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Sawbones
On Point Joined: Mar 04 2022 Location: Texas Status: Offline Points: 152 |
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Posted: Apr 06 2022 at 6:22pm |
Reloading fired once Sellier & Belloit brass length trimmed to 1.280", CCI primers, 110gr FMJ, Overall Cartridge Length 1.677" Weighed H110 powder on RCBS Charge Master electronic scale. Averages: 14.0gr H110---- 1863f/s 14.5gr H110---- 1943f/s 15.0gr H110---- 1968f/s Shot from early Q.H.M.C. Carbine #1583865 ROCK-OLA barrel BTW, spent cartridge lengths varied from 1.280" to 1.940"; most were 1.282" -1.284". H110 and Win 296 share identical burn rates (Source Hornady and Lyman Reloading Manuals and various internet sources) |
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"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
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Timothy
On Point Joined: Jan 13 2022 Location: Crossville TN Status: Offline Points: 109 |
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Thanks for the data points.
Any particular reason for choosing 1.677 for OAL? I haven’t deviated from my Hornady book yet - I’ve been using the recommended 1.680”. Just 3 mils difference I know, and perhaps you are just keeping a margin below max. But your post got me to wondering the effect of OAL on a cartridge that head spaces on the case mouth.
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T R
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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The fact that it does head space off the case mouth allows the OAL to vary without affecting head space. Longer only limited by contact with the rifling, shorter to the extent it might affect pressure, assuming the same projectile is compared. Of course some lighter projectiles will be seated below spec OAL. I seat Mauser 86-grain RNSP to around 1.62, they have to be seated deep enough to obtain adequate neck tension. The shorter OAL would present additional freebore, but I think one would have to get pretty scientific to be able to measure pressure changes or accuracy differences. Most commercial ammo that I have measured is rarely if every right on 1.68 and usually closer to 1.67.
Not saying accuracy is not affected by variances in OAL, but the average carbine shooter would likely not notice or care. I doubt that varying OAL by 2 to 3 thousandths is going to make much difference.
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Sawbones
On Point Joined: Mar 04 2022 Location: Texas Status: Offline Points: 152 |
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My goal was 1.680" but didn't quite make it and it was of no consequence to me. Down to the 0.001" precision is not necessary here. In the circumstance of the WWII 30cal M1 carbine 0.003" plus or minus is not significant because one must consider the fact we don't know how many rounds have been fired out of each of these relics hence one does not definitively know precisely where the headspace begins or ends or where the lands begin in each and every M1 carbine in existence. Those factors are unique to each and every M1 carbine. I think my Q.H.M.C. carbine was a closet queen since birth and never on the battlefield so the headspace/rifling is probably near pristine but, of course, the M1 carbine by design was never to be tack-driver precise and accurate. |
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"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
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Sawbones
On Point Joined: Mar 04 2022 Location: Texas Status: Offline Points: 152 |
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To Timothy, More on OAL OAL as found in the Hornady Reloading book 1.680" is the maximum over all length. It can certainly be shorter depending on what a rifle likes. Know this: each rifle is like a mean mother-in-law w/ bad ovaries: Ya never know what will please the old bag until you divorce her daughter. I've rifles that like long jumps (ogive to rifling) [shorter OALs] and rifles that like shorter jumps (ogive to lands) [longer OALs]. As you know there are many factors influencing precision/accuracy. I've been struggling w/ a Mannlicher-Schoenaur .270cal for many years and can't get any acceptable MOA out of it. I've a Model 43 Winchester .218 Bee (born ~1950) I've fine tuned to 4 shots/one hole at a hunnerd yards. |
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"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
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Smokpole
Hard Corps Joined: Oct 21 2019 Location: Madison ohio Status: Offline Points: 1058 |
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"The fact that it does head space off the case mouth allows the OAL to vary without affecting head space. Longer only limited by contact with the rifling..."
Floyd, Longer is limited by the mag unless you are single round loading. Too long and they won't go into the mag. |
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Timothy
On Point Joined: Jan 13 2022 Location: Crossville TN Status: Offline Points: 109 |
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Thanks Sawbones - for the thoughts and the plain talk. BTW I am pretty sure my mother in law no longer worries about ovaries (life is good) and ps I’m keeping the daughter!
I do get the message from Floyd and Smokepole and others that the .30 cal may not be the best platform from which to learn how fine-tune reloads so as to ‘dial in’ performance. However….. … in a general sense it IS interesting/fascinating to try to understand the affects that the variables in a particular rifle (as you mention) and cartridge load may have on overall performance. Maybe one of these days I’ll try stepping up from current .30 and .45 and 9mm cartridge repertoire and try reloading rounds for my Dad’s .30-06 Remington towards learning more along these lines. V/R Tim
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Rebel92
Grunt Joined: Jul 20 2021 Location: Hattiesburg, MS Status: Offline Points: 541 |
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I decided to measure some of my unshot milsurp, the OAL, I measured some Evansville brass I have from 1944, it’s OAL was 1.65-166.
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Flypa38
Recruit Joined: Feb 10 2022 Location: Pittsburgh, PA Status: Offline Points: 1 |
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Another note on OAL. Probably doesn't matter much here, but measuring from the bullet ogive is a much more accurate method of measuring because of slight manufacturing variances. For example, I was getting differences up to .008"s when measuring from rim to tip with a dial caliper, but ogive to rim was spot on for .303 British. Probably would never be able to tell the difference in .003" in regards to accuracy, and pressure difference would most likely also be negligible.
Just something I learned that made me feel a little better about OAL not matching exactly what the book says.
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David Milisock
On Point Joined: Aug 03 2019 Location: USA Status: Offline Points: 334 |
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Tolerance is important, the more accurate the game the more important they are. My 30 Carbine hand loads out perform any factory loads I've ever bought. I rarely trim, I measure and anything over size goes into a trim later container, (I have thousands of brass) I use a balance scale and a powder measured. I throw powder until it weighs correct, load and weigh 1 in 10. I shoot groups that stay inside the 6" center of a 9" paper plate at 200 yards from prone or a rest. I use the standard upgraded military ramp sight. The sights are combat sights but I do not expect much improvement if I upgraded them.
My bolt varmint rifles I weigh each charge and shoot 1 1/16" groups at 300 yards from both of them and one 35 caliber magnum that performs the same.
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David Milisock
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