Nitrider

Your longer guide rod theory makes sense. Also, I've noticed that the Gen 5s are tighter when locking up. In my experience when coupled with a lighter recoil spring they're a little more likely to hang out of battery than Gen 1-4s.

I run a new Steel Challenge club and have been generously given some "hand-me-down" plates to start with. They are great (for now), but I want to upgrade them as soon as possible. Who makes the best Steel Challenge kit right now? Features I care about in no particular order: -Price -Ease of transport -Best "ringing" steel -Safest design (to minimize spalling) -Most durable

Rowdyb- I am glad that I am not the only person who dislikes the unserrated and beveled areathat Dawson is putting on their rear sights. I get a huge "bloom" effect in certain lighting conditions when using them. This makes vertical alignment of the sights extremely difficult and horizontal alignment a bit harder than usual. Right now the only two MOS compatible sight available (that I'm aware of) are the Dawsons (crappy rear) and the Proctor Y notch (which I dislike too). I tried calling Dawson and they seemed nice but couldn't even understand my displeasure with their rear sight. I contacted Proctor and he is no longer making non-Y notch sights. I have two sets of the old non-Y notch pre-MOS sights and LOVE THEM. I wish he'd step up and make something decent! Are you still liking your Sevignys?

Bringing a post WAYYY back from the dead... I've used the Magloc +2oz base pads with really good success. They've outlasted other brands through tons of drops on polished concrete. Usually the base pad doesn't fail, but the plastic at the base of the mag does.

I can't say that I've gotten to the bottom of this issue, but I seem to have tamed it for now. I slightly increased the recoil spring weight so that my rifle doesn't beat itself up when shooting XM193 and still runs darn near everything else under the sun flawlessly. Keep in mind that my definition of a rifle that beats itself up is probably another guy's definition of acceptably gassed. When I feel the recoil spring bottoming out, see the red dot vibrate violently under recoil, and see 2 o'clock ejection... I call it over-gassed. I really think the best solution would be the addition of a Bootleg Adjustable Gas bolt carrier. The ability to increase or decrease gas flow due to ammunition type and temperature shifts would be a huge benefit. It will be the next item I purchase for this rifle.

I didn't know that increased pressure increases burn rate as well. Good to know. And you're correct, the likelihood of manufacturers using the same powder in XM193 and MK262 ammo is very slim. I'm pretty sure those two loads call for a specific (and different) powder. I know that throws a direct comparison out the window, but the concept I illustrated in my last post should generally hold true with varying effects depending on powders used. Heck, maybe I should load some 55s and 77s with the same lot of powder to see if there is something to the theory. 24.8gr of Tac would work with both 77gr and 55gr loads. Regarding keeping pressure variances in a narrower operating window, I think the only good ways to accomplish that is to: A. Increase barrel length past the gas port like in a carbine length gas system (traditional dwell) so that the suppressor's added dwell is a non-issue. B. Run the rifle without a can so the gas can be tuned for a much more consistent traditional dwell. Even super short dwell times work well when tuned right. C. Run a flow-through type suppressor on the rifle. I have zero experience with these designs, but have been kind of eyeballing this brand. http://saimaastill.fi/portfolios/saimaa-still-suppressor-tl-series/ I'm kind of thinking that the increased spring weight only helped me land smack in the middle of the gas adjustments. I don' t think it made the system any less sensitive.

I think you may be on to something. Bear with me while I talk you though this... (Not trying to sound smug; I'm just trying to explain my current understanding and think out loud too.) I've noticed that 77gr 223 and 5.56 ammo cycles more weakly than 55gr 223 and 5.56. Specific examples include Hornady 5.56 75gr Interlock SBR (weak ejection), IMI 5.56 77gr Razor Core (weak to medium ejection), Tula 223 55gr (medium ejection), PMC Bronze 223 55gr (medium ejection), and Federal 5.56 55gr XM193 (violent ejection). Usually I use Tula and PMC Bronze as test ammo as Tula is the wimpiest cycling ammo I can find and PMC is about the softest ammo I would run on a regular basis. Both of these ammo types ejected with more force than their heavier grain counterparts. It should also be noted that in this particular barrel length and gas system combo that the heavier bullets retained WAY MORE energy than the lighter bullets. I.E. 5.56 55gr XM193 chronoed around 2750fps = 924ft/lbs 5.56 77gr IMI Razor Core chronoed around 2625 = 1178 ft/lbs These two loads generate similar amounts of energy when fired from a 16" to 20" rifle, but obviously differ in a 12.5" mid length gas. Perhaps this suggests a more thorough powder burn when shooting heavier projectiles in shorter barrels? Does a more efficient burn result in lower dwell pressures in the suppressor? I've looked at reloading manuals and noticed that ammunition using a 77gr projectile is usually loaded with 10%-15% less powder than ammunition using a 55gr projectile. Less powder means less gas volume being produced. Is it possible that once the projectile leaves the barrel and enters the suppressor that the sudden increase in volume allows the 77gr ammo (low gas volume) to drop significantly while 55gr ammo (high gas volume) better fills the volume of the suppressor and provides a greater dwell pressure? (See child like drawing I attached below.) To reiterate, dwell duration is identical for all ammunition types. Only the dwell pressure is changing between different ammunition types, and that is due to increased gas volume provided by typical powder charges associated with lighter bullets, and vice versa.

Thanks for the well thought out reply. I do have a full mass system and I've been tempted to give it a whirl. A lot of what I'm going to talk about is based on my current understanding of how ARs operate, so feel free to correct me and take it all with a grain of salt: I think you're right, generally suppressors and SBRs don't play along very well with low mass setups. Short lock time from pistol/carbine gas ports, increased port pressure, and increased back pressure all make running a suppressor a pain. Then add a low mass BCG and buffer and the action may unlock even sooner and thus cycle more violently and increase blowback to the shooter's face. What I've done to counter act this is use a midlength gas system to increase lock time and reduce port pressures and then added the can to increase dwell lost by running a 12.5" barrel. Although I am getting increased dwell time, I may not be getting the increased dwell pressures I thought I'd get from adding the can. I'm also using a Tubbs flatwire spring which increases BCG lock up force by a few pounds which should help keep the low mass BCG in place longer, dropping pressure further before extraction. I measured it once and I think it was increased by 20% or so, but don't quote me on that. Possible solution: I could switch back to a (shorter) carbine buffer tube which would further compress the buffer spring (I.E. add weight and increase lock up pressure) and thus soften recoil with the "harsh cycling" ammo. Or I could get a 308 spring (Tubbs or standard) and trim it to weight. But If I lost BHO with standard ammunition, I'd be back at square one. What is goofy to me is that this effect can usually be accomplished by adjusting the gas block down one click. Less gas will better match a softer spring. But my adjustable gas block clicks on this 12.5" mid-length gas barrel make huge changes in ejection. So I assume it is making huge changes in gas flow. Usually, when running a 16" mid-length with low mass, I can adjust gas to the lowest point where I get BHO with my weakest ammo and then increase the gas by one click for added reliability. The system then runs all ammunition equally well, without ejection surpassing 3:00. Right now I feel like we're super close to getting this nailed down. Maybe the increased spring weight will do the trick. Just saying it out loud sounds right. Like this: ((BCG weight+buffer weight)+spring resistance) = (gas pressure from port depending on ammunition type) Assume "=" means appropriate gas. Not too much, not too little. If low mass means that I am unwilling to add weight, if the gas block cannot fine tune between settings, and if I am unwilling to manage ammunition type then all of these variables are fixed. The only solution is to adjust spring weight and hope that a true sweet spot even exists between gas settings. If not, then something else will have to give.

UPDATE: I tried running the rifle with a slightly heavier flatwire spring and a standard rifle length spring. No gas adjustments were made during the test. Both springs reduced felt recoil with the harsh cycling ammunition and brought ejection from 1:30-2:00 back to 2:30-3:00. Other soft cycling ammunition retained bolt hold open. I wouldn't call this "problem solved", but I would say that the new buffer spring has enlarged the rifle's operational sweetspot. I'm still open to ideas on how to make this rifle less ammunition sensitive, so keep 'em coming!

Another good option, but MicroMOA is currently closed for business. I had been trying to purchase one of their 12.5" Midlength barrels for this very build for over six months. I emailed, left voicemails, checked forums and tried calling distributors and no one could give me a straight answer if they are out of business or not. I hope they return because I've used a Govnah and it worked pretty well. That said, I didn't really care for the gas that it bled under the handguard. Skinny handguard + Govnah = keymod shaped exhaust blast marks all over my hands. Plus I'm not sure if the Govnah would fit under my SLR Helix handguard; it's pretty tight in there.

What you wrote pretty closely reflects my thoughts, but I posted here because I'm open to new ideas. I've seen video showing that the Superlative Arms block reduces velocity when in bleed off mode. Since this is a 12.5" setup, velocity is already in short supply. I'd rather find another fix, but it is an option. Thanks for the input. I forgot to mention this as a possible solution in the main post; Would it be worth installing a Bootleg adjustable BCG in conjunction with the SLR Sentry 7 I already have? I figure that it'd add some unwanted mass but would also allow me to quickly reduce gas for "harsh recoiling" loads.

I have an AR-15 running the following setup: 12.5" Midlength gas Triarc TRACK barrel Silencerco Omega (dedicated suppressed) RCA low mass BCG SLR Sentry 7 adjustable gas block A5 buffer tube A5 buffer (reduced weight using KAK aluminum weights) Tubbs flatwire spring Function is consistent and 100% reliable with any one single type of ammunition, BUT I am having issues with ammo sensitivity when changing from different loads. In previous builds using similar components (but 16" mid and non-suppressed) I have had a wide band of reliabilty. Once gas is properly set the rifle runs to BHO with everything from weak steel cased 223 to full house 77gr 5.56 ammo. When gas is tuned for the 12.5" rifle listed above I get flawless performance (4 o'clock ejection and BHO) from roughly 50% of the different ammo types I shoot. The other 50% ejects at 2:00 to 2:30 and makes the gun vibrate harshly when shooting. Function is 100% consistent when running a single type of ammo. If I decrease gas by one click I lose BHO on the softer ammo, and the more violent cycling ammo will then cycle smoothly. To clarify, some low pressure 223 cycles violently and some cycles properly. (I.E.5.56 55gr XM193 cycles violently, but 5.56 77gr MK262 Mod1 cycles smooth.) What gives?! Any suggestions to remedy the problem? EDIT: OPTION #1 Would anyone recommend replacing the low mass BCG with the Bootleg adjustable BCG? https://www.weaponoutfitters.com/bootleg-adjustable-carrier.html PROS- On the fly fine tuning between gas settings. CONS- Added mass, possibly added maintenance, cost. OPTION #2 Should I skip all this head-scratching and just shoot ammo that functions properly in my rifle? Or is it wrong to run my rifle in such a narrow window of operation?

adamge- Good idea on cleaning the second time after trimming. I wonder if case lube may build up in the Trim-it as I use it and mess with trim length. Thus far, I haven't noticed any residual brass shavings in my brass as I reload, but you never know... Steve RA- I assume that loading out to 2.260 doesn't cause feeding issues in your AR and that you've had good accuracy results reloading this way, right? Also, does loading out longer help with accuracy or does it increase case capacity? Both?

bigedp51- "Rat turd in a violin case", I'm going to remember that one. Ha ha! Thank you for the well thought through reply. I'll take a deep breath, put my OCD on the back burner, and go back to reloading per usual. While I'm not trying to eek out every last bit of accuracy from this rifle, I do want to make sure that I'm doing things properly. I will follow this proceedure when reloading. Polish brass in media tumbler Lube/deprime/resize to .003-.006" smaller than fired brass headspace dimensions in a single stage press Polish in tumber again to remove lube Trim brass to 1.753"/chamfer and deburr using Trim-it II Swage primer pocket [only if necessary] Prime/drop powder/seat bullet in Dillon 550 [Note: Bullet seated to max COAL that the magazine will allow, usually 2.250"] Does that sound about right? Am I missing anything along the way?

This question is a little convoluted, but is a window into my reloading mania. In advance, thanks for taking the time to read it. I appreciate the help. I recently set back the headspace of some reloads causing the occasional double feed. This led on a quest to better understand headspace and it's effect on accuracy and function of the rifle. My journey began by measuring headspace using a Hornady headspace guage. It works well and led me to believe that headspace should be around 1.451"-1.455" according to factory loaded .223/5.56 ammo. I then began measuring the headspace of cases that had been fired through my rifle and found that it was 1.459 +/- .001" So, question #1: If my fired cartridge's headspace measures 1.459", what should I adjust my resizing die [headspace-wise] to optimize function and accuracy? Moving on... In order to tune my cartridges headspace, I purchased a feeler gauge set to help adjust the resizing die. I started experimenting with different headspace measurements to see if they chambered properly. To my surprise, when chambering a dummy round made of a piece of resized brass [at 1.458"] and a 55gr bullet, the headspace measurement shrank after being chambered. Specifically, it reduced itself from 1.458" to 1.454" after releasing the bolt hold-open and letting spring power chamber the round. In contrast, when riding the charging handle forward and slowly loading a round into the chamber, the headspace measurement does not change at all. Question #2: Why is my headspace measurement shrinking after chambering a round?! Question #3: What do you believe this rifle's actual headspace is? Or, how would you go about determining my rifle's exact headspace? For what it's worth, I've tried chambering longer headspaced brass and gotten cases stuck. I've also tried chambering much shorter headspaced cases until it caused failure to extract issues. I've at least determined a sweet spot to keep the rifle reliable. Another thought on headspace in the AR platform is that cartridge overall length is limited to magazine dimensions and as such, loading the bullet until it is a few thousandths off the rifling is not really an option. Since loading the bullet just shy of the rifling is not an option, the next best place to look for accuracy is properly headspacing cartridges. Question #4: Will adjusting headspace result in better accuracy? Again, sorry for such a convoluted post, but the questions feel too interconnected to separate.