THROAT DIMENSIONS in 30-06's SPRINGERS

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  • Last Post 10 January 2008
linoww posted this 08 January 2008

What throating does your military 1903/03-A3's,or P-17's have?

What is the barrel make,is it new or worn out ???

How do you measure them accuratly? I use a lead slug in the throat. With a steel rod in a fired case(just below the end of the neck) and the bolt closed I whump it several times with a brass rod then knock it out of the chamber.Is this better than using Cerrosafe???

I am having a 190g plainbase bullet made for my HS Mfg barrels and am curious what dimensions others have to deal with to get bullet fit.My leade it shorter than most 1903 barrels I have used(or seen) and it seems to be shot a bit.

 

George

"if it was easy we'd let women do it" don't tell my wife I said that!

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Ed Harris posted this 09 January 2008

Pre-1940 military M1903s with original barrels have throating which resembles the current SAAMI chamber, with a .340” neck diameter, 4 degree Basic forcing cone from a .310 diameter entrance with no cylindrical ball seat.

Late production 03A1s and all 03A3s have a chamber throat which resembles that of the M1 Garand rifle, having a .3095” cylindrical ball seat .120 long, with 5 degree Basic forcing cone.

Nominal bore and groove dimensions are .2995” + .0015/ - .0000 bore and .3080” + 0.0015” / - .0000 groove.

WWI-era M1917 barrels often run much larger, some approaching .303 British bore and groove dimensions. These are difficult to measure accurately without a V-anvil micrometer, due to their odd number of grooves.

I designed the NEI #56 with two crimp grooves to enable seating to proper depth in either new or worn SAAMI chambers or military 03A3 barrels.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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billwnr posted this 09 January 2008

Ed, what about some 1945 barrels? Aren't they up to .311 because of “generous tolerances"?

I have an 03-A3 that usingthe bullets that I made for an older 1903 just drop down and if it wasn't for the driving bands would fall into or possibly all the way down the barrel (of the 03-A3).

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Ed Harris posted this 09 January 2008

Groove diameter “shouldn't” exceed .3095” unless the government's QAR signed off on them. Alot of surplus barrels were rejects that didn't gage up. Some ended up on marlin lever actions and 94 Winchesters until they were used up.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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CB posted this 09 January 2008

George,

I have several Sprg barrels in all varying degrees of wear. Most severely worn. I find the wear erodes in an equal ratio of diameter at the throat and the diameter down the length of the throat taper. That is; from an original .3095” throat opening and .2995” bore to a .312"/.301” or .313"/.302". This is usually what I find with a typical length bore-ride bullet like the Lyman 311299, 311290 and the 311284.

The old worn barrels will still shoot with bullets with diameter to fill the opening of the throat say at .313” and the nose to engrave in the lands at .302". The Lyman 314299 and the Lee 90371 mould works for the worn throats. I don't care what dimension the rest of the barrel is. CBE moulds also offers 30 caliber moulds with .312", .313", and .314” bases. I have one and really like it.

I just bought the Lee 90371 this winter and just cast with it the other day. The Lee two-cavity mould is a great mould. It has enough mass to cast well and a big sprue plate to open by hand easy. Out of the box, I casted 15 to 20 casts before it warmed up enough for good bullets. After another 20 casts, I lightly wire brushed the cavities with a stainless steel hand brush to get rid of the light remaining cherry burrs. Now the bullets practically fall out just as well as my Lyman moulds. The CBs are round and both cavities are identical!

I don't think it matters if you use Cerrosafe or pound in a slug like you say. Either way you need to know what you got, map it out with a micrometer and calipers on a sketch to keep for a reference with whatever bullet you try to fit..............Dan

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linoww posted this 09 January 2008

"I don't think it matters if you use Cerrosafe or pound in a slug like you say. Either way you need to know what you got, map it out with a micrometer and calipers on a sketch to keep for a reference with whatever bullet you try to fit..............Dan"

 

I've had skilled machinist types tell me cerrosafe is not as reliable as a lead slug as it has to be at room temp to get an accurate reading.I havnt found any trouble with this,but was curious about others experience.

I am pretty good at trig,so mapping the dimensions and angles is the sort of easy part.I keep slugs in medicine containers with notes in my shops cabinets.I usually make two of them just in case I didnt get good enough upset.

 

George

"if it was easy we'd let women do it" don't tell my wife I said that!

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CB posted this 09 January 2008

 

George,

I don't think you can rely on military chamber spec. throats as so many surplus Sprg rifles and barrels have been out in the public for so long, many have been tinkered with and finished chambered with the many various throat dimension 30-06 reamers on the market over many years. Cerrosafe is plenty reliable. As with any product, instructions need to be followed.

 

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RicinYakima posted this 09 January 2008

Dan and Geo.

Cerrosafe is effective, If you read the directions. The trick is watching the time. One hour after solidification, measure. Don't try to keep it for reference! The blurb says 0.0025 expansion at 200 hours. But what they don't tell you is that it is dependent upon thickness of the casting, the bigger it is the more it will increase, and it doesn't always stop at 200 hours.

Like Geo, I make a lead pounding of throats for reference. If I don't need it for reference and it is easy, I will use Cerrosafe.

Ric

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linoww posted this 10 January 2008

RicinYakima wrote: Dan and Geo.

Cerrosafe is effective, If you read the directions. The trick is watching the time. One hour after solidification, measure. Don't try to keep it for reference! The blurb says 0.0025 expansion at 200 hours. But what they don't tell you is that it is dependent upon thickness of the casting, the bigger it is the more it will increase, and it doesn't always stop at 200 hours. Like Geo, I make a lead pounding of throats for reference. If I don't need it for reference and it is easy, I will use Cerrosafe.

Ric

Thats why I went to the lead slug.My super duper machinist buddy said it's good for a quickie,but really isnt a precise way to measure down into 10'ths.

Geo.

"if it was easy we'd let women do it" don't tell my wife I said that!

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CB posted this 10 January 2008

I ain't gonna shoot the Cerrosafe slug, so just how perfect does it have to be! ;)

My final fit is always gauged by pushing the actual cb in the throat and inspecting the engraving.

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linoww posted this 10 January 2008

Dan Willems wrote: I ain't gonna shoot the Cerrosafe slug, so just how perfect does it have to be! ;)

My final fit is always gauged by pushing the actual cb in the throat and inspecting the engraving.

Shoot the cerrosafe........ i never thought of that.

I agree on bullet fit(and range testing)being the final frontier.

Somtimes its strange how a bullet that fits the throat like crap shoots at all.it seems to me lower velocity in the 1200-1400 range can work with undersized and longer bodied bullets real well at times.The nose guidance doesnt seem to be critical?Not match loads,but more than adequate plinking and offhand work.I once told a guy how his 311291 with a.314 body and .297 nose would scatter all up and down the paper in his '06 It shot into 2” and was a big eye opener and embarassing moment,me  being an “expert” cast bullet shooter <G>.

 

George

"if it was easy we'd let women do it" don't tell my wife I said that!

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RicinYakima posted this 10 January 2008

FINALLY got to measure a springer's throat this morning! He could get golf balls down, but choked on tennis balls. That really made his fur stand on end! So I'd say about an inch and a quarter.

Ric

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linoww posted this 10 January 2008

FINALLY got to measure a springer's throat this morning! He could get golf balls down, but choked on tennis balls. That really made his fur stand on end! So I'd say about an inch and a quarter.

Ric

I was waiting for someone to make a joke on that one.

George

"if it was easy we'd let women do it" don't tell my wife I said that!

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