# of rnds for testing

[TREERAT]

if you were only concerned at finding if a load will lead in a rifle, how many is sufficient to detrrmine that? would 5 rnds be enough to make a decision from. in other words if it is going to lead the bore will it do it in 5 rnds or will it take more.

[BABore]

Probably more than that. It will depend on the reason for the leading. Undersized boolits will lead pretty quickly. Barrel constrictions may take a few more rounds. Lack of lube capacity in the design, lube quality, velocity exceeding alloy or lube, powder type, these all may take quite a few rounds. And to top that, every gun is different.

Initially resolve the boolit fit and barrel condition problems first. Then work up a good load while watching for signs of leading. Tweak the rest latter with a known good load. There are no short cuts.

[archmaker]

I do not know if I would worry, unless I was competing. I mean within reason.

I would do my work up for the load and examine the bore after each "group".

However, when I shot IHMSA I would develop a load using 5 shot groups, and then when I found the most accurate I would then shoot 8 - 5rd groups to make sure the last 5 are as accurate as the first 5.

You just have to determine what you are going to do with the load and what you are willing to accept. I do not know (frankly I would like to know, if someone has really tried it) but I would guess that any load could eventually lead a barrel after X number of rounds, of non-stop shooting, and no cleaning in-between.

[captaint]

Tree, If it were me, I would give 25 or 30 anyway. I'm not sure 5 is enough. Mike

[Recluse]

For rifle, I start with three-round variations just to see if my load is even going to make it on the paper.

Once I determine/find a load that makes it on the paper, I up the number to five shot groups for testing.

But, I also start with the gun in the same condition every time. In other words, I generally start with a clean bore--that's one variable in this whole process that is easy and cheap to control.

And, since some rifles do better with a "warm and fouled" bore, I'll often load up "waster rounds" that I just load up and send down range for no other purpose than to warm up the barrel and get a bit of fouling in it. However, I've found this to be more "critical" with jacketed projectiles than Pb ones.

[Echo]

Well, ONE round is enough to make a decision on. I wouldn't put too much faith in the decision, though.
Researchers and others involved in inferential statistics say that a sample size of about 30 is best. They will also say that you can use fewer if that is all you have. Increasing sample size reduces the error term, but how much accuracy do we need? I'm speaking of accuracy of estimate, not accuracy of the load.

For my own efforts, I shoot groups of five, and am a happy camper.

(Taught Stat, Research Design, and QC at university level)

[runfiverun]

when starting with a clean bbl i have noticed it takes between 7 and 11 shots to get the bbl lubed all the way down and for a star to appear.
kinda funny as i was shooting them over a chronograph at the time, and could pin point when the star would appear from the velocitys.
since leading is caused by different issues pressure,running out of lube,pressure drop-off,inflexability of the alloy,etc..
you need to determine what where and why to determine when.

[TREERAT]

I think some of you missed the part that my only concern at this point was checking for leading, accuracy is not a concern at this point, I will fine tune that after. just wanted to see if 5 rnds of each powder charge working up one grain at a time was enough to tell if that particular charge weight would lead before moving up. from your responses it sounds like it may not be enough number of rounds.

I want to increase the powder charge till it just grays the bore, then decrease 1/2 grain at a time to find the most accurate charge. this should give the fastest load that will not lead up the bore, and still be accurate.

[Blammer]

3 rounds. I've done some "leading" testing and 3 rounds is a good indicator.

of course on some tests it's only taken ONE round to lead the brl from end to end.

[Doc Highwall]

I think their are a lot of variables some more important then others. I would say that boolit fit is the most important followed by lube. Next would by your alloy and the pressures that are generated by the chosen powder. My own test is with my Remington 40X in 308 Win that I am shooting right now. My alloy is indoor 22lr range lead mixed with tin to make a 30:1 alloy, with SAECO #315 175gr TCGC and Hornady gas checks that have been annealed and sized .310 in a SAECO luber sizer. For cases I am using Federal Gold Medal with Remington 9 1/2 primers, powder is AA5744. The first 100 cases were charged with 19 grs and the rifle was shot with all 100 rounds then cleaned with no leading at all. This is the load that I used in the bench rest match to shoot a 10 shot group at 100 yds that measured .781 and was shot near the end of the 100 shots with no cleaning. My next test is to increase the powder charge in .2 gr increments every 50 shots until the group opens up by either too much pressure for the 30:1 alloy or leading occurs. I now have 100 shots through the gun at 19.4 grs and the group seem to be getting smaller. I am now loading 50 more at 19.6 grs and I am not going to clean the rifle just to see what it will do. Attached are the last two groups that I fired with the 19.4 grains of AA5744, and these are thrown charges not weighed. Almost forgot the lube I used is from the BULLSHOP it is his NASA lube hint hint

[waksupi]

Maybe not directly related to the original question, but 10 shots is the standard we use for testing cast boolit loads.

[Doc Highwall]

My point is that I have no leading after 100 shots with out cleaning and still have this level of accuracy. I am going to see what happens after 150 shots between cleanings. TREERAT wanted to know how many shots it would take for leading to appear in a rifle. If I am lucky I might be able to shoot several hundred between cleanings with out any loss of accuracy. This might not be important to some shooters but my goal is to be able to shoot a 100 shot match plus sighters with out cleaning the rifle so as not to make a variable after cleaning to let the barrel be coated when you only have two sighters and the third shot out of the gun is for record. I have seen this happen in matches after a competitor cleaned their rifle and it took too many shots to let the barrel settle down.

[mainiac]

I think all guns are a rule unto themselves! My new aquired .32 special marlin has over 400 rounds threw its barrell,and has never been cleaned yet. It shoots groups so nice,that i see no sense cleaning it. I peek up the bore once in awhile,and it always looks shiney,just like a mirror.

[joeb33050]

Maybe not directly related to the original question, but 10 shots is the standard we use for testing cast boolit loads.

I don't use 10 shots for testing cast bullet loads. I use five 5-shot groups for the test of accuracy, comparison between loads. The Rifleman now seems to use 5-shot groups, frequently 5 of them, to test.
I don't know what this means. 10 shots total? Or 10 shot groups?
Which "we" is this?
joe b.

[runfiverun]

the greying of the bbl probably isn't leading it's called antimonial wash if you want that just shoot high antimony boolits.
leading and wash are different things.
i have a couple of 24" bbld leveractions that i haven't cleaned the barells in15 years no leading and no loss of accuracy.
no, they ain't safe queens.
when testing lube for a particular rifle i will shoot it for almost a full year,i keep taping a target over the original and shoot 20 shot groups,over a wide range of temps and weather conditions.
headache yep, i have 9 separate lubes on the bench right now.
notes man notes.

[waksupi]

I don't use 10 shots for testing cast bullet loads. I use five 5-shot groups for the test of accuracy, comparison between loads. The Rifleman now seems to use 5-shot groups, frequently 5 of them, to test.
I don't know what this means. 10 shots total? Or 10 shot groups?
Which "we" is this?
joe b.

Those are ten shot groups. That is the amount established back in the old Shooters.com days, and it has been a good standard to test cast loads.

[relic]

Yeah, I have often wondered what barrel leading really is or looks like. Pistol or rifle. I dont think the graying being uniform is leading. I shoot a dozen different rifles with plain based boolits. If accuracy falls off I will run a patch or two and usually all comes back to normal. Barrel looks shiny, back to shooting. I usually have a target for data that I wan t to achieve, such as accuracy,& velocity, even testing different loads while working up Ive not had severe leading that you can see. Some harder alloys will leave little specks of lead on a patch after firing, but never severe, it shows up in my 44-40s a lot with some harder commercial cast boolits, my home cast softer boolits are just fine. Ahaa, there is just so many variables not enough time to discuss all of them. I think I got off track. I load 10 rounds when testing new loads. I also know what I want to achieve before I start. This cast boolit site is the best place to look for info.