Powder Load vs Recoil Spring Strength

[Alllen Bundy]

I've transitioned from using standard pressure 9mm 115 gr ammo to Sig 124 gr +P ammo rated at 1,198 fps muzzle velocity for my Sig P365 and P365XL.

I've haven't had any malfunctions using the stock 17 lb recoil springs with any of the following standard pressure 9 mm 115 gr cartridges or 124 gr +P cartridges.

Browning Training & Practice - 115 gr FMJ - 1,190 fps

Magtech 9A - 115 gr FMJ - 1,135 fps

Remington Range - 115 gr FMJ - 1,145 fps

Winchester White Box - 115 gr FMJ - 1,190 fps

Speer LE Gold Dot Duty - 115 gr JHP - 1,210 fps

Sig Sauer Elite Performance - 115 gr JHP - 1,185 fps

Winchester Silver Tip - 115 gr JHP - 1,225 fps

=================

Sig Sauer M17 Nato - 124 gr FMJ +P - 1,198 fps

Sig Sauer M17 Nato - 124 gr JHP +P - 1,198 fps

But I'm wondering if it would be advisable to use a stronger recoil spring with the 124 gr +P ammo.

Recoils springs are available in strengths of 12, 14, 15, 16, 17, & 18 lb.

 

[LiveLife]

I've transitioned from using standard pressure 9mm 115 gr ammo to Sig 124 gr +P ammo rated at 1,198 fps muzzle velocity for my Sig P365 and P365XL.

I'm wondering if it would be advisable to use a stronger recoil spring with the 124 gr +P ammo ... Recoils springs are available in strengths of 12, 14, 15, 16, 17, & 18 lb.

NOTE: Recoil springs are consumable and should be replaced when reduced in strength to tame felt recoil and muzzle flip (Unless you are running lighter target loads)

Check your owner's manual to see if the pistol is +P rated. If a pistol is rated for +P ammunition, no need to replace with higher spring rate unless spring is worn. These are what's listed as factory recoil spring rates - https://www.glockstore.com/Tungsten-Competition-Recoil-Spring_3?quantity=1&custcol7=5

Factory Weight Spring is 17 lbs for the following Gen 1, 2, 3 Glocks:​

G17, 20, 21, 20SF, 21SF, 22, 31, 34, 35​

​

Factory Weight Spring is 18 lbs for the following Gen 1, 2, 3 Glocks:​

G19, G23, G32​

So if you want to run +P ammo, I would use factory 17/18 lb spring rate using Glock models as examples. If you want to run regular pressure factory loads, 16/17 lbs (Spring rate after new recoil spring assemblies settle/break in). And if you want to run lighter target loads may need even lighter 13-15 lb spring rate.

I measure spring rate by pushing cleared pistol muzzle into a medicine bottle against a bathroom scale and can get good estimate based on the accuracy of the scale (Higher resolution digital scale is better).

 

[highlander 5]

Most modern pistols should be fine with +P anmo so no need to replace a recoil spring. If you're using a pistol used by a country's modern military they are rated for NATO spec which is considered +P shoot to your hearts content.

 

[Slamfire]

I created some kludge device to measure spring compression and that became a dead end. I am sure with dead weights and an expensive fixture it would become easy. So I simply go by the spring rating on the package.

If a spring is weak, you will experience more misfeeds and if really weak, stove pipes. I have seen shooters with 30 to 40 year old S&W M41's having malfunctions with 22lr. Those guys had never changed the recoil spring and were getting stove pipes. I have a 60 + year old Ruger MK1 that is unreliable with HV ammunition, but is feeding my SV without a problem. I think the old recoil spring and mainspring allow the bolt to travel too fast. And I get these over ride jams with HV ammunition. The case has not risen high enough for the bolt to engage the rim, instead the bolt catches the case in the mid section and drags it forward.

I have installed 22 lb recoil springs in my 1911's, and with full powered loads, the pistols ran fine. The slide was hard to rack. However, when I shot full power loads in a target 1911 with a 13 lb recoil spring (standard is 16lb), I had the same sort of failures to feed that I have with my Ruger MK1. Plus the recoil spring guide got a bit beat up.

You can also call the manufacturer and ask them about the dynamics of the pistol with +P ammunition. If the customer service guy understands the question, they might tell you no problemo, or tell you to go to a slightly stronger spring.

 

[Alllen Bundy]

The Sig P365 series is rated for +P ammunition but NOT +P+.

I have a calibrated force gauge rated for 2% accuracy. Before I measure the recoil spring strength I remove the disconnector and striker to make sure that they won't interfere with the recoil spring strength measurement.


Someone please correct me if my analysis is wrong, but if the recoil spring is not strong enough for the powder load, the slide is NOT going to be sufficiently slowed by the recoil spring. The slide will slam into the slide stop. You will feel more muzzle flip. It will feel snappier. The slide will beat the crap out of the slide stop in the grip module. This would probably also increase the strain on the extractor claw as it is extracting a shell case. The shell cases may not eject where you want them to.

If the recoil spring is too strong for the powder load, the slide may not retract fast enough and may not retract fully and ejection malfunctions may occur. The stripper/pick on the slide may be unable to remove a cartridge from the magazine and would fail to chamber a new cartridge.

 

[GRIZ22]

The recoil spring serves one function. That's to return the slide to battery.

 

[Steve762us]

You may find a heavier recoil spring gives your +P loads a few more f/s.

And, returning the slide to battery--and stripping/chambering the next round--
is only one of the recoil spring's functions. The other is keeping the slide/barrel/
case together long enough, to let most of the pressure escape the muzzle after
bullet exit.