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Thread: Gas gun reloading

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    Gas gun reloading

    So I finally purchased a POF P308 and I need to start load development. I've been reloading for years but only for bolt guns. I know to FL resize but that's about it. Is there any other things I need to know that might be different? I'm going to start with Winchester brass and save my Lapua's for the bolt gun. Is there any advantage to turning the necks with a gas gun?

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    Basically, it's the same. Use a case gage and full length size by .003-.005" instead of the .001-.002" you use for bolt guns. I don't think turning necks for a gas gun is worth it. The chambers are usually too loose to take advantage of it, and they tend to beat the crap out of the brass anyhow, so it winds up being a lot of work for negligible gain. Leave the neck turning for bolt guns.

    Other than that, some like to use the military style primers like the CCI 41 in gasguns with floating firing pins like the AR. (CCI 34 for large primers - 41's are the small ones)
    bigedp51 and McSweep like this.
    http://bisonballistics.com - articles about precision shooting and an online ballistic calculator.

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    Reload the same as if you were reloading for a bolt gun. The only things you need to consider are:

    A) crimp your rounds. The lee factory crimp is ideal but do not overcrimp. This will prevent bullet offset as autoloaders can be violent chambering.
    Even w/o a canelure you can put a minute crimp. Crimp helps in two ways, it helps with preventing bullet offset but also it is a good way to
    provide consistent starting pressure that translates into nice speed spreads. Be careful w/o a canelure is ok but very lightly w/o deforming the bullet.

    B) Some suggest to use the small dies. These full size to a slighter smaller dimension to assist with autoloaders. So far I have not seen any need
    to do that even with some rounds being just necked sized. But they are rounds from the same gun. If you are given brass or buy brass new or
    once fired or from the recycling bin always full size and trim to spec or you will find surprises.

    I hope this helps.

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    I disagree on the crimp. Crimping a match grade bullet is not a good idea. You don't need to do it.
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    http://bisonballistics.com - articles about precision shooting and an online ballistic calculator.

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    So the things I've learned while loading for a semi auto rifle. Crimping is over is over rated and I don't do it for precision rounds. I do FL resize every firing. Other then that I follow the same procedure as I would for any other rifle.
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    Quote Originally Posted by demoniacal View Post
    Basically, it's the same. Use a case gage and full length size by .003-.005" instead of the .001-.002" you use for bolt guns. I don't think turning necks for a gas gun is worth it. The chambers are usually too loose to take advantage of it, and they tend to beat the crap out of the brass anyhow, so it winds up being a lot of work for negligible gain. Leave the neck turning for bolt guns.

    Other than that, some like to use the military style primers like the CCI 41 in gasguns with floating firing pins like the AR. (CCI 34 for large primers - 41's are the small ones)
    Helidriver, demoniacal is spot on in his answer and I could not say it any better,(two thumbs up) and as he stated the only difference is shoulder bump and selection of primers.

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    I agree 110%

    Crimping may not be needed but if done correctly with the Lee FCD accuracy is as good if not better with extra insurance of the bullet not moving.
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    Great thanks guys.

    I was planning on running a tighter neck tension to avoid crimping (I don't know how to crimp). Someone suggested .003 neck tension. I use Redding neck only and FL dies. Both bushing type with the buttons removed. My normal process when I FL size is neck only die down .004 then FL die down the final .004. That usually gives me .001 neck tension depending on the brass. I figue I will stick with the same process and just adjust the bushings to end up with .003.

    Yes, no maybe?

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    There is only so tight you can get a neck. If you use a really small bushing, you'll just deform the neck until the bullet fits, and then you'll have the normal amount of neck tension, which is provided by the spring of the brass. It's not quite an exact science, but as long as you don't use really light neck tension, you should be fine. .002 is what I've used without issue. I don't stress about it.

    To crimp, you need a separate crimp die. They're best left for tube magazines and heavy stuff. Precision rifles really don't need it.
    http://bisonballistics.com - articles about precision shooting and an online ballistic calculator.

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    As I said a very light crimp assures two objectives. Bullet setback/movement preventions and consistent starting pressure that is a key factor of accuracy sometimes showing single digits differences in the spreads.
    What one needs to do is to put a minute amount of pressure so there is zero bullet/jacket deformation. I have been using a collet for 25+ years and never had any problems. Quite the opposite, the same reloads show
    sub moa consistency all the time.
    For bolt action I might not crimp depending on the jacket and load.

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    Quote Originally Posted by damoncali View Post
    I disagree on the crimp. Crimping a match grade bullet is not a good idea. You don't need to do it.
    +1. I never crimp and get excellent results with 155's and 168's.
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    Quote Originally Posted by Thumper580 View Post
    +1. I never crimp and get excellent results with 155's and 168's.
    I have a bunch of 175s for my bolt gun. Do the lighter weights work better for gas guns? I assume a 1 in 10 twist should be plenty for the 175s.
    Last edited by Helidriver; 10-31-2013 at 08:21 AM.

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    I shoot 175s and 178s through my 1-11.25 with good results, it is common. I believe the 1-10 is capable up into the 220s. Correct me if I'm wrong.

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    What about charge weight? I would think that a semi would be much more sensitive to bore time and pressure? What say the gas-gun-gurus?
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    If timing is an issue then the answer is an adjustable gas system not charge weight.

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    No need to crimp, just use a smaller bushing to achieve .003 neck tension. .003 has not deformed the neck for me. 175's work good and you may also try 155 scenars to see if your rifle likes them.
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    You will need to reinsert the button because gas guns throw brass into the things that bends the necks and they have to be returned to round. After that you should just decrease your bushing to increase neck tension to .003 or .004, that is why they make bushing dies so you can adjust it how you like. There is no need to add a unneeded step.
    Not all gas guns come with or are allowed by rules to have a adjustable gas block so you might have to decrease charge weight or go to a faster powder to decrease port pressure. The powders used in bolt guns and not necessarily the best powders for semi autos.

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    Quote Originally Posted by Xcount View Post
    You will need to reinsert the button because gas guns throw brass into the things that bends the necks and they have to be returned to round. After that you should just decrease your bushing to increase neck tension to .003 or .004, that is why they make bushing dies so you can adjust it how you like. There is no need to add a unneeded step.
    Not all gas guns come with or are allowed by rules to have a adjustable gas block so you might have to decrease charge weight or go to a faster powder to decrease port pressure. The powders used in bolt guns and not necessarily the best powders for semi autos.
    How do you set neck tension with the button installed? As the cartridge is extracted from the die doesn't the button size it to it's final dimentions? I could be wrong and need to measure my buttons but that's what I thought the purpose of the button was.

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    Your sizing process is confusing for me. Are you running them through a neck size and then a body die or an FL die? Doesn't make sense.

    What I do is run them through an FL small base die with the expander ball turned down a little bit so there is about .002-.003 neck tension. Brass I trim to 2" even, CCI or Fed primers, and then any of your typical favorite powders for a 308. 3031, 4064, 4895, Varget, Reloader 15 H4895 they all run great. Seat 175smk to 2.81" overall so they fit in the mag and go to town. I've made like 4000+ 308 loads for nothing but gas guns these past few years and have had zero problems and my ammo always shoots "good enough".

    As far as pressures go with gas guns lots of times you have a bit tighter chamber than a big roomy remington so your charges might be lower at max. But you will still get to the "favorite" loads a lot of people use.

    IMHO no need to complicate something that isn't that complicated.

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    I use a Lee FCD for my match loads for my AR-10 and they shoot the lights out! Factory match ammo has a crimp and is accurate. I will also crimp match loads for a semi. I have played with it for my bolt guns bur its not really needed.

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    Quote Originally Posted by BCP View Post
    Your sizing process is confusing for me. Are you running them through a neck size and then a body die or an FL die? Doesn't make sense.

    What I do is run them through an FL small base die with the expander ball turned down a little bit so there is about .002-.003 neck tension. Brass I trim to 2" even, CCI or Fed primers, and then any of your typical favorite powders for a 308. 3031, 4064, 4895, Varget, Reloader 15 H4895 they all run great. Seat 175smk to 2.81" overall so they fit in the mag and go to town. I've made like 4000+ 308 loads for nothing but gas guns these past few years and have had zero problems and my ammo always shoots "good enough".

    As far as pressures go with gas guns lots of times you have a bit tighter chamber than a big roomy remington so your charges might be lower at max. But you will still get to the "favorite" loads a lot of people use.

    IMHO no need to complicate something that isn't that complicated.
    Yes, neck size down with a bushing half way to final size then FL size to the final neck tension. Both are bushing dies. It helps with case neck concentricty by not going more than .005 down at a time. I thought it was a load of bull until I actually tried it. I figured why not try it since I already have the dies. My necks are truly more concentric. Does it make a difference in accuracy? I don't really know but I like to do it because of what I see on the runout gauge.

    The Rifleman's Journal: Reloading: Two-Step Sizing and Concentricity

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    Just wondering if your sizing process is getting the case up high enough into the FL die with a bit of shoulder bump so they run 100%. That was my main thought when I read your post. When you make some test loads you will find out if they run well or not.

    FWIW mine usually run 1-1.5ish on neck and 3-6 total for bullet runout using pulled 175 sierras and FC brass. With LC there is a little less bullet runout, and a bit more less with winchester brass. Most of these go through my M1A so accuracy is hard to judge but generally seems to shoot about like M118LR which was what I was trying to dupe. For me reloading is not a passion but a necessity so lots of 'good enough' ammo is preferable to a small batch of 'excellent'.

    When I had my DPMS SASS I made ammo the same way but using winchester brass and 178 amaxs or BTHP and it shot about 3/4-1MOA, so really no different than the best I could do with fed match.
    Last edited by BCP; 10-31-2013 at 09:29 PM.

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    Quote Originally Posted by BCP View Post
    Just wondering if your sizing process is getting the case up high enough into the FL die with a bit of shoulder bump so they run 100%. That was my main thought when I read your post. When you make some test loads you will find out if they run well or not.

    FWIW mine usually run 1-1.5ish on neck and 3-6 total for bullet runout using pulled 175 sierras and FC brass. With LC there is a little less bullet runout, and a bit more less with winchester brass. Most of these go through my M1A so accuracy is hard to judge but generally seems to shoot about like M118LR which was what I was trying to dupe. For me reloading is not a passion but a necessity so lots of 'good enough' ammo is preferable to a small batch of 'excellent'.

    When I had my DPMS SASS I made ammo the same way but using winchester brass and 178 amaxs or BTHP and it shot about 3/4-1MOA, so really no different than the best I could do with fed match.
    Yeah. it might be a needless step. Since I've never loaded for gas it will be a learning process. I have 2 boxes of 178 Amaxs that I might try with this. I need to venture out from my Lapua/Varget/SMK pet load.

    What's your take on the military CCI primers? Do we really need them? I've got a bunch of 210Ms that I would prefer to use.

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    Helidriver

    One word of warning, on over gassed rifles there can still be pressure in the barrel as the bolt is moving to the rear. As the bolt moves to the rear this pressure can cause the shoulder of the case to move forward. Therefore it is possible for the fired case to be slightly longer than the chamber and give you a false reading when adjusting for shoulder bump and resizing your cases. This case "growth" varies with brass hardness and annealing and if your going for minimum shoulder bump you will see varying springback rates after sizing and you should know the actual headspace length of your chamber.

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    Quote Originally Posted by bigedp51 View Post
    Helidriver

    One word of warning, on over gassed rifles there can still be pressure in the barrel as the bolt is moving to the rear. As the bolt moves to the rear this pressure can cause the shoulder of the case to move forward. Therefore it is possible for the fired case to be slightly longer than the chamber and give you a false reading when adjusting for shoulder bump and resizing your cases. This case "growth" varies with brass hardness and annealing and if your going for minimum shoulder bump you will see varying springback rates after sizing and you should know the actual headspace length of your chamber.
    Is there a good indication of when this is occuring? What do I watch for?

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    I don't see a need for the CCI 34s. Fed 210M is a good primer I'd use them all day long.

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    Quote Originally Posted by BCP View Post
    I don't see a need for the CCI 34s. Fed 210M is a good primer I'd use them all day long.
    Good deal. I figured but wanted to make sure.

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    Quote Originally Posted by Helidriver View Post
    Is there a good indication of when this is occuring? What do I watch for?
    Fire your rifle with the gas system turned off in the bolt action mode and then in normal mode with the same ammunition and see if the cartridge headspace length is longer in "normal" mode. Changes in components especially powders will effect port pressure in the normal mode and could effect fired case length.

    The Hornady Cartridge Case Headspace Gauge will give you very good case length readings for measuring fired cases to adjust for shoulder bump.


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    Whomever believes loading for bolt is same as gas is mistaken. Sizing cases without an expander is common practice for many bolt gun loaders. As xcount wrote, because semis ding the case mouth often, your expander button or mandrel will need to straighten out the inwardly poking ding.

    Also, semis will not tolerate chamber pressure the same as a bolt gun. I refer primarily to the large chassis AR's like yours, rather than AR15's. Breaking cam pins, excessive / premature lug wear or even breaks, primer piercing, broken firing pins can occur in AR's when pressures rise to excessively high levels.

    In other words, put too much propellant in a round and fire it in your AR10/Lr308, and do it enough times, parts will break. An AR clearly is not a bolt gun and is not intended to be used like one. For AR10/Lr308 rifles and carbines, use data proven to be safe in the M14 (H 4895, 155 - 168 grain bullets, 40.0 - 42.0 grains propellant). Otherwise, firing your semi-automatic rifle or carbine using bolt gun ammo and off-the-shelf hunting ammunition will be at your risk and peril, either bodily, or mechanically. At least wear eye protection.

    By the way; run an expander mandrel instead of a button, but if you insist on the button, polish it, and expand the case mouth using a down stroke of the press handle. Expanding while moving into the case mouth, like coitus, works better than expanding while pulling the button out of the case mouth. The latter can stretch the mouth out of concentricity or affect bullet runout. Last, crimping might not hurt anything, depending on whether the crimped ammo shoots well, but if crimping is necessary to prevent coal changes, or runout, the ammo is not the cause. The cause for that is feed ramp issues directly, or indirectly by maladjusted magazine lips not presenting the round sufficient to facilitate proper feeding. Canelured bullets are designed for optional crimping if proven necessary.

    Now do as you wish, but you have been warned.

    Last edited by Casey Simpson; 10-31-2013 at 11:39 PM.


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    Most gas guns have a floating firing pin that kisses the primer when a round is chambered. The cci primer has a thicker cup to alleviate this issue. Fed primers have a very sensitive cup that has been known to cause slam fires during chambering. Many years ago I had a couple slam fires with fed primers due to primers being seated flush and being hit by the firing pin. After that I bought a primer pocket uniformed and made sure primers were seated below flush. Never had an issue after that

    Make sure to clean up/uniform the primer pocket and seat the primers well below flush.

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    Quote Originally Posted by Casey Simpson View Post

    Expanding while moving into the case mouth, like coitus, works better than expanding while pulling the button out of the case mouth.

    Best use of 'coitus' EVER! My reloading bench will never feel the same.
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    Quote Originally Posted by bigedp51 View Post
    Fire your rifle with the gas system turned off in the bolt action mode and then in normal mode with the same ammunition and see if the cartridge headspace length is longer in "normal" mode. Changes in components especially powders will effect port pressure in the normal mode and could effect fired case length.

    The Hornady Cartridge Case Headspace Gauge will give you very good case length readings for measuring fired cases to adjust for shoulder bump.

    I have the guage already and my rifle has the adjustable gas block. Seems simple enough.
    Last edited by Helidriver; 11-01-2013 at 08:47 AM.

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    I have only been reloading for 5 years so take this at newbie value. once fired LC brass, cci 250 LRM primer behind Varget, RL 15 and IMR 4320 pushing 168 & 175 SMK's
    I crimp everyone with the Lee factory crimp die. They shoot very well at 100yds out of a RRA 308 w a 24"bbl. Crimping made for better groups for me.
    The nosler 168 BT shoots extremely well out of this gun with varget, my hunting load. Have no idea of velocity just worked up loads from the book till they shot acceptable.

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    Quote Originally Posted by damoncali View Post
    I disagree on the crimp. Crimping a match grade bullet is not a good idea. You don't need to do it.
    I agree. Only crimp if the bullet has a cannelure. Crimping a bullet without one will compress not just the jacket but the soft lead beneath it. When the round is sent downrange the jacket will expand, the lead won't, leaving a void that can put the bullet totally out of balance. Not something that helps when the bullet is spinning many, many thousands of revolutions per minute. A simple example is a 1:12 twist with a 3,000 fps muzzle velocity. One rotation of the bullet for each foot traveled so that means 3,000 Rev's per Second. Just a paltry 180,000 RPM and at that speed ANY bullet imperfection is a lot of force trying to make it wobble.
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    Quote Originally Posted by Helidriver View Post

    What's your take on the military CCI primers? Do we really need them? I've got a bunch of 210Ms that I would prefer to use.
    I've used thousands of Federals without slam fires. But it only takes one to ruin a match or worse, so I recently switched to the CCI's. There's no reason not to. Proper safety is key here - be goddamn careful when you drop the bolt. Don't put a round in the chamber and then drop the bolt on it - always feed from a mag or use a proper single load follower. Be doubly careful if you're using normal primers.
    http://bisonballistics.com - articles about precision shooting and an online ballistic calculator.

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    Quote Originally Posted by Helidriver View Post
    Yeah. it might be a needless step. Since I've never loaded for gas it will be a learning process. I have 2 boxes of 178 Amaxs that I might try with this. I need to venture out from my Lapua/Varget/SMK pet load.

    What's your take on the military CCI primers? Do we really need them? I've got a bunch of 210Ms that I would prefer to use.
    Quote Originally Posted by damoncali View Post
    I've used thousands of Federals without slam fires. But it only takes one to ruin a match or worse, so I recently switched to the CCI's. There's no reason not to. Proper safety is key here - be goddamn careful when you drop the bolt. Don't put a round in the chamber and then drop the bolt on it - always feed from a mag or use a proper single load follower. Be doubly careful if you're using normal primers.
    I've used a lot (many thousands) of standard SRP's without slamfire incident but over the years have become very fond of the Wolf/Tula .223 Primer. Supposed to be the "slam fire preventer" that he CCI's are but when I bought my last case of 5,000 they were less than half the price. Performance and accuracy didn't suffer at all. They were also more plentiful than the CCI's which certainly helped a lot too.
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    I would suggest using CCI BR-2 or the standard CCI Large Rifle Primer.They have a thicker / harder cup that add a factor of safety with a free floating firing pin.I use the federal 210M in my bolt gun.It only takes one incident to cause you a bad day.Like others have said the wolf primers will work well in a gas gun.
    I have shot the M1-A for over twenty years in competition .I have seen several slam fires with Federal 210M's .

    Regards,Mike

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    One more thing worth noting - the CCI military style primers are considered magnum primers and according to CCI, are "optimized for ball powder". I don't know exactly that that means, but they are not interchangeable with regular CCI primers.
    http://bisonballistics.com - articles about precision shooting and an online ballistic calculator.

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    From what I have read, the CCI #41 SR Mil primer is pretty much the same as the CCI #450 SR Magnum primer. Except the #41 has a few thousandths more space between the anvil and the cup.

    Same priming compound, same amount of priming compound, and same cup.

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    Quote Originally Posted by Pinecone View Post
    From what I have read, the CCI #41 SR Mil primer is pretty much the same as the CCI #450 SR Magnum primer. Except the #41 has a few thousandths more space between the anvil and the cup.

    Same priming compound, same amount of priming compound, and same cup.
    All the conversations about which primer is which and their construction/content reminds me of an incident back in the very early 1970's. I was working for an Oil company and visiting one of the dealers I oversaw. He was getting a delivery of batteries from a local outlet. The salesman went out to the truck, pulled several batteries out that were exactly the same only had no labels. He then pulled out a folder, selected some stick on labels, and applied them. He now had three different battery "Models" with different warranties. The batteries were exactly the same, just the labels changed, along with the prices for each.

    Makes me wonder how many primers are merely different due to price and packaging, nothing else.
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    Quote Originally Posted by Deadshot2 View Post

    Makes me wonder how many primers are merely different due to price and packaging, nothing else.
    Cup thickness, cup hardness and anvil height effect primer sensitivity, more slam fires occur when chambering a single round "WITHOUT" the magazine in place. This is because when feeding from the magazine bolt velocity is greatly reduced and inertia on the free floating firing pin is much less. Slam fires on feeding from the magazine normally happen because of a high primer. NOTE: as stated above CCI milspec primers have a shorter anvil that reduces primer sensitivity even more and both are magnum primers. Military ball powders are double base powders and use more deterrent coating to control the burn rate and keep peak flame temp down. The magnum type primers also insure proper ignition of the powder in below freezing temps.

    Below, small rifle primers used in the AR15 should have a cup thickness of .025 to help prevent slam fires. Large rifle primers all have the same cup thickness and seating depth is very important.



    Below, military ammunition has a milspec requirment that the primer be .008 below the base of the case. (center left in photo)



    Now click on the links below and look at the flash photos of the primers going off and "SEE" the difference in primers. Look at the flame size on the Remington primers, Remington ran Lake City Army Ammunition Plant from 1941 to 2001 and loaded ball powders in this ammunition and did not use CCI No.34 or 41 primers.

    Primers - Large Rifle Primer Study
    A Match Primer Study in the 30-06 Cartridge
    By Germán A. Salazar

    The Rifleman's Journal: Primers - Large Rifle Primer Study

    Primers - Small Rifle Primer Study
    A Match Primer Study in the 6BR Cartridge
    By Germán A. Salazar

    The Rifleman's Journal: Primers - Small Rifle Primer Study
    Last edited by bigedp51; 11-03-2013 at 10:23 AM.

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    On the M1 Garand and the location of the gas port the bullet is out of the barrel before the bolt begins to move. On the M1A and AR15 rifles with the location of the gas port and being over gassed a fired case can end up longer than the chamber. If using thinner commercial cases the shoulder moving forward can be greater when fired.

    If these cases are not sized properly the head clearance or air space between the bolt face and the rear of the case could be zero or less than zero. Meaning the case is as long as the chamber or even longer, this increases the chance of a slam fire.

    On a semi-auto rifle you need more head clearance to insure proper chambering. Below is a animated image of a case firing, uncrimped primer movment and head clearance.



    Below, primers should be seated with a slight primer crush to ensure the anvil is seated properly. (drawing is exaggerated)