Minimum bullet inset

[AMSting]

Is there a rule of thumb on how deep to set the bullet into a case? For example, a 9mm bullet is about 0.5" long, with about 0.25" straight sided before you get to the curvature. How deep should this be inset into the case? Factory rounds seem to be anywhere from a little less than 0.1" up to about 0.2".

Maybe a percentage of the straight side?

Does this apply to all bullet calibers?

[gregintenn]

The reloading manuals list a maximum overal length (OAL). Assuming the bullet doesn't have a crimp groove, this is a good place to start. If a crimp groove is present, and you have a bullet designed for the caliber you are loading, you put the crimp groove at the mouth of the case. Wadcutter bullets go fully inside tha case. So I guess the short answer is "It depends.....".

[Raoul]

Is there a rule of thumb on how deep to set the bullet into a case? For example, a 9mm bullet is about 0.5" long, with about 0.25" straight sided before you get to the curvature. How deep should this be inset into the case? Factory rounds seem to be anywhere from a little less than 0.1" up to about 0.2".

Maybe a percentage of the straight side?

Does this apply to all bullet calibers?

Don't guess. Get a reloading manual or at least look up some loads on the net. It could be dangerous guessing.

[AMSting]

I am using published information. My question started because I measured different OALs from factory ammo. There are even differences in tested OALs between manuals. If there was one "best" OAL, I would think everyone would use it.

I guess what I am asking is whether there is a minimum length that needs to be within the case in order to ensure consistent reloads.

[Rightwinger]

I know what you're looking at AMSting. If you look at Lee's manual then get the Lyman's out, you can see different data for the exact same powder and bullet as far as charges. I tended to average the two looking for the middle ground and work up. I haven't found an OAL data that wasn't the same since that's based on the SAMMI chamber dimensions and the bullet dimensions but I guess there could be differences there for those that load to engage the lands and grooves and those that load just to get in the throat. Have been loading for over three years but not that many calibers to see a bunch of differences.

[Guest Lester Weevils]

When I started loading Hornady XTP JHP 124gr 9mm, the Hornady load data for the bullet was so short I worried that it may be a typo. And of course the Hornady load data didn't list the brand of powder I wanted to use.

The powder company's OAL for XTP JHP 124gr, listed significantly longer OAL than the Hornady recommended length.

I bought a couple of boxes Hornady loaded XTP 124gr 9mm ammo, in order to measure the Hornady built ammo and monkey-see-monkey-do. The Hornady loaded ammo measured exactly the same length as their load data recommended OAL.

XTP has a "pointy stubby" unusual shape, but loaded to the Hornady surprisingly-short length it feeds great.

I copied Hornady's OAL and started with the minimum powder load and worked up. Chrono'd the sample Hornady ammo in comparison to my reloads to match my ammo velocity to the factory stuff. So at the end of the day the reloads were the same size and velocity as the Hornady factory rounds.

Also bought two other brands of ammo for comparison which used that same XTP bullet. They were different OAL and velocity from Hornady. So it was a guessing game but finally decided that Hornady is more likely to know the proper OAL for their bullet than some other ammo company.

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I dunno nothin, but maybe it makes sense to monkey-see-monkey-do copy factory ammo. Find factory ammo that uses the same bullet style and copy the dimensions of the factory ammo and work up the load.

When I started loading Rainier bullets, it was an exception because the Rainier shape looked different than any loaded ammo I had seen. There is maybe really good published data for Rainier nowadays, but back then I couldn't find any suggestions. Not having a loaded sample to copy, just experimented with the length of a couple of dummy loads until it would feed well, and then worked up from the minimum load till the load was strong enough to work the pistol action without stove-piping. Low power plinking loads.

Maybe that is over-thinking the problem, or maybe even getting the wrong answer.

[AMSting]

Maybe I answered my own question above with if there was one "best" OAL, everyone would use it. I started using factory ammo that cycled cleanly. Most reload data was close to that length. Then I found Remington which was a lot shorter.

I wound up picking the longer length since I knew it fed well and was closer to the rest of the reloading data. I am working up from minimum load for several different powders. I could insert the bullet deeper without compressing the powder. I was just wondering if there was some rule of thumb based on caliber, bullet, type, etc. If not, I'll keep going this way as that seems to be the consensus.

Rightwinger, by OAL I meant the tested load, not the SAAMI spec. That is the same across manuals. The test loads length vary quite a bit. I at first thought about loading to either the lands or just chamber, but I got different results when I measured across different pistols. I decided to pick something that fed in all of them and see how the loads work out across pistols. So far, I am within a few grains for each to cycle reliably. I load at the lightest that will cycle everything.

Oh, and Lester, there is less Rainier data available now. I am using their bullets and a load manual from 2005, averaged with other information from other manuals.

[Guest Lester Weevils]

Hi AMSting

I started loading light plinking loads with the Ranier for 9mm and .357 mag about 2001 as best can recall. Never used anything except the 124gr HP 9mm and the 158gr .357.

Got out of the habit using Rainier when it just became unobtanium during the great bullet famine of 2009. Might start using it again now that it is available again.

The .357 was a no-brainer because most all of that caliber uses about the same OAL at least for non-wadcutters.

I guestimated the 9mm OAL by comparing the curve shape of the Ranier HP to the curve shape of a conventional round-nose 124gr FMJ. Adjusted the depth of the Rainier until the 'feeding curve' on the side of the Ranier most closely matched the curve of an ordinary FMJ.

Was a long time ago and maybe got it all wrong, but it turned out to be a pretty long OAL near the max 9mm length.

If that happens to be the one you are loading, I could measure one of mine for ya, as a data point.

[enfield]

Somewhere along the line during the last 30 years I seem to recall a rule-of-thumb that a bullet should be seated at least 1 bullet diameter deep in the case mouth.

OAL definitely can affect max pressure if the bullets are seated too deep, but apparently there is no problem with exceeding recommended OAL, at least with bottle-necked rifle cartridges. I have been loading long-out-of-spec rounds for my M94 Swede for many years. As long as the rounds fit in the magazine and the bullet isn't pushed back into the case (by the rifling) when you chamber a round, you're good to go. My M94 has a long leade due to the looong 156 gr RN military bullets it was designed for. I seat my 140 gr spire point bullets about .020 off of the rifling and they still fit the mag. Whether there's an accuracy difference in doing so, I don't know, but there is supposed to be. The rifle has always shot better than I do.

I'm not a reloading expert, so this is not a recommendation that you exceed published OAL in your case.

[TGO David]

Basic theory: When gun powder ignites and burns, it becomes a pressurized gas. The pressurized gas has similar properties as a pressurized liquid, and is what propels the bullet down the barrel.

Take syringe full of water, remove the needle and cap the end with your finger. Press the plunger down 5mm. Now press it down 10mm. Notice how the pressure increases? Basic physics. The same thing happens the further you seat a bullet into a casing w/o reducing the amount of powder in the charge. If you keep the charge the same # of grains but keep setting the bullet further and further back into the case, sooner or later the pressure upon ignition will be far greater than what the firearm can handle and you will end up blowing it to pieces.

That's why you don't just arbitrarily choose how far to set the bullet into the casing. Always, always, always consult reloading manuals. The stuff we play with as reloaders is more than capable of ruining your day if its done wrong.

[glockster157]

There are many variables in bullets seating depth. In pistols feeding and magazine fit are the most important. I once loaded a bunch of 45acp's with 200 grain lead semi-wadcutters to what looked just like what I had been loading. But this was a different brand and the nose was slightly longer. None would fit in my 1911 mags...oops. For revolvers I have had to seat long bullets, like the Keith 173 grain SWC, over the first driving band in SW's that have recessed cylinders. they shot just fine. In rifles length effects feeding and magazine fit as well as accuracy. If I want the best accuracy I will seat the bullet out just off the rifling even if it will not fit the magazine. I just load them one at a time. Love my single shots. I have loaded varmint/target rounds where the bullet was way out there. This will reduce pressure allowing more powder and higher velocities in some circumstances. On the other hand, I have had bullets want to set back in semi autos and this will increase pressures as stated. Always test and check for bullet set back on any semi auto before shooting too many of any new load.