http://thefiringline.com/forums/showthread.php?p=5424409
Your test vehicle is likely to give different results because a bolt gun is a totally different animal than a gas gun. IF your rifle is set up right both lugs are contacting equally and the barrel may be contacting front of receiver 360° around and your bolt face may be square.
The M14 in issue condition is known as the worst performing rifle we ever fielded. I worked product engineering for the Army Small Cal Lab at Picatinny Arsenal and I had engineering responsibility for the M14 until the Chief transferred me to the Dover Devil MG project. While there my board was adjacent to Julio Savioli who was the draftsman for the M14 rifle and his name is on all the drawings for it. Al Cole was engineer in charge of the M14 and he was also a friend. Savy (as we called him) was a wealth of information on the M14 and had all kinds of stories about it as he not only did the drawings, he was in on the field testing.
First off consider the requirement facts from the engineering files from the government weapons production efforts.
1. acceptance accuracy for 1903 Springfield was 3" at 100 yards.
2. acceptance accuracy for M1 Garand was 5" at 100 yards.
3. acceptance accuracy for M14 was 5.5" at 100 yards and was waivered continually as it could not meet that.
4. acceptance accuracy for M16 series is 4.5" at 100 yards.
From SAAMI we have a recommendation of 3" at 100 yards and it is up to the vendor whether he wants to meet this or not.
H&R also made M14s and M1s and the contracts were shut down due to poor QA.
The M14 if rebuilt correctly and very few can do so is capable of acceptable accuracy. For instance the Army MTU rebuild program with rifle fired from machine rest was 10 shots in 4.5" at 300 yards. Some would go to 3" but rarely. A good bolt gun will shoot in 2" at 300 yards.
The TRW weapons were at one time thought to be good but MTU set up some exotic measurement fixture and figured out the threads in the receiver were not at right angle to the front of the receiver and from then on all their builds were on SA receivers.
If you will get a copy of Hinnant's book entitled "The Guide to Precision Rifle Barrel Fitting" you will read about a lot of the headaches manufacturers allow to get out the door even with bolt guns.
The out of square problems Bart refers to is really quite common in many vendors weapons. On a bolt gun these are easily corrected with a good lathe.
Check out
http://www.bryantcustom.com/articles/true.htm which will give you a working knowledge of what has to be done to make a rifle shoot well.
These processes while they can be done on a M14 are problematical because if you chuck up a M14 receiver to square the front of the receiver and you take material off the front of it, that destroys the thread timing for the barrel.
Military rifles are set up to be rebuildable at depot by just taking off a tired barrel and replacing with new. The new barrels have the threads timed so that it will snug up right before 12:00 o'clock and the barrel can be torqued on. Thusly the interface of the receiver and barrel contact points is extremely critical and must be controlled to tight tolerances. If material is removed from front of receiver the replacement barrel will not contact the shoulder with enough "crush" to have the barrel "time up" at 12:00 o'clock.
Now with after market barrels you can square the receiver face and twick the barrel to get it to time at 12:00 a bit easier but squaring the threads is still problematical.
The 1903 and 03A3 rifles were built the same way and they too have thread alignment issues. For instance I had a barrel all threaded up for 03A3 and I had three actions with no barrels that had been squared. I screwed that barrel into one receiver and it contacted first a 4:00, the next one contacted at 9:00 and the third one contacted 360°. Which means the threads were out of square on the other two actions and on the money on the third one.
The M14 can have other problems wherein the bolt lugs don't bear equally.
A quick and dirty way to tell whether you have a problem is to examine your striker indent on a fired case. The ideal barrel to action set up is to have the bore center line of the barrel and the bore center line of the action in perfect alignment. If the barrel threads are out of square the line has a bend and it first shows up as off center striker hits. You will also find bolts with striker openings drill off center as well.
The industry "recommendation" allows for 1/2 the diameter of the striker indent to be off center. Medium bolt strikers measure around .060 diameter thusly the off center condition can be .030" out of alignment.
Frankford Arsenal tested millions of primers in a big study in the 50s and it was determined the offset of the striker indent had no detrimental ignition reliability up to .020" offset but after .020 the misfire rate is increased dramatically. Bottom line is the ammo boys determine reliability is compromised over .020" and the weapon boys produce rifles with .030" offset to meet production. It is a fact of life in mass production.
Now if you want to see precision take a look at the Barnard actions and the other actions the current crop of Palma Team shooters use. Their cases come out and show visually dead center striker indents and the rifles all shoot very well.
As Bart indicates you still have the problem of out of square case heads and bolt face out of square problems. If you will dig back about 1978 time frame there was a big article by a guy named Creighton Audette who did a lot of study on this and determined out of square case heads set up even more problems and if your bolt face is out of square, the threads are out of square and the bolt lugs don't contact evenly then you have compounded problems.
So basically while your rifle may shoot much better than others is it perhaps the fact is yours has a straighter bore/action centerline, lugs contact and bolt face is more square.
Case in point I had a new commercial rifle I got in 2005 and it shot horizontal groups that holes tended to touch or almost touch. I had a looksee at bolt lugs and bottom lug was not touching. I lapped in top lug and rifle started shooting round groups.
There are other problems to be experienced such as barrel is not properly stress relieved and starts to walk. Worst I ever had was a H&R breakdown rifle in 223. It consistantly shot a 3 shot group 1.5" wide and 10" high at 100. A call to H&R revealed they did not stress relieve barrels at all. They replaced barrel and it shot 2" at 100 in a round group.
I had two very good friends who were the ordnance types for the US Secret Service. One was formerly an ammo tech at Frankford Arsenal and the other built the ammo acceptance rifles while there. At USSS they did similar except one built all the sniper rifles. They too told me that their testing with Fed Match showed what Bart has alluded to. With their budget they could handload every last round for their counter sniper rifles yet they do not.
The problem is finding factory ammo that shoots well in the first place as most factory ammo has cannelures which is a perfect thing to do to a bullet to destroy it's accuracy. Mass produced hunting bullets for the industry can be bested by using Sierra matchkings about 99% of the time so if you test hunting ammo and then handload Sierras your data will show handload is best but it is because of the quality of the projectile thus your data will be skewed.
This by no means is a complete list of problems that can be encountered and need to be overcome to achieve that one hole rifle. Bart has been around the block a few times and has experienced things 99.9% of others never dream about.
On my gas guns I FL size. If I place round in chamber I ease the op rod about half way down and release it. If I am necking only with a gas gun I will load them long to be close to the lands (within .020") and place in chamber with easy let down. Also my gas cylinder plug has an extra vent hole to bleed off port pressure a bit. My Tanker Garand has a much larger hole in gas plug to bleed off excess pressures so ejection angle is correct.
I also apply Mobil 1 synthetic motor oil to gas ports or let run down op rod to keep the carbon build down.
In standing I will just pop round in mag and drop it. On my bolt guns most of them I FL size for with dies matched to the chamber so I don't move brass over .002" when sizing. Some I neck size the entire neck only and not the body. Some I partially neck size but on my bolt guns the chambers are much tighter. I guess you could say on the whole I FL all rapid fire. If you will look closely at Fed Match you will see a transistion angle between neck and shoulder that is not duplicatable in FL or Neck dies.
If you have a chrono you might also check your SD for a 30 round string between FL and neck sized. Basically shoot ten and tally, shoot next ten and tally and last 10 and tally. Shoot at 45 second intervals. You may well find a significant difference. SD of 10 or less was Marine Corps ammo room standard at Quantico for Marine Corps team.
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Distinguished Rifleman High Power & Smallbore Prone
President's Hundred (Rifle) US Palma Teams(2)
US Dewar Team (2),4 Man Natl.Champ Team
My Notes:
“Rifle U.S. Cal 30, M1, National Match 1957”. I think this was handed out at the National Matches because it was written as an informational brochure on the NM rifles of the year.
Section 5. Accuracy Firing
a. With the rifle supported in a rifle rest three ten shot groups are fired at 1000 yards for accuracy using match ammunition. The average extreme spread of these groups cannot exceed 4.2 inches. Any one ten-shot group making this average cannot exceed 5.7 inches extreme spread. If these requirements are not met the rifle is rejected.
b. Figure 24 illustrates the distribution of averages of three ten-sho groups for 655 National Match Rifles targeted in this fashion. It is to be noted that all rifles to the right of the 4.2 inch line were screened out; the average of those accepted was a 3.4 inch average group size and eighty-eight rifles averaged three inches and under for three ten shot groups.
