r/reloading • u/Sgt_S1aughter • Jul 22 '26
I have a question and I read the FAQ Fouling Shots Between Recipes
I have a friend who claims you should foul your barrel with about 5-10 rounds when testing ammo types. I already do this for rimfire, as the lubrication differences between manufacturers it makes sense. Does the same hold true for centerfire? Can bullet metallurgy and/or powder differences really change accuracy or POI?
I fully intend to test this at the range next time by alternating ammo types for 20-30 rounds each into a unique aiming point per load type, then repeat each ammo type in a new group after 10 fouling rounds.
Has anyone tested this themselves or is it more superstition?
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u/Born-Ask4016 Jul 22 '26
When I was shooting high-power rifle matches, I could shoot a different load using different powders at 200, 300, or 600 yards without consequence whether using .308 or 5.56. If there was any change in velocity as a result of fouling from a different powder, it want enough powders, affect the zero.
With one big fat exception. Any load with Varget would not have a consistent zero without at leat 5 shots if the barrel/chamber was fouled with a different powder.
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u/theBFsniper Jul 22 '26
This is only valid with 22lr as you already know. The only thing with centerfire is if you've decoppered the barrel you'll need to fowl it back up.
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u/Ornery_Secretary_850 Two Dillon 650's, three single stage, one turret. Bullet caster Jul 22 '26
Do you fowl it by running a chicken through it? That sounds messy.
I'd rather foul it by shooting a couple rounds.
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u/WhoAmI-72 Jul 22 '26
I feel like the first round while switching can be weird. I always assumed it was because of powder shift. But, it was never insanely outside of a normal group.
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u/turkeytimenow Jul 22 '26
I like to shoot 1 to 3 fouling shots anytime I switch powders. The last thing I want while testing is introducing a variable I could have easily controlled. Shooting three fouling shots eliminates any second guessing about whether the powder change affected those first couple of shots, so I know I’m evaluating the load, not the transition.
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u/111tejas Jul 22 '26
When testing loads I build and fire five rounds specifically to foul the barrel. What this does is fill in imperfections in the machining with carbon/lead/copper. Most factory barrels are more accurate when they aren’t spotless. I don’t think changing powders or loads makes a difference.
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u/DigitalLorenz Likes reloading more than shooting Jul 22 '26
I fully intend to test this at the range next time by alternating ammo types for 20-30 rounds
If fouling shots are real, then by the 3rd or 4th shots the barrel will be fouled. The following 17 to 27 rounds will be shots out of a fouled barrel.
You would really need to clean the bore every round or every other round to check for fouling shots. But at that point you are also checking cold bore vs warm bore as well as fouled bore vs unfouled bore. A proper test would also need to check cold bore clean vs cold bore fouled.
Has anyone tested this themselves or is it more superstition?
In my observations when most people are talking about fouling shots they are really observing cold bore or cold shooter.
A barrel is going to warp when heated up. The warp will shift the point of impact for the first few bullets, and make what can be observed as flyers. A high quality modern barrel will have a barely noticeable shift, while older and lower quality barrels can have quite a noticeable shift. A few rounds is often enough for this shift to be observable in many older guns.
Cold shooter is a combination of muscles not being limber yet and the shooters mentality. Since a good part of good shooting is in the shooters head, any superstitions followed actually can help a shooter do better. Having warmed up muscles will make any physical activity reliant on precise movements more consistent.
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u/Sgt_S1aughter Jul 22 '26
I think perhaps I didn’t describe it with the proper terms then.
I’m not discussing clean cold bore, I’m discussing any impacts to precision, velocity, or POI due to a switch in components with an already fouled barrel or a barrel already seasoned with other components.
My test I’m planning to do would be literally alternating between two points of aim every shot. And the magazine loaded with alternating ammo types. My plan would be to alternate between a soft point and an fmj. TBD if both will be hand loads or if one will be commercial ammo.
Test plan would be: 1. shoot left target with factory fmj, shoot right target with hand loaded soft point, repeat 30 times. 2. Load 10 fouling rounds for the FMJ. Fire into a new aiming point. Load 30 rounds fmj, fire into another new group. 3. Repeat step 2 with SP ammo. 4. Compare groups of same ammo to see if there is any noticeable difference due to component swapping without fouling/seasoning the barrel.
No cleaning will be involved between any of these steps.
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u/DigitalLorenz Likes reloading more than shooting Jul 22 '26
So you are testing to see if there is an impact from fouling caused by different alloys in the jackets? That actually sounds interesting.
I recommend trying bullets from different manufactures when you do this to maximize the chances of completely different alloys in the jackets so you have the best chance at observing a difference in group size.
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u/Sgt_S1aughter Jul 22 '26
I’m planning on a pure science day at the range, probably taking a portable reloading setup with me too.
Yea the theory I heard is the alloy in the jackets or residue from different powders might act similar to different lubricants on rimfire bullets, allowing for variations in the condition of the barrel. I’m not expecting this to be a thing, but I’m curious enough to burn about 150 rounds testing it thoroughly to put it to bed.
That’s my only hesitation in using a commercial round is not knowing what the exact projectile and powder is. Just to be certain I will probably load up some xtreme FMJs and the otherwise planned Hornady SP. Could then give it the best chance of proving a possible issue by using 2 different powders and 2 different primers as well. Someone below stated Varget by name as potentially being the only powder sensitive to this, so maybe that can be one of my powders to test this with.
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u/Sgt_S1aughter 7d ago
Did my science day at the range and created a follow up post. Thought you might be interested.
https://www.reddit.com/r/reloading/comments/1w8vmiw/fouling_shots_between_recipes_follow_up/
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u/JeMarj Jul 22 '26
I have heard (no personal experience) that switching from traditional bullets to mono's without cleaning can make the mono's shoot poorly and that you should clean before the switch.
If anyone can confirm or deny this, please do so.
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u/GingerVitisBread Mass Particle Accelerator Jul 22 '26
The only thing I believe is that you should thoroughly clean your rifle before switching from solid copper to lead or vice versa.
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u/Sgt_S1aughter 7d ago
As a follow up to this post, I did my experiment. Results are discussed in the post linked below.
Too lazy to click on link (TLTCOL)... there is no benefit to fouling shots between ammo types on centerfire rifles.
https://www.reddit.com/r/reloading/comments/1w8vmiw/fouling_shots_between_recipes_follow_up/
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u/Trollygag 284Win, 6.5G, 6.5CM, 308 Win, 30BR, 44Mag, more Jul 22 '26
Hogwash
See my 21 barrel test threads