.308 Springfield rcv'r built w/standard mil-spec kit. trimmed to 2.005 initially & only 4 full loadings with CCI#34's to avoid slamfire gremlins. used WLRP also. even w/clean chamber could/would an out of battery blow-up occur with following steps? I notice that the chambered rounds either surplus,FGMM,or my reloads will slam back the shoulder about a thousanth. If i only push the the shoulder back on FLS only a thou could i load the round up & let the chambering do the other thou on the shoulder giving a 2 thousanth total. I realize the generous chamber dimensions does not pretend to be of bolt linage. could this help accuracy measurably or help measure it for a box, as in early death wish. if a out of battery firing occurs it wouldn't be helped by the CCI#34's thicker cup. the touchier Federals have other assignments. Views please. keep your powder dry.
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could i set my M1A brass on shoulders back less?
- Thread starter chung400ramair
- Start date
Re: could i set my M1A brass on shoulders back less?
You want the round to fit the chamber with a little clearance. My procedure for sizing match loads is to use the FL sizing die to partially size the case enough to set the shoulder back to provide at least a .002 clearance of the loaded round in the chamber of a particular rifle.
This is to minimize brass stretching and only secondarily to help with accuracy. A match bullet and a tuned powder charge will be the most important accuracy factor. With a standard chamber, it doesn't matter much. FGMM shoots well with factory dimensioned cases.
As long as the chamber is clean and the brass provides that minimal clearance, there won't be any slam fire problems. The greatest risk is an out-of-battery firing, which is why shorter is better to avoid that under field conditions where grit might enter the chamber.
I am not sure about your exact question, but if I understand what you are trying to say correctly, you don't want the bolt to be sizing your case down as it chambers the round. You would essentially be firing ammo that is too long for the chamber, making an out-of-battery detonation likely, and that would be the worst possible outcome for safety reasons.
TC
You want the round to fit the chamber with a little clearance. My procedure for sizing match loads is to use the FL sizing die to partially size the case enough to set the shoulder back to provide at least a .002 clearance of the loaded round in the chamber of a particular rifle.
This is to minimize brass stretching and only secondarily to help with accuracy. A match bullet and a tuned powder charge will be the most important accuracy factor. With a standard chamber, it doesn't matter much. FGMM shoots well with factory dimensioned cases.
As long as the chamber is clean and the brass provides that minimal clearance, there won't be any slam fire problems. The greatest risk is an out-of-battery firing, which is why shorter is better to avoid that under field conditions where grit might enter the chamber.
I am not sure about your exact question, but if I understand what you are trying to say correctly, you don't want the bolt to be sizing your case down as it chambers the round. You would essentially be firing ammo that is too long for the chamber, making an out-of-battery detonation likely, and that would be the worst possible outcome for safety reasons.
TC
Re: could i set my M1A brass on shoulders back less?
You need to bump the shoulder back much further than 0.002" on a M14 action. The cases actually stretch longer than the chamber due to being under pressure when the extraction cycle begins. (The main reason that the M14 is so damn hard on brass!)
My opinion is you should set the shoulder back 0.004" to 0.006"(now that i think about it, it may even be greater than what i mentioned) from <span style="text-decoration: line-through">fired</span>chamber dimensions. And i would check the sized cases to see if they chamber without any resistance with the rifle stripped to just the bolt and receiver (bolt being stripped as well).
<span style="font-weight: bold">
http://www.zediker.com/downloads/14_loading.pdf
and
http://www.zediker.com/downloads/oncefired.pdf
Read this! </span>
In the end what it comes down to is shortened brass life vs. keeping your rifle (and your face) in one piece.
You need to bump the shoulder back much further than 0.002" on a M14 action. The cases actually stretch longer than the chamber due to being under pressure when the extraction cycle begins. (The main reason that the M14 is so damn hard on brass!)
My opinion is you should set the shoulder back 0.004" to 0.006"(now that i think about it, it may even be greater than what i mentioned) from <span style="text-decoration: line-through">fired</span>chamber dimensions. And i would check the sized cases to see if they chamber without any resistance with the rifle stripped to just the bolt and receiver (bolt being stripped as well).
<span style="font-weight: bold">
http://www.zediker.com/downloads/14_loading.pdf
and
http://www.zediker.com/downloads/oncefired.pdf
Read this! </span>
In the end what it comes down to is shortened brass life vs. keeping your rifle (and your face) in one piece.
Re: could i set my M1A brass on shoulders back less?
Just to be clear, the .002 number I was referring to was the minimum clearance of the loaded round to chamber fit. So you would need to size the fired case sufficiently to provide that minimum clearance regardless of how much it takes.
TC
Just to be clear, the .002 number I was referring to was the minimum clearance of the loaded round to chamber fit. So you would need to size the fired case sufficiently to provide that minimum clearance regardless of how much it takes.
TC
Re: could i set my M1A brass on shoulders back less?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Top Cat</div><div class="ubbcode-body">Just to be clear, the .002 number I was referring to was the minimum clearance of the loaded round to chamber fit. So you would need to size the fired case sufficiently to provide that minimum clearance regardless of how much it takes.
TC </div></div>
Good Point, I wrote it the wrong way in my above post.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Top Cat</div><div class="ubbcode-body">Just to be clear, the .002 number I was referring to was the minimum clearance of the loaded round to chamber fit. So you would need to size the fired case sufficiently to provide that minimum clearance regardless of how much it takes.
TC </div></div>
Good Point, I wrote it the wrong way in my above post.
Re: could i set my M1A brass on shoulders back less?
re:Agent Ronin,& TopCat, thanks for the thinking words. Zeidiker's material is gratefully received and it probably will be gone over many times. thanks for hard numbers to work around. I paralell your membership affiliations & a few others. going to round out my hobby with a Garand aquistion to help balance out my two standard M1As. was searching ways to better reload the pair. my double lugged lami-stock match '308 shoots generic PMC 168g fmj pretty tight & Federals 168g even tighter. trying to widen my experience in loading up 155g & SHPBT 175's to approach the Tikka 3 zone of happiness & beyond if i can, while enjoying reloading fun. there are two electric auto trim/chamfer devices i an looking at to to speed up the joy of trimming. thanks to both & others for factoids. keep your powder dry. gotta admit, those Tikka types sure are sleek. would do one as a project, SH overflows in info & possibles.
re:Agent Ronin,& TopCat, thanks for the thinking words. Zeidiker's material is gratefully received and it probably will be gone over many times. thanks for hard numbers to work around. I paralell your membership affiliations & a few others. going to round out my hobby with a Garand aquistion to help balance out my two standard M1As. was searching ways to better reload the pair. my double lugged lami-stock match '308 shoots generic PMC 168g fmj pretty tight & Federals 168g even tighter. trying to widen my experience in loading up 155g & SHPBT 175's to approach the Tikka 3 zone of happiness & beyond if i can, while enjoying reloading fun. there are two electric auto trim/chamfer devices i an looking at to to speed up the joy of trimming. thanks to both & others for factoids. keep your powder dry. gotta admit, those Tikka types sure are sleek. would do one as a project, SH overflows in info & possibles.
Re: could i set my M1A brass on shoulders back less?
400carbon you're quite welcome. I too am always on a quest to get a little bit better at my reloading techniques. Especially when it comes to the M1/M14. Now i just got to wait for my LRB M25 receiver to show up (put on the wait list in September, probably wont have it until May haha).
400carbon you're quite welcome. I too am always on a quest to get a little bit better at my reloading techniques. Especially when it comes to the M1/M14. Now i just got to wait for my LRB M25 receiver to show up (put on the wait list in September, probably wont have it until May haha).
Re: could i set my M1A brass on shoulders back less?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 400corbon</div><div class="ubbcode-body">[snip]I notice that the chambered rounds either surplus,FGMM,or my reloads will slam back the shoulder about a thousanth. [snip]</div></div>
That's common, not a sign of anything other than the extractor snapping over the rim. ALL Garands and M14-types *will* do that, regardless of any reasonable sized-to head clearance.
The big bugaboo for slam-fires is how far your firing pin can protrude past the boltface with the bolt all the way forward BUT just before starting to rotate towards locked. At that position, the firing pin *should* be fully retracted and be incapable of touching the primer at all.
You can test this with a sized and primed case and the action out of the stock. Run the primed case in the chamber, use the un-sprung oprod to snap the extractor over (I'm too lazy to remove the extractor) the rim, back the oprod out so the bolt is rotated unlocked but otherwise fully forward, and then use a hardwood or brass or aluminum rod to take a light hammer strike on the rear tang of your firing pin.
Eject the case and look at the primer. If you see any dent, take a picture of it and post here.
My first build had a chamber something like .007 longer than my reloads' headspace. Cases started breaking on reload #3. I don't do that any more.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 400corbon</div><div class="ubbcode-body">[snip]I notice that the chambered rounds either surplus,FGMM,or my reloads will slam back the shoulder about a thousanth. [snip]</div></div>
That's common, not a sign of anything other than the extractor snapping over the rim. ALL Garands and M14-types *will* do that, regardless of any reasonable sized-to head clearance.
The big bugaboo for slam-fires is how far your firing pin can protrude past the boltface with the bolt all the way forward BUT just before starting to rotate towards locked. At that position, the firing pin *should* be fully retracted and be incapable of touching the primer at all.
You can test this with a sized and primed case and the action out of the stock. Run the primed case in the chamber, use the un-sprung oprod to snap the extractor over (I'm too lazy to remove the extractor) the rim, back the oprod out so the bolt is rotated unlocked but otherwise fully forward, and then use a hardwood or brass or aluminum rod to take a light hammer strike on the rear tang of your firing pin.
Eject the case and look at the primer. If you see any dent, take a picture of it and post here.
My first build had a chamber something like .007 longer than my reloads' headspace. Cases started breaking on reload #3. I don't do that any more.
Re: could i set my M1A brass on shoulders back less?
thanks.Grump. checking the chamber w/cerro caste is in order. Agent Ronin's link to Zeidiker articles speaks of small base die only for his '308 use in M-14. it is for at least a '002 min shoulder set back from actual dimensions. at this point i am on the right track as to a measurement of clearence in reference the chamber. am away but when i get back in glendale, gonna find myself a wood wacker to institute your procedure to check primer appearence. so far all reloads have fired & ejected w/o anything abnormal. due to inherent design of the floating primer it is NORMAL for the primer to have indention upon chambering. i have carefully avoided any high primers by checking them upside down before putting powder in. apparrently do so enabeled my initial use of WLRP w/o hazards. so far any chambering indents are shrugged off. it seems as long as the chartridge chambers FREELY w/adequate shoulder set back it has avoided out of battery. OUT OF BATTERY is dangerous & since it needs happen only ONCE, i am happy to keep it on the sidelines untill it dies and fritter away.
thanks.Grump. checking the chamber w/cerro caste is in order. Agent Ronin's link to Zeidiker articles speaks of small base die only for his '308 use in M-14. it is for at least a '002 min shoulder set back from actual dimensions. at this point i am on the right track as to a measurement of clearence in reference the chamber. am away but when i get back in glendale, gonna find myself a wood wacker to institute your procedure to check primer appearence. so far all reloads have fired & ejected w/o anything abnormal. due to inherent design of the floating primer it is NORMAL for the primer to have indention upon chambering. i have carefully avoided any high primers by checking them upside down before putting powder in. apparrently do so enabeled my initial use of WLRP w/o hazards. so far any chambering indents are shrugged off. it seems as long as the chartridge chambers FREELY w/adequate shoulder set back it has avoided out of battery. OUT OF BATTERY is dangerous & since it needs happen only ONCE, i am happy to keep it on the sidelines untill it dies and fritter away.
Re: could i set my M1A brass on shoulders back less?
Don't know where Mr. Zediker got his information but there is more information to be had. The bullet is long gone before the bolt starts to rotate. The projectile takes much less than 1 millisecond to exit the muzzle. The bolt begins to unlock at 2.0 milliseconds. The bolt is fully unlocked and begins to move rearward at 2.8 milliseconds after the cartridge ignites.
Reference: Springfield Armory Research and Development Division Technical Report SA-TR11-2610 as reproduced in Stevens, R. Blake. U.S. Rifle M14 from John Garand to the M21 Revised Second Edition. Collector Grade Publications: Cobourg, Ontario, Canada, 1991: pp 183 - 186.
Blake came to Picatinny when he was doing research work on the M14 and visited our office and came to our appartment. He was given lots of good info by the folks still there that worked on the M14. The technician that did all the M14 drawings just died about six months back. Nice guy.
I have a copy of SA TN11 1094 which gives timing analysis comparisons between the M1 Garand and the M14.
Initiation time (in milliseconds) of operating rod recoil for the M1 Garand was 1.58 and the M14 was 1.53.
At op rod initiation the M1 bullet exited the muzzle and traveled 7.2" where the M14 bullet had exited the muzzle for 9.2".
At the conclusion of bolt unlock the bullet had traveled 88.9" with the M1 and 123" from the M14 muzzle.
This correlates with the high speed film I saw filmed at SA wherein an M14 was fired a multi round burst with one pull of the trigger and the whole mag was filmed. This film was located in the archives of the Army Small Cal Lab when I worked there and we viewed a number of previously classified films prior to their destruction as the paperwork to declassify them would have taken months and there was nothing on them that was not common knowledge at that time.
The function of the M14 is amazing, This film took perhaps five minutes to watch just a few rounds fired and everything was slowed down to the point the manufacturer and date thereof could be easily seen on each case as it spun out of the rifle.
I clearly remember seeing the hammer slowly pivoting up to strike the tail of the striker and the immediate stiffening of the bolt. The bolt quickly relaxed and was not under any tension. This was prior to any movement of the op rod which when it starts its rearward travel the roller bolt is engaged in a rather violent fashion. The roller of the bolt was struck two to three times raising it a bit each time and finally it achieves the top of the travel and the bolt starts to the rear, the next round came up and was picked up and fed forward. The bolt gets to the end of the travel and another series of jerky movements occurred as the bolt was rotated into battery. The bolt bounces around a bit and finally comes to a complete stop about the same time the op rod ceases to move forward. Again the bolt is relaxed and the hammer is then seen to move toward the striker to fire the next round.
There was also the capability of photographing bullets in bore at any position in it's travel.
What is not widely known is all M14 bolts have cracks at the rear of the locking lugs where it intersects the bolt body.
I had Engineering responsibility for the M14 Rifle and the M21 at Picatinny Arsenal after the move from Rodman Lab and thusly when I read the above statement I knew the facts to be different. Took a few phone calls but I finally located the data and the source thereof which is Springfield Armory where it was designed.
Don't know where Mr. Zediker got his information but there is more information to be had. The bullet is long gone before the bolt starts to rotate. The projectile takes much less than 1 millisecond to exit the muzzle. The bolt begins to unlock at 2.0 milliseconds. The bolt is fully unlocked and begins to move rearward at 2.8 milliseconds after the cartridge ignites.
Reference: Springfield Armory Research and Development Division Technical Report SA-TR11-2610 as reproduced in Stevens, R. Blake. U.S. Rifle M14 from John Garand to the M21 Revised Second Edition. Collector Grade Publications: Cobourg, Ontario, Canada, 1991: pp 183 - 186.
Blake came to Picatinny when he was doing research work on the M14 and visited our office and came to our appartment. He was given lots of good info by the folks still there that worked on the M14. The technician that did all the M14 drawings just died about six months back. Nice guy.
I have a copy of SA TN11 1094 which gives timing analysis comparisons between the M1 Garand and the M14.
Initiation time (in milliseconds) of operating rod recoil for the M1 Garand was 1.58 and the M14 was 1.53.
At op rod initiation the M1 bullet exited the muzzle and traveled 7.2" where the M14 bullet had exited the muzzle for 9.2".
At the conclusion of bolt unlock the bullet had traveled 88.9" with the M1 and 123" from the M14 muzzle.
This correlates with the high speed film I saw filmed at SA wherein an M14 was fired a multi round burst with one pull of the trigger and the whole mag was filmed. This film was located in the archives of the Army Small Cal Lab when I worked there and we viewed a number of previously classified films prior to their destruction as the paperwork to declassify them would have taken months and there was nothing on them that was not common knowledge at that time.
The function of the M14 is amazing, This film took perhaps five minutes to watch just a few rounds fired and everything was slowed down to the point the manufacturer and date thereof could be easily seen on each case as it spun out of the rifle.
I clearly remember seeing the hammer slowly pivoting up to strike the tail of the striker and the immediate stiffening of the bolt. The bolt quickly relaxed and was not under any tension. This was prior to any movement of the op rod which when it starts its rearward travel the roller bolt is engaged in a rather violent fashion. The roller of the bolt was struck two to three times raising it a bit each time and finally it achieves the top of the travel and the bolt starts to the rear, the next round came up and was picked up and fed forward. The bolt gets to the end of the travel and another series of jerky movements occurred as the bolt was rotated into battery. The bolt bounces around a bit and finally comes to a complete stop about the same time the op rod ceases to move forward. Again the bolt is relaxed and the hammer is then seen to move toward the striker to fire the next round.
There was also the capability of photographing bullets in bore at any position in it's travel.
What is not widely known is all M14 bolts have cracks at the rear of the locking lugs where it intersects the bolt body.
I had Engineering responsibility for the M14 Rifle and the M21 at Picatinny Arsenal after the move from Rodman Lab and thusly when I read the above statement I knew the facts to be different. Took a few phone calls but I finally located the data and the source thereof which is Springfield Armory where it was designed.
