Do extra power buffer springs increase or decrease cyclic rate?

[Mike9250]

I have an HK416 10.4 FA that I'm thinking about suppressing. Since it is overgassed as is, I was thinking about switching to a VLTOR A5 with the H4 buffer to keep the cyclic rate down. Will a Wolff XP spring help as well? I always thought that a heavier spring would slow the rearward travel of the bolt and decrease the cyclic rate. However, it also seems logical that the heavier spring could speed up the forward travel of the bolt, thus increasing cyclic rate. Anyone know which is correct?

[w3453l]

I could be wrong, but I believe that a heavier spring should have no effect on cyclic rate; assuming that the buffer weight remains unchanged.

Force on Spring = - Force of Spring

I'm sure someone will either confirm or prove other wise.

[t15]

I can't comment directly on your question, but if you are already going to vltor a5, there's no reason not to run with a sprinco green action spring, which is almost universally considered the premium option. I think lots of users run this spring in their a5 with the whole array of buffer weights.

A heavier spring will delay unlock and increase reliability with dirty mags etc.

Personally I buy the bcm 8position a5 tubes and buy buffers and sprincos separately. Have no issues using green, but my heaviest buffer is a h3.

[Benito]

I could be wrong, but I believe that a heavier spring should have no effect on cyclic rate; assuming that the buffer weight remains unchanged.

Force on Spring = - Force of Spring

I'm sure someone will either confirm or prove other wise.

Based on my understanding of physics theory, I would agree, however, I have no empirical data to support that.
It would slow down the rearward velocity, but increase the forward velocity. Net change = zero.

[lysander]

The stiffer the spring the higher the cyclic rate.

The force returning the bolt to the forward position is stronger, so the acceleration is higher.

How fast the bolt slows down on the backward trip is largely unchanged due to the extreme force used to accelerate it.

The piston force is on the order of 1500 to 2000 pounds, so 2 or 3 lb/ins increase in spring rate is not going to change the time taken to get the carrier to the back of the extension by any appreciable amount, but, once the buffer bottoms out in the rear of the extension the velocity is zero, so all forward acceleration comes from the spring. Stiffer spring more force; more force, higher acceleration; higher acceleration, less time....

[MegademiC]

I believe Lysander is correct. With pistols, heavier spring increases speed. The slide goes back and forth in what looks like one motion with a high speed camera, while a weak spring allows the slide to remain relatively still for a period at the rear most position before returning to battery. I'm assuming this carries over to rifles.

[Mike9250]

Thanks for the replies. So it sounds like I shouldn't expect the XP spring to slow it down at all. I'll probably test it with both and see how it does. Am I correct that the only advantage of the XP spring would be to prevent the buffer from slamming into the back of the tube with too much force? If that's the case I might have to live with some increase in cyclic rate in order to reduce some of the recoil.

[Benito]

The stiffer the spring the higher the cyclic rate.

The force returning the bolt to the forward position is stronger, so the acceleration is higher.

How fast the bolt slows down on the backward trip is largely unchanged due to the extreme force used to accelerate it.

The piston force is on the order of 1500 to 2000 pounds, so 2 or 3 lb/ins increase in spring rate is not going to change the time taken to get the carrier to the back of the extension by any appreciable amount, but, once the buffer bottoms out in the rear of the extension the velocity is zero, so all forward acceleration comes from the spring. Stiffer spring more force; more force, higher acceleration; higher acceleration, less time....

Yes, good point. That makes more sense than my previous post.

[BufordTJustice]

Lysander beat me to it. He's correct. You moderate cyclic rate with buffer/reciprocating mass and you increase cyclic rate with increasing spring rate.

EDIT: OP, you may want to look at heavy buffers dot net and their stainless body A5 format buffer. It's expensive, but there's none heavier. That's if you're stl getting battered even with the A5H4.

Also, you might consider the Tubbs AR10 flat wire spring in the A5 receiver extension.