One of the other things it does is stops the bolt being pushed up by pressure on the sear with the striker under pressure. That some times lifts the top locking lug off the receiver and causes vibration issues.

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John Alexander posted this 08 March 2018

Ric,

With groups like that you could probably do OK in production or HR as it is.  That bore should be easy to clean. 

Is 30 US Gov. a 30-40, a 30-03, or 30-06?   I suppose I would know if I knew more about the history of the Newton's.

John

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Ken Campbell Iowa posted this 08 March 2018

Ric,  epoxy the scope base on, no screws.

ken

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RicinYakima posted this 08 March 2018

John,

.30 US Army is now called the 30/40 Krag

.30 caliber of 1903 is now called the .30-03

.30 caliber of 1906 was first called the ".30 US Government" on the commercial market, but shortened by the trainers in WWI to ".30-06" and was used by Winchester to mark Model 1895's. Newton marked all of his .30-06's ".30 US Gov" until he went broke the first time.

As a side note, Ideal reloading tools called the new rimless round the ".30-45" until Marlin bought him out in 1912 and they went to .30-06 also.

Ric

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RicinYakima posted this 08 March 2018

John, the bore is easy to clean although this one has a lot of dark stain. I bought it out of a leaking shed in Seattle and cleaned it up. I think because there are no corners, there are no pits. The throat is very gentle from the case mouth forward. There is not much area in the bore, as normal .30 caliber patch and jag is tighter than an '03 Springfield. Ric

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John Alexander posted this 08 March 2018

Ric,

I really appreciate that you share all the arcane history you have stuffed in your head with us from time to time. 

Another bit of trivia that I suspect you know is that some 1895 Winchesters were marked 30 caliber of 1903 or maybe it was 30-03 i don't have the rifle to remind me which.

With hammer forging apparently the cheapest way to make good quality barrels it looks like they should go back to that style of rifling. Making thee mandrels might be tricky but otherwise it would eliminate the need for sharp corners.  I assume Glock already has.

John

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