How does increasing OAL effect load performance?

[slohand42]

I have been reloading off and on for years, both shot she'll and pistols. Currently I am loading 40S&W for major USPSA and have been looking through the different recipes, including Clays.

The question that came up for me is, what effect does increasing the OAL have on the performance of the load?

Thanks.

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Edited May 3, 2016 by slohand42

[DarksideCZ]

In my tanfoglio loading longer than 1.135 causes feeding issues.

[slohand42]

I have a Para 16.40, earlier version, Canadian made. I can load up to 1.200 without feeding issues.

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[slohand42]

I know that lengthening the OAL reduces the internal pressure for fast burning powders like Clays. Does it effect the velocity as well, i.e, does lengthening the OAL increase or reduce muzzle velocity?

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[cnote]

Exactly , yes , and reduce

[darkvibe]

In theory maybe but I chronod some different OAL loads and didn't find any difference in velocity.

[perttime]

Better chrono it to make sure.

[Hi-Power Jack]

what effect does increasing the OAL have on the performance of the load?

OAL can play havoc with feeding - too short, or too long, and the ammo won't feed.

OAL can improve/decrease accuracy.

OAL might change pressure levels - with the wrong powders, it can be dramatic.

[slohand42]

Thanks, everyone. I'm loading clays at 1.200 right now. Without discussing the pros and cons of clays in a 40, a lot of the loads I've seen, especially for my Para P16 show an OAL of 1.180 with a 180 gr. bullet. I figure extending the length to 1.200 reduces pressure even more but am hoping I will still make major PL. I'll find a chrono and check it out. Hope the first chrono I find isn't at a match.

Again, thanks.

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[Sarge]

The thing is, even if velocities don't change, pressure always does.

[rustybayonet]

what effect does increasing the OAL have on the performance of the load?

OAL can play havoc with feeding - too short, or too long, and the ammo won't feed.

:

OAL WILL CHANGE CHAMBER PRESSURES!!!

[Steve RA]

Do a Plunk Test when experimenting with different OALs.

[levellinebrad]

In theory maybe but I chronod some different OAL loads and didn't find any difference in velocity.

This statement is contrary to my results. I just worked up some new loads with xtreme 180gr rnfp. I loaded 20 at 1.200 oal. I shot 10 of them over the chrono and was making a 161pf with 4.2gr E3. I ran the remaining 10 back through the press and seated them to 1.180 oal. It increased my average velocity by 55fps and brought the pf to 170pf.

[L3324temp]

^ I've had similar results every time I've tested.

[Postal Bob]

^ Similar results also with reducing oal from 1.20", to 1.18".

[cnote]

Physics, why we avoid setback like the plague

Some powders do plateau and increases can cause a bad situation also

[rustybayonet]

I just played with this last week. I took a text book load and opened up the oal to see if I could get a better poi. This caused cyclic malfunctions by decreasing chamber pressure. Ejection was fine but side did not run all the way back so it was out of battery on the next round. So I had to kick them back down to the original oal. If your looking for max oal, it will depend on your pistol. You then have to work UP your charge to function. The rounds were plinkers so I brought the oal back down instead of pulling them.

[mjohn]

In theory maybe but I chronod some different OAL loads and didn't find any difference in velocity.

This statement is contrary to my results. I just worked up some new loads with xtreme 180gr rnfp. I loaded 20 at 1.200 oal. I shot 10 of them over the chrono and was making a 161pf with 4.2gr E3. I ran the remaining 10 back through the press and seated them to 1.180 oal. It increased my average velocity by 55fps and brought the pf to 170pf.

Not doubting your results, but it odes not seem logical that 0.02 change in oal will result in an increase of 55 fps which you stated increased the PF by 9. It is not possible to get a increase in PF of 9 (using VV reloading data) when using N320 and loading 180 LTC (which LTC and plated are suppose to be similar in loading data or at least for a starting point) the reloading table states a max increase of 0.6 grains (from starting load to max load) and only yields an 85 fps increase which is a 15 PF.

In my thought process, I can not understand how a 0.02 change in oal influences the velocity so much as compared to the powder load.

[Tino2212]

I know its not .40 but i load my 9 major rounds very long (1.188)to get the chamber pressure down and getting as much powder as possible in them to work my comp so yes increasing the OAL will decrease chamber pressure .

Resulting in less velocitie if the powder charge is the same .

[levellinebrad]

In theory maybe but I chronod some different OAL loads and didn't find any difference in velocity.

This statement is contrary to my results. I just worked up some new loads with xtreme 180gr rnfp. I loaded 20 at 1.200 oal. I shot 10 of them over the chrono and was making a 161pf with 4.2gr E3. I ran the remaining 10 back through the press and seated them to 1.180 oal. It increased my average velocity by 55fps and brought the pf to 170pf.

Not doubting your results, but it odes not seem logical that 0.02 change in oal will result in an increase of 55 fps which you stated increased the PF by 9. It is not possible to get a increase in PF of 9 (using VV reloading data) when using N320 and loading 180 LTC (which LTC and plated are suppose to be similar in loading data or at least for a starting point) the reloading table states a max increase of 0.6 grains (from starting load to max load) and only yields an 85 fps increase which is a 15 PF.

In my thought process, I can not understand how a 0.02 change in oal influences the velocity so much as compared to the powder load.

E3 is a very fast powder. That's the only reason I could think there is such an increase. I'm new to .40 but noticed similar increases in 9mm when changing the oal.

[Jim Watson]

I had to reduce my 9mm Minor OAL by about .035" to go from gun 1 to gun 2.

Velocity went up by 70 fps. There was bound to be a pressure increase blowing the bullets out faster.

I ended up reducing the powder charge by 9% to get back where I was.