This is one of the "never sell" rifles in the SP armoury. I stumbled into some 7 years ago and my son will be making his debut appearance at camp Perry in 2020. This is the rifle he'll train with this summer,. Some of you older gents may remember Don (Mac) McCoy.
-------------------------------------------------------------------------------------------------------------------------------------------------
This was communications between my Son and two Grand Masters familiar with the rifle, at least by reputation. The other two Grand Mastered multiple times at Camp Perry. Some comments were mine.
============================================================================================================
Any Ideas on this?
This is a one of three Garands built by Don McCoy in this specific manner. The 190gr projectile is specified, and now I should be explaining what we found on our range today.
The rifle sent all 8 rounds downrange in a single trigger pull . The barrel has been hBN sealed and we're shooting 175SMKs, impact coated. Chrono shows a nominal 2,475. There's no doubt that the gas port is set to accommodate the 190s without damaging the op-rod.
This is the rifle.
This was the original explanation.
----------------------------------------------------------------
Noted Garand competition builder and accuracy specialist Don McCoy of Santee, CA, built this M1 for me in 2001. It is built on a selected Springfield receiver (1943 manufacture date), and has an Obermeyer 5R barrel with 1:10 twist. It is designed to shoot 190-grain bullets with exceptional accuracy out to 1000 yards.
This rifle has numerous custom accuracy features, including a lugged receiver, glass bedding with additional custom fabricated steel plate fittings that tie the receiver into the bedding with 3 bolts, ½-minute rear sight, reaming to ensure barrel & gas cylinder clearance as well as machining the end of the gas cylinder for stock clearance, and many more machined accuracy refinements. The forward hand grip is also glass bedded with attention taken to ensure complete clearance for the op-rod. The heavy stock is English walnut with a Fullerplast finish as only McCoy can do.
The 2-stage trigger is extraordinarily smooth and makes the rifle a joy to shoot. The rifle has approximately 40 rounds through it. It was function-fired by McCoy and later broken-in by myself using Tetra Gun followed by a dry patch every round for the first 10 rounds, every other for the next 10, and then 5 + 5 for the final 10 rounds. After the last 5 rounds it was immediately cleaned with Tetra Gun, dried, and a patch with Militec-1 lubricant was run down the bore while it was still hot. After returning from the range, the bore was cleaned with Sweets 7.62, followed by Tetra Gun. Lastly a patch of Militec-1 lubricant was run down the barrel. All cleaning & lubrication/protection was run from the breech to the muzzle.
From here on out, the rifle will clean up easily with either Tetra Gun or Kroil, followed by the Militec-1 for conditioning and as a protectant/preservative. An application of Sweets 7.62 every 200 rounds or so will help prevent copper build up. The purchaser will get the fired brass from the break-in session.
This rifle is one of only three like it that McCoy has built in his long career building match Garands. His clients include some of the top High Power competitors and collectors in the country. I have a McCoy M1 in .308 with an Obermeyer 5R 1:11 barrel, which I fired in many High Power matches with great success.
A fine, accurate, and unique rifle from one of the outstanding M1 accuracy specialists at the peak of his career.
I also have video of McCoy in his shop going over the features of this rifle which I'm sending with the rifle.
-----------------------------------------------------------------------------
By "one of three" I didn't know what he meant until the video on the rifle arrived. It was made by McCoy explaining the exact constrution of this rifle by serial number. Beside every aspect of the rifle being bedded, its triple pillar bedded. I'll post another picture of those pillars as soon as I get my sister in town to forward them our here.
So, should I be using 190's exclusively or can I simply boost the charge to obtain the right pressures?
---------------------------------------------------------------------
This was a question by a Garand competition shooter.
"The next question I have is how do you know the McCoy rifle you have was built to fire only 190 gr. bullets."
----------------------------------------------------------------------
Because McCoy made a point of it in the DVD he made for this rifle.
This is the bedding. Note the three welded pillars and the corresponding bedded receivers in the stock.
It seems that Mr. McCoy and I will be speaking today. He feels there may be a timing problem. He's very ill now and I won't be taking much of his time. With his advice I intend to solve it here. I posted this in case you gents thought of something I've missed. I was hoping to not have to bother him at all if it appeared to be something obvious to you. I suspect pressures too low may be involved, but I've never dealt with a M1 that was a custom build.
Thanks for any advice.
BTW........ Close examination of the trigger group shows a positive lock up and plenty of hammer/sear contact before release. The trigger seems to be a 4.5 pull.
Makers Medallion.
Stage one.
Stage two.
Any ideas at all? Dumb in the first place to try a 175 in lieu of a 190? Any ideas before we bother Mr. McCoy?
Latigo
CDR Xfire
Latigo,
Mac adjusts his triggers to the absolute minimum sear engagement, with most of the weight in the first stage. I was sure that mine would double, but it doesn't. It has been very, very dependable. But mine is single lugged only at the back. (I went and dug my triple lugged rifle out of the safe a while back ... it was built be Clint Fowler, and the forward lugs are slightly different and located more forward).
These rifles are meant to be fired with the buttplate HARD into your shoulder, even in offhand where you can't use the sling. If you use a "soft" hold as in benchrest shooting, you are probably bump-firing it. The combination of the way the rifle recoils, and the trigger technique ("milking the trigger") will make it double, or even simulate full auto fire. I can do this on purpose, it gets folks attention with an M1A and ten rounds in the magazine. (if you are using your mechanical rest, you may get the same efect)
I would fire it in a good solid prone postition with a tight sling. If you want the security of a rest for ammo testing, put a sandbag under your gloved hand. If it still doubles, do the same with M72-equivalent 173 or 175 grain loads. If it still doubles, it needs some attention. The Easy Button would be a new hammer tuned for a bit more sear engagement. If all this doesn't work, then you need to talk the The Master himself. The "unkown" to me is how Mac's forward lug system may effect the way the rifle flexes under recoil forces, and how that may effect the minimum tolerable sear engagement.
Hope this helps ...
Resp'y,
Bob S.
think it does help. I was prone with the rifle bagged fore and aft. My usual way to pull the trigger on any rifle is to pull with folllow through and hold the trigger to the rear before making a conscious release............................. but considering his trigger setup, now I'm not so sure.
After doubling, I extracted the next chambered round and we noticed the primer was dimpled. I also think I remember having pulled the trigger after doubling and there was no release, just as if the hammer had not reset at all. I cycled the bolt and it fired the next chambered round ok.
Ok, so the load was with a FLS case, TTL less than manual length, primer seated just below flush, 175gr SMK seated 10 thous off the lands, 45.5gr of 4895 and a MV of 2540. I had a guy tell me about the US Army Manual data book listing the 173gr with 50gr of 4895. It sounded way wrong so I googled it and found there had been an error in TM 43-0001-27 saying that 50gr of 4895 was a match load with the 173gr projectile. I'm thinking now that I should have been at 46.5gr of 4895 anyway to make things work with the right MV and pressures. With a gas port tuned specifically for a 190, can chamber pressures that are too low cause any of this?
And the soft hold sure could have happened. I was excited about the whole thing anyway.
Don (Mac) McCoy, now in his 90's and I just spoke to him and his protoge on the phone. Too much info to type right now, but I'll be back after we implement everything he asked us to do with the rifle with full explanations.
Latigo
I was able to speak with Mr. McCoy last evening, probably for the last time. His protoge is taking over everything very soon now and I don't want to bother him again. At age 92 he doesn't need to be answering questions from someone into his first Garand. He was good enough to explain the exact nature of the rifle to me.
He said there is not a mechanical way for that rifle to double. It was all me. His exact words were, "Chamber each round with your fingers. Don't use one of those single round setups. Let the bolt close narurally. Breathe on that trigger, don't just pull it. Do all that and you'll be shooting right along with the best of them, but only if you're capable. The rifle already is. It was designed for 190s, so use 190s. The load we gave you is for military brass. Use it."
The gent taking over all of it is Mark Hendricks. He's been studying under Mr. McCoy for a long time and it now ready to keep the shop running with the same quality Garands. He's avaliable to me anytime I want to call, so I'm sure I'll have more questions later. We loaded 190 SMKs with Mr. McCoy's load data last night and we got load data from Mark for 175 SMKs as well.
I'll post targets after we take it all out to our range saturday or sunday. Its still pretty cold here so we'll be shooting from our ShootShed at the 100 yard mark. Its going to be a fun summer.
One thing I forgot. His load data is hot! A few of them with amounts over book maximums by a full grain, and one that's two grains over.
�
David, this is the C/C communication we received between J. Sopko and RL Steinberg, both of the other two multi Grand Masters. Distinguished Naval Marksman RL Steinberg is the one who proofed our new Type PS 1,000 yard Diopter at Quantico. The same one you have.
P
===========================================================
Hi Joe, (Joe Sopko)
Yup, exactly!
I cut and pasted your earlier reply on this subject and sent it to the fellow in Montana and it turns out that it wasn;t Mac that told him to neck size, it was Mark. Anyway, he is going to take your advice about bumping the shoulder back. That's exactly what I would have told him too, but I thought your advice would have more credibility than mine
I remembered the story of Dave Fiehtner blowing a Navy Mk2-1 apart with the 190 SMK load. It turns out that someone told him to seat the bullet WAY out to jam them in the lands ... and the result wasn't pretty, either ... slam fire with bolt unlocked, rifle came apart in two major pieces and a bunch of little ones. He was fortunate that he was not seriously injued.
More later .....
Bob
-----Original Message-----
From: Joe Sopko <[email protected]>
To: Rls1998 <[email protected]>
Sent: Sat, Dec 17, 2011 5:31 am
Subject: Re: Resizing for LR
Hi, Bob,
I was just thinking about a more fundamental issue. It's not possible to successfully only neck size brass from an M1 or M14 since the brass is ejected hot and continues to expand unconstrained after ejection. The ejected brass is often ~.005" or more larger than the chamber. It's also one reason that service rifle brass doesn't last as long as a bolt gun. All these are reasons that I'm becoming a believer in using headspace gauges with service rifles. Another story Mac told me was that he built an M1 with a tight (benchrest-type) chamber for someone many years ago. Even though Mac warned against it, that person was adamant about it and is a person that should have known better. So, Mac built it for him with a lot of caveats. The result was not good.
Joe
On Dec 13, 2011, at 9:18 PM, Joe Sopko wrote:
Hi, Bob,
For my 308 Win Mk2's, I full length/small base resize all my brass. I found that a headspace on Mac's rifles need to be setback a couple more thousandths than normal. I set them back about -0.003-4" from zero. I agree that neck sizing for an M1/Mk2/M14/M16 is not a good practice.
Now, I don't have any of his 30-'06 rifles, although he tried to convince me for years that it would be a better long range gun. Since that would be a different reamer, I can't say if the headspace is the same due to gunsmith technique or due to a worn reamer. I asked Mac about the characteristics of his 308 chamber a few years ago and all he told me was, "I only have one reamer for 308."
Mac was one of those masters that if he told you to do something, it usually was what you should do. However, I'd try FL SB first at zero headspace. Then, bump it back a few thousandths and see which shoot better.
Another option is to call Mark Heckman who took over for Mac. He may have some better insight (Mark Heckman <[email protected]>).
Joe
On Dec 13, 2011, at 5:19 PM, Rls1998 wrote:
What are you doing for brass prep for your MR and LR gas gun loads? Just FL? Body die to bump the shoulder back a controlled amount? Other?
TIA!
Bob S.
I've been mostly a bolt gunner since we retired, but I've thought about this particular part with the gas guns a bit. Since the case comes out HOT as you note, and continues to expand without the restraint of the chamber walls, it is larger than the chamber. As the case cools back to ambient, you recover SOME, but not all, of that expansion in the neck and shoulder area since the brass in that area of the case has been stressed into the non-linear portion of the sterr/strain curve, but not past the 2% yield offset. OTH, the brass just above the base of the case HAS been stressed beyond the yield pioint, and that portion cannot be recovered on cooling. That's the permanent stretch, and the major reason for very short case life with the gas guns. What all of this means is that a once-fired case from a gas gun does not accurately represent the chamber dimensions. It will not go back in the chamber without significant resistence. But the shooter wouldn't necessarilly be conscious of this resistence because the op rod spring is usually (but not always) enough to overcome the resistance. I f you remove the op rod spring, and try to chamber a once-fired case manually, you feel it. (I did this with my first M1A about 1983 when the Mickey Mouse cast op rid cracked!). With a bolt gun, a once fired case gives a reasonably accurate indication of the chamber dimensions, and the dimension that you measure from that case is at least a good approximation of zero headspace. With a gas gun, that once fired case is longer than the chamber ... maybe by several thousandths. So how do you determine the "zero" point for that chamber with a once-fired case? I suspect that the .003-.004 that you are bumping your cases back is actually bringing you to near the "zero" point for that chamber. What do you think?
What case gauge are using to measure your bump=back?
R/Bob
-----Original Message-----
From: Joe Sopko <[email protected]>
To: Rls1998 <[email protected]>
Sent: Sat, Dec 17, 2011 5:31 am
Subject: Re: Resizing for LR
Hi, Bob,
I was just thinking about a more fundamental issue. It's not possible to successfully only neck size brass from an M1 or M14 since the brass is ejected hot and continues to expand unconstrained after ejection. The ejected brass is often ~.005" or more larger than the chamber. It's also one reason that service rifle brass doesn't last as long as a bolt gun. All these are reasons that I'm becoming a believer in using headspace gauges with service rifles. Another story Mac told me was that he built an M1 with a tight (benchrest-type) chamber for someone many years ago. Even though Mac warned against it, that person was adamant about it and is a person that should have known better. So, Mac built it for him with a lot of caveats. The result was not good.
Joe
Another option is to call Mark Heckman who took over for Mac. He may have some better insight (Mark Heckman <[email protected]>).
Joe
44 grains of IMR4320 was the "Navy" and "Air Force" long range load under a 190 in a LC M118 match case. The loading room at the Navy unit never loaded 4895 under 190's; too fast a powder for best accuracy and functioning.
46gr H4895
Hornady 150 gr FMJ
CCI #34 primer
HXP brass
Easy on the rifle and very accurate. Camp Perry load.
The last M72 ammo loaded was ordered loaded by the DCM and was charged with 46.5 grains of IMR4895. I heard that at Camp Perry originally
LC or comparable brass, 48.0 of WW 748 or BLC2, 147-150 FMJ ball bullet.
Swage the crimp, cut the primer pockets to a uniform depth, CCI military primer, and squeeeeeeze the trigger.
======================================================================================
Don Mcoy passed away 3 days after I last spoke to him.
P.W. St.Marie
-------------------------------------------------------------------------------------------------------------------------------------------------
This was communications between my Son and two Grand Masters familiar with the rifle, at least by reputation. The other two Grand Mastered multiple times at Camp Perry. Some comments were mine.
============================================================================================================
Any Ideas on this?
This is a one of three Garands built by Don McCoy in this specific manner. The 190gr projectile is specified, and now I should be explaining what we found on our range today.
The rifle sent all 8 rounds downrange in a single trigger pull . The barrel has been hBN sealed and we're shooting 175SMKs, impact coated. Chrono shows a nominal 2,475. There's no doubt that the gas port is set to accommodate the 190s without damaging the op-rod.
This is the rifle.
This was the original explanation.
----------------------------------------------------------------
Noted Garand competition builder and accuracy specialist Don McCoy of Santee, CA, built this M1 for me in 2001. It is built on a selected Springfield receiver (1943 manufacture date), and has an Obermeyer 5R barrel with 1:10 twist. It is designed to shoot 190-grain bullets with exceptional accuracy out to 1000 yards.
This rifle has numerous custom accuracy features, including a lugged receiver, glass bedding with additional custom fabricated steel plate fittings that tie the receiver into the bedding with 3 bolts, ½-minute rear sight, reaming to ensure barrel & gas cylinder clearance as well as machining the end of the gas cylinder for stock clearance, and many more machined accuracy refinements. The forward hand grip is also glass bedded with attention taken to ensure complete clearance for the op-rod. The heavy stock is English walnut with a Fullerplast finish as only McCoy can do.
The 2-stage trigger is extraordinarily smooth and makes the rifle a joy to shoot. The rifle has approximately 40 rounds through it. It was function-fired by McCoy and later broken-in by myself using Tetra Gun followed by a dry patch every round for the first 10 rounds, every other for the next 10, and then 5 + 5 for the final 10 rounds. After the last 5 rounds it was immediately cleaned with Tetra Gun, dried, and a patch with Militec-1 lubricant was run down the bore while it was still hot. After returning from the range, the bore was cleaned with Sweets 7.62, followed by Tetra Gun. Lastly a patch of Militec-1 lubricant was run down the barrel. All cleaning & lubrication/protection was run from the breech to the muzzle.
From here on out, the rifle will clean up easily with either Tetra Gun or Kroil, followed by the Militec-1 for conditioning and as a protectant/preservative. An application of Sweets 7.62 every 200 rounds or so will help prevent copper build up. The purchaser will get the fired brass from the break-in session.
This rifle is one of only three like it that McCoy has built in his long career building match Garands. His clients include some of the top High Power competitors and collectors in the country. I have a McCoy M1 in .308 with an Obermeyer 5R 1:11 barrel, which I fired in many High Power matches with great success.
A fine, accurate, and unique rifle from one of the outstanding M1 accuracy specialists at the peak of his career.
I also have video of McCoy in his shop going over the features of this rifle which I'm sending with the rifle.
-----------------------------------------------------------------------------
By "one of three" I didn't know what he meant until the video on the rifle arrived. It was made by McCoy explaining the exact constrution of this rifle by serial number. Beside every aspect of the rifle being bedded, its triple pillar bedded. I'll post another picture of those pillars as soon as I get my sister in town to forward them our here.
So, should I be using 190's exclusively or can I simply boost the charge to obtain the right pressures?
---------------------------------------------------------------------
This was a question by a Garand competition shooter.
"The next question I have is how do you know the McCoy rifle you have was built to fire only 190 gr. bullets."
----------------------------------------------------------------------
Because McCoy made a point of it in the DVD he made for this rifle.
This is the bedding. Note the three welded pillars and the corresponding bedded receivers in the stock.
It seems that Mr. McCoy and I will be speaking today. He feels there may be a timing problem. He's very ill now and I won't be taking much of his time. With his advice I intend to solve it here. I posted this in case you gents thought of something I've missed. I was hoping to not have to bother him at all if it appeared to be something obvious to you. I suspect pressures too low may be involved, but I've never dealt with a M1 that was a custom build.
Thanks for any advice.
BTW........ Close examination of the trigger group shows a positive lock up and plenty of hammer/sear contact before release. The trigger seems to be a 4.5 pull.
Makers Medallion.
Stage one.
Stage two.
Any ideas at all? Dumb in the first place to try a 175 in lieu of a 190? Any ideas before we bother Mr. McCoy?
Latigo
CDR Xfire
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Latigo,
Mac adjusts his triggers to the absolute minimum sear engagement, with most of the weight in the first stage. I was sure that mine would double, but it doesn't. It has been very, very dependable. But mine is single lugged only at the back. (I went and dug my triple lugged rifle out of the safe a while back ... it was built be Clint Fowler, and the forward lugs are slightly different and located more forward).
These rifles are meant to be fired with the buttplate HARD into your shoulder, even in offhand where you can't use the sling. If you use a "soft" hold as in benchrest shooting, you are probably bump-firing it. The combination of the way the rifle recoils, and the trigger technique ("milking the trigger") will make it double, or even simulate full auto fire. I can do this on purpose, it gets folks attention with an M1A and ten rounds in the magazine. (if you are using your mechanical rest, you may get the same efect)
I would fire it in a good solid prone postition with a tight sling. If you want the security of a rest for ammo testing, put a sandbag under your gloved hand. If it still doubles, do the same with M72-equivalent 173 or 175 grain loads. If it still doubles, it needs some attention. The Easy Button would be a new hammer tuned for a bit more sear engagement. If all this doesn't work, then you need to talk the The Master himself. The "unkown" to me is how Mac's forward lug system may effect the way the rifle flexes under recoil forces, and how that may effect the minimum tolerable sear engagement.
Hope this helps ...
Resp'y,
Bob S.
think it does help. I was prone with the rifle bagged fore and aft. My usual way to pull the trigger on any rifle is to pull with folllow through and hold the trigger to the rear before making a conscious release............................. but considering his trigger setup, now I'm not so sure.
After doubling, I extracted the next chambered round and we noticed the primer was dimpled. I also think I remember having pulled the trigger after doubling and there was no release, just as if the hammer had not reset at all. I cycled the bolt and it fired the next chambered round ok.
Ok, so the load was with a FLS case, TTL less than manual length, primer seated just below flush, 175gr SMK seated 10 thous off the lands, 45.5gr of 4895 and a MV of 2540. I had a guy tell me about the US Army Manual data book listing the 173gr with 50gr of 4895. It sounded way wrong so I googled it and found there had been an error in TM 43-0001-27 saying that 50gr of 4895 was a match load with the 173gr projectile. I'm thinking now that I should have been at 46.5gr of 4895 anyway to make things work with the right MV and pressures. With a gas port tuned specifically for a 190, can chamber pressures that are too low cause any of this?
And the soft hold sure could have happened. I was excited about the whole thing anyway.
Don (Mac) McCoy, now in his 90's and I just spoke to him and his protoge on the phone. Too much info to type right now, but I'll be back after we implement everything he asked us to do with the rifle with full explanations.
Latigo
I was able to speak with Mr. McCoy last evening, probably for the last time. His protoge is taking over everything very soon now and I don't want to bother him again. At age 92 he doesn't need to be answering questions from someone into his first Garand. He was good enough to explain the exact nature of the rifle to me.
He said there is not a mechanical way for that rifle to double. It was all me. His exact words were, "Chamber each round with your fingers. Don't use one of those single round setups. Let the bolt close narurally. Breathe on that trigger, don't just pull it. Do all that and you'll be shooting right along with the best of them, but only if you're capable. The rifle already is. It was designed for 190s, so use 190s. The load we gave you is for military brass. Use it."
The gent taking over all of it is Mark Hendricks. He's been studying under Mr. McCoy for a long time and it now ready to keep the shop running with the same quality Garands. He's avaliable to me anytime I want to call, so I'm sure I'll have more questions later. We loaded 190 SMKs with Mr. McCoy's load data last night and we got load data from Mark for 175 SMKs as well.
I'll post targets after we take it all out to our range saturday or sunday. Its still pretty cold here so we'll be shooting from our ShootShed at the 100 yard mark. Its going to be a fun summer.
One thing I forgot. His load data is hot! A few of them with amounts over book maximums by a full grain, and one that's two grains over.
�
| Fri, Mar 15, 5:11 PM (20 hours ago) | ||
|
David, this is the C/C communication we received between J. Sopko and RL Steinberg, both of the other two multi Grand Masters. Distinguished Naval Marksman RL Steinberg is the one who proofed our new Type PS 1,000 yard Diopter at Quantico. The same one you have.
P
===========================================================
Hi Joe, (Joe Sopko)
Yup, exactly!
I cut and pasted your earlier reply on this subject and sent it to the fellow in Montana and it turns out that it wasn;t Mac that told him to neck size, it was Mark. Anyway, he is going to take your advice about bumping the shoulder back. That's exactly what I would have told him too, but I thought your advice would have more credibility than mine
I remembered the story of Dave Fiehtner blowing a Navy Mk2-1 apart with the 190 SMK load. It turns out that someone told him to seat the bullet WAY out to jam them in the lands ... and the result wasn't pretty, either ... slam fire with bolt unlocked, rifle came apart in two major pieces and a bunch of little ones. He was fortunate that he was not seriously injued.
More later .....
Bob
-----Original Message-----
From: Joe Sopko <[email protected]>
To: Rls1998 <[email protected]>
Sent: Sat, Dec 17, 2011 5:31 am
Subject: Re: Resizing for LR
Hi, Bob,
I was just thinking about a more fundamental issue. It's not possible to successfully only neck size brass from an M1 or M14 since the brass is ejected hot and continues to expand unconstrained after ejection. The ejected brass is often ~.005" or more larger than the chamber. It's also one reason that service rifle brass doesn't last as long as a bolt gun. All these are reasons that I'm becoming a believer in using headspace gauges with service rifles. Another story Mac told me was that he built an M1 with a tight (benchrest-type) chamber for someone many years ago. Even though Mac warned against it, that person was adamant about it and is a person that should have known better. So, Mac built it for him with a lot of caveats. The result was not good.
Joe
On Dec 13, 2011, at 9:18 PM, Joe Sopko wrote:
Hi, Bob,
For my 308 Win Mk2's, I full length/small base resize all my brass. I found that a headspace on Mac's rifles need to be setback a couple more thousandths than normal. I set them back about -0.003-4" from zero. I agree that neck sizing for an M1/Mk2/M14/M16 is not a good practice.
Now, I don't have any of his 30-'06 rifles, although he tried to convince me for years that it would be a better long range gun. Since that would be a different reamer, I can't say if the headspace is the same due to gunsmith technique or due to a worn reamer. I asked Mac about the characteristics of his 308 chamber a few years ago and all he told me was, "I only have one reamer for 308."
Mac was one of those masters that if he told you to do something, it usually was what you should do. However, I'd try FL SB first at zero headspace. Then, bump it back a few thousandths and see which shoot better.
Another option is to call Mark Heckman who took over for Mac. He may have some better insight (Mark Heckman <[email protected]>).
Joe
On Dec 13, 2011, at 5:19 PM, Rls1998 wrote:
What are you doing for brass prep for your MR and LR gas gun loads? Just FL? Body die to bump the shoulder back a controlled amount? Other?
TIA!
Bob S.
I've been mostly a bolt gunner since we retired, but I've thought about this particular part with the gas guns a bit. Since the case comes out HOT as you note, and continues to expand without the restraint of the chamber walls, it is larger than the chamber. As the case cools back to ambient, you recover SOME, but not all, of that expansion in the neck and shoulder area since the brass in that area of the case has been stressed into the non-linear portion of the sterr/strain curve, but not past the 2% yield offset. OTH, the brass just above the base of the case HAS been stressed beyond the yield pioint, and that portion cannot be recovered on cooling. That's the permanent stretch, and the major reason for very short case life with the gas guns. What all of this means is that a once-fired case from a gas gun does not accurately represent the chamber dimensions. It will not go back in the chamber without significant resistence. But the shooter wouldn't necessarilly be conscious of this resistence because the op rod spring is usually (but not always) enough to overcome the resistance. I f you remove the op rod spring, and try to chamber a once-fired case manually, you feel it. (I did this with my first M1A about 1983 when the Mickey Mouse cast op rid cracked!). With a bolt gun, a once fired case gives a reasonably accurate indication of the chamber dimensions, and the dimension that you measure from that case is at least a good approximation of zero headspace. With a gas gun, that once fired case is longer than the chamber ... maybe by several thousandths. So how do you determine the "zero" point for that chamber with a once-fired case? I suspect that the .003-.004 that you are bumping your cases back is actually bringing you to near the "zero" point for that chamber. What do you think?
What case gauge are using to measure your bump=back?
R/Bob
-----Original Message-----
From: Joe Sopko <[email protected]>
To: Rls1998 <[email protected]>
Sent: Sat, Dec 17, 2011 5:31 am
Subject: Re: Resizing for LR
Hi, Bob,
I was just thinking about a more fundamental issue. It's not possible to successfully only neck size brass from an M1 or M14 since the brass is ejected hot and continues to expand unconstrained after ejection. The ejected brass is often ~.005" or more larger than the chamber. It's also one reason that service rifle brass doesn't last as long as a bolt gun. All these are reasons that I'm becoming a believer in using headspace gauges with service rifles. Another story Mac told me was that he built an M1 with a tight (benchrest-type) chamber for someone many years ago. Even though Mac warned against it, that person was adamant about it and is a person that should have known better. So, Mac built it for him with a lot of caveats. The result was not good.
Joe
Another option is to call Mark Heckman who took over for Mac. He may have some better insight (Mark Heckman <[email protected]>).
Joe
44 grains of IMR4320 was the "Navy" and "Air Force" long range load under a 190 in a LC M118 match case. The loading room at the Navy unit never loaded 4895 under 190's; too fast a powder for best accuracy and functioning.
46gr H4895
Hornady 150 gr FMJ
CCI #34 primer
HXP brass
Easy on the rifle and very accurate. Camp Perry load.
The last M72 ammo loaded was ordered loaded by the DCM and was charged with 46.5 grains of IMR4895. I heard that at Camp Perry originally
LC or comparable brass, 48.0 of WW 748 or BLC2, 147-150 FMJ ball bullet.
Swage the crimp, cut the primer pockets to a uniform depth, CCI military primer, and squeeeeeeze the trigger.
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Don Mcoy passed away 3 days after I last spoke to him.
P.W. St.Marie
