BHKnowledgeBaseSolution
SLIDE VELOCITY SYNCHRONIZATION

What are the benefits of “Slide Velocity Synchronization”?

– Reliability enhanced

– Excessive Recoil is eliminated, better control of firearm, faster follow-up shots

– Accuracy is better

– Increased Shooter Confidence

– Less wear of firearm parts

 

SLIDE VELOCITY SYNCHRONIZATION – DEFINITION:

A combination of springs in a firearm, that, when used for shooting a specific type of ammunition, yields ejection distances of empty shell casings in the 4’-10’ range.
The rearward slide velocity of your semi-auto handgun, influences the distance of ejection of empty shell casings. (Other things influence ejection distance: condition of extractor and ejector and other parts, including cleaning and lubrication. For the purposes of this discussion, we’re assuming a well-maintained firearm where all parts and springs are in good condition.)
When a round is fired, there must be sufficient rearward slide velocity to reliably accomplish complete ejection of the empty bullet casing AND sufficient forward velocity of the slide, when returning to battery, to reliably pick up and chamber the next round in the magazine.
We use a range of 4-10 feet, as a general rule. Spring set-up combinations that yield ejection distances of less than 4 feet, may be generally reliable – BUT – have you ever had a round of ammunition that just didn’t seem to be as strong as the rest in the box? Even the best factory ammunition can have one of these guys in the box! Your spring set-up should leave enough “margin” for that occasional underpowered round.
We generally use 10 feet as a “maximum”. There is no reason for your semi-auto pistol to be sending empty brass flying 15 feet. At 15 feet ejection distance, our testing has shown that slide velocity is excessive – the firearm is taking more punishment during recoil than is necessary – the shooter has less controllable excessive recoil – and the barrel is very likely unlocking from the slide before bullet leaves end of barrel – (which means the barrel is actually moving before the bullet leaves the barrel.) Excessive ejection distance also has another downside…..the increased possibility of insufficient recoil spring strength to strip the next round from the magazine, chamber that round, and return the slide to it’s forward-most position.
So…..when thinking about ejection distance of spent shell casings…..we’re looking for “enough”, but not “too much”.
So, what’s the BEST that I can do?
Optimal is extracting empty shell casings landing 5’ – 8’ from the shooting position. If the minimum is 5’, you’ve got margin in the event of the lesser-powered round in the box, and a maximum of 8’ is margin well inside the maximum should you encounter a particularly spunky round in the box.
Extraction distances of less than 4’ can be considered “Over-Sprung” and a “Red Flag” because you’re dangerously close to short cycling the slide which will cause a malfunction that must be cleared. A lighter recoil spring should be considered.
Extraction distances that get into double-digits (+10’) indicate a slide that is probably “Under-Sprung” and is also a “Red Flag” as damage may result. A stronger recoil spring should be considered. Extration distances of 12’ or + deserve Two Red Flags because in addition to the risk of damage due to excessive slide velocity, your bullets are probably leaving the end of an already moving barrel when they exit.
Why am I just hearing about this concept……Slide Velocity Synchronization?
The primary reason…..without the necessary springs to accomplish Slide Velocity Synchronization…..there’s nothing a shooter can do about it except to buy the brand and type of ammunition that ejects the desired distance in your firearm. A variety of springs are required to adapt your firearm to the wide variety of ammunition available today.
Considering only the 9x19mm caliber for a moment. Today, ammunition bullet weights range from ultra-light less than 90 gr bullet weights, and we’re now seeing the other extreme of bullet weights of 150 gr+. Ammunitions of the standard pressure variety and +P pressure.
(As a point of reference, BHSpringSolutions LLC has done no testing with any ammunitions commonly rated as “+P+” and encourages all shooters to avoid ammunition carrying this kind of barrel pressure rating.)
BHSpringSolutions LLC offers spring kits for the Hi Power, Hi Power Clones and Compacts, 1911, Arcus 98DA and 98DAC, that make Slide Velocity Synchronization possible.

BHSpringSolutions LLC

KNOWLEDGE BASE

SLIDE VELOCITY SYNCHRONIZATION
FULL SIZE HI POWER

BROWNING, FN, FM, FEG, OTHER CLONES IDENTICAL TO THE FN/BROWNING HI POWER

For the purposes of this discussion, the Kareen Mark II/III and Arcus 94 fall into “Clone” but not “identical clone” category. During this discussion, the term “Kareen/Arcus clones” refers to this category of clones that include the Kareen Mark II/III and Arcus 94 Hi Powers.

LEGAL NOTES: THE END USER OF ALL BHSPRINGSOLUTIONS LLC PRODUCTS UNDERSTANDS THAT ANY ALTERATIONS TO A FIREARM THAT DEVIATE FROM OEM PARTS AND SPRINGS MAY VOID THE MANUFACTURERS WARRANTY. THE INFORMATION PROVIDED HEREIN IS SHARED AFTER THOUSANDS OF ROUNDS OF TESTING AND ANALYSIS, BUT MAY NOT BE APPLICABLE TO ALL FIREARMS OF MAKE AND TYPE REFERENCED IN THIS INFORMATION. THIS INFORMATION IS INTENDED FOR EXPERIENCED USERS OF THIS FIREARM MAKE AND MODEL AND CONSUMER IS RESPONSIBLE FOR OBTAINING ADDITIONAL KNOWLEDGE NECESSARY TO FULLY UNDERSTAND THE CONTENT OF THIS INFORMATION. THE END USER OF THIS PRODUCT SHOULD CONSULT WITH A QUALIFIED GUNSMITH BEFORE ALTERING ANY FIREARM.

The Hi Power
The Single Action (SA) Hi Power has a simpler recoil cycling design, compared to semi-auto pistols of a Double Action/Single Action (DA/SA) design. When cycling rearward, the slide encounters the resistance of the Main Spring as the slide re-cocks the hammer, and of course the slide also encounters the resistance of the Recoil Spring. Both springs do two jobs – both play a role in controlling rearward slide velocity (recoil). Although the two springs work together to control rearward slide velocity, after the slide moves fully rearward the Main Spring’s job is momentarily finished and the recoil spring finishes it’s job when it propels the slide into it’s forward most position (battery). The Main Spring finishes it’s job when the trigger is pulled, causing the Hammer to hit the Firing Pin with sufficient force that the Firing Pin overcomes the resistance of the Firing Pin Spring. We refer to this design as “simpler” because it can be easier to accomplish “Slide Velocity Synchronization” in the Hi Power, than in a DA/SA CZ 75 (as an example), where the trigger is “pulled” slightly rearward when the hammer is cocked by the slide, which also makes the resistance of the Trigger Return Spring part of the equation of controlling rearward slide velocity. The SA Hi Power relies on only two springs to control rearward slide velocity which also means the Recoil Spring in a SA semi-auto will usually need to be stronger than the recoil spring in a DA/SA semi-auto. The heavier recoil spring translates into more authoritative forward slide velocity that strips and chambers the next round from the magazine.

BHSS RECOIL SPRINGS
17 lb Recoil Spring – The OEM Browning Hi Power Recoil Spring works well with any BHSS Hi Power Main Spring. Works well with most all standard pressure ammunition. Note: When combined the BHSS 26 lb Main Spring, the 17 lb Recoil Spring may be a bit “light” for some ammunitions. In the Kareen/Arcus Clones this spring is used for +P ammunition.

17 lb Progressive Recoil Spring – Comparable performance to the 17 lb Recoil Spring but makes the slide easier to rack.

18 lb Progressive Recoil Spring – A little better control of recoil than either 17 lb Recoil Spring, easier to rack than 18.5 lb Recoil Spring. In many Hi-Powers, may represent a single spring solution for all Standard Pressure and +P shooting.

18.5 lb Recoil Spring – Primarily used with +P rated ammunition. Sometimes used with standard pressure ammunition when using 26 lb Main Spring. Important note – when used with a 32 or 30 lb Main Spring, this Recoil Spring can cause “short cycling” (malfunctions) if shooting Standard Pressure ammunition.

15 lb Recoil Spring – This is OEM in the Kareen/Arcus Clones! In the Browning Hi Power and identical clones, the 15 lb Recoil Spring is primarily used for lower powered ammunition and light reloads that don’t cycle well with the 17 lb Recoil Spring. If using the 32 lb Main Spring, some factory 115 gr FMJ ammunition may cycle best with the 15 lb Recoil Spring.

MAIN (HAMMER) SPRING
32 lb Main Spring – This is the OEM Main Spring for today’s current production Hi Powers. Most gunsmiths who customize Hi Powers agree that this spring is “overkill”. It is sufficient to also be used in the Browning/FN .40S&W Hi Power. It creates a lot of hammer pressure on the sear that contributes to a heavy and even difficult trigger “break”. When a Hi Power is retrofitted with an SFS kit, the Main Spring supplied with the SFS kit measures 30 lb. The SFS kit was developed by an FN engineer – further possible validity that a 32 lb Main Spring is a lot of spring for the application. Can be used to slow rearward slide velocity.

30 lb Main Spring – This is the OEM in the Kareen/Arcus Clones and SFS equipped Browning/FN Hi Powers. Preferred by many gunsmiths in all Hi Powers. Sufficient for use with the BHSS Heavy Firing Pin Spring.

26 lb Main Spring – This is the OEM Main Spring in the Arcus 98DA and 98DAC Hi Power Inspired Handguns. It also works well in the Hi Power. When used, this Main Spring significantly reduces hammer pressure on the sear. Lightens trigger pull. BEST PRACTICES RECOMMENDATION: Sufficient for use with the BHSS Heavy Firing Pin Spring – HOWEVER – if used with the BHSS Heavy Firing Pin Spring, user should commit to changing the Main Spring every 24 months or 2,000 rounds. If used with the Light Firing Pin Spring, user should commit to changing this spring every 48 months or 4,000 rounds. It may be necessary to “up” the resistance of your Recoil Spring when going down to this 26 lb Main Spring.

24 lb Main Spring – Really a specialty spring. In Type 1 Sear Lever Models, use should be confined to Hi-Powers intended for range / target / sporting uses only. In Type II Sear Lever Models where the Light Firing Pin Spring is appropriate, may be applied to broader uses.
Used to lighten the Double Action Trigger Pull in the Arcus 98 DA/DAC.
Expect to need to increase the strength of the Recoil Spring when changing to this spring.
Can play a role in accomplishing the easiest slide rack for the user.
Follow same spring change schedule as with the 26 lb Main Spring.

FIRING PIN SPRING – The Hi Power’s Firing Pin Spring does not impact slide velocity. Unlike Browning striker fired semi-autos where the Firing Pin Spring propels the firing pin forward, the Hi Power’s Firing Pin Spring retains the Firing Pin in it’s rearward position. In Hi Power models without a Firing Pin Block Safety, the Firing Pin Spring is the “Drop Safety” and is the only protection against an unintended discharge that is possible if a Hi Power is dropped on the muzzle with a round in the chamber.

Heavy Firing Pin Spring – Current production Hi Power OEM. Recommended for use in all Hi Powers and Hi Power Clones, including the Kareen/Arcus Clones that do not have a Firing Pin Block Safety (Drop Safety) employing the use of a Sear Lever Spring.

Light Firing Pin Spring – OEM in the Kareen/Arcus Clones and Arcus 98DA and 98DAC Hi Power Inspired Handguns. NOTE: BHSpringSolutions recommends all Kareen and Arcus Hi Power owners replace the Firing Pin Spring with the BHSpringSolutions HEAVY Firing Pin Spring. Often used by users of the 26 lb Main Spring. Sufficient for all Browning/FN Hi Powers and FM 95 Hi Powers equipped with a Firing Pin Block Safety. And although this Firing Pin Spring was OEM in the Kareen/Arcus Clones, that do not include a Firing Pin Block Safety, BHSpringSolutions LLC does not recommend the use of this spring in Hi Powers that do not have a Firing Pin Block Safety.