You have mentioned more than a few times, that you experience poor accuracy performance (and/or temporary POI shifts?) for a few rounds, after switching from one type of ammunition to another. I know I am ultimately going to have to try some stuff out, but I am curious if there is a way around this. My goal is to have a more consistent, accurate, precision ammunition, and a low-dollar FMJ, that I can seamlessly switch between. As in: I want to be able to go from shooting the FMJ, to a mag swap, and have precision performance out the gate; no "settling down". I suspect I have experienced the phenomenon you describe, and I want to mitigate it. The chosen performance ammo is 73gr Hornady FTX; perhaps I need to try some Hornady FMJs. Or you can tell me I suck, and I am not experiencing the phenomenon you described; that'd actually save me some hassle. I have perceived deviances of about 1MOA.

The accuracy and POI issues when switching among ammo types may, or may not, exist on your rifles. Every barrel is different. There are many permutations of ammo rotation. I know the issues exist on all my AR15s, so I expect accuracy/POI for a few rounds after switching. It's why I shoot ball ammo only once in a blue moon, and even then, I'll clean the barrel before I shoot quality ammo in that rifle.

I discussed this issue years ago with buddies who compete in similar matches. For various personal reasons, none of them switch between match and FMJ ammo within a stage or match. All of them handload, and thus they aren't all that experienced with the variability I see in factory ammo types.

Nikonuser suggested that the ammo switching issues may be caused by different powders. It's plausible. Match ammo is likely loaded with more consistent and more expensive powders than FMJ. Probably the best way to test this is by hand loading FMJ and match bullets with the same powder(s), then switching back and forth. But I doubt competitors seeking consistent match ammo results will load FMJ bullets with something like Varget. They just won't waste their expensive powder on a bullet that is inherently inaccurate.

Thanks for that explanation, fritz. I had not really focused on the issue until KSGM brought it up again now, but it’s something to be aware of. Although I don’t make a frequent practice of it, I have fouled a clean bore with something other than a premium load I was testing to avoid any possible “cold, clean bore” effects, but even if switching ammo types isn’t always an issue, it’s something to keep in mind.

Always learning something new.

I began competing in the AR15 matches in around 2017, or maybe the prior year. Precision and 2-rifle competitions, generally with targets from 5 to 600 yards. There were occasional 800 yard WTF targets in windy foothills of Wyoming, which were just hope and pray specials.

I began discussing AR15 ammo issues in the SF long distance rifle thread about that time. Those matches were new to me, and likely new format for some other shooters, too. Lots of experimentation with rifle setup, optics, ammo, tactics. The 3-gun guys often used what they were comfy with -- 14-16 inch barrels, 55 FMJ ammo, LPV optics, lots of ammo burned per stage. The guys with precision bolt action backgrounds often went with 18-20 inch barrels, match ammo, mid-power zoom optics, one-shot-one-hit mentality. Positives and negatives to both, but neither one was optimal for 5-minute stages requiring both fast CQB and long-distance precision.

I've watched 3-gun guys dump 60 rounds of ball ammo on a 10-target stage, and not hit all the targets. Sounded like a war zone. On my good days, I've cleaned certain 10-target stages with a handful of match rounds left over in a single 20-round mag. Note that such stages are 10 steel targets -- unlimited rounds to make one hit per target.

The challenge of what ammo/gun/optics/tactics comes with the stages comprised of a handful of close paper targets shot on the move, and a handful of steel targets in the distance. The close targets were often reduced size IPSC, with an A zone of about 1.5" wide and 3" tall. Two hits in the A zone were required to score. At 5-25 yards, ammo type is irrelevant. The subsequent steel targets might be a combination of 3-5" diamonds at 100-150 yards and larger plates out to 400 yards. The steel targets generally required better ammo, or spray-and-pray hosing from FMJ.

I began to suspect that the transition from FMJ to match ammo was a problem when I couldn't reliably hit 3-4 MOA targets at 100-150 yards. The impacts just danced all around the plates. With time short, I sometimes moved on to plates at 300-400 yards and just center punched them. When time allowed, I returned to the 100-150 yard targets, and I hit them with ease.

I tested the ammo switch at my home range and found that none of my factory match ammo options shot well immediately after 55 FMJ. My match ammo options include FGMM 69, Hornady HPBT 75, and Hornady ELD-M 73. All three of these loads are capable of 1/2 MOA accuracy under the right conditions. Having a few rounds of 2-3 MOA from match ammo, with no consistent deviation was unacceptable to me. That's when I ixnayed ball ammo.

fritz has a good memory. I remember offering that explanation about different types of powder in one session.

This issue is fairly obscure nowadays because handloaders do not have a wide array of powders usually. With prices and availability of components, and especially with the amount of information available on the web, they will usually select a powder and work with that one.

In days of yore, it was not unusual to have multiple canisters of various powders and people tried various combos. I started handloading in the late 70s, very early 80s, way before the Internet of today. Information was sparse and the trick was to look in books and try out various combos until you found something.

I "remember" reading about how switching powder types would impact the next few rounds and the solution was to do a quick clean of the bore, or live with it.

Nowadays, you ask on a board, which powder for such and such, and you go with the most responses. If you can find it.

Ammomakers may use types of powder that are not available to handloaders, so keep that in mind.

A quick nylon brush followed by a patch of 2 and you should be good.

So, as an experiment in a (somewhat) field-expedient remedy, I asked the LGS to order an Otis "ripcord" for me. Unlike the Hoppes boresnakes, the ripcord doesn't have a metal bristle brush woven in. The idea is, when making the switch to a different ammo type, give the the ripcord a couple passes, and mitigate the settle-in issue.

Soooooo, my first test with the ripcord is either inconclusive, because I jacked it up, or very telling that this isn't a good approach. I shot some FMJ; maybe 15 rounds; then went and shot two rounds of FTX from 300M, at my 6" plate. In between, I removed the Eotech and installed the scope, installed my bipod, switched to the mag with the FTX, removed the silencer, pulled the cord through twice, and reinstalled the silencer. My first shot hit about 3.5MOA high (I didn't feel myself mess it up; certainly not to that degree). My second shot barely missed, off the top edge. Is it possible that swabbing the barrel like that could cause that kind of a shift?

I noticed this in my AR platform as I was trying to use 55gr FMJ on the short range targets and then a 68gr or 73gr dialed in for accuracy for longer engagements. I had the dope correct but the groups wore poor as compared to firing them by themselves and it would get squirrely in windage. One the of old timers doing bench rest down the firing line told me it was due to the differences in bullet jump and fouling in the bore. I've never proved it out but it made some sense.

quote:

Originally posted by KSGM:
Soooooo, my first test with the ripcord is either inconclusive, because I jacked it up, or very telling that this isn't a good approach. I shot some FMJ; maybe 15 rounds; then went and shot two rounds of FTX from 300M, at my 6" plate. In between, I removed the Eotech and installed the scope, installed my bipod, switched to the mag with the FTX, removed the silencer, pulled the cord through twice, and reinstalled the silencer. My first shot hit about 3.5MOA high (I didn't feel myself mess it up; certainly not to that degree). My second shot barely missed, off the top edge. Is it possible that swabbing the barrel like that could cause that kind of a shift?

IMO your test is inconclusive -- from stacked variables and from limited data.

If you want to test a variable, it must be the only variable. There are too many moving parts.

A two-shot group is fine if you are absolutely certain that your two shots were consistent and repeatable. This is where one-shot dot drills provide experience to fall back on.

FTX may, or may not, shoot accurately immediately after a sorta-kinda clean bore.

I performed another brief, though seemingly somewhat conclusive, test. Five rounds of FMJ, followed by scope off/on, followed by three rounds of FTX at my 300M six inch plate. I tried it with PMC XTAC 55gr, PPU 55gr, and Hornady Frontier 62gr; in that order. I broke position between FTX rounds. The FTX after the PMC all missed a bit high/left. Hit 2/3 after PPU. Hit 2/3 after Frontier. I re-tried the PMC, to see if that was a fluke. All missed; two low and one high. So, it seems that the PMC doesn't play as well with the FTX as the other two. I think this data is conclusive enough for me to avoid PMC, if I want my FTX to hit correctly, after a switch.

I do agree with your assessment of my previous test, fritz. I am bad about sharing most everything related to a subject, regardless of it's thoroughness or validity. For the sake of conversation, I guess.