handloading for gas operated semiautos

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15 years 8 months ago #1155 by Hank in Arkansas
Replied by Hank in Arkansas on topic Re:handloading for gas operated semiautos
I've been thinking about your feeding problems, and have a few more ideas. First, read through Armalite's tech notes, particularly on rifle cleaning. You might consider taking apart the bolt and carrier, and giving it a thorough cleaning and relubrication. Pay particular attention to the locking lugs and lug recess. Make sure everything is well lubed except the chamber itself. During your experimenting stage, I'd overlub it just to make sure everything is "slick". Later you can lub normally. Armalite recommends military type gun oil. I personally use Hornady OneShot spray on lub, but there's a zillion lubs out there.

Make sure as you shoot, you're testing different magazines. It's possible you have a magazine that is retarding the stripping of a round on bolt closure.

I think you're on the right track with the small base dies. You mentioned that your reload neck dimensions weren't the same as factory. Crimping can really screw up things. A taper crimp that is too strongly applied can cause the neck to bulge out. I've seen it so bad that the bulge was visible, and the bullet could be twirled by hand in the case, being held in place only by the crimp. I've switched to only using the Lee Factory Crimp die, because it completely avoids this problem. Good news, too -- the Lee die is inexpensive. The die squeezes the neck only from the sides, not in and down toward the shoulder.

AR rifles need loads that are fairly near maximum to function properly. I wonder if some of your loads are failing to push the bolt & carrier fully to the rear upon firing? Maybe enough to extract the fired round and strip off the next one, but without enough spring pressure to fully feed? Only you know if it's your starting loads that are failing to feed fully, or the hotter ones.

I gather that your rounds aren't really sticking in the chamber, but rather the bolt isn't closing fully. Early on with my AR10, I had similar problems, but no longer. All decent factory ammo is feeding fine, and my carefully prepared handloads are as well. Keep us posted.

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15 years 8 months ago #1156 by Hillbilly1053
Replied by Hillbilly1053 on topic Re:handloading for gas operated semiautos
Thanks for your comments Hank. I am good on the cleaning and lubrication. I am sure of it.

And I am also sure I am getting enough pressure to cycle fully.

For clarification, I do get rounds that are 'stuck' in the chamber. Not horribly stuck, just expanded enough to be tough to extract with the charging handle. These rounds also fail to have a dimple on their primer, indicating maybe I went TOO FAR in the chamber...? (Sized too small...)

I do have a technical question about a point you mentioned. Chamber pressure. The NATO 7.62 is supposed to max out at 50000 psi and the 308WIN at 62000psi. How do you measure pressures? Since the reloading data does not distinguish between NATO and WIN, and does not tell expected pressures...how do you know?

Thanks...

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15 years 8 months ago #1159 by Hank in Arkansas
Replied by Hank in Arkansas on topic Re:handloading for gas operated semiautos
First, on not seeing a primer strike. That's because the round did not fully chamber, so the bolt did not lock up fully. ARs have a safety device built into the bolt that keeps the striker from hitting the primer UNLESS the bolt is fully locked up. That avoids a disasterous situation that would wreck the rifle and maybe the shooter. Normal reloading dies, even Small Base, cannot set back the shoulder of the case far enough to keep the primer from being struck. You should be able to run the die into the press all the way to full contact with the shell holder, and still not set back the shoulder too far. The small base die will simply reduce the diameter of the cartridge more than a regular die. I know bolt action shooters experiment with neck sizing and partial sizing, but for ARs I'd recommend full sizing -- that is, run the die down fully onto the shell holder. You should not get excessive headspace. Maximum, maybe, but not excessive. Be aware though that cases will NOT last as long as if they were fired in a bolt action. If, after one or two firings, you see signs of head separation, then something may be wrong with either the die or the chamber, but that's going to be very rare. But don't expect more than 3 or 4 safe reloads of your AR brass. (The Sierra manual, edition V, has an excellent article to explain why.)

There is no easy way for a hobby reloader to measure pressure. The equipment is too expensive. Oehler (spelling?) makes a device, but it's beyond what most hobbyists will undertake. The other equipment is expensive lab stuff. You simply have to stick with reliable published reloading data that has been pressure tested for you. If you have a chronograph, it can give you pressure clues. For example, if a factory load chronographs at 2700 fps, think of that as a baseline. Then if you test a handload with the same bullet weight, and you are getting 3000 fps, something is wrong. You won't know the actual pressure, but it's a good bet that you're way over what the factory load was producing. Likewise, if you get only 2400 fps, your load is probably mild. However, even so, if that load is what the load manual says is MAX, then that's max. SAMMI, NATO, Europeon CIP, and other groups, all publish pressure specs, but often using different methods. The handloader has no choice but to use reliable tested loads. In terms of dimensions, I believe .308Win and 7.62x51mm are identical; that's NOT the case with .223 vs 5.56mm. (I'm talking chambers, not ammo.)

You may have read about using a micrometer to measure case head expansion to estimate pressures. I've done it, and read a lot about it. I've come to the conclusion that it's sort of like trying to estimate your car's tire pressure by measuring the outside dimensions of the tire. It's just not reliable; too many variables.

I'm beginning to suspect that something is happening in the crimping step to mess up some of your rounds. Are you trimming to uniform length? Also, try the "maximum" resizing with the SB dies, that is, get a firm bump of the die onto the shell holder. Try a few dummy rounds. And get that Lee Factory Crimp die. I also recommend the Wilson Case Gauge in .308. It's nothing but a properly dimensioned "chamber" and very easy and fast to use. Hope all this helps.

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15 years 8 months ago - 15 years 8 months ago #1164 by bigwheel
Replied by bigwheel on topic Re:handloading for gas operated semiautos
Get a case gauge. I like the lyman as it lets you check headspace and neck length
loaded or unloaded. Small base dies are not necessary. They are a .001 or so smaller
at the base is all. You may be bulging the neck and or shoulder if you are crimping non canallured bullets with your full length die. They usually are a roll crimp on bottle neck
cartridges if not always and if the crimp starts before the bullet is seated all the way
it forces the brass down. Also and as common is the expander ball is pulling the shoulder
back out some on the softer cases. Leave it out when you size whenever possible or if
you insist, run the cases back through the die a second time with the whole spindle assembly removed. A case gauge is the quickest and easiest way to avoid problems at the
range.
As for sticking rounds, sounds like a pressure problem. An undersized case, too much
powder, etc... Remember a lot is going on in a gas gun and it all has to be timed right.
As the powder is ignited the shell expands and grips the chamber, the primer blows back
against the bolt face, the case then stretches backward and reseats the primer: as the
bullet passes the gas port is sends pressure to the bolt carrier. This pressure pushes the
bolt forward and takes the friction off the locking lugs. About this time the case has shrunk and will allow the bolt to rotate and extract the case as it travels reward. This is
all part of "timing". If you see a shinny spot on the head of the case it is called "bolt swipe". There was pressure still on the case as the bolt started to rotate. The next level
of a problem is heavy extractor marks on the case and finally actually deforming and tearing of the rim by the extractor. These are all signs of a problem that will take the
life out of you brass and your gun. And they can be dangerous. New factory brass is
pretty safe but when reloading the brass has already been weakened some so things
are more critical.
You mentioned cases that were unfired not extracting, could be the bullet touched the lands which leaves marks on the bullet, also can be the rim of the case is deformed
from a previous firing and without a case gauge you have no easy way of seeing it. A
few seconds with a file is all it takes to cure them if they are. Anything that holds the
bolt from closing is a life threatening danger so pay special attention to it being closed
all the way. I have seen posts of ar15 bolts blowing apart from not having rotated all the way closed. With new cases, bullet seating coal and crimping should be the only things that could cause the bolt not to close.
As for the hornady one shot user, it's a case lube, not gun grease or oil. Am I missing
something in the post? A note on the lee fcd if you use one: they crimp non-canallured
bullets fine but use a very light crimp as they deform the bullet very easily.
Lastly : 7.62x51 nato loads are different than 308, hornady, speer and sierra designate them in their manuals.
Hope this helps a little more.
Last edit: 15 years 8 months ago by bigwheel.

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15 years 8 months ago #1166 by Hank in Arkansas
Replied by Hank in Arkansas on topic Re:handloading for gas operated semiautos
Two more comments on this thread. I do use Hornady OneShot "Gun Cleaner & Dry Lube", marketed specifically for lubricating firearms; it comes in a black can. Hornady also markets a product called OneShot "Case Lub", in a red can. They are completely different products.

There's endless discussion in gun mag articles and reloading manuals on the difference between 5.56mm vs .223Rem, and 7.62 vs .308Win. The SAMMI (Sporting Arms and Ammo Manufacturers Institute) standard published case dimensions are identical for each, that is 5.56 is the same as .223 and 7.62 is the same as .308. So far as I can tell, most manufacturers of rifles cut .308 chambers the same as 7.62 chambers. That is not always the case with .223. SAMMI issued a warning a few years back that some commercial rifles chambered in .223Rem produce excessive pressure when used with 5.56mm military ammunition. That is due to the fact that some manufacturers produce .223 rifle chambers that differ significantly in dimension from military 5.56 chambers. SAMMI went on to recommend that only commercial .223Rem ammo be used in commercial rifles, and not to use any 5.56 military ammo in them. They went on to say that shooters should check with their rifle's manufacturer to find out if military ammo was OK. Ruger's Mini14 and all normal AR type rifles are cut with military dimensioned reemers, but there are all sorts of custom built match rifles and even normal production sporters out there that may not be. As for commercial civilian rifles, I have a Remington 700BDL varmint rifle in .223Rem that definitely does show excessive pressure when milspec 5.56mm ammo is fired in it. I did it once, but won't again. I don't know how Remington is dimensioning current production rifles, but when my rifle what made, they specifically recommended using only Remington commercial ammo.

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15 years 8 months ago #1168 by bigwheel
Replied by bigwheel on topic Re:handloading for gas operated semiautos
Thanks for clearing up the one shot, never have seen the gun lube. The case dimensions are the same for 308 and 7.62 but as previously stated the pressure specs
are different. And as some loads in barrels 20" inches and longer see secondary pressure
spikes sometimes doubling the posted pressure it is imperative to stay with gas gun loads.
When you send a load into a lab they won't even record the secondary spike unless you
specifically ask them to. Many manufactures loads have these same spikes as well and
they don't advertise the fact. In bolt buns it is not a huge factor. In a gas gun the timing
is involved.

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14 years 5 months ago #4268 by Louisiana Shooter
Replied by Louisiana Shooter on topic Re:handloading for gas operated semiautos
I am an NRA Training counselor. If there is a substantial safety factor covered in Sierra's 5th edition that is not covered in other manuals, the NRA Training Department would be an effective partner in helping to get the word out. I read the artical in Western Shooter, and while there is lots of great information there that cannot be talked about too much, all of it is covered in every reloading manual that I have read. I do not have, and cannot find, Seirra's 5th Edition.

Gun writers, even technical gun writers, know that excitement is what sells, so before calling in the Marines to spread the word, some tests should be done by impartial parties. Can someone who has read Seirra's 5th edition narrow the concerns down to 3-5 key issues. This summer, I will be with a few other TC's and several Instructors at a Boy Scout Camp. We will have plenty of "down time". With hundreds of years of collective experience, we can devise and conduct some field tests to try to see what level of attention should be given these concerns when NRA courses are conducted.

My brother and his wife founded and operate the Ballistics Testig Group, presently teach at The Air Force Academy, and are NRA Instructors as well. If pressure testing has to be done, we can make that happen.

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14 years 5 months ago #4269 by Hank in Arkansas
Replied by Hank in Arkansas on topic Re:handloading for gas operated semiautos
Louisiana Shooter, I'll try to summarize, although it's hard to do so for nearly 20 pages from Sierra. First, there's discussion about slam fires, usually due to faulty handloads combined with the free floating firing pins found in military rifles. Next, there's discussion of "out of battery" fires. This can be due to worn parts, cobbled together "custom" rifles, and shooter error. For example, I recently watched Lee Ermy (?), aka Gunny, on TV carefully sliding home the op rod handle on an old M1 as if he was loading eggs. Sierra discusses proper rifle manipulation (which Gunny wasn't doing), which is all the more important with handloads that are often more difficult to chamber. Next, there are pages devoted to component and powder selection for gas guns. There's lots of info on primers, soft versus hard, and the CCI arsenal primers. There's also lots of info on bullet seating, proper neck tension and crimping. Finally, there's discussion of gaging (ie, using a gage to check rounds).

I'm an NRA reloading instructor and have about 40+ years at it. However, there are tens of thousands of new guys just getting into ARs, M1s, and M1As, and then starting to reload. I found the Sierra chapter very informative, and still think it's a "must read" for anyone who can find it. Also, A-Square's "Any Shot You Want" loading manual is also excellent. I think it's very important for handloaders to realize that military style gas operated autos are a different animal from bolt guns. The internet has at least revealed that there are many more blown up ARs than we would have ever thought. I'd be glad to discuss any of this with you. Send me a private message if you wish.

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14 years 5 months ago #4270 by Louisiana Shooter
Replied by Louisiana Shooter on topic Re:handloading for gas operated semiautos
I cousel instructors that I train to be very careful about not showing brand likes/dislikes. That said, reviewing the information that I have so far and sifting it through my training and experience, it would seem that people loading for semi-auto's should use a subset of the load data out there. Did the Sierra manual have charts with load recipes and dimensional specs proven to work more safely and reliably in semi's? It seems to me that given the fact that many great load recipes are not so great in semi-auto's, having a separate chart for semi-suto proven data in the manual would be a step in the right direction. NRA Instructors and training dept publications could simply coach reloaders with semi's to seek out semi-auto specific data.

Several issues mentioned are really either rifle maintanence issues or attention to detail related. I believe that these are properly address in the NRA training programs, but should be reflected in pages on .223 and .308 loading, too. Having the issues stressed every time a loader looks up data could help.

We'll have some fun at camp making cartridges of varying specs and components to see what parameters we can identify. I already have a bunch of cartridges with the Federal primers one writer says to avoid.

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14 years 5 months ago #4271 by bigwheel
Replied by bigwheel on topic Re:handloading for gas operated semiautos
Primers are not harder or softer , they have thicker or thinner cups. Here's a chart of the most
popular.

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