Longranger

Blackjack988, Berger 6.5mm 140gr Hybrids are Target, right? If so, I’ll take all 500. Let me know. THX!

I found GRT while searching for an alternative to QL. Actually, I was thinking of doing my own program from scratch, but I like to snoop around and see if anyone else has been there done that before I reinvent the wheel. I was so impressed with GRT that I become a patron that supports their efforts. GRT runs on Windows and Linux. Wide support for Windows, only one distribution of Linux has been thoroughly tested. GRT is available for free, but it is not open source. Public release updates are provided in Windows and Linux versions. Interim (or beta) updates are made available to patrons and only for Windows. I think the model that provides the basis for the data is better (as in more accurate) than that used in QL and GRT includes a plug-in that allows any user to upload their load, chrony, component measurements, and pressure data (if they have Pressure Trace) to a database that is used to continually refine the powder burn characteristics. The whole project seems exceptionally well thought out to me. Now for some of the inner workings of GRT. The program includes an OBT feature that supplies full and half node values and a target analysis module. Accurate results REQUIRE inputting exacting measurements of your fired case capacity and measurements, barrel details, and bullet weight and measurements. Default values for almost everything are preloaded in the database and wildcat cartridges and new bullets are added to the database as fast as users upload new info. Do I sound like a salesman for GRT? Sorry about that, I just think it’s an amazing tool that has resulted from the combined efforts of a great reloading community. The GRT community forum is hosted on Discord, which I had never even heard of prior to stumbling across GRT. Then I found that NJGF is also on Discord. No cost to join the forum, but patrons get a few perks like direct support and communication with the development team. I haven’t found anything about GRT yet that I don’t like, so that’s also a plus.

Forgot to answer your question. Lower powder charges for heavier bullets are typically due to the pressure increase associated with getting the heavier bullet underway. Lighter bullets are easier to get moving and the pressure rises more slowly.

kc17, I just ran what I think you're looking at in GRT load simulation software. Looks like 3.4gr of Titegroup is bumping up against the max recommended pressure. This is just a simulation, like QuickLoad software. So, all normal warnings regarding working up a load apply.

winmag45, Well, I didn't pull my 590A1 apart to check, but I just happen to have an aftermarket pistol grip stock for a Mossberg lying around here and it has a short attaching bolt that is a 5/16-18 thread. Hope that helps. -Longranger

If those shorter cases are good except for the length of 1.138", I'd use them. SAAMI spec on 38 SPL case length is 1.135" to 1.155". Just check after firing that they haven't shrunk below the lower limit. Not sure what you're measuring with, but you're really splitting hairs here. I'd use a 1"-2" micrometer that had been set with gauges if I thought the length was that critical. -Longranger

Dead on precise for COAL? Shorter tends to increase pressure, which you'd need to watch closely at maximum or near maximum loads. Longer - problems fitting into mag if way too long or maybe chambering in a revolver. SAAMI spec for max 38 SPL length is 1.550". What COAL are you getting? -Longranger

Crimps look ok from what I can see. 1 or 2 thou over on COAL should work. -Longranger

Torkk, Wipe the funnel and powder measure hopper inside and out with a Bounce dryer sheet. Ground the powder measure. Throw a charge, weigh it, record the weight, throw that powder back into the hopper, repeat ten times. See if you're getting consistent the weights. You need to do the same motion everytime you throw a charge. Slow or fast or tap 3 times - whatever. Just make sure you throw charges the same way each time. Report back with your progress please. - -Longranger

I'm interested. Where are you located? -Longranger

Kansas City Firearms and Cornerstone Arms are showing 1 pound cans available for online orders. -Longranger

PK90, I've had a standalone Snap-On borescope for a long time. It came with a small tip, a large tip, and 90-degree adapters for looking sideways instead of straight ahead. It records video or photos onto an SD-card. I think there's been lots of progress in the tech since I bought that and there are now some pretty fancy USB borescopes available. Prices vary all over the board. -Longranger

Hodgdon website says COL for the 115gr LRN loaded with Titegroup is 1.100. You're pretty much right there at 1.103. -Longranger

Do you have load data for the ibjiheads bullets and titegroup? It's generally not a good idea to just change bullets and expect the same recipe to apply. Sounds like the coated bullets have a much more round profile than the FMJs. -Longranger

If the Tool Craft and PSA are both full auto spec, they're probably the same weight. Oh well. If the SPR gas rings test ok, no leaks in the gas system, gas block is properly aligned to the gas port, and the gas port is not undersize or partially clogged, I think you're down to lightening the buffer or running the 55gr ammo with a heavier charge than the recommended max. I'm curious to hear what you decide to settle on. -Longranger

MartyZ, You did say in your original post that you had checked the gun. Did you test or check the gas rings? Are the BCGs in all your ARs the same weight? I wonder if the SPR BCG is a touch heavier than the others and maybe a little swapping around will get you all guns working with all ammo. -Longranger

I agree 100%. I'm only saying that a 55gr @ 3224fps has the same kinetic energy as a 68gr at 2900fps. Same amount of work was done on the bullet. Different powders, different burn rates, different length of time in the barrel (before and after the gas port), and different pressure/time curves. -Longranger

Well, it sounds like you need to decide if you want to lighten the rifle buffer weight a little and have a bit more recoil on all your other loads just to have consistent locking with the 55gr at the lower charge or run the 55gr above the recommended max charge or just save the 55gr ammo for the carbines. Your call. I'd use the 55gr ammo in the carbines. -Longranger

Barrel nut ID maybe 1.190"? Even better. Do you need to be a gunsmith in NJ to open up a barrel nut ID on a lathe? -Longranger

Dang! ID on the barrel nut is what, 1.182"? So it would just clear if you took 0.018" off the comp OD? Or, opened the ID of your barrel nut 0.018"? 0.009" off the thread height. -Longranger

Tony13, My first thought is that the weld material covering the pin should be aluminum since the comp is aluminum. A drill should be able to get through that, but you run the risk of breaking the drill bit off when it gets through the aluminum and encounters the pin. I'd try operating on the weld with a Dremel tool or a jeweler's file to get to the pin. Remove enough material to expose the full diameter of the pin. Hopefully it's a roll pin and not a solid pin, right? And it's likely in a blind hole. And it's likely made of spring steel. Trying to screw a tap or screw into the pin usually doesn't work. Pack as much grease into the pin as you can. Or, maybe drops of oil if you have zero luck with the grease. Find a pin punch that's a close fit to the inside diameter of the pin, put it into the center of the pin and deliver a sharp smack to the grease or oil. The hydraulic pressure will force the pin out. I've done this with bushings in blind holes before and this is like a miniature version of that process. DON'T FORGET TO PUT YOUR EYE PRO ON FIRST! -Longranger

Very good! Thanks for the update. -Longranger

Interesting. SAAMI spec on case OAL is 1.730"-1.760". So, there's still a little room to go lower if needed. I'm curious to hear the post-weekend report. Is your SPR chambered for .223 Rem, 5.56, or .223 Wylde? Just thinking about any differences in chamber volume (albeit small) that might be in play here as well. -Longranger

I'd trim the cases down to 1.750" and seat the bullets so that the COL is 2.200". At least then you'll be consistent with the Hornady load data as a starting point. Beyond that, any chance your gas system is a little gumpered up or leaky? Maybe you're operating close to the lower limit of the pressure needed to produce a full stroke cycle. Just for reference, how close to the 1.750" case length are you now? -Longranger

Ok. 68gr @ 2900fps is the same energy as 55gr @ 3224fps. So, the question is are you at 3200fps with your loads. Hornady 9th is showing 2.200 COL for the 55gr FMJBT w/c. Is that what yours are measuring? -Longranger