Question: Will a small base die increase speed, and will neck turning affect speed?

[NamibHunter]

Recently acquired a small base die (standard taper) to avoid clickers after 20 reloads of the ADG brass. After using the small base die for the first time, i get heavy bolt click at the top of the bolt opening and experiencing some extraction issues (but now also using new brass that is not neck turned).

Likely cause of the bolt click: MPA chamber is fairly tight, and the standard Hornady FL die probably did not size the case enough at the .200” line (close to the web). So try a small base die…

Sadly my superb neck turned (old) brass (12.1 thou) decided to develop neck splits at reload nr 20, just before the small base die arrived. Dumped them all, as the necks were partially tearing off on the neck shoulder junction, likely from thinning caused by neck turning. Probably went too deep into the shoulder and the cutter angle is too shallow. Got a new cutter that is 38 degrees today, prior cutter was 58 deg.

Moved on to the second half of the batch of 100 ADG cases (same packaging, same batch nr). But decided to try the new brass without neck turning (15 thou necks, a big delta from 12). Same powder batch, primer batch, FL sizing, brass prep (except for no neck turning and an additional sizing step via the small base die). Speed is now running 60 fps faster and i got some mild ejector marks. That was a surprise. Accuracy degraded, probably the speed change took the load outside the prior node. Also the primer pockets expanded too much from the higher peak pressure so brass life will suffer too much.

Next batch is loaded 1.3 grains less powder, and we will see what that does.

Unfortunately the two changes (switch to thick neck brass, and sizing the case even smaller via the small base die) happened at the same time, so trying to untangle the two effects. Yep i know - you should never change more than one thing at a time…

Questions:

1) How much will speed change if the 200 line is now sized 0.8 thou smaller in diameter? Of course the entire case body will be resized smaller, but very slightly. The effort required on the press handle is minimal with a lubed case. Presume “shot start pressure” will be slightly higher due to the smaller usable case volume (total case volume minus volume taken up by the seated bullet) due to the additional sizing step.

2) How much does neck turning affect speed, if you go down a lot, like 3 thou less neck thickness? I wanted to see a sine wave-like carbon fouling on the neck. Total clearance is now 5 or 5.5 thou (based on reamer print). I realize neck turning will slightly increase “effective combustion volume” once the bullet comes to a standstill in the grooves because there is less brass in the chamber, but this effect must be tiny? Case volume before the bullet starts to leave the neck is not affected by neck thickness, or case length, so shot start pressure should be the same.

I believe neck tension is same or very similar, purely based on feel. Annealed in an AMP machine using different codes derived from Aztec mode (and two melted cases). Maybe shoulder softness was slightly different because of the big difference between neck thickness and shoulder thickness, and maybe the shoulder got bumped a little more, or less, changing case volume…. Shoulder bump gauge showed very similar numbers.

Does anybody have any personal test results on these two effects (neck thickness and small base sizing)?

 

[Doom]

Sounds like your load was borderline on pressure. But in general the more the brass has to expand to fill the chamber the lower the velocity will be. Less energy is available for the bullet. The neck issue might be a little more problematic depending on the chamber (neck diameter). I agree that any effect of neck turning should be negligible as long as the neck is free to expand and release the bullet.

I would be suspicious of any results from trying to test and make comparisons between two different sizing dies and making any general assumptions on the results.

 

[Yondering]

Like Doom said - sizing the case down more generally causes lower velocity, not higher. Some of the energy in the powder charge is used to push the case outwards, forming it to the chamber, which also takes some small amount of time, naturally; IMO this contributes to a softer start of the bullet, resulting in lower pressure and velocity.
But 0.8 thou difference? Too small to have a measurable effect IMO.

Neck turning generally causes lower velocity as well, but it's a pretty small effect. I wouldn't look to that as a cause of pressure issues, as long as the neck isn't too large or too long for the chamber.

While I'm not 100% sure what you mean by "bolt click", I have to wonder if your small base die isn't bumping the shoulder back enough. You didn't mention how much you're bumping the shoulder, and IMO that'd be the very first thing to check if you know about it, so maybe you aren't measuring shoulder bump? Just guessing based on the info provided.

 

[Haney]

After how many firings did they start to become clickers ? When you sized the new brass w/ small base die did you use the expander ball or set neck ID with a mandrel ?

 

[NamibHunter]

Like Doom said - sizing the case down more generally causes lower velocity, not higher. Some of the energy in the powder charge is used to push the case outwards, forming it to the chamber, which also takes some small amount of time, naturally; IMO this contributes to a softer start of the bullet, resulting in lower pressure and velocity.
But 0.8 thou difference? Too small to have a measurable effect IMO.

Neck turning generally causes lower velocity as well, but it's a pretty small effect. I wouldn't look to that as a cause of pressure issues, as long as the neck isn't too large or too long for the chamber.

While I'm not 100% sure what you mean by "bolt click", I have to wonder if your small base die isn't bumping the shoulder back enough. You didn't mention how much you're bumping the shoulder, and IMO that'd be the very first thing to check if you know about it, so maybe you aren't measuring shoulder bump? Just guessing based on the info provided.

Thanks for the insights, much appreciated.

Shoulder bump is exactly 2 thou and is checked every time after the FL sizing step (done with a Hornady Custom Comp die). I control shoulder bump with a set of Redding custom shell holders. AMP annealed every time. Pretty sure that shoulder bump is the same as before, after the FL sizing step. Will go check when i do the next batch if the shoulder bump changes post small base die sizing (the Redding die was bored out by Porter Precision, so not touching the shoulder), but presumably the small base die might elongate the brass and move the shoulder out again? Will have to check that.

The original brass had a weight range of 2.4 grain. I culled out the worst 10 (heavy) cases and then sorted the brass into a light and a heavy batch, with a very small weight difference if 1.0 grain. Recently switched from the “light” brass to the “heavy” brass. But 1.0 grain out of 235 grains total (average weight) is less than 0.4%. Could that be the cause of the speed increase?

 

[NamibHunter]

After how many firings did they start to become clickers ? When you sized the new brass w/ small base die did you use the expander ball or set neck ID with a mandrel ?

After about 15 reloads there were light “clicks” at the top of the bolt opening cycle, at my typical load (which is 50 fps below hard bolt lift), and the primer pockets were still fairly tight. Brass lasted 20 reloads, but horizontal neck splits was the cause if their demise, not loose primer pockets. So i don’t think my standard load was especially high on pressure. No ejector marks.

MPA chambers tend to be tight, and the Hornady die is not ideal.

 

[Supersubes]

I dont think the brass is doing it. This is a barrel thing, carbon ring, etc.

 

[Yondering]

Shoulder bump is exactly 2 thou and is checked every time after the FL sizing step (done with a Hornady Custom Comp die). I control shoulder bump with a set of Redding custom shell holders. AMP annealed every time. Pretty sure that shoulder bump is the same as before, after the FL sizing step. Will go check when i do the next batch if the shoulder bump changes post small base die sizing (the Redding die was bored out by Porter Precision, so not touching the shoulder), but presumably the small base die might elongate the brass and move the shoulder out again? Will have to check that.

I'd bet that's exactly what it's doing. Most likely it's sizing the body down at the shoulder junction, which does push the shoulder forward a few thousandths if the die isn't also contacting the shoulder. That should explain your bolt click.

 

[Haney]

After about 15 reloads there were light “clicks” at the top of the bolt opening cycle, at my typical load (which is 50 fps below hard bolt lift), and the primer pockets were still fairly tight. Brass lasted 20 reloads, but horizontal neck splits was the cause if their demise, not loose primer pockets. So i don’t think my standard load was especially high on pressure. No ejector marks.

MPA chambers tend to be tight, and the Hornady die is not ideal.

Tight chamber and Hornady die are likely the issue . If you made it that many firings without clickers it's not terrible , but not ideal .

 

[Haney]

Quoting a man that knows what he is talking about .

 

[NamibHunter]

Tight chamber and Hornady die are likely the issue . If you made it that many firings without clickers it's not terrible , but not ideal .

Yep agreed.

The rifle is a switch barrel MPA, using the West Texas Ordnance switchlug. Works well and have two bolts lapped into the same action action.

Allows me to order new barrels in a new caliber/chambering without having to ship the rifle to a gunsmith and wait for weeks/months every time. That is super convenient!

My experience has been that tight (match) chambers allow you to shoot factory match ammo (often sized on the small side, to fit all chambers) surprisingly well. But if you buy premium brass and hand load, that is not optimal, as you lose top end speed, and thicker/stronger brass tend to develop clickers, because the standard FL dies are not fully compatible with the tight chamber.

I should really stop being stingy and buy my own reamers. One chamber reamer and another reamer for cutting a custom FL die. Then there is no need for small base dies, or custom FL dies…

 

[NamibHunter]

Quoting a man that knows what he is talking about .

View attachment 8128507

Bart is spot-on with his reply.

Busy doing a deep clean on the barrel. Bore scoped showed a carbon ring in the neck area of the chamber, and significant carbon fouling.

I had a superb 300 WSM load that ran 2855 fps in a 30” barrel with zero pressure signs, very long freebore, HBN coated, except for the slight click at the top of the bolt opening. SD was often in the 4.6 to 5.8 fps range for large samples (35-50 rounds), a superb result, and it shot well (barrel tuner delivered positive conpensation at 600 yards, my longest available range locally). I got tired of the clickers and for the new batch of brass (same serial nr) i wanted to avoid the brass growing that fat and causing clickers, so ordered a custom small base die, with the intent of using it at every reload.

But sadly too many changes all at the same time, and the new load shot way faster using the same powder charge, around 2920 fps and got bright ejector marks, with medium hard bolt lift and primer pockets expanding too much in one firing.

On balance, i would rather live with the light clickers and get back to an SD of 4 fps.

Buyers remorse, i guess…. Will forego the small base die for now and adjust powder load to get to the prior speed. Don’t mess with success!

 

[NamibHunter]

I'd bet that's exactly what it's doing. Most likely it's sizing the body down at the shoulder junction, which does push the shoulder forward a few thousandths if the die isn't also contacting the shoulder. That should explain your bolt click.

Tested this sequence: First lube and FL size the brass bumping the shoulder 2.5 thou. Then run the brass through the small base die (no shoulder in the die): Case head to shoulder measurement grows 0.5-1.0 thou, but hard to measure accurately. Net shoulder bump is now 1.5-2.0 thou, still good enough.

 

[Yondering]

Tested this sequence: First lube and FL size the brass bumping the shoulder 2.5 thou. Then run the brass through the small base die (no shoulder in the die): Case head to shoulder measurement grows 0.5-1.0 thou, but hard to measure accurately. Net shoulder bump is now 1.5-2.0 thou, still good enough.

So does that empty sized piece of brass from that measurement still give you bolt click? If so, I'd get out a sharpie marker and color or soot the case to see what's making hard contact. If not, I'd want to look hard at bullet seating depth and seated neck diameter.

 

[NamibHunter]

So does that empty sized piece of brass from that measurement still give you bolt click? If so, I'd get out a sharpie marker and color or soot the case to see what's making hard contact. If not, I'd want to look hard at bullet seating depth and seated neck diameter.

Not fired them yet. Will report soon.

As is, the twice sized brass allows the bolt to close without resistance.

I doubt it will click until reload 10 or 12…

 

[NamibHunter]

Btw during pressure testing (post fire forming with a medium load), all the high end loads close to book max “clicked”, (1.6 gn below max), well before primer pressure signs, ejector marks or hard bolt lift showed up.

 

[MakeSawdust]

Measure .200 line of sized brass and fired brass. Sized brass should be at least a full .001 smaller than fired brass. Preferably .002 smaller especially when measuring with calipers. (Makes you question is .001 actually .0014 or .0006. Not to mention tool accuracy and measurement error). Also need to check neck clearance and trim length. If those check out it gets fun as you need to use some marking fluid and possibly need a chamber cast to figure it out.

 

[NamibHunter]

Measure .200 line of sized brass and fired brass. Sized brass should be at least a full .001 smaller than fired brass. Preferably .002 smaller especially when measuring with calipers. (Makes you question is .001 actually .0014 or .0006. Not to mention tool accuracy and measurement error). Also need to check neck clearance and trim length. If those check out it gets fun as you need to use some marking fluid and possibly need a chamber cast to figure it out.

Yep, the Hornady “Custom Competition” die (it is neither custom made, nor competition worthy) sized the brass at the 0.200 line by only 0.7 thou. With the small base die used post FL sizing, it is now sizing it down 1.5 thou.

Kenny Porter did a good job, as always.

Neck clearance is 5.5 thou in total (diameter difference loaded vs fired at full pressure).

 

[NamibHunter]

Checked with the bore scope: Just a hint of gray carbon between end of the case neck and the end of the chamber after 40 rounds.

I always clean the chamber and inspect with the Teslong bore scope. So not the cause. Had this problem years ago with a different rifle, and learned this lesson the hard way.

 

[NamibHunter]

Checked the powder serial number: New bottle has a different batch nr, so it seems the new batch is significantly more “energetic”.

Problem found! Should have checked that first. Assumptions are the mother of all…

 

[Yondering]

So for clarification - were you having "bolt click" when chambering loaded rounds, or only after firing them?

Was it happening on chambering before using the small base die, but not after? Or not with either method until after firing?

 

[NamibHunter]

So for clarification - were you having "bolt click" when chambering loaded rounds, or only after firing them?

Was it happening on chambering before using the small base die, but not after? Or not with either method until after firing?

Bolt click sometimes appeared after firing the ADG brass/rounds, especially when the brass got past 12 reloads. Bolt close was always fine.

During load development with brand new brass, i had occasional bolt click at top of bolt lift, but only with rounds where the powder charge was near or at book max (but before ejector marks or hard bolt lift showed up). Not unexpected. Found max for H4831 (a temp stable powder) and backed off 60 fps. That was where the speed flat spot appeared.

ADG brass loaded at the accuracy node (well below max pressure) worked perfectly fine with the Hornady FL die with 1.5-2 thou should bump, for 10-11 reloads shooting a super consistent Average Speed and a large sample (35-45 shot) SD of 4-6 fps, with zero bolt click issues. Loaded rounds chambered real easy. Extracted was also real easy.

At reload 11 a few clicks were felt (same load as before, chanbered cleaned every time i get back home, carbon ring removed every time, inspected with bore scope).

From reload 12 to 19 every case clicked every time, at the same load as before, with the same barrel conditions as before. Brass was retired after reload 19 if i remember correctly.

Talked to some experienced folks including gunsmith Kenny Porter at Porter Precision and he recommended a small base die. And next time don’t use a match chamber reamer, or a “competition” reamer to cut the chamber (likely chamber is too tight and not compatible with the FL die). Thise reamers are apparently meant for Hornady factory match ammo, not custom hand loads.

Got the small base die back from Kenny within days, and is now using it on every reload, sizes the brass about 1.5 thou down from fired dimension at the 0.200” line, close to the case head. Double what the Hornady die produced.

Sadly, it seems my new batch of powder needs a lower charge for the same speed, so made an adjustment to the load recipe. Discovered that a bit late (assumed the new bottle was the same batch nr as before…). No clicks so far.

Will have to wait for reload 12-14 to know if the bolt clicks come back.

It is likely the tight chamber dimensions that caused it.

 

[NamibHunter]

Much appreciate the help and advice!

 

[ToKeepAndBear]

Time to buy new brass? Toss after 10 firings and carry on.

 

[Haney]

Bolt click sometimes appeared after firing the ADG brass/rounds, especially when the brass got past 12 reloads. Bolt close was always fine.

During load development with brand new brass, i had occasional bolt click at top of bolt lift, but only with rounds where the powder charge was near or at book max (but before ejector marks or hard bolt lift showed up). Not unexpected. Found max for H4831 (a temp stable powder) and backed off 60 fps. That was where the speed flat spot appeared.

ADG brass loaded at the accuracy node (well below max pressure) worked perfectly fine with the Hornady FL die with 1.5-2 thou should bump, for 10-11 reloads shooting a super consistent Average Speed and a large sample (35-45 shot) SD of 4-6 fps, with zero bolt click issues. Loaded rounds chambered real easy. Extracted was also real easy.

At reload 11 a few clicks were felt (same load as before, chanbered cleaned every time i get back home, carbon ring removed every time, inspected with bore scope).

From reload 12 to 19 every case clicked every time, at the same load as before, with the same barrel conditions as before. Brass was retired after reload 19 if i remember correctly.

Talked to some experienced folks including gunsmith Kenny Porter at Porter Precision and he recommended a small base die. And next time don’t use a match chamber reamer, or a “competition” reamer to cut the chamber (likely chamber is too tight and not compatible with the FL die). Thise reamers are apparently meant for Hornady factory match ammo, not custom hand loads.

Got the small base die back from Kenny within days, and is now using it on every reload, sizes the brass about 1.5 thou down from fired dimension at the 0.200” line, close to the case head. Double what the Hornady die produced.

Sadly, it seems my new batch of powder needs a lower charge for the same speed, so made an adjustment to the load recipe. Discovered that a bit late (assumed the new bottle was the same batch nr as before…). No clicks so far.

Will have to wait for reload 12-14 to know if the bolt clicks come back.

It is likely the tight chamber dimensions that caused it.

Good to see Kenny has another happy customer and you have things under control .

 

[Yondering]

Bolt click sometimes appeared after firing the ADG brass/rounds, especially when the brass got past 12 reloads. Bolt close was always fine.

During load development with brand new brass, i had occasional bolt click at top of bolt lift, but only with rounds where the powder charge was near or at book max (but before ejector marks or hard bolt lift showed up). Not unexpected. Found max for H4831 (a temp stable powder) and backed off 60 fps. That was where the speed flat spot appeared.

ADG brass loaded at the accuracy node (well below max pressure) worked perfectly fine with the Hornady FL die with 1.5-2 thou should bump, for 10-11 reloads shooting a super consistent Average Speed and a large sample (35-45 shot) SD of 4-6 fps, with zero bolt click issues. Loaded rounds chambered real easy. Extracted was also real easy.

At reload 11 a few clicks were felt (same load as before, chanbered cleaned every time i get back home, carbon ring removed every time, inspected with bore scope).

From reload 12 to 19 every case clicked every time, at the same load as before, with the same barrel conditions as before. Brass was retired after reload 19 if i remember correctly.

Talked to some experienced folks including gunsmith Kenny Porter at Porter Precision and he recommended a small base die. And next time don’t use a match chamber reamer, or a “competition” reamer to cut the chamber (likely chamber is too tight and not compatible with the FL die). Thise reamers are apparently meant for Hornady factory match ammo, not custom hand loads.

Got the small base die back from Kenny within days, and is now using it on every reload, sizes the brass about 1.5 thou down from fired dimension at the 0.200” line, close to the case head. Double what the Hornady die produced.

Sadly, it seems my new batch of powder needs a lower charge for the same speed, so made an adjustment to the load recipe. Discovered that a bit late (assumed the new bottle was the same batch nr as before…). No clicks so far.

Will have to wait for reload 12-14 to know if the bolt clicks come back.

It is likely the tight chamber dimensions that caused it.

Are you annealing? And if so, are you annealing hot/long enough to fully soften the brass back to its previous state? Maybe the issue is just near the case head, which doesn't get annealed of course, and sharpie marked on some cases would tell you that pretty quick. But it also sounds like maybe the brass isn't getting fully annealed and the shoulders are getting harder over 10-12 firings until you start to have issues from too much brass springback? Just guessing since I don't know your process of course, but that's one possible cause.

Of course after 12-14 firings, it's pretty likely the back half of the case is starting to harden up pretty well and not get sized down enough. I'd want to use some soot or a sharpie to figure out exactly where it's sticking and why. It does sound like it's related to brass work hardening one way or the other though.

 

[Doom]

@NamibHunter:

When you have hard extraction or "clickers" (I hate that term) you are in the 70KSI region with your pressure.

 

[Molon]

: Case head to shoulder measurement grows 0.5-1.0 thou, but hard to measure accurately.

It's not hard to measure using proper tools.

...

 

[Molon]

(Makes you question is .001 actually .0014 or .0006. Not to mention tool accuracy and measurement error).

Use a quality blade micrometer and there won't be any question.

....

 

[Yondering]

@NamibHunter:

When you have hard extraction or "clickers" (I hate that term) you are in the 70KSI region with your pressure.

I'd agree this is true generally speaking. But when he said it only happens after 12-14 firings, I suspect there's more to it than that. The number of firings before it's an issue indicates that brass work hardening probably has something to do with it too.

 

[Haney]

@NamibHunter:

When you have hard extraction or "clickers" (I hate that term) you are in the 70KSI region with your pressure.

Too many variables to claim that as fact .

 

[Haney]

Quoting a man that knows what he is talking about .

View attachment 8128507

Truth

 

[hero's machine]

With 15 firings being the beginning of your clicks, did you ever section a case and see if brass flow is an issue?

If it's not a carbon ring....this is where I would look next.